CYTOSTATIC EFFECT OF TNF-ALPHA ON CANCER-CELLS IS INDEPENDENT OF P21(WAF1)

Tumor necrosis factor alpha (TNF alpha) is a cytotoxic/cgtostatic comp ound for a variety of human cancer cells. The p21(WAF1) protein is a c yclin-dependent kinase inhibitor (CDKI) that binds to cyclin/cyclin-de pendent kinase (CDK) complexes and inhibits their kinase activities, t hereby leading to cell cycle arrest. We found that the cytostatic effe ct of TNF alpha on the cervical cancer cell line, ME180, was concomita nt with an arrest of these cells in the G0/G1 phase of the cell-cycle. This corresponded with an increase in both p21(WAF1) mRNA and protein levels which likely occurred via a p53-independent pathway since ME18 0 is infected with the human papilloma virus. To elucidate the role of p21(WAF1) in the TNF alpha-mediated growth and cell cycle arrest, we stably transformed ME180 cells with an antisense p21(WAF1)- expression vector. Two clones with reduced levels of p21(WAF1) both in their bas al state as well as after their exposure to TNF alpha were selected. T he growth of these cells was still inhibited by TNF alpha and they arr ested in G0/G1 similar to wildtype or empty vector transfected cells. These results indicate that although p21(WAF1) expression increases dr amatically with TNF alpha treatment, it may not play a critical role i n the cytostatic effect of TNF alpha on ME180 cervical cancer cells.