Overexpression of ZEB2 at the invasion front of colorectal cancer is an independent prognostic marker and regulates tumor invasion in vitro.

PURPOSE: Epithelial-to-mesenchymal transition (EMT) plays a pivotal role in tumor invasion and dissemination. EMT occurs predominantly at the tumor edge where it is induced by cytokines, the extracellular matrix environment, or hypoxia. In the tumor cell, it is further mediated by several transcription factors and microRNAs. The aim of this study was to explore the expression of EMT-associated genes at the invasive front in colorectal cancer and to evaluate their prognostic significance. EXPERIMENTAL DESIGN: We evaluated the expression of 13 EMT-associated genes at the invasion front of 30 colorectal liver metastases by quantitative real-time PCR. Immunostaining against zinc finger E-box-binding homeobox 2 (ZEB2) was carried out on 175 primary colorectal cancer specimens and 30 colorectal liver metastases and correlated to clinical and histopathologic data. DLD-1 cells were transfected with siRNA and subjected to migration and invasion assays. RESULTS: Gene expression analysis and immunohistochemistry showed an upregulation of ZEB2 at the invasion front in primary colorectal cancer and liver metastases. Overexpression of ZEB2 at the invasion front correlated significantly with tumor stage in primary colorectal cancer. Moreover, univariate and multivariate analysis revealed overexpression of ZEB2 at the invasion front as an independent prognostic marker for cancer-specific survival. Downregulation of ZEB2 by siRNA decreased the migration and invasion capacity of DLD-1 cells in vitro. CONCLUSIONS: Overexpression of ZEB2 at the invasion front correlates with tumor progression and predicts cancer-specific survival in primary colorectal cancer. Therefore, ZEB2 may be interesting as biomarker and potential target for treatment of colorectal cancer.

Invasion front-specific expression and prognostic significance of microRNA in colorectal liver metastases.

The tumor edge of colorectal cancer and its adjacent peritumoral tissue is characterized by an invasion front-specific expression of genes that contribute to angiogenesis or epithelial-to-mesenchymal transition. Dysregulation of these genes has a strong impact on the invasion behavior of tumor cells. However, the invasion front-specific expression of microRNA (miRNA) still remains unclear. Therefore, the aim of the present study was to investigate miRNA expression patterns at the invasion front of colorectal liver metastases. Laser microdissection of colorectal liver metastases was performed to obtain separate tissue compartments from the tumor center, tumor invasion front, liver invasion front and pure liver parenchyma. Microarray expression analysis revealed 23 miRNA downregulated in samples from the tumor invasion front with respect to the same miRNA in the liver, the liver invasion front or the tumor center. By comparing samples from the liver invasion front with samples from pure liver parenchyma, the tumor invasion front and the tumor center, 13 miRNA were downregulated. By quantitative RT-PCR, we validated the liver invasion front-specific downregulation of miR-19b, miR-194, let-7b and miR-1275 and the tumor invasion front-specific downregulation of miR-143, miR- 145, let-7b and miR-638. Univariate analysis demonstrated that enhanced expression of miR-19b and miR-194 at the liver invasion front, and decreased expression of let-7 at the tumor invasion front, is an adverse prognostic marker of tumor recurrence and overall survival. In conclusion, the present study suggests that invasion front-specific downregulation of miRNA in colorectal liver metastases plays a pivotal role in tumor progression.

Low expression of aldehyde dehydrogenase 1A1 (ALDH1A1) is a prognostic marker for poor survival in pancreatic cancer.

BACKGROUND: Aldehyde dehydrogenase 1 (ALDH1) has been characterised as a cancer stem cell marker in different types of tumours. Additionally, it plays a pivotal role in gene regulation and endows tumour cells with augmented chemoresistance. Recently, ALDH1A1 has been described as a prognostic marker in a pancreatic cancer tissue microarray. The aim of this study was to reevaluate the expression of ALDH1A1 as a prognostic marker on whole-mount tissue sections. METHODS: Real-time-quantitative-PCR (qRT-PCR) and Western blotting were used to evaluate the expression profile of ALDH1A1 in seven pancreatic cancer cell lines and one non-malignant pancreatic cell line. Immunostaining against ALDH1A1 and Ki-67 was performed on paraffin-embedded samples from 97 patients with pancreatic cancer. The immunohistochemical results were correlated to histopathological and clinical data. RESULTS: qRT-PCR and Western blotting revealed a different expression pattern of ALDH1A1 in different malignant and non-malignant pancreatic cell lines. Immunohistochemical analysis demonstrated that ALDH1A1 was confined to the cellular cytoplasm and occurred in 72 cases (74%), whereas it was negative in 25 cases (26%). High expression of ALDH1A1 was significantly correlated to an increased proliferation rate (Spearman correlation, p = 0.01). Univariate and multivariate analyses showed that decreased expression of ALDH1A1 is an independent adverse prognostic factor for overall survival. CONCLUSIONS: Immunohistochemical analysis on whole-mount tissue slides revealed that ALDH1A1 is more abundantly expressed in pancreatic cancer than initially reported by a tissue microarray analysis. Moreover, high expression of ALDH1A1 correlated significantly with the proliferation of tumour cells. Intriguingly, this study is the first which identifies low expression of ALDH1A1 as an independent adverse prognostic marker for overall survival in pancreatic cancer.