Targeting the Vulnerability of RB Tumor Suppressor Loss in Triple-Negative Breast Cancer

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Approximately 30% of triple-negative breast cancers (TNBCs) lack functional retinoblastoma (RB) tumor suppressor.
• Loss of RB function presents a potential therapeutic vulnerability in TNBC.

Purpose of the Study:

• To identify small molecules that are synthetically lethal with RB loss of function in TNBC.
• To explore the therapeutic potential of targeting RB-deficient TNBC.

Main Methods:

• Drug screens were employed to identify candidate RB-synthetic lethal small molecules.
• Isogenic TNBC cell lines and panels with varying RB statuses were used for counter-screening.
• Analysis of TNBC clinical specimens and xenograft models were performed.

Main Results:

• Several RB-synthetic lethal small molecules were identified, including anti-helmenthics, chemotherapeutics, and inhibitors of DNA-damage checkpoints (CHK) and chromosome segregation (PLK1).
• Therapeutic effects were confirmed to be robust and selective for RB-loss-of-function TNBC.
• RB-deficient tumors showed high CHK1 and PLK1 expression and increased drug sensitivity due to impaired DNA replication checkpoints.
• CHK inhibitors demonstrated RB-selective efficacy in xenograft models.

Conclusions:

• Loss of RB function in TNBC leads to specific vulnerabilities that can be exploited therapeutically.
• Targeting DNA-damage checkpoints (CHK1, PLK1) represents a promising precision strategy for RB-deficient TNBC.
• This study supports the development of therapies selectively targeting RB loss in TNBC treatment.