PARP1 expression predicts and determines synergy between PARP1 inhibitors and trabectedin.. Homo sapiens

Trabectedin is a DNA-damaging agent with a peculiar mechanism of action; it traps the DNA repair machinery leading to DNA single- and double-strand breaks, particularly in BRCA1/2-deficient tumors. We hypothesized that trabectedin-induced DNA damage might activate PARP1 (a DNA-repair machinery key player), and consequently, PARP1 inhibition would perpetuate trabectedin-induced DNA damage. In several tumor histotypes, we demonstrated a different degree of synergism between trabectedin and PARP1 inhibitors (PARP1-Is). Independent of BRCA1/2 status, PARP1 expression dictated the degree of synergism. Namely, silenced PARP1 reduced trabectedin-PARP1-Is synergism, whereas overexpressed PARP1 increased combination efficacy. High-PARP1 expression and specific gene signatures associated with DNA damage response and repair (DDR-R) were predictive of trabectedin+PARP1-I synergy. These findings pave the way for the clinical development of this novel combination therapy, as well as evaluation of PARP1 expression and DDR-R signatures in tumor samples as predictive biomarkers of response. Overall design: six bone and soft tissue sarcoma cell lines treated with trabectedin, olaparib and combination