Inhibition of ron kinase blocks conversion of micrometastases to overt metastases by boosting antitumor immunity

MSLN induced EMT, cancer stem cell traits and chemotherapy resistance of pancreatic cancer cells

Chemoresistance is one of the main reasons for poor prognosis of pancreatic cancer. The effects of mesothelin (MSLN) on chemoresistance in pancreatic cancer are still unclear. We aim to investigate potential roles of MSLN in chemoresistance and its relationship with proliferation, epithelial-mesenchymal transition (EMT) and cancer stemness of pancreatic cancer cells. Human pancreatic cancer cell lines ASPC-1 and Mia PaCa-2 with high and low expression of MSLN, respectively, were selected. The ASPC-1 with MSLN knockout (KO) and Mia PaCa-2 of MSLN overexpression (OE) were generated. The effects of MSLN on cell phenotypes, expression of EMT-related markers, clone formation, tumor sphere formation, and pathologic role of MSLN in tumorigenesis were detected. Sensitivity of tumor cells to gemcitabine was evaluated. The results showed that adhesion, proliferation, migration and invasion were decreased significantly in ASPC-1 with MSLN KO, whereas increased significantly in Mia PaCa-2 with MSLN OE. The size and the number of clones and tumor spheres were decreased in ASPC-1 with MSLN KO, and increased in Mia PaCa-2 with MSLN OE. In xenograft model, tumor volume was decreased (tumor grew slower) in MSLN KO group compared to control group, while increased in MSLN OE group. Mia PaCa-2 with MSLN OE had a higher IC50 of gemcitabine, while ASPC-1 with MSLN KO had a lower IC50. We concluded that MSLN could induce chemoresistance by enhancing migration, invasion, EMT and cancer stem cell traits of pancreatic cancer cells. Targeting MSLN could represent a promising therapeutic strategy for reversing EMT and chemoresistance in pancreatic cancer cells.

A network map of macrophage-stimulating protein (MSP) signaling

Macrophage-stimulating protein (MSP), a serum-derived growth factor belonging to the plasminogen-related kringle domain family, is mainly produced by the liver and released into the blood. MSP is the only known ligand for RON ("Recepteur d'Origine Nantais", also known as MST1R), which is a member of the receptor tyrosine kinase (RTK) family. MSP is associated with many pathological conditions, including cancer, inflammation, and fibrosis. Activation of the MSP/RON system regulates main downstream signaling pathways, including phosphatidylinositol 3-kinase/ AKT serine/threonine kinase/ (PI3-K/AKT), mitogen-activated protein kinases (MAPK), c-Jun N-terminal kinase (JNK) & Focal adhesion kinase (FAK). These pathways are mainly involved in cell proliferation, survival, migration, invasion, angiogenesis & chemoresistance. In this work, we created a pathway resource of signaling events mediated by MSP/RON considering its contribution to diseases. We provide an integrated pathway reaction map of MSP/RON that is composed of 113 proteins and 26 reactions based on the curation of data from the published literature. The consolidated pathway map of MSP/RON mediated signaling events contains seven molecular associations, 44 enzyme catalysis, 24 activation/inhibition, six translocation events, 38 gene regulation events, and forty-two protein expression events. The MSP/RON signaling pathway map can be freely accessible through the WikiPathways Database URL: https://classic.wikipathways.org/index.php/Pathway:WP5353 .

The environmental carcinogen benzo[a]pyrene regulates epigenetic reprogramming and metabolic rewiring in a two-stage mouse skin carcinogenesis model

Non-melanoma skin cancer (NMSC) is the most common cancer in the world. Environmental exposure to carcinogens is one of the major causes of NMSC initiation and progression. In the current study, we utilized a two-stage skin carcinogenesis mouse model generated by sequential exposure to cancer-initiating agent benzo[a]pyrene (BaP) and promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA), to study epigenetic, transcriptomic and metabolic changes at different stages during the development of NMSC. BaP/TPA caused significant alterations in DNA methylation and gene expression profiles in skin carcinogenesis, as evidenced by DNA-seq and RNA-seq analysis. Correlation analysis between differentially expressed genes and differentially methylated regions found that the mRNA expression of oncogenes leucine rich repeat LGI family member 2 (Lgi2), kallikrein-related peptidase 13 (Klk13) and SRY-Box transcription factor (Sox5) are correlated with the promoter CpG methylation status, indicating BaP/TPA regulates these oncogenes through regulating their promoter methylation at different stages of NMSC. Pathway analysis identified that the modulation of macrophage-stimulating protein-recepteur d'origine nantais and high-mobility group box 1 signaling pathways, superpathway of melatonin degradation, melatonin degradation 1, sirtuin signaling and actin cytoskeleton signaling pathways are associated with the development of NMSC. The metabolomic study showed BaP/TPA regulated cancer-associated metabolisms like pyrimidine and amino acid metabolisms/metabolites and epigenetic-associated metabolites, such as S-adenosylmethionine, methionine and 5-methylcytosine, indicating a critical role in carcinogen-mediated metabolic reprogramming and its consequences on cancer development. Altogether, this study provides novel insights integrating methylomic, transcriptomic and metabolic-signaling pathways that could benefit future skin cancer treatment and interception studies.

Dual identity of tumor-associated macrophage in regulated cell death and oncotherapy

Tumor-associated macrophage (TAM) affects the intrinsic properties of tumor cells and the tumor microenvironment (TME), which can stimulate tumor cell proliferation, migration, and genetic instability, and macrophage diversity includes the diversity of tumors with different functional characteristics. Macrophages are now a central drug target in various diseases, especially in the TME, which, as "tumor promoters" and "immunosuppressors", have different responsibilities during tumor development and accompany by significant dynamic alterations in various subpopulations. Remodelling immunosuppression of TME and promotion of pre-existing antitumor immune responses is critical by altering TAM polarization, which is relevant to the efficacy of immunotherapy, and uncovering the exact mechanism of action of TAMs and identifying their specific targets is vital to optimizing current immunotherapies. Hence, this review aims to reveal the triadic interactions of macrophages with programmed death and oncotherapy, and to integrate certain relationships in cancer treatment.

Kinase inhibitors: Opportunities for small molecule anticancer immunotherapies

As the fifth pillar of cancer treatment, immunotherapy has dramatically changed the paradigm of therapeutic strategies by focusing on the host's immune system. In the long road of immunotherapy development, the identification of immune-modulatory effects for kinase inhibitors opened a new chapter in this therapeutic approach. These small molecule inhibitors not only directly eradicate tumors by targeting essential proteins of cell survival and proliferation but can also drive immune responses against malignant cells. This review summarizes the current standings and challenges of kinase inhibitors in immunotherapy, either as a single agent or in a combined modality.

An Introduction and Overview of RON Receptor Tyrosine Kinase Signaling

RON is a receptor tyrosine kinase (RTK) of the MET receptor family that is canonically involved in mediating growth and inflammatory signaling. RON is expressed at low levels in a variety of tissues, but its overexpression and activation have been associated with malignancies in multiple tissue types and worse patient outcomes. RON and its ligand HGFL demonstrate cross-talk with other growth receptors and, consequentially, positions RON at the intersection of numerous tumorigenic signaling programs. For this reason, RON is an attractive therapeutic target in cancer research. A better understanding of homeostatic and oncogenic RON activity serves to enhance clinical insights in treating RON-expressing cancers.

Tailoring therapies to counter the divergent immune landscapes of breast cancer

Breast cancer remains a significant clinical concern affecting millions of women worldwide. Immunotherapy is a rapidly growing drug class that has revolutionized cancer treatment but remains marginally successful in breast cancer. The success of immunotherapy is dependent on the baseline immune responses as well as removing the brakes off pre-existing anti-tumor immunity. In this review, we summarize the different types of immune microenvironment observed in breast cancer as well as provide approaches to target these different immune subtypes. Such approaches have demonstrated pre-clinical success and are currently under clinical evaluation. The impact of combination of these approaches with already approved chemotherapies and immunotherapies may improve patient outcome and survival.

Diabetes mellitus impacts on expression of DNA mismatch repair protein PMS2 and tumor microenvironment in pancreatic ductal adenocarcinoma

AIMS/INTRODUCTION

The mismatch repair (MMR) protein recognizes DNA replication errors and plays an important role in tumorigenesis, including pancreatic ductal adenocarcinoma (PDAC). Although PMS2, a MMR protein, is degraded under oxidative stress, the effects of diabetes are still unclear. Herein, we focused on whether diabetes affected MMR protein expression in PDAC.

MATERIALS AND METHODS

Tissues from 61 surgically resected PDAC subjects were clinicopathologically analyzed. Immunohistochemical analysis was performed for MMR protein expression, oxidative stress, and immune cell infiltration. The change of MMR protein expression was assessed in PDAC cell lines under stimulation with 25 mM glucose and 500 μM palmitic acid. Survival curves were analyzed by the Kaplan-Meier method with the log-rank test.

RESULTS

Diabetes complicated with dyslipidemia significantly decreased the expression of PMS2 in PDAC tissues with an inverse correlation with the degree of oxidative stress. Palmitic acid combined with high glucose induced degradation of PMS2 protein, enhancing oxidative stress in vitro. CD8⁺ T-cell infiltration was associated with a short duration of type 2 diabetes (≤4 years) and a low expression of PMS2 in PDAC tissues, while CD163⁺ tumor-associated macrophage infiltration was increased with a long duration of diabetes (>4 years). A short duration of diabetes exhibited a better prognosis than nondiabetic subjects with PDAC (P < 0.05), while a long duration of diabetes had a worse prognosis (P < 0.05).

CONCLUSIONS

The different phases of diabetes have a major impact on PDAC by altering PMS2 expression and the tumor immune microenvironment, which can be targeted by an immune checkpoint inhibitor.

RON (MST1R) and HGFL (MST1) Co-Overexpression Supports Breast Tumorigenesis through Autocrine and Paracrine Cellular Crosstalk

BACKGROUND

Aberrant RON signaling is present in numerous cancers including breast cancer. Evidence suggests that the ligand, hepatocyte growth factor-like (HGFL), is also overexpressed in breast cancer. RON (MST1R) and HGFL (MST1) genes are located on human chromosome 3 and mouse chromosome 9 respectively and are found near each other in both species. Based on co-expression patterns, we posited that RON and HGFL are co-regulated and that coordinate upregulation drives aggressive tumorigenesis.

METHODS

Mouse models were used to establish the functional significance of RON and HGFL co-overexpression on the activation of tumor cells and tumor-associated macrophages in breast cancer. TCGA and METABRIC gene expression and alteration data were used to query the relationships between MST1R and MST1 in breast cancer.

RESULTS

In tumor models, physiologic sources of HGFL modestly improve Arginase-1+ (M2) macrophage recruitment to the tumor proper. Tumor-cell produced HGFL functions in autocrine to sustain tumor cell RON activation and MAPK-dependent secretion of chemotactic factors and in paracrine to activate RON on macrophages and to promote breast cancer stem cell self-renewal. In silico analyses support that RON and HGFL are co-expressed across virtually all cancer types including breast cancer and that common genomic alterations do not appear to be drivers of RON/HGFL co-overexpression.

CONCLUSIONS

Co-overexpression of RON and HGFL in breast cancer cells (augmented by physiologic sources of HGFL) promotes tumorigenesis through autocrine-mediated RON activation/RON-dependent secretome changes and paracrine activation of macrophage RON to promote breast cancer stem cell self-renewal.

The MST1R/RON Tyrosine Kinase in Cancer: Oncogenic Functions and Therapeutic Strategies

Simple Summary

MST1R/RON receptor tyrosine kinase is a highly conserved transmembrane protein present on epithelial cells, macrophages, and recently identified in a T-cell subset. RON activation attenuates inflammation in healthy tissue. Interestingly, it is overexpressed in several epithelial neoplasms with increasing levels of expression associated with worse outcomes. Though the mechanisms involved are still under investigation, RON is involved in carcinogenesis via immune modulation of the immune tumor microenvironment, activation of numerous oncogenic pathways, and is protective under cellular stress. Alternatively, inhibition of RON abrogates tumor progression in both animal and human tissue models. Given this, RON is a targetable protein of great interest for cancer treatment. Here, we review RON’s function in tissue inflammation and cancer progression, and review cancer clinical trials to date that have used agents targeting RON signaling.

Abstract

The MST1R/RON receptor tyrosine kinase is a homologue of the more well-known MET receptor. Like MET, RON orchestrates cell signaling pathways that promote oncogenesis and enable cancer cell survival; however, it has a more unique role in the regulation of inflammation. RON was originally described as a transmembrane receptor expressed on tissue resident macrophages and various epithelial cells. RON is overexpressed in a variety of cancers and its activation modifies multiple signaling pathways with resultant changes in epithelial and immune cells which together modulate oncogenic phenotypes. While several RON isoforms have been identified with differences in structure, activation, and pathway regulation, increased RON expression and/or activation is consistently associated with worse outcomes. Tyrosine kinase inhibitors targeting RON have been developed, making RON an actionable therapeutic target.

Macrophage-mediated RON signaling supports breast cancer growth and progression through modulation of IL-35

Tumor associated macrophages (TAMs) play a major role in regulating mammary tumor growth and in directing the responses of tumor infiltrating leukocytes in the microenvironment. However, macrophage-specific mechanisms regulating the interactions of macrophages with tumor cells and other leukocytes that support tumor progression have not been extensively studied. In this study, we show that the activation of the RON receptor tyrosine kinase signaling pathway specifically in macrophages supports breast cancer growth and metastasis. Using clinically relevant murine models of breast cancer, we demonstrate that loss of macrophage RON expression results in decreases in mammary tumor cell proliferation, survival, cancer stem cell self-renewal, and metastasis. Macrophage RON signaling modulates these phenotypes via direct effects on the tumor proper and indirectly by regulating leukocyte recruitment including macrophages, T-cells, and B-cells in the mammary tumor microenvironment. We further show that macrophage RON expression regulates the macrophage secretome including IL-35 and other immunosuppressive factors. Overall, our studies implicate activation of RON signaling in macrophages as a key player in supporting a thriving mammary pro-tumor microenvironment through novel mechanisms including the augmentation of tumor cell properties through IL-35.

Blocking Short-Form Ron Eliminates Breast Cancer Metastases through Accumulation of Stem-Like CD4+ T Cells That Subvert Immunosuppression

Immunotherapy has potential to prevent and treat metastatic breast cancer, but strategies to enhance immune-mediated killing of metastatic tumors are urgently needed. We report that a ligand-independent isoform of Ron kinase (SF-Ron) is a key target to enhance immune infiltration and eradicate metastatic tumors. Host-specific deletion of SF-Ron caused recruitment of lymphocytes to micrometastases, augmented tumor-specific T-cell responses, and nearly eliminated breast cancer metastasis in mice. Lack of host SF-Ron caused stem-like TCF1+ CD4+ T cells with type I differentiation potential to accumulate in metastases and prevent metastatic outgrowth. There was a corresponding increase in tumor-specific CD8+ T cells, which were also required to eliminate lung metastases. Treatment of mice with a Ron kinase inhibitor increased tumor-specific CD8+ T cells and protected from metastatic outgrowth. These data provide a strong preclinical rationale to pursue small-molecule Ron kinase inhibitors for the prevention and treatment of metastatic breast cancer.

SIGNIFICANCE

The discovery that SF-Ron promotes antitumor immune responses has significant clinical implications. Therapeutic antibodies targeting full-length Ron may not be effective for immunotherapy; poor efficacy of such antibodies in trials may be due to their inability to block SF-Ron. Our data warrant trials with inhibitors targeting SF-Ron in combination with immunotherapy. This article is highlighted in the In This Issue feature, p. 2945.

Tumor cell intrinsic RON signaling suppresses innate immune responses in breast cancer through inhibition of IRAK4 signaling

Increasing evidence suggests that cancer cells require both alterations in intrinsic cellular processes and the tumor microenvironment for tumor establishment, growth, and progression to metastatic disease. Despite this, knowledge of tumor-cell intrinsic molecular mechanisms controlling both tumor cell processes as well as the tumor microenvironment is limited. In this study, we provide evidence demonstrating the novel role of RON signaling in regulating breast cancer initiation, progression, and metastasis through modulation of tumor cell intrinsic processes and the tumor microenvironment. Using clinically relevant models of breast cancer, we show that RON signaling in the mammary epithelial tumor cells promotes tumor cell survival and proliferation as well as an immunopermissive microenvironment associated with decreased M1 macrophage, natural killer (NK) cell, and CD8+ T cell recruitment. Moreover, we demonstrate that RON signaling supports these phenotypes through novel mechanisms involving suppression of IRAK4 signaling and inhibition of type I Interferons. Our studies indicate that activation of RON signaling within breast cancer cells promotes tumor cell intrinsic growth and immune evasion which support breast cancer progression and highlight the role of targeting RON signaling as a potential therapeutic strategy against breast cancer.

Metastasis-Initiating Cells and Ecosystems

Metastasis is initiated and sustained through therapy by cancer cells with stem-like and immune-evasive properties, termed metastasis-initiating cells (MIC). Recent progress suggests that MICs result from the adoption of a normal regenerative progenitor phenotype by malignant cells, a phenotype with intrinsic programs to survive the stresses of the metastatic process, undergo epithelial-mesenchymal transitions, enter slow-cycling states for dormancy, evade immune surveillance, establish supportive interactions with organ-specific niches, and co-opt systemic factors for growth and recurrence after therapy. Mechanistic understanding of the molecular mediators of MIC phenotypes and host tissue ecosystems could yield cancer therapeutics to improve patient outcomes. SIGNIFICANCE: Understanding the origins, traits, and vulnerabilities of progenitor cancer cells with the capacity to initiate metastasis in distant organs, and the host microenvironments that support the ability of these cells to evade immune surveillance and regenerate the tumor, is critical for developing strategies to improve the prevention and treatment of advanced cancer. Leveraging recent progress in our understanding of the metastatic process, here we review the nature of MICs and their ecosystems and offer a perspective on how this knowledge is informing innovative treatments of metastatic cancers.

Autophagy and Cancer Dormancy

Metastasis and relapse account for the great majority of cancer-related deaths. Most metastatic lesions are micro metastases that have the capacity to remain in a non-dividing state called “dormancy” for months or even years. Commonly used anticancer drugs generally target actively dividing cancer cells. Therefore, cancer cells that remain in a dormant state evade conventional therapies and contribute to cancer recurrence. Cellular and molecular mechanisms of cancer dormancy are not fully understood. Recent studies indicate that a major cellular stress response mechanism, autophagy, plays an important role in the adaptation, survival and reactivation of dormant cells. In this review article, we will summarize accumulating knowledge about cellular and molecular mechanisms of cancer dormancy, and discuss the role and importance of autophagy in this context.

Clinical Potential of Kinase Inhibitors in Combination with Immune Checkpoint Inhibitors for the Treatment of Solid Tumors

Oncogenic kinases contribute to immunosuppression and modulate the tumor microenvironment in solid tumors. Increasing evidence supports the fundamental role of oncogenic kinase signaling networks in coordinating immunosuppressive tumor microenvironments. This has led to numerous studies examining the efficacy of kinase inhibitors in inducing anti-tumor immune responses by increasing tumor immunogenicity. Kinase inhibitors are the second most common FDA-approved group of drugs that are deployed for cancer treatment. With few exceptions, they inevitably lead to intrinsic and/or acquired resistance, particularly in patients with metastatic disease when used as a monotherapy. On the other hand, cancer immunotherapies, including immune checkpoint inhibitors, have revolutionized cancer treatment for malignancies such as melanoma and lung cancer. However, key hurdles remain to successfully incorporate such therapies in the treatment of other solid cancers. Here, we review the recent literature on oncogenic kinases that regulate tumor immunogenicity, immune suppression, and anti-tumor immunity. Furthermore, we discuss current efforts in clinical trials that combine kinase inhibitors and immune checkpoint inhibitors to treat breast cancer and other solid tumors.

Emerging strategies for treating metastasis

The systemic spread of tumor cells is the ultimate cause of the majority of deaths from cancer, yet few successful therapeutic strategies have emerged to specifically target metastasis. Here we discuss recent advances in our understanding of tumor-intrinsic pathways driving metastatic colonization and therapeutic resistance, as well as immune activating strategies to target metastatic disease. We focus on therapeutically exploitable mechanisms, promising strategies in preclinical and clinical development, and emerging areas with potential to become innovative treatments.

Revealing the link between macrophage in microenvironment of osteosarcoma and poor prognosis by utilizing the Integrated analysis

OBJECTIVES

Osteosarcoma (OS) is the most common type of primary malignant bone tumor, The effect of tumor microenvironment components on OS oncogenesis remains unknown.

METHODS

To investigate the function of immune cells in osteosarcoma, we provided a text-based GMT (Gene Matrix Transposed) file in which each line defines one of lm22 with their markers. We used STRING to draw DEG's PPI network and selected hub genes and modules. Then, survival analysis was conducted to hub genes. We identified 10,390 common genes, and identified 218 DEGs based on the combined t-value and Z scores.

RESULTS

The KEGG and GSEA enrichment analysis showed that macrophages are significantly activated in osteosarcoma. PPI network analysis revealed that hub gene CD163 molecule. We found that the expression of CD163 was negatively associated with the OS of osteosarcoma patients. These results suggest that macrophages are a risk factor in patients with osteosarcoma.

CONCLUSIONS

This study has systematically validated results of the studies carried out previously and filled up the gap in the field of OS on large-scaled meta-analysis. In addition, for the hub gene (CD163) and the macrophage cell capable of being used as a novel biomarker in promoting early diagnosis and development of therapeutic approaches.

Research trends in pharmacological modulation of tumor-associated macrophages

As one of the most abundant immune cell populations in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play important roles in multiple solid malignancies, including breast cancer, prostate cancer, liver cancer, lung cancer, ovarian cancer, gastric cancer, pancreatic cancer, and colorectal cancer. TAMs could contribute to carcinogenesis, neoangiogenesis, immune-suppressive TME remodeling, cancer chemoresistance, recurrence, and metastasis. Therefore, reprogramming of the immune-suppressive TAMs by pharmacological approaches has attracted considerable research attention in recent years. In this review, the promising pharmaceutical targets, as well as the existing modulatory strategies of TAMs were summarized. The chemokine-chemokine receptor signaling, tyrosine kinase receptor signaling, metabolic signaling, and exosomal signaling have been highlighted in determining the biological functions of TAMs. Besides, both preclinical research and clinical trials have suggested the chemokine-chemokine receptor blockers, tyrosine kinase inhibitors, bisphosphonates, as well as the exosomal or nanoparticle-based targeting delivery systems as the promising pharmacological approaches for TAMs deletion or reprogramming. Lastly, the combined therapies of TAMs-targeting strategies with traditional treatments or immunotherapies as well as the exosome-like nanovesicles for cancer therapy are prospected.

Targeting metastatic cancer

Despite recent therapeutic advances in cancer treatment, metastasis remains the principal cause of cancer death. Recent work has uncovered the unique biology of metastasis-initiating cells that results in tumor growth in distant organs, evasion of immune surveillance and co-option of metastatic microenvironments. Here we review recent progress that is enabling therapeutic advances in treating both micro- and macrometastases. Such insights were gained from cancer sequencing, mechanistic studies and clinical trials, including of immunotherapy. These studies reveal both the origins and nature of metastases and identify new opportunities for developing more effective strategies to target metastatic relapse and improve patient outcomes.

Insights from transgenic mouse models of PyMT-induced breast cancer: recapitulating human breast cancer progression in vivo

Breast cancer is associated with the second highest cancer-associated deaths worldwide. Therefore, understanding the key events that determine breast cancer progression, modulation of the tumor-microenvironment and metastasis, which is the main cause of cancer-associated death, are of great importance. The mammary specific polyomavirus middle T antigen overexpression mouse model (MMTV-PyMT), first published in 1992, is the most commonly used genetically engineered mouse model (GEMM) for cancer research. Mammary lesions arising in MMTV-PyMT mice follow similar molecular and histological progression as human breast tumors, making it an invaluable tool for cancer researchers and instrumental in understanding tumor biology. In this review, we will highlight key studies that demonstrate the utility of PyMT derived GEMMs in understanding the molecular basis of breast cancer progression, metastasis and highlight its use as a pre-clinical tool for therapeutic discovery.

Targeting tumor-associated macrophages: A potential treatment for solid tumors

Tumor-associated macrophages (TAMs) in solid tumors exert protumor activities by releasing cytokines or growth factors into the tumor microenvironment. Increasing studies have also shown that TAMs play a key role in tumor progression, such as tumor angiogenesis, immunosuppression, cell proliferation, migration, invasion, and metastasis. A large body of evidence shows that the abundance of TAMs in solid tumors is correlated with poor disease prognosis and resistance to therapies. Therefore, targeting TAMs in solid tumors is considered to be a promising immunotherapeutic strategy. At present, the therapeutic strategies of targeting macrophages mainly include limiting monocyte recruitment, depletion strategies, promoting macrophage phagocytic activity, and induction of macrophage reprogramming. Additionally, targeting TAMs in combination with conventional therapies has been demonstrated to be a promising therapeutic strategy in solid tumors. In the present review, we summarized various TAMs-targeting therapeutic strategies for treating solid tumors. This review also discusses the challenges for targeting TAMs as tumor treatments, the obstacles in clinical trials, and the perspective for the future development of TAMs-targeting therapies for various cancers.

Pathological significance of abnormal recepteur d’origine nantais and programmed death ligand 1 expression in colorectal cancer

BACKGROUND

Programmed death ligand 1 (PD-L1) immunotherapy remains poorly efficacious in colorectal cancer (CRC). The recepteur d’origine nantais (RON) receptor tyrosine kinase plays an important role in regulating tumor immunity.

AIM

To identify the patterns of RON and PD-L1 expression and explore their clinical significance in CRC.

METHODS

Gene expression data from the Gene Expression Omnibus database (GEO; n = 290) and patients at the First Affiliated Hospital, Zhejiang University School of Medicine (FAHZUSM; n = 381) were analyzed to determine the prognostic value of RON and PD-L1 expression within the tumor microenvironment of CRC. HT29 cell line was treated with BMS-777607 to explore the relationship between RON activity and PD-L1 expression. Signaling pathways and protein expression perturbed by RON inhibition were evaluated by cellular immunofluorescence and Western blot.

RESULTS

In the GEO patient cohort, cut-off values for RON and PD-L1 expression were determined to be 7.70 and 4.3, respectively. Stratification of patients based on these cutoffs demonstrated that high expression of RON and PD-L1 was associated with a poor prognosis. In the FAHZUSM cohort, rates of high expression of RON in tumor cells, high PD-L1 expression in tumor cells and tumor infiltrating monocytes, and both high RON and high PD-L1 expression in the tumor microenvironment were 121 (32%), 43 (11%), 91 (24%), and 51 (13.4%), respectively. High expression of RON was significantly correlated with high expression of PD-L1 in the tumor cell compartment (P < 0.001). High expression of RON and that of PD-L1 were independent prognostic factors for poorer overall survival. Concurrent high expression of both RON and PD-L1 in the tumor microenvironment was significantly associated with a poor prognosis. In vitro, BMS-777607 inhibited the phosphorylation of RON, inhibited PD-L1 expression, and attenuated activation of the ERK1/2 and AKT signaling pathways in CRC cells.

CONCLUSION

RON, PD-L1, and their crosstalk are significant in predicting the prognostic value of CRC. Moreover, phosphorylation of RON upregulates PD-L1 expression, which provides a novel approach to immunotherapy in CRC.

MSP-RON Pathway: Potential Regulator of Inflammation and Innate Immunity

Macrophage-stimulating protein (MSP), a soluble protein mainly synthesized by the liver, is the only known ligand for recepteur d'origine nantais (RON), which is a member of the MET proto-oncogene family. Recent studies show that the MSP-RON signaling pathway not only was important in tumor behavior but also participates in the occurrence or development of many immune system diseases. Activation of RON in macrophages results in the inhibition of nitric oxide synthesis as well as lipopolysaccharide (LPS)-induced inflammatory response. MSP-RON is also associated with chronic inflammatory responses, especially chronic liver inflammation, and might serve as a novel regulator of inflammation, which may affect the metabolism in the body. Another study provided evidence of the relationship between MSP-RON and autoimmune diseases, suggesting a potential role for MSP-RON in the development of drugs for autoimmune diseases. Moreover, MSP-RON plays an important role in maintaining the stability of the tissue microenvironment and contributes to immune escape in the tumor immune microenvironment. Here, we summarize the role of MSP-RON in immunity, based on recent findings, and lay the foundation for further research.

The MSP-RON axis stimulates cancer cell growth in models of triple negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor prognosis and high rates of relapse. The lack of actionable targets for TNBC has contributed to the high mortality rates of this disease, and new candidate molecules for potential manipulation are urgently required. Here, we show that macrophage-stimulating protein (MSP) and its tyrosine kinase receptor, Recepteur d'origine nantais (RON), are potent drivers of cancer cell growth and tumor progression in a mouse model of TNBC driven by the loss of Trp53 and Brca1. After comparison of two genetically engineered mouse models of TNBC, we found that mammary tumors from K14-Cre;Brca1F/F ;Trp53F/F (KB1P) mice exhibit high endogenous levels of MSP and RON expression. We show that MSP stimulates serine/threonine kinase 1 and extracellular regulated MAPK activation as well as cancer cell growth in cell lines derived from the two mouse models, while genetic and pharmacological inhibition of RON prevents these effects. Similarly, KB1P tumor progression in mice was robustly attenuated by treatment with a RON inhibitor with accompanied reduction in the proliferation marker, Ki-67. Analysis of human gene expression data confirmed that the genes encoding MSP and RON are robustly expressed in human TNBC as well as other subsets of breast cancer. Our findings uncover a mouse model where MSP expression and RON expression are naturally increased, and they provide evidence that this receptor and its ligand are viable candidate molecules for targeted treatment of breast cancer.

MST1R (RON) expression is a novel prognostic biomarker for metastatic progression in breast cancer patients

PURPOSE

This study evaluates the prognostic significance of MST1R (RON) expression in breast cancer with respect to disease progression, long-term survival, subtype, and association with conventional prognostic factors.

METHODS

The approach includes interrogation of survival and tumor staging with paired MST1R RNA expression from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets. Protein expression evaluation was performed using immunohistochemistry (IHC) staining of MST1R on breast cancer tissue samples from the Cancer Diagnosis Program Breast Cancer Progression tissue microarray and locally obtained breast tumor tissue samples analyzed with paired survival, metastasis, and subtype.

RESULTS

Data from TCGA (n = 774) show poorer relapse-free survival (RFS) in patients with high MST1R expression (P = 0.32) and no difference in MST1R expression based on tumor stage (P = 0.77) or nodal status (P = 0.94). Patients in the GEO-derived Kaplan-Meier Plotter microarray dataset demonstrate the association of MST1R and poorer overall survival (n = 1402, P = 0.018) and RFS in patients receiving chemotherapy (n = 798, P = 0.041). Patients with high MST1R expression display worse overall survival (P = 0.01) and receiver operator characteristic (ROC) analysis demonstrate the predictive capacity of increased MST1R with early death (P = 0.0017) in IHC-stained samples. Paired IHC-stained breast tumor samples from the primary versus metastatic site show MST1R expression is associated with metastatic progression (P = 0.032), and ROC analysis supports the predictive capacity of MST1R in metastatic progression (P = 0.031). No associations of MST1R with estrogen receptor (ER), progesterone receptor (PR), both ER and PR, HER2 positivity, or triple-negativity were found (P = 0.386, P = 0.766, P = 0.746, P = 0.457, P = 0.947, respectively).

CONCLUSIONS

MST1R expression has prognostic value in breast cancer with respect to survival and metastatic progression. MST1R expression is not associated with tumor stage, nodal status, or subtype.

The Receptor Tyrosine Kinase RON and Its Isoforms as Therapeutic Targets in Ewing Sarcoma

The receptor tyrosine kinase (RTK) RON is linked to an aggressive metastatic phenotype of carcinomas. While gaining interest as a therapeutic target, RON remains unstudied in sarcomas. In Ewing sarcoma, we identified RON among RTKs conferring resistance to insulin-like growth factor-1 receptor (IGF1R) targeting. Therefore, we explored RON in pediatric sarcoma cell lines and an embryonic Tg(kdrl:mCherry) zebrafish model, using an shRNA-based approach. To examine RON–IGF1R crosstalk, we employed the clinical-grade monoclonal antibody IMC-RON8, alone and together with the IGF1R-antibody IMC-A12. RON silencing demonstrated functions in vitro and in vivo, particularly within micrometastatic cellular capacities. Signaling studies revealed a unidirectional IGF1-mediated cross-activation of RON. Yet, IMC-A12 failed to sensitize cells to IMC-RON8, suggesting additional mechanisms of RON activation. Here, RT-PCR revealed that childhood sarcomas express short-form RON, an isoform resistant to antibody-mediated targeting. Interestingly, in contrast to carcinomas, treatment with DNA methyltransferase inhibitor did not diminish but increased short-form RON expression. Thus, this first report supports a role for RON in the metastatic progression of Ewing sarcoma. While principal molecular functions appear transferrable between carcinomas, Ewing sarcoma and possibly more common sarcoma subtypes, RON highlights that specific regulations of cellular networks and isoforms require better understanding to successfully transfer targeting strategies.

Metastasis Organotropism: Redefining the Congenial Soil

Metastasis is the most devastating stage of cancer progression and causes the majority of cancer-related deaths. Clinical observations suggest that most cancers metastasize to specific organs, a process known as "organotropism." Elucidating the underlying mechanisms may help identify targets and treatment strategies to benefit patients. This review summarizes recent findings on tumor-intrinsic properties and their interaction with unique features of host organs, which together determine organ-specific metastatic behaviors. Emerging insights related to the roles of metabolic changes, the immune landscapes of target organs, and variation in epithelial-mesenchymal transitions open avenues for future studies of metastasis organotropism.

Translation of cancer immunotherapy from the bench to the bedside

The tremendous success of immune checkpoint blockades has revolutionized cancer management. Our increased understanding of the cell types that compose the tumor microenvironment (TME), including those of the innate and adaptive immune system, has helped to shape additional immune modulatory strategies in cancer care. Pre-clinical and clinical investigations targeting novel checkpoint interactions and key pathways that regulate cancer immunity continue to increase rapidly. Various combinatorial drug regimens are being tested in attempt to achieve durable response and survival rates of patients with cancer. This review provides an overview of specific components of the TME, an introduction to novel immune checkpoints, followed by a survey of present day and future combination immune modulatory therapies. The idea that the immune system can recognize and destroy tumor cells was first described in the cancer immunosurveillance hypothesis of Burnet and Thomas. However, early experimental evidence failed to support the concept. It was not until the late 1990s when seminal papers clearly showed the existence of cancer immunosurveillance, leading to the cancer immunoediting hypothesis. In this century, progress in the understanding of negative regulators of the immune response led to the discovery that inhibition of these regulators in patients with cancer could lead to dramatic and durable remissions. Drs. Tasuku Honjo and James P. Allison were awarded the Nobel Prize in 2018 for their pioneering work in this field. We now see rapid advances in cancer immunology and emerging effective therapies revolutionizing cancer care across tumor types in the clinic, while pre-clinical research is moving from a focus on the malignant cells themselves to dissect the highly heterogenic and complex multi-cellular tumor microenvironment (TME).

Tailoring Nanomaterials for Targeting Tumor-Associated Macrophages

Advances in the field of nanotechnology together with an increase understanding of tumor immunology have paved the way for the development of more personalized cancer immuno-nanomedicines. Nanovehicles, due to their specific physicochemical properties, are emerging as key translational moieties in tackling tumor-promoting, M2-like tumor-associated macrophages (TAMs). Cancer immuno-nanomedicines target TAMs primarily by blocking M2-like TAM survival or affecting their signaling cascades, restricting macrophage recruitment to tumors and re-educating tumor-promoting M2-like TAMs to the tumoricidal, M1-like phenotype. Here, the TAM effector mechanisms and strategies for targeting TAMs are summarized, followed by a focus on the mechanistic considerations in the development of novel immuno-nanomedicines. Furthermore, imaging TAMs with nanoparticles so as to forecast a patient's clinical outcome, describing treatment options, and observing therapy responses is also discussed. At present, strategies that target TAMs are being investigated not only at the basic research level but also in early clinical trials. The significance of TAM-targeting biomaterials is highlighted, with the goal of facilitating future clinical translation.

Receptor tyrosine kinase recepteur d'origine nantais as predictive marker for aggressive prostate cancer in African Americans

Published evidence shows a correlation between several molecular markers and prostate cancer (PCa) progression including in African Americans (AAs) who are disproportionately affected. Our early detection efforts led to the identification of elevated levels of antiapoptotic protein, c-FLIP and its upstream regulatory factors such as androgen receptor (AR), recepteur d'origine nantais (RON), a receptor tyrosine kinase in human prostate tumors. The primary objective of this study was to explore whether these markers play a role in racial disparities using immunohistochemistry in prostatectomy samples from a cohort of AA, Hispanic Whites (HWs), and non-Hispanic Whites (NHWs). Bivariable and multivariable logistic regression analyses were used to identify a statistical association between molecular markers, possible correlation with risk factors including race, obesity, prostate-specific antigen (PSA) and disease aggressiveness. Further, changes in the levels and expression of these molecular markers were also evaluated using human PCa cell lines. We found significantly elevated levels of RON ( P = 0.0082), AR ( P = 0.0001), c-FLIP ( P = 0.0071) in AAs compared with HWs or NHWs. Furthermore, a higher proportion of HW and NHWs had a high Gleason score (>6) but not PSA as compared to AAs ( P = 0.032). In summary, our findings suggest that PSA was important in predicting aggressive disease for the cohort overall; however, high levels of RON may play a role in predisposing AA men to develop aggressive disease. Future research is needed using large datasets to confirm these findings and to explore whether all or any of these markers could aid in race-specific stratification of patients for treatment.

Targeting the immunity protein kinases for immuno-oncology

With the rise of immuno-oncology, small-molecule modulators targeting immune system and inflammatory processes are becoming a research hotspot. This work mainly focuses on key kinases acting as central nodes in immune signaling pathways. Although over thirty small-molecule kinase inhibitors have been approved by FDA for the treatment of various cancers, only a few are associated with immuno-oncology. With the going deep of the research work, more and more immunity protein kinase inhibitors are approved for clinical trials to treat solid tumors and hematologic malignancies by FDA, which remain good prospects. Meanwhile, in-depth understanding of biological function of immunity protein kinases in immune system is pushing the field forward. This article focuses on the development of safe and effective small-molecule immunity protein kinase inhibitors and further work needs to keep the promises of these inhibitors for patients' welfare.

Alterations of Signaling Pathways Related to the Immune System in Breast Cancer: New Perspectives in Patient Management

In recent years, immune manipulation for cancer treatment, including breast cancer, has been increasingly gaining consent, and many attempts have been made, mainly by either strengthening the immune response (IR) or by inhibiting immune evasion. Therefore, elucidating the related mechanisms is of importance due to the potential to improve the management of cancer patients by immunotherapy. This review article summarized some recent experimental studies, which have discovered novel alterations of signaling pathways related to the immune system in breast cancer. These altered signaling pathways have been grouped according to the general biological mechanism involved: tumor-initiating cells (TICs), cancer stem cells (CSCs), immune evasion, tumor growth and progression, prediction of clinical outcome and prediction of response, or resistance to chemotherapy. These altered pathways related to the immune system open clinical opportunities for the prognosis or treatment of patients. Many of these pathways are related to the origin of breast cancer and immune evasion. We recommended development of new drugs which act on these molecular pathways, and the designing of clinical trials to be carried out mainly in breast cancer patients who required adjuvant treatment.

Inhibition of RON kinase potentiates anti-CTLA-4 immunotherapy to shrink breast tumors and prevent metastatic outgrowth

The advent of immune checkpoint blockade as a new strategy for immunotherapy has changed the outlook for many aggressive cancers. Although complete tumor eradication is attainable in some cases, durable clinical responses are observed only in a small fraction of patients, underlining urgent need for improvement. We previously showed that RON, a receptor tyrosine kinase expressed in macrophages, suppresses antitumor immune responses, and facilitates progression and metastasis of breast cancer. Here, we investigated the molecular changes that occur downstream of RON activation in macrophages, and whether inhibition of RON can cooperate with checkpoint immunotherapy to eradicate tumors. Activation of RON by its ligand, MSP, altered the gene expression profile of macrophages drastically and upregulated surface levels of CD80 and PD-L1, ligands for T-cell checkpoint receptors CTLA-4 and PD-1. Genetic deletion or pharmacological inhibition of RON in combination with anti-CTLA-4, but not with anti-PD-1, resulted in improved clinical responses against orthotopically transplanted tumors compared to single-agent treatment groups, resulting in complete tumor eradication in 46% of the animals. Positive responses to therapy were associated with higher levels of T-cell activation markers and tumor-infiltrating lymphocytes. Importantly, co-inhibition of RON and anti-CTLA-4 was also effective in clearing metastatic breast cancer cells in lungs, resulting in clinical responses in nearly 60% of the mice. These findings suggest that RON inhibition can be a novel approach to potentiate responses to checkpoint immunotherapy in breast cancer.

Unresolved endoplasmic reticulum stress engenders immune-resistant, latent pancreatic cancer metastases

The majority of patients with pancreatic ductal adenocarcinoma (PDA) develop metastatic disease after resection of their primary tumor. We found that livers from patients and mice with PDA harbor single disseminated cancer cells (DCCs) lacking expression of cytokeratin 19 (CK19) and major histocompatibility complex class I (MHCI). We created a mouse model to determine how these DCCs develop. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs that were CK19^- and MHCI^- The DCCs exhibited an endoplasmic reticulum (ER) stress response but paradoxically lacked both inositol-requiring enzyme 1α activation and expression of the spliced form of transcription factor XBP1 (XBP1s). Inducible expression of XBP1s in DCCs, in combination with T cell depletion, stimulated the outgrowth of macrometastatic lesions that expressed CK19 and MHCI. Thus, unresolved ER stress enables DCCs to escape immunity and establish latent metastases.

NetH2pan: A Computational Tool to Guide MHC Peptide Prediction on Murine Tumors

With the advancement of personalized cancer immunotherapies, new tools are needed to identify tumor antigens and evaluate T-cell responses in model systems, specifically those that exhibit clinically relevant tumor progression. Key transgenic mouse models of breast cancer are generated and maintained on the FVB genetic background, and one such model is the mouse mammary tumor virus-polyomavirus middle T antigen (MMTV-PyMT) mouse-an immunocompetent transgenic mouse that exhibits spontaneous mammary tumor development and metastasis with high penetrance. Backcrossing the MMTV-PyMT mouse from the FVB strain onto a C57BL/6 genetic background, in order to leverage well-developed C57BL/6 immunologic tools, results in delayed tumor development and variable metastatic phenotypes. Therefore, we initiated characterization of the FVB MHC class I H-2^q haplotype to establish useful immunologic tools for evaluating antigen specificity in the murine FVB strain. Our study provides the first detailed molecular and immunoproteomic characterization of the FVB H-2^q MHC class I alleles, including >8,500 unique peptide ligands, a multiallele murine MHC peptide prediction tool, and in vivo validation of these data using MMTV-PyMT primary tumors. This work allows researchers to rapidly predict H-2 peptide ligands for immune testing, including, but not limited to, the MMTV-PyMT model for metastatic breast cancer. Cancer Immunol Res; 6(6); 636-44. ©2018 AACR.

RON kinase: A target for treatment of cancer-induced bone destruction and osteoporosis

Bone destruction occurs in aging and numerous diseases, including osteoporosis and cancer. Many cancer patients have bone osteolysis that is refractory to state-of-the-art treatments, which block osteoclast activity with bisphosphonates or by inhibiting the receptor activator of nuclear factor κB ligand (RANKL) pathway. We previously showed that macrophage-stimulating protein (MSP) signaling, which is elevated in about 40% of breast cancers, promotes osteolytic bone metastasis by activation of the MSP signaling pathway in tumor cells or in the bone microenvironment. We show that MSP signals through its receptor, RON tyrosine kinase, expressed on host cells, to activate osteoclasts directly by a previously undescribed pathway that is complementary to RANKL signaling and converges on proto-oncogene, non-receptor tyrosine kinase SRC (SRC). Genetic or pharmacologic inhibition of RON kinase blocked cancer-mediated bone destruction and osteoporosis in several mouse models. Furthermore, the RON kinase inhibitor BMS-777607/ASLAN002 altered markers of bone turnover in a first-in-human clinical cancer study, indicating the inhibitor's potential for normalizing bone loss in patients. These findings uncover a new therapeutic target for pathogenic bone loss and provide a rationale for treatment of bone destruction in various diseases with RON inhibitors.

HGFL-mediated RON signaling supports breast cancer stem cell phenotypes via activation of non-canonical β-catenin signaling

Breast cancer stem cells (BCSCs), which drive tumor progression, recurrence, and metastasis, are considered a major challenge for breast cancer treatments, thus the discovery of novel pathways regulating BCSC maintenance remains essential to develop new strategies to effectively target this population and combat disease mortality. The HGFL-RON signaling is overexpressed in human breast cancers and is associated with increased breast cancer progression, metastasis, and poor prognosis. Here, we report that overexpression of RON/MST1R and HGFL/MST1 in cell lines and primary tumors increases BCSC self-renewal, numbers, and tumorigenic potential after syngeneic transplantation. Transcriptome analyses also reveal that the HGFL-RON signaling pathway regulates additional BCSC functions and supports an immunosuppressive microenvironment to stimulate tumor formation and progression. Moreover, we show that genetic and chemical downregulation of HGFL-RON signaling disrupts BCSC phenotypes and tumor growth by suppressing the RON-mediated phosphorylation/activation of β-CATENIN/CTNNB1 and its effector NF-κB/RELA. These studies indicate that HGFL-RON signaling regulates BCSC phenotypes and the tumor microenvironment to drive tumorigenesis and present HGFL/RON as novel therapeutic targets to effectively eradicate BCSCs in patients.

Global survey of the immunomodulatory potential of common drugs

Small-molecule drugs may complement antibody-based therapies in an immune-oncology setting, yet systematic methods for the identification and characterization of the immunomodulatory properties of these entities are lacking. We surveyed the immumomodulatory potential of 1,402 small chemical molecules, as defined by their ability to alter the cell-cell interactions among peripheral mononuclear leukocytes ex vivo, using automated microscopy and population-wide single-cell image analysis. Unexpectedly, ∼10% of the agents tested affected these cell-cell interactions differentially. The results accurately recapitulated known immunomodulatory drug classes and revealed several clinically approved drugs that unexpectedly harbor the ability to modulate the immune system, which could potentially contribute to their physiological mechanism of action. For instance, the kinase inhibitor crizotinib promoted T cell interactions with monocytes, as well as with cancer cells, through inhibition of the receptor tyrosine kinase MSTR1 and subsequent upregulation of the expression of major histocompatibility complex molecules. The approach offers an attractive platform for the personalized identification and characterization of immunomodulatory therapeutics.

Therapeutic IgE Antibodies: Harnessing a Macrophage-Mediated Immune Surveillance Mechanism against Cancer

IgG monoclonal antibodies have made significant contributions to cancer therapy, but suffer from several limitations that restrict their effectiveness in unleashing host immune system components against tumors. The development of monoclonal antibodies of an alternative class, namely IgE, may offer enhanced immune surveillance and superior effector cell potency against cancer cells. In our recent article, we elaborate our proof-of-concept studies of a mouse/human chimeric IgE antibody (MOv18 IgE), which is specific for the cancer-associated antigen folate receptor alpha. We demonstrate superior antitumor efficacy for IgE compared with an otherwise identical IgG in a syngeneic immunocompetent animal, and we identify TNFα/MCP-1 signaling as an IgE-mediated mechanism of monocyte and macrophage activation and recruitment to tumors. These findings draw parallels with powerful macrophage-activating functions employed by IgE against parasites, rather than allergic IgE mechanisms. The potential clinical application of IgE-derived drugs in clinical oncology is clear if the antitumor activity of MOv18 IgE in these preclinical experiments can be replicated in patients. In particular, different IgE antibodies with specificity for many other antigens already validated as targets for IgG suggest a wide potential for development of a novel class of antibody therapy. Cancer Res; 77(11); 2779-83. ©2017 AACR.

Progress in tumor-associated macrophage (TAM)-targeted therapeutics

As an essential innate immune population for maintaining body homeostasis and warding off foreign pathogens, macrophages display high plasticity and perform diverse supportive functions specialized to different tissue compartments. Consequently, aberrance in macrophage functions contributes substantially to progression of several diseases including cancer, fibrosis, and diabetes. In the context of cancer, tumor-associated macrophages (TAMs) in tumor microenvironment (TME) typically promote cancer cell proliferation, immunosuppression, and angiogenesis in support of tumor growth and metastasis. Oftentimes, the abundance of TAMs in tumor is correlated with poor disease prognosis. Hence, significant attention has been drawn towards development of cancer immunotherapies targeting these TAMs; either depleting them from tumor, blocking their pro-tumoral functions, or restoring their immunostimulatory/tumoricidal properties. This review aims to introduce readers to various aspects in development and evaluation of TAM-targeted therapeutics in pre-clinical and clinical stages.

The Shc1 adaptor simultaneously balances Stat1 and Stat3 activity to promote breast cancer immune suppression

Tyrosine kinase signalling within cancer cells is central to the establishment of an immunosuppressive microenvironment. Although tyrosine kinase inhibitors act, in part, to augment adaptive immunity, the increased heterogeneity and functional redundancy of the tyrosine kinome is a hurdle to achieving durable responses to immunotherapies. We previously identified the Shc1 (ShcA) scaffold, a central regulator of tyrosine kinase signalling, as essential for promoting breast cancer immune suppression. Herein we show that the ShcA pathway simultaneously activates STAT3 immunosuppressive signals and impairs STAT1-driven immune surveillance in breast cancer cells. Impaired Y239/Y240-ShcA phosphorylation selectively reduces STAT3 activation in breast tumours, profoundly sensitizing them to immune checkpoint inhibitors and tumour vaccines. Finally, the ability of diminished tyrosine kinase signalling to initiate STAT1-driven immune surveillance can be overcome by compensatory STAT3 hyperactivation in breast tumours. Our data indicate that inhibition of pY239/240-ShcA-dependent STAT3 signalling may represent an attractive therapeutic strategy to sensitize breast tumours to multiple immunotherapies.

Tyrosine kinase signalling in cancer cells promotes immune evasion. Here, the authors show that tyrosine kinases engage scaffold protein Shc1 to promote immunosuppression in breast cancer by simultaneously activating STAT3 immunosuppressive signals and impairing STAT1-driven anti-tumour immune responses.

Meeting report: Metastasis Research Society-Chinese Tumor Metastasis Society joint conference on metastasis

During September 16th-20th 2016, metastasis experts from around the world convened for the 16th Biennial Congress of the Metastasis Research Society and 12th National Congress of the Chinese Tumor Metastasis Society in Chengdu, China to share most current data covering basic, translational, and clinical metastasis research. Presentations of the more than 40 invited speakers of the main congress and presentations from the associated Young Investigator Satellite Meeting are summarized in this report by session topic. The congress program also included three concurrent short talk sessions, an advocacy forum with Chinese and American metastatic patient advocates, a 'Meet the Professors Roundtable' session for young investigators, and a 'Meet the Editors' session with editors from Cancer Cell and Nature Cell Biology. The goal of integrating expertise and exchanging the latest findings, ideas, and practices in cancer metastasis research was achieved magnificently, thanks to the excellent contributions of many leaders in the field.

RON Signaling Is a Key Mediator of Tumor Progression in Many Human Cancers

With an increasing body of literature covering RON receptor tyrosine kinase function in different types of human cancers, it is becoming clear that RON has prominent roles in both cancer cells and in the tumor-associated microenvironment. RON not only activates several oncogenic signaling pathways in cancer cells, leading to more aggressive behavior, but also promotes an immunosuppressive, alternatively activated phenotype in macrophages and limits the antitumor immune response. These two unique functions of this oncogene, the strong correlation between RON expression and poor outcomes in cancer, and the high tolerability of a new RON inhibitor make it an exciting therapeutic target, the blocking of which offers an advantage toward improving the survival of cancer patients. Here, we discuss recent findings on the role of RON signaling in cancer progression and its potential in cancer therapy.

RON kinase isoforms demonstrate variable cell motility in normal cells

INTRODUCTION

Aberrant RON (Recepteur d'Origine Nantais) tyrosine kinase activation causes the epithelial cell to evade normal growth pathways, resulting in unregulated cell proliferation, increased cell motility and decreased apoptosis. Wildtype (wt) RON has been shown to play a role in metastasis of epithelial malignancies. It presents an important potential therapeutic target for colorectal, breast, gastric and pancreatic cancer. Little is known about functional differences amongst RON isoforms RON155, RON160 and RON165. The purpose of this study was to determine the effect of various RON kinase isoforms on cell motility.

METHODS

Cell lines with stable expression of wtRON were generated by inserting the coding region of RON in pTagRFP (tagged red fluorescence protein plasmid). The expression constructs of RON variants (RON155, RON160 and RON165) were generated by creating a mutagenesis-based wtRON-pTag RFP plasmid and stably transfected into HEK 293 cells. The wound closure scratch assay was used to investigate the effect on cell migratory capacity of wild type RON and its variants.

RESULTS

RON transfected cells demonstrated increased cell motility compared to HEK293 control cells. RON165 cell motility was significantly increased compared to RON160 (mean percentage of wound covered 37.37% vs. 32.40%; p = 0.03).

CONCLUSIONS

RON tyrosine kinase isoforms have variable cell motility. This may reflect a difference in the behavior of malignant epithelial cells and their capacity for metastasis.

The Basis of Oncoimmunology

Cancer heterogeneity, a hallmark enabling clonal survival and therapy resistance, is shaped by active immune responses. Antigen-specific T cells can control cancer, as revealed clinically by immunotherapeutics such as adoptive T-cell transfer and checkpoint blockade. The host immune system is thus a powerful tool that, if better harnessed, could significantly enhance the efficacy of cytotoxic therapy and improve outcomes for cancer sufferers. To realize this vision, however, a number of research frontiers must be tackled. These include developing strategies for neutralizing tumor-promoting inflammation, broadening T-cell repertoires (via vaccination), and elucidating the mechanisms by which immune cells organize tumor microenvironments to regulate T-cell activity. Such efforts will pave the way for identifying new targets for combination therapies that overcome resistance to current treatments and promote long-term cancer control.

A novel protein isoform of the RON tyrosine kinase receptor transforms human pancreatic duct epithelial cells

The MST1R gene is overexpressed in pancreatic cancer producing elevated levels of the RON tyrosine kinase receptor protein. While mutations in MST1R are rare, alternative splice variants have been previously reported in epithelial cancers. We report the discovery of a novel RON isoform discovered in human pancreatic cancer. Partial splicing of exons 5 and 6 (P5P6) produces a RON isoform that lacks the first extracellular immunoglobulin-plexin-transcription domain. The splice variant is detected in 73% of xenografts derived from pancreatic adenocarcinoma patients and 71% of pancreatic cancer cell lines. Peptides specific to RON P5P6 detected in human pancreatic cancer specimens by mass spectrometry confirm translation of the protein isoform. The P5P6 isoform is found to be constitutively phosphorylated, present in the cytoplasm, and it traffics to the plasma membrane. Expression of P5P6 in immortalized human pancreatic duct epithelial (HPDE) cells activates downstream AKT, and in human pancreatic epithelial nestin-expressing cells, activates both the AKT and MAPK pathways. Inhibiting RON P5P6 in HPDE cells using a small molecule inhibitor BMS-777607 blocked constitutive activation and decreased AKT signaling. P5P6 transforms NIH3T3 cells and induces tumorigenicity in HPDE cells. Resultant HPDE-P5P6 tumors develop a dense stromal compartment similar to that seen in pancreatic cancer. In summary, we have identified a novel and constitutively active isoform of the RON tyrosine kinase receptor that has transforming activity and is expressed in human pancreatic cancer. These findings provide additional insight into the biology of the RON receptor in pancreatic cancer and are clinically relevant to the study of RON as a potential therapeutic target.

HGFL supports mammary tumorigenesis by enhancing tumor cell intrinsic survival and influencing macrophage and T-cell responses

The Ron receptor is overexpressed in human breast cancers and is associated with heightened metastasis and poor survival. Ron overexpression in the mammary epithelium of mice is sufficient to induce aggressive mammary tumors with a high degree of metastasis. Despite the well-documented role of Ron in breast cancer, few studies have examined the necessity of the endogenous Ron ligand, hepatocyte growth factor-like protein (HGFL) in mammary tumorigenesis. Herein, mammary tumor growth and metastasis were examined in mice overexpressing Ron in the mammary epithelium with or without HGFL. HGFL ablation decreased oncogenic Ron activation and delayed mammary tumor initiation. HGFL was important for tumor cell proliferation and survival. HGFL loss resulted in increased numbers of macrophages and T-cells within the tumor. T-cell proliferation and cytotoxicity dramatically increased in HGFL deficient mice. Biochemical analysis of HGFL proficient tumors showed increased local HGFL production, with HGFL loss decreasing β-catenin expression and NF-κB activation. Re-expression of HGFL in HGFL deficient tumor cells stimulated cell migration and invasion with coordinate activation of NF-κB and reduced apoptosis. Together, these results demonstrate critical in vivo functions for HGFL in promoting breast tumorigenesis and suggest that targeting HGFL may inhibit tumor growth and reactivate anti-tumor immune responses.

The Tyrosine Kinome Dictates Breast Cancer Heterogeneity and Therapeutic Responsiveness

Phospho-tyrosine signaling networks control numerous biological processes including cellular differentiation, cell growth and survival, motility, and invasion. Aberrant regulation of the tyrosine kinome is a hallmark of malignancy and influences all stages of breast cancer progression, from initiation to the development of metastatic disease. The success of specific tyrosine kinase inhibitors strongly validates the clinical relevance of tyrosine phosphorylation networks in breast cancer pathology. However, a significant degree of redundancy exists within the tyrosine kinome. Numerous receptor and cytoplasmic tyrosine kinases converge on a core set of signaling regulators, including adaptor proteins and tyrosine phosphatases, to amplify pro-tumorigenic signal transduction pathways. Mutational activation, amplification, or overexpression of one or more components of the tyrosine kinome represents key contributing events responsible for the tumor heterogeneity that is observed in breast cancers. It is this molecular heterogeneity that has become the most significant barrier to durable clinical responses due to the development of therapeutic resistance. This review focuses on recent literature that supports a prominent role for specific components of the tyrosine kinome in the emergence of unique breast cancer subtypes and in shaping breast cancer plasticity, sensitivity to targeted therapies, and the eventual emergence of acquired resistance. J. Cell. Biochem. 117: 1971-1990, 2016. © 2016 Wiley Periodicals, Inc.

New insights into tumor dormancy: Targeting DNA repair pathways

Over the past few decades, major strides have advanced the techniques for early detection and treatment of cancer. However, metastatic tumor growth still accounts for the majority of cancer-related deaths worldwide. In fact, breast cancers are notorious for relapsing years or decades after the initial clinical treatment, and this relapse can vary according to the type of breast cancer. In estrogen receptor-positive breast cancers, late tumor relapses frequently occur whereas relapses in estrogen receptor-negative cancers or triple negative tumors arise early resulting in a higher mortality risk. One of the main causes of metastasis is tumor dormancy in which cancer cells remain concealed, asymptomatic, and untraceable over a prolonged period of time. Under certain conditions, dormant cells can re-enter into the cell cycle and resume proliferation leading to recurrence. However, the molecular and cellular regulators underlying this transition remain poorly understood. To date, three mechanisms have been identified to trigger tumor dormancy including cellular, angiogenic, and immunologic dormancies. In addition, recent studies have suggested that DNA repair mechanisms may contribute to the survival of dormant cancer cells. In this article, we summarize the recent experimental and clinical evidence governing cancer dormancy. In addition, we will discuss the role of DNA repair mechanisms in promoting the survival of dormant cells. This information provides mechanistic insight to explain why recurrence occurs, and strategies that may enhance therapeutic approaches to prevent disease recurrence.