Karsten Brand

Heat Shock Protein 70 Is Required for the Survival of Cancer Cells

Abstract: The major stress‐inducible heat shock protein, Hsp70, is a chaperone protein abundantly and preferentially expressed in human tumors and tumor cell lines. Owing to the ability of Hsp70 to protect cells from a wide range of apoptotic and necrotic stimuli, it has been assumed that Hsp70 may confer survival advantage to tumor cells. To investigate this hypothesis in human tumor cell lines, we generated an adenovirus expressing antisense Hsp70 (Ad.asHsp70). The effective and specific depletion of Hsp70 by Ad.asHsp70 resulted in massive cell death of all tumorigenic cell lines tested (carcinomas of breast, colon, prostate and liver as well as glioblastoma). Inspite of an effective depletion of Hsp70, Ad.asHsp70 had no effect on the survival or growth of fetal fibroblasts or non‐tumorigenic epithelial cells of breast or prostate. Anti‐apoptotic proteins Bcl‐2, Bcl‐XLand CrmA as well as peptide‐inhibitors of caspases, DEVD‐CHO and zVAD‐FMK, failed to rescue tumor cells from Ad.asHsp70‐induced cell death. These results indicate that the high expression of Hsp70 is a prerequisite for the survival of human cancer cells of various origins and reveal Hsp70 as the only protein described so far whose expression is specifically needed for the survival of tumorigenic cells.

Distinct Types of Tumor-Initiating Cells Form Human Colon Cancer Tumors and Metastases

Human colon cancer harbors a small subfraction of tumor-initiating cells (TICs) that is assumed to be a functionally homogeneous stem-cell-like population driving tumor maintenance and metastasis formation. We found unexpected cellular heterogeneity within the TIC compartment, which contains three types of TICs. Extensively self-renewing long-term TICs (LT-TICs) maintained tumor formation in serial xenotransplants. Tumor transient amplifying cells (T-TACs) with limited or no self-renewal capacity contributed to tumor formation only in primary mice. Rare delayed contributing TICs (DC-TICs) were exclusively active in secondary or tertiary mice. Bone marrow was identified as an important reservoir of LT-TICs. Metastasis formation was almost exclusively driven by self-renewing LT-TICs. Our results demonstrate that tumor initiation, self-renewal, and metastasis formation are limited to particular subpopulations of TICs in primary human colon cancer. We identify LT-TICs as a quantifiable target for therapies aimed toward eradication of self-renewing tumorigenic and metastatic colon cancer cells.

Tissue inhibitor of metalloproteinases-1 promotes liver metastasis by induction of hepatocyte growth factor signaling.

Balanced expression of proteases and their inhibitors is one prerequisite of tissue homeostasis. Metastatic spread of tumor cells through the organism depends on proteolytic activity and is the death determinant for cancer patients. Paradoxically, increased expression of tissue inhibitor of metalloproteinases-1 (TIMP-1), a natural inhibitor of several endometalloproteinases, including matrix metalloproteinases and a disintegrin and metalloproteinase-10 (ADAM-10), in cancer patients is negatively correlated with their survival, although TIMP-1 itself inhibits invasion of some tumor cells. Here, we show that elevated stromal expression of TIMP-1 promotes liver metastasis in two independent tumor models by inducing the hepatocyte growth factor (HGF) signaling pathway and expression of several metastasis-associated genes, including HGF and HGF-activating proteases, in the liver. We also found in an in vitro assay that suppression of ADAM-10 is in principle able to prevent shedding of cMet, which may be one explanation for the increase of cell-associated HGF receptor cMet in livers with elevated TIMP-1. Similar TIMP-1-associated changes in gene expression were detected in livers of patients with metastatic colorectal cancer. The newly identified role of TIMP-1 to create a prometastatic niche may also explain the TIMP-1 paradoxon.

Tumoral Immune Cell Exploitation in Colorectal Cancer Metastases Can Be Targeted Effectively by Anti-CCR5 Therapy in Cancer Patients

The immune response influences the clinical course of colorectal cancer (CRC). Analyzing the invasive margin of human CRC liver metastases, we identified a mechanism of immune cell exploitation by tumor cells. While two distinct subsets of myeloid cells induce an influx of T cells into the invasive margin via CXCL9/CXCL10, CCL5 is produced by these T cells and stimulates pro-tumoral effects via CCR5. CCR5 blockade in patient-derived functional in vitro organotypic culture models showed a macrophage repolarization with anti-tumoral effects. These anti-tumoral effects were then confirmed in a phase I trial with a CCR5 antagonist in patients with liver metastases of advanced refractory CRC. Mitigation of tumor-promoting inflammation within the tumor tissue and objective tumor responses in CRC were observed.

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. Clin Cancer Res; 17(24); 7654–63. ©2011 AACR.

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. (Cancer Sci 2011; 102: 1799–1807)

Transcriptional activation of the β-catenin gene at the invasion front of colorectal liver metastases†

β‐Catenin is a pivotal molecule of the Wnt‐signalling pathway, involved in regulation of developmental and oncogenic processes as well as in intercellular adhesion. So far, β‐catenin has been thought to be regulated mainly at the protein level. Here, we provide evidence for a transcriptional mechanism of β‐catenin regulation at the invasion front of colorectal liver metastases. In a nude mouse/LS174T cell xenograft model of colorectal liver metastases, we observed β‐catenin up‐regulation at the mRNA and protein levels and a 13.7‐fold increase of β‐catenin promoter activity in the cancer cells of the invasion front. In addition, the promoter activity was five‐fold higher in the interior of the tumour than in cells growing in cell culture. In vitro studies revealed binding of TCF‐4 to the β‐catenin promoter and reduced promoter activity by over‐expression of dominant negative TCF‐4, or β‐catenin knock‐down and increased activity by β‐catenin over‐expression, indicating that β‐catenin acts as co‐transcription factor of its own promoter. In 55% (7/13) of clinical specimens, β‐catenin mRNA was markedly elevated in the cancer cells of the invasion front. Elevation of mRNA was paralleled by increased nuclear and cytoplasmic β‐catenin protein concentrations. These data indicate that transcriptional regulation contributes to the dynamic changes of β‐catenin levels upon the confrontation of tumour cells with the host microenvironment. Copyright

Down-regulation of CXCL1 inhibits tumor growth in colorectal liver metastasis

As part of ongoing studies to obtain a global picture of invasion related events in colorectal liver metastases, here, we report our findings on gene expression of the pro-angiogenic subgroup of chemokines, the CXCL-ELR+ chemokines. Apart from their pro-angiogenic and chemoattractant function, these chemokines appear to also contribute to tumor cell transformation, growth and invasion. In our nude mouse model of colorectal liver metastases, we found CXCL1,2,3,5 and 8 (IL-8) to be up-regulated in the tumor cells of the invasion front as compared to the tumor cells in the inner parts of the tumor. ShRNA mediated down-regulation of the most prominently up-regulated group member, CXCL1/gro-alpha resulted in inhibition of cell viability, invasion and proliferation. In vivo, down-regulation of CXCL1 resulted in a nearly complete prevention of tumor growth in nude mice. Mechanistically, auto-regulatory mechanisms involving NF-kappaB and Akt appear to be involved in pro-tumorigenic functions of CXCL1.

Annexin A2 as a differential diagnostic marker of hepatocellular tumors.

While improved imaging techniques have made it possible to detect focal liver lesions smaller than 1cm in diameter, differentiating benign lesions from hepatocellular carcinoma (HCC) still remains a challenge. To address this problem and obtain a definite diagnosis, needle core biopsies are often performed, leading to an increased need for supportive ancillary techniques in the histopathological assessment of highly differentiated hepatocellular tumors. Here we evaluate the diagnostic value of immunohistologically detected Annexin A2 (ANXA2) expression in highly differentiated liver tumors. ANXA2 is a calcium-dependent phospholipid-binding protein that has been linked to malignant transformation and HCC development. Our data show that adding sinusoidal ANXA2 expression to the already established marker panel (GPC3, GS, and HSP70) increases the accuracy for the detection of well-differentiated HCC (74% sensitivity, 100% specificity). In addition, in our series, the combinations ANXA2-GPC3 and ANXA2-GS performed better compared to the other established marker combinations. In conclusion, we suggest that adding ANXA2 to the established diagnostic marker panel increases the reliability and objectivity of HCC diagnosis in liver biopsies.

Adenovirus-mediated overexpression of tissue inhibitor of metalloproteinases-1 in the liver: efficient protection against T-cell lymphoma and colon carcinoma metastasis

Matrix metalloproteinases (MMPs) are critical for metastasis of tumor cells. Tissue inhibitor of metalloproteinases‐1 (TIMP‐1), a natural MMP inhibitor, was shown to reduce metastasis in different models. Here, we investigated whether increased TIMP‐1 levels in the liver achieved by adenoviral gene transfer will effectively inhibit liver metastasis of two independent tumor cell lines.