In a phase II study, researchers found that the PARP inhibitor olaparib led to stable disease or tumor regressions in patients with advanced breast, ovarian, pancreatic, and prostate cancers who had germline mutations in BRCA1 or BRCA2.
In addition, it was recently shown that aberrations in DNA repair genes, such as BRCA2 and ATM, are present in both somatic and germline form in a significant minority of prostate cancer; these abnormalities can be targeted by drugs such as platinums and PARP inhibitors.
We identified differential therapeutic vulnerabilities that emerge upon the loss of both PTEN and p53, and observed that combined inhibition of PARP and PI3K provides increased efficacy in hormone-insensitive advanced prostate cancer.
A phase II study of the PARP inhibitor olaparib (AstraZeneca) for cancer patients with inherited BRCA1 and BRCA2 gene mutations confirmed earlier results showing clinical benefit for advanced breast and ovarian cancers, and demonstrated evidence of effectiveness against pancreatic and prostate cancers.
Detailed studies in prostate cancer cells now indicate PTEN does not regulate RAD51 expression or homologous recombination and is not a biomarker for PARP inhibitor sensitivity.
Here, we tested the hypothesis that the PARP inhibitor ABT-888 (veliparib) can enhance the response of prostate cancer cells and tumors to ionizing radiation (IR).
To clarify the basis for cell killing during prostate cancer radiotherapy, we determined the IR-induced expression of several apoptotic- (bax, bcl-2, survivin and PARP) and G1-cell cycle checkpoint- (p53 and p21(WAF1/Cip1)) related proteins, in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145 and PC-3; all epithelial) prostate cells.