| [Backgrounds]Colorectal cancer is the most common malignancy tumor in Western Europe, NorthAmerica and other developed countries, and one of nine common malignant tumors inChina. In the past30years, the incidence of colon cancer is on rise in majority ofcountries, including China. From the epidemiological point of view, the colon cancer isasociated with social environment, lifestyle and genetic factors, even though theetiology of colon cancer and the exact molecular mechanism is not fully understood.Recently, the environment factors/pollutants are a major health concerns.Among all environmental pollutants,60%-70%are inorganic pollutants, whileArsenic and Cadmium are on the top list of inorganic, heavy metal pollutants. Arseniteis widely found in soil, food, drinking water, and rarely in some traditional Chinesemedicines. Arsenite exposure has become a global health problem. International Agencyfor Research on Cancer (IARC) recognized it as a class I chemical carcinogen.Epidemiological studies show that arsenite is closely associated with skin, lung, bladder,liver and colon cancer. Other studies found that arsenite not only promote thecancerogenesis of colon cancer, but also the invasion and metastasis. Nevertheless, theexact underlyingmechanism is unclear.The epithelial-mesenchymal transition (EMT) refers to a specific patho-orphysiological process, in which the epithelial cells lose polarity and the adhesioncapacity with surrounding cells while gain ability of migration and invasion. EMT is acomplex process where cells undergo a switch from epithelial phenotype tomesenchymal phenotype. Multi-genes, multi-steps and multi-stages are involved in EMT; nevertheless, EMT is an early key event necessary for gastrointestinal tumorinvasion and metastasis. It is known that arsenic trioxide promote the growth andmetastasis of colon cancer cells, but it is unclear whether EMT is involved. This studyintends to explore whether the low concentration of arsenite promotes intestinal tumorcell proliferation and invasion by stimulating epithelial-to-mesenchymal transition.[Methods]We establish the HT-29cell model with chronic AS treatment (15nM). We detectedthe effects of AS on cell growth, colony forming, invasion and migration and thenanalysis the possible molecular mechanisms through Western Blotting andimmunostaining.[Results](1). Establish the HT-29cell model with chronic AS treatment (15nM).(2). The Effects of AS on HT-29cells growth: MTT and cell cycle assay found thatcontrol and AS (30) groups have similar cell proliferation rate, while AS (60) group hasan increased proliferation rate.(3) Plate and soft agar colony forming assay indicated that AS treated cells, especiallyAS (60) group, have increased proliferation and non-anchored growth capacity.(4). AS on invasion and metastasis: Wound healing assay showed that cell migrationrate was obviously higher in AS (60) cells. Transwell assay demonstrated that theinvasion rate was increased in AS treatment groups.(5). The effects of AS on in vivo tumorigenesis: the tumor weight and volume of AStreatment cells were significantly higher than the control group.(6). EMT is involved： Cell morphology suggested that epithelial cells changecytoskeleton, lose polarity and increase the space between the cells. Adhesion assay invitro found that the rate of cell adhedion in AS (60) is lower than the control and the AS(30) groups. Immunofluorescence assay demonstrated that the expression level ofE-cadherin was significantly decreased and the expression of vimentin was markedly increased. Western Blotting also found that acute exposure to AS also induced theEMT-like phenotypical shift, i.e., downregulation of the expression of epithelial markerand upregulation of the expression of mesenchymal marker.[Conclusion]1. AS promotes HT-29cells proliferation, invasion, migration and tumorigenesisability.2. EMT is involved in AS treated HT-29cells. |
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