Diagnostic and prognostic utility of methylation and protein expression patterns of myopodin in colon cancer
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Myopodin is an actin-binding protein believed to play a tumor suppressor role in several solid neoplasias. We evaluated the potential differential myopodin methylation and expression and their clinical relevance in colon cancer. The epigenetic silencing of myopodin by hypermethylation was tested in colon cancer cells (n = 5) before and after azacitidine treatment. Myopodin methylation status was evaluated by methylation-specific PCR in colon cancer cells and colorectal tissues (n = 210) grouped in a training set (n = 62) and two independent validation series (n = 100 and n = 48) collected at independent clinical settings. Myopodin expression patterns were analyzed by immunohistochemistry on tissue arrays. Myopodin hypermethylation correlated with gene and protein expression loss, being increased in vitro by azacitidine. Myopodin was frequently methylated in colon cancer cells (four out of five). Methylation rates were 90.3%, 70.0%, and 47.8% in the training and validation sets, respectively. Myopodin methylation rendered a diagnostic accuracy of 83.9% (p < 0.0005). Cytoplasmic myopodin expression was significantly higher in non-neoplastic biopsies compared to colon tumors (p < 0.0005). Loss of myopodin expression correlated with increasing tumor stage (p = 0.011), methylation (p = 0.005), and poor overall survival (p = 0.003). In the first validation set (n = 100), myopodin methylation predicted disease-free (p = 0.046) and overall survival (p = 0.031). In the second validation cohort, myopodin methylation and protein expression patterns predicted disease-specific (p = 0.012 and p = 0.001, respectively) and overall survival (p = 0.009 and p = 0.043, respectively). Thus, myopodin was revealed to be epigenetically modified in colon cancer. The diagnostic and prognostic clinical utility of myopodin methylation and expression patterns suggest considering their assessment for the clinical management of colon cancer patients.
KeywordsColon cancer Myopodin Methylation Biomarker Tissue array Immunohistochemistry
We thank all members of the laboratory of M. Sánchez-Carbayo for the technical support and constructive suggestions in the preparation of this manuscript. We also would like to thank the Tumor Bank belonging to the Molecular Pathology Program at the Spanish National Cancer Center and all the members of our clinical collaborators at the different institutions involved in this study for the support in facilitating the tumor specimens as well as the clinical follow-up of the colon cancer cases analyzed in this study.
Spanish Ministry of Science and Innovation grant SAF2009-13035 and Mutua Madrileña 2010 (to M. Sánchez-Carbayo).
Conflicts of interest
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