Expression of apoptosis and cell cycle related genes in proliferating and colcemid arrested cells of divergent lineage

Progression through the cell cycle and redirection of cells towards program med cell death (apoptosis) are tightly inter-related processes. However the requirement for tissue and cell type specificity suggests that a wide vari ety of mechanisms are used to achieve the same purpose. To examine this iss ue, we investigated cell cycle (c-myc, p53, p21/WAF) and apoptosis related (bcl-2, bcb-X-L, bax-alpha) gene expression in two cell lines of very diffe rent origin under proliferating and apoptosis-inducing conditions. Transfor med human osteosarcoma cells (MG63) and non-transformed human kidney embryo nal fibroblasts (293-0) were kept in culture in medium containing 10% FCS a nd growth arrest was induced by the addition of 50 ng/ml colcemid. Colcemid treatment caused growth arrest and elevated expression of cyclin B1 protei n in both cell lines. Apoptosis was significantly elevated in both cell lin es after colcemid exposure for at least one cell cycle. However the pattern of expression of cell cycle and apoptosis related genes, determined by RT- PCR, was quite different between the two cell Lines during exponential,grow th and cell cycle arrest. Colcemid treatment did not markedly influence c-m yc, p53 and p21/WAF expression in MG63 cells but did suppress c-myc and inc rease p21/WAF in 293-0 cells. Furthermore colcemid treated MG63 cells exhib ited elevated bcl-2 and bax-alpha expression while similar treatment of 293 -0 cells resulted in decreased bcl-X-L and slightly increased bax-alpha exp ression. While growth arrest and apoptosis were induced in both MG63 and 29 3 cells following colcemid treatment, the differences in gene expression su ggest that the mechanism by which these cells determine cell fate is quite different and may determine the sensitivity of different cell populations t o anti-neoplastic drug therapy. The distinct patterns of gene expression sh ould be carefully defined before mechanisms of apoptotic cell death are stu died.