Chemotactic activity for mononuclear phagocytes of culture supernatants from murine and human tumor cells: evidence for a role in the regulation of the macrophage content of neoplastic tissues

Lactate: The Mediator of Metabolism and Immunosuppression

The Warburg effect, one of the hallmarks of tumors, produces large amounts of lactate and generates an acidic tumor microenvironment via using glucose for glycolysis. As a metabolite, lactate not only serves as a substrate to provide energy for supporting cell growth and development but also acts as an important signal molecule to affect the biochemical functions of intracellular proteins and regulate the biological functions of different kinds of cells. Notably, histone lysine lactylation (Kla) is identified as a novel post-modification and carcinogenic signal, which provides the promising and potential therapeutic targets for tumors. Therefore, the metabolism and functional mechanism of lactate are becoming one of the hot fields in tumor research. Here, we review the production of lactate and its regulation on immunosuppressive cells, as well as the important role of Kla in hepatocellular carcinoma. Lactate and Kla supplement the knowledge gap in oncology and pave the way for exploring the mechanism of oncogenesis and therapeutic targets. Research is still needed in this field.

Macrophages in tumor: An inflammatory perspective

Inflammation is a part of carefully co-ordinated healing immune exercise to eliminate injurious stimuli. However, in substantial number of cancer types, it contributes in shaping up of robust tumor microenvironment (TME). Solid TME promotes infiltration of tumor associated macrophages (TAMs) that contributes to cancer promotion. TAMs are functionally heterogeneous and display an extraordinary degree of plasticity, which allow 'Switching' of macrophages into an 'M2', phenotype, linked with immunosuppression, advancement of tumor angiogenesis with metastatic consequences. In contrary to the classical M1 macrophages, these M2 TAMs are high-IL-10, TGF-β secreting-'anti-inflammatory'. In this review, we will discuss the modes of infiltration and switching of TAMs into M2 anti-inflammatory state in the TME to promote immunosuppression and inflammation-driven cancer.

A reconfigurable microscale assay enables insights into cancer-associated fibroblast modulation of immune cell recruitment

Innate immune cell infiltration into neoplastic tissue is the first line of defense against cancer and can play a deterministic role in tumor progression. Here, we describe a series of assays, using a reconfigurable microscale assay platform (i.e. Stacks), which allows the study of immune cell infiltration in vitro with spatiotemporal manipulations. We assembled Stacks assays to investigate tumor-monocyte interactions, re-education of activated macrophages, and neutrophil infiltration. For the first time in vitro, the Stacks infiltration assays reveal that primary tumor-associated fibroblasts from specific patients differ from that associated with the benign region of the prostate in their ability to limit neutrophil infiltration as well as facilitate monocyte adhesion and anti-inflammatory monocyte polarization. These results show that fibroblasts play a regulatory role in immune cell infiltration and that Stacks has the potential to predict individual patients' cancer-immune response.

CCL2 in the Tumor Microenvironment

The C-C motif chemokine ligand 2 (CCL2) is a crucial mediator of immune cell recruitment during microbial infections and tissue damage. CCL2 is also frequently overexpressed in cancer cells and other cells in the tumor microenvironment, and a large body of evidence indicates that high CCL2 levels are associated with more aggressive malignancies, a higher probability of metastasis, and poorer outcomes in a wide range of cancers. CCL2 plays a role in recruiting tumor-associated macrophages (TAMs), which adopt a pro-tumorigenic phenotype and support cancer cell survival, facilitate tumor cell invasion, and promote angiogenesis. CCL2 also has direct, TAM-independent effects on tumor cells and the tumor microenvironment, including recruitment of other myeloid subsets and non-myeloid cells, maintaining an immunosuppressive environment, stimulating tumor cell growth and motility, and promoting angiogenesis. CCL2 also plays important roles in the metastatic cascade, such as creating a pre-metastatic niche in distant organs and promoting tumor cell extravasation across endothelia. Due to its many roles in tumorigenesis and metastatic processes, the CCL2-CCR2 signaling axis is currently being pursued as a potential therapeutic target for cancer.

The chemokine MCP-1 (CCL2) in the host interaction with cancer: a foe or ally?

Macrophages are one of the most abundant leukocyte populations infiltrating tumor tissues and can exhibit both tumoricidal and tumor-promoting activities. In 1989, we reported the purification of monocyte chemoattractant protein-1 (MCP-1) from culture supernatants of mitogen-activated peripheral blood mononuclear cells and tumor cells. MCP-1 is a potent monocyte-attracting chemokine, identical to the previously described lymphocyte-derived chemotactic factor or tumor-derived chemotactic factor, and greatly contributes to the recruitment of blood monocytes into sites of inflammatory responses and tumors. Because in vitro-cultured tumor cells often produce significant amounts of MCP-1, tumor cells are considered to be the main source of MCP-1. However, various non-tumor cells in the tumor stroma also produce MCP-1 in response to stimuli. Studies performed in vitro and in vivo have provided evidence that MCP-1 production in tumors is a consequence of complex interactions between tumor cells and non-tumor cells and that both tumor cells and non-tumor cells contribute to the production of MCP-1. Although MCP-1 production was once considered to be a part of host defense against tumors, it is now believed to regulate the vicious cycle between tumor cells and macrophages that promotes the progression of tumors.

Macrophages, Neutrophils, and Cancer: A Double Edged Sword

The tumor microenvironment is a well-recognized framework, in which myeloid cells play important roles in cancer development from tumor initiation to metastasis. Immune cells present in the tumor microenvironment can promote or inhibit cancer formation and development. Diversity and plasticity are hallmarks of cells of the monocyte-macrophage lineage. In response to distinct signals the cells of the monocyte-macrophage lineage have the ability to display a wide spectrum of activation states; classical Ml or alternative M2 macrophages represent extremes of a continuum of this activation. Tumor-associated macrophages generally acquire an M2-like phenotype that is relevant for their participation in tumor growth and progression. There is now evidence that also neutrophils can be driven towards distinct phenotypes in response to microenvironmental signals. In fact they can interact with distinct cell populations and produce a wide number of cytokines and effector molecules. Therefore, macrophages and neutrophils are both integrated in the regulation of the innate and adaptive immune responses in various inflammatory situations, including cancer. These findings have triggered efforts to target tumor-associated macrophages and neutrophils. In particular, “reeducation” to activate their antitumor potential or elimination of tumor promoting cells is a new strategy undergoing preclinical and clinical evaluation.

Tumor associated macrophages and neutrophils in tumor progression

Tumor-associated macrophages (TAMs) are a key component of the tumor microenvironment and orchestrate various aspects of cancer. Diversity and plasticity are hallmarks of cells of the monocyte-macrophage lineage. In response to distinct signals macrophages undergo M1 (classical) or M2 (alternative) activation, which represent extremes of a continuum in a spectrum of activation states. Metabolic adaptation is a key component of macrophage plasticity and polarization, instrumental to their function in homeostasis, immunity and inflammation. Generally, TAMs acquire an M2-like phenotype that plays important roles in many aspects of tumor growth and progression. There is now evidence that also neutrophils can be driven towards distinct phenotypes in response to microenvironmental signals. The identification of mechanisms and molecules associated with macrophage and neutrophil plasticity and polarized activation provides a basis for new diagnostic and therapeutic strategies.

Tumor associated macrophages and neutrophils in cancer

The tumor microenvironment is a complex framework, in which myeloid cells play important roles in sculpting cancer development from tumor initiation to metastasis. Immune cells are key participants of the tumor microenvironment where they can promote or inhibit cancer formation and development. Plasticity is a widely accepted hallmark of myeloid cells and in particular of the monocyte-macrophage lineage. It includes the ability to display a wide spectrum of activation states in response to distinct signals and classical M1 or alternative M2 macrophages represent a paradigm of this feature. Neutrophils have long been viewed as terminally differentiated effector cells, playing a major role during the acute phase of inflammation and resistance against microbes. Recent evidence questioned this limited point of view, indicating that neutrophils can interact with distinct cell populations and produce a wide number of cytokines and effector molecules. Therefore, macrophages and neutrophils are both integrated in the regulation of the innate and adaptive immune responses in various inflammatory situations, including cancer.

Epigallocatechin gallate reduces human monocyte mobility and adhesion in vitro

BACKGROUND AND PURPOSE

Monocytes/macrophages are an important population of immune inflammatory cells that have diverse effector functions in which their mobility and adhesion play a very relevant role. Epigallocatechin gallate (EGCG), a major component of green tea, has been reported to have anti-allergic and anti-inflammatory activities, but its effects on monocytes remain to be determined. Here we investigated the effects of EGCG on the migration and adhesion of monocytes.

EXPERIMENTAL APPROACH

We used a human monocyte cell line (THP-1) to analyse the effects of treatment with EGCG under non-cytotoxic conditions on the expression levels of the monocyte chemotactic protein-1 (MCP-1) and of the MCP-1 receptor (CCR2) and on the activation of beta1 integrin. A functional validation was carried out by evaluating the inhibitory effect of EGCG on monocyte adhesiveness and migration in vitro.

KEY RESULTS

Treatment of THP-1 cells with EGCG decreased MCP-1 and CCR2 gene expression, together with MCP-1 secretion and CCR2 expression at the cell surface. EGCG also inhibited beta1 integrin activation. The effects on these molecular targets were in agreement with the EGCG-induced inhibition of THP-1 migration in response to MCP-1 and adhesion to fibronectin.

CONCLUSIONS AND IMPLICATIONS

Under our experimental conditions, EGCG treatment inhibited the migration and adhesion of monocytes. These inhibitory effects of EGCG on monocyte function should be considered as a promising new anti-inflammatory response with a potential therapeutic role in the treatment of inflammation-dependent diseases.

Chemokine-protease interactions in cancer

Solid tumour and leukemic cells expressing chemokine receptors, metastasize to chemokine-secreting organs. Chemokines indirectly affect tumour development by attracting immunocompetent cells with pro- or anti-tumoral activities. Various membrane-associated and soluble proteases selectively cleave specific chemokines. Precursor plasma chemokines (CXCL7, CCL14) need to be proteolytically processed to obtain receptor affinity. Angiogenic CXC chemokines (CXCL1, CXCL8) have increased CXCR1/CXCR2 affinity after limited NH2-terminal processing, whereas truncated angiostatic chemokines (CXCL10) show lower CXCR3 affinity without loss of angiostatic potential. NH2-terminally cleaved monocyte chemotactic proteins (CCL2, CCL7, CCL8) have impaired capacity to attract tumour-associated macrophages and function as receptor antagonists for intact CC chemokines. Migration of Th1/CCR5+ and Th2/CCR4+ effector lymphocytes toward CCR5 (CCL5, CCL3L1) and CCR4 (CCL22) ligands is affected by cleavage. Although proteolytical processing of chemokines is well studied in vitro, the direct or indirect effects on tumour invasion and metastasis are only poorly evaluated.

Identification of a blood-derived chemoattractant for neutrophils and lymphocytes as a novel CC chemokine, Regakine-1

Chemokines constitute a large family of chemotactic cytokines that selectively attract different blood cell types. Although most inflammatory chemoattractants are only induced and released in the circulation during acute infection, a restricted number of CXC and CC chemokines are constitutively present in normal plasma at high concentrations. Here, such a chemotactic protein was purified to homogeneity from serum and fully identified as a novel CC chemokine by mass spectrometry and amino acid sequence analysis. The protein, tentatively designated Regakine-1, shows less than 50% sequence identity with any known chemokine. This novel CC chemokine chemoattracts both neutrophils and lymphocytes but not monocytes or eosinophils. Its modest chemotactic potency but high blood concentration is similar to that of other chemokines present in the circulation, such as hemofiltrate CC chemokine-1, platelet factor-4, and beta-thromboglobulin. Regakine-1 did not induce neutrophil chemokinesis. However, it synergized with the CXC chemokines interleukin-8 and granulocyte chemotactic protein-2, and the CC chemokine monocyte chemotactic protein-3, resulting in an at least a 2-fold increase of the neutrophil and lymphocyte chemotactic response, respectively. The biologic effects of homogeneous natural Regakine-1 were confirmed with chemically synthesized chemokine. Like other plasma chemokines, it is expected that Regakine-1 plays a unique role in the circulation during normal or pathologic conditions.

Detection and localization of Mip-3alpha/LARC/Exodus, a macrophage proinflammatory chemokine, and its CCR6 receptor in human pancreatic cancer

Macrophage Proinflammatory Human Chemokine-3alpha (Mip-3alpha/LARC/Exodus) belongs to a large family of chemotactic cytokines, which participate in directing inflammatory cell migration and in modulating angiogenesis. Mip-3alpha signals through a recently identified G-protein linked 7-transmembrane receptor, CCR6. In this study, we have characterized the expression of Mip-3alpha and CCR6 in 12 normal and 16 cancerous human pancreatic tissues and in 4 cultured pancreatic cancer cell lines, and assessed the effects of Mip-3alpha on growth and invasion of these cell lines. Pancreatic cancer tissues markedly overexpressed Mip-3alpha in comparison with normal pancreatic samples. By in situ hybridization Mip-3alpha and CCR6 mRNA moieties were present in cancer cells within the tumors. In addition, Mip-3alpha was abundant in the macrophages infiltrating the tumor mass. Mip-3alpha and its receptor CCR6 were expressed in all 4 tested pancreatic cancer cell lines. Mip-3alpha stimulated the growth of one cell line, enhanced the migration of another cell line, and was without effect in the other 2 cell lines. Together, our findings suggest that Mip-3alpha has the potential to act via autocrine and paracrine mechanisms to contribute to the pathobiology of human pancreatic cancer.

Chemokines: a superfamily of chemotactic cytokines

Chemokines are a bipartite family of chemotactic proteins that bear the structural hallmark of four cysteine residues, the first two of which are in tandem. The spectrum of action of chemokines encompasses a large number of leukocyte populations, including monocytes, granulocytes, lymphocytes, NK and dendritic cells. Although the spectrum of action of chemokines largely overlaps, clear differences are still present. Chemokines play an important role in the recruitment of leukocytes at the site of inflammation, allergic reaction and tumors. Available information on receptor usage by MCP-1 and related chemokines and signal transduction pathways is reviewed. The better understanding of signaling mechanisms will provide a new basis for the development of therapeutic strategies.

The detection and localization of monocyte chemoattractant protein-1 (MCP-1) in human ovarian cancer

Chemokines may control the macrophage infiltrate found in many solid tumors. In human ovarian cancer, in situ hybridization detected mRNA for the macrophage chemokine monocyte chemoattractant protein-1 (MCP-1) in 16/17 serous carcinomas, 4/4 mucinous carcinomas, 2/2 endometrioid carcinomas, and 1/3 borderline tumors. In serous tumors, mRNA expression mainly localized to the epithelial areas, as did immunoreactive MCP-1 protein. In the other tumors, both stromal and epithelial expression were seen. All tumors contained variable numbers of cells positive for the macrophage marker CD68. MCP-1 mRNA was also detected in the stroma of 5/5 normal ovaries. RT-PCR demonstrated mRNA for MCP-1 in 7/7 serous carcinomas and 6/6 ovarian cancer cell lines. MCP-1 protein was detected by ELISA in ascites from patients with ovarian cancer (mean 4.28 ng/ml) and was produced primarily by the cancer cells. Human MCP-1 protein was also detected in culture supernatants from cell lines and in ascites from human ovarian tumor xenografts which induce a peritoneal monocytosis in nude mice. We conclude that the macrophage chemoattractant MCP-1 is produced by epithelial ovarian cancer and that the tumor cells themselves are probably a major source. MCP-1 may contribute to the accumulation of tumor-associated macrophages, which may subsequently influence tumor behavior.

Expression of the JE/MCP-1 gene suppresses metastatic potential in murine colon carcinoma cells

The purpose of this study was to determine whether the expression of the JE/MCP-1 gene encoding for the monocyte chemottractant protein, MCP-1 (also known as monocyte chemotactic and activating factor MCAF, TDCF, and SMC-CF) can influence the metastatic properties of tumor cells. The highly metastatic murine colon carcinoma CT-26 cells, syngeneic to BALB/c mice that do not produce endogenous JE/MCP-1 protein, were transfected with a BCMGS-Neo expression vector (control) or a vector containing full-length JE cDNA. CT-26 parental cells, CT-26 Neo, and CT-26 JE/MCP-1-positive cells were injected into syngeneic or nude mice. The CT-26 JE/MCP-1-positive cells produced significantly fewer lung metastases. The decrease in incidence of metastasis was not due to the inability of the transfected cells to arrest in the lung vasculature or to differences in cell cycle time. CT-26 cells producing JE/MCP-1 were highly susceptible to lysis by syngeneic macrophages treated with subthreshold concentrations of lipopolysaccharide. In addition, culture supernatants of JE/MCP-1-expressing cells plus lipopolysaccharide synergistically activated tumoricidal properties in syngeneic macrophages. This activity was blocked by anti-JE/MCP-1 antibodies, indicating the involvement of the JE/MCP-1 molecule in this process. Moreover, purified JE/MCP-1 added to lipopolysaccharide-containing medium resulted in significant activation of macrophages against parental CT-26 cells. These data suggest that, in addition to its chemotactic properties, JE/MCP-1 can synergize with bacterial endotoxins to activate macrophages to become tumoricidal and, hence, could suppress metastasis.

Association of different macrophage phenotypes with infiltrating and non-infiltrating areas of tumor-host interface in colorectal carcinoma

At the tumor-host interface (interface) of well differentiated tubulary or tubulopapillary colorectal carcinomas infiltrative, poorly demarcated and non-infiltrative, well bordered areas alternate. The composition of the inflammatory infiltrate within the desmoplastic stroma of the central tumor part and the interface was analyzed, particularly emphasizing differences between infiltrative and non-infiltrative areas of the interface. Of particular interest was the distribution of the following recently identified, functionally different human macrophage phenotypes: the 27E10-positive phenotype, an inflammatory macrophage, the 25F9-positive phenotype, a mature, resident macrophage and the RM3/1-positive phenotype, associated with anti-inflammatory function. It was found that macrophages were the dominating cells in the inflammatory infiltrate of both central tumor part and interface and that the number of B-cells and NK-cells were negligible. The 27E10-positive phenotype revealed a strong association with infiltrative areas at the interface, whereas the resident macrophage together with the RM3/1 was associated with sharply bordered tumor areas dominating within the tumor stroma, particularly in carcinomas with marked desmoplastic stroma response. These findings suggest that different macrophage phenotypes, localized in different regions of the carcinoma, have different effects on tumor cells.

Liposome-encapsulated muramyl tripeptide up-regulates monocyte chemotactic and activating factor gene expression in human monocytes at the transcriptional and post-transcriptional levels

Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) is a novel immune modulator that is now under investigation against metastatic melanoma and osteosarcoma. We have already reported that L-MTP-PE induced monocyte-mediated tumoricidal activity and up-regulation of the tumor necrosis factor and interleukin-1 (IL-1) in vivo and in vitro. We now demonstrate that L-MTP-PE also induces monocyte chemotactic and activating factor (MCAF) mRNA expression at both the transcriptional and post-transcriptional levels. Monocyte chemotactic activity was also present in the supernatants of L-MTP-PE-stimulated cells. In monocytes, the increased expression of MCAF was induced rapidly (by 2 h) but was short-lived. By 4 h, MCAF mRNA had decreased to background level. We found no change in MCAF mRNA levels in lymphocytes exposed to L-MTP-PE. We therefore conclude that L-MTP-PE selectively up-regulates MCAF expression in monocytes and that MCAF may play a role in the tumoricidal and immune-stimulating activity of L-MTP-PE.

Species-specificity of monocyte chemotactic protein-1 and -3

The present study was aimed at defining the activity of human and mouse monocyte chemotactic protein-1 (MCP-1) on homologous and heterologous mononuclear phagocytes. Human natural and recombinant MCP-1 and mouse natural MCP-1/JE were tested as chemoattractants on human blood monocytes and mouse peritoneal macrophages. The human and murine cytokines were equiactive on human monocytes. Human MCP-1 was active on mouse macrophages but the maximal chemotactic effect elicited was about half that of human cells or of mouse MCP-1/JE or of reference chemoattractants. Human MCP-3, a recently identified member of the C-C chemokine family, with high sequence similarity to MCP-1/JE, was also active on mouse mononuclear phagocytes, though less so than mouse MCP-1/JE. These results caution against under-estimating the potential of MCPs when the human chemokines are applied in mice.

Macrophage infiltration and growth of sarcoma clones expressing different amounts of monocyte chemotactic protein/JE

Tumor-derived chemotactic factors (TDCF) have been identified and thought to play a role in the regulation of macrophage infiltration in neoplastic tissues. The present study was designed to assess the in vivo relevance of the TDCF molecularly identified as monocyte chemotactic protein/JE, by investigating murine sarcoma clones expressing different levels of MCP/JE. The 1D3 clone derived from the B77 RSV-induced sarcoma expressed appreciable levels of MCP/JE mRNA and, concomitantly, chemotactic activity for mononuclear phagocytes. In contrast, the 5B11 clone from the same tumor had undetectable levels of MCP/JE transcripts and little or no chemotactic activity. The chemotactic activity of 1D3 cells was blocked by an appropriate specific antiserum. The in vitro growth rate of the 2 sarcoma lines was identical. Upon in vivo transplantation, the 1D3 clone showed a substantially higher level of tumor-associated macrophages (28.9%; range 21%-34%) than the 5B11 clone (16.6%; range 13%-20%). 5B11-induced tumors appeared earlier and grew faster than those induced by 1D3. The difference in growth rate and in macrophage infiltration between 1D3 and 5B11 clones was also evident upon transplantation into nude mice. These results are consistent with the hypothesis that TDCF, identified as MCP/JE, is one important determinant of macrophage infiltration in tumors.

Expression and secretion of leukocyte chemotactic cytokines by normal human melanocytes and melanoma cells

The capacity of human melanocytes and melanoma cells to produce IL-8 and monocyte chemotactic and activating factor (MCAF) was investigated. Melanocytes expressed mRNA for IL-8 and MCAF, when stimulated with either IL-1 alpha or TNF alpha, but not when stimulated with IL-6, IFN gamma, or LPS alone. IL-8 and MCAF could be induced in a dose-dependent fashion with doses as low as 0.1 ng/ml TNF alpha and 0.5 ng/ml IL-1 alpha. IL-8 and MCAF mRNA were rapidly expressed and peaked between 2 and 4 h for IL-8 and between 4 and 8 h for MCAF. This correlated well with the accumulation of IL-8 antigen as measured by a radioimmunoassay. Supernatants from melanocyte cultures stimulated with either IL-1 alpha or TNF alpha and separated on a heparin-Sepharose column became positive for neutrophil and monocyte chemotactic activity in a dose- and time-dependent fashion. When IFN gamma was added to melanocyte cultures stimulated with suboptimal doses of TNF alpha there was a synergistic increase in secreted IL-8 protein and monocyte chemotactic activity. These data provide further evidence for the possible role of melanocytes in the initiation of an inflammatory reaction. Three different malignant melanoma cell lines stimulated with either TNF alpha or IL-1 alpha expressed IL-8 mRNA, but not mRNA for MCAF. The IL-8 mRNA signal corresponded well with the amount of secreted IL-8 protein. These data suggest that IL-8 and MCAF may play a role in growth regulation and spreading of melanomas.

Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Two chemoattractants for human monocytes were purified to apparent homogeneity from the culture supernatant of a glioma cell line (U-105MG) by sequential chromatography on Orange A-Sepharose, an HPLC cation exchanger, and a reverse phase HPLC column. On SDS-PAGE gels under reducing or nonreducing conditions, the molecular masses of the two peptides glioma-derived chemotactic factor 1 and 2 were 15 and 13 kD, respectively. Amino acid composition of these molecules was almost identical, and differed from other cytokines that have been reported. The NH2 terminus of each peptide was apparently blocked. When tested for chemotactic efficacy, the peptides attracted approximately 30% of the monocytes added to chemotaxis chambers, at the optimal concentration of 10(-9) M. Potency and efficacy were comparable with that of FMLP, which is often used as a reference attractant. The activity was chemotactic rather than chemokinetic. In contrast to their interaction with human monocytes, the pure peptides did not attract neutrophils. These pure tumor-derived chemoattractants can now be compared with attractants produced by normal cells and evaluated for their biological significance in human neoplastic disease.

Purification and amino acid analysis of two human glioma-derived monocyte chemoattractants

Two chemoattractants for human monocytes were purified to apparent homogeneity from the culture supernatant of a glioma cell line (U-105MG) by sequential chromatography on Orange A-Sepharose, an HPLC cation exchanger, and a reverse phase HPLC column. On SDS-PAGE gels under reducing or nonreducing conditions, the molecular masses of the two peptides glioma-derived chemotactic factor 1 and 2 were 15 and 13 kD, respectively. Amino acid composition of these molecules was almost identical, and differed from other cytokines that have been reported. The NH2 terminus of each peptide was apparently blocked. When tested for chemotactic efficacy, the peptides attracted approximately 30% of the monocytes added to chemotaxis chambers, at the optimal concentration of 10(-9) M. Potency and efficacy were comparable with that of FMLP, which is often used as a reference attractant. The activity was chemotactic rather than chemokinetic. In contrast to their interaction with human monocytes, the pure peptides did not attract neutrophils. These pure tumor-derived chemoattractants can now be compared with attractants produced by normal cells and evaluated for their biological significance in human neoplastic disease.

Myelokathexis associated with multiple congenital malformations: immunological study on phagocytic cells and lymphocytes

A 5-year-old boy was first seen at the age of 11 months when he presented with growth retardation, skeletal dysmorphisms and neutropenia. Since then he has remained leukopenic except when he has pulmonary infections with a marked leukocytosis. Despite his neutropenia, marked myeloid hyperplasia was evident on marrow smear examination; many cells showed abnormally hypersegmented nuclei, with unusual shape or pyknotic nuclei. Phagocytic cells showed impaired phagocytosis, candidacidal activity, metabolic burst and chemotaxis. Moreover, the patient's serum generated less chemotactic activity than normal serum. These data indicate a selectively complex defect of the neutrophil during differentiation associated with the presence of an inhibitor of chemotactic factors in the patient's serum.

Enhancement of production of superoxide anion by human monocytes exposed to products of HT 29 human colonic adenocarcinoma cell line

The generation of superoxide anion (O2-) by human blood monocytes in response to stimulation by either phorbol myristate acetate (PMA) or opsonized Zymosan was greatly enhanced (range: 100-200% according to donor) by prior exposure of the peripheral blood mononuclear cells (PBM) to human colonic adenocarcinoma cells (HT 29 line) or their conditioned culture medium (DMEM-HT 29). This priming effect was observed after 5 hr and persisted for up to 15 hr of contact between PBM and endotoxin-free DMEM-HT 29. Beyond this time, primed monocytes gradually lost this ability. However, they maintained a higher capacity (about 100%) to produce O2- when compared to controls. DMEM-HT 29-induced monocyte priming requires that the tumor-active substance(s) act(s) on 2 target cells: first, on non adherent mononuclear cells (NA-PBM) to induce cytokine production and, second, on the monocyte itself. Priming activity was also found in conditioned medium from FR3T3 embryonic fibroblasts but not in conditioned medium from HT 29 repolarized cells (by culture in glucose-free medium) or from non-tumorous human colonic mucosa explants.

The immunological network at the site of tumor rejection

The tumor mass irrespective of its type or location in the body has long been shrouded in mystery and even today we still have only a tentative handle on its secrets. Attempts to manipulate either the tumor cells per se or host-derived leukocytes have, on the whole, not been successful or at best questionable. The ability of the host to respond immunologically to TSTA is well documented, yet again attempts to manipulate this response have been disappointing. One of the problems has been a lack of knowledge concerning the tumor mass and its constituents, such as the intratumor leukocytes, and the significance of their presence to the biological properties of the neoplasm [8,9,80]. The purpose in studying the immunological network is, in part, to try to assign a function to these cells on the premise that lymphoid elements and macrophages have a potential role to play in recognition of TSTA. The advantage of adoptive immunotherapy model systems is that tumor rejection can be achieved under controlled conditions and this allows an analysis of the immunological network and its individual circuits. At the same time, valuable information on the mechanisms of action during adoptive immunotherapy and how best to improve therapeutic protocols is acquired.

Inflammatory infiltrates of experimental mammary cancers

The purpose of this review was to summarize observations on the type and function of inflammatory infiltrates of mouse mammary tumors and to speculate on the underlying mechanisms and the significance of infiltrates to mammary tumor biology. Although the major conclusion is that much more work is needed, certain themes seem to be emerging. The number of infiltrating cells can be very high but is unrelated to biological behavior of the tumors. What seems to be important is the relative contributions of inflammatory cell subsets. In the case of T-cell subsets and NK cells, the infiltrates from tumors of long-term cell lines so far seem uninformative. The general characteristics are similar to those of infiltrates from rapidly proliferating, normal mammary tissues. These characteristics do not correlate with diverse biological behavior or malignant potential. A more informative model appears to be one in which the development of tumors from preneoplastic tissue can be observed. Here our attention is currently focused on NK cells. By contrast, the correlation between activated TAM and metastatic behavior suggests that our transplantable MMT lines may be biologically relevant in the study of infiltrating macrophages. We are especially interested in the role of TAM in the generation of tumor cell variability. Overall, our data indicate that the host infiltrate is another manifestation of both inter- and intra-tumor heterogeneity and, as such, is not simply a response to, but, rather, a part of the tumor ecosystem. Unraveling the cellular and molecular mechanisms that govern the inflammatory cell component of tumors should provide insight into the types of cellular interactions that result in tumor development and progression.

Tumor-derived chemotactic factor(s) from human ovarian carcinoma: evidence for a role in the regulation of macrophage content of neoplastic tissues

Supernatants from freshly disaggregated human ovarian carcinomas maintained in vitro for 24 hr, from primary ovarian carcinoma cultures (4-6 days in culture) and from established ovarian cancer cell lines were examined for chemotactic activity on blood monocytes in blind-well chemotaxis chambers. Tumor-cell culture supernatants induced migration of peripheral blood monocytes across polycarbonate filters with considerable heterogeneity among different tumors. Induction of migration occurred only in the presence of a gradient between the lower and upper compartments of the chamber. Chemotactic activity was characterized by means of supernatants from primary ovarian carcinoma cultures. Chemotactic factor(s) was (were) produced in serum-free conditions and the production was inhibited by emetine but not by mitomycin C. The activity was destroyed by exposure to proteolytic enzymes and by heating at 100 degrees C but was unaffected by RNase, DNase, lipase and exposure to extreme pH values or heating at 56 degrees C. Upon fractionation on Sephadex G 75, the activity eluted as a single peak in the cytochrome C region, corresponding to an apparent molecular weight of about 12 kd. The percentage of macrophages was assessed in 25 freshly disaggregated tumor specimens. Ovarian carcinomas were heterogeneous in their macrophage content with values ranging from 4 to 36%. A significant (r = 0.62; p = 0.00097), though far from absolute, correlation was found between chemotactic activity of culture supernatants and percentage of tumor-associated macrophages. Tumor-derived chemotactic factor(s) could be one of the mechanisms involved in the regulation of the macrophage content of human ovarian carcinomas.

Locomotion and chemotaxis of mononuclear phagocytes

The capacity for locomotion and for chemotaxis is probably very different in monocytes and macrophages from different sources. Numerous techniques have been established for studying the locomotion of these cells. Many of the factors are sparsely documented and the reports are scattered among various cell types. Heterogeneity of locomotion and chemotactic responsiveness is evident when established macrophage lines and mouse peritoneal macrophage are studied. The effects of mononuclear phagocytes and their released products on the locomotion of other cell types are reviewed.

Evaluation of absorption with Limulus amebocyte lysate to remove contaminating endotoxin from interferon and lymphokine preparations

Alpha and beta human interferon (IFN) preparations and lymphokines (supernatants of PHA-stimulated blood lymphocytes) were deliberately contaminated with endotoxin (20 ng/ml) and subsequently rendered endotoxin-free by absorption with Limulus amebocyte lysate (LAL). Absorption with LAL did not appreciably affect the antiviral activity of IFN and lymphokines in 8 experiments and caused a 30-50% reduction in two. The capacity of these agents to stimulate natural killer cell activity and monocyte cytotoxicity was not consistently modified by absorption on LAL. When the chemotactic activity of lymphokine for monocytes was measured, the maximal number of monocytes induced to migrate and the maximal active lymphokine concentration were not affected by absorption with LAL. LAL-treated lymphokines, however, showed a prozone phenomenon, presumably related to the release of chemotaxis inhibitor(s) from the LAL gel.