REPORTS Expression of Human Herpesvirus 8-Encoded Cyclin D in Kaposi’s Sarcoma Spindle Cells

Background: Human herpesvirus 8 (HHV-8) DNA sequences have been detected in Kaposi’s sarcoma, in primary effusion lymphoma (an unusual highgrade non-Hodgkin’s lymphoma seen primarily in patients with acquired immunodeficiency syndrome [AIDS]), and in Castleman’s disease (a rare lymphoproliferative disorder); however, proof that HHV-8 is involved in the pathogenesis of these diseases remains to be established. HHV-8 contains a gene, i.e., v-cyclin D, that is a homologue of the cellular cyclin D2 gene, which encodes a protein that promotes passage through G1 phase of the cell cycle. Previous studies have identified v-cyclin D messenger RNA (mRNA) in biopsy specimens of Kaposi’s sarcoma. In this study, we isolated a full-length v-cyclin D complementary DNA and characterized the pattern of v-cyclin D mRNA expression in Kaposi’s sarcoma. Methods: Standard methods were used to construct and to screen HHV-8 genomic and complementary DNA libraries. Reverse transcription–polymerase chain reaction (RT–PCR) methods and in situ hybridization with RNA probes were used to examine v-cyclin D mRNA expression. Results: RT–PCR demonstrated the presence of v-cyclin D mRNA in biopsy specimens of AIDSrelated Kaposi’s sarcoma, in earlypassage spindle cells from classical (i.e., not AIDS-related) Kaposi’s sarcoma, and in spindle cells isolated from the peripheral blood of patients with AIDS-related Kaposi’s sarcoma. In situ hybridization indicated that mRNAs for v-cyclin D and kaposin, an HHV-8 latency-associated gene, were present in approximately 1% of the spindle cells in early patch lesions and approximately 60% of the spindle cells in late nodular lesions of Kaposi’s sarcoma. Conclusions: Spindle cells of Kaposi’s sarcoma, which have been regarded as the tumor cells of this cancer, contain v-cyclin D mRNA. Expression of vcyclin D protein may be involved in the pathogenesis of Kaposi’s sarcoma by promoting cell proliferation. [J Natl Cancer Inst 1997;89:1868–74]