A Novel Mutant from Apoptosis‐resistant Colon Cancer HT‐29 Cells Showing Hyper‐apoptotic Response to Hypoxia, Low Glucose and Cisplatin

Solid tumors usually have regions of hypoxia and glucose deprivation. Human colon carcinoma HT‐29 cells show an apoptosis‐resistant phenotype in response to microenvironmental stresses. In this study, we isolated a novel mutant of HT‐29, designated as HA511, that showed a high apoptotic response to hypoxia, glucose deprivation and treatment with the chemical stressors tunicamycin and glucosamine. The mutant HA511 cells exhibited nuclear condensation and fragmentation and activation of CPP32 (caspase‐3) protease under the stress conditions, while the parental HT‐29 cells did not. We found that apoptosis occurred in HA511 cells after prolonged cell cycle arrest at the G1 phase, while in the parental cells a progression to S phase occurred after the G1 arrest. Upon exposure to an anti‐Fas antibody, HA511 cells underwent apoptosis, whereas the parental cells proliferated without substantial cell death. Furthermore, HA511 cells were preferentially hypersensitive to cisplatin. We found no alteration in expression of GRP78, anti‐apoptotic protein Bcl‐X(L), or p53, of which the gene was mutated in HT‐29 cells. The mutant HA511 cells could provide useful information on the mechanism of apoptosis of solid tumors.