P01.13 * EXPRESSION OF HUMAN ENDOGENOUS RETROVIRUS K (HERV-K) IN HUMAN ASTROCYTIC TUMORS

Abstract

OBJECTIVE: Human endogenous retroviruses (HERVs) are suspected to be involved in oncogenesis and tumor progression. Transcripts of HERV-K have been detected in a multitude of human cancers as e.g., teratocarcinoma, mamma carcinoma or melanoma. The HERV-K splice variants env, rec, 1.5 kb transcript and Np9 have been suggested to be tumorigenic. To date, no reports about HERV-K expression are available concerning glioblastoma multiforme (GBM), the most common malignant brain tumor in adults, rapidly progressing and with a limited prognosis of 14.6 months in median. Therefore, we elucidated whether HERV-K transcripts could be detected in these tumors and serve as new molecular targets for treatment. METHODS: Five human GBM cell lines (U87, U138, U251, U343 and GaMG), a panel of patients' tissue samples (13 astrocytoma WHO° II, 17 GBM WHO° IV and 3 normal brain biopsies) and primary cell cultures of passages 2 and 6 were analyzed for the expression of HERV-K full length mRNA and env, rec and 1.5 kb transcripts by semiquantitative RT-PCR. RESULTS: Full length mRNA was strongly expressed in the GBM cell line U87, but weakly expressed in the GBM cell lines U138, U251, U343 and GaMG. The splice products could not be detected, despite a weak expression of env mRNA in U87 cells. Very few samples of the tissue panel showed weak expression of env mRNA, but none of the rec or 1.5 kb transcripts. Primary cells expressed the 1.5 kb transcript weakly in early passages, but lost HERV-K expression with extended culture time. CONCLUSIONS: Although expression of different splice variants of HERV-K have been reported to play a role in several malignancies and they were found in variable amounts in GBM cell lines, the lack of their expression in human tumor-biopsies confirms that HERV-K splice products do not play a role in human malignant gliomas and therefore, are not suitable as targets for new therapy regimen.