INTERRUPTION OF A TRANSFORMING GROWTH-FACTOR-ALPHA AUTOCRINE LOOP IN CACO-2 CELLS BY ANTISENSE OLIGODEOXYNUCLEOTIDES

Background & Aims: We have previously shown that Caco-2 cell proliferation is driven by basolateral membrane epidermal growth factor receptors, The aim of this study was to investigate whether autocrine production of transforming growth factor alpha (TGF-alpha) activates these receptors and stimulates proliferation using antisense oligodeoxynucleotides, Methods: Caco-2 cells grown on microporous membranes or Jurkat cells were exposed to conventional or 5' cholesterol-modified oligodeoxynucleotides synthesized with random, antisense, or missense base sequences, Indices of proliferation were measured, including [H-3]thymidine or [H-3]uridine uptake for studies of short-term stimulation and the methylthiotetrazole assay as an index of cell number increase over longer periods, Secretion of TGF-alpha by cells was detected using a soft agar bioassay, Results: Incubation with antisense oligodeoxynucleotides inhibited TGF-alpha secretion compared with controls, Random and missense oligodeoxynucleotides had no effect on proliferation, The TGF-alpha antisense oligodeoxynucleotides markedly inhibited proliferation, an effect that was abolished by adding TGF-alpha to the medium, Oligonucleotides had no effect on Jurkat cells, a lymphocytic cell line lacking epidermal growth factor receptors, Cholesterol-modified oligodeoxynucleotides were more effective and specific than unmodified oligodeoxynucleotides. Conclusions: Caco-2 cell proliferation is driven by autocrine stimulation of epidermal growth factor receptors by TGF-alpha. This mechanism may be effectively inhibited by antisense oligodeoxynucleotides, particularly those modified by the 5' attachment of cholesterol.