Evaluation of poly (ADP) ribose polymerase (PARP) inhibitor, veliparib (ABT-888), in combination with platinum, etoposide and radiation in small cell lung cancer. Homo sapiens

Veliparib showed limited single agent cytotoxicity but selectively potentiated (≥50% reduction in IC50) cisplatin, carboplatin and etoposide in vitro in 5 of 9 SCLC cell lines. Veliparib with cisplatin, etoposide or with both cisplatin and etoposide showed greater delay in tumor growth than chemotherapy alone in H146 but not H128. The potentiating effect of veliparib was associated with in vitro cell line sensitivity to cisplatin (CC=0.672; p=0.048) and DNA-PKcs protein modulation. Gene expression profiling identified differential expression of a 5-gene panel (GLS, UBEC2, HACL1, MSI2 and LOC100129585) in cell lines with relatively greater sensitivity to platinum and veliparib combination. Veliparib potentiates standard cytotoxic agents against SCLC in a cell specific manner. This potentiation correlates with platinum sensitivity, DNA-PKcs expression and a 5-gene expression profile. Overall design: In vitro cytotoxicity of veliparib, cisplatin, carboplatin, and etoposide singly and combined was determined by MTS in 9 SCLC cell lines (H69, H128, H146, H526, H187, H209, DMS53, DMS153, and DMS114). Subcutaneous xenografts in athymic nu/nu mice of H146 and H128 with relatively high and low platinum sensitivity, respectively, were employed for in vivo testing. Mechanisms of differential sensitivity of SCLC cell lines to PARP inhibition were investigated by comparing protein and gene expression profiles of the platinum sensitive and the less sensitive cell lines.