The Quantitative Proteomic Analysis In Multi-stage Of Colon Cancer

Colon cancer is the most common malignant tumors with high incidence and mortality. It is a great threat to human health. So many patients when diagnosed are already in the advanced stage occurring cancer invasion and metastasis with poor survival rate. Therefore early detection and diagnosis of colon cancer is essential to increase the treatment efficiency and improve the prognosis.Colon cancer is originated from the normal colonic mucosa(NCM), and then develops to adenomatous polyps(AP), last to carcinoma in situ(CIS) and invasive carcinoma(IC), its carcinogenesis is a gradual muti-stage process which involves multiple genes, factors and epigenetic changes. So, the protein research in the muti-stage of colon mucosa carcinogenesis has a very important scientific value and significance for elaborating the carcinogenesis mechanisms and finding early diagnosis biomarkers.In this study, laser capture microdissection(LCM) technology was used to purify muti-stage epithelial cells in colon carcinogenesis, then isotope tags for relative and absolute quantification (iTRAQ) technology combined nano liquid chromatography-tandem mass spectrometry(NanoLC-MS/MS) was used to identify the differentially expressed proteins in colon carcinogenesis. As a result,433differentially expressed proteins were identified. These proteins were divided into25clusters and three groups by K-means clustering analysis. GO analysis showed that these proteins were associated with cell communication, growth development, immunity, transport, stress response, cell adhesion, cell cycle and apoptosis. Signal pathway analysis showed these proteins were mainly involved in cancer-related signaling pathways such as the integration signaling pathway, inflammatory chemokine and cytokine signal transduction pathway, FAS signaling pathway, apoptosis signaling pathway, p53pathway, angiogenesis, Wnt signaling pathway, cadherin signaling pathway and P38MAPK signaling pathway.At the same time, Western blot and immunohistochemistry were used to verify the MYH9and PDCD4in various stages of colon tissues, the results were consistent with the results of the quantitative analysis. Statistical analysis indicated the expression levels of MYH9were significantly associated with lymph node metastasis and clinical stage.In this study, we used LCM combined with iTRAQ and NanoLC-MS/MS technique successfully established the differentially expressed proteins of colon carcinogenesis. The most important was that it was the first time that reported MYH9had a gradual up-regulation trend in colon carcinogenesis, and associated with lymph node metastasis and clinical stage, this study laid a foundation on understanding the molecular mechanisms of colon cancer and screening for diagnostic biomarkers.