Diagnostic and prognostic utility of methylation and protein expression patterns of myopodin in colon cancer.

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 (n05) before and after azacitidine treatment. Myopodin methylation status was evaluated by methylation-specific PCR in colon cancer cells and colorectal tissues (n0210) grouped in a training set (n0 62) and two independent validation series (n0100 and n0 48) collected at independent clinical settings. Myopodin expression patterns were analyzed by immunohistochemis- try 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 biop- sies compared to colon tumors (p<0.0005). Loss of myo- podin expression correlated with increasing tumor stage (p0 0.011), methylation (p00.005), and poor overall survival (p00.003). In the first validation set (n0100), myopodin methylation predicted disease-free (p00.046) and overall survival (p00.031). In the second validation cohort, myo- podin methylation and protein expression patterns predicted disease-specific (p00.012 and p00.001, respectively) and overall survival (p00.009 and p00.043, 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.