ANALYSIS OF K-RAS GENE-MUTATIONS IN HUMAN PANCREATIC-CANCER CELL-LINES AND IN BILE SAMPLES FROM PATIENTS WITH PANCREATIC AND BILIARY CANCERS

The ras family of oncogenes are the most frequently activated group of dominant transforming genes in both human and experimental cancers. T he ras family of genes encode highly similar proteins with molecular w eights of 21 kDa which are thought to play a key role in signal transd uction. Activation in vivo by point mutations results in the ras p21 p rotein being maintained in the activated form and stimulating cellular proliferation autonomously. Point mutations at codon 12 of K-ras have been observed in >75% of cases of adenocarcinomas of the exocrine pan creas. The type and frequency of K-ras gene mutations in pancreatic ca ncer cell lines and in bile samples from patients with cytologically-p roven biliary tract malignancies and from patients with non-malignant disorders of the biliary tract were determined. Codons 12, 13 and 61 o f the K-ras gene were analysed by using restriction fragment length po lymorphisms created through mismatched primers during polymerase chain reaction (PCR) of genomic DNA. A mutation of codon 12 of K-ras was de tected in 10 of 13 (77%) human pancreatic cancer cell lines. The amino -acid substitutions were glycine to aspartate (5 samples), arginine (2 ), valine (2) and cysteine (1). No mutations were found at codons 13 o r 61. A mutation at codon 12 of K-ras was detected in 9 of 18 (50%) of bile samples analysed. Eleven bile samples had positive cytology for malignancy of pancreaticobiliary origin, and 4 (36%) of these had a co don 12 mutation. Mutations were detected in 5 of the 7 (71%) cytologic ally-negative bile samples, although malignancy was subsequently diagn osed in 2 of these patients on further histology, and was suspected in 3 other cases on clinical and radiological criteria. This method prov ides a rapid determination of K-ras gene mutations in bile samples for patients with pancreatic and biliary tract diseases, which may be use ful when considering future therapy directed at inhibition of activate d ras-induced signal transduction pathways.