Relation of cell cycle position and chromatin decondensation to ectopic hormone synthesis in HeLa cells.

Ectopic synthesis of human chorionic gonadotropin (hCG) in HeLa cells, mediated by sodium butyrate, is shown to be associated with cell cycle position in late G1 or early S phase where decondensation of chromatin is maximal. Inhibitors or conditions of culture that block HeLa cells in earlier stages of G1 do not increase hormone production. The time course of butyrate-mediated hCG synthesis shows a direct correlation with the degree of chromatin decondensation in synchronized HeLa cells. Using synchronized cultures, both late G1 and butyrate-treated G2 cells were observed to synthesize large amounts of hormone. However, the chromatin of butyrate-treated G2 HeLa cells resembles late G1 chromatin in its maximal decondensation. These findings suggest that ectopic hormone production in neoplastic cells may be related to decondensation of chromatin irrespective of the position of cells in the cell cycle.