Data from Cisplatin Resistance Associated with PARP Hyperactivation

<div>Abstract<p>Non–small cell lung carcinoma patients are frequently treated with cisplatin (CDDP), most often yielding temporary clinical responses. Here, we show that PARP1 is highly expressed and constitutively hyperactivated in a majority of human CDDP-resistant cancer cells of distinct histologic origin. Cells manifesting elevated intracellular levels of poly(ADP-ribosyl)ated proteins (PAR<sup>high</sup>) responded to pharmacologic PARP inhibitors as well as to PARP1-targeting siRNAs by initiating a DNA damage response that translated into cell death following the activation of the intrinsic pathway of apoptosis. Moreover, PARP1-overexpressing tumor cells and xenografts displayed elevated levels of PAR, which predicted the response to PARP inhibitors <i>in vitro</i> and <i>in vivo</i> more accurately than PARP1 expression itself. Thus, a majority of CDDP-resistant cancer cells appear to develop a dependency to PARP1, becoming susceptible to PARP inhibitor–induced apoptosis. <i>Cancer Res; 73(7); 2271–80. ©2013 AACR</i>.</p></div>