MUC2 siRNA reduces growth of LS174T human colon cancer cells

2240 MUC2, a high molecular-weight glycoprotein, is the major secreted mucin produced from the intestinal goblet cells. It covers intestinal epithelium and thus provides a lubricating barrier that protects mucosal surface. In this study, we determined the in vitro effect of MUC2 suppression in LS174T colon cancer cell line that produces MUC2. Cell survival was 10% and 15% lower in MUC2 small interfering RNA (siRNA) transfected cells at 48h and 96h respectively compared to controls, as quantified using a 4-methylumbelliferyl heptanoate (MUH) viability assay. Apoptotic cell death was increased by 9% and 13% in MUC2 transfected cells at 48h and 96h respectively compared to controls, as detected by the number of TUNEL-positive apoptotic cells. Expression of apoptosis-associated enzymes was increased 48h following MUC2 siRNA transfection as shown by immunoblotting for cleaved PARP and cleaved caspase-3. The number of cell counts for six days was decreased by 50% in MUC2 siRNA transfected cells when compared to controls. DNA content analysis revealed that the S-phase population was two-fold greater in MUC2 siRNA treated cells compared to controls. In summary, we have shown that siRNA knockdown of MUC2 arrested cells in S-phase, decreased cell survival and increased apoptosis. Collectively these results suggest that MUC2 augments LS174T cells survival, modulates progression through S-phase, and suppresses its apoptotic cell death. Based on these data we propose that MUC2 mucin promotes tumorigenesis of the highly aggressive mucinous colorectal cancers.