Validation of gene expression changes of osteopontin and MMP-1 in primary and metastatic colorectal carcinomas

Background: Metastasis is one of the most important characteristics of cancer in terms of its impact on patient survival. Unfortunately, identification of altered genes during tumor metastasis is limited. Methods: Using high-throughput microarrays containing 19K spotted human oligonucleotides, gene expression of primary and matched metastatic colon cancer were compared in previous study. Although DNA microarray analysis did not demonstrate complete classification of primary and metastatic carcinoma, 80 differentially expressed genes were identified. Among these, expression of osteopontin, matrix metalloproteinase-1 (MMP-1) and serpin A1 was assessed using immunohistochemistry in a validation set containing 43 pairs from tissue microarrays. Results: The expression of osteopontin was significantly higher in metastatic carcinoma than in primary carcinoma, as indicated by mRNA expression. The expression of MMP-1 was significantly lower in metastatic carcinoma. Expression of serpin A1 was not correlated with the microarray results. Conclusions: Osteopontin and MMP-1 expression successfully classified primary and metastatic colorectal carcinomas and further studies on their clinical application is encouraged.