INFECTION WITH A TRANSFORMING GROWTH-FACTOR-ALPHA ANTISENSE RETROVIRAL EXPRESSION VECTOR REDUCES THE IN-VITRO GROWTH AND TRANSFORMATION OF A HUMAN COLON-CANCER CELL-LINE

Transforming growth factor a (TGFalpha) is a growth factor produced by colon cancer cells which may function as an autocrine growth regulator. Therefore, the proliferation and transformation of colon cancer cells might be attenuated by blocking the production of endogenous TGFalpha. GEO cells, from a human colon carcinoma cell line that expresses TGFalpha and functional epidermal growth factor (EGF) receptors, were infected with a replication-defective, recombinant amphotropic retroviral expression vector containing the neomycin-resistance gene and a 435-bp ApaI-EcoRI coding fragment of the human TGF alpha cDNA oriented in the 3' to 5' direction under the transcriptional control of the heavy-metal-inducible mouse metallothionein I promoter. Following antibiotic selection, G418-resistant colonies were pooled and expanded into a cell line (GEO TGFalpha AS cells). A 50 to 70% inhibition in the production of secreted and cell-associated TGFalpha protein was observed in GEO TGFalpha AS cells that had been maintained in CdCl2-supplemented medium. Moreover, a growth inhibition of 70% and SO% was observed in CdCl2-treated GEO TGFalpha AS cells under anchorage-dependent and anchorage-independent culture conditions, respectively. In contrast, CdCl2 treatment of parental GEO cells had no significant effect upon these parameters. Our results suggest that TGFalpha may be involved in modulating the in vitro cell growth and transformation of human colon cancer cells that express both this growth factor and its cognate receptor. (C) 1993 Wiley-Liss, Inc.