Modification of Ha-ras oncogene p21 expression and cell cycle progression in the human colonic cancer cell line HT-29.
Multiparameter flow cytometric measurements of the Ha-ras oncogene product, Ha-p21, versus DNA content were used to study the effect of prednisolone, sodium butyrate, and hyperosmolality on the expression of this gene during the cell cycle of HT-29, a human colonic carcinoma cell line. In control cells the expression of Ha-p21 was cell cycle dependent; it increased during G1 and remained approximately constant as cells traversed the S- and G2 + M phases. Two compartments of G1 cells, one expressing low (G1A) and the other (G1B) high levels of Ha-p21 could be identified. Cells grown with prednisolone (1.4-2.1 microM) expressed higher Ha-p21 levels than controls. Cell cycle analysis revealed that this effect was accompanied by a change in the distribution of cells in G1 phase: whereas the proportion of cells in G1A was reduced, that of cells in G1B was increased. The steroid had no detectable effect on cells in S and G2 + M. By contrast, sodium butyrate and hyperosmolality caused a marked decrease in Ha-p21 content. This reduction was not accompanied by any modification of the proportion of cells in the cell cycle compartments. These results would suggest that Ha-p21 is not likely to be a primary regulator of cell cycle progression in HT-29 cells.
D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D002453:Cell Cycle; D002460:Cell Line; D003110:Colonic Neoplasms / Q000473:pathology / Q000503:physiopathology*; D004273:DNA, Neoplasm / Q000032:analysis; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D009857:Oncogenes; D009994:Osmolar Concentration; D011239:Prednisolone / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*
D002087:Butyrates; D004273:DNA, Neoplasm; D011518:Proto-Oncogene Proteins; D020148:Butyric Acid; D011239:Prednisolone; D019204:GTP-Binding Proteins