Sensitivity to the non-COX inhibiting celecoxib derivative, OSU03012, is p21(WAF1/CIP1) dependent

OSU03012 is a non-COX inhibiting celecoxib derivative with growth inhibiting and apoptotic activity in many cancer cell lines. To investigate mechanisms related to cell cycle proteins in growth inhibition and apoptosis induced by OSU03012, the primary human oral epithelial cell line, TE1177, was transformed with HPV16 E6 (TE/E6), HPV16 E7 (TE/E7) or empty vector (TE/V). TE/E6 cell lines exhibiting low levels of p53 and undetectable levels of p21(WAF1/CIP1) were sensitized to the growth inhibiting and apoptotic effects of OSU03012. The TE/E7 cell lines expressing low levels of Rb and elevated levels of p53 and p21(WAF1/CIP1) were resistant. OSU03012 reduced the number of cells in the S phase of the TE/E7 and TE/V cell lines with intact p53-p21(WAF1/CIP1) checkpoint, but not in the checkpoint defective TE/E6 cell lines. Treatment with OSU03012 also markedly reduced the levels of cyclin A and Cdk2 in TE/E7 and TE/V, but not in TE/E6 cell lines, which had significantly enhanced basal levels of cyclin A and Cdk2. Consistent with the TE/E6 cell line, p21(WAF1/CIP1)-/- mouse embryo fibroblasts were more sensitive to OSU03012-induced apoptosis as evidenced by PARP and caspase 3 cleavages. These data suggest that p21(WAF1/CIP1) is an important factor in the sensitivity of cells to the growth inhibiting and apoptotic effects of OSU03012.