Although exposure to gliotoxin slightly prevented the proliferation of CaOV3/PTX_R and SKOV3/PTX_R cells (Figure 1B), treating drug-resistant ovarian cancer cells with gliotoxin failed to induce cleaved caspase-9 (active p37) and caspase-3 (active p19/17) or the downstream target cleaved poly (ADP-ribose) polymerase (PARP) (Figure 1C). This evidence concerns the gene CASP9 and ovarian cancer.