Tagged: Drug Resistence

Synergistic Effects of Drug Combinations Targeting AML Cells

April 11, 2024

In this new study, researchers investigated a promising new approach to acute myeloid leukemia (AML) therapy by combining multiple drugs to enhance cytotoxic effects on AML cells.

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Acute myeloid leukemia (AML) is a cancer characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. ABT199, also known as venetoclax, is a targeted therapy that inhibits the BCL-2 protein, which is often overexpressed in AML cells and contributes to their survival. By blocking this protein, venetoclax can trigger apoptosis, or programmed cell death, in cancer cells. Thiotepa, a DNA alkylating agent, has been used in conditioning regimens for hematopoietic stem cell transplantation (HSCT) but its combination with ABT199/venetoclax has not been thoroughly explored, until now.

In a new study, researchers Benigno C. Valdez, Bin Yuan, David Murray, Jeremy L. Ramdial, Uday Popat, Yago Nieto, and Borje S. Andersson from The University of Texas MD Anderson Cancer Center and the University of Alberta investigated a promising new approach to AML therapy by combining multiple drugs to enhance cytotoxic effects on AML cells. On March 14, 2024, their new research paper was published in Oncotarget’s Volume 15, entitled, “ABT199/venetoclax synergism with thiotepa enhances the cytotoxicity of fludarabine, cladribine and busulfan in AML cells.”

“The results may provide relevant information for the design of clinical trials using these drugs to circumvent recognized drug-resistance mechanisms when used as part of pre-transplant conditioning regimens for AML patients undergoing allogenic HSCT.”

The Study

In this study, the researchers demonstrated a notable synergistic effect between ABT199/venetoclax and thiotepa, significantly amplifying cytotoxicity against AML cells. This effect was further magnified when these drugs were combined with fludarabine, cladribine, and busulfan, well-established chemotherapeutic agents renowned for their efficacy in AML treatment.

One pivotal discovery of the research lies in elucidating the molecular mechanism behind this heightened cytotoxicity. The combined drug regimen led to increased cleavage of Caspase 3, PARP1, and HSP90, recognized markers of apoptosis, indicative of a robust activation of the cell death pathway. Additionally, heightened Annexin V positivity, an indicator of early apoptosis stages, was observed, suggesting the effective initiation of cell death in AML cells.

The investigation also shed light on an augmented DNA damage response, evidenced by elevated levels of γ-H2AX, P-CHK1 (S317), P-CHK2 (S19), and P-SMC1 (S957). These markers imply that the drug combination not only induces apoptosis but also contributes to the accumulation of DNA damage in AML cells, further fostering their demise.

Another significant outcome was the activation of stress signaling pathways, reflected in increased levels of P-SAPK/JNK (T183/Y185) and decreased P-PI3Kp85 (Y458). These alterations indicate cellular stress induced by drug treatment, potentially heightening sensitivity to the cytotoxic effects of the combination therapy.

Furthermore, the study addressed the pressing issue of drug resistance, commonly encountered in AML treatment. The five-drug combination notably decreased the levels of BCL-2, BCL-xL, and MCL-1, proteins associated with resistance to venetoclax, suggesting potential efficacy in overcoming resistance and improving treatment outcomes for AML patients. Various AML cell lines, including those with P53-negative and FLT3-ITD-positive mutations associated with poor prognosis, were subjected to the drug combination.

Results & Conclusion

The results exhibited promising activity of the combination therapy against these challenging cell lines. Moreover, extending the findings to clinical relevance, the drug combination was tested on leukemia patient-derived cell samples, revealing enhanced activation of apoptosis, which hints at potential effectiveness in a clinical setting and provides a basis for future clinical trials.

The implications of this research are profound, offering a novel strategy for conditioning regimens in AML patients undergoing HSCT. Combining ABT199/venetoclax and thiotepa with fludarabine, cladribine, and busulfan presents a promising approach for eradicating AML cells and preparing patients for stem cell transplantation. In conclusion, the study signifies a significant advancement in combating AML. The synergistic effects observed in combining ABT199/venetoclax with thiotepa and other chemotherapeutic agents pave the way for enhancing treatment regimens. This research sets the stage for future clinical trials and the potential development of more effective therapies for AML patients.

“The results provide a rationale for clinical trials using these two- and five-drug combinations as part of a conditioning regimen for AML patients undergoing HSCT.”

Click here to read the full research paper in Oncotarget.

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Oncotarget is an open-access, peer-reviewed journal that has published primarily oncology-focused research papers since 2010. These papers are available to readers (at no cost and free of subscription barriers) in a continuous publishing format at Oncotarget.com.

Oncotarget is indexed and archived by PubMed/Medline, PubMed Central, Scopus, EMBASE, META (Chan Zuckerberg Initiative) (2018-2022), and Dimensions (Digital Science).

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Antitumor Effects of Sacituzumab Govitecan Plus Platinum-Based Chemotherapy

March 14, 2024

In this study, researchers investigated the antitumor effects of Sacituzumab govitecan in combination with platinum-based chemotherapy.

The relentless search for effective cancer therapies has led to numerous breakthroughs in drug discovery and development. Advancements have emerged in recent years through the promising avenue of combination therapy, where two or more drugs are used synergistically to enhance their collective therapeutic effect. This strategy has shown significant potential in overcoming drug resistance, reducing side effects, and improving patient survival rates.

In a new study, researchers Thomas M. Cardillo, Maria B. Zalath, Roberto Arrojo, Robert M. Sharkey, Serengulam V. Govindan, Chien-Hsing Chang, and David M. Goldenberg from Gilead Sciences and the Center for Molecular Medicine and Immunology demonstrated the significant antitumor effects of Sacituzumab govitecan, an anti-Trop-2-SN-38 antibody-drug conjugate, in combination with platinum-based chemotherapy. On February 22, 2024, their research paper was published in Oncotarget, entitled, “Sacituzumab govitecan plus platinum-based chemotherapy mediates significant antitumor effects in triple-negative breast, urinary bladder, and small-cell lung carcinomas.”

Sacituzumab Govitecan & Platinum-Based Chemotherapy

Sacituzumab govitecan is an innovative drug that has gained prominence in recent years due to its unique mechanism of action and remarkable antitumor effects. It is an antibody-drug conjugate composed of an anti-Trop-2-directed antibody linked with the topoisomerase I inhibitory drug, SN-38, via a proprietary hydrolysable linker. Trop-2 is a transmembrane glycoprotein that is highly expressed in various solid tumors, making it an attractive target for cancer therapy. SN-38, the active metabolite of the chemotherapy drug irinotecan, is a potent topoisomerase I inhibitor that triggers DNA damage and apoptosis in cancer cells.

Platinum-based chemotherapy, primarily cisplatin and carboplatin, is a cornerstone of cancer treatment. These drugs work by interfering with DNA replication in cancer cells, leading to cell death. However, their use is often limited by drug resistance and toxic side effects.

“Using multiple drugs to treat cancer may allow for direct activity against multiple targets simultaneously or may indirectly affect the same target through different mechanisms of action [16].”

The Study

The combination of Sacituzumab govitecan and platinum-based chemotherapy has the potential to overcome these limitations. In the current study, the researchers found this combination to produce significant antitumor effects in various cancer models, including triple-negative breast, urinary bladder, and small-cell lung carcinomas. They found that the combination treatment resulted in additive growth inhibitory effects in vitro. The combination led to significant down-regulation of anti-apoptotic proteins and up-regulation of pro-apoptotic proteins, suggesting a shift towards pro-apoptotic signaling.

The in vivo efficacy of the combination therapy was further confirmed in mice bearing human tumor xenografts. The combination of Sacituzumab govitecan and carboplatin or cisplatin resulted in significant tumor regressions in all tested models. Importantly, the combination therapy was well tolerated by the animals, indicating a favorable safety profile.

Conclusions

The findings from this study represent a significant leap forward in the field of chemotherapy combination therapy drug discovery. The team provided strong evidence to support the clinical investigation of Sacituzumab govitecan in combination with platinum-based chemotherapy for the treatment of various solid tumors. Future studies should investigate the optimal dosing and sequencing of this combination therapy to maximize its efficacy and minimize potential toxicities. Additionally, the exploration of potential biomarkers could help identify patients who are most likely to benefit from this combination therapy.

In summary, the combination of Sacituzumab govitecan (SG) and platinum-based chemotherapy holds great promise as a potent antitumor therapy. It represents a novel approach that could potentially revolutionize the treatment of various solid tumors and improve patient outcomes.

“Importantly, these data demonstrate significantly greater antitumor effects of SG plus carboplatin or cisplatin in tumor-bearing mice than monotherapies, and that they were well tolerated by the animals. Based on these results, SG plus platinum-based chemotherapeutics merit clinical investigation.”

Click here to read the full research paper in Oncotarget.

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Genetic Alterations in Thyroid Cancer: Resistance to BRAFi and Anaplastic Transformation

February 8, 2024

In this new research perspective, researchers discuss the role of genetic alterations in resistance to BRAF inhibition and anaplastic transformation in thyroid cancer.

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Thyroid cancer is a complex disease with various subtypes and clinical presentations. While some cases can be successfully treated with standard therapy, others present challenges due to resistance to treatment and the development of aggressive forms of the disease. In a new research perspective, researchers Mark Lee and Luc GT Morris from New York Presbyterian Hospital and Memorial Sloan Kettering Cancer Center discuss the recent research that has shed light on the role of genetic alterations in mediating both resistance to BRAF inhibition and anaplastic transformation in thyroid cancer. On January 24, 2024, their paper was published in Oncotarget, entitled, “Genetic alterations in thyroid cancer mediating both resistance to BRAF inhibition and anaplastic transformation.”

“An improved understanding of the molecular basis of thyroid cancer has led to the development of new targeted agents.”

Understanding Thyroid Cancer and its Molecular Landscape

Thyroid cancer is generally characterized by well-differentiated histology and a relatively indolent course. However, a subset of patients presents with more advanced disease or dedifferentiated histologies that are less responsive to standard therapy. These dedifferentiated subtypes include anaplastic thyroid cancers (ATC) and poorly differentiated thyroid cancers (PDTC), which are thought to arise from a process of microevolution from papillary thyroid cancers (PTC).

The mitogen-activated protein kinase (MAPK) pathway plays a crucial role in regulating cell proliferation and differentiation. Mutations in this pathway, particularly in the BRAF gene (specifically the V600E mutation), have been identified in a significant proportion of thyroid cancers. The BRAF V600E mutation leads to constitutive activation of the MAPK pathway, resulting in dedifferentiation and tumor progression.

BRAF Inhibition as a Therapeutic Approach

Given the role of the BRAF V600E mutation in thyroid cancer, targeted agents that inhibit BRAF have been explored as potential treatments. Sorafenib and lenvatinib were the first agents approved for use in thyroid cancer but have shown limited overall survival benefits. More recent agents, such as vemurafenib and dabrafenib, specifically target the V600E mutant oncoprotein and have demonstrated promising results in early trials.

However, despite initial responses, the long-term efficacy of BRAF inhibitors is limited due to the emergence of resistance mechanisms. Multiple compensatory pathways and mutations have been observed in thyroid carcinoma cells that mediate bypass of BRAF blockade, leading to disease progression. These mechanisms can be primary, already present in the tumor, or secondary, acquired over the course of treatment.

Genetic Alterations Associated with Resistance to BRAF Inhibition

Recent studies have identified specific genetic alterations that are associated with resistance to BRAF inhibitors and anaplastic transformation in thyroid cancer. One such alteration is the presence of mutations in the PI3K/AKT/mTOR pathway, particularly in the PIK3CA gene. These mutations paradoxically hyperactivate the ERK pathway when BRAF is inhibited, leading to decreased response to therapy].

Other genetic alterations associated with resistance include mutations in the MAPK/ERK pathway (such as MET amplifications, NF2, NRAS, and RASA1), the SWI/SNF chromatin remodeling complex (ARID2 and PBRM1), and the JAK/STAT pathway (JAK1). These alterations have been observed in tumors that dedifferentiate after treatment with BRAF inhibitors, suggesting their involvement in both resistance and anaplastic transformation.

Mechanisms of Anaplastic Transformation in Thyroid Cancer

Anaplastic transformation, the transition from well-differentiated to dedifferentiated thyroid cancer, is a rare but aggressive form of the disease. The mechanisms underlying anaplastic transformation are not fully understood but likely involve genetic and molecular changes that drive the loss of cellular differentiation.

Ultrastructural analyses have shown that well-differentiated thyroid carcinomas transforming into anaplastic thyroid cancers undergo changes in cellular architecture, including the loss of tight junctions, desmosomes, and cellular polarity. Molecular alterations associated with anaplastic transformation include aneuploidy, increased copy number alterations, and mutations affecting genes such as p53, bcl-2, cyclin D1, β-catenin, Met, c-myc, Nm23, and Ras.

Overlapping Mechanisms of Resistance and Anaplastic Transformation

Recent research has revealed a significant overlap between the genetic alterations associated with resistance to BRAF inhibitors and the development of anaplastic thyroid cancer. Studies have shown that tumors that dedifferentiate after BRAF inhibition are enriched in known genetic alterations that mediate resistance to BRAF blockade, including mutations in the PI3K/AKT/mTOR, MAPK/ERK, SWI/SNF chromatin remodeling complex, and JAK/STAT pathways.

These findings suggest that selective pressures exerted by BRAF inhibition can promote the outgrowth of subclones harboring these mutations, ultimately leading to anaplastic transformation. The complex and multifactorial nature of these compensatory mechanisms underscores the need for alternative treatment strategies to address resistance and improve long-term disease control.

Immune Microenvironment in Resistance and Anaplastic Transformation

The immune microenvironment of thyroid tumors has been a topic of active investigation, as it plays a crucial role in both tumor pathogenesis and drug resistance. While BRAF inhibitors are thought to increase anti-tumor immunity, they may also have competing effects, such as driving tumor infiltration by macrophages. Anaplastic thyroid cancer is associated with changes in the immune milieu, including increased infiltration by macrophages and fibroblasts.

The immunosuppressive microenvironment observed in resistance to BRAF inhibitors and anaplastic evolution suggests a potential role for combined targeted therapy with immunotherapy. Preclinical studies have shown that the combination of BRAF inhibitors with immune checkpoint inhibitors can enhance anti-tumor immune activity. Clinical trials evaluating the efficacy of combined BRAF blockade with immunomodulatory therapies are ongoing, with preliminary results showing promising anti-tumor effects.

Current Approaches and Future Directions

The current standard therapeutic approach for locally advanced, recurrent, metastatic, and dedifferentiated thyroid cancers involves surgical resection and adjuvant radioactive iodine therapy. However, in cases where surgery is not feasible or tumors are resistant to standard therapy, targeted agents have emerged as potential treatment options.

For patients with ATCs harboring the BRAF V600E mutation, neoadjuvant combination kinase inhibition with dabrafenib plus trametinib has shown promise . Other targeted agents, such as everolimus (MTOR inhibitor), crizotinib (MET inhibitor), and PI3K inhibitors, have demonstrated antitumor activity in preclinical and early clinical studies.

Combined BRAF blockade with immunotherapy is also being investigated as a potential treatment strategy. Early clinical trials have shown promising outcomes, with significant partial response rates and stable disease rates in advanced thyroid cancers. However, further studies with long-term follow-up are needed to evaluate the real-world effectiveness of these novel immunotherapies in combination with targeted therapy.

Conclusion

Genetic alterations play a crucial role in mediating both resistance to BRAF inhibition and anaplastic transformation in thyroid cancer. Understanding the mechanisms underlying these processes is essential for developing effective treatment strategies. Targeted therapies, such as BRAF inhibitors, have shown initial promise but are limited by the emergence of compensatory mechanisms.

The identification of specific genetic alterations associated with resistance and anaplastic transformation provides insights into potential therapeutic targets. Combined targeted therapy with immunomodulatory agents is being explored as a means to enhance anti-tumor immune activity and overcome resistance. Ongoing clinical trials will further elucidate the effectiveness of these novel treatment approaches and pave the way for personalized therapies for patients with thyroid cancer.

In conclusion, the study of genetic alterations in thyroid cancer has provided valuable insights into the development of resistance to targeted therapies and the progression to more aggressive forms of the disease. By understanding the underlying mechanisms and identifying potential therapeutic targets, researchers can work towards improved treatment strategies and better outcomes for patients with thyroid cancer.

“Dual-target therapies have been trialed but with continued limitations to long-term disease control. Thyroid tumor dedifferentiation and BRAF inhibitor resistance are also found to be associated with a transition to an immunosuppressed state. Early studies on combined targeted and immune-modulated therapy have demonstrated promising outcomes. Further clinical studies are needed to test real-world effectiveness of these novel immunotherapies with targeted therapy.”

Click here to read the full research perspective in Oncotarget.

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Triple Combination Treatment Overcomes Colorectal Cancer Resistance

December 14, 2023

In a new study, researchers aimed to elucidate the role of cancer stemness in the resistance of colorectal cancer cells to targeted therapies.

Triple Combination Treatment Overcomes Colorectal Cancer Resistance

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Colorectal cancer is the third most diagnosed cancer and the second leading cause of cancer-related deaths worldwide. It often starts in the colon or rectum with small, noncancerous clumps of cells called polyps, which can develop into cancer over time. Risk factors for colorectal cancer include age, family history, inflammatory bowel diseases, diet, smoking, and physical activity.

The development and progression of colorectal cancer are driven by the aberrant activation of multiple signaling pathways, such as EGFR (epidermal growth factor receptor), RAS-RAF, and PTEN-PI3K. Among these pathways, the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR pathways are particularly important, as they are frequently mutated in colorectal cancer. Therapeutic targeting of these pathways has shown promise in suppressing tumor growth. However, cancer cells often develop resistance to targeted therapies, leading to treatment failure and disease progression.

In a new study, researchers Astha Lamichhane, Gary D. Luker, Seema Agarwal, and Hossein Tavana from The University of Akron, University of Michigan and Georgetown University aimed to elucidate the role of cancer stemness in the resistance of colorectal cancer cells to targeted therapies. Their research paper was published in Oncotarget on October 4, 2023, entitled, “Inhibiting BRAF/EGFR/MEK suppresses cancer stemness and drug resistance of primary colorectal cancer cells.”

The Study

One of the major mechanisms of drug resistance in cancer is the gain of stemness in cancer cells under drug pressure. Cancer stem cells (CSCs) are a small subpopulation of cells within a tumor with the ability to self-renew and differentiate into various cell types that constitute the tumor. CSCs are thought to be responsible for tumor initiation, progression, and resistance to therapy. Therefore, identifying approaches to target CSCs is crucial for improving treatment outcomes in colorectal cancer patients.

In the current study, the researchers developed spheroid cultures of patient-derived BRAFmut and KRASmut tumor cells and studied the resistance mechanisms to inhibition of the MAPK pathway. The researchers found that treatment with MAPK pathway inhibitors enriched the expression of CSC markers CD166, ALDH1A3, CD133, and LGR5 and activated the PI3K/Akt pathway in cancer cells. These findings suggest that the development of drug resistance in colorectal cancer is associated with the acquisition of a stem cell-like phenotype.

To overcome drug resistance mediated by cancer stemness, the researchers examined various combination treatments to block these activities. They found that a triple combination treatment targeting BRAF, EGFR, and MEK significantly reduced stemness and the activities of oncogenic signaling pathways in colorectal cancer cells. This triple combination treatment has shown promise in clinical trials, with response rates of 21% and 32% in patients with BRAFmut colorectal cancer. The researchers demonstrated that this combination treatment effectively suppressed the growth, stemness, and activities of several oncogenic signaling pathways in cancer cells.

“Our finding supports the hypothesis that CSCs confer drug resistance and suppressing stemness is a viable approach in BRAFmut colorectal cancer.”

Conclusion

Altogether, the researchers found that inhibiting BRAF, EGFR, and MEK in combination shows promise in suppressing cancer stemness and overcoming drug resistance in colorectal cancer cells. This approach targets the underlying mechanisms of resistance, providing a potential strategy for improving treatment outcomes in patients with colorectal cancer. Further research and clinical trials are needed to validate the efficacy and safety of this triple combination therapy.

“In conclusion, this study presented a model of cyclic drug treatment and recovery of patient-derived tumor spheroids and established that single-agent MEK inhibition of colorectal cancer cells lead to adaptive resistance of cancer cells through gain of stemness. A triple combination treatment used in a clinical trial of colorectal cancer patients effectively blocked growth, stemness, and activities of several oncogenic signaling pathways in cancer cells. Our approach to identify mechanisms of drug resistance of patient-derived cancer cells to targeted therapies and develop effective treatments is promising toward cancer precision medicine.”

Click here to read the full research paper in Oncotarget.

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The Evolution of Metastatic Cancer: Mechanisms and Drivers

April 14, 2023

In a new editorial, researchers explore genomic evolution in metastatic cancer, how therapy can drive it and the implications for developing new treatments.

The Evolution of Metastatic Cancer: Mechanisms and Drivers

The Trending With Impact series highlights Oncotarget publications attracting higher visibility among readers around the world online, in the news and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Oncotarget.com.

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There are several theories that attempt to explain the genesis of cancer. One prominent theory is the genetic theory—proposing that cancer may arise from the accumulation of genetic mutations that alter the normal functioning of cells. These mutations can drive the formation of tumors, which can then spread to other parts of the body in a process known as metastasis. Metastatic cancer is often difficult to treat because it has evolved to become resistant to standard therapies.

“It is generally accepted that development of cancer is a slow process, likely spanning decades during which the developing neoplastic cells sequentially acquire genomic alterations that will eventually give rise to the primary tumor [1].”

In a new editorial, researchers Ditte S. Christensen and Nicolai J. Birkbak from Aarhus University discuss mechanisms of genomic evolution in metastatic cancer, how therapy can drive it and the implications for developing new treatments. Their editorial paper was published in Oncotarget on March 21, 2023, entitled, “Therapy drives genomic evolution in metastatic cancer.”

Therapy Can Drive Metastatic Cancer

Cancer cells are master adaptors and have a remarkable ability to evolve, especially in response to therapy. When cancer cells are exposed to chemotherapy, radiation or targeted therapies, they can develop resistance to these treatments by acquiring new genetic mutations. This can occur through a variety of mechanisms, including mutations in the genes that regulate cell division and DNA repair, as well as the acquisition of new genes that confer resistance to specific drugs.

In this editorial, the authors discuss how this process of genomic evolution can lead to the development of metastatic cancer. As cancer cells acquire new mutations that allow them to survive and grow in the presence of therapy, they may also acquire mutations that allow them to invade and colonize new tissues. This can lead to the development of new tumors in distant parts of the body, which are often more difficult to treat than the original tumor.

“How the ability to perform these multiple independent steps is acquired by cancer cells remains a mystery.”

Mechanisms of Metastatic Cancer

Understanding the mechanisms by which cancer cells evolve in response to therapy is essential for developing new treatments for metastatic cancer. The clonal bottleneck hypothesis and the gatekeeper mutation hypothesis are two different hypotheses that attempt to explain how cancer cells acquire the ability to metastasize and spread to distant parts of the body. The clonal bottleneck hypothesis proposes that metastatic cancer is the result of a single subclone of cancer cells from the primary tumor that successfully seeds new sites. According to this hypothesis, the cancer cells undergo a clonal bottleneck event where only a small number of cells from the primary tumor are able to survive and successfully colonize new tissues. This hypothesis suggests that the ability to metastasize is an inherent property of the subclone that successfully colonizes new sites.

On the other hand, the gatekeeper mutation hypothesis proposes that metastatic cancer is the result of a specific genetic mutation or mutations that act as gatekeepers, allowing cancer cells to metastasize and spread to new sites. According to this hypothesis, the ability to metastasize is acquired through the acquisition of one or more specific genetic mutations that allow cancer cells to bypass the normal checks and balances that prevent uncontrolled growth and invasion of surrounding tissues.

Exploring Gatekeeper Genomic Events

In a 2022 study, the authors of this editorial and their team explored the concept of gatekeeper genomic events by comparing primary and metastatic tumors on a large scale. Their large-scale analysis of more than 40,000 individual tumors from the AACR Genomics Evidence Neoplasia Information Exchange (GENIE) project found an increase in mutation burden and chromosomal instability in metastatic tumors, but no evidence of individual mutations driving the metastatic process itself. The concept of gatekeeper mutations remains a hypothesis, and further research is needed to explore this idea in more detail.

This study and others suggest that metastatic cancer dissemination involves a bottleneck event where a highly fit clone from a primary tumor successfully seeds distant sites. Strong selective pressure from anti-cancer therapy drives the acquisition of private driver mutations associated with therapy resistance in individual metastatic tumors. There is limited evidence for the existence of specific gatekeeper mutations. It is also possible that the primary driver of metastatic cancer is found outside the cancer cells.

“Indeed, it may be that a primary driver of metastatic cancer is to be found outside the cancer cells themselves, potentially through inflammation in the tumor-immune microenvironment or through interaction with a declining host immune system which may enable immune escape and sudden systemic dissemination by a highly proliferative primary tumor clone.”

Conclusions

In conclusion, the genetic theory of cancer proposes that cancer arises from genetic mutations that alter the normal functioning of cells, leading to the formation of tumors and metastasis. This editorial by Christensen and Birkbak highlights the process of genomic evolution in metastatic cancer and its implications for cancer treatment. Understanding the mechanisms by which cancer cells evolve in response to therapy is crucial for developing new treatments for metastatic cancer. Recent studies have shed light on the clonal origin of metastatic tumors and the role of selective pressure from anti-cancer therapy in the acquisition of private driver mutations associated with therapy resistance. While the concept of gatekeeper mutations remains a hypothesis, it is clear that the acquisition of aggressive cancer traits is the primary driver of metastatic potential. Further research is needed to explore this idea in more detail and develop effective therapies for metastatic cancer.

“It will be exciting to further explore these questions as more data becomes available on metastatic cancers, particularly with paired primary and metastatic tumor samples with sequential biopsies to facilitate the analysis of dynamic tumor evolution over time, rather than through static snapshots provided by samples obtained at a single time point.”

Click here to read the full editorial published in Oncotarget.

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Oncotarget is an open-access, peer-reviewed journal that has published primarily oncology-focused research papers since 2010. These papers are available to readers (at no cost and free of subscription barriers) in a continuous publishing format at Oncotarget.com. Oncotarget is indexed/archived on MEDLINE / PMC / PubMed.

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New Target Fights Ferroptosis- and Radio-Resistance in Lung Cancers

November 2, 2022

Researchers published a research perspective about a recent study that uncovered FSP1 as a novel target gene that mediates ferroptosis resistance and radioresistance in lung cancer cells.

Figure 1: KEAP1-NRF2 axis and its molecular effectors in the regulation of ferroptosis. — **Figure 1:** KEAP1-NRF2 axis and its molecular effectors in the regulation of ferroptosis.

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Ferroptosis is a type of cell death caused by the accumulation of iron and lipid peroxides in cells. Cancer cells are often resistant to ferroptosis, which allows them to survive and proliferate. Radioresistance is another common feature of cancer cells that allows them to resist the effects of radiation therapy.

A new research paper (published on April 22, 2022) identified ferroptosis suppressor protein 1 (FSP1) as a novel KEAP1/NRF2 target gene and demonstrated that FSP1 plays an essential role in NRF2-mediated ferroptosis resistance and radioresistance in KEAP1-deficient lung cancer cells.

Recently, researchers Nsengiyumva Emmanuel, Hongen Li, Jing Chen, and Yilei Zhang from Xi’an Jiaotong University, Ruyang People’s Hospital and Shaanxi Jiuzhou Biomedical Science and Technology Group wrote a paper about the implications of these findings. On October 19, 2022, their research perspective was published in Oncotarget’s Volume 13, entitled, “FSP1, a novel KEAP1/NRF2 target gene regulating ferroptosis and radioresistance in lung cancers.”

“In a recent study by Pranavi Koppula et al. from The University of Texas MD Anderson Cancer Center, FSP1 was demonstrated as a novel target of NRF2 and to play a vital role in KEAP1/NRF2-mediated ferroptosis regulation [13], which reveals the important role of genetic regulation of FSP1 in cancer development.”

The KEAP1-NRF2 regulatory pathway is crucial for protecting cells against oxidative damage. In lung cancer cells, KEAP1 mutations lead to NRF2 deregulation and contribute to tumorigenesis. Researchers have been searching for an effective way of targeting this pathway in cancer cells to sensitize them to ferroptosis/radiation-inducing agents. They found that FSP1 is upregulated in KEAP1-mutant lung cancer cells, and its expression is associated with resistance to ferroptosis and radiotherapy. Coenzyme Q10- (CoQ) FSP1 signaling represents a potential target for overcoming resistance to ferroptosis and radiotherapy in KEAP1-mutant lung cancer cells.

“Currently, there are four major ferroptosis-defending systems, while NRF2 could directly control two of them, SLC7A11/GSH/GPX4 axis and CoQ/FSP1 axis.”

This study provides new insights into the role of target genes in the KEAP1-NRF2 pathway and how they contribute to cancer cells’ resistance to ferroptosis and radiotherapy. However, the mechanism by which KEAP1-NRF2 target genes mediate resistance to ferroptosis is not yet fully understood. Fortunately, the identification of FSP1 as a key target gene involved in this process opens up new therapeutic avenues for the treatment of lung cancer.

“Here, Pranavi Koppula and her colleagues’ study indicates that pharmacological targeting of CoQ-FSP1 signaling to overcome KEAP1 deficiency-induced radioresistance could be a potentially effective therapeutic strategy in treating KEAP1 mutant lung cancers.”

Click here to read the full research perspective published by Oncotarget.

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Epigenetics and Immunotherapy Combined Fights Rare Lymphoma

August 24, 2022

In a new Oncotarget study, researchers assessed an epigenetic and immunotherapy treatment regimen among patients with blastic mantle cell lymphoma (bMCL).

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Mantle cell lymphoma (MCL) is a type of non-Hodgkin’s lymphoma (NHL) that is aggressive, difficult to treat and typically affects older adults. Recurrence and mortality rates among patients with MCL have remained high, despite recent therapeutic advances. Blastic mantle cell lymphoma (bMCL) is a rare subtype of MCL associated with a worse disease trajectory.

“Despite recent advances, MCL is incurable except with allogeneic stem cell transplant. Blastic mantle cell lymphoma (bMCL) is a rarer subtype of cMCL associated with an aggressive clinical course and poor treatment response, frequent relapse and poor outcomes.”

In previous studies, researchers reported that a combination of epigenetic and immunotherapy treatments may have synergistic activity and offer better outcomes in patients with MCL. In the current study, Francis R. LeBlanc, Zainul S. Hasanali, August Stuart, Sara Shimko, Kamal Sharma, Violetta V. Leshchenko, Samir Parekh, Haiqing Fu, Ya Zhang, Melvenia M. Martin, Mark Kester, Todd Fox, Jiangang Liao, Thomas P. Loughran, Juanita Evans, Jeffrey J. Pu, Stephen E. Spurgeon, Mirit I. Aladjem, and Elliot M. Epner from Pennsylvania State University College of Medicine, Penn State Hershey Cancer Institute, Winter Haven Hospital Cassidy Cancer Center, Icahn School of Medicine at Mount Sinai, National Cancer Institute, University of Virginia, UVA Cancer Center, University of Arizona College of Medicine, Oregon Health and Science University, and Beverly Hills Cancer Center used samples from a previous trial to perform correlative studies focused on clinical results in patients with blastic MCL. On August 16, 2022, their research paper was published in Volume 13 of Oncotarget, entitled, “Combined epigenetic and immunotherapy for blastic and classical mantle cell lymphoma.”

Epigenetic and Immunotherapy

Epigenetic therapy includes a range of drugs that can target epigenetic mechanisms, including DNA methylation and posttranslational modifications of histones. For example, vorinostat (SAHA; a histone deacetylase inhibitor) and cladribine (chemotherapy that also inhibits DNA methylation) are epigenetic agents. Rituximab, a maintenance immunotherapeutic agent, is a CD20-directed monoclonal antibody. These three treatments combined encompass a novel potential epigenetic and immunotherapy treatment regimen (SCR) for mantle cell lymphoma (MCL).

“Relapsed and [treatment] naïve MCL patients were treated with vorinostat (SAHA), cladribine and rituximab (SCR) regimen and followed for OS [overall survival], progression free survival (PFS) and with correlative basic science studies to investigate potential mechanisms of action of this epigenetic/immunotherapy combination.”

The Study

Since blastic MCL patients are rare, only 13 bMCL (four relapsed, nine previously untreated) patients treated with the SCR regimen were assessed in the prospective part of this study. All patients were male and Caucasian, and the median age at diagnosis was 62 years old. The patients were treated until they achieved remission, met the criteria for removal from the study, withdrew from the study, or passed away. Four patients were changed from rituximab to ofatumumab (a potent fully-human anti-CD20 antibody) due to rituximab intolerance (allergies, reactions) or lack of efficacy.

“Of 13 bMCL patients, all patients responded to therapy, with 12 patients meeting criteria for remission (CR, n = 6; PR, n = 6). Of those achieving CR, 5 remain in CR more than 5 years after diagnosis.”

Results

After a median of 4.8 cycles of therapy, 12 patients achieved a complete response (CR), and one patient maintained stable disease (SD). The patients reported an increased overall survival greater than 40 months, and several patients maintained durable remissions without relapse for longer than five years. These results are remarkably superior to current treatment regimens with conventional chemotherapy, which range from 14.5-24 months among bMCL patients.

“The median OS of 43.4 months and PFS of 17.3 months for MCL patients with blastic disease treated with SCR therapy is one of the most important outcomes in this study.”

Another important finding was that the G/A870 CCND1 polymorphism was a strong predictor of blastic MCL, nuclear localization of cyclinD1 and response to SCR therapy. The team identified two distinct mechanisms of resistance to SCR therapy. The researchers reported that the loss of CD20 expression and evading treatment by seeking sanctuary in the central nervous system were two major resistance mechanisms to SCR therapy.

“These data indicate that administration of epigenetic agents improves efficacy of anti-CD20 immunotherapies.”

Conclusion

Although the study sample was relatively small, the researchers’ results are promising. The SCR regimen was demonstrated to be an effective epigenetic and immunotherapy treatment for mantle cell lymphoma, with long-term remissions and improved overall survival in bMCL patients. Researchers revealed important insights into the mechanisms of action of SCR and potential resistance mechanisms. This study also highlights the potential for future research exploring the efficacy of SCR in other cancers, along with other predictive biomarkers of response.

“This approach is promising in the treatment of MCL and potentially other previously treatment refractory cancers.”

Click here to read the full research paper published by Oncotarget.

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Oncotarget

Trending With Impact: Low-Dose Chemo Inhibits Resistant Breast Cancer

June 18, 2021

In this trending in vitro study, researchers assessed the efficacy of low-dose 6-mercaptopurine and 5-azacitidine to inhibit high resistance triple-negative breast cancer cells.

Photomicrograph of a breast cancer (grade 3 invasive ductal carcinoma) with frequent mitoses (mitotic figures), including a large central atypical mitoses.

The Trending with Impact series highlights Oncotarget publications attracting higher visibility among readers around the world online, in the news, and on social media—beyond normal readership levels. Look for future science news about the latest trending publications here, and at Oncotarget.com.

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Triple-negative breast cancer (TNBC) accounts for 10-15% of all breast cancers. “Triple-negative” in this subtype of breast cancer cell refers to the lack of HER2 protein and estrogen and progesterone receptors. This means that TNBC cannot be treated with hormone inhibition and must be treated with conventional chemotherapy. In addition, many of these breast cancer cells can opportunistically switch between proliferation and quiescence—a difficult phenotype to treat. Patients diagnosed with this highly adaptable cancer frequently relapse and develop resistance to treatments.

In 2021, researchers from The University of Texas MD Anderson Cancer Center conducted a research study in hopes of developing a safe and effective therapeutic combination to treat resistant triple-negative breast cancer. Their paper, published in Oncotarget’s Volume 12, Issue 7, was entitled: “Inhibition of resistant triple-negative breast cancer cells with low-dose 6-mercaptopurine and 5-azacitidine.”

The Study

“Evidence suggests that SUM149-metabolic adaptable (MA) cells are a suitable model of resistant human triple-negative breast cancer (TNBC) cells that can survive bottlenecks in the body, including therapeutic interventions, by opportunistically switching between quiescence and cell proliferation [5, 7, 8].”

In this in vitro study, researchers cultured three highly drug-resistant and metastatic progenitor-like TNBC cell lines with opportunistic switching between quiescence and proliferation. Researchers focused on designing a safe treatment that is effective in both low- and high-risk patients. The researchers note that it was critical to their study that the regimen is proven safe to administer to patients for early use in the minimal residual disease (MRD) stage after surgery, and before clinical metastasis is detected.

“For a potential therapy to be suitable at the MRD stage, it must be safe (an important criterion prior to clinical relapse) and disrupt heterogeneous progenitor-like cancer cells that evolve into clinical metastases.”

Two chemotherapy and immunosuppressive drugs (ribonucleoside analogues) were tested on the cell lines at low doses for the sake of viability in the MRD stage: 6-mercaptopurine (6-MP) and 5-azacitidine (5-AzaC). Both of these drugs have been clinically proven to be well-tolerated and to have drug-sensitizing, quiescence-stabilizing, and apoptosis-inducing effects in cancer cells.

“We chose 5-AzaC because it could complement 6-MP’s effects on the transcriptome and epigenome, and—as indicated by many Phase 1 clinical trials—5-AzaC is well tolerated [11].”

Results & Conclusion

“Our studies suggest that low-dose 6-MP, which is a purine analogue and very effective in maintaining remission in IBD [9], inhibits highly adaptable TNBC cells in our model, presumably by disrupting their transcriptome and epigenome.”

Researchers found that these low-dose therapeutics take several weeks to become effective. Despite the low dose, 6-MP (complimented by 5-AzaC) was capable of inhibiting highly adaptable TNBC cells. The researchers also point out that, based on decades of 6-MP’s use in patients with inflammatory bowel disease (IBD), this drug may be used regularly to modulate the immune system and prevent disease recurrence through its ability to inhibit chronic inflammation associated with advanced cancers.

“We suggest that low dose 6-MP and other drugs that would complement 6-MP’s action, such as 5-AzaC, could be suitable for preventing recurrence and metastasis in high-risk breast cancers. 6-MP could be taken lifelong if it is necessary for maintaining a long-term remission.”

Click here to read the full scientific study, published by Oncotarget.

Oncotarget

Trending with Impact: RNA Modification Regulatory Proteins in Melanoma

May 20, 2021

Researchers analyzed various publicly available datasets and identified two RNA modification regulatory proteins that are not only overexpressed in melanoma, but necessary for melanoma growth.

Malignant melanoma under the microscope.

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After melanoma of the skin metastasizes, it commonly becomes very difficult for doctors to treat. This is due to melanoma’s problematic tendency to acquire resistance to therapeutic interventions. Despite the development of many new targeted interventions and immunotherapies, five-year survival rates for patients with melanoma continue to be less than 10% for patients with lymph node metastasis and less than 5% for patients with distant metastasis.

“As the number of potential therapeutic DNA targets dwindle, many researchers are turning to RNA to tackle the problem.”

In 2018, researchers from Yale University School of Medicine and the University of Alabama at Birmingham in the United States set their focus on analyzing RNA alterations in melanoma, in hopes of identifying new, and more effective, therapeutic targets. Their research paper was published by Oncotarget in 2019, and entitled: “Dissecting the role of RNA modification regulatory proteins in melanoma.”

“Many studies have shown that these RNA modifications play crucial role in melanoma growth and metastasis [58, 59]. They are also involved in drug resistance mechanism.”

The Study

“Since RNA is a key molecule that drives every cellular process, their deregulation is present in nearly all human disease and play a causative role.”

The researchers explain that alterations among RNAs may arise due to altered activity or expression of the enzymes/proteins which are involved in the modification process. In this study, the team used multiple publicly available bioinformatics platforms to, first, analyze RNA alterations in melanoma samples, and then, to comprehensively analyze RNA modification regulatory proteins among melanoma samples. The publicly available datasets included: The Cancer Genome Atlas, The Human Protein Atlas, Oncomine, and the UALCAN database.

“Our study started with the analysis of various genetic alterations (amplifications, mutations/deletion) as well as RNA overexpression of these RNA modification regulatory proteins in The Cancer Genome Atlas melanoma database.”

Based on their analyses of these databases, reverse transcription quantitative PCR, soft-agar assays, validation by shRNA-mediated knockdown, and statistical analysis, the team identified what they believe are the most relevant RNA modifying proteins that play a crucial role in the development of melanoma. They found that METTL4 and DNMT3A RNA-modifying enzymes/proteins are both necessary for melanoma growth and overexpressed in melanoma.

“Based on this we infer that the upregulated expression of RNA modification regulatory proteins METTL4 and DNMT3A play a key role in melanoma initiation or progression.”

Conclusion

The researchers explained that their studies served the duel purpose of improving their understanding of novel pathways that cause melanoma to become untreatable, and also paving the way “to develop new, effective and sustainable therapeutic tools for optimal drug selection and treatment.”

“Additional future studies are needed to fully determine the role of these RNA modification regulatory proteins in melanoma tumor growth and progression (e.g., metastasis).”

Click here to read the full scientific study, published by Oncotarget

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