Synthetic lethality between RB-loss and E2F3 inhibition in small cell cancers targeted by pyrimidine synthesis...

Area of Science:

• Oncology
• Molecular Biology
• Cancer Genetics

Background:

• Small cell carcinoma is an aggressive cancer with neuroendocrine (NE) features, including small cell lung cancer and small cell NE prostate cancer (SCPC).
• RB inactivation is a nearly universal event in small cell cancers, presenting a potential therapeutic vulnerability.
• Understanding dependencies in RB-deficient cancers is crucial for developing novel treatment strategies.

Purpose of the Study:

• To identify genetic dependencies in small cell prostate cancer (SCPC) models using genome-wide CRISPR screening.
• To investigate the role of identified dependencies in RB-deficient cancers across different tissues.
• To explore E2F3 as a potential therapeutic target in small cell carcinomas.

Main Methods:

• Genome-wide CRISPR dependency screen in SCPC models derived from human prostate cell transformation.
• Analysis of E2F3 dependency in RB-deficient cancer cells from prostate, lung, and adnexa.
• Inhibition of E2F3 and de novo pyrimidine synthesis to assess effects on cell proliferation and tumor growth.

Main Results:

• A genome-wide CRISPR screen identified a dependency on the transcription factor E2F3 in SCPC models.
• E2F3 is required in RB-deficient cancer cells across multiple origins (prostate, lung, adnexa).
• E2F3 inhibition suppressed cell cycle progression, proliferation, and in vivo tumor growth in RB-deficient cells.
• Inhibition of de novo pyrimidine synthesis reduced E2F3 expression and small cell carcinoma proliferation.

Conclusions:

• E2F3 is a critical dependency in RB-deficient small cell carcinomas.
• Targeting E2F3 represents a potential synthetic lethality strategy for treating small cell cancers.
• This approach could offer a novel therapeutic avenue by exploiting a common molecular feature of these lethal malignancies.