DIFFERENTIAL EXPRESSION OF C-FOS PROTOONCOGENE IN 2 SUBCLONES DERIVED FROM A HUMAN OVARIAN-CANCER CELL-LINE

The expression of the c-fos proto-oncogene was studied in two sublines of the human ovarian cancer cell line SW626. One subline (SW/B) presents the typical 2.0 kb mRNA which is detectable within 15 min. after serum stimulation of quiescent cells, is inducible by protein synthesis inhibitors and has a half-life of approximately 10-15 min. The other subline (SW/A) does not show the 2.0 kb mRNA, but instead presents a mRNA of higher molecular weight capable of hybridizing with the c-fos probe. This bigger mRNA is neither serum inducible nor sensitive to protein synthesis inhibitors. The presence of this transcript is not due to any gross alteration in the gene structure. Differences were found in the DNA binding proteins obtained from nuclei of the two sublines. A protein able to bind the promoter of c-fos was found in SW/B but not in SW/A. In the latter subline no amplification products were observed using two different sets of primers covering the 3' coding region of the human gene. Conversely, the expected fragments were amplified from mRNA obtained from the SW/B subline.