High expression of ganglioside α-2,8-sialyltransferase (G_D3 synthase) gene in adult T-cell leukemia cells unrelated to the gene expression of human T-lymphotropic virus type I

Expression of ganglioside α-2,8-sialyltransferase (G_D3 synthase; EC 2.4.99.8) gene and gangliosides in human leukemia cells were analyzed. Flow cytometric analysis of various types of leukemia cells using monoclonal antibodies revealed that G_D3 was expressed at a moderate level on adult T-cell leukemia (ATL) cells and weakly on T-cell acute lymphocytic leukemia cells. Accordingly, high levels of G_D3 synthase mRNA in ATL and low levels in T-cell acute lymphocytic leukemia were demonstrated by semiquantitative reverse transcription-PCR analysis. High-level expression of the G_D3 synthase gene in ATL cells was detected in the uncultured state, and was not changed during short-term culture in vitro. This was in contrast with the rapid up-regulation of G_M2/G_D2 synthase gene, which was observed within 24 h after start of culture after the emergence of human T-lymphotropic virus type I (HTLV-I) gene expression. In cultured normal T lymphocytes with or without HTLV-I p40^tax protein, G_D3 synthase gene was almost equally expressed, whereas G_M2/G_D2 synthase gene was much more strongly expressed in the p40^tax-positive T cells. These findings indicated that the G_D3 synthase gene was highly expressed in ATL cells unrelated to HTLV-I genome expression.