L- myc allele polymorphism and prognosis for metastases in Russian gastric cancer patients

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During recent years, several attempts have been made to use restriction fragment length polymorphism (RFLP) of protooncogenes, e.g. c-Ha-rus and L-myc, as a marker for prognosis in human cancers [I]. L-myc has L and S alleles, and the presence of two S-S alleles has been reported to be associated with metastases of lung [2] and stomach cancer [3] in Japanese patients, although another study of lung cancer in Caucasians showed no such association [4]. Stomach cancer is common among the Russian population and a good prognostic marker is greatly needed. We performed L-myc RFLP analysis of stomach cancer samples from 21 newly diagnosed patients in Russia. DNA from tumour samples and corresponding mucosa was amplified by polymerase chain reaction, before single strand conformation polymorphism analysis or EcoRI digestion [4]. 9 patients had metastases in regional lymphnodes. All the tumours contained the same L-myc genotypes as the corresponding normal mucosa. Among the 21 patients, the ratio of L-myc genotypes between L-L, L-S and S-S was 0.24:0.62:0.14, which is very close to that found for a healthy white Caucasian population [4]: 0.25:0.62:0.13 (P=O.9865, x2). Among the nine patients with metastases, only 1 patient was found to have the SS genotype, anddistribution ofL-mycalleles was 0.33:0.56:0.11. The distribution of alleles in patients without metastases was 0.17:0.66:0.17, which did not significantly differ from the patients with metastases (P=O.8137, x2). Thus, no excess prevalence of S-S L-myc allele genotype was found in these Russian patients with metastases. If the reported association between the S-S genotype and metastases in Japanese patients could be confirmed in future studies, such an association might be explained by the presence of some specific factor(s) (internal or external) modulating the metastatic process. Among such factors could be ethnic differences in genotypes in the L-myc gene and environmental risk factors. However, because loss of heterozygosity is infrequent in stomach cancer at the L-myc locus [S], the loss of putative metastasis suppressor gene near this locus is improbable. In addition, it appears that the L-myc gene itself is