Combining DNA Damage Induction with BCL-2 Inhibition to Enhance Merkel Cell Carcinoma Cytotoxicity
Wei Liu1, Nathan A Krump1, Meenhard Herlyn2
1Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Abstract:
Merkel cell carcinoma (MCC) is a highly lethal skin cancer. MCC tumors rapidly develop resistance to the chemotherapies tested to date. While PD-1/PD-L1 immune checkpoint blockade has demonstrated success in MCC treatment, a significant portion of MCC patients are nonresponsive. Therefore, the pressing need for effective MCC chemotherapies remains. We screened a library of natural products and discovered that one compound, glaucarubin, potently reduced the viability of Merkel cell polyomavirus (MCPyV)-positive MCCs, while remaining nontoxic to primary human fibroblasts and MCPyV-negative MCC cell lines tested. Protein array and Western blot analyses revealed that glaucarubin induces DNA damage and PARP-1 cleavage that correlates with the loss of viability in MCC cells. However, high basal expression of the antiapoptotic factor BCL-2 allowed a subpopulation of cells to survive glaucarubin treatment. Previous studies have shown that, while targeting BCL-2 family proteins significantly decreases MCC cell viability, BCL-2 antisense therapy alone was insufficient to inhibit tumor growth in patients with advanced MCC. We discovered that treatment with an FDA-approved BCL-2 inhibitor in the context of glaucarubin-induced DNA damage led to near complete killing in multiple MCPyV-positive MCC cell lines that express high levels of BCL-2. The combination of DNA damage-induced apoptosis and BCL-2 inhibition thus represents a novel therapeutic strategy for MCPyV-positive MCCs.
Insights
Glaucarubin, a natural compound, effectively kills Merkel cell carcinoma (MCC) cells by inducing DNA damage. Combining it with a BCL-2 inhibitor overcomes resistance, offering a new therapeutic strategy for this lethal skin cancer.
Area of Science:
- Oncology
- Dermatology
- Pharmacology
Background:
- Merkel cell carcinoma (MCC) is an aggressive skin cancer with limited treatment options.
- Existing therapies, including immune checkpoint inhibitors, show limited efficacy in a significant patient subset.
- Developing novel chemotherapies for MCC is crucial due to rapid development of treatment resistance.
Purpose of the Study:
- To identify novel therapeutic agents for Merkel cell carcinoma (MCC).
- To investigate the efficacy of natural products, specifically glaucarubin, against MCC.
- To explore combination therapies to overcome treatment resistance in MCC.
Main Methods:
- Screening of a natural product library to identify compounds effective against MCC.
- In vitro assessment of glaucarubin's cytotoxicity on Merkel cell polyomavirus (MCPyV)-positive and -negative MCC cell lines and fibroblasts.
- Analysis of glaucarubin's mechanism of action, including DNA damage induction and PARP-1 cleavage.
- Evaluation of combination therapy using glaucarubin and a BCL-2 inhibitor in MCC cell lines.
Main Results:
- Glaucarubin demonstrated potent cytotoxicity against MCPyV-positive MCC cells, sparing normal cells.
- Glaucarubin treatment induced DNA damage and PARP-1 cleavage, leading to MCC cell death.
- High BCL-2 expression conferred resistance to glaucarubin in a subset of MCC cells.
- Combination therapy with glaucarubin and a BCL-2 inhibitor resulted in near-complete killing of resistant MCC cells.
Conclusions:
- Glaucarubin is a promising natural compound for MCC treatment, inducing DNA damage and apoptosis.
- BCL-2 inhibition combined with glaucarubin-induced DNA damage offers a novel and effective therapeutic strategy for MCPyV-positive MCC.
- This combination approach may overcome resistance mechanisms and improve outcomes for patients with advanced MCC.
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