[53] Clinical Aggressiveness of Myxofibrosarcomas Is Associated with Decreased Expression of p12^CDK2AP1: Prognostic Implication of a Putative Tumor Suppressor That Induces Cell Cycle Arrest and Apoptosis Via Mitochondrial Pathway

HY Huang, YL Chen, CF Li, YL Shiue. Chang Gung Memorial Hospital, Kaohsiung Medical Center, Chang Gung University, Kaohsiung, Taiwan; National Sun Yat-Sen University, Kaohsiung, Taiwan; Chi-Mei Foundation Medical Center, Tainan, Taiwan

Background: The tumorigenesis and prognostication of myxofibrosarcoma remains obscure. Attenuated endogenous expression of P12^CDK2AP1 and its active dimmer (P25^CDK2AP1) was found in myxofibrosarcoma cell lines (NMFH-1, OH931), prompting us to investigate the clinical and biological significance of this putative tumor suppressor that targets CDK2 for proteolysis.
Design: A polyclonal antibody against the P12^CDK2AP1-His fusion protein was generated to perform Western blotting and immunohistochemistry. Vectors of p12^CDK2AP1-specific cDNA and shRNA were transfected into NMFH-1 cells to analyze the effects on CDK2 expression, cell cycle regulation by flow cytometry, and apoptotic responses by assessing changes in annexin V and caspase-3, 8, 9. By tissue microarrays, P12^CDK2AP1 immunostain was interpretable in 102 primary myxofibrosarcomas and correlated with clinicopathological variables, expression of CDK2 and cleaved caspase-3, and disease-specific survival (DSS).
Results: Exogenous P12^CDK2AP1 overexpression in NMFH-1 cells induced cell cycle arrest at G0/G1 phase and downregulated CDK2 expression, and these findings were reversed by RNA interference. In NFHH-1 cells, increased cleaved products of caspases-3, 9, but not caspase-8, were detected after transfecting P12^CDK2AP1-specific cDNA, suggesting the induction of apoptosis via the mitochondrial pathway. P12^CDK2AP1 immunostain, aberrantly decreased in 63% of cases, was positively and negatively related to the expression of cleaved caspase-3 (p<0.001) and CDK2 (p=0.034), respectively. Together with higher histological grades, decreased P12^CDK2AP1 expression was predictive of worse DSS in both univariate (p=0.002) and multivariate (p= 0.015) analyses.
Conclusions: P12^CDK2AP1 expression induces both mitochondrial pathway-dependent apoptosis and cell cycle arrest with downregulated CDK2. Declined P12^CDK2AP1 expression also represents a poor prognosticator of myxofibrosarcomas.
Category: Bone & Soft Tissue

Monday, March 9, 2009 1:00 PM

Poster Session II # 21, Monday Afternoon