The specific shapes of capillaries are associated with worse prognosis in patients with invasive breast cancer.

Angiogenesis is considered essential for tumor progression; however, whether histological counting of blood vessel numbers, expressed as microvessel density (MVD), can be a prognostic factor in breast cancer remains controversial. It has been suggested that the specific morphology of blood vessels such as glomeruloid microvascular proliferation (GMP) is associated with clinical parameters. Here, we aimed to clarify the significance of MVD with revised immunohistochemistry and to identify new blood vessel shapes that predict prognosis in breast cancer. Four hundred and eleven primary breast cancer specimens were collected, and the sections were immunohistochemically stained with CD31 (single staining) and CD31 and Collagen IV (double staining). The prognosis of patients was examined based on the MVD value, and the presence of GMP and other blood vessels with other specific shapes. As a result, high MVD value and the presence of GMP were not associated with worse prognosis. By contrast, patients with deep-curved capillaries surrounding tumor cell nests (C-shaped) or excessively branched capillaries near tumor cell nests showed a significantly poor prognosis. The presence of these capillaries was also correlated with clinicopathological parameters such as Ki-67 index. Thus, the morphology of capillaries rather than MVD can be a better indicator of tumor aggressiveness.

SPRED2 Is a Novel Regulator of Autophagy in Hepatocellular Carcinoma Cells and Normal Hepatocytes.

Sprouty-related enabled/vasodilator-stimulated phosphoprotein homology 1 domain containing 2 (SPRED2) is an inhibitor of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway and has been shown to promote autophagy in several cancers. Here, we aimed to determine whether SPRED2 plays a role in autophagy in hepatocellular carcinoma (HCC) cells. The Cancer Genome Atlas (TCGA) Liver Cancer Database showed a negative association between the level of SPRED2 and p62, a ubiquitin-binding scaffold protein that accumulates when autophagy is inhibited. Immunohistochemically, accumulation of p62 was detected in human HCC tissues with low SPRED2 expression. Overexpression of SPRED2 in HCC cells increased the number of autophagosomes and autophagic vacuoles containing damaged mitochondria, decreased p62 levels, and increased levels of light-chain-3 (LC3)-II, an autophagy marker. In contrast, SPRED2 deficiency increased p62 levels and decreased LC3-II levels. SPRED2 expression levels were negatively correlated with translocase of outer mitochondrial membrane 20 (TOM20) expression levels, suggesting its role in mitophagy. Mechanistically, SPRED2 overexpression reduced ERK activation followed by the mechanistic or mammalian target of rapamycin complex 1 (mTORC1)-mediated signaling pathway, and SPRED2 deficiency showed the opposite pattern. Finally, hepatic autophagy was impaired in the liver of SPRED2-deficient mice with hepatic lipid droplet accumulation in response to starvation. These results indicate that SPRED2 is a critical regulator of autophagy not only in HCC cells, but also in hepatocytes, and thus the manipulation of this process may provide new insights into liver pathology.

Requirement of CRAMP for mouse macrophages to eliminate phagocytosed E. coli through an autophagy pathway.

Host-derived antimicrobial peptides play an important role in the defense against extracellular bacterial infections. However, the capacity of antimicrobial peptides derived from macrophages as potential antibacterial effectors against intracellular pathogens remains unknown. In this study, we report that normal (wild-type, WT) mouse macrophages increased their expression of cathelin-related antimicrobial peptide (CRAMP, encoded by Camp) after infection by viable E. coli or stimulation with inactivated E. coli and its product lipopolysaccharide (LPS), a process involving activation of NF-κB followed by protease-dependent conversion of CRAMP from an inactive precursor to an active form. The active CRAMP was required by WT macrophages for elimination of phagocytosed E. coli, with participation of autophagy-related proteins ATG5, LC3-II and LAMP-1, as well as for aggregation of the bacteria with p62 (also known as SQSTM1). This process was impaired in CRAMP-/- macrophages, resulting in retention of intracellular bacteria and fragmentation of macrophages. These results indicate that CRAMP is a critical component in autophagy-mediated clearance of intracellular E. coli by mouse macrophages.

SPRED2: A Novel Regulator of Epithelial-Mesenchymal Transition and Stemness in Hepatocellular Carcinoma Cells.

The downregulation of SPRED2, a negative regulator of the ERK1/2 pathway, was previously detected in human cancers; however, the biological consequence remains unknown. Here, we investigated the effects of SPRED2 loss on hepatocellular carcinoma (HCC) cell function. Human HCC cell lines, expressing various levels of SPRED2 and SPRED2 knockdown, increased ERK1/2 activation. SPRED2-knockout (KO)-HepG2 cells displayed an elongated spindle shape with increased cell migration/invasion and cadherin switching, with features of epithelial-mesenchymal transition (EMT). SPRED2-KO cells demonstrated a higher ability to form spheres and colonies, expressed higher levels of stemness markers and were more resistant to cisplatin. Interestingly, SPRED2-KO cells also expressed higher levels of the stem cell surface markers CD44 and CD90. When CD44+CD90+ and CD44-CD90- populations from WT cells were analyzed, a lower level of SPRED2 and higher levels of stem cell markers were detected in CD44+CD90+ cells. Further, endogenous SPRED2 expression decreased when WT cells were cultured in 3D, but was restored in 2D culture. Finally, the levels of SPRED2 in clinical HCC tissues were significantly lower than those in adjacent non-HCC tissues and were negatively associated with progression-free survival. Thus, the downregulation of SPRED2 in HCC promotes EMT and stemness through the activation of the ERK1/2 pathway, and leads to more malignant phenotypes.

Exosomal Wnt7a from a low metastatic subclone promotes lung metastasis of a highly metastatic subclone in the murine 4t1 breast cancer.

BACKGROUND: Patients with triple-negative breast cancer (TNBC) often have poorer prognosis than those with other subtypes because of its aggressive behaviors. Cancer cells are heterogeneous, and only a few highly metastatic subclones metastasize. Although the majority of subclones may not metastasize, they could contribute by releasing factors that increase the capacity of highly metastatic cells and/or provide a favorable tumor microenvironment (TME). Here, we analyzed the interclonal communication in TNBC which leads to efficient cancer progression, particularly lung metastasis, using the polyclonal murine 4T1 BC model. METHODS: We isolated two 4T1 subclones, LM.4T1 and HM.4T1 cells with a low and a high metastatic potential, respectively, and examined the effects of LM.4T1 cells on the behaviors of HM.4T1 cells using the cell scratch assay, sphere-forming assay, sphere invasion assay, RT-qPCR, and western blotting in vitro. We also examined the contribution of LM.4T1 cells to the lung metastasis of HM.4T1 cells and TME in vivo. To identify a critical factor which may be responsible for the effects by LM.4T1 cells, we analyzed the data obtained from the GEO database. RESULTS: Co-injection of LM.4T1 cells significantly augmented lung metastases by HM.4T1 cells. LM.4T1-derived exosomes promoted the migration and invasion of HM.4T1 cells in vitro, and blocking the secretion of exosome abrogated their effects on HM.4T1 cells. Analyses of data obtained from the GEO database suggested that Wnt7a might be a critical factor responsible for the enhancing effects. In fact, a higher level of Wnt7a was detected in LM.4T1 cells, especially in exosomes, than in HM.4T1 cells, and deletion of Wnt7a in LM.4T1 cells significantly decreased the lung metastasis of HM.4T1 cells. Further, treatment with Wnt7a increased the spheroid formation by HM.4T1 cells via activation of the PI3K/Akt/mTOR signaling pathway. Finally, infiltration of αSMA-positive fibroblasts and angiogenesis was more prominent in tumors of LM.4T1 cells and deletion of Wnt7a in LM.4T1 cells markedly reduced angiogenesis. CONCLUSIONS: We demonstrated, for the first time, that a low metastatic subclone can enhance lung metastasis of highly metastatic subclone via exosomal Wnt7a and propose Wnt7a as a molecular target to treat TNBC patients.

Leukocyte chemotactic receptor Fpr1 protects against aging-related posterior subcapsular cataract formation.

Cataracts are a common consequence of aging; however, pathogenesis remains poorly understood. Here, we observed that after 3 months of age mice lacking the G protein-coupled leukocyte chemotactic receptor Fpr1 (N-formyl peptide receptor 1) began to develop bilateral posterior subcapsular cataracts that progressed to lens rupture and severe degeneration, without evidence of either systemic or local ocular infection or inflammation. Consistent with this, Fpr1 was detected in both mouse and human lens in primary lens epithelial cells (LECs), the only cell type present in the lens; however, expression was confined to subcapsular LECs located along the anterior hemispheric surface. To maximize translucency, LECs at the equator proliferate and migrate posteriorly, then differentiate into lens fiber cells by nonclassical apoptotic signaling, which results in loss of nuclei and other organelles, including mitochondria which are a rich source of endogenous N-formyl peptides. In this regard, denucleation and posterior migration of LECs were abnormal in lenses from Fpr1-/- mice, and direct stimulation of LECs with the prototypic N-formyl peptide agonist fMLF promoted apoptosis. Thus, Fpr1 is repurposed beyond its immunoregulatory role in leukocytes to protect against cataract formation and lens degeneration during aging.

Distinct contributions of cathelin-related antimicrobial peptide (CRAMP) derived from epithelial cells and macrophages to colon mucosal homeostasis.

The cathelin-related antimicrobial peptide CRAMP protects the mouse colon from inflammation, inflammation-associated carcinogenesis, and disrupted microbiome balance, as shown in systemic Cnlp-/- mice (also known as Camp-/- mice). However, the mechanistic basis for the role and the cellular source of CRAMP in colon pathophysiology are ill defined. This study, using either epithelial or myeloid conditional Cnlp-/- mice, demonstrated that epithelial cell-derived CRAMP played a major role in supporting normal development of colon crypts, mucus production, and repair of injured mucosa. On the other hand, myeloid cell-derived CRAMP potently supported colon epithelial resistance to bacterial invasion during acute inflammation with exacerbated mucosal damage and higher rate of mouse mortality. Therefore, a well concerted cooperation of epithelial- and myeloid-derived CRAMP is essential for colon mucosal homeostasis. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

A Critical Role of Formyl Peptide Receptors in Host Defense against Escherichia coli.

Formyl peptide receptors (FPRs, mouse Fprs) belong to the G protein-coupled receptor superfamily and mediate phagocyte migration in response to bacteria- and host-derived chemoattractants; however, knowledge about their in vivo roles in bacterial pathogenesis is limited. In this study, we investigated the role of Fpr1 and Fpr2 in host defense against Escherichia coli infection. In vitro, we found that supernatants from E. coli cultures induced chemotaxis of wild-type (WT) mouse bone marrow-derived neutrophils and that the activity was significantly reduced in cells genetically deficient in either Fpr1 or Fpr2 and was almost absent in cells lacking both receptors. Consistent with this, E. coli supernatants induced chemotaxis and MAPK phosphorylation in HEK293 cells expressing either recombinant Fpr1 or Fpr2 but not untransfected parental cells. WT bone marrow -derived neutrophils could actively phagocytose and kill E. coli, whereas both activities were diminished in cells lacking Fpr1 or Fpr2; again, an additive effect was observed in cells lacking both receptors. In vivo, Fpr1 and Fpr2 deficiency resulted in reduced recruitment of neutrophils in the liver and peritoneal cavity of mice infected with inactivated E. coli Moreover, Fpr1-/- and Fpr2-/- mice had significantly increased mortality compared with WT mice after i.p. challenge with a virulent E. coli clinical isolate. These results indicate a critical role of Fprs in host defense against E. coli infection.

Crosstalk between Cancer Cells and Fibroblasts for the Production of Monocyte Chemoattractant Protein-1 in the Murine 4T1 Breast Cancer.

The chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2) is shown to promote the progression of breast cancer. We previously identified cancer cell-derived granulocyte-macrophage colony-stimulating factor (GM-CSF) as a potential regulator of MCP-1 production in the murine 4T1 breast cancer, but it played a minimum role in overall MCP-1 production. Here, we evaluated the crosstalk between 4T1 cells and fibroblasts. When fibroblasts were co-cultured with 4T1 cells or stimulated with the culture supernatants of 4T1 cells (4T1-sup), MCP-1 production by fibroblasts markedly increased. 4T1 cells expressed mRNA for platelet-derived growth factor (PDGF)-a, b and c, and the PDGF receptor inhibitor crenolanib almost completely inhibited 4T1-sup-induced MCP-1 production by fibroblasts. However, PDGF receptor antagonists failed to reduce MCP-1 production in tumor-bearing mice. Histologically, 4T1 tumors contained a small number of αSMA-positive fibroblasts, and Mcp-1 mRNA was mainly associated with macrophages, especially those surrounding necrotic lesions on day 14, by in situ hybridization. Thus, although cancer cells have the capacity to crosstalk with fibroblasts via PDGFs, this crosstalk does not play a major role in MCP-1 production or cancer progression in this model. Unraveling complex crosstalk between cancer cells and stromal cells will help us identify new targets to help treat breast cancer patients.

PolyI:C suppresses TGF-ß1-induced Akt phosphorylation and reduces the motility of A549 lung carcinoma cells.

BACKGROUNDS: Epithelial mesenchymal transition (EMT) is a critical process involved in the invasion and metastasis of cancer, including lung cancer (LC). Transforming growth factor (TGF)-ß is one of factors capable of inducing EMT. Polyinosinic-polycytidylic acid (polyI:C), a synthetic agonist for toll-like receptor (TLR) 3, can enhance immune responses and has been used as an adjuvant for cancer vaccines; however, it remains unclear whether it influences other process, such as EMT. In the present study, we examined the effects of polyI:C on TGF-ß-treated A549 human LC cells. METHODS AND RESULTS: By in vitro cell proliferation assay, polyI:C showed no effect on the growth of A549 cells treated with TGF-ß1 at the concentration range up to 10 µg/ml; however, it markedly suppressed the motility in a cell scratch and a cell invasion assay. By Western blotting, polyI:C dramatically decreased TGF-ß1-induced Ak strain transforming (Akt) phosphorylation and increased phosphatase and tensin homologue (PTEN) expression without affecting the Son of mothers against decapentaplegic (Smad) 3 phosphorylation or the expression level of E-cadherin, N-cadherin or Snail, indicating that polyI:C suppressed cell motility independently of the 'cadherin switching'. The Akt inhibitor perifosine inhibited TGF-ß1-induced cell invasion, and the PTEN-specific inhibitor VO-OHpic appeared to reverse the inhibitory effect of polyI:C. CONCLUSION: PolyI:C has a novel function to suppress the motility of LC cells undergoing EMT by targeting the phosphatidylinositol 3-kinase/Akt pathway partly via PTEN and may prevent or reduce the metastasis of LC cells.

The Critical Role of the Antimicrobial Peptide LL-37/ CRAMP in Protection of Colon Microbiota Balance, Mucosal Homeostasis, Anti-Inflammatory Responses, and Resistance to Carcinogenesis.

Mouse cathelin-related antimicrobial peptide (CRAMP) and its homologue human cathelicidin (LL-37) play active roles in innate immune responses, angiogenesis, and wound healing. In addition, LL-37/CRAMP fends off microbes and protects against infections in the colon, where the epithelium is exposed to myriad of enteric pathogens. It is increasingly recognized that LL-37/CRAMP maintains colon mucosal barrier integrity, shapes the composition of microbiota, and protects the host from tumorigenesis. In this review, we discuss the importance of LL-37/CRAMP in the homeostasis of the host, with novel findings derived from mice deficient in CRAMP that support the proposition for this natural antimicrobial peptide and an immune modulator as a drug lead for therapeutic development.

The Antimicrobial Peptide CRAMP Is Essential for Colon Homeostasis by Maintaining Microbiota Balance.

Commensal bacteria are critical for physiological functions in the gut, and dysbiosis in the gut may cause diseases. In this article, we report that mice deficient in cathelin-related antimicrobial peptide (CRAMP) were defective in the development of colon mucosa and highly sensitive to dextran sulfate sodium (DSS)-elicited colitis, as well as azoxymethane-mediated carcinogenesis. Pretreatment of CRAMP-/- mice with antibiotics markedly reduced the severity of DSS-induced colitis, suggesting CRAMP as a limiting factor on dysbiosis in the colon. This was supported by observations that wild-type (WT) mice cohoused with CRAMP-/- mice became highly sensitive to DSS-induced colitis, and the composition of fecal microbiota was skewed by CRAMP deficiency. In particular, several bacterial species that are typically found in oral microbiota, such as Mogibacterium neglectum, Desulfovibrio piger, and Desulfomicrobium orale, were increased in feces of CRAMP-/- mice and were transferred to WT mice during cohousing. When littermates of CRAMP+/- parents were examined, the composition of the fecal microbiota of WT pups and heterozygous parents was similar. In contrast, although the difference in fecal microbiota between CRAMP-/- and WT pups was small early on after weaning and single mouse housing, there was an increasing divergence with prolonged single housing. These results indicate that CRAMP is critical in maintaining colon microbiota balance and supports mucosal homeostasis, anti-inflammatory responses, and protection from carcinogenesis.

Elastin and collagen IV double staining: A refined method to detect blood vessel invasion in breast cancer.

Blood vessel invasion (BVI) is a prognostic indicator in various cancers. Elastic stain, which highlights blood vessel walls, is commonly used to detect BVI. In the breast, however, its diagnostic usefulness is limited because it also highlights some intraductal carcinoma components, which often mimic BVI. In this study, we aimed to improve BVI detection in breast cancer and developed a double staining: Victoria blue for elastin and immunohistochemistry for collagen IV. Collagen IV fibers were retained along the basement membranes of intraductal carcinoma components, whereas they were rearranged or lost in BVI. From these observations, we defined BVI as the presence of tumor cells inside an elastic ring with a rearrangement or loss of collagen IV fibers. Using these criteria, we found BVI in 148 cases (49%) among 304 cases of primary operable invasive breast carcinoma, and the presence of BVI correlated significantly with poor prognosis. By contrast, we detected BVI in 94 cases (31%) or 14 cases (5%) by elastic van Gieson or CD31 immunostaining among the same cases, respectively, with no statistically significant association with prognosis. Thus, elastin and collagen IV double staining facilitates the detection of BVI in breast cancer and is useful to predict prognosis.

Deficiency in Fpr2 results in reduced numbers of Lin-cKit+Sca1+ myeloid progenitor cells.

The Lin-c-Kit+ Sca-1+ cell population in the bone marrow (BM) serves as the direct precursor for differentiation of myeloid cells. In this study, we report that deficiency in Fpr2, a G protein-coupled chemoattractant receptor in mice, is associated with reduced BM nucleated cells, including CD31+Ly6C+ (granulocytes and monocytes), CD31-/Ly6Cint (granuloid cells), and CD31-/Ly6Chigh (predominantly monocytes) cells. In particular, the number of Lin-c-Kit+Sca-1+ (LKS) cells was reduced in Fpr2-/- mouse BM. This was supported by observations of the reduced incorporation of intraperitoneally injected bromodeoxyuridine by cells in the c-Kit+ population from Fpr2-/- mouse BM. Purified c-Kit+ cells from Fpr2-/- mice showed reduced expansion when cultured in vitro with stem cell factor (SCF). SCF/c-Kit-mediated phosphorylation of P38, STAT1, Akt (Thr-308), and Akt (Ser-473) was also significantly reduced in c-Kit+ cells from Fpr2-/- mice. Furthermore, Fpr2 agonists enhanced SCF-induced proliferation of c-Kit+ cells. Colony-forming unit assays revealed that CFU-granulocyte-macrophage formation of BM cells from Fpr2-/- mice was significantly reduced. After heat-inactivated bacterial stimulation in the airway, the expansion of c-kit+ Sca-1+ cells in BM and recruitment of Ly6G+ cells to the lungs and CD11b+Ly6C+TNFα+ cells to the spleen of Fpr2-/- mice was significantly reduced. These results demonstrate an important role for Fpr2 in the development of myeloid lineage precursors in mouse BM.

SOCS3 overexpression in T cells ameliorates chronic airway obstruction in a murine heterotopic tracheal transplantation model.

PURPOSE: Suppressor of cytokine signaling-3 (SOCS3) is a negative feedback inhibitor of cytokine signaling with T-cell-mediated immunosuppressive effects on obliterative bronchiolitis (OB). In this study, we aimed to investigate the impact of T-cell-specific overexpression of SOCS3 using a murine heterotopic tracheal transplantation (HTT) model. METHODS: Tracheal allografts from BALB/c mice were subcutaneously transplanted into wild-type C57BL/6J (B6; WT) mice and SOCS3 transgenic B6 (SOCS3TG) mice. Tracheal allografts were analyzed by immunohistochemistry and quantitative polymerase chain reaction assays at days 7 and 21. RESULTS: At day 21, allografts in SOCS3TG mice showed significant amelioration of airway obstruction and epithelial loss compared with allografts in WT mice. The intragraft expression of IFN-γ and CXCL10 was suppressed, while that of IL-4 was enhanced in SOCS3TG mice at day 7. The T-bet levels were lower in SOCS3TG allografts than in WT allografts at day 7. CONCLUSION: We revealed that the overexpression of SOCS3 in T cells effectively ameliorates OB development in a murine HTT model by inhibiting the Th1 phenotype in the early phase. Our results suggest that the regulation of the T-cell response, through the modulation of SOCS expression, has potential as a new therapeutic strategy for chronic lung allograft dysfunction.

Cancer Cell-Derived Granulocyte-Macrophage Colony-Stimulating Factor Is Dispensable for the Progression of 4T1 Murine Breast Cancer.

We previously reported that 4T1 murine breast cancer cells produce GM-CSF that up-regulates macrophage expression of several cancer promoting genes, including Mcp-1/Ccl2, Ccl17 and Rankl, suggesting a critical role of cancer cell-derived GM-CSF in cancer progression. Here, we attempted to define whether 4T1 cell-derived GM-CSF contributes to the expression of these genes by 4T1tumors, and their subsequent progression. Intraperitoneal injection of anti-GM-CSF neutralizing antibody did not decrease the expression of Mcp-1, Ccl17 or Rankl mRNA by 4T1 tumors. To further examine the role of cancer cell-derived GM-CSF, we generated GM-CSF-deficient 4T1 cells by using the Crisper-Cas9 system. As previously demonstrated, 4T1 cells are a mixture of cells and cloning of cells by itself significantly reduced tumor growth and lung metastasis. By contrast, GM-CSF-deficiency did not affect tumor growth, lung metastasis or the expression of these chemokine and cytokine genes in tumor tissues. By in-situ hybridization, the expression of Mcp-1 mRNA was detected in both F4/80-expressing and non-expressing cells in tumors of GM-CSF-deficient cells. These results indicate that cancer cell-derived GM-CSF is dispensable for the tuning of the 4T1 tumor microenvironment and the production of MCP-1, CCL17 or RANKL in the 4T1 tumor microenvironment is likely regulated by redundant mechanisms.

Integrative DNA, RNA, and protein evidence connects TREML4 to coronary artery calcification.

Coronary artery calcification (CAC) is a heritable and definitive morphologic marker of atherosclerosis that strongly predicts risk for future cardiovascular events. To search for genes involved in CAC, we used an integrative transcriptomic, genomic, and protein expression strategy by using next-generation DNA sequencing in the discovery phase with follow-up studies using traditional molecular biology and histopathology techniques. RNA sequencing of peripheral blood from a discovery set of CAC cases and controls was used to identify dysregulated genes, which were validated by ClinSeq and Framingham Heart Study data. Only a single gene, TREML4, was upregulated in CAC cases in both studies. Further examination showed that rs2803496 was a TREML4 cis-eQTL and that the minor allele at this locus conferred up to a 6.5-fold increased relative risk of CAC. We characterized human TREML4 and demonstrated by immunohistochemical techniques that it is localized in macrophages surrounding the necrotic core of coronary plaques complicated by calcification (but not in arteries with less advanced disease). Finally, we determined by von Kossa staining that TREML4 colocalizes with areas of microcalcification within coronary plaques. Overall, we present integrative RNA, DNA, and protein evidence implicating TREML4 in coronary artery calcification. Our findings connect multimodal genomics data with a commonly used clinical marker of cardiovascular disease.

Regulation of inflammation by members of the formyl-peptide receptor family.

Inflammation is associated with a variety of diseases. The hallmark of inflammation is leukocyte infiltration at disease sites in response to pathogen- or damage-associated chemotactic molecular patterns (PAMPs and MAMPs), which are recognized by a superfamily of seven transmembrane, Gi-protein-coupled receptors (GPCRs) on cell surface. Chemotactic GPCRs are composed of two major subfamilies: the classical GPCRs and chemokine GPCRs. Formyl-peptide receptors (FPRs) belong to the classical chemotactic GPCR subfamily with unique properties that are increasingly appreciated for their expression on diverse host cell types and the capacity to interact with a plethora of chemotactic PAMPs and MAMPs. Three FPRs have been identified in human: FPR1-FPR3, with putative corresponding mouse counterparts. FPR expression was initially described in myeloid cells but subsequently in many non-hematopoietic cells including cancer cells. Accumulating evidence demonstrates that FPRs possess multiple functions in addition to controlling inflammation, and participate in the processes of many pathophysiologic conditions. They are not only critical mediators of myeloid cell trafficking, but are also implicated in tissue repair, angiogenesis and protection against inflammation-associated tumorigenesis. A series recent discoveries have greatly expanded the scope of FPRs in host defense which uncovered the essential participation of FPRs in step-wise trafficking of myeloid cells including neutrophils and dendritic cells (DCs) in host responses to bacterial infection, tissue injury and wound healing. Also of great interest is the FPRs are exploited by malignant cancer cells for their growth, invasion and metastasis. In this article, we review the current understanding of FPRs concerning their expression in a vast array of cell types, their involvement in guiding leukocyte trafficking in pathophysiological conditions, and their capacity to promote the differentiation of immune cells, their participation in tumor-associated inflammation and cancer progression. The close association of FPRs with human diseases and cancer indicates their potential as targets for the development of therapeutics.

The production of monocyte chemoattractant protein-1 (MCP-1)/CCL2 in tumor microenvironments.

Infiltration of leukocytes is one of the hallmarks of the inflammatory response. Among the leukocyte populations, neutrophils are the first to infiltrate, followed by monocytes and lymphocytes, suggesting the presence of mediators that specifically recruit these cell types. Cytokine-like chemoattractants with monocyte chemotactic activity, such as lymphocyte-derived chemotactic factor (LDCF) or tumor-derived chemotactic factor (TDCF), were reported as molecules that could play a critical role in the recruitment of monocytes into sites of immune responses or tumors; however, their identities remained unclear. In the 1980s, researchers began to test the hypothesis that leukocyte chemotactic activity is a part of the wider activities exhibited by cytokines, such as interleukin-1 (IL-1). In 1987, we demonstrated, for the first time, the presence of a cytokine like chemoattractant with cell type-specificity (now known as the chemokine interleukin-8 or CXC chemokine ligand 8) that was different from IL-1. This led us to the purification of the second such molecule with monocyte chemotactic activity. This monocyte chemoattractant was found identical to the previously described LDCF or TDCF, and termed monocyte chemoattractant protein-1 (MCP-1). Isolation of MCP-1 created a revolution in not only inflammation but also cancer research that continues today, and MCP-1 has become a molecular target to treat patients with many diseases. In this review, I will first describe a history associated with the discovery of MCP-1 and then discuss complex mechanisms regulating MCP-1 production in tumor microenvironments.