BACKGROUND Basic fibroblast growth factor has been shown to be mitogenic in colon cancer cell lines. In human malignant melanoma cells, antisense oligodeoxynucleotides targeted against basic fibroblast growth factor messenger RNA significantly inhibit cell growth. However, the efficacy of such an antisense oligodeoxynucleotide strategy has not been evaluated for colon cancer cells. OBJECTIVE To investigate whether basic fibroblast growth factor can stimulate the growth of HT-29 human colon cancer cells and whether antisense oligodeoxynucleotides can inhibit growth of these cells at baseline. METHODS Western blotting analyses were used to confirm the presence of basic fibroblast growth factor protein in this cell line. Cell growth was assessed after 2, 4 and 6 days of treatment by cell counting using the trypan blue exclusion method. Phosphorothioate-modified oligodeoxynucleotides (10 microM) were used, complementary to codon 60 of the basic fibroblast growth factor messenger RNA. Cationic liposomes (DOTAP) were used to enhance the cellular uptake of the oligodeoxynucleotides. RESULTS Western blotting demonstrated the presence of basic fibroblast growth factor protein in this cell line. Basic fibroblast growth factor (1-40 ng/mL) dose-dependently stimulated cell growth and peak values were obtained at a dose of 20 ng/mL. By contrast, antisense oligodeoxynucleotide treatment significantly inhibited cell growth compared with the sense oligodeoxynucleotide-treated cells (P=0.007). This inhibition was reversed by the addition of basic fibroblast growth factor, 20 ng/mL. CONCLUSIONS Treatment targeted against basic fibroblast growth factor messenger RNA inhibits growth of HT-29 human colon cancer cells. This finding may provide a rationale for the therapeutic use of antisense oligodeoxynucleotides targeted at basic fibroblast growth factor for the treatment of colon cancer.