The cellular apoptosis susceptibility (CSE1L) gene has been demonstrated to regulate multiple cellularmechanisms including the mitotic spindle check point as well as proliferation and apoptosis. However, theimportance of CSE1L in human colon cancer is largely unknown. In the present study, we examined expressionlevels of CSE1L mRNA by semiquantitative RT-PCR. A lentivirus-mediated small interfering RNA (siRNA)was used to knock down CSE1L expression in the human colon cancer cell line RKO. Changes in CSE1L targetgene expression were determined by RT-PCR. Cell proliferation was examined by a high content screeningassay. In vitro tumorigenesis was measured by colony-formation assay. Cell cycle distribution and apoptosiswere detected by flow cytometric analysis. We found CSE1L mRNA to be expressed in human colon cancer cells.Using a lentivirus based RNAi approach, CSE1L expression was significantly inhibited in RKO cells, causingcell cycle arrest in the G2/M and S phases and a delay in cell proliferation, as well as induction of apoptosisand an inhibition of colony growth capacity. Collectively, the results suggest that silencing of CSE1L may be apotential therapeutic approach for colon cancer.