Histochemical and immunohistochemical evidence of tumor heterogeneity in colorectal cancer.

INTRODUCTION: Intratumoral heterogeneity implies the existence of differences between tumor cells, which can best be shown by histochemical and immunohistochemical techniques. The histological study is a mandatory step in any research aimed at characterizing tumor heterogeneity. Immunohistochemistry (IHC) also plays an important role in the differentiation of tumor types, assessing aggressiveness.

MATERIALS AND METHODS: Investigated group consisted of 50 patients with colorectal adenocarcinoma, for each were recorded clinicopathological data and harvested samples intraoperatively, which were included in paraffin blocks. We perform Hematoxylin-Eosin staining for histological grade and other indices. IHC study used Avidin-Biotin-Peroxidase (ABC), with the markers: CK7, CK20, MUC1, MUC2, Ki-67, PCNA, p53, KRAS, BCL2, PTEN, EGFR. The resulting data were analyzed by statistical methods.

RESULTS: Most of colorectal adenocarcinoma studied had no special histological features and had G2 grade. IHC detected in most cases the CK20+÷CK7- phenotype (78%) and MUC1 (74%) protein expression. The proliferation markers (Ki-67 and PCNA) were present in all tumor mass with a variable index, which shows high intratumoral heterogeneity, but p53 and KRAS were distributed more uniformly, showing low intratumoral heterogeneity. PTEN was expressed nuclearly in 86% of the cases and EGFR in 42%.

CONCLUSIONS: The expression profiles of cytokeratins and mucins in the colorectal adenocarcinomas are useful in defining tumor phenotypes with different prognosis and therapy. We found a significant positive correlation between KRAS protein expression and BCL2 and TP53 expression. The study demonstrated the intratumoral and intertumoral heterogeneity, expressed at phenotypic level.