Proliferation of the human colon carcinoma cell line HT29: autocrine growth and deregulated expression of the c-myc oncogene.
Human colon adenocarcinoma cell (line HT29) are able to proliferate in a defined (serum-free) medium containing no added growth factors; in such conditions, their doubling time is 3 to 4 days (on serum-coated dishes) or 2 to 3 days (on an autologous extracellular matrix) compared with 1 day in the presence of fetal calf serum. In the presence of suramin, a polyanion disrupting the binding of growth factors to their receptors, the incorporation of [3H]thymidine in serum-free cultures is reduced (27.0 +/- 2.9% of control after 3 days of culture), suggesting involvement of autocrine growth factors in the autonomous proliferation of the cells. The expression of the proliferation-related oncogene c-myc was examined during various stages of growth and differentiation of the HT29 cells. The cellular contents of c-myc mRNA were similar in all experimental conditions studied: exponential phase; stationary phase; nondifferentiated as well as differentiated cells (by glucose deprivation); and also in serum-free medium containing or not suramin. An approximately 2-fold increase in the level of c-myc mRNA was observed in cells cultured for 3 days in suramin-containing medium and then incubated during 3 h in the absence of suramin (with or without 10% fetal calf serum). Southern blot analysis of the genomic DNA of HT29 cells did not reveal any rearrangement within the region containing the c-myc gene and the flanking sequences (approximately five kilobases upstream and approximately three kilobases downstream). The c-myc locus was weakly amplified (four to six copies per cell). These results indicate that the c-myc gene expression in HT29 cells is deregulated and does not require growth factor stimulation. The deregulation of the c-myc gene may be related to the reduced growth factor requirement of the HT29 cell line.
Forgue-Lafitte
M E
ME
Institut National de la Santé et de la Recherche Médicale, Unité 55, Centre de Recherches Paris-St-Antoine, Paris, France.
Coudray
A M
AM
Bréant
B
B
Mester
J
J
D015152:Blotting, Northern; D015139:Blotting, Southern; D002277:Carcinoma / Q000473:pathology*; D002454:Cell Differentiation; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000473:pathology*; D003470:Culture Media; D015972:Gene Expression Regulation, Neoplastic; D006133:Growth Substances / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc; D011519:Proto-Oncogenes; D013498:Suramin / Q000494:pharmacology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D003470:Culture Media; D006133:Growth Substances; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D013498:Suramin