Combined CDKN1A/TP53 mutation in bladder cancer is a therapeutic target

Area of Science:

• Oncology
• Cancer Biology
• Molecular Therapeutics

Background:

• Invasive bladder cancer, particularly metastatic, has poor outcomes with limited therapeutic advancements.
• Chemotherapy combined with Chk1 inhibition is explored in cancers with TP53 mutations, but not yet in bladder cancer.
• CDKN1A (p21) mutations occur in 14% of invasive bladder cancers, often co-occurring with TP53 mutations.

Purpose of the Study:

• To investigate the therapeutic potential of combining gemcitabine with a Chk1 inhibitor in bladder cancer, specifically in cases with combined TP53 and CDKN1A mutations.
• To determine if combined TP53-CDKN1A loss confers sensitivity to this combination treatment.

Main Methods:

• Utilized TP53-CDKN1A double-mutant bladder cancer cell lines (647V, RT-112) and compared them with TP53 or p21-deficient lines.
• Assessed p-Chk1 levels, G2-M arrest, DNA damage, and apoptosis in response to gemcitabine and Chk1 inhibitors (PF477736, AZD7762).
• Conducted xenograft studies using RT-112 cells to evaluate in vivo tumor growth inhibition.

Main Results:

• TP53-CDKN1A double-mutant cell lines exhibited increased p-Chk1 levels and G2-M arrest upon gemcitabine treatment.
• These double-mutant cells showed heightened sensitivity to the combination of gemcitabine and Chk1 inhibitors compared to other cell lines.
• Restoring CDKN1A in p21-deficient cells reduced sensitivity to the combination treatment by mitigating DNA damage and apoptosis.
• Gemcitabine-PF477736 combination therapy demonstrated a significant synergistic effect on tumor growth in RT-112 xenografts.

Conclusions:

• TP53/CDKN1A double-mutant bladder cancer cells display a unique dependency on Chk1 activity for cell-cycle checkpoint control following chemotherapy-induced DNA damage.
• Combination therapy involving gemcitabine and Chk1 inhibitors represents a promising therapeutic strategy for bladder cancers harboring these specific mutations.