Effects Of ALCAM Gene Silencing On Proliferation And Invasiveness Of Human Hepatocarcinoma Cell Line HepG2

Background Activated leukocyte cell adhesion molecule(ALCAM) is a member of immunoglobulin gene superfamily. It is mainly expressed on leucocytes and thymic epithelial cells. ALCAM mediates cell-cell interactions by both heterophilic(ALCAM-CD6) and homophilic(ALCAM-ALCAM). Studies show that ALCAM plays a role in tumorigenesis and progression.ALCAM expression is closely correlated with invasion and metastasis of several human tumors.Objective To investigate the association between the expression level of ALCAM and hepatocellular carcinoma(HCC) and to explore the role of ALCAM in the progression of HCC.Methods1. The mRNA and protein expression of ALCAM in 52 matched pairs of HCC tissues and corresponding normal tissues were measured by RT-qPCR and immunohistochemical staining to detect the association between ALCAM expression and clinicopathological characteristics.2. Recombinant adenovirus were generated using pSES-HUS Technology. Adenoviruses ALCAM-siRNA then infected human hepatocarcinoma cell line HepG2 cells. The efficiency of ALCAM siRNA were examined by RT-PCR and Western Blot.3. ALCAM expression was downregulated in the HepG2 cells following transfection with siRNA targeting the ALCAM gene. Cell proliferation was analyzed by MTT assay and the apoptosis of the cells was determined by flow cytometry. Then, cell migration was detected by transwell assays.Results1. The outcomes intimated that the level of ALCAM expression was lower in tumors from patients who in lower differentiation grade compared with moderate or high differentiation grade(P=0.024), tumors had intrahepatic metastasis compared with those patients without(P=0.019), but has no significant correlation with age, sex, level of AFP, tumor size and TNM Stages, as shown in the all 52 cases of HCC.2. Recombinant adenoviruses si RNAs targeting for ALCAM gene were successfully constructed and could effectively inhibited the expression of ALCAM gene in HepG2 cells.3. The inhibition of ALCAM expression suppressed the proliferation and induced the apoptosis of HCC cells, however, promoted HCC cells migration.Conclusion1. Compared with the corresponding normal tissues, ALCAM is abundantly expressed in HCC tissues, and reduced ALCAM expression is associated with low differentiation grade and intrahepatic metastasis. ALCAM is not only a promising candidate of biomarker in HCC, but also a potential marker for risk prediction of metastasis.2. ALCAM expression in the HepG2 cells was markedly decreased with ALCAM siRNA, which makes preparation for the subsequent experiments.3. Downregulation of ALCAM expression reduced HCC cells proliferation and induced cells apoptosis, however, promoted HCC cells migration. The results revealed that ALCAM may plays an complicated role in the development of HCC. The molecular mechanisms behind these observations should be further studied.