Abstract 589: NQO1-dependent anticancer action with combination β-lapachone and ionizing radiation in the head and neck cancer.

Abstract

Abstract The number of new cases of oral cavity, pharynx and larynx cancers is estimated be 52,610 in 2012 with an expected 11,500 deaths. Despite progressive improvements in outcome, current treatment approaches still result in an overall survival rate of approximately 50% at five years for locally advanced head and neck cancer (HNC). Additional therapeutic approaches are needed to further enhance outcomes. NAD(P)H:quinone oxidoreductase 1 (NQO1) is a two-electron oxidoreductase that reduces quinones to hydroquinones and has been shown to be overexpressed in a number of solid tumors. For the first time, our studies in 45 HNC cell lines identified NQO1 overexpression in more than 70% of HNC cell lines. Furthermore over-expression of NQO1 has been shown to be a critical determinant for tumor-selective therapy using β-lapachone (β-lap), a substrate of NQO1 that undergoes partial reduction and spontaneous reversion, creating a futile cycle that produces very high levels of reactive oxygen species. HNC cell lines that overexpress NQO1 are significantly killed by treatment with β-lap. The anti-cancer action of β-lap in HNC cells is initiated and processed through five essential downstream mediators: (i) reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2); (ii) DNA single strand breaks (SSBs) induced by ROS; (iii) hyperactivation of poly(ADP-ribose)polymerase-1 (PARP1) and accompanying poly(ADP-ribose)-PARP1 (PAR) formation; (iv) dramatic NAD+/ATP depletion; and (v) programmed necrosis (necroptosis). In combination with ionizing radiation (IR), β-Lap radiosensitized NQO1(+) HNC cells under conditions where nontoxic doses of either agent alone did not achieve threshold levels of DNA lesions and /or SSBs required for PARP-1 hyper-activation. Furthermore, combination therapy with β-lap and IR significantly enhanced γ-H2AX and 53BP1 foci formation and PARP-1 hyper-activation which was associated with ATP loss and induction of programmed cell death. Furthermore, the anticancer effects of combination β-Lap and IR were blocked by the NQO1 inhibitor dicoumarol. Our findings offer a strategy for the clinical utilization of β-lap as a radiosensitizer in HNC. Citation Format: Long Shan Li, Srilakshmi Reddy, Jinming Gao, David A. Boothman, Baran Sumer, John S. Yordy. NQO1-dependent anticancer action with combination β-lapachone and ionizing radiation in the head and neck cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 589. doi:10.1158/1538-7445.AM2013-589