A synthetic lethality-based strategy to treat cancers harboring a genetic deficiency in the chromatin remodeling...

Area of Science:

• Oncology
• Molecular Biology
• Cancer Genetics

Background:

• SWI/SNF chromatin-remodeling genes are frequently mutated in cancers.
• Targeting strategies for SWI/SNF-deficient tumors, particularly those lacking BRG1/SMARCA4, are needed.
• Non-small-cell lung cancer (NSCLC) frequently harbors SWI/SNF mutations.

Purpose of the Study:

• To investigate a synthetic-lethality therapy for cancers deficient in the BRG1/SMARCA4 ATPase subunit.
• To evaluate the therapeutic potential of inhibiting the related BRM/SMARCA2 subunit.
• To identify NSCLC patients with BRG1 deficiency who lack common targetable mutations.

Main Methods:

• Immunohistochemistry to assess BRG1 expression in NSCLC.
• RNA interference (RNAi) to silence BRM in cancer cell lines and tumor xenografts.
• Analysis of tumor growth suppression, senescence induction (p21/CDKN1A), and rescue experiments with BRG1 re-expression.

Main Results:

• 15.5% of NSCLC cases analyzed were deficient in BRG1 and lacked mutations in known therapeutic targets.
• BRM silencing suppressed the growth of BRG1-deficient cancer cells, inducing senescence.
• BRM depletion inhibited the growth of BRG1-deficient tumor xenografts in vivo.
• Growth suppression was reversible by wild-type BRG1, but not ATPase-deficient BRG1.

Conclusions:

• BRM inhibition represents a promising synthetic-lethal strategy for treating BRG1/SMARCA4-deficient cancers.
• This approach is particularly relevant for NSCLCs lacking mutations in EGFR, DDR2, ALK, or FGFR1.
• Development of BRM-ATPase inhibitors could offer a new therapeutic avenue for these difficult-to-treat cancers.