Expression of FGFR2 BEK and K-SAM mRNA variants in normal and malignant human breast

The expression of mRNA encoding alternative forms of fibroblast growth factor receptor 2 (FGFR2) differing in the carboxy terminal half of their third immunoglobulin-like domain, was investigated in 77 human breast cancer tissues, 12 non-malignant breast biopsies and 29 cell lines, using a reverse transcriptase (RT) polymerase chain reaction (PCR) method. RNA from the two tissue groups yielded PCR product corresponding to both the BEK and the K-SAM form; amounts normalised to glyceraldehyde phosphate dehydrogenase product were similar in both groups. The level of either variant or of the total FGFR2 product was essentially unrelated to prognosis or clinical status except that patients with advanced clinical T staging had a higher proportion of BEK to K-SAM (P = 0.01). RNA from 1/2 normal breast derived and 8/10 breast cancer cell lines expressed exclusively or predominantly the K-SAM form; 2/10 had significant amounts of both BEK and K-SAM mRNA. Of 12 other epithelial lines, seven expressed mainly K-SAM mRNA, four expressed BEK and one was negative. Of five non-epithelial lines, one was negative, two expressed only BEK mRNA and two had significant amounts of both variants. We conclude that tissue levels of FGFR2 mRNA are unaltered in breast cancer extracts and that the splicing mechanism for this exon selection appears not to be significantly disrupted.