Staurosporine increases carcinoembryonic antigen expression in a human colon cancer cell line

Staurosporine (ST), a protein kinase C inhibitor, was found to produce anti tumor effects against C22.20, a clonal subline derived from colon cancer HT -29 line, selected for low expression of carcinoembryonic antigen (CEA). Ho wever, as assessed by FAGS analysis using propidium iodide, no apoptosis or cell cycle alteration was found on day 3 after treatment of C22.20 cells w ith ST (1-100nM), Exposure of cells to graded concentrations of the drug (i .e,, from 1 to 25nM) resulted in a concentration-dependent increase in the percentage of CEA positive cells, as determined by flow cytometric analysis . However, when higher concentrations (i.e, 50nM - 100nM) of ST were used, the percentage of CEA positive cells declined compared to that detected in 25nM-treated tumor. Since these results were obtained in a clonal cell popu lation, it is reasonable to hypothesize that induction rather than selectio n mechanism is involved in this phenomenon. The potential clinical interest of the present findings stems from the consideration that treatment with S T or its derivatives could improve sensitivity and efficacy of diagnostic a nd/or immunotherapeutic approaches based on CEA molecules.