Oncogenic role of the chromobox protein CBX7 in gastric cancer

The expression of CBX7 and its potential target protein p16(INK4a) in gastric cancer cell lines and gastric tumors was assayed by Western blot analysis and immunohistochemistry(IHC). The correlations between CBX7 expression and p16(INK4a), clinicopathological characteristics, and prognosis were analyzed. Gastric cancer cell line SGC-7901 was transfected with CBX7 siRNA expressing plasmids, and the expression of various proteins was analyzed by Western blot analysis. Cellular senescence, anchorage independent growth, and cell migration assays were performed to determine the functional role of CBX7 in gastric cancer cells.CBX7 was found to be overexpressed in gastric cancer cell lines and gastric tumors. Overexpression of CBX7 in gastric cancer tissues correlated with patients' age, clinical stage and lymph node metastasis. Knockdown of CBX7 expression in gastric cancer cells led to increased cellular senescence, decreased cellular proliferation and migration ability, accompanied by upregulation of p16(INK4a).CBX7 acts as an oncogene in the carcinogenesis and progression of gastric cancer, and it may regulate tumorigenesis, cell migration and cancer metastasis partially via p16(INK4a) regulatory pathway.Polycomb group (PcG) proteins are a class of epigenetic regulators, which always form multiprotein complexes to exert their functions in regulating cell proliferation, senescence and tumorigenesis via well-known growth regulatory pathways [1]. More and more studies have implicated the deregulation of different PcG proteins in carcinogenesis and neoplastic progression. Bmi-1 is one of the best known PcG gene, which was initially identified for its ability to cooperate with c-Myc in lymphomagenesis and subsequently was found to be overexpressed in many kinds of human cancers and thus was accepted as an oncogene [2-10]. Overexpression of Bmi-1 has been shown to immortalize and transform normal human cells via inhibiting cellular senescence, which constitutes a powerful ba