Enhanced tumour growth in the rat liver after selective elimination of Kupffer cells

Shp2 Deficiency in Kupffer Cells and Hepatocytes Aggravates Hepatocarcinogenesis by Recruiting Non-Kupffer Macrophages

BACKGROUND & AIMS

Complex communications between hepatocytes and Kupffer cells (KCs) are known to drive or suppress hepatocarcinogenesis, with controversial data in the literature. In previous experiments that aimed to decipher hepatocyte/KC interactions, we unexpectedly unveiled a tumor-suppressing effect of polyinosinic-polycytidylic acid, a widely used inducer of MX dynamin like GTPase 1 (Mx1)-cre expression, which questioned a theory of interleukin 1a/6 cytokine circuit in hepatocyte/KC communication. The goal of this study was to clarify the controversy and decipher unique functions of KCs and non-KC macrophages in liver tumorigenesis.

METHODS

We used the C-type lectin domain family 4 member F (Clec4f)-cre system to delete Src-homology 2 domain-containing tyrosine phosphatase 2 (Shp2)/protein tyrosine phosphatase nonreceptor 11 (Ptpn11) in KCs, and a combination of Clec4f-cre and adeno-associated virus-cre to delete Shp2 in KCs and hepatocytes to investigate the effects on hepatocellular carcinoma development and immune cell compositions/activities.

RESULTS

Ablating Shp2 in KCs generated a tumor-promoting niche, which was exacerbated further by concurrent removal of Shp2 in both KCs and hepatocytes. Shp2 deficiency induced KC apoptosis and decreased its numbers, which induced compensatory recruitment of bone marrow-derived monocytes into liver. These newly recruited monocytes differentiated into non-KC macrophages with tumor-associated macrophage function, leading to aggravated tumor progression through down-regulation of CD8 T cells. Tumor-associated macrophage blockade by anti-chemokine (C-C motif) ligand 2 (CCL2) antibody inhibited hepatocellular carcinoma progression, while depletion of all macrophages had a tumor-promoting effect by increasing myeloid-derived suppressor cells (M-MDSCs) and decreasing CD8 T cells.

CONCLUSIONS

Shp2 loss in KCs or hepatocytes generated a protumorigenic microenvironment, which was exacerbated by its removal in both cell types. These results show the complexity of intercellular signaling events in liver tumorigenesis and raises caution on the use of specific Shp2 inhibitor in liver cancer therapy. Transcript profiling: RNA sequencing data are available at Gene Expression Omnibus (GSE222594).

Surgical Stress and Cancer Progression: New Findings and Future Perspectives

PURPOSE OF REVIEW

The stress response to surgery is essential for maintaining homeostasis and exhibits anti-tumor effects; however, an ongoing and exaggerated stress response may have adverse clinical consequences and even promote cancer progression. This review will discuss the complex relationship between surgical stress and cancer progression.

RECENT FINDINGS

Surgical stress exhibits both anti-tumor and cancer-promoting effects by causing changes in the neuroendocrine, circulatory, and immune systems. Many studies have found that many mechanisms are involved in the process, and the corresponding targets could be applied for cancer therapy. Although surgical stress may have anti-tumor effects, it is necessary to inhibit an excessive stress response, mostly showing cancer-promoting effects.

CD169-positive macrophages enhance abscopal effect of radiofrequency ablation therapy in liver cancer

Radiofrequency ablation (RFA) is a widely used and effective treatment for primary or metastatic liver cancer with small-size lesions. However, the therapeutic effectiveness of RFA in controlling metastatic lesion or recurrence is still limited. As the major cell population in tumor microenvironment (TME), macrophages have been reported to be recruited to RFA-treated lesion, but their roles are still unclear. Herein, we successfully established the mouse model mimicking RFA-induced abscopal effect, in which RFA eliminated the local orthotopic liver tumor but failed to control growth of distant tumor. Correspondently, RFA suppressed protumoral activation of local tumor-associated macrophages (TAMs), but failed to reprogram TAMs in distance. Importantly, although RFA led to reduced proportion of hepatic CD169⁺ macrophages in local and decreased expression of immune inhibitory molecules Tim-3 and PD-L1, these alterations were not observed for CD169⁺ macrophages in distant TME. Further RNA-seq and flow cytometry analysis showed that hepatic CD169⁺ macrophages contributed to reprograming TME through recruiting CD8⁺ T/NK cells and suppressing accumulation of MDSCs/Tregs. Consistently, depletion of CD169⁺ macrophages in CD169-DTR mouse greatly promoted liver tumor progression and largely dampened RFA-induced tumor suppression. Notably, transfer of CD169⁺ macrophages synergistically enhanced RFA-induced inhibition of distant tumor. To our knowledge, this is the first study which demonstrates hepatic CD169⁺ macrophages as a key factor responsible for RFA-induced abscopal effect. Our data suggest RFA with transfer of CD169⁺ macrophages as a promising combination therapy to lessen metastasis or recurrence of liver cancer in patients.

The roles of tumor-associated macrophages in tumor angiogenesis and metastasis

Tumor associated macrophages (TAMs) are the most frequent immune cells within tumor microenvironment (TME). There is growing evidence that TAMs are involved in tumor progression via multiple mechanisms. TAMs create an immunosuppressive TME by producing growth factors, chemokines, and cytokines which modulate recruitment of immune cells and inhibit anti-tumor responses. They also serve as angiogenesis promoting cells by production of pro-angiogenic factors and matrix metalloproteinases (MMPs) and vascular constructing which guarantee supplying oxygen and nutrients to solid tumor cells. Furthermore, TAMs play important functions in tumor metastasis through contributing to invasion, extravasation, survival, intravasation, and colonization of tumor cells. In this review, we summarized macrophage classification, TAMs polarization, and mechanisms underlying TAM-promoting angiogenesis and metastasis.

Preoperative lymphocyte count in relation to sarcoma prognosis

PURPOSE

Inflammation plays a major role in tumour development, progression and metastasis. Multiple inflammatory markers such as absolute lymphocyte count, neutrophil-lymphocyte ratio (NLR), lymphocyte-monocyte ratio (LMR) and platelet-lymphocyte ratio have been discovered as prognostic markers for various malignancies. We investigate preoperative lymphocyte count and other cell count ratios and their relation to survival and prognosis of sarcoma patients after surgery.

METHODS

A total of 142 patients from the Orthopaedics Oncology Database were included into this retrospective study. Kaplan-Meier curve and multivariate Cox proportional models were used to calculate the overall survival of patients with sarcoma who underwent radical excision surgery.

RESULTS

High preoperative LMR is significantly associated with better overall survival and prognosis in sarcoma patients, whereas high preoperative NLR is significantly associated with shorter overall survival and poorer prognosis. Multivariate analysis shows that LMR and NLR are good predictors for overall survival at 3 and 5 years after surgery, respectively. Patients with high preoperative lymphocytes count are associated with longer overall survival, but this association is not statistically significant. Our findings suggest that preoperative NLR and LMR are good predictive markers for survival of sarcoma patients.

CONCLUSION

LMR and NLR can be used to identify patients at risk for poor clinical outcome, so that a more aggressive course of treatment can be applied to improve outcome. These are cost-effective prognostic tools as they are calculated from routine preoperative peripheral blood counts. In conclusion, preoperative NLR and LMR are good prognostic markers for predicting the clinical outcome of patients with sarcoma.

Potential impact of invasive surgical procedures on primary tumor growth and metastasis

Surgical procedures such as tumor resection and biopsy are still the gold standard for diagnosis and (determination of) treatment of solid tumors, and are prognostically beneficial for patients. However, growing evidence suggests that even a minor surgical trauma can influence several (patho) physiological processes that might promote postoperative metastatic spread and tumor recurrence. Local effects include tumor seeding and a wound healing response that can promote tumor cell migration, proliferation, differentiation, extracellular matrix remodeling, angiogenesis and extravasation. In addition, local and systemic immunosuppression impairs antitumor immunity and contributes to tumor cell survival. Surgical manipulation of the tumor can result in cancer cell release into the circulation, thus increasing the chance of tumor cell dissemination. To prevent these undesired effects of surgical interventions, therapeutic strategies targeting immune response exacerbation or alteration have been proposed. This review summarizes the current literature regarding these local, systemic and secondary site effects of surgical interventions on tumor progression and dissemination, and discusses studies that aimed to identify potential therapeutic approaches to prevent these effects in order to further increase the clinical benefit from surgical procedures.

The role of hepatic macrophages in liver metastasis

The liver is a major target organ for metastasis of both gastrointestinal and extra-gastrointestinal cancers. Due to its frequently inoperable nature, liver metastasis represents a leading cause of cancer-associated death worldwide. In the past years, the pivotal role of the immune system in this process is being increasingly recognised. In particular, the role of the hepatic macrophages, both recruited monocyte-derived macrophages (Mo-Mfs) and tissue-resident Kupffer cells (KCs), has been shown to be more versatile than initially imagined. However, the lack of tools to easily distinguish between these two macrophage populations has hampered the assignment of particular functionalities to specific hepatic macrophage subsets. In this Review, we highlight the most remarkable findings regarding the origin and functions of hepatic macrophage populations, and we provide a detailed description of their distinct roles in the different phases of the liver metastatic process.

Tumor-infiltrating lymphocytes predict prognosis of breast cancer patients treated with anti-Her-2 therapy

PURPOSE

Infiltration of tumor associated lymphocytes and count of its different phenotypes are potentially new independent predictor of prognosis in breast cancer. However, research related to it is less reported in breast cancer patients treated with anti-Her-2 therapy. Thus, we evaluated the relationship between survival and tumor infiltrating lymphocytes including its different phenotypes in tumors of such patients.

METHODS

Between 1999 and 2010, 98 patients diagnosed with primary breast cancer and treated with anti-Her-2 therapy at Sun-Yat-Sen University Cancer Center were included in the study. Biopsy specimens were collected post-operation but before chemotherapy. Tumor infiltrating lymphocytes as well as its FOXP3+, CD68+, IL-17+ phenotypes in both intratumoral and stromal sites and expression of FOXP3 in cancer cells were assessed.

RESULTS

Median follow-up time of 98 patients was 83.3 months (range 7.4-201 months). It suggested that patients with high stromal infiltration of TILs, lower count of FOXP3+ Tregs and CD68+ Mφ in stromal site, and high expression of FOXP3 in cancer cells had longer survival of OS. In multivariate Cox regression analysis, high count of intratumoral CD68+ Mφ [HR: 2.70 (1.00-7.31); p=0.050] and high expression of FOXP3 in cancer cells [HR: 0.29 (0.09-0.91); p=0.034] were independent prognostic factors for overall survival.

CONCLUSIONS

Tumor infiltrating lymphocytes as well as its FOXP3+, CD68+ phenotypes in stromal site, and expression of FOXP3 in cancer cells were significantly associated with OS, suggesting that they can be used as important pathological factor predicting prognosis of breast cancer patients treated with anti-Her-2 therapy.

CD47 Blockade as an Adjuvant Immunotherapy for Resectable Pancreatic Cancer

Purpose: Patients with pancreatic ductal adenocarcinoma (PDAC) who undergo surgical resection and adjuvant chemotherapy have an expected survival of only 2 years due to disease recurrence, frequently in the liver. We investigated the role of liver macrophages in progression of PDAC micrometastases to identify adjuvant treatment strategies that could prolong survival.Experimental Design: A murine splenic injection model of hepatic micrometastatic PDAC was used with five patient-derived PDAC tumors. The impact of liver macrophages on tumor growth was assessed by (i) depleting mouse macrophages in nude mice with liposomal clodronate injection, and (ii) injecting tumor cells into nude versus NOD-scid-gamma mice. Immunohistochemistry and flow cytometry were used to measure CD47 ("don't eat me signal") expression on tumor cells and characterize macrophages in the tumor microenvironment. In vitro engulfment assays and mouse experiments were performed with CD47-blocking antibodies to assess macrophage engulfment of tumor cells, progression of micrometastases in the liver and mouse survival.Results:In vivo clodronate depletion experiments and NOD-scid-gamma mouse experiments demonstrated that liver macrophages suppress the progression of PDAC micrometastases. Five patient-derived PDAC cell lines expressed variable levels of CD47. In in vitro engulfment assays, CD47-blocking antibodies increased the efficiency of PDAC cell clearance by macrophages in a manner which correlated with CD47 receptor surface density. Treatment of mice with CD47-blocking antibodies resulted in increased time-to-progression of metastatic tumors and prolonged survival.Conclusions: These findings suggest that following surgical resection of PDAC, adjuvant immunotherapy with anti-CD47 antibody could lead to substantially improved outcomes for patients. Clin Cancer Res; 24(6); 1415-25. ©2017 AACR.

Single tumor-initiating cells evade immune clearance by recruiting type II macrophages

Guo et al. show that liver tumor-initiating cells (TICs) actively recruit M2 macrophages from as early as the single-cell stage. Elimination of TIC-associated macrophages abolishes tumorigenesis in a manner dependent on the immune system.

Tumor infiltrated type II (M2) macrophages promote tumorigenesis by suppressing immune clearance, promoting proliferation, and stimulating angiogenesis. Interestingly, macrophages were also found to enrich in small foci of altered hepatocytes containing liver tumor-initiating cells (TICs). However, whether and how TICs specifically recruit macrophages and the function of these macrophages in tumor initiation remain unknown due to technical difficulties. In this study, by generating genetically defined liver TICs, we demonstrate that TICs actively recruit M2 macrophages from as early as the single-cell stage. Elimination of TIC-associated macrophages (TICAMs) abolishes tumorigenesis in a manner dependent on the immune system. Mechanistically, activation of the Hippo pathway effector Yes-associated protein (YAP) underlies macrophage recruitment by TICs. These results demonstrate for the first time that macrophages play a decisive role in the survival of single TICs in vivo and provide a proof of principle for TIC elimination by targeting YAP or M2 macrophages.

Pretreatment Lymphocyte Monocyte Ratio Predicts Long-Term Outcomes in Patients with Digestive System Tumor: A Meta-Analysis

Purpose. The prognostic value of pretreatment lymphocyte monocyte ratio (LMR) in digestive system cancer patients remains controversial. The aim of this study was to quantify the prognostic impact of this biomarker and assess its consistency in digestive system tumors. Methods. We searched "PubMed," "Embase," and "CBM" for published eligible studies before June 2016 and conducted a meta-analysis to estimate the pooled hazard ratios (HRs) for disease recurrence and mortality focusing on LMR. Subgroup analyses, meta-regression, and sensitivity analyses were also performed. Results. A total of 22 cohort studies enrolling 12829 patients with digestive system cancer were included. The summary results showed that lower LMR was significantly associated with worse overall survival (OS), cancer-specific survival (CSS), and tumor disease or recurrence-free survival (DFS/RFS) in analyses using the studies reporting HRs either by the univariate analyses (HR = 1.32, HR = 1.35, and HR = 1.26 for OS, CSS, and DFS/RFS, resp.) or by multivariate analyses (HR = 1.21, HR = 1.18, and HR = 1.26 for OS, CSS, and DFS/RFS, resp.). Conclusion. Our results support the fact that decreased LMR indicates worse prognosis in multiple digestive system tumors.

Axl and Mer Receptor Tyrosine Kinases: Distinct and Nonoverlapping Roles in Inflammation and Cancer?

The receptor tyrosine kinases Axl and Mer subserve the process of termination of proinflammatory signaling and have key roles in both the resolution of inflammation and restoration of homeostasis. Axl functions prominently under conditions of tissue stress or in response to infection, whereas Mer has a major role in maintenance of homeostasis within tissues. Distinct patterns of expression of Axl and Mer underlie their clearly defined functional roles during the initiation and progression of inflammation. Axl and Mer are expressed by tumor cells and by infiltrating inflammatory cells and the regulation of cellular function via Axl and Mer signaling is also important for tumorigenesis, tumor progression, and metastasis. In this review, we consider the divergent functions of Axl and Mer in the context of inflammatory processes within tumors and the implications for development of therapeutic agents targeting these receptors.

Protumoral TSP50 Regulates Macrophage Activities and Polarization via Production of TNF-α and IL-1β, and Activation of the NF-κB Signaling Pathway

Testes-specific protease 50 (TSP50) is abnormally overexpressed in many kinds of cancers and promotes cell proliferation and migration. However, whether TSP50 can influence the tumor microenvironment, especially the function of immune cells in the microenvironment, remains largely unknown. We demonstrated that exposure to the conditioned medium from TSP50-overexpressing cells, or co-culture with TSP50-overexpressing cells, enhanced the cytokine production and phagocytic activities of macrophages, and induced M2b polarization. Further investigation showed that production of TNF-α and IL-1β was strongly induced by TSP50 in TSP50-overexpressing cells. TSP50-induced TNF-α and IL-1β were main factors that mediated the effects of TSP50-overexpressing cells on macrophages. The NF-κB pathway could be activated in macrophages upon the treatment of conditioned medium of TSP50-overexpressing cells and its activation is necessary for the observed effects on macrophages. Taken together, our results suggested that oncogenic TSP50 expressed in cells could activate surrounding macrophages and induce M2b polarization, partly through inducing TNF-α/ IL-1β secretion and subsequent NF-κB pathway activation. This implies a potential mechanism by which oncogene TSP50 regulates tumor microenvironment to support tumor development.

Inflammation and uPAR-Expression in Colorectal Liver Metastases in Relation to Growth Pattern and Neo-adjuvant Therapy

Proteolytic activity and inflammation in the tumour microenvironment affects cancer progression. In colorectal cancer (CRC) liver metastases it has been observed that three different immune profiles are present, as well as proteolytic activity, determined by the expression of urokinase-type plasminogen activator (uPAR).The main objectives of this study were to investigate uPAR expression and the density of macrophages (CD68) and T cells (CD3) as markers of inflammation in resected CRC liver metastases, where patients were neo-adjuvantly treated with chemotherapy with or without the angiogenesis inhibitor bevacizumab. Chemonaive patients served as a control group. The markers were correlated to growth patterns (GP) of liver metastases, i.e. desmoplastic, pushing and replacement GP. It was hypothesised that differences in proteolysis and inflammation could reflect tumour specific growth and therapy related changes in the tumour microenvironment. In chemonaive patients, a significantly higher level of uPAR was observed in desmoplastic liver metastases in comparison to pushing GP (p = 0.01) or replacement GP (p = 0.03). A significantly higher density of CD68 was observed in liver metastases with replacement GP in comparison to those with pushing GP (p = 0.01). In liver metastases from chemo treated patients, CD68 density was significantly higher in desmoplastic GP in comparison to pushing GP (p = 0.03). In chemo and bevacizumab treated patients only a significant lower CD3 expression was observed in liver metastases with a mixed GP than in those with desmoplastic (p = 0.01) or pushing GP (p = 0.05). Expression of uPAR and the density of macrophages at the tumour margin of liver metastasis differ between GP in the untreated patients. A higher density of T cells was observed in the bevacizumab treated patients, when desmoplastic and pushing metastases were compared to liver metastases with a mix of the GP respectively, however no specific correlations between the immune markers of macrophages and T cells or GP of liver metastases could be demonstrated.

Kupffer cells decrease metastasis of colon cancer cells to the liver in the early stage

Although Kupffer cells (KCs) play an important role in the liver's immune response, their role in colon cancer metastasis to the liver is unclear. We here analyzed the relationship between KCs and tumor cells (TCs) in colon cancer metastasis to the liver. Fischer 344 (F344) rats were divided into control group (KC+ group) and KC elimination group (KC‑ group), in which KC elimination was induced by Cl2MDP liposome injection. RCN‑H4 colon cancer cells were injected into the rats of both groups, and the relationship between the two types of cells was observed by intravital microscopy (IVM) for 6 h. Moreover, to investigate the effect of KCs on liver metastasis formation, KCs were eliminated at different time points before and after the TC injection. The number of metastatic nodules 2 weeks after the injection was evaluated. In the KC‑ group, IVM revealed that the number of adherent TCs had increased 1.5‑fold at 6 h after the TC injection as compared with in the KC+ group. Moreover, in the KC+ group, 74% of the TCs adhered to the KCs, and KC activation and KC phagocytosis of the TCs were observed. Two weeks after the injection, the number of metastatic nodules was significantly increased in rats in which the KCs had been eliminated before the injection, but not in rats in which the KCs had been eliminated after the injection. KC activation and KC phagocytosis of TCs decreased colon cancer cell metastasis to the liver.

Targeting tumor-infiltrating macrophages to combat cancer

Tumor-associated macrophages are one of the major constituents of tumor stroma in many solid tumors and there is compelling preclinical and clinical evidence that macrophages promote cancer initiation and malignant progression. Therefore, these cells represent potential targets for therapeutic benefit. In this review, we will summarize macrophage phenotypic heterogeneity, the current understanding of how tumors take advantage of macrophage plasticity to generate immunosuppression, and how manipulation of specific macrophage populations can be used for therapeutic purposes through translational approaches.

Macrophage polarization in inflammatory diseases

Diversity and plasticity are two hallmarks of macrophages. M1 macrophages (classically activated macrophages) are pro-inflammatory and have a central role in host defense against infection, while M2 macrophages (alternatively activated macrophages) are associated with responses to anti-inflammatory reactions and tissue remodeling, and they represent two terminals of the full spectrum of macrophage activation. Transformation of different phenotypes of macrophages regulates the initiation, development, and cessation of inflammatory diseases. Here we reviewed the characters and functions of macrophage polarization in infection, atherosclerosis, obesity, tumor, asthma, and sepsis, and proposed that targeting macrophage polarization and skewing their phenotype to adapt to the microenvironment might hold great promise for the treatment of inflammatory diseases.

Isolation and culture of hepatic stellate cells from mouse liver

Hepatic stellate cells (HSCs) are the primary extracellular matrix-producing cells within the liver and have numerous vital functions. A robust protocol for the isolation and culture of HSCs is important for further investigations of cell functions and related mechanisms in liver disease. The volume of the mouse liver is much smaller than that of the rat liver, which makes it much more difficult to isolate mouse HSCs (mHSCs) than rat HSCs. At present, isolating mHSCs is still a challenge because there is no efficient, robust method to isolate and culture these cells. In the present study, C57BL/6J mice were intravenously injected with liposome-encapsulated dichloromethylene diphosphate (CL2MDP) to selectively eliminate Kupffer cells from the liver. The mouse livers were then perfused in situ, and the mHSCs were isolated with an optimized density gradient centrifugation technique. In the phosphate buffer solution (PBS)-liposome group, the yield of mHSCs was (1.37 ± 0.23) × 10(6)/g liver, the cell purity was (90.18 ± 1.61)%, and the cell survival rate was (94.51 ± 1.61)%. While in the CL2MDP-liposome group, the yield of mHSCs was (1.62 ± 0.34) × 10(6)/g liver, the cell purity was (94.44 ± 1.89)%, and the cell survival rate was (94.41 ± 1.50)%. Based on the yield and purity of mHSCs, the CL2MDP-liposome treatment was superior to the PBS-liposome treatment (P < 0.05, P < 0.01). This study established successfully a robust and efficient protocol for the separation and purification of mHSCs, and both a high purity and an adequate yield of mHSCs were obtained.

The preoperative lymphocyte to monocyte ratio predicts clinical outcome in patients with stage III colon cancer

BACKGROUND

Inflammation has a critical role in the pathogenesis and progression of cancer. The lymphocyte to monocyte ratio (LMR) could be shown to be prognostic in haematologic neoplasia. In this study, we analysed the LMR with clinical outcome in stage II and III colon cancer patients.

METHODS

Three hundred and seventy-two patients with stage II and III colon cancer were included in this retrospective study. Kaplan-Meier curves and multivariate Cox-regression analyses were calculated for time to recurrence (TTR) and overall survival (OS).

RESULTS

Including all patients, the elevated preoperative LMR was significantly associated with increased TTR and OS in multivariate analysis (HR: 0.47, 95%CI: 0.29-0.76, P=0.002; HR: 0.51, 95%CI: 0.31-0.83, P=0.007; respectively). In subanalyses, the association was limited to patients with stage III (HR: 0.40, 95%CI: 0.22-0.72, P=0.002), in contrast to patients with stage II (HR: 0.40, 95%CI: 0.28-1.66, P=0.397). When the subgroup of patients with 'high-risk' LMR≤2.83 was analysed, no benefit of adjuvant 5-FU-based chemotherapy could be found (HR: 0.99; 95%CI: 0.60-1.63; P=0.953).

CONCLUSION

The LMR might be an independent prognostic marker for TTR in stage III colon cancer patients. Our results further suggest that high-risk patients based on the LMR do not benefit from adjuvant chemotherapy. Independent validation of our findings is warranted.

Screening for transcription factors and their regulatory small molecules involved in regulating the functions of CL1-5 cancer cells under the effects of macrophage-conditioned medium

Many reports have inferred that macrophages can interact with tumor cells in the tumor microenvironment (TME) in a vicious cycle of tumor development; however, the changes in gene expression in tumor cells under the effects of macrophages are still largely unknown. The present study was carried out to illustrate the changes in the gene expression profile in lung cancer cells under the effects of macrophage-conditioned medium. Gene expression profile data were derived from the GEO database GSE9315. The GSM234968 sample was derived from a highly invasive human pulmonary adenocarcinoma cell line, CL1-5, and was treated with conditioned medium (supernatant of a culture solution of human monocyte THP-1). The GSM234967 sample that was not treated with the conditioned medium was used as a control. GO and KEGG enrichment analyses were carried out using DAVID software, and visualization networks were constructed using Cytoscape software. The results showed that 40 differentially expressed genes were annotated. Five differentially expressed transcription factors were identified, EIF2B4, EIF2B5, JUNB, GNG11 and HMGB2, which were all related to 'stress' and 'responses'. The gene cluster of JUNB was mainly enriched in cancer-related pathways, 'Wnt signaling pathway' and 'MAPK signaling pathway'. Finally, 10 small molecules, thioridazine, resveratrol, astemizole, ciclopirox, calmidazolium, etoposide, anisomycin, pyrvinium, azacyclonol and terfenadine, which may act on transcription factors, were identified using the CMap database. In conclusion, we identified transcription factors playing key roles in tumor cells under the effects of macrophages in order to provide new clues for blocking this vicious cycle of tumor development.

Macrophages promote tumour growth and liver metastasis in an orthotopic syngeneic mouse model of colon cancer

PURPOSE

Tumour-associated macrophages have been shown to promote proliferation, angiogenesis and metastasis in several carcinomas. The effect on colon cancer has not yet been clarified. Furthermore, Kupffer cells in the liver might initiate the formation of metastases by directly binding tumour cells.

METHODS

An orthotopic syngeneic mouse model of colon cancer as well as a liver metastases model has been studied, using murine CT-26 colon cancer cells in Balb/c-mice. Macrophages were depleted in both models by clodronate liposomes. Tumour sizes and metastases were determined using 7-Tesla MRI. The macrophage and vascular density in the orthotopic tumours as well as the Kupffer cell density in the livers were evaluated using immunohistochemistry.

RESULTS

Animals in the macrophage-depleted group displayed significantly smaller primary tumours (37 ± 20 mm(3)) compared to the control group (683 ± 389 mm(3), p = 0.0072). None of the mice in the depleted group showed liver or peritoneal metastases, whereas four of six control mice displayed liver and five out of six mice peritoneal metastases. The vascular density was significantly lower in the macrophage-depleted group (p = 0.0043). In the liver metastases model, animals of the Kupffer cell-depleted group (14.3 ± 7.7) showed significantly less liver metastases than mice of the two control groups (PBS liposomes, 118.5 ± 28.2, p = 0.0117; NaCl, 81.7 ± 23.2, p = 0.0266). The number of liver metastases correlated directly with the Kupffer cell density (p = 0.0221).

CONCLUSION

Macrophages promote tumour growth, angiogenesis and metastases in this orthotopic syngeneic mouse model. Kupffer cells enhance the formation of metastases in the liver.

The renin angiotensin system regulates Kupffer cells in colorectal liver metastases

Blockade of the renin angiotensin system (RAS) can inhibit tumor growth and this may be mediated via undefined immunomodulatory actions. This study investigated the effects of RAS blockade on liver macrophages (Kupffer cells; KCs) in an orthotopic murine model of colorectal cancer (CRC) liver metastases. Here we showed that pharmacological targeting of the RAS [ANG II (31.25 µg/kg/h i.p.), ANG-(1-7) (24 µg/kg/h i.p.) or the ACE inhibitor; captopril (750 mg/kg/d i.p.)] altered endogenous KC numbers in the tumor-bearing liver throughout metastatic growth. Captopril, and to a lesser extent ANG-(1-7), increased KC numbers in the liver but not tumor. KCs were found to express the key RAS components: ACE and AT1R. Treatment with captopril and ANG II increased the number of AT1R-expressing KCs, although total KC numbers were not affected by ANG II. Captopril (0.1 µM) also increased macrophage invasion in vitro. Additionally, captopril was administered with KC depletion before tumor induction (day 0) or at established metastatic growth (day 18) using gadolinium chloride (GdCl 3; 20 mg/kg). Livers were collected at day 21 and quantitative stereology used as a measure of tumor burden. Captopril reduced growth of CRC liver metastases. However, when captopril was combined with early KC depletion (day 0) tumor growth was significantly increased compared with captopril alone. In contrast, late KC depletion (day 18) failed to influence the anti-tumor effects of captopril. The result of these studies suggests that manipulation of the RAS can alter KC numbers and may subsequently influence progression of CRC liver metastases.

Bimodal role of Kupffer cells during colorectal cancer liver metastasis

Kupffer cells (KCs) are resident liver macrophages that play a crucial role in liver homeostasis and in the pathogenesis of liver disease. Evidence suggests KCs have both stimulatory and inhibitory functions during tumor development but the extent of these functions remains to be defined. Using KC depletion studies in an orthotopic murine model of colorectal cancer (CRC) liver metastases we demonstrated the bimodal role of KCs in determining tumor growth. KC depletion with gadolinium chloride before tumor induction was associated with an increased tumor burden during the exponential growth phase. In contrast, KC depletion at the late stage of tumor growth (day 18) decreased liver tumor load compared with non-depleted animals. This suggests KCs exhibit an early inhibitory and a later stimulatory effect. These two opposing functions were associated with changes in iNOS and VEGF expression as well as T-cell infiltration. KC depletion at day 18 increased numbers of CD3 (+) T cells and iNOS-expressing infiltrating cells in the tumor, but decreased the number of VEGF-expressing infiltrating cells. These alterations may be responsible for the observed reduction in tumor burden following depletion of pro-tumor KCs at the late stage of metastatic growth. Taken together, our results indicate that the bimodal role of KC activity in liver tumors may provide the key to timing immunomodulatory intervention for the treatment of CRC liver metastases.

Bisphosphonates and cancer: what opportunities from nanotechnology?

Bisphosphonates (BPs) are synthetic analogues of naturally occurring pyrophosphate compounds. They are used in clinical practice to inhibit bone resorption in bone metastases, osteoporosis, and Paget's disease. BPs induce apoptosis because they can be metabolically incorporated into nonhydrolyzable analogues of adenosine triphosphate. In addition, the nitrogen-containing BPs (N-BPs), second-generation BPs, act by inhibiting farnesyl diphosphate (FPP) synthase, a key enzyme of the mevalonate pathway. These molecules are able to induce apoptosis of a number of cancer cells in vitro. Moreover, antiangiogenic effect of BPs has also been reported. However, despite these promising properties, BPs rapidly accumulate into the bone, thus hampering their use to treat extraskeletal tumors. Nanotechnologies can represent an opportunity to limit BP accumulation into the bone, thus increasing drug level in extraskeletal sites of the body. Thus, nanocarriers encapsulating BPs can be used to target macrophages, to reduce angiogenesis, and to directly kill cancer cell. Moreover, nanocarriers can be conjugated with BPs to specifically deliver anticancer agent to bone tumors. This paper describes, in the first part, the state-of-art on the BPs, and, in the following part, the main studies in which nanotechnologies have been proposed to investigate new indications for BPs in cancer therapy.

Peri-operative bowel perforation in early stage colon cancer is associated with an adverse oncological outcome

BACKGROUND

The presence of an inflammatory response resulting from bowel perforation or anastomotic leakage has been suggested to enhance recurrence rates in colorectal cancer patients. Currently, it is unknown if bowel perforation or anastomotic leakage has prognostic significance in early stage colon cancer patients. In this study, the impact of peri-operative bowel perforation including anastomotic leakage on disease-free survival of stage I/II colon cancer patients was investigated.

METHODS

Prospective follow up data of 448 patients with stages I/II colon cancer that underwent resection were included. Patients who died within 3 months after initial surgery were excluded.

RESULTS

Median follow up was 56.0 months. Patients with peri-operative bowel perforation (n = 25) had a higher recurrence rate compared to patients without perforation (n = 423), 36.0 % vs. 16.1 % (p = 0.01). Disease-free survival was significantly worse for the perforation group compared to patients without perforation (p = 0.004). Multivariate analysis including T-stage, histological grade, and adjuvant chemotherapy showed peri-operative bowel perforation to be an independent factor significantly associated with disease recurrence (odds ratio, 2.7; 95 % CI, 1.1-6.7).

CONCLUSION

Peri-operative bowel perforation is associated with increased recurrence rates and impaired disease-free survival in early-stage colon cancer patients.

Transition of tumor-associated macrophages from MHC class II(hi) to MHC class II(low) mediates tumor progression in mice

Background

Tumor-associated macrophages (TAMs) are the most abundant immune cells within the tumor stroma and play a crucial role in tumor development. Although clinical investigations indicate that high levels of macrophage (MΦ) infiltration into tumors are associated with a poor prognosis, the exact role played by TAMs during tumor development remains unclear. The present study aimed to investigate dynamic changes in TAM major histocompatibility complex (MHC) class II expression levels and to assess the effects of these changes on tumor progression.

Results

Significant inhibition of tumor growth in the murine hepatocellular carcinoma Hepa1-6 model was closely associated with partial TAM depletion. Strikingly, two distinct TAM subsets were found to coexist within the tumor microenvironment during Hepa1-6 tumor development. An MHC class II^hi TAM population appeared during the early phase of tumor development and was associated with tumor suppression; however, an MHC class II^low TAM population became increasingly predominant as the tumor progressed.

Conclusions

Tumor progression was positively correlated with increasing infiltration of the tumor tissues by MHC class II^low TAMs. Thus, targeting the transition of MΦ may be a novel strategy for drug development and immunotherapy.

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.

Macrophage diversity enhances tumor progression and metastasis

There is persuasive clinical and experimental evidence that macrophages promote cancer initiation and malignant progression. During tumor initiation, they create an inflammatory environment that is mutagenic and promotes growth. As tumors progress to malignancy, macrophages stimulate angiogenesis, enhance tumor cell migration and invasion, and suppress antitumor immunity. At metastatic sites, macrophages prepare the target tissue for arrival of tumor cells, and then a different subpopulation of macrophages promotes tumor cell extravasation, survival, and subsequent growth. Specialized subpopulations of macrophages may represent important new therapeutic targets.

Inflammatory disease and cancer with a decrease in Kupffer cell numbers in Nucling-knockout mice

Nucling is a stress-inducible protein associated with apoptosomes. The cytochrome c-triggered formation of apoptosomes represents a key-initiating event in apoptosis. We have recently reported that Nucling regulates the apoptotic pathway by controlling the activation of NF-kappaB as well. Here we show that hepatocellular carcinoma (HCC) arising spontaneously against a background of hepatitis occurred more frequently in Nucling-knockout (KO) mice than wild-type (WT) mice. Biochemical serum testing revealed potential liver dysfunction with hypercholesterolemia in Nucling-KO males. In the background of Nucling-KO mice, we observed the up-regulation of TNFalpha, spontaneous NF-kappaB-activation and the induction of galectin-3 expression in liver. In addition, we observed a decrease in the number of Kupffer cells (KCs) in the KO mice. KCs are important for the hepatic immune system, acting as phagocytes or antigen-presenting cells (APCs). We found that KCs in Nucling-KO mice were apoptotic possibly through the up-regulation of TNFalpha. These observations indicate that Nucling is important for the regulation of NF-kappaB signals in liver. We propose that Nucling deficiency could be a powerful tool to reveal the NF-kappaB-related molecular networks leading to hepatitis and HCC development.

Role of Kupffer cells in the outgrowth of colorectal cancer liver metastases

Colorectal cancer is one of the commonest malignancies in the "developed" world. The liver constitutes the main host organ for its distant metastases which, when present, augur a bad prognosis for the disease. Kupffer cells (KCs) are macrophages that constantly reside within the liver and form an effective first line defence against multiple harmful agents which reach the hepatic sinusoids via the portal circulation. KCs remove chemical compounds and dead or damaged cells, eliminate bacteria and protect against invading tumour cells. They may play a crucial tumouricidal role, exerting cytotoxic and cytostatic functions through the release of multiple cytokines and chemokines. Subsequently, colorectal metastasising cells are destroyed either by KC-performed phagocytosis or via the stimulation of other immune cells which migrate into the sinusoids and act accordingly. On the contrary, KC products, including cytokines, growth factors and matrix-degrading enzymes may promote liver metastasis, supporting tumour cell extravasation, motility and invasion. Current research aims to exploit the antineoplastic properties of KCs in new therapeutic approaches of colorectal cancer liver metastasis. Numerous agents, such as the granulocyte macrophage-colony stimulating factor, interferon gamma, muramyl peptide analogues and various antibody based treatments, have been tested in experimental models with promising results. Future trials may investigate their use in everyday clinical practice and compare their therapeutic value with current treatment of the disease.

High tumor-infiltrating macrophage density predicts poor prognosis in patients with primary hepatocellular carcinoma after resection

Macrophages constitute a major component of the leukocyte infiltrate of tumors and perform distinct roles in different tumor microenvironments. This study attempted to investigate the prognostic values of tumor-infiltrating macrophages in patients with hepatocellular carcinoma after resection, paying particular attention to their tissue microlocalization. The CD68(+) macrophages were assessed by immunohistochemistry in tissues from 137 patients with hepatocellular carcinoma. Prognostic value of intratumoral, marginal, and peritumoral macrophage densities was evaluated by Kaplan-Meier analysis and Cox regression. Both intratumoral and marginal macrophage densities were associated inversely with overall survival (P = .034 and .004, respectively) and disease-free survival (P = .006 and .008, respectively). In contrast, peritumoral macrophage density was associated with neither overall survival nor disease-free survival. Intratumoral macrophage density emerged as an independent prognosticator of overall survival (hazard ratio = 1.721, P = .049) and disease-free survival (hazard ratio = 2.165, P = .007). Marginal macrophage density, but not intratumoral macrophage density, was associated with vascular invasion, tumor multiplicity, and fibrous capsule formation. Our results demonstrate that high macrophage infiltration predicts poor prognosis in patients with hepatocellular carcinoma. These results, together with our previous report showing the distinct activation patterns of macrophages in different areas of tumor tissue, implies that macrophages in those areas may use different strategies to promote the tumor progression.

The renin-angiotensin system and malignancy

The renin-angiotensin system (RAS) is usually associated with its systemic action on cardiovascular homoeostasis. However, recent studies suggest that at a local tissue level, the RAS influences tumour growth. The potential of the RAS as a target for cancer treatment and the suggested underlying mechanisms of its paracrine effects are reviewed here. These include modulation of angiogenesis, cellular proliferation, immune responses and extracellular matrix formation. Knowledge of the RAS has increased dramatically in recent years with the discovery of new enzymes, peptides and feedback mechanisms. The local RAS appears to influence tumour growth and metastases and there is evidence of tissue- and tumour-specific differences. Recent experimental studies provide strong evidence that drugs that inhibit the RAS have the potential to reduce cancer risk or retard tumour growth and metastases. Manipulation of the RAS may, therefore, provide a safe and inexpensive anticancer strategy.

Animal models for liver metastases of colorectal cancer: research review of preclinical studies in rodents

Liver metastases of colorectal carcinoma occur in about 50-60% of patients. To improve survival of these patients, there is an urgent need for new treatment strategies. For this purpose, the availability of a preclinical model to develop and test such treatments is mandatory. An ideal animal model for studying liver metastases of colorectal origin should mimic all aspects of the metastatic development in humans and be practical, predictable, and optimal in terms of ethical considerations. Thus far, no model has been developed which satisfies all these conditions. As a consequence, choosing an animal model for the study of liver metastases requires compromises and choices about the necessary characteristics that depend on the purpose of the intended experiments. This overview addresses the advantages and disadvantages of different animal models used for research on experimental liver metastases of colorectal origin. Based on data available in literature, we conclude that heterotopic injection of undifferentiated syngeneic tumor cells in immunocompetent rodents covers most of the desired characteristics. Both subcapsular as well as intraportal injection will yield suitable models and the eventual choice will depend on the aim of the study.

Use of bioluminescence imaging to detect enhanced hepatic and systemic tumor growth following partial hepatectomy in mice

BACKGROUND

The impact of partial hepatectomy on intra-hepatic and distant tumor growth is a matter of controversy. Utilizing a highly sensitive tumor imaging strategy, we sought to demonstrate whether this growth-acceleration occurs, and to develop an animal model with which to investigate potential therapeutic strategies.

METHODS

Mice bearing constitutively-active luciferase-expressing tumor cells were subjected to either 70% partial hepatectomy (PH; n=10) or a sham operation (n=11). Mice were sacrificed 14 days later and remnant livers (or anatomic equivalents in the control group) and lungs harvested for bioluminescence detection.

RESULTS

Remnant liver weights were significantly increased in PH compared to equivalent lobes in sham-operated animals (t-test; p=0.005). Tumor burden as measured by bioluminescence was significantly higher in both liver and lung specimens in the PH group (Wilcoxon's Rank Sum test; p=0.01 and 0.004, respectively).

CONCLUSIONS

Following PH, enhanced metastatic growth was depicted regionally and systemically with bioluminescence imaging providing an objective measure of tumor burden. This preclinical model can help to identify adjuvant therapies that can influence both tumor growth and liver regeneration.

Enhanced tumour growth and impaired cellular antitumoural defense in hepatic colorectal carcinoma metastasis in rats after laparoscopy compared to open surgery

BACKGROUND

This study aims to assess postoperative hepatic growth of colorectal adenocarcinoma metastasis and peritumoural macrophage counts after laparoscopy in an experimental animal model.

METHODS

Thirty male syngenic WAG/Rij rats were randomised into two surgical groups: laparoscopy (LS; n = 15) using CO(2) at 12 mmHg and laparotomy (LT; n = 15; negative control) during an operating time of 90 min. At 45 min after setup, CC531s colon adenocarcinoma cells were injected into two liver lobes. Postoperative tumour volumes were determined by abdominal magnetic resonance imaging (MRI) and computed three-dimensional volumetry. Peritumoural macrophages were counted by local stereology using a confocal laser-scanning fluorescence microscope.

RESULTS

The median postoperative tumour volume was significantly higher after LS in both lobes (L): after 10, 15 and 20 days in L2 and L5: 24/12, 54/38, 275/62 mm(3) and 0/0, 15/11, 55/24 mm(3) (LS/LT). Significantly fewer peritumoural macrophages were found after LS at all postoperative time points (Mann-Whitney: p < 0.05).

CONCLUSIONS

Increased hepatic growth of colorectal adenocarcinoma metastasis and impaired cellular antitumoural defence after LS cast doubt on the use of LS in colorectal cancer and needs further clinical investigation.

Transporters, enzymes, and enalapril removal in a rat (CC531-induced) liver metastatic model

Temporal changes in physiological spaces, protein expression of transporters and enzymes, and enalapril removal were appraised in the metastatic liver tumor model developed from male Wag/Rij rats after the intraportal injection of CC531 colon adenocarcinoma cells; sham-operated preparations received PBS. Liver tissue spaces, investigated with multiple indicator dilution technique in liver perfusion studies, were unchanged at week 3 after tumor induction. At week 4, however, the sinusoidal blood volume and albumin Disse space in tumor-bearing livers were slightly lower compared with those of shams. Increased levels of the canalicular ATP transporters, P-glycoprotein, multidrug resistance-associated protein 2 (Mrp2), and bile salt export pump (Bsep) at week 2 (P < 0.05), unchanged levels of Ntcp, Oatp1a1, Oatp1a4, and Mct2, but decreased levels of cytochrome P450 3a2 (Cyp3a2) and glutathione S-transferase (Gst4-4) at week 4 (P < 0.05) were observed in peritumor vs. sham-operated liver tissues with Western blotting. The steady-state extraction ratio of enalapril, a substrate that enters the liver rapidly via Oatp1a1 and primarily undergoes metabolism by the carboxylesterases, was unaffected by liver metastasis at week 4 regardless of its delivery via the portal vein or hepatic artery into the perfused liver preparations.

Phagocytosis of ultrasound contrast agent microbubbles by Kupffer cells

Delayed parenchymal phase images of the liver more than 5 min after IV injection of ultrasound contrast agents are thought to be related to the phagocytosis of contrast agent microbubbles by macrophages. In this study, we examined whether liver-specific macrophages, Kupffer cells, phagocytosed the microbubbles and whether their elimination affected the delayed parenchymal images of the liver. Phase-contrast microscope observations showed that Kupffer cells phagocytosed various contrast agents in vitro. Among the contrast agents used, 99% of Sonazoid and Optison, and 47% of Levovist were phagocytosed, whereas only 7.3% of SonoVue and 0% of Imavist were phagocytosed. Elimination of Kupffer cells in vivo by gadolinium chloride (GdCl(3)) resulted in decreased intensity of the delayed parenchymal images with Sonazoid and Levovist, while SonoVue showed no changes compared with control. Our findings suggested that Kupffer cells phagocytosed contrast agents and they were responsible for the delayed images of contrast ultrasound in the liver.

Role of Kupffer cells in the pathogenesis of liver disease

Kupffer cells, the resident liver macrophages have long been considered as mostly scavenger cells responsible for removing particulate material from the portal circulation. However, evidence derived mostly from animal models, indicates that Kupffer cells may be implicated in the pathogenesis of various liver diseases including viral hepatitis, steatohepatitis, alcoholic liver disease, intrahepatic cholestasis, activation or rejection of the liver during liver transplantation and liver fibrosis. There is accumulating evidence, reviewed in this paper, suggesting that Kupffer cells may act both as effector cells in the destruction of hepatocytes by producing harmful soluble mediators as well as antigen presenting cells during viral infections of the liver. Moreover they may represent a significant source of chemoattractant molecules for cytotoxic CD8 and regulatory T cells. Their role in fibrosis is well established as they are one of the main sources of TGFβ1 production, which leads to the transformation of stellate cells into myofibroblasts. Whether all these variable functions in the liver are mediated by different Kupffer cell subpopulations remains to be evaluated. In this review we propose a model that demonstrates the role of Kupffer cells in the pathogenesis of liver disease.

Role of Kupffer cells in host defense and liver disease

Kupffer cells (KC) constitute 80-90% of the tissue macrophages present in the body. They reside within the lumen of the liver sinusoids, and are therefore constantly exposed to gut-derived bacteria, microbial debris and bacterial endotoxins, known to activate macrophages. Upon activation KC release various products, including cytokines, prostanoides, nitric oxide and reactive oxygen species. These factors regulate the phenotype of KC themselves, and the phenotypes of neighboring cells, such as hepatocytes, stellate cells, endothelial cells and other immune cells that traffic through the liver. Therefore, KC are intimately involved in the liver's response to infection, toxins, ischemia, resection and other stresses. This review summarizes established basic concepts of KC function as well as their role in the pathogenesis of various liver diseases.

Preoperative granulocyte/macrophage colony-stimulating factor (GM-CSF) increases hepatic dendritic cell numbers and clustering with lymphocytes in colorectal cancer patients

Despite surgery with curative intent, approximately 30% of colorectal carcinoma patients will develop liver metastases during follow-up. Synchronous occult micrometastases, tumor cell shedding into the portal circulation and postoperative immune impairment have all been suggested to facilitate outgrowth of liver metastases. In experimental models, increases in both number of resident macrophages of the liver, the so-called Kupffer cells (KC), and tumoricidal capacity of KC were observed after pretreatment with granulocyte/macrophage colony-stimulating factor (GM-CSF), a potent immuno-stimulatory agent. Following perioperative recombinant human GM-CSF (rhGM-CSF), we previously showed activation of the systemic immune response in the postoperative period, which is normally transiently down-modulated after surgery. Therefore, in this pilot study, effects of preoperative rhGM-CSF administration on the composition of human liver immune cell population were evaluated in patients undergoing surgery for colorectal cancer. No difference in KC numbers of rhGM-CSF-treated patients was observed. Importantly, however, a 6-fold increase in dendritic cell (DC) numbers was observed compared to control patients, as quantified by immunohistochemistry of liver biopsies, taken during laparotomy. Furthermore, direct contact between liver CD8+ cells and DC was significantly enhanced in rhGM-CSF-treated patients. Both increases in DC numbers and DC interaction with CD8+ T cells suggest enhanced immunological activation, which may reduce liver metastases formation and ultimately improve survival after initial colorectal surgery.

Kupffer cells abrogate cholestatic liver injury in mice

BACKGROUND & AIMS

Biliary obstruction and cholestasis can cause hepatocellular apoptosis and necrosis. Ligation of the common bile duct in mice provides an excellent model in which to study the underlying mechanisms. Kupffer cells play a key role in modulating the inflammatory response observed in most animal models of liver injury. This study was performed to determine the role of Kupffer cells in the injury attending cholestasis.

METHODS

Mice were not treated or were rendered Kupffer cell-depleted by intravenous inoculation of multilamellar liposome-encapsulated dichloromethylene diphosphonate, the common bile duct was ligated and divided; sham-operated animals served as controls. Similarly, interleukin-6 (IL-6)-deficient and tumor necrosis factor-receptor-deficient mice underwent bile duct ligation (BDL) or sham operations.

RESULTS

Serum alanine transaminase levels were increased in all BDL mice at 3 days after surgery, but were significantly higher in IL-6-deficient mice or mice rendered Kupffer cell-depleted before ligation. Histologic examination of BDL livers showed portal inflammation, neutrophil infiltration, bile duct proliferation, and hepatocellular necrosis. Photoimage analyses confirmed more necrosis in the livers of Kupffer cell-depleted and IL-6-deficient animals. Purified Kupffer cells derived from BDL animals produced more IL-6 in culture. Similarly, Kupffer cells obtained by laser capture microdissection from the livers of BDL mice expressed increased levels of IL-6 messenger RNA. Recombinant mouse IL-6 administered 1 hour before BDL completely reversed the increased liver damage assessed otherwise in Kupffer cell-depleted mice.

CONCLUSIONS

These findings indicate that Kupffer cells abrogate cholestatic liver injury by cytokine-dependent mechanisms that include the production of IL-6.

Macrophages direct tumour histology and clinical outcome in a colon cancer model

Macrophages generally constitute a major component of the tumour stroma. Although conventionally considered to be cytotoxic effector cells, macrophages have recently been described as promoters of tumour progression. The present study shows that selective depletion of peritoneal or liver macrophages prior to CC531 tumour cell inoculation resulted in highly differentiated tumours in rats. In contrast, tumours from control rats, in which macrophages are abundantly present, showed a desmoplastic stromal reaction with hallmark features of malignancy, such as neovascularization and matrix remodelling, indicating that the presence of macrophages is associated with malignant histopathological differentiation. Remarkably, macrophage-depleted rats, bearing highly differentiated tumours, had a worse prognosis, as they displayed a higher tumour load and poorer survival. Thus, while macrophages direct tumours towards malignant tumour histology, their role in anti-tumour defence is important. The selective inhibition of macrophage functions involved in malignant progression without interfering with cytotoxic ability may therefore identify important new targets for cancer therapy.

Therapeutic potential of Kupffer cells in prevention of liver metastases outgrowth

Development of liver metastases is a frequent complication in the course of gastro-intestinal malignancies. After entering the liver via the portal circulation, blood-borne tumor cells that have been seeded from primary colorectal cancer, are first encountered by Kupffer cells (KC), which line the liver sinusoids. KC represent approximately 10% of all liver cells, and have the ability to kill tumor cells. As such, they may play an important intrinsic role in the protection against outgrowth of hepatic metastases. Furthermore, the cytotoxic function of KC is increased upon stimulation with various biological response modifiers, such as interferon-gamma, granulocyte macrophage-colony stimulating factor, antibodies and muramyl dipeptides. Therefore, enhancement of KC cytotoxic functions may represent an attractive treatment modality to prevent development of liver metastases in the clinical setting.

Mechanisms of Focal Heat Destruction of Liver Tumors

BACKGROUND

Focal heat destruction has emerged as an effective treatment strategy in selected patients with malignant liver tumors. Radiofrequency ablation, interstitial laser thermotherapy, and microwave treatment are currently the most widely applied thermal ablative techniques. A major limitation of these therapies is incomplete tumor destruction and overall high recurrences. An understanding of the mechanisms of tissue injury induced by focal hyperthermia is essential to ensure more complete tumor destruction. Here, the currently available scientific literature concerning the underlying mechanisms involved in the destruction of liver tumors by focal hyperthermia is reviewed.

METHODS

Medline was searched from 1960 to 2004 for literature regarding the use of focal hyperthermia for the treatment of liver tumors. All relevant literature was searched for further references.

RESULTS

Experimental evidence suggests that focal hyperthermic injury occurs in two distinct phases. The first phase results in direct heat injury that is determined by the total thermal energy applied, tumor biology, and the tumor microenvironment. Tumors are more susceptible to heat injury than normal cells as the result of specific biological features, reduced heat dissipating ability, and lower interstitial pH. The second phase of hyperthermic injury is indirect tissue damage that produces a progression of tissue injury after the cessation of the initial heat stimulus. This progressive injury may involve a balance of several factors, including apoptosis, microvascular damage, ischemia-reperfusion injury, Kupffer cell activation, altered cytokine expression, and alterations in the immune response. Blood flow modulation and administration of thermosensitizing agents are two methods currently used to increase the extent of direct thermal injury. The processes involved in the progression of thermal injury and therapies that may potentially modulate them remain poorly understood.

CONCLUSION

Focal hyperthermia for the treatment of liver tumors involves complex mechanisms. Evidence suggests that focal hyperthermia produces both direct and indirect tissue injury by differing underlying processes. Methods to enhance the effects of treatment to achieve complete tumor destruction should focus on manipulating these processes.

Interactions between rat colon carcinoma cells and Kupffer cells during the onset of hepatic metastasis

Liver sinusoids harbor populations of 2 important types of immunocompetent cells, Kupffer cells (KCs) and natural killer (NK) cells, which are thought to play an important role in controlling hepatic metastasis in the first 24 hr upon arrival of the tumor cells in the liver. We studied the early interaction of KCs, NK and CC531s colon carcinoma cells in a syngeneic rat model by confocal laser scanning microscopy. Results showed a minority of KCs (19% periportal and 7% pericentral) involved in the interaction with 94% of tumor cells and effecting the phagocytosis of 92% of them. NK cell depletion decreased the phagocytosis of tumor cells by KCs by 33% over a period of 24 hr, leaving 35% of the cancer cells free, as compared to 6% in NK-positive rats. Surviving cancer cells were primarily located close to the Glisson capsule, suggesting that metastasis would initiate from this region.

Rat colon carcinoma cells that survived systemic immune surveillance are less sensitive to NK-cell mediated apoptosis

In order to form distant metastases, cells from the primary tumor have to detach, enter the blood- or lymph-compartment and escape immune surveillance. Here, we describe the selection of rat colon carcinoma cell lines (CC531s-m1 and CC531s-m2) that escaped from systemic immune surveillance; CC531s cells were injected into the v. jugularis of Wag/Rij rats, after three weeks the lung tumors were isolated, the tumor cells were cultured, characterized and injected again. The m1- and m2-cell lines were less susceptible for killing by syngeneic NK cells. Further characterization of this cell line showed a decreased sensitivity towards TRAIL- and CD95L-, but not to granzyme B-mediated apoptosis. In the m1- and m2-cells log-phase growth started earlier as compared to the parental cell line, whereas no changes were found in anchorage-dependent or anchorage-independent growth. After subcapsular injection of the m2-cell line into the liver of rats much more lung metastases were formed in comparison to injection of the parental cell line. In conclusion, the results suggest that the resistance of the m1- and m2-cells to NK cell-mediated apoptosis was associated with their capability to survive systemic immune surveillance and form metastases in vivo.