Induction of the expression of differentiation-related antigens on human colon carcinoma cells by stimulating protein kinase C.

This study was undertaken to determine whether the phorbol diester, phorbol 12-myristate 13-acetate (PMA), causes differentiation of the human colon carcinoma cell line, SW 48. Under routine growth conditions, the cells are round, have a high nuclear-to-cytoplasmic ratio, and lack cytoplasmic vacuoles. After treatment for 1 hour with 100 nmol/L of PMA at 37 degrees C, the cells assumed a spread-out, flasklike shape, displayed a low nuclear-to-cytoplasmic ratio, and exhibited cytoplasmic vacuoles. An inert but lipophilic phorbol diester, 4 phorbol 12,13-didecanoate, failed to induce these morphological changes. Cell kinetic studies showed that whereas SW 48 cells have a doubling time of 35 hours, those incubated with 100 nmol/L of PMA have a doubling time of 90 hours. Although the flow cytometry histograms were similar until 8 hours into the cell cycle, the PMA-treated cells ultimately spent proportionately less time in S and more in G2/M. Finally, under routine growth conditions, SW 48 cells express neither carcinoembryonic antigen nor G7 antigen. These antigens, which are present on the surface of well-differentiated cells, were expressed after treatment of SW 48 with PMA. The data suggest that PMA causes profound changes in structure, cell growth kinetics, and antigen expression, consistent with induction of differentiation of the cell line SW 48.