Abstract. CD44 is a causal factor for tumor invasion, metastasis and acquisition of resistance to apoptosis. CD44 knockdown using inducible short hairpin RNA (shRNA) significantly reduces cell growth and invasion. Short hairpin RNA against CD44 and pGFP-V-RS-vector was used for knockdown of CD44 expression in SW620 colon cancer cells. Cell growth, invasion and migration assay, immunofluorescence for β-catenin expression and Western blotting for Wnt signaling molecules were analyzed. Cell cycle analysis and Western blot analysis for apoptotic molecules were evaluated. Short hairpin RNA against CD44 reduced the expression of CD44. Cell proliferation, migration and invasion were markedly inhibited and apoptosis was increased in shRNA CD44-transfected cells. Knockdown of CD44 decreased the phosphorylation of PDK1, Akt and GSK3β, and β-catenin levels. Decreased phosphorylated Akt led to an increase in phosphorylated FoxO1 and induced cell cycle arrest in the G 0 -G 1 phase and a decrease in the S phase. The levels of Bcl-2 and Bcl-xL expression were down-regulated, while the levels of BAX expression and cleaved caspase-3, -8 and -9 were increased. CD44 knockdown by way of shRNA inhibited cell proliferation and induced cell apoptosis. This can be used as a therapeutic intervention with the anti-survival/pro-apoptotic machinery in human colon cancer.

Elevated CD133 mRNA levels may represent more aggressive tumor biology and poorer survival in patients with colorectal cancer, correlating with a high level of MSI status. Larger prospective studies are required to confirm these findings.