Tumor hypoxia figures heavily in malignant progression by altering the intracellular glucose metabolism and inducing angiogenic factor production, thus, selecting and expanding more aggressive cancer cell clones. Little is known, however, regarding hypoxia-induced antigenic changes in cancers. We investigated the expression of N-glycolyl sialic acid (NeuGc)-G M2 , a cancer-associated ganglioside containing non-human sialic acid, NeuGc, in human cancers. Cancer tissues prepared from patients with colon cancers frequently expressed NeuGc-G M2 , whereas it was virtually absent in nonmalignant colonic epithelia. Studies on cultured cancer cells indicated that the non-human sialic acid was incorporated from culture medium. Hypoxic culture markedly induced mRNA for a sialic acid transporter, sialin, and this accompanied enhanced incorporation of NeuGc as well as N-acetyl sialic acid. Transfection of cells with sialin gene conferred accelerated sialic acid transport and induced cell surface expression of NeuGc-G M2 . We propose that the preferential expression of NeuGc-G M2 in cancers is closely associated with tumor hypoxia. Hypoxic culture of tumor cells induces expression of the sialic acid transporter, and enhances the incorporation of non-human sialic acid from the external milieu. A consequence of this is the acquisition of cancer-associated cell surface gangliosides, typically G M2 , containing nonhuman sialic acid (NeuGc), which is not endogenously synthesized through CMP-N-acetyl sialic acid hydroxylase because humans lack the gene for the synthetic enzyme. As hypoxia is associated with diminished response to radiotherapy and chemotherapy, NeuGc-G M2 is a potential therapeutic target for hypoxic cancer cells. (Cancer Res 2006; 66(6): 2937-45)

Selectin-dependent cell adhesion mediates inflammatory extravasation and routine homing of lymphocytes. Most resting peripheral T lymphocytes lack expression of sialyl Lewis X, the carbohydrate ligand for selectins, and are induced to strongly express it upon activation. T helper 1 (Th1) cells are known to more preferentially express sialyl Lewis X as compared with T helper 2 (Th2) cells upon activation. The molecular basis for this preferential expression, however, has not been elucidated to date. Here we show that the gene for fucosyltransferase VII (FUT7), the rate-limiting enzyme for sialyl Lewis X synthesis, is a unique example of the human genes with binding sites for both GATA-3 and T-bet, two opposing factors for Th1 and Th2 development, and is regulated transcriptionally by a balance of the two interacting transcription factors. T-bet promotes and GATA-3 represses FUT7 transcription. Our results indicated that T-bet interferes with the binding of GATA-3 to its target DNA, and also that GATA-3 significantly interferes with the binding of T-bet to the FUT7 promoter. T-bet has a binding ability to GATA-3, CBP͞P300, and Sp1 to form a transcription factor complex, and GATA-3 regulates FUT7 transcription by phosphorylationdependently recruiting histone deacetylase (HDAC)-3͞HDAC-5 and by competing with CBP͞P300 in binding to the N terminus of T-bet. Suppression of GATA-3 activity by dominant-negative GATA-3 or repressor of GATA (ROG) was necessary to attain a maximum expression of FUT7 and sialyl Lewis X in human T lymphoid cells. These results indicate that the GATA-3͞T-bet transcription factor complex regulates the cell-lineage-specific expression of the lymphocyte homing receptors.fucosyltransferase ͉ helper memory T cells ͉ lymphocyte homing ͉ selectin ͉ GATA-3͞HDAC-3 interaction