ACTIVATION OF THE GALECTIN-1 (L-14-I) GENE FROM NONEXPRESSING DIFFERENTIATED CELLS BY FUSION WITH UNDIFFERENTIATED AND TUMORIGENIC CELLS

Expression of the galectin-1 (L-14-I) gene, elevated in most dediffere ntiated and transformed cell lines, has been studied in cell hybrid sy stems. Fusion of L-14-I nonproducing rat liver differentiated FAO cell s with dedifferentiated rat liver BRL3A cells leads to extinction of l iver-specific gene expression while L-14-I mRNA levels remain high. In terspecific hybrids produced by fusion of tumorigenic human osteosarco ma 143TK(-) with FAO cells show loss of both differentiated functions and tumorigenic phenotype and activation of the FAO L-14-I alleles. In creased expression of rat L-14-I alleles was also observed in human os teosarcoma x rat thyroid cells transient heterokaryons. The data prese nted here show that expression of the L-14-I gene is subject to domina nt positive control and that it correlates with loss of differentiatio n-specific functions, but it,is independent from tumorigenicity. L-14- I activation in FAO cells is achieved by treatment with 5-azacytidine. This result suggests that DNA demethylation is responsible or a prere quisite for L-14-I activation in hybrids.