NOX1 and neoplasm: In response to PARP inhibition or depletion, NOX1 and NOX4 were significantly upregulated in vitro and in vivo, and GKT137831, a specific inhibitor of NOX1 and NOX4, effectively attenuated oxidative DNA damage and rescued the perturbed proliferation, when measured by clonogenic assay in vitro and by immunostaining of Ki-67 of tumor xenograft in vivo.