Gfra3 blocking peptide

In contrast to the hereditary form of medullary thyroid carcinoma (MTC), little is known about the etiology of sporadic MTC, Somatic gain-of-function mutations in the RET proto-oncogene, encoding a receptor tyrosine kinase, are found in an average of 40% of sporadic MTC, We analysed 31 sporadic MTC for somatic and germline variants in GFRA1, GFRA2 and GFRA3 which encode the co-receptors of RET, Although there were no somatic mutations in any of the three genes, a sequence variant (-193C>G) in the 5'-UTR of GFRA1 was found in 15% of cases. Three patients were heterozygous (het); another three patients homozygous (hom) for the G variant. The G allele was not observed in 31 race-matched normal controls. Hence, the relative frequency of this variant in sporadic MTC cases and controls differed significantly (P<0.05). Since this variant lies in the 5' UTR, likely at the transcriptional start site, we analysed for differential expression of GFR-1 at the transcript and protein levels. At the mRNA level, GFRA1 was over-expressed in tumors harboring the rare variant (P=0.06), The presence of the G polymorphic allele seemed to be associated with increased expression by immunostaining for GFR alpha -1. Interestingly, cytoplasmic staining was stronger in intensity for het patients and nuclear staining predominant in hom cases. In conclusion, mutation analysis of GFRA1, GFRA2 and GFRA3 revealed over-representation of a rare variant in GFRA1 (- 193C > G) in the germline of sporadic MTC cases. Our data suggest that the mechanism is related to over-expression of GFR alpha -1 and differential subcellular compartmentalization but the precise mechanism as to how it acts as a low penetrance susceptibility allele for the development of sporadic MTC remains to be elucidated.

Background: A large number of epigenetic alterations has been found to be implicated in the etiology of gastric cancer. We have studied the DNA methylation status of 27 500 gene promoter regions in 24 gastric adenocarcinomas from a Norwegian cohort, and aimed at identifying the hypermethylated regions. We have compared our findings to the gene expression in the same tissue, and linked our results to prognosis and survival. Methods: Biopsies from gastric adenocarcinomas and adjacent normal gastric mucosa were obtained from 24 patients following surgical resection of the tumor. Genome-wide DNA methylation profiling of the tumor and matched non-cancerous mucosa was performed. The results were compared to whole transcriptome cDNA microarray analysis of the same material. Results: Most of the gene promoter regions in both types of tissue showed a low degree of methylation, however there was a small, but significant hypermethylation of the tumors. Hierarchical clustering showed separate grouping of the tumor and normal tissue. Hypermethylation of the promoter region of the GFRA3 gene showed a strong correlation to post-operative survival and several of the clinicopathological parameters, however no difference was found between the two main histological types of gastric cancer. There was only a modest correlation between the DNA methylation status and gene expression. Conclusions: The different DNA methylation clusters of the tumors and normal tissue indicate that aberrant DNA methylation is a distinct feature of gastric cancer, although there is little difference in the overall, and low, methylation levels between the two tissue types. The GFRA3 promoter region showed marked hypermethylation in almost all tumors, and its correlation with survival and other clinicopathological parameters may have important prognostic significance.