Extracellular matrix modulates expression of growth factors and growth-factor receptors in liver-colonizing colon-cancer cell lines

Advancements in 3D In Vitro Models for Colorectal Cancer

The process of drug discovery and pre-clinical testing is currently inefficient, expensive, and time-consuming. Most importantly, the success rate is unsatisfactory, as only a small percentage of tested drugs are made available to oncological patients. This is largely due to the lack of reliable models that accurately predict drug efficacy and safety. Even animal models often fail to replicate human-specific pathologies and human body's complexity. These factors, along with ethical concerns regarding animal use, urge the development of suitable human-relevant, translational in vitro models.

Whence CRIPTO: The Reemergence of an Oncofetal Factor in 'Wounds' That Fail to Heal

There exists a set of factors termed oncofetal proteins that play key roles in ontogeny before they decline or disappear as the organism's tissues achieve homeostasis, only to then re-emerge in cancer. Although the unique therapeutic potential presented by such factors has been recognized for more than a century, their clinical utility has yet to be fully realized1. This review highlights the small signaling protein CRIPTO encoded by the tumor derived growth factor 1 (TDGF1/Tdgf1) gene, an oft cited oncofetal protein whose presence in the cancer literature as a tumor promoter, diagnostic marker and viable therapeutic target continues to grow. We touch lightly on features well established and well-reviewed since its discovery more than 30 years ago, including CRIPTO's early developmental roles and modulation of SMAD2/3 activation by a selected set of transforming growth factor β (TGF-β) family ligands. We predominantly focus instead on more recent and less well understood additions to the CRIPTO signaling repertoire, on its potential upstream regulators and on new conceptual ground for understanding its mode of action in the multicellular and often stressful contexts of neoplastic transformation and progression. We ask whence it re-emerges in cancer and where it 'hides' between the time of its fetal activity and its oncogenic reemergence. In this regard, we examine CRIPTO's restriction to rare cells in the adult, its potential for paracrine crosstalk, and its emerging role in inflammation and tissue regeneration-roles it may reprise in tumorigenesis, acting on subsets of tumor cells to foster cancer initiation and progression. We also consider critical gaps in knowledge and resources that stand between the recent, exciting momentum in the CRIPTO field and highly actionable CRIPTO manipulation for cancer therapy and beyond.

Pancreatic cancer exosomes initiate pre-metastatic niche formation in the liver

Pancreatic ductal adenocarcinomas (PDACs) are highly metastatic with poor prognosis, mainly due to delayed detection. We hypothesized that intercellular communication is critical for metastatic progression. Here, we show that PDAC-derived exosomes induce liver pre-metastatic niche formation in naive mice and consequently increase liver metastatic burden. Uptake of PDAC-derived exosomes by Kupffer cells caused transforming growth factor β secretion and upregulation of fibronectin production by hepatic stellate cells. This fibrotic microenvironment enhanced recruitment of bone marrow-derived macrophages. We found that macrophage migration inhibitory factor (MIF) was highly expressed in PDAC-derived exosomes, and its blockade prevented liver pre-metastatic niche formation and metastasis. Compared with patients whose pancreatic tumours did not progress, MIF was markedly higher in exosomes from stage I PDAC patients who later developed liver metastasis. These findings suggest that exosomal MIF primes the liver for metastasis and may be a prognostic marker for the development of PDAC liver metastasis.

Transcriptional profiling identifies genes induced by hepatocyte-derived extracellular matrix in metastatic human colorectal cancer cell lines

The milieu of the liver, and in particular hepatocyte-derived extracellular matrix (hECM), is a critical factor regulating development of liver metastases of colorectal cancer (CRC) cells. The present study has investigated genes altered by hECM in CRC cells and particularly by heparan sulfate chains of hepatocyte proteoglycans. Gene profiling analysis shows that after 2 days on hECM, 226 genes are up-regulated more than 2-fold in strongly metastatic SM cells, including genes involved in growth arrest and apoptosis, signal transduction, cell migration, proliferation, communication and angiogenesis, with activation of the erbB signaling network and p53 effectors. Genes down-regulated by hECM include genes involved in lipogenesis and the S phase of the cell cycle. Further studies exploring the kinetics of gene expression after 4 and 7 days culture on hECM show induction of EGF family members and of stem cell markers. In particular, hECM, but not collagen, increases mRNA expression of HB-EGF and colon stem cell marker leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5). Expression of these genes is not induced by hECM depleted of the heparan sulfate chains of proteoglycans. Lastly, a specific cell population positive for cancer stem cell (CSC) markers LGR5, epCAM and CD133, but negative for CD44, appears after 7 days culture on hECM, a population which is reduced by 50 % in cells grown on heparan sulfated-depleted hECM. Collectively, the data suggest that hECM induces growth factors and receptors regulating proliferation of metastatic CRC in the liver and offers a growth advantage for specific populations expressing CSC markers.

Heparin regulates colon cancer cell growth through p38 mitogen-activated protein kinase signalling

OBJECTIVES

Heparin acts as an extracellular stimulus capable of activating major cell signalling pathways. Thus, we examined the putative mechanisms utilized by heparin to stimulate HT29, SW1116 and HCT116 colon cancer cell growth.

MATERIALS AND METHODS

Possible participation of the mitogen-activated protein kinase (MAPK) cascade on heparin-induced HT29, SW1116 and HCT116 colon cancer cell growth was evaluated using specific MAPK cascade inhibitors, Western blot analysis, real-time quantitative PCR and FACS apoptosis analysis.

RESULTS

Treatment with a highly specific p38 kinase inhibitor, SB203580, significantly (50-70%) inhibited heparin-induced colon cancer cell growth, demonstrating that p38 MAPK signalling is involved in their heparin-induced proliferative response. This was shown to be correlated with increased (up to 3-fold) phosphorylation of 181/182 threonine/tyrosine residues on p38 MAP kinase. Furthermore, heparin inhibited cyclin-dependent kinase inhibitor p21(WAF1/CIP1) and p53 tumour suppressor gene and protein expression up to 2-fold or 1.8-fold, respectively, and stimulated cyclin D1 expression up to 1.8-fold, in these cell lines through a p38-mediated mechanism. On the other hand, treatment with heparin did not appear to affect HT29, SW1116 and HCT116 cell levels of apoptosis.

CONCLUSIONS

This study demonstrates that an extracellular glycosaminoglycan, heparin, finely modulates expression of genes crucial to cell cycle regulation through specific activation of p38 MAP kinase to stimulate colon cancer cell growth.

The desmoplastic reaction surrounding hepatic colorectal adenocarcinoma metastases aids tumor growth and survival via alphav integrin ligation

PURPOSE

The treatment of metastatic colorectal carcinoma represents a major clinical challenge. We investigated the hypothesis that the desmoplastic reaction within the liver elicited by metastatic adenocarcinoma, characterized by collagen I deposition and altered collagen IV distribution, promotes the growth and survival of hepatic colorectal carcinoma metastases.

EXPERIMENTAL DESIGN

Partial hepatectomy specimens for metastatic colorectal adenocarcinoma were examined immunohistochemically for differential integrin expression. Human colorectal adenocarcinoma cell lines HT-29, KM12SM, and KM12c were grown on wild-type collagen I or IV, or cleavage-resistant r/r collagen I, and assessed for their growth, survival, and resistance to 5-fluorouracil. The effect of alpha(v)beta(3) and alpha(v)beta(5) integrin blockade by neutralizing antibodies was examined.

RESULTS

Collagen I, in contrast to collagen IV, significantly enhanced the growth, survival, and chemoresistance of colorectal carcinoma cells. Blockade of the alpha(v)beta(3) and alpha(v)beta(5) integrins significantly reduced colorectal carcinoma cell proliferation on collagen, especially in the cell line with the most metastatic potential. These in vitro findings correlated with the pattern of integrin expression identified within resected hepatic colorectal carcinoma metastases. Using matrix metalloproteinase-resistant r/r collagen I as a dominant negative ligand for alpha(v) integrins, we showed a key role for this integrin-ligand interaction in mediating the survival and proliferation of colorectal carcinoma cells.

CONCLUSIONS

Desmoplasia has an important role in the development of hepatic colorectal carcinoma metastasis. The interaction between integrin and collagen I is identified as a potential therapeutic target.

Amphiregulin is a promising prognostic marker for liver metastases of colorectal cancer

PURPOSE

Aberrant activation of epidermal growth factor receptors (EGFR/HER1) by ligand stimulation or heterodimerization with human epidermal growth factor 2 (HER2) is considered to play an important role in the development of colorectal carcinoma. Amphiregulin (AR) is a ligand of EGFR that might be related to the development and progression of gastrointestinal tumors. The aim of this study was to determine the AR, EGFR, and HER2 protein expression levels and to evaluate their prognostic relevance to the clinical course of colorectal cancer.

EXPERIMENTAL DESIGN

The AR, EGFR, and HER2 protein levels in primary tumors of colorectal cancer (n = 106) were examined using immunohistochemistry. Metastatic sites in liver specimens (n = 16) were also analyzed in the same manner.

RESULTS

Thirteen (81.6%) metastatic lesions of the liver stained positive for AR. Among the primary lesions of colorectal cancer, 58 (54.7%) stained positive for AR, 13 (12.3%) stained positive for EGFR, and 5 (4.7%) stained positive for HER2. When the relationships between each protein expression level and the clinicopathologic factors were examined, only the AR expression level was significantly related to liver metastasis (P = 0.0296). A multivariate analysis of liver metastasis proved that AR expression was an independent prognostic factor of liver metastasis from colorectal cancer (P = 0.0217).

CONCLUSIONS

AR expression in primary lesions of colorectal cancer is an important predictive marker of liver metastasis.

Role of cancer microenvironment in metastasis: focus on colon cancer

One person on three will receive a diagnostic of cancer during his life. About one third of them will die of the disease. In most cases, death will result from the formation of distal secondary sites called metastases. Several events that lead to cancer are under genetic control. In particular, cancer initiation is tightly associated with specific mutations that affect proto-oncogenes and tumour suppressor genes. These mutations lead to unrestrained growth of the primary neoplasm and a propensity to detach and to progress through the subsequent steps of metastatic dissemination. This process depends tightly on the surrounding microenvironment. In fact, several studies support the point that tumour development relies on a continuous cross-talk between cancer cells and their cellular and extracellular microenvironments. This signaling cross-talk is mediated by transmembrane receptors expressed on cancer cells and stromal cells. The aim of this manuscript is to review how the cancer microenvironment influences the journey of a metastatic cell taking liver invasion by colorectal cancer cells as a model.

The heparins and cancer: review of clinical trials and biological properties

The association between cancer and thromboembolic disease is a well-known phenomenon and can contribute significantly to the morbidity and mortality of cancer patients. The spectrum of thromboembolic manifestations in cancer patients includes deep vein thrombosis, pulmonary embolism, but also intravascular disseminated coagulation and abnormalities in the clotting system in the absence of clinical manifestations. Unfractionated heparin (UFH) and particularly low molecular weight heparins (LMWH-s) are widely used for the prevention and treatment of thromboembolic manifestations that commonly accompany malignancies. Malignant growth has also been linked to the activity of heparin-like glycosaminoglycans, to neoangiogenesis, to protease activity, to immune function and gene expression. All these factors contribute in the proliferation and dissemination of malignancies. Heparins may play a role in tumour cell growth and in cancer dissemination. The aims of the study are to review the efficiency of heparins in the prevention and treatment of cancer-related thromboembolic complications, and review the biological effects of heparins. Heparins are effective in reducing the frequency of thromboembolic complications in cancer patients. Meta-analyses comparing unfractionated heparins and LMWH-s for the treatment of deep vein thrombosis have shown better outcome with a reduction of major bleeding complications in patients treated with LMWH-s. LMWH have antitumour effects in animal models of malignancy: heparin oligosaccharides containing less than 10 saccharide residues have been found to inhibit the biological activity of basic fibroblast growth factor (bFGF), whereas heparin fragments with less than 18 saccharide residues have been reported to inhibit the binding of vascular endothelial growth factor (VEGF) to its receptors on endothelial cells. It has been shown that LMWH, in contrast with UFH, can hinder the binding of growth factors to their high-affinity receptors as a result of its smaller size. In vitro heparin fragments of less than 18 saccharide residues reduce the activity of VEGF, and fragments of less than 10 saccharide residues inhibit the activity of bFGF. Small molecular heparin fractions have also been shown to inhibit VEGF- and bFGF-mediated angiogenesis in vivo, in contrast with UFH. Moreover, heparin may influence malignant cell growth through other different interrelated mechanisms: inhibition of (1) heparin-binding growth factors that drive malignant cell growth; (2) tumour cell heparinases that mediate tumour cell invasion and metastasis; (3) cell surface selectin-mediated tumour cell metastasis and blood coagulation. The above evidence, together with favourable pharmaco-properties and with a reduction in major bleeding complications, suggests an important role for LMWH-s in thromboprophylaxis and in the therapy of venous thromboembolism in cancer patients. There is sufficient experimental data to suggest that heparins may interfere with various aspects of cancer proliferation, angiogenesis, and metastasis formation. Large-scale clinical trials are required to determine the clinical impact of the above activities on the natural history of the disease.

Heparin-derived disaccharides modulate proliferation and Erb-B2-mediated signal transduction in colon cancer cell lines

Organ-specific extracellular matrix (ECM) determines metastasis formation by regulating tumor cell proliferation. Hepatocyte-derived ECM enhances proliferation of colon cancer cell lines by increasing expression of tyrosine kinase receptors of the erb-B family. The active components in the ECM are the heparan sulfates, which are highly heterogeneous in their chemistry and size. We determined the effect of heparan sulfate disaccharides, of defined chemistry and present in high amounts in the liver heparan sulfate chains, on the proliferation of colon cancer cell lines and investigated the mechanism involved. The low-metastatic cell line KM12 was stimulated to proliferate by a highly sulfated disaccharide, found in the highest amounts in hepatocyte-derived heparan sulfate. Growth of the highly metastatic cell line KM12SM was inhibited by the second most common disaccharide in hepatocyte-derived heparan sulfate. The effect of both disaccharides was not accompanied by changes in the expression of erb-B1, erb-B2, erb-B3 or heregulin-alpha. We determined whether the disaccharides modified the signal-transduction pathways mediated by the erb-B receptors. The erb-B2-specific tyrosine kinase inhibitor AG825 abolished the enhancement of KM12 cell proliferation by the stimulatory disaccharide. This disaccharide increased tyrosine phosphorylation of erb-B1 and erb-B2 receptors, effects that were abolished by AG825. Moreover, the disaccharide caused increased expression of cyclin D1 and of activated MAP kinase, again reduced in the presence of the inhibitor AG825. The growth-inhibitory disaccharide reduced phosphorylation of erb-B1, but not of erb-B2, receptors in KM12SM cells. In conclusion, not only hepatocyte-derived heparan sulfate but also disaccharide molecules derived from heparan sulfate can affect colon cancer cell proliferation. Their effect is mediated by modulation of the erb-B signal transduction.

Partial purification of a liver-derived tumor cell growth inhibitor that differentially inhibits poorly-liver metastasizing cell lines: identification as an active subunit of arginase

Organ specific tumor metastasis is thought in part to require the ability of metastatic cells to respond to target-organ-associated growth factors or to avoid the effects of target organ associated growth inhibitors. We previously found that murine and rat liver-conditioned media inhibited the growth of the poorly-liver metastasizing murine RAW117-P large-cell lymphoma cells more than their highly liver-metastasizing RAW117-H10 counterparts. Using a six step chromatographic procedure, the major RAW117-P cell proliferation inhibitor from a rat liver extract was purified. The factor displayed a Mr of approximately 35,000 and an isoelectric point > 8.5. This material inhibited the growth of many cells at high concentration; however, in dose-response studies it displayed a higher IC50 for highly-liver metastatic murine RAW117-H10 lymphoma and human KM12SM colon carcinoma cells than for their poorly-liver metastatic counterparts. Attempts to identify the growth inhibitor led to the supplementation of tissue culture inhibitor assays with various components, including excess amino acids, and this was found to completely abrogate the factor's activity. Specifically, the addition of excess arginine resulted in the complete cellular recovery from inhibitor exposure. This tentatively identified the liver growth inhibitor as the enzyme arginase, a Mr approximately 10,000 multisubunit protein. A microtiter plate-based assay for arginase was developed and the purification repeated using human liver as a source of activity and the human KM12C colon carcinoma line as a target. The growth inhibitory and arginase activities were found to co-purify, identifying the factor as arginase. Highly-metastatic cells displayed no ability to preferentially inactivate or inhibit the activity of arginase, but they did they display slightly greater amounts of intracellular arginine. The liver is a major site of arginase localization as the enzyme is required for the functioning of the urea cycle. The results indicate that certain liver-colonizing tumor cells can escape, to a degree, the proliferation-damping effects of arginine depletion.