Recognition and destruction of neoplastic cells by activated macrophages: discrimination of altered self

Calculus bovis inhibits M2 tumor-associated macrophage polarization via Wnt/β-catenin pathway modulation to suppress liver cancer

BACKGROUND

Calculus bovis (CB), used in traditional Chinese medicine, exhibits anti-tumor effects in various cancer models. It also constitutes an integral component of a compound formulation known as Pien Tze Huang, which is indicated for the treatment of liver cancer. However, its impact on the liver cancer tumor microenvironment, particularly on tumor-associated macrophages (TAMs), is not well understood.

AIM

To elucidate the anti-liver cancer effect of CB by inhibiting M2-TAM polarization via Wnt/β-catenin pathway modulation.

METHODS

This study identified the active components of CB using UPLC-Q-TOF-MS, evaluated its anti-neoplastic effects in a nude mouse model, and elucidated the underlying mechanisms via network pharmacology, transcriptomics, and molecular docking. In vitro assays were used to investigate the effects of CB-containing serum on HepG2 cells and M2-TAMs, and Wnt pathway modulation was validated by real-time reverse transcriptase-polymerase chain reaction and Western blot analysis.

RESULTS

This study identified 22 active components in CB, 11 of which were detected in the bloodstream. Preclinical investigations have demonstrated the ability of CB to effectively inhibit liver tumor growth. An integrated approach employing network pharmacology, transcriptomics, and molecular docking implicated the Wnt signaling pathway as a target of the antineoplastic activity of CB by suppressing M2-TAM polarization. In vitro and in vivo experiments further confirmed that CB significantly hinders M2-TAM polarization and suppresses Wnt/β-catenin pathway activation. The inhibitory effect of CB on M2-TAMs was reversed when treated with the Wnt agonist SKL2001, confirming its pathway specificity.

CONCLUSION

This study demonstrated that CB mediates inhibition of M2-TAM polarization through the Wnt/β-catenin pathway, contributing to the suppression of liver cancer growth.

Roles of macrophages in tumor development: a spatiotemporal perspective

Macrophages are critical regulators of tissue homeostasis but are also abundant in the tumor microenvironment (TME). In both primary tumors and metastases, such tumor-associated macrophages (TAMs) seem to support tumor development. While we know that TAMs are the dominant immune cells in the TME, their vast heterogeneity and associated functions are only just being unraveled. In this review, we outline the various known TAM populations found thus far and delineate their specialized roles associated with the main stages of cancer progression. We discuss how macrophages may prime the premetastatic niche to enable the growth of a metastasis and then how subsequent metastasis-associated macrophages can support secondary tumor growth. Finally, we speculate on the challenges that remain to be overcome in TAM research.

The effects of prolactin on the immune system, its relationship with the severity of COVID-19, and its potential immunomodulatory therapeutic effect

Prolactin (PRL) is an endocrine hormone secreted by the anterior pituitary gland that has a variety of physiological effects, including milk production, immune system regulation, and anti-inflammatory effects. Elevated levels of PRL have been found in several viral infections, including 2019 coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), a viral pathogen that has recently spread worldwide. PRL production is increased in SARS-CoV2 infection. While PRL can trigger the production of proinflammatory cytokines, it also has several anti-inflammatory effects that can reduce hyperinflammation. The exact mechanism of PRL's contribution to the severity of COVID-19 is unknown. The purpose of this review is to discuss the interaction between PRL and SARS-CoV2 infection and its possible association with the severity of COVID-19.

Bringing Macrophages to the Frontline against Cancer: Current Immunotherapies Targeting Macrophages

Macrophages are found in all tissues and display outstanding functional diversity. From embryo to birth and throughout adult life, they play critical roles in development, homeostasis, tissue repair, immunity, and, importantly, in the control of cancer growth. In this review, we will briefly detail the multi-functional, protumoral, and antitumoral roles of macrophages in the tumor microenvironment. Our objective is to focus on the ever-growing therapeutic opportunities, with promising preclinical and clinical results developed in recent years, to modulate the contribution of macrophages in oncologic diseases. While the majority of cancer immunotherapies target T cells, we believe that macrophages have a promising therapeutic potential as tumoricidal effectors and in mobilizing their surroundings towards antitumor immunity to efficiently limit cancer progression.

Current Perspectives on Therapies, Including Drug Delivery Systems, for Managing Glioblastoma Multiforme

Glioblastoma multiforme (GBM), a standout among the most dangerous class of central nervous system (CNS) cancer, is most common and is an aggressive malignant brain tumor in adults. In spite of developments in modality therapy, it remains mostly incurable. Consequently, the need for novel systems, strategies, or therapeutic approaches for enhancing the assortment of active agents meant for GBM becomes an important criterion. Currently, cancer research focuses mainly on improving the treatment of GBM via diverse novel drug delivery systems. The treatment options at diagnosis are multimodal and include radiation therapy. Moreover, significant advances in understanding the molecular pathology of GBM and associated cell signaling pathways have opened opportunities for new therapies. Innovative treatment such as immunotherapy also gives hope for enhanced survival. The objective of this work was to collect and report the recent research findings to manage GBM. The present review includes existing novel drug delivery systems and therapies intended for managing GBM. Reported novel drug delivery systems and diverse therapies seem to be precise, secure, and relatively effective, which could lead to a new track for the obliteration of GBM.

Inflammation-based prognostic scores in patients with extrahepatic bile duct lesions treated by percutaneous transhepatic biliary stenting combined with 125I seeds intracavitary irradiation

PURPOSE

This study aimed at investigating the efficacy of percutaneous transhepatic biliary stenting (PTBS) combined with ¹²⁵I seeds intracavitary irradiation in the treatment of extrahepatic cholangiocarcinoma (EHC) and to preliminarily explore the prognostic values of inflammation-based scores in these patients.

METHODS

A total of 113 clinically/pathologically diagnosed cases of EHC who received PTBS combined with ¹²⁵I seeds implantation were retrospectively analyzed. The postoperative changes of clinical symptoms and serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total serum bilirubin (TBIL), direct bilirubin (DBIL), and albumin (ALB) were observed. Preoperative clinical data were extracted to calculate inflammation-based scores, including systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), and platelets-to-lymphocyte ratio (PLR). Kaplan-Meier survival curves and Cox regression analyses were used to evaluate the prognostic significance of inflammation-based scores.

RESULTS

After operation, clinical symptoms such as jaundice and fever significantly improved in all patients. At 1 month and 3 months postoperatively, serum levels of ALT, AST, ALP, TBIL, and DBIL significantly reduced, and ALB significantly increased, compared with preoperative values. The median survival time of the patients was 12 months and the 1-year survival rate was 56.8%. Univariate analysis revealed that factors related to overall survival were CA19-9, TBIL, ALB, SII, and NLR. Multivariate analysis further identified SII and NLR as independent prognostic models.

CONCLUSION

The combination of PTBS and ¹²⁵I seeds intracavitary irradiation is an effective palliative treatment for advanced EHC. Elevated SII and NLR can be used to predict poor survival.

Targeting macrophages: therapeutic approaches in cancer

Infiltration of macrophages in solid tumours is associated with poor prognosis and correlates with chemotherapy resistance in most cancers. In mouse models of cancer, macrophages promote cancer initiation and malignant progression by stimulating angiogenesis, increasing tumour cell migration, invasion and intravasation and suppressing antitumour immunity. At metastatic sites, macrophages promote tumour cell extravasation, survival and subsequent growth. Each of these pro-tumoural activities is promoted by a subpopulation of macrophages that express canonical markers but have unique transcriptional profiles, which makes tumour-associated macrophages (TAMs) good targets for anticancer therapy in humans through either their ablation or their re-differentiation away from pro-tumoural towards antitumoural states. In this Review, we evaluate the state of the art of TAM-targeting strategies, focusing on the limitations and potential side effects of the different therapies such as toxicity, rebound effects and compensatory mechanisms. We provide an extensive overview of the different types of therapy used in the clinic and their limitations in light of known macrophage biology and propose new strategies for targeting TAMs.

Discovering Macrophage Functions Using In Vivo Optical Imaging Techniques

Macrophages are an important component of host defense and inflammation and play a pivotal role in immune regulation, tissue remodeling, and metabolic regulation. Since macrophages are ubiquitous in human bodies and have versatile physiological functions, they are involved in virtually every disease, including cancer, diabetes, multiple sclerosis, and atherosclerosis. Molecular biological and histological methods have provided critical information on macrophage biology. However, many in vivo dynamic behaviors of macrophages are poorly understood and yet to be discovered. A better understanding of macrophage functions and dynamics in pathogenesis will open new opportunities for better diagnosis, prognostic assessment, and therapeutic intervention. In this article, we will review the advances in macrophage tracking and analysis with in vivo optical imaging in the context of different diseases. Moreover, this review will cover the challenges and solutions for optical imaging techniques during macrophage intravital imaging.

Infrared spectroscopic characterization of monocytic microvesicles (microparticles) released upon lipopolysaccharide stimulation

Microvesicles (MVs) are involved in cell-cell interactions, including disease pathogenesis. Nondestructive Fourier-transform infrared (FTIR) spectra from MVs were assessed as a technique to provide new biochemical insights into a LPS-induced monocyte model of septic shock. FTIR spectroscopy provided a quick method to investigate relative differences in biomolecular content of different MV populations that was complementary to traditional semiquantitative omics approaches, with which it is difficult to provide information on relative changes between classes (proteins, lipids, nucleic acids, carbohydrates) or protein conformations. Time-dependent changes were detected in biomolecular contents of MVs and in the monocytes from which they were released. Differences in phosphatidylcholine and phosphatidylserine contents were observed in MVs released under stimulation, and higher relative concentrations of RNA and α-helical structured proteins were present in stimulated MVs compared with MVs from resting cells. FTIR spectra of stimulated monocytes displayed changes that were consistent with those observed in the corresponding MVs they released. LPS-stimulated monocytes had reduced concentrations of nucleic acids, α-helical structured proteins, and phosphatidylcholine compared with resting monocytes but had an increase in total lipids. FTIR spectra of MV biomolecular content will be important in shedding new light on the mechanisms of MVs and the different roles they play in physiology and disease pathogenesis.-Lee, J., Wen, B., Carter, E. A., Combes, V., Grau, G. E. R., Lay, P. A. Infrared spectroscopic characterization of monocytic microvesicles (microparticles) released upon lipopolysaccharide stimulation.

Preoperative lymphocyte-to-monocyte ratio predicts survival in primary hepatitis B virus-positive hepatocellular carcinoma after curative resection

Background

Both inflammation and immunity are associated with the development of malignancy. The lymphocyte-to-monocyte ratio (LMR) has been confirmed as a prognostic factor for several malignant diseases. The purpose of our study was to analyze prognostic significance of preoperative LMR in hepatitis B virus (HBV)-related hepatocellular carcinoma after curative resection.

Patients and methods

A total of 253 patients with primary HBV-positive hepatocellular carcinoma who underwent a curative operation were enrolled in this retrospective study. The relationship between preoperative LMR and survival outcomes was analyzed through Kaplan–Meier curves and multivariate Cox regression analyses.

Results

Patients with a high LMR had a significantly higher mean overall survival than those with a low LMR (67 months vs 55 months, P=0.023), and high LMR remained significant for longer survival in the multivariate analysis (hazard ratio, 0.147; 95% confidence interval [CI]: 0.085–0.253; P=0.021). Furthermore, patients with a high LMR also had a higher median recurrence-free survival than those with a low LMR in univariate analyses (60 months vs 48 months, P=0.026) and multivariate analyses (hazard ratio, 0.317; 95% CI: 0.042–1.023; P=0.032). However, the survival benefit was limited to patients with advanced cancer.

Conclusion

LMR was confirmed as an independent prognostic biomarker for primary HBV-positive hepatocellular carcinoma after curative resection.

Prognostic value of inflammation-based markers in patients with recurrent malignant obstructive jaundice treated by reimplantation of biliary metal stents: A retrospective observational study

We aimed to assess the therapeutic effect of reimplantation of biliary metal stents by percutaneous transhepatic cholangial drainage (PTCD) in patients with recurrent malignant obstructive jaundice (MOJ). Furthermore, we explored the prognostic value of inflammation-based markers in these patients.We reviewed 33 cases of recurrent MOJ after implantation of biliary metal stents by PTCD, all of which underwent reimplantation of stents under digital subtraction angiography guidance. Levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin were compared between before and after reimplantation (1 week, 1 month, and 3 months postoperatively). Preoperative clinical data were collected to calculate the inflammation-based markers, including systemic immune-inflammation index (SII, neutrophil × platelets/ lymphocyte), platelets-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), and monocyte-to-lymphocyte ratio (MLR). The primary outcome was overall survival (OS), which was estimated by the Kaplan-Meier method and Cox regression analysis.The levels of ALT, AST, total bilirubin, and direct bilirubin significantly reduced after the reimplantation operation. During a median follow-up time of 10 months, 18 (54.5%) patients died. Gender, albumin, SII, PLR, NLR, and MLR were found to be associated with OS by the log-rank test and univariate analysis. Multivariate Cox analysis identified elevated levels of SII and PLR as significant factors for predicting poor OS.Reimplantation is clinically feasible in patients with recurrent MOJ after implantation of biliary metal stents. SII and PLR are independent, useful inflammation-based prognostic models for predicting outcomes in these patients.

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.

Prognostic value of preoperative lymphocyte-to-monocyte ratio in pancreatic adenocarcinoma

BACKGROUND

Inflammation and immunity have an important role in the development of cancer. The lymphocyte-to-monocyte ratio (LMR) has been shown to be of prognostic value in several malignant forms. The purpose of this study was to analyze the prognostic significance of preoperative LMR in post-curative resection of pancreatic adenocarcinoma.

METHODS

A total of 144 patients with primary pancreatic adenocarcinoma who underwent curative operation were enrolled in this retrospective study. The correlation between preoperative LMR and survival was analyzed using Kaplan-Meier curves and multivariate Cox regression analyses.

RESULTS

In the univariate analysis, an elevated preoperative LMR was significantly associated with an increased overall survival (OS) (19 months vs 12 months, P=0.000), and this result remained significant in the multivariate analysis (hazard ratio [HR]: 0.148; 95% confidence interval [CI]: 0.085-0.252; P=0.000). Furthermore, patients with high LMR also had higher median recurrence-free survival (RFS) than patients with low LMR in univariate (18 months vs 10 months, P=0.000) and multivariate analyses (HR: 0.148; 95% CI: 0.085-0.252; P=0.000). Subgroup analyses showed that both patients with stage III cancer and patients with stage I+II cancer can obtain OS and RFS benefits from high LMR.

CONCLUSION

LMR can be considered as an independent prognostic biomarker for operable pancreatic adenocarcinoma.

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.

Innate immune cells in breast cancer--from villains to heroes?

The innate immune system ensures effective protection against foreign pathogens and plays important roles in tissue remodeling. There are many types of innate immune cells, including monocytes, macrophages, dendritic cells, and granulocytes. Interestingly, these cells accumulate in most solid tumors, including those of the breast. There, they play a tumor-promoting role through secretion of growth and angiogenic factors, as well as immunosuppressive molecules. This is in strong contrast to the tumor-suppressing effects that innate immune cells exert in vitro upon proper activation. Therapeutic approaches have been developed with the aim of achieving similar suppressive activities in vivo. However, multiple factors in the tumor microenvironment, many of which are immunosuppressive, represent a major obstacle to effective treatment. Here, we discuss the potential of combating breast cancer through activation of the innate immune system, including possible strategies to enhance the success of immunotherapy.

Inhibitory effect of vitamin D-binding protein-derived macrophage activating factor on DMBA-induced hamster cheek pouch carcinogenesis and its derived carcinoma cell line

This study investigated the inhibitory effect of vitamin D-binding protein-derived macrophage-activating factor (GcMAF) on carcinogenesis and tumor growth, using a 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced hamster cheek pouch carcinogenesis model, as well as the cytocidal effect of activated macrophages against HCPC-1, a cell line established from DMBA-induced cheek pouch carcinoma. DMBA application induced squamous cell carcinoma in all 15 hamsters of the control group at approximately 10 weeks, and all 15 hamsters died of tumor burden within 20 weeks. By contrast, 2 out of the 14 hamsters with GcMAF administration did not develop tumors and the remaining 12 hamsters showed a significant delay of tumor development for approximately 3.5 weeks. The growth of tumors formed was significantly suppressed and none of the hamsters died within the 20 weeks during which they were observed. When GcMAF administration was stopped at the 13th week of the experiment in 4 out of the 14 hamsters in the GcMAF-treated group, tumor growth was promoted, but none of the mice died within the 20-week period. On the other hand, when GcMAF administration was commenced after the 13th week in 5 out of the 15 hamsters in the control group, tumor growth was slightly suppressed and all 15 hamsters died of tumor burden. However, the mean survival time was significantly extended. GcMAF treatment activated peritoneal macrophages in vitro and in vivo, and these activated macrophages exhibited a marked cytocidal effect on HCPC-1 cells. Furthermore, the cytocidal effect of activated macrophages was enhanced by the addition of tumor-bearing hamster serum. These findings indicated that GcMAF possesses an inhibitory effect on tumor development and growth in a DMBA-induced hamster cheek pouch carcinogenesis model.

Inhibition of aldose reductase prevents colon cancer metastasis

Colon cancer is the third most common cause of cancer and is the second leading cause of cancer deaths in the USA. Although inhibition of aldose reductase (AR) is known to prevent human colon cancer cell growth in nude mice xenografts, the role of AR in the regulation of cancer metastasis is not known. We now demonstrate the mechanisms by which AR regulates colon cancer metastasis in vitro and in vivo. Inhibition of AR prevented the epidermal growth factor (EGF) or fibroblast growth factor (FGF)-induced migration and invasion of human colon cancer (HT29; KM20) cells by >70% and also inhibited (>80%) the adhesion of the cancer cells to endothelial cells. Treatment of endothelial cells with AR inhibitors significantly (∼85%) downregulated the EGF or FGF-induced expression of Inter-Cellular Adhesion Molecule-1, Vascular cell adhesion molecule-1 and vascular endothelial-cadherin. Furthermore, liver metastasis of green fluorescent protein-labeled KM20 cells injected into the spleen of athymic nude mice was significantly (>65%) prevented by AR inhibitor, fidarestat or ARsiRNA delivered systemically into the mice. Similar results were observed with HT29 cells. AR inhibition or ablation also prevented (70-90%) the increase in the levels of matrix metalloproteinase-2, cyclin D1, CD31, CD34 and the activation of nuclear factor-kappa-binding protein in metastatic liver. Thus, our results indicate that AR regulates cancer cell adhesion, invasion and migration events which initiate metastasis and therefore, AR inhibition could be a novel therapeutic approach for the prevention of colon cancer metastasis.

Nitric oxide-mediated tumoricidal activity of murine microglial cells

Experimental metastases in the brain of mice are infiltrated by microglia, and parabiosis experiments of green fluorescent protein (GFP(+)) and GFP(-) mice revealed that these microglia are derived from circulating monocytes (GFP(+), F4/80(+), and CD68(+)). These findings raised the question as to whether microglia (specialized macrophages) possess tumoricidal activity. C8-B4 murine microglia cells were incubated in vitro in medium (control) or in medium containing both lipopolysaccharide and interferon-γ. Control microglia were not tumoricidal against a number of murine and human tumor cells, whereas lipopolysaccharide/interferon-γ-activated microglia lysed murine and human tumor cells by release of nitric oxide. Parallel experiments with murine peritoneal macrophages produced identical results. Neither activated microglia nor activated macrophages lysed nontumorigenic murine or human cells. Collectively, these data demonstrate that brain metastasis-associated microglia are derived from circulating mononuclear cells and exhibit selective and specific tumoricidal activity.

Environmental control of invasiveness and metastatic dissemination of tumor cells: the role of tumor cell-host cell interactions

Recent advances in tumor biology led to the realization that, in order to understand the mechanisms involved in proliferation and invasion of tumor cells, an analysis of the complex interactions that tumor cells establish with host cells of tumor microenvironment is required. The bidirectional interactions between tumor cells and components of tumor microenvironment, in particular endothelial cells, cells of monocyte/macrophage lineage and fibroblasts/myofibroblasts, play a critical role in most of the events that characterize tumor progression and metastasis. Interactions between these "reactive" normal cells and the genetically altered tumor cells, by either cell-to-cell contacts or soluble mediators, control the most aspects of tumor formation and progression. This review addresses some of the experimental evidences documenting that tumor cells may influence host cells of their own microenvironment by triggering changes that facilitate their local as well as distant dissemination. Therefore, it focuses on macrophages and fibroblasts that, upon stimulation by tumor cells, change their state towards a tumor-promoting-like phenotype.

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.

Immunological tolerance and tumor rejection in embryo-aggregated chimeric mice - lessons for tumor immunity

Background

Rejection of transplanted tumors by the immune system is a rare event in syngeneic hosts, and is considered to be dependent on the local interaction of defensive immune reactions and tumor tolerance mechanisms. Here, we have enlisted the aid of a unique set of embryo-aggregated lineage chimeric mice derived from C57/BL6 and FVB donors to study the interplay between local and systemic tumor immunity and tolerance in rejection of mouse B16 melanoma cells, syngeneic to the C57/BL6 donor strain.

Methods

Two variants of embryo-aggregated chimeric mice with either variable or no contribution of C57-derived cells to their skin were generated by the fusion of different ratios of morula stage blastomers. Chimeric mice were analyzed for s.c. growth of B16 tumors in comparison to their respective donor strains as well as normal F1 hybrids, and the relative frequencies of cellular components of the immune system by FACS analysis of peripheral blood or lymph node cells.

Results

B16 tumors grew significantly faster in mice with full chimerism in their skin as compared to syngeneic C57 or semi-syngeneic C57 × FVB F1 hosts. In contrast, s.c. tumor growth was either absent or significantly reduced in chimeric mice lacking C57-derived cells in their skin, but tolerant to C57 tissue in other organs. Comparison of the relative frequencies of various immune cells in the periphery via FACS-analysis did not reveal any significant differences between the two types of chimeric mice with respect to their donor strains.

Conclusion

Our data suggest a complex interplay between mechanisms of local peripheral tolerance and innate antitumor mechanisms possibly involving NK cell allorecognition as a basis for the differential growth or rejection of B16 tumors in these unique chimeric mice, which we suggest to constitute a valuable new model system for the study of immune-mediated tumor rejection.

Tumoral and macrophage uPAR and MMP-9 contribute to the invasiveness of B16 murine melanoma cells

The aim of this study was to investigate whether tumor cells as well as tumor-associated macrophages (TAMs) contribute to the generation of protease activities essential to tumor cell invasiveness, such as matrix metalloproteinase 2 and 9 (MMP-2 and MMP-9), and the urokinase-type plasminogen activator (uPA) and uPA receptor (uPAR). We found that the enhanced invasiveness through Matrigel-coated filters of B16 murine melanoma cells stimulated with IFNgamma was associated with an higher expression of uPAR and MMP-9 in these cells. Moreover, treatment with anti-MMP-9 or anti-uPAR monoclonal antibodies abrogated the increase of invasiveness in IFNgamma-stimulated melanoma cells, suggesting a cooperation of uPA system and MMP-9 in cytokine-stimulated invasiveness. Invasiveness through Matrigel was also enhanced in B16 melanoma cells exposed to a medium conditioned by TAMs, represented in our experimental model by thioglycollate-elicited macrophages co-cultivated with melanoma cells. Macrophages isolated from these co-cultures were found to express higher levels of uPAR and MMP-9 compared to macrophage cultures alone, and the pro-invasive activity of the co-culture-conditioned medium was abrogated by anti-MMP-9 monoclonal antibodies, but not anti-uPAR monoclonal antibodies. Furthermore, the enhanced uPAR and MMP-9 expression in macrophages co-cultivated with tumor cells seems a rather specific phenomenon, generated through a cell-to-cell contact mechanism. On the whole, our data point to a cooperation between tumor cells and macrophages elicited by tumor cells themselves in generating key enzymes essential in the promotion of tumor invasiveness, such as uPAR and MMP-9.

Tuftsin augments antitumor efficacy of liposomized etoposide against fibrosarcoma in Swiss albino mice

Anticancer drugs are generally plagued by toxic manifestations at doses necessary for control of various forms of cancer. Incorporating such drugs into liposomes not only reduces toxicity but also enhances the therapeutic index. Some antioxidants and potent immunomodulators have also been shown to impart significant antitumor activity presumably by nonspecific activation of the host immune system. In the present study, we evaluated augmentation of the antitumor activity of etoposide (ETP) by the immunomodulator tuftsin in Swiss albino mice with fibrosarcoma. The efficacies of the free form of ETP, liposomized ETP (Lip-ETP), and tuftsin-bearing liposomized ETP (Tuft-Lip-ETP) formulations were evaluated on the basis of tumor regression, effect on expression level of p53wt and p53mut, and survival of the treated animals. Tuft-Lip-ETP, when administered at a dosage of 10 mg/kg body weight/day for five days, significantly reduced tumor volume, delayed tumor growth, and also up-regulated the expression of p53wt. In contrast, although Lip-ETP delayed tumor growth, it did not decrease tumor size. The results of the present study suggest that tuftsin incorporation in drug-loaded liposomes is a promising treatment strategy for various forms of cancers, including fibrosarcoma.

Tuftsin augments antitumor efficacy of liposomized etoposide against fibrosarcoma in Swiss albino mice

Anticancer drugs are generally plagued by toxic manifestations at doses necessary for control of various forms of cancer. Incorporating such drugs into liposomes not only reduces toxicity but also enhances the therapeutic index. Some antioxidants and potent immunomodulators have also been shown to impart significant antitumor activity presumably by nonspecific activation of the host immune system. In the present study, we evaluated augmentation of the antitumor activity of etoposide (ETP) by the immunomodulator tuftsin in Swiss albino mice with fibrosarcoma. The efficacies of the free form of ETP, liposomized ETP (Lip-ETP), and tuftsin-bearing liposomized ETP (Tuft-Lip-ETP) formulations were evaluated on the basis of tumor regression, effect on expression level of p53wt and p53mut, and survival of the treated animals. Tuft-Lip-ETP, when administered at a dosage of 10 mg/kg body weight/day for five days, significantly reduced tumor volume, delayed tumor growth, and also up-regulated the expression of p53wt. In contrast, although Lip-ETP delayed tumor growth, it did not decrease tumor size. The results of the present study suggest that tuftsin incorporation in drug-loaded liposomes is a promising treatment strategy for various forms of cancers, including fibrosarcoma.

Enhancement of nitric oxide release in mouse inflammatory macrophages co-cultivated with tumor cells of a different origin

In the present study we investigated whether synthesis of nitric oxide (NO) by macrophages is affected by contact with tumor cells. Although it is well known that NO generated by macrophages influences different activities related to tumor progression, there is limited information on the modulatory role of tumor cells on NO release by macrophages. The experimental protocol used in our study consisted in the determination of NO secreted by macrophages, either resident or inflammatory, co-cultivated with tumor cells (B16 melanoma and L929 fibrosarcoma cells) at different cell densities and macrophage:tumor cell ratios. This experimental in vitro protocol simulates the different interactions between macrophages and tumor cells that occur during the development of a tumor mass. We found that the co-cultivation with tumor cells induced an increased secretion of NO in macrophages provided that they express an inflammatory phenotype, and they were challenged with LPS or IFNgamma/LPS. Two more variables were found to be critical in the increase of NO generation in inflammatory macrophages cultivated with tumor cells: a high cell density and a prevalence of tumor cells over macrophages. The enhancement of NO secreted in inflammatory macrophages stimulated by tumor cells was not observed in normal murine fibroblasts co-cultivated with tumor cells.

Distribution of tumor-infiltrating dendritic cells in human non-small cell lung carcinoma in relation to apoptosis

Host defense mechanisms play important roles in suppressing the development and growth of tumors. It is known that S-100 protein-positive immature dendritic cells (S100DC), as antigen presenting cells (APC), and macrophages have roles in the immune responses to tumor growth. Mediators such as nitric oxide are also important in the surveillance against cancer. We examined the distribution of S100DC and CD68-positive macrophages (CD68MØ) immunohistochemically to compare the condition of apoptotic tumor cells in 69 patients with human non-small cell lung carcinoma. The expression of inducible nitric oxide synthases (iNOS) in tumors was also studied. Unlike macrophages, S100DC were distributed predominantly in cancer nests. In the areas with infiltration of 'many' S100DC (i.e. more than 10 DC/HPF), we found two distinct patterns of tumor infiltration: scattered and aggregated infiltration of DC in tumor nests. In areas of scattered S100DC distribution, only a few apoptotic tumor cells could be detected. However, in the areas of DC aggregations, apoptotic tumor cells were significantly more abundant (P = 0.0491). In contrast to S100DC, the distribution and density of CD68MØ were associated with iNOS expression of tumor cells (P < 0.0001), but not with distribution of apoptotic tumor cells. These findings reveal differences in the in vivo condition between S100DC and CD68MØ in tumors, and suggest there is a relationship between tumor-infiltrating S100DC aggregation and apoptosis in in vivo non-small cell lung cancers.

GnT-V, macrophage and cancer metastasis: a common link

GnT-V generated, beta1,6-branched polylactosamines are a common feature shared by normal granulocytes, monocytes, and a variety of malignant cells. Furthermore, activation of GnT-V in oncogenic transformation induces invasiveness and metastatic potential in mice as well as in humans. In view of the common expression of lymphocytic/monocytic trait, motility, and GnT-V by metastatic cancer cells, macrophage fusion hybrids were generated in vitro with Cloudman S91 mouse melanoma cells to test whether the parental traits are co-expressed in hybrids and how those are related to altered phenotypes in relation to metastasis. In fact, the fusion hybrids are highly metastatic in vivo, motile in vitro, and express macrophage-associated traits of increased GnT-V activity, beta1,6 branching, and polylactosamine content. A Spontaneously formed lung melanoma metastases have been identified and characterized as host x tumor hybrid containing higher DNA content than parental cells and increased GnT-V activity. The results, taken together, could reflect prior fusion of tumor-associated macrophages with cells of the primary tumor, and therefore establish a possible common link between elevated expression of GnT-V and malignant transformation, a well-known report. Moreover, the fusion hybrids with metastatic potential ranging from high to low offer a genetically matched model system, for identification and characterization of differentially expressed genes in association with metastasis, since the fusion partners are derived from the same species of mouse (DBA/2J).

Cells as vehicles for cancer gene therapy: the missing link between targeted vectors and systemic delivery?

Systemic administration of currently manufactured viral stocks has not so far achieved sufficient circulating titers to allow therapeutic targeting of metastatic disease. This is due to low initial viral titers, immune inactivation, nonspecific adhesion, and loss of particles. One way to exploit the elegant molecular manipulations that have been made to increase vector targeting is to protect these vectors until they reach the local sites of tumor growth. Various cell types home preferentially to tumors and can be loaded with the constructs required to produce targeted vectors. Here we discuss the potential of using such cell carriers to chaperone precious vectors directly to the tumors. The vectors can incorporate mechanisms to achieve tumor site-inducible expression, along with tumor cell-specific expression of the therapeutic gene and/or replicating viral genomes that would be released at the tumor. In this way, the great advances that have so far been made with the engineering of vector tropisms might be genuinely exploited and converted into clinical benefit.

Monocyte chemoattractant protein-1-induced activation of p42/44 MAPK and c-Jun in murine peritoneal macrophages: a potential pathway for macrophage activation

The role of monocyte chemoattractant protein-1 (MCP-1) in mediating the infiltration and activation of monocytes/macrophages into the sites of inflammation or tumor growth is well documented, but the molecular mechanism(s) involved in the process is poorly understood. In the current investigation, we demonstrate activation of the p42/44 MAPK-mediated signal transduction in murine peritoneal macrophages on stimulation with MCP-1 (10-100 ng/ml) in vitro. The p42/44 MAPK activation was determined by studying the expression of the phosphorylated p42/44 MAPK (Thr202/Tyr204) in the MCP-1-treated macrophages. This response was found to be rapid and time dependent, detectable within 5 min of MCP-1 stimulation. PD98058 (5-50 microM), a specific inhibitor of MAPK kinase (MEK) inhibited the p42/44 MAPK phosphorylation, indicating the specificity of the response. Furthermore, the MCP-1-induced phosphorylation of p42/44 MAPK was found to be blocked by pertussis toxin (100 ng/ml), tyrosine kinase inhibitor-genestein (10 ng/ml), PI3K inhibitor-wortmannin (20-200 microM), and anti-CCR2 antibody (2.5 microg/ml). Additionally, phosphorylation of JNK and activation of the transcription factor, c-Jun, were also noted in response to MCP-1 treatment. Lastly, the MCP1-induced p42/44 MAPK activity was correlated with the functional activation of macrophages by demonstrating the dose-specific inhibition of actin polymerization, macrophage-mediated tumor cell cytotoxicity, and tumor necrosis factor-alpha (TNF-alpha) transcription/production afforded by PD98059 in the MCP-1-treated macrophages. Taken together, these data suggest the involvement of the p42/44 MAPK/c-Jun pathway in the signal transduction process, leading to activation of murine peritoneal macrophages.

Effects of niosomal cisplatin and combination of the same with theophylline and with activated macrophages in murine B16F10 melanoma model

The use of cisplatin is limited due to its certain toxic effects. In the present study niosomes of cisplatin by using span 60 and cholesterol were prepared and investigated for antimetastatic activity in experimental metastatic model of B16F10 melanoma. Theophylline and its combination effect with free cisplatin and niosomal cisplatin were also carried out in the same model. The effect of treatment with activated macrophages alone and in combination with cisplatin, theophylline and niosomal cisplatin was also observed. Treatment with niosomal cisplatin (1 mg/kg) and combination of the same with theophylline (15 mg/kg) showed significant reduction in the number of lung nodules as compared to untreated control as well as with free cisplatin (1 mg/kg). The treatment with activated macrophages (activated by using Muramyl dipeptide) significantly reduced the secondary growth of tumor in lung. Niosomal cisplatin showed a significant protection against weight loss and bone marrow toxicity as compared to free cisplatin. These results suggest that cisplatin encapsulated in niosomes has significant antimetastatic activity and reduced toxicities than that of free cisplatin. However theophylline failed to show antimetastatic effect alone or in combination with cisplatin or with activated macrophages.

Heparin and cancer revisited: mechanistic connections involving platelets, P-selectin, carcinoma mucins, and tumor metastasis

Independent studies indicate that expression of sialylated fucosylated mucins by human carcinomas portends a poor prognosis because of enhanced metastatic spread of tumor cells, that carcinoma metastasis in mice is facilitated by formation of tumor cell complexes with blood platelets, and that metastasis can be attenuated by a background of P-selectin deficiency or by treatment with heparin. The effects of heparin are not primarily due to its anticoagulant action. Other explanations have been suggested but not proven. Here, we bring together all these unexplained and seemingly disparate observations, showing that heparin treatment attenuates tumor metastasis in mice by inhibiting P-selectin-mediated interactions of platelets with carcinoma cell-surface mucin ligands. Selective removal of tumor mucin P-selectin ligands, a single heparin dose, or a background of P-selectin deficiency each reduces tumor cell-platelet interactions in vitro and in vivo. Although each of these maneuvers reduced the in vivo interactions for only a few hours, all markedly reduce long-term organ colonization by tumor cells. Three-dimensional reconstructions by using volume-rendering software show that each situation interferes with formation of the platelet "cloak" around tumor cells while permitting an increased interaction of monocytes (macrophage precursors) with the malignant cells. Finally, we show that human P-selectin is even more sensitive to heparin than mouse P-selectin, giving significant inhibition at concentrations that are in the clinically acceptable range. We suggest that heparin therapy for metastasis prevention in humans be revisited, with these mechanistic paradigms in mind.

Biological properties associated with the enhanced lung-colonizing potential in a B16 murine melanoma line grown in a medium conditioned by syngeneic Corynebacterium parvum-elicited macrophages

A previous study by our laboratory showed that the peritoneal murine Corynebacterium parnum-elicited macrophages released into their growth medium an activity which enhanced the ability of B16-F10 melanoma cells to form experimental metastases in the lung of syngeneic mice. In the present study, we used a clone of B16-F10 line (F10-M3 cells) to investigate whether the increase in lung-colonizing potential due to the pro-clonogenic activity released by C. parvum-elicited macrophages was associated with biological properties characteristic of a metastatic phenotype. We have found that the pulmonary retention, growth rate in lung parenchyma, invasiveness through Matrigel, adhesiveness to IL-1-activated endothelium and MHC class I expression were increased in F10-M3 cells stimulated by the macrophage pro-clonogenic activity. By using an in vitro experimental protocol, the enhancement of lung-colonizing potential in the stimulated melanoma cells turned out to be a transient phenomenon as was the increase of invasiveness through Matrigel and the higher expression of MHC class I antigens. In conclusion, the melanoma cells stimulated by the pro-clonogenic activity released by C. parvum-elicited macrophages showed changes in biological parameters which are relevant to metastatic diffusion. These changes appeared as a temporary phenomenon which sustains the view that the metastatic phenotype represents a transient biological character influenced by host factors.

Cutting Edge: Differential Effect of Apoptotic Versus Necrotic Tumor Cells on Macrophage Antitumor Activities

Macrophages (Mφ) play essential roles both in tumor defense and normal tissue homeostasis by removal of transformed as well as damaged and disintegrating cells. Whereas tissue necrosis is known to provoke inflammatory responses, removal of apoptotic cells has been assumed to be immunologically inert. We now show that while Mφ exposure to necrotized tumor cells causes pronounced stimulation of Mφ antitumor activity, exposure of Mφ to apoptotic tumor cells in contrast results in impairment of Mφ-mediated tumor defense and even support of tumor cell growth. Given the fact that apoptosis is a consequence of various cancer treatment modalities, this may lead to a suppression of local antitumor reactions and thus actually counteract endogenous immune-mediated tumor defense mechanisms.

Increased level of exhaled nitric oxide and up-regulation of inducible nitric oxide synthase in patients with primary lung cancer

Monocyte-macrophage series have an important role in host surveillance against cancer. The cytotoxic/cytostatic activity of macrophages is, to a great extent, attributed to the up-regulation of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO). Here, in 28 patients with primary lung cancer and 20 control subjects, we measured the concentration of exhaled NO and nitrite in epithelial lining fluid (ELF) using a chemiluminescence NO analyser, and studied NOS expression in alveolar macrophages (AM) and lung tissues by flow cytometry; immunohistochemical analysis was also undertaken. The mean fluorescence intensity (FI) of iNOS expression in AM was significantly increased in patients with lung cancer (tumour side 263.5 +/- 15.2 FI, normal side 232.4 +/- 18.6 FI; n = 28) compared with that in control subjects (27.3 +/- 3.2 FI; n = 20, P< 0.001). The level of exhaled NO from cancer patients (16.9 +/- 0.9 p.p.b.; n = 28) was significantly higher than that in the control group (6.0 +/- 0.5 p.p.b.; n = 20, P < 0.001). The level of nitrite was also significantly higher in ELF from cancer patients (tumour side 271.1 +/- 28.9 nM and normal side 257.4 +/- 19.6 nM vs control subjects 32.9 +/- 4.1 nM; P< 0.001). The intensity of iNOS expression in AM was correlated with the level of exhaled NO (rs = 0.73, n = 76, P< 0.001) and the nitrite released in ELF (rs = 0.56, n = 76, P< 0.001). The nitrite generation of cultured AM from patients with lung cancer was significantly enhanced compared with that of control subjects after culture for 24 h (tumour side 5.75 +/- 0.69 and normal side 5.68 +/- 0.58 microM per 106 cells vs control group 38.3 +/- 3.6 nM per 106 cells; P< 0.001). The distribution of iNOS was identified in AM, tumour-associated macrophages, endothelium, chondrocytes, airway epithelium of both lungs and malignant cells (adenocarcinoma and alveolar cell carcinoma) of cancer patients. cNOS was labelled in alveolar macrophages, endothelial cells and nerve elements from lung tissue. Our results indicate that, in patients with primary lung cancer, the production of NO from alveolar macrophages was increased as a result of the up-regulation of iNOS activity. The increased NO production was not specific to the tumour side and might be attributed to the tumour-associated non-specific immunological and inflammatory processes of the host.

Inhibition by sphingosine of leukemic cell killing by human monocytes activated with interleukin-2: a possible role of protein kinase C

Sphingosine and its analogs, which inhibit protein kinase C (PKC), are known to be potent inducers of apoptosis in tumor cells. However, we were concerned that sphingosine might also interfere with anti-tumor cells of the immune system. Therefore, we evaluated the effect of sphingosine on activation of human monocytes by interleukin-2 (IL-2) for killing of leukemic cells. Monocytes, purified by elutriation and adherence, were activated with IL-2 or interferon-gamma (IFN-gamma) in the presence or absence of sphingosine or another inhibitor for 18 h. Then the monocytes were washed and the culture medium was replaced with fresh medium to remove the sphingosine. HL- 60 and K562 leukemic cells were added to the monocyte cultures. Over the next 48 h, the cytotoxic activity of the monocytes towards the leukemic cells was assessed by means of an 111-indium-releasing assay. IL-2-activated monocytes lysed 48 +/- 3% of HL-60 cells and 44 +/- 3% of K562 cells. Sphingosine, dihydrosphingosine, N,N-dimethylsphingosine, and the PKC inhibitor H7 inhibited the activation of monocytes by IL-2, blocking cytotoxic activity against the leukemic cells by approximately 75%. These inhibitors were not toxic to monocytes at the concentrations used. In a PKC assay, sphingosine and H7 inhibited PKC activity in IL-2-treated monocytes. Thus, sphingosines, by inhibiting PKC activity, inhibited activation of monocytes by IL-2, which inhibited the killing of leukemic cells.

Effect of photodynamic pretreatment on the susceptibility of murine tumor cells to macrophage antitumor mechanisms

In vitro photodynamic treatment of YAC-1 murine T-lymphoma cells with the hematoporphyrin derivative Photosan 3 and red light resulted in dose-dependent phototoxicity. Photodynamic pretreatment, however, did not render these cells more susceptible to macrophage-mediated tumor cytotoxicity or the cytotoxic effects of macrophage-derived antitumor mediators like tumor necrosis factor alpha (TNF-alpha) or interferon beta (IFN-beta). Independent of the degree of photosensitization used, the cytotoxicity values obtained with macrophages or the different mediators were shifted by the respective values for phototoxicity, suggesting these effects to be additive and thus not interdependent. These data show that while higher overall tumor cytotoxicity can be achieved by a combination of photodynamic treatment and macrophage-mediated tumor destruction, this apparently is not a result of enhanced sensitivity of photodynamically treated tumor cells to macrophage antitumor mechanisms in general.

Taxol, a microtubule-stabilizing antineoplastic agent, differentially regulates normal and tumor-bearing host macrophage nitric oxide production

Taxol, a potent antitumor chemotherapeutic, promotes in vitro cytotoxic antitumor activities by normal host macrophage (M phi s). Because tumor growth induces functional changes among M phi populations, we determined whether fibrosarcoma growth (Meth-KDE) modified M phi responsiveness to the activating agent taxol. Tumors induce tumor-distal M phi populations to become immune suppressor cells, partially through overproduction of the cytotoxic and proinflammatory molecules nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha). Beneficial to the tumor-bearing host (TBH) when released by tumor-proximal M phi s, NO and TNF-alpha suppress lymphoproliferation and fail to impart antitumor activity when expressed in tumor-distal compartments. We report that taxol differentially regulated normal host and TBH M phi production of the immunosuppressive molecule NO by tumor-distal M phi populations. In response to IFN-gamma-priming and taxol triggering, TBH M phi s increase their production of NO as compared to resting M phi s; however, unlike normal host M phi s, taxol-induced TBH M phi NO production was significantly suboptimal. Modulation of TBH M phi NO production in tumor-distal compartments may alleviate M phi-mediated suppression of T-cell proliferative responses, yet promote sufficient NO production by tumor-associated M phi s to affect cytotoxicity. Collectively, these data leave implications for immunotherapeutic activities by the anticancer drug taxol.

C2-ceramide and C6-ceramide inhibited priming for enhanced release of superoxide in monocytes, but had no effect on the killing of leukaemic cells by monocytes

Ceramide acts as an intracellular second messenger in cellular signal transduction. We examined the effects of two cell-permeable ceramides, C2-ceramide and C6-ceramide, on human monocyte functions. After monocytes were primed with lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma) for 18 hr in suspension culture, they produced a high amount of superoxide (O2-) when triggered by phorbol myristate acetate. C2- or C6-ceramide inhibited O2- release from monocytes primed with LPS (1 ng/ml) or IFN-gamma (100 U/ml), but did not affect unprimed monocytes. An analogue, C2-dihydroceramide, was inactive. C2-ceramide was most effective at 6 microM, and C6-ceramide at 60 microM. C2- or C6-ceramide at these concentrations was not toxic for monocytes, as assessed by trypan blue exclusion and by the 3-[4, 5-dimethylthiazol-2-y1]-2,5 diphenyl tetrazolium bromide (MTT) assay which measures the ability of live cells to produce formazan. C2-ceramide (20 microM) had no effect on the killing of leukaemic cells (HL-60 and K562 cells) by monocytes treated with IFN-gamma, LPS, or both for 18 hr, with killing assessed by an 111 Indium-releasing assay. C2-ceramide (20 microM) induced secretion of low amounts of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) from the monocytes. But C2-ceramide did not alter the higher secretion of TNF-alpha or IL-1 beta from monocytes treated with IFN-gamma or LPS. Thus the cell-permeable ceramides acted like antagonists of LPS, rather than analogues of LPS, as has been proposed. The results here showed that the signal transduction pathway for O2- release by monocytes differed from that for the cytolysis of leukaemic cells, and confirmed that oxygen radicals are not involved in cytolysis.

Enhancement of lung-colonizing potential of murine tumor cell lines co-cultivated with activated macrophages

In order to explore the influence of activated macrophages on tumor cells, we cultured a series of weakly metastatic clones isolated from the murine T3 fibrosarcoma line (T3 clones) and the B16-F10 melanoma cells on feeder layers of C. parvum- or thioglycollate-elicited macrophages, or 'resident' (unstimulated) macrophages. Co-cultivation with C. parvum-elicited macrophages, but not with resident macrophages, induced an increase of the lung-colonizing potential of T3 clones and B16-F10 cells. An enhancement of lung-colonizing potential was also found in tumor cells grown in media conditioned by C. parvum-elicited macrophages. Thioglycollate-elicited macrophages also generated a pro-clonogenic activity which was however effective only on T3 clones but not on B16-F10 cells. The increase in the lung-colonizing potential of tumor cells stimulated by activated macrophages was retained to some degree after subcultivation in tissue culture medium or transplantation into syngeneic animals. In conclusion, our data support the notion that macrophages at different states of activation may enhance lung colonization of tumor cells by inducing a partially stable change of phenotype.

Anti-tumoral effect of GM-CSF with or without cytokines and monoclonal antibodies in solid tumors

Cytotoxicity is an important function of the immune system that results in destruction of cellular targets by humoral and cellular mechanisms. The functional capacity of granulocytes, lymphocytes and macrophages are of significance for cancer patients because of the ability of these cells to exhibit anti-tumor activity. The hallmark of immune cytotoxicity is the recognition and destruction of selected targets by humoral and cellular effects that distinguish between targets and normal cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine with potential to be an anti-neoplastic cytokine. GM-CSF induces: (1) differentiation of monocytes to large macrophage like cells; (2) augmentation of MHC class II antigen expression on monocytes; (3) enhancement in vitro of macrophage and granulocyte natural cytotoxicity and ADCC; and (4) increased expression of adhesion molecules and granulocytes and monocytes. GM-CSF also cooperates with other cytokines in the expansion of specific T cells. Several experimental and clinical studies have demonstrated the anti-neoplastic effects of GM-CSF alone or in combination with cytokines or/and monoclonal antibody. Interestingly, the future might see the combination of GM-CSF and mouse monoclonal antibody MAb17-1A in the adjuvant setting in colon- and/or rectal carcinoma patients.

New insights into tumor-host interactions in lymphoma metastasis

The metastatic process is characterized by a complex series of sequential steps involving constant interactions (mutual "cross-talks") of metastasized tumor cells with their microenvironment (lymphocyte, macrophages, endothelial cells, etc.) in target organs. These interactions determine the outcome of metastasis (either the eradication of metastatic cells or their increased proliferation and invasion). Recently developed methods of tumor and host cell analysis at the molecular level allow better elucidation of molecular mechanisms of metastasis and of immune mechanisms involved in antitumor responses. Direct modulation of these processes will probably increase the success of clinical cancer treatment. Here we review data (a) on the expression of some costimulatory (MHC class II, CD80, sialoadhesin) and adhesion (LFA-1, ICAM-1, VLA-4) molecules on both metastasized tumor cells and host cells and (b) on the production of a cytotoxic molecule, nitric oxide, by in situ activated Kupffer and endothelial cells in the process of liver metastasis. This study was performed with well-characterized murine ESbL T lymphoma cells transduced with the bacterial lacZ gene, which allows detection and quantification of metastases at the single cell level throughout lymphoma growth and metastasis. Experimental results are discussed in the context of recent literature.

Monocyte activation in patients with non-seminomatous germ cell tumour of the testis before and after tumour eradication

AIMS

To investigate the kinetics of normalisation of monocyte oxidative activity following tumour eradication.

METHODS

Whole blood lucigenin enhanced chemiluminescence was studied in patients with non-seminomatous germ cell tumours. Group 1 comprised 14 patients who had been "cured" of their cancer (the term "cured" as used in this report denotes a relapse free period of at least three years). Group 2 comprised 15 patients who were followed from diagnosis to up to two years after the start of treatment.

RESULTS

Lucigenin enhanced chemiluminescence of whole blood in the "cured" patients was similar to that of controls and lower than that in patients who had not yet received chemotherapy (group 2). After treatment, chemiluminescence decreased slowly and did not normalise until 18 months after the start of treatment. Tumour necrosis factor alpha (TNF alpha) concentrations were normal in "cured" patients but were raised in those who had not yet received treatment. TNF alpha was normalised 12 months after start of treatment. Alpha-fetoprotein concentrations were raised in most patients but normalised rapidly after tumour eradication.

CONCLUSIONS

The activity of blood monocytes, as measured by whole blood lucigenin enhanced chemiluminescence, is increased in cancer. This activity may be a consequence of the presence of tumour cells. Immunocompetent cells remain active for over a year after eradication of the tumour.

Human breast cancer cell line xenografts as models of breast cancer. The immunobiologies of recipient mice and the characteristics of several tumorigenic cell lines

The ability to maintain and study human tissues in an in vivo environment has proved to be a valuable tool in breast cancer research for several decades. The most widely studied tissues have been xenografts of established human breast cancer cell lines into athymic nude mice. Human breast tumor xenografts provide the opportunity to study various important interactions between the tumor and host tissues, including endocrinologic, immunologic, and tumor-stroma interactions. The nude mouse is not the only immune-deficient recipient system in which to study xenografts. Additional single and combined mutant strains have been used successfully, including mice homozygous for the severe combined immune deficiency mutation (scid), both the beige (bg) and nude (nu) mutations in combination (bg/nu), and mice bearing the combined bg/nu/xid mutations. The differing immunobiologies are discussed, with particular reference to the immunobiology of breast cancer, as are the characteristics of several of the more frequently utilized breast cancer xenografts and cell lines. The ability of several endocrine treatments to modulate effectors of cell mediated immunity, e.g., estrogens and antiestrogens, and the effect of site of inoculation on tumor take and metastasis, also are described.

The effects of granulocyte-macrophage colony-stimulating factor on tumour-infiltrating lymphocytes from renal cell carcinoma

It has been shown that granulocyte-macrophage colony-stimulating factor (GM-CSF) can induce specific and non-specific anti-tumour cytotoxicity and also stimulates the proliferation and function of peripheral lymphocytes and thymocytes. GM-CSF and interleukin 2 (IL-2) act synergistically on peripheral lymphocytes for the induction of a highly effective cytotoxic cell population. Thus, the goal of our investigation was to study the effects of GM-CSF upon expansion, proliferation and in vitro killing activity of tumour-infiltrating lymphocytes (TILs) from renal cell carcinoma (RCC). TILs from seven consecutive tumours were cultured with GM-CSF (500 or 1000 nmol ml-1) without IL-2 supplementation, with suboptimal doses of IL-2 (8 and 40 U ml-1) plus GM-CSF (1000 nmol ml-1), and with a dose of IL-2 (400 U ml-1) which sufficed alone to induce TIL development plus GM-CSF (500 or 1000 nmol ml-1). GM-CSF alone or together with suboptimal doses of IL-2 was not able to induce or facilitate TIL development in these cultures. When GM-CSF at both concentrations studied was added to optimal doses of IL-2 the resulting TIL populations proliferated significantly better and faster (+66%), resulting in a higher cell yield (+24%) at the time of maximal expansion of the TIL cultures. The length of the culture periods of TILs was not affected by GM-CSF when compared with the control cultures supplemented with IL-2 alone. In vitro killing activity of TIL populations stimulated with IL-2 and GM-CSF remained unspecific, but lysis of the autologous tumour targets as well as the allogeneic renal tumour targets was significantly enhanced (+138%) as compared with the corresponding control TILs stimulated with IL-2 alone. Lysis of the natural killer (NK)-sensitive control cell line K562 and the NK-resistant Daudi cell line remained unchanged even though FACS analysis of TILs cultured with IL-2 and 1000 nmol of GM-CSF demonstrated a significantly higher proportion of cells expressing the CD56 molecule (+50%). Specific receptors for GM-CSF could not be demonstrated on TILs from RCC. Our data demonstrate that GM-CSF alters the biological behaviour of IL-2-activated TILs from renal cell carcinoma in terms of proliferation, in vitro killing activity and cell-surface molecule expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibody-independent phagocytosis of tumor cells by human monocyte-derived macrophages cultured in recombinant macrophage colony-stimulating factor

Human monocytes exposed in vitro to recombinant macrophage-colony-stimulating factor (rhMCSF) differentiate into monocyte-derived macrophages (MDM), which mediate efficient antibody-dependent cytotoxicity (ADCC) against tumor cells. We and others have shown that this form of ADCC is unusual in that phagocytosis, rather than extracellular lysis, appears to play the major role in target cell killing. In this study, we asked whether the phagocytic form of cytotoxicity seen with ADCC could occur in the absence of an opsonizing antibody. We now report that, whereas cell lines derived from solid tumors are often resistant to antibody-independent cytotoxicity, malignant cells of lymphoid origin appear particularly susceptible to such antibody-independent killing. We found that all of nine lymphocytic leukemia and lymphoma cell lines tested in a total of 35 experiments, plus all four samples of fresh leukemic blasts, were consistently susceptible to antibody-independent MDM cytotoxicity. Antibody-independent cytotoxicity against these cells was efficient (40%-63% killing) at effector: target (E:T) ratios as low as 2:1. Like ADCC, antibody-independent cytotoxicity involved phagocytosis of target cells, as demonstrated by ingestion of fluorescently labeled targets and analysis by flow cytometry. At the time of phagocytosis, the majority of target cells retained membrane integrity, as indicated by the direct transfer of intracellular [51Cr]chromate from radiolabeled targets to phagocytosing MDM, without release of the label into the medium. However, in contrast to ADCC, we found that the degree of antibody-independent cytotoxicity was not a function of the E:T ratio. Instead, a constant proportion of the available target cells were killed regardless of the E:T ratio, suggesting that target cell recognition, rather than effector cell potency, might be the limiting factor in determining cytotoxicity. In additional experiments, we have also identified a second tumor cell type, nueroblastoma, as being susceptible to antibody-independent phagocytosis (all of five cell lines tested, cytotoxicity 40%-93%, E:T = 3:1). Our data thus indicate that the cytotoxicity induced by rhMCSF is not confined to antibody-mediated killing, and that phagocytosis can play a significant role in target cell destruction even in the absence of opsonizing antibody.

Monocyte activation by tumour cells: a role for carbohydrate structures associated with CD2

Monocytes/macrophages can kill tumour cells and mediate tumour-destructive host responses e.g. by releasing tumour necrosis factor-alpha (TNF-alpha). The underlying mechanisms of tumour cell recognition, however, are not clear. Previous work in our laboratory suggested that carbohydrate moieties associated with the T cell adhesion molecule CD2 of Jurkat cells induce TNF-alpha secretion by human monocytes. In this study we present data indicating that the stimulatory capacity for TNF-alpha secretion is confined to carbohydrate moieties of tumour cell CD2. Irradiated resting peripheral T cells did not display stimulatory activity in contrast to irradiated Jurkat cells although surface expression of CD2 was similar. Activated T cells, however, induced TNF-alpha production by monocytes via a CD2-independent mechanism. Only affinity purified CD2 prepared from Jurkat cells but not from non-transformed T cells activated monocytes to secrete TNF-alpha. This activation process was blocked by anti-CD2 antibodies. Neuraminidase and PNGaseF treatment of isolated CD2 inhibited the stimulatory capacity whereas pronase treatment did not. These data suggest that carbohydrate moieties containing sialic acid mediate stimulation of monocytes. Taken together, these results indicate a role for glycosylation patterns typical of tumour cells in the recognition process of tumour cells by monocytes/macrophages.

Activation of Fc receptor-mediated phagocytosis by mouse peritoneal macrophages following the intraperitoneal administration of liposomes

The effects of liposomes on the phagocytic activity of mouse peritoneal macrophages were investigated using IgG-opsonized sheep red blood cells (SRBC). The highest ingestion index of opsonized SRBC via Fc receptors of macrophages from BALB/c mice was observed for macrophages harvested on day 4 following the intraperitoneal injection of liposomes (2.27 mumol lipid/mouse). An increase in the ingestion index was observed irrespective of liposomal charge. Binding parameters of Fc receptors of macrophages from liposome- or saline-injected mice were determined using horseradish peroxidase-conjugated IgG, and an increase in the number of binding sites with the same binding constant was observed in macrophages from liposome-injected mice. The activation mechanism of mouse peritoneal macrophages by liposomes differed from that by lipopolysaccharides. Liposomes thus appear to contribute to the activation of immune response.

Effect of liposome-muramyl tripeptide combined with recombinant canine granulocyte colony-stimulating factor on canine monocyte activity

Liposome-muramyl tripeptide-phosphatidylethanolamine (L-MTP-PE) has been shown to activate monocytes in vivo to become tumoricidal resulting in reduction in metastasis as well as prolongation of survival time in murine and canine tumor models. Granulocyte colony-stimulating factor (G-CSF) is a cytokine which will stimulate the proliferation of granulocytes as well as monocytes. Recombinant canine G-CSF (rcG-CSF) was administered to normal dogs as a method of increasing the monocyte population prior to in vivo monocyte activation using L-MTP-PE. rcG-CSF administration resulted in a 3.5-fold increase in absolute monocyte counts and when combined with L-MTP-PE, resulted in an enhanced level of serum tumor necrosis factor-alpha activity compared to dogs treated with L-MTP-PE alone. G-CSF alone did not affect monocyte cytostatic activity, however, dogs receiving G-CSF had a significant increase in monocyte cytostatic activity following L-MTP-PE. The combined use of CSFs and effector cell activators deserves further evaluation in clinical trials.

Leukemic cell lysis by activated human macrophages: significance of membrane-associated tumor necrosis factor

In this study, we analyzed the mechanism(s) of leukemic cell lysis by human macrophages. Peripheral blood monocyte-derived macrophages were activated with recombinant interferon-gamma and lipopolysaccharide and their lytic activity against two leukemic cell lines (K562 and HL-60 cells) was assessed by an 111In releasing assay. Activated macrophages lysed these leukemic cells, and the lytic activity against leukemic cells was almost completely inhibited by anti-tumor necrosis factor (TNF) antibody. The macrophage-lysate prepared from activated macrophages also exhibited significant lytic activity against leukemic cells; this lytic activity was inhibited by anti-TNF antibody. The leukemic cells that we used for the cytotoxicity assays were resistant to recombinant TNF. The culture supernatant of activated macrophages did not show any lytic activity. These findings suggest that cell-associated TNF plays a role in macrophage-mediated cytotoxicity against leukemic cells.