Liver resection-associated macrophage inflammatory protein-2 stimulates engraftment but not growth of colorectal metastasis at extrahepatic sites

Macrophage inflammatory protein-2 as mediator of inflammation in acute liver injury

Macrophage inflammatory protein (MIP)-2 is one of the CXC chemokines and is also known as chemokine CXC ligand (CXCL2). MIP-2 affects neutrophil recruitment and activation through the p38 mitogen-activated-protein-kinase-dependent signaling pathway, by binding to its specific receptors, CXCR1 and CXCR2. MIP-2 is produced by a variety of cell types, such as macrophages, monocytes, epithelial cells, and hepatocytes, in response to infection or injury. In liver injury, activated Kupffer cells are known as the major source of MIP-2. MIP-2-recruited and activated neutrophils can accelerate liver inflammation by releasing various inflammatory mediators. Here, we give a brief introduction to the basic molecular and cellular sources of MIP-2, and focus on its physiological and pathological functions in acute liver injury induced by concanavalin A, lipopolysaccharides, irradiation, ischemia/reperfusion, alcohol, and hypoxia, and hepatectomy-induced liver regeneration and tumor colorectal metastasis. Further understanding of the regulatory mechanisms of MIP-2 secretion and activation may be helpful to develop MIP-2-targeted therapeutic strategies to prevent liver inflammation.

TSH overcomes Braf(V600E)-induced senescence to promote tumor progression via downregulation of p53 expression in papillary thyroid cancer

The BRAF(V600E) mutation is found in approximately 40% of papillary thyroid cancers (PTC). Mice with thyroid-specific expression of Braf(V600E) (TPO-Braf(V600E)) develop PTC rapidly with high levels of serum thyroid-stimulating hormone (TSH). It is unclear to what extent the elevated TSH contributes to tumor progression. To investigate the progression of Braf(V600E)-induced PTC (BVE-PTC) under normal TSH, we transplanted BVE-PTC tumors subcutaneously into nude and TPO-Braf(WT) mice. Regression of the transplanted tumors was observed in both nude and TPO-Braf(WT) mice. They were surrounded by heavy lymphocyte infiltration and oncogene-induced senescence (OIS) was demonstrated by strong β-gal staining and absence of Ki-67 expression. In contrast, BVE-PTC transplants continued to grow when transplanted into TPO-Braf(V600E) mice. The expression of Trp53 was increased in tumor transplants undergoing OIS. Trp53 inactivation reversed OIS and enabled tumor transplants to grow in nude mice with characteristic cell morphology of anaplastic thyroid cancer (ATC). PTC-to-ATC transformation was also observed in primary BVE-PTC tumors. ATC cells derived from Trp53 knockout tumors had increased PI3K/AKT signaling and became resistant to Braf(V600E) inhibitor PLX4720, which could be overcome by combined treatment of PI3K inhibitor LY294002 and PLX4720. In conclusion, BVE-PTC progression could be contained via p53-dependent OIS and TSH is a major disruptor of this balance. Simultaneous targeting of both MAPK and PI3K/AKT pathways offer a better therapeutic outcome against ATC. The current study reinforces the importance of rigorous control of serum TSH in PTC patients.

Parenchyma-preserving hepatic resection for colorectal liver metastases

BACKGROUND

Hepatic resection of colorectal liver metastases is the only curative treatment option. As clinical and experimental data indicate that the extent of liver resection correlates with growth of residual metastases, the present study analyzes the potential benefit of a parenchyma-preserving liver surgery approach.

METHODS

Data from a prospectively maintained database of patients undergoing liver resection for colorectal metastases were reviewed. Evaluation of outcome was performed using the Kaplan-Meier method. Correlations were calculated between clinical-pathological variables.

RESULTS

One hundred sixty-three patients underwent 198 liver resections for colorectal metastases: 26 major hepatectomies, 65 minor anatomical resections, 78 non-anatomical resections, as well as 29 combinations of minor anatomical and non-anatomical procedures. Overall 1-, 3-, and 5-year survival was 93%, 62%, and 40%, respectively. Patients with repeated liver resections had a 5-year survival of 27%. Interestingly, large dissection areas were associated with a significant reduction of the 5-year survival rate (33%). Five-year survival after major hepatectomy was not significantly reduced.

CONCLUSION

For colorectal liver metastases, minor resections offer a prolonged survival compared to major hepatectomies. As patients with stage IV colorectal disease are candidates for repeat resections, preservation of hepatic parenchyma is of increasing importance in the setting of multi-modal and repeated therapy approaches.

Bone Marrow Suppression by c-Kit Blockade Enhances Tumor Growth of Colorectal Metastases through the Action of Stromal Cell-Derived Factor-1

Background. Mobilization of c-Kit⁺ hematopoietic cells (HCs) contributes to tumor vascularization. Whereas survival and proliferation of HCs are regulated by binding of the stem cell factor to its receptor c-Kit, migration of HCs is directed by stromal cell-derived factor (SDF)-1. Therefore, targeting migration of HCs provides a promising new strategy of anti-tumor therapy. Methods. BALB/c mice (n = 16) were pretreated with an anti-c-Kit antibody followed by implantation of CT26.WT-GFP colorectal cancer cells into dorsal skinfold chambers. Animals (n = 8) additionally received a neutralizing anti-SDF-1 antibody. Animals (n = 8) treated with a control antibody served as controls. Investigations were performed using intravital fluorescence microscopy, immunohistochemistry, flow cytometry and western blot analysis. Results. Blockade of c-Kit significantly enhanced tumor cell engraftment compared to controls due to stimulation of tumor cell proliferation and invasion without markedly affecting tumor vascularization. C-Kit blockade significantly increased VEGF and CXCR4 expression within the growing tumors. Neutralization of SDF-1 completely antagonized this anti-c-Kit-associated tumor growth by suppression of tumor neovascularization, inhibition of tumor cell proliferation and reduction of muscular infiltration. Conclusion. Our study indicates that bone marrow suppression via anti-c-Kit pretreatment enhances tumor cell engraftment of colorectal metastases due to interaction with the SDF-1/CXCR4 pathway which is involved in HC-mediated tumor angiogenesis.

Liver regeneration and tumour stimulation: implications of the renin-angiotensin system

Liver resection is the most effective treatment for primary liver tumours and metastasis to the liver, and remains the only potentially long-term curative therapy for patients with colorectal cancer (CRC) liver metastases. Nevertheless, there is a significant incidence of tumour recurrence following liver resection. Cellular and molecular changes resulting from resection and the subsequent liver regeneration process may influence the kinetics of tumour growth, contributing to recurrence. Although commonly associated with the systemic homeostasis of blood pressure, fluid and electrolyte, the renin-angiotensin system (RAS) has recently been shown to play a role in regulating cell proliferation, apoptosis and angiogenesis in local organs as well as in malignancies. An electronic search of the English literature on the role of the RAS in liver regeneration and tumourigenesis was performed using PubMed, with additional relevant articles sourced from reference lists. Studies have shown that the blockade of the RAS pathway stimulates liver regeneration and inhibits tumour progression. An understanding of the role of RAS in liver regeneration and tumourigenesis may enable alternative strategies to improve patient outcome and survival after liver resection. This review will discuss the role of the RAS in liver regeneration and in tumour recurrence post-liver resection. The potential of the RAS as a novel therapeutic target for CRC liver metastases patients undergoing liver resection will be outlined.

CXCR4 and CXCR7 regulate angiogenesis and CT26.WT tumor growth independent from SDF-1

Recent studies have shown that the chemokine stromal cell-derived factor (SDF)-1 and its receptor CXCR4 are involved in the metastatic process of colorectal cancer. The impact of SDF-1 on the stimulated metastatic growth during hepatectomy-associated liver regeneration is unknown. With the use of a heterotopic murine colon cancer model, we analyzed whether blockade of SDF-1 inhibits angiogenesis and extrahepatic growth of colorectal cancer after liver resection. Functional neutralization of SDF-1 by 1 mg/kg body weight anti-SDF-1 antibody only slightly delayed the initial tumor cell engraftment but also did not reduce the size of established extrahepatic tumors compared with controls. Tumor cell apoptosis was increased by anti-SDF-1 treatment only during the early 5-9-day period of tumor cell engraftment, but was found significantly decreased during the late phase of tumor growth. The initial delay of tumor cell engraftment was associated with an increase of tumor capillary density and microvascular permeability. This was associated with an increased vascular endothelial growth factor (VEGF) expression and an enhanced tumor cell invasion of the neighboring tissue. In contrast to the neutralization of SDF-1, blockade of the SDF-1 receptors CXCR4 and CXCR7 significantly reduced tumor capillary density and tumor growth. Thus, our study indicates that neutralization of SDF-1 after hepatectomy is not capable of inhibiting angiogenesis and growth of extrahepatic colorectal tumors, because it is counteracted by the compensatory actions through an alternative VEGF-dependent pathway.

Stromal cell-derived factor-1 promotes cell migration and tumor growth of colorectal metastasis

In a mouse model of established extrahepatic colorectal metastasis, we analyzed whether stromal cell-derived factor (SDF) 1 stimulates tumor cell migration in vitro and angiogenesis and tumor growth in vivo.

METHODS

Using chemotaxis chambers, CT26.WT colorectal tumor cell migration was studied under stimulation with different concentrations of SDF-1. To evaluate angiogenesis and tumor growth in vivo, green fluorescent protein-transfected CT26.WT cells were implanted in dorsal skinfold chambers of syngeneic BALB/c mice. After 5 days, tumors were locally exposed to SDF-1. Cell proliferation, tumor microvascularization, and growth were studied during a further 9-day period using intravital fluorescence microscopy, histology, and immunohistochemistry. Tumors exposed to PBS only served as controls.

RESULTS

In vitro, > 30% of unstimulated CT26.WT cells showed expression of the SDF-1 receptor CXCR4. On chemotaxis assay, SDF-1 provoked a dose-dependent increase in cell migration. In vivo, SDF-1 accelerated neovascularization and induced a significant increase in tumor growth. Capillaries of SDF-1-treated tumors showed significant dilation. Of interest, SDF-1 treatment was associated with a significantly increased expression of proliferating cell nuclear antigen and a downregulation of cleaved caspase-3.

CONCLUSION

Our study indicates that the CXC chemokine SDF-1 promotes tumor cell migration in vitro and tumor growth of established extrahepatic metastasis in vivo due to angiogenesis-dependent induction of tumor cell proliferation and inhibition of apoptotic cell death.

Adhesion molecules and chemokines: the navigation system for circulating tumor (stem) cells to metastasize in an organ-specific manner

To date, cancer is still the second most prevalent cause of death after cardiovascular diseases in the industrialized word, whereby the primary cause of cancer is not attributed to primary tumor formation, but rather to the growth of metastases at distant organ sites. For several years it was considered that the well-known phenomenon of organ-specific spreading of tumor cells is mostly a mechanical process either directed passively due to size constraints (mechanical trapping theory) or due to a fertile environment provided by the organ in which tumor cells can proliferate (seed and soil hypothesis). Both mechanisms strongly depend on the adhesive properties of tumor cells either to endothelial cells and/or cancer cells, which are facilitated by a variety of cell adhesion molecules including carbohydrates and integrins. Within the past years it became evident that the organ-specific metastatic spreading of tumor cells does not only rely on heterotypic and homotypic adhesive interactions, but also on the interplay of chemokines and their appropriate receptors. Moreover, the identification of cancer stem cells in various tumor tissues has opened new questions. Cancer stem cells possess self-renewal, differentiation, and tumor-initiating capacities. Thus these cells are ideal candidates to be the seed of a secondary tumor. In the present review we will give a brief overview about the complex process of organ-specific metastasis formation depending on the interplay of adhesion molecules, chemokines, and the putative role of cancer stem cells in metastasis formation.