CHEK1 and mesothelioma: Synergistic increases in cytotoxicity with the use of COX-2 specific inhibitors, Chk1 inhibitors (PF-00477736), and nitric oxide (NO) (O’Kane et al. 2010; Blasina et al. 2011; Nagai et al. 2012) were also reported in previous studies on the enhancement of PMX cytotoxicity in vitro on various mesothelioma (MSTO-211H, NCl-H2052, NCl-H2452) and human lung adenocarcinoma (A549) cell lines.