CIP2A is overexpressed in esophageal squamous cell carcinoma

A human oncoprotein-designed cancerous inhibitor of PP2A (CIP2A) has been recently identified, which can stabilize c-Myc protein by inhibiting its degradation mediated by protein phosphatase 2A (PP2A) in tumor cells and promote the proliferation of various cancer cells. Esophageal squamous cell carcinoma (ESCC) is a highly aggressive cancer with poor prognosis worldwide. However, the underlying molecular mechanism of the development of ESCC is still poorly understood. In the present study, the CIP2A expression between normal and malignant esophageal tissues was compared by immunohistochemical analysis; moreover, the mechanisms of CIP2A-mediated tumorigenesis were investigated by evaluating its role in cell proliferation, cell cycle, apoptosis and senescence. We found that the positive staining of CIP2A was found in 36 of 40 (90%) of cancer tissues, whereas only 8 of 40 (20%) normal esophageal mucosa exhibited positive CIP2A staining. The CIP2A is significantly overexpressed in human esophageal tumors when compared with normal tissues (χ² = 39.6, P < 0.01). On the other hand, the CIP2A expression was not associated with age, gender, tumor burden, or differentiation status. Depletion of CIP2A expression led to impaired clonogenicity and senescence, which is the primary mechanism of CIP2A in oncogenesis. Therefore, CIP2A may be a candidate in diagnosis and therapy of esophageal cancer.