Phorbol ester inhibits dna synthesis induced by interleukin-6 in TSH-Pretreated FRTL-5 cells

Combination of TSH and Interleukin-6 (IL-6) can stimulate DNA synthesis in FRTL-5 cells. Phorbol 12-miristate 13-acetate (PMA) stimulates G0 to G1 transition but inhibits G1 to S transition in these cells. We studied the effect of IL-6 on DNA synthesis in TSH-pretreated FRTL-5 cells in the presence or absence of PMA. IL-6 induced DNA synthesis when it was added to TSH-pretreated cells. Further, PMA inhibited the DNA synthesis induced by IL-6. These data might suggest that in FRTL-5 cells IL-6 can show its mitogenic effect in G1 phase of their cell cycle progression.