Detection of c-kit exons 11- and 17-activating mutations in testicular seminomas by high-resolution melting amplicon analysis

A subgroup of testicular seminomas has been reported to contain activating mutations in KIT, the transmembrane tyrosine kinase receptor encoded by the c-kit gene. Most mutations are in exon 17, although exon 11-activating mutations have recently been described. For patients refractory to standard therapeutic protocols for seminoma, the presence of c-kit-activating mutations in some of these neoplasms might suggest an alternative therapy with KIT targeting drugs. We used the novel mutation scanning technique, high-resolution melting amplicon analysis, to screen a series of 22 testicular seminomas for c-kit-activating mutations. Four cases (18%) had exon 17-activating mutations and these included D816Y, D816V, Y823N and one case that contained both D816E and D820H. A single case (5%) had an exon 11-activating mutation. Interestingly, the exon 11-activating mutation was L576P, the same mutation that characterizes the rare c-kit mutation-positive cases of malignant melanoma. Fluorescence in situ hybridization (FISH) for c-kit suggested that most seminomas are probably polysomic for c-kit and there was not a significant difference in c-kit FISH characteristics between the mutation-positive and mutation-negative cases. The use of high-resolution melting amplicon analysis as a screening technique will allow for the rapid identification of patients with testicular seminomas whose tumors contain c-kit-activating mutations. This could benefit patients whose tumors are refractory to standard therapeutic protocols.