Tagged: Drug Resistence

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

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.
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 [578].”

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.

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Trending with Impact: RNA Modification Regulatory Proteins in Melanoma

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.
Malignant melanoma under the microscope.

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.

Listen to an audio version of this article

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 [5859]. 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 AtlasThe Human Protein AtlasOncomine, 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

Oncotarget is a unique platform designed to house scientific studies in a journal format that is available for anyone to read—without a paywall making access more difficult. This means information that has the potential to benefit our societies from the inside out can be shared with friends, neighbors, colleagues, and other researchers, far and wide.

For media inquiries, please contact media@impactjournals.com.