| Abstract: |
GEO is a well-differentiated colon cancer cell line that coexpresses the epidermal growth factor-like growth factors CRIPTO (CR), amphiregulin (AR), and transforming growth factor or (TGF-α). Antisense 20-mer phosphorothioate oligodeoxynncleotides (AS S-oligos) directed against CR, AR, and TGF-α mRNAs were equipotent in their ability to inhibit both the anchorage dependent growth and the anchorage-independent growth (AIG) of GEO cells, with a 50% inhibitory concentration of about 5 μM in the AIG assay. A supraadditive effect was observed when a combination of S-oligos was used. For example, a combination of two different AS S-oligos (either AR + CR, or TGF-α + CR, or TGF-α + AR) at a concentration of 1 μM each (total concentration, 2 μM) resulted in 50% inhibition of GEO cells AIG, whereas the use of each AS S-Oligo at a 1 or 2 μM concentration resulted respectively in about 10 and 20% growth inhibition. A combination of the three AS S-oligos was even more effective, resulting in about 60% inhibition of GEO cells AIG at a concentration of 1 μM each (3 μM total concentration). The AS S-oligos were also able to inhibit specifically the expression of either AR, CR, or TGF-α proteins in GEO cells, as assessed using immunocytochemistry or Western blot analysis. Finally, a supraadditive growth inhibitory effect of the AS S-oligos and an epidermal growth factor receptor-blocking antibody (monoclonal antibody 528) was observed. These data suggest that the use of a combination of AS S-oligos directed against different growth factors and antibodies directed against their receptors might result in an efficient inhibition of colon carcinoma cell growth. |
