Background: Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncoprotein inhibiting proteolytic degradation of c-MYC. In this study, we investigated the clinical relevance of CIP2A in NSCLC.
Materials and methods: We analyzed CIP2A mRNA expression in 29 NSCLC tissues using quantitative reverse transcription polymerase chain reaction (RT-QPCR). We also examined the expression of CIP2A protein by immunohistochemistry in 90 lung cancer specimens and correlated its expression with c-MYC expression and clinicopathological parameters. The functional roles of CIP2A in lung cancer cell lines were evaluated by small interfering RNA-mediated depletion of the protein followed by analyses of cell proliferation and invasion.
Results: In 29 lung cancer tissues examined, 24 of them (82.7%) exhibited much stronger levels of CIP2A mRNA compared with their corresponding normal tissues. Moreover, CIP2A mRNA expression levels correlated with c-MYC mRNA levels. Furthermore, CIP2A protein was found to be overexpressed in 72.2% of 90 human lung cancer samples and correlated with poor survival (P < 0.05). In addition, the CIP2A status was a significant prognostic factor for NSCLC patients (P = 0.0136). Depleting CIP2A expression inhibited growth and clonogenic potential in lung cancer cell lines.
Conclusions: CIP2A is an oncoprotein overexpressed in NSCLC, and its expression is associated with poor prognosis and malignant cell proliferation.