siRNA-induced CD44 knockdown suppresses the proliferation and invasion of colorectal cancer stem cells through inhibiting epithelial-mesenchymal transition.

CD44 has shown prognostic values and promising therapeutic potential in multiple human cancers; however, the effects of CD44 silencing on biological behaviors of cancer stem cells (CSCs) have not been fully understood in colorectal cancer. To examine the contribution of siRNA-induced knockdown of CD44 to the biological features of colorectal CSCs, colorectal CSCs HCT116-CSCs were generated, and CD44 was knocked down in HCT116-CSCs using siRNA. The proliferation, migration and invasion of HCT116-CSCs were measured, and apoptosis and cell-cycle analyses were performed. The sensitivity of HCT116-CSCs to oxaliplatin was tested, and xenograft tumor growth assay was performed to examine the role of CD44 in HCT116-CSCs tumorigenesis in vivo. In addition, the expression of epithelial-mesenchymal transition (EMT) markers E-cadherin, N-cadherin and vimentin was quantified. siRNA-induced knockdown of CD44 was found to inhibit the proliferation, migration and invasion, induce apoptosis, promote cell-cycle arrest at the G1/G0 phase and increase the sensitivity of HCT116-CSCs to oxaliplatin in HCT116-CSCs, and knockdown of CD44 suppressed in vivo tumorigenesis and intrapulmonary metastasis of HCT116-CSCs. Moreover, silencing CD44 resulted in EMT inhibition. Our findings demonstrate that siRNA-induced CD44 knockdown suppresses the proliferation, invasion and in vivo tumorigenesis and metastasis of colorectal CSCs by inhibiting EMT.