Primer Mismatch Analysis: a Rapid and Non-Isotopic Method for Analysing Ras Mutations in Human Cancer

Abstract

Numerous studies have shown that activated oncogenes do play a role in the oncogenesis of human neoplasms [1], One of the best illustrated examples is the ras-gene family consisting of three closely related genes: the Harvey-, Kirsten- and N-ras gene. These genes possess four exons and they all encode for the 21 KD protein p21 which has GTP-ase activity and obviously functions as a “second messenger”. Cellular ras-proto-oncogenes can be transformed to activated ras-genes in specific codon areas by point mutations. The point mutations are found at characteristic sites in codon 12, 13 and 61 in all three genes [1,6,8]. These mutated genes then code for the changed p21 proteins having a reduced GTP-ase activity, although the function of the encoded proteins still remains to be determined. Activations in the Harvey ras-gene are fairly rare [2,3], whereas activated Kirsten- and N-ras genes can be observed in a significanly higher number of human tumors [4]. Furthermore, in some pre-malignant diseases, e.g. adenomas in the large intestine and myelodysplastic syndrome, activated Kirsten- and N-ras genes can be proved, too [5,9]. The increased incidence of mutated ras oncogenes in human neoplasias leads to the assumption that these mutations participate in an important step in carcinogenesis. However, up to now the precise function of activated ras-genes in oncogenesis could not be clarified. It is furthermore still controversial whether the detection of an activated ras gene allows diagnostic and prognostic statements.