Abstract
Induction of apoptosis in human cancer cells by Sasa quelpaertensis Nakai has been considered to be a potential therapeutic target for cancer treatment; however, the underlying mechanisms of action are not well understood. The present study investigated the role of nitric oxide (NO•) and inhibitors of apoptosis (IAPs) during apoptosis induced by Sasa quelpaertensis Nakai extracts (SQE) in p53-wild type (WT) and p53-null HCT116 colon carcinoma cells. Trypan blue exclusion and Annexin V/propidium iodide assays were used to test for antiproliferation, and apoptosis and cell cycle. Griess and reverse transcription-polymerase chain reaction and western blotting assays were carried out to assay NO• production, and to detect the mRNA and protein levels of Bcl-2, PARP and IAPs. A colorimetric assay was utilized to measure the time-dependent increase in caspase-3 activity. SQE inhibited cell growth and promoted apoptosis by the elevation of NO• in a dose- and time-dependent manner. In addition, both cell types underwent a reduction in mRNA and protein levels of IAPs (survivin, CIAP-1 and -2, and X-linked inhibitor of apoptosis) as well as anti-apoptotic Bcl-2, whereas an increase in protein expression of poly (ADP-ribose) polymerase 1 and caspase 3 activity was observed; however, an equivalent cytotoxic and apoptotic effect by SQE was observed in p53-WT and p53-null cells. Collectively, the results indicated that SQE-induced apoptosis was independent of p53 status and associated with modulation of endogenous NO• and IAP family gene expression.