Somatostatin receptor expression profile as a potential criterion for discrimination between seminoma and non-seminoma testicular tumors.

The expression of five (sst1-sst5) somatostatin (SRIF) receptor mRNAs was compared between normal and tumoral testicular samples diagnosed as either seminoma or non-seminoma. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis indicated that all testicular tissues studied (total of 24) contained sst5 receptor transcripts, whereas the sst2 was absent in all of them. In contrast to the normal tissue samples, both types of tumors (total of 12) did not contain sst4 transcripts. sst3 mRNA was expressed in normal and non-seminoma samples, but not in seminomas. sst1 transcripts were not found in normal and seminoma tissues. However, all studied non-seminomas contained this mRNA. Our data thus points to a specific pattern of SRIF receptor mRNA expression in each type of the samples analyzed. Moreover, they further indicate that the presence of sst1 and sst3 transcripts might be used as an additional criterion to distinguish between seminoma and nonseminoma tumors.

Evidence for a selective loss of somatostatin receptor subtype expression in male germ cell tumors of seminoma type.

Somatostatin (SRIF) is a potent antiproliferative signal for both normal and tumoral mammalian cells and an alteration in the SRIF receptor expression pattern has been associated with carcinogenesis. In the present study, the relevance of SRIF signaling to human male germ cell tumors was assessed at the receptor level. The expression of five SRIF receptor (sst1-sst5) mRNAs was estimated by RT-PCR and compared between normal and tumoral testes. All 12 normal testicular tissues studied contained sst3 and sst5 receptor transcripts whereas sst4 was present in almost all (11 of 12). sst1 transcripts were consistently absent while the majority (11/12) of normal samples studied did not contain sst2 mRNA. Parallel assessment of SRIF receptor mRNAs in 10 seminoma testicular germ cell tumors showed expression of a single receptor type, sst5, in all samples analyzed. All seminoma samples were depleted in transcripts corresponding to sst1 and sst2 receptors while either sst3 or sst4 mRNAs were absent in almost all (9 of 10) tumoral samples studied. The comparison of SRIF receptor expression between normal tissue and seminoma tumors thus points to a selective loss of sst3 and sst4 mRNA expression in seminomas. Altogether these data indicate that: (i) normal human testes are putative SRIF targets; (ii) loss of sst3 and sst4 SRIF receptor expression might be associated with seminoma carcinogenesis.