Novel retroviral sequences are expressed in the epididymis and uterus of Syrian hamsters.
Combined androgen and oestrogen treatment of male or female Syrian hamsters results via an unknown mechanism in the formation of leiomyosarcomas in the reproductive tract. We have examined the possibility that retroviral gene expression may play a role in tumorigenesis. Evidence of virus-like particles in epididymis and seminal fluid is shown in electron micrographs. We identified expressed retroviral sequences by using RT-PCR to amplify a conserved retroviral reverse transcriptase coding region in RNA isolated from epididymis, testis, clarified seminal fluid and uterus. Phylogenetic analysis allowed us to classify the sequences into two distinct groups: (1) mammalian type-C viruses, having similarity to Moloney murine leukaemia virus, feline leukaemia virus and gibbon ape leukaemia virus amongst others; (2) a mixed ABCD group containing, for example, Chinese hamster and murine intracisternal A-particle virus sequences, mouse mammary tumour virus and human and simian retroviral sequences. The presence of putative full-length retrovirus related to mammalian type-C viruses in the epididymis and uterus was confirmed by Northern blot analysis. However, steroid treatment did not alter retroviral RNA levels in the epididymis or in a uterine tumour relative to untreated uterus. In summary, Syrian hamster reproductive tissues were found to express unique retroviral sequences; however, their role, if any, in hormonal carcinogenesis remains unresolved.