c-MET expression level in primary colon cancer: a predictor of tumor invasion and lymph node metastases.

Abstract

PURPOSE: Both c-MET and vascular endothelial growth factor (VEGF)-C expression are important factors in primary carcinoma progression. We hypothesized that overexpression of c-MET and/or VEGF-C mRNA in primary colorectal cancer (CRC) can predict tumor invasion and regional metastasis. EXPERIMENTAL DESIGN: The level of c-MET and VEGF-C mRNA expression was assessed using a quantitative RT-RealTime PCR assay on early stage primary CRC tumors (n = 36). RESULTS: The c-MET mRNA copy number ranged from 1.18 x 10(2) to 1.11 x 10(6) copies (median 5.17 x 10(4)) per 250 ng of RNA from CRC specimens. c-MET mRNA copies in CRC specimens was significantly higher than that from normal colon mucosal epithelium (P = 0.0001). c-MET mRNA copies significantly correlated with the depth of invasion: T(1) versus T(2), P = 0.007; T(1) versus T(3)/T(4), P = 0.0001; T(1) versus T(2) versus T(3)/T(4), P = 0.0005; and T(1)/T(2) versus T(3)/T(4), P = 0.011. c-MET copy number in primary CRC of N(1)/N(2) staged patients was significantly higher than N(0) cases (P < 0.03). Expression levels of c-MET mRNA were verified with immunohistochemistry analysis of c-MET protein expression in CRC specimens and normal mucosal epithelium. The VEGF-C mRNA copies of primary CRC assessed ranged from 0 to 1.65 x 10(5) copies (median 580). Although VEGF-C mRNA copies in CRC primary tumors were significantly higher than normal colon mucosal epithelium (P = 0.0008), it did not correlate with any major clinicopathological parameters of CRC. CONCLUSIONS: This study indicates c-MET mRNA overexpression in primary CRC may be an important prognostic marker for early stage invasion and regional disease metastasis.