Prognostic implications of EGFR protein expression in sporadic colorectal tumors: Correlation with copy number status, mRNA levels and miRNA regulation

Sporadic colorectal cancer (sCRC) is the third most frequent cancer worldwide and the second most common cause of cancer-related deaths (mainly due metastatic dissemination). We investigated the immunohistochemical expression of frequently altered proteins in primary tumors from 51 patients (25 liver metastatic and 26 non-metastatic cases) with a median 103 months follow-up (103 months). We evaluated EGFR copy number (using SNP arrays and FISH) and its expression and regulation (by mRNA and miRNA arrays). We found differences between metastatic and non-metastatic sCRCs for MLH1 (p = 0.05), PMS2 (p = 0.02), CEA (p < 0.001) and EGFR (p < 0.001) expression. EGFR expression was associated with lymph node metastases (p = 0.001), liver metastases at diagnosis (p < 0.001), and advanced stage (p < 0.001). There were associations between EGFR expression-, EGFR gene copy number- and EGFR mRNA levels. We found potential interactions of two miRNAs targeting EGFR expression, (miR-134 and miR-4328, in non-metastatic and metastatic tumors, respectively). EGFR expression was associated with a worse outcome (p = 0.005). Multivariate analysis of prognostic factors for overall survival identified that, the expression of EGFR expression (p = 0.047) and pTNM stage (p < 0.001) predicted an adverse outcome. EGFR expression could be regulated by amplification or polysomies (in metastatic tumors), or miRNAs (miRNA-134, in non-metastatic tumors). EGFR expression in sCRC appears to be related to metastases and poor outcome.