Inverse correlation of phospho-KDR/Flk-1 expression and stage of colorectal cancer: Implication of the significance of neoangiogenesis in activated VEGFR -2 expressing early stage colorectal adenocarcinomas

The activation of vascular endothelial cell growth factor receptors (VEGFRs) plays an essential role in cancer progression. In this study, we investigated the expression of phosphorylated VEGFR-2 (or phospho-KDR/Flk-1), the activated form of VEGFR-2, in human colorectal adenomas and colorectal adenocarcinomas. Phospho- KDR/Flk-1 showed weak expression in the normal colorectal tissue. Phospho- KDR/Flk-1 was mainly stained in the cytoplasm of colorectal adenomas, and was stained in both the cytoplasm and nuclei colorectal adenocarcinomas. There was no indication of increased phospho-KDR/Flk-1 expression in the colorectal adenocarcinomas, as compared to that of colorectal adenomas. Furthermore, there was an inverse relationship of phospho-KDR/Flk-1 expression with cancer stage (p < 0.0001), lymph node metastasis (p = 0.011), and distant metastasis (p = = 0.021) of the colorectal adenocarcinomas. Our results indicate that early stage colorectal adenocarcinomas with highly activated (phosphorylated) VEGFR-2 expression may indicate the significance of neoangiogenesis of the tumors.