Epithelial membrane protein 1 negatively regulates cell growth and metastasis in colorectal carcinoma

AIM:To determine the expression and function of epithelial membrane protein 1(EMP1)in colorectal carcinoma.METHODS:Colorectal samples were taken from cancer lesions and adjacent normal tissue in colorectal cancer patients immediately after endoscopic biopsy.A portion of the sample was either fixed in 4%paraformaldehyde and embedded in paraffin for immunohistochemistry or stored in liquid nitrogen for Western blot.In order to determine protein expression of EMP1in colorectal cancer(n=63)and normal tissue(n=31),semi-quantitative immunohistochemistry and Western blot were utilized.For in vitro studies,the human colorectal cancer cell line SW-480 was maintained in RPMI-1640 medium supplemented with 10%fetal bovine serum.Recombinant lentivirus mediated overexpression of EMP1 in SW-480 cells was quantified by real-time reverse transcription-polymerase chain reaction and Western blot.Control SW-480 cells were transfected with an empty vector.To further study the effect of EMP1 overexpression in SW-480 cells,cell proliferation,apoptosis,migration and invasion assays were conducted.RESULTS:Expression of EMP1 was significantly lower in colorectal cancer tissue than in normal tissue using both immunohistochemistry(39.7%vs 90.3%of tissues,P<0.05)and Western blot(0.126±0.022 vs0.632±0.053,P<0.05).The level of EMP1 protein expression was not correlated with gender,age,or tumor location.Decreased expression of EMP1 was significantly correlated with T stage,lymph node metastasis,clinic stage,and histological grade in patients with colorectal cancer(P<0.05).According to Kaplan-Meier analysis,low EMP1 expression correlated significantly with poor overall five-year survival(34.2%vs 64.0%survival,P<0.05).SW-480 cells transfected with EMP1 had a lower survival fraction,higher cell apoptosis(12.1%±1.3%vs 3.1%±0.6%,P<0.05),a significant decrease in migration and invasion(124.0±17.0 and 87.0±12.0,respectively vs 213.0±29.0 and 178.0±21.0,respectively,P<0.05),higher caspase-9(0.635±0.063 vs0.315±0.032,P<0.05),and lower VEGFC protein expression(0.229±0.021 vs 0.519±0.055,P<0.05)relative to cells not transfected with EMP1.CONCLUSION:Low EMP1 expression in colorectal cancer is associated with increased disease severity,suggesting that EMP1 may be a negative regulator of colorectal cancer.