Signal regulatory protein α is associated with tumor-polarized macrophages phenotype switch and plays a pivotal role in tumor progression

Identification of a novel subtype of SPP1 + macrophages expressing SIRPα: implications for tumor immune evasion and treatment response prediction

BACKGROUND

SPP1 + macrophages are among the major phagocytic cells, yet promoting tumor immune evasion and predicting unfavorable prognosis, in various cancer types. Meanwhile, the predictive value of the abundance of SPP1 + macrophages in patients receiving immunotherapy remains debatable, indicating the potential existence of subtypes of SPP1 + macrophages with diverse biological functions.

METHODS

The single cell RNA sequencing data of myeloid cells integrated from several cancers including esophageal squamous cell carcinoma was analyzed for characterizing the function and cellular interactions of SPP1 + macrophages expressing SIRPα. Multiplexed immunohistochemistry was used to quantify the quantity and spatial distribution of SPP1 + macrophages expressing SIRPα. Kaplan-Meier method was used for survival analysis. In vitro and in vivo studies investigating the function of SPP1 + macrophages were performed.

RESULTS

SPP1 + macrophages possessed a high phagocytic signature and could engulf more tumor cells in vitro and in vivo. SIRPα expression could represent the phagocytic activity of SPP1 + macrophages and delineated subsets of SPP1 + macrophages with different functions. SPP1 + SIRPα + macrophages showed close spatial distance to tumor cells and positively correlated with PD1 + CD8 + T cells. A high abundance of SPP1 + SIRPα + macrophages at baseline corresponded to patients' response to PD-1/PD-L1 inhibitors.

CONCLUSION

A novel subtype of SPP1 + macrophages expressing SIRPα was identified and their abundance predicted patients' response to PD-1/PD-L1 inhibitors.

Clinical Significance of SIRPα Expression on Tumor-Associated Macrophages in Patients with Lung Squamous Cell Carcinoma

BACKGROUND

Signal-regulatory protein alpha (SIRPα) is an immune checkpoint molecule expressed on macrophages that functions to inhibit phagocytosis by binding to CD47 expressed on tumor cells. SIRPα has attracted increasing attention as a novel target for cancer immunotherapy; however, the expression and immune function of SIRPα in lung squamous cell carcinoma (LUSC) remain unclear. Therefore, this study aimed to identify the clinical importance of SIRPα expression in LUSC and to explore the factors that elevate SIRPα expression.

PATIENTS AND METHODS

Primary LUSC specimens surgically resected from 172 patients underwent immunohistochemical evaluation of the association of SIRPα expression on tumor-associated macrophages with clinicopathological features and clinical outcomes. Furthermore, we analyzed the association of SIRPα expression with tumor-infiltrating lymphocytes and the expression of programmed cell death ligand 1 (PD-L1). In vitro, monocytes were treated with cytokines, and SIRPα protein expression was assessed by flow cytometry.

RESULTS

There were no differences in SIRPα expression and clinicopathological factors. High SIRPα expression was significantly associated with PD-L1-positive expression, and high CD8, PD-1, and CD163 expression. The high SIRPα expression group showed significantly shorter recurrence-free survival (RFS) and overall survival (OS). On multivariate analysis, high SIRPα expression was an independent poor prognostic factor for RFS and OS. The expression of SIRPα protein in monocytes was upregulated by treatment with IFNγ.

CONCLUSION

Our analysis revealed that high SIRPα expression significantly predicts poor prognosis in patients with surgically resected LUSC.

Identification of a cuproptosis and copper metabolism gene-related lncRNAs prognostic signature associated with clinical and immunological characteristics of hepatocellular carcinoma

Background

The relationship between cuproptosis and HCC is still in the exploratory stage. Long noncoding RNAs (lncRNAs) have recently been linked to the progression of hepatocellular carcinoma (HCC). However, the clinical significance of lncRNAs associated with cuproptosis remains unclear.

Methods

Based on The Cancer Genome Atlas (TCGA) liver hepatocellular carcinoma (LIHC) dataset, we identified characteristic prognostic lncRNAs by univariate, LASSO, and multifactorial regression analysis, and constructed a prognostic signature of cuproptosis-related lncRNAs in HCC. The role of lncRNAs were identified through CCK-8, clone formation in Huh-7 cells with high expression of FDX1. Prognostic potential of the characteristic lncRNAs was evaluated in each of the two cohorts created by randomly dividing the TCGA cohort into a training cohort and a test cohort in a 1:1 ratio. Immune profiles in defined subgroups of cuproptosis-related lncRNA features as well as drug sensitivity were analyzed.

Results

We constructed a multigene signature based on four characteristic prognostic lncRNAs (AL590705.3, LINC02870, KDM4A-AS1, MKLN1-AS). These four lncRNAs participated in the development of cuproptosis. HCC patients were classified into high-risk and low-risk groups based on the median value of the risk score. The receiver operating characteristic curve area under the curve values for 1-, 3-, and 5-year survival were 0.773, 0.728, and 0.647, respectively, for the training cohort, and 0.764, 0.671, and 0.662, respectively, for the test cohort. Univariate and multifactorial regression analyses indicated that this prognostic feature was an independent prognostic factor for HCC. Principal component analysis plots clearly distinguished between low- and high-risk patients in terms of their probability of survival. Furthermore, gene set enrichment analysis showed that a variety of processes associated with tumor proliferation and progression were enriched in the high-risk group compared with the low-risk group. Moreover, there were significant differences in the expression of immune cell subpopulations, immune checkpoint genes, and potential drug screening, which provided distinct therapeutic recommendations for individuals with various risks.

Conclusions

We constructed a novel cuproptosis-associated lncRNA signature with a significant predictive value for the prognosis of patients with HCC. Cuproptosis-associated lncRNAs are associated with the tumor immune microenvironment of HCC and even the efficacy of tumor immunotherapy.

Cuproptosis-related immune checkpoint gene signature: Prediction of prognosis and immune response for hepatocellular carcinoma

Immune checkpoint genes (ICGs), the foundation of immunotherapy, are involved in the incidence and progression of hepatocellular carcinoma (HCC). Cuproptosis is characterized by copper-induced cell death, and this novel cell death pathway has piqued the interest of researchers in recent years. It is worth noting that there is little information available in the literature to determine the relationship between cuproptosis and anti-tumor immunity. We identified 39 cuproptosis-related ICGs using ICGs co-expressed with cuproptosis-related genes. A prognostic risk signature was constructed using the Cox regression and the least absolute shrinkage and selection operator analysis methods. The signature was built using the Cancer Genome Atlas (TCGA)-Liver Hepatocellular Carcinoma database. The TCGA and International Cancer Genome Consortium cohorts were classified into two groups; the low- and high-risk groups were determined using a prognostic signature comprised of five genes. The multivariate Cox regression analysis revealed that the signature could independently predict overall survival. Furthermore, the level of immune infiltration analysis revealed the robustness of the prognostic signature-immune cell infiltration relationship observed for Tregs, macrophages, helper T cells, and naive B cells. Both groups showed significant differences in immune checkpoint expression levels. The gene enrichment analysis was used for characterization, and the results revealed that enriching various pathways such as PI3K-AKT-mTOR signaling, glycolysis, Wnt/beta-catenin signaling, and unfolded protein response could potentially influence the prognosis of patients with HCC and the level of immune infiltration. The sensitivity of the two groups of patients to various drug-targeted therapy methods and immunotherapy was analyzed. In conclusion, the findings presented here lay the foundation for developing individualized treatment methods for HCC patients. The findings also revealed that studying the cuproptosis-based pathway can aid in the prognosis of HCC patients. It is also possible that cuproptosis contributes to developing anti-tumor immunity in patients.

SIRPα maintains macrophage homeostasis by interacting with PTK2B kinase in Mycobacterium tuberculosis infection and through autophagy and necroptosis

Background

To determine whether SIRPα can be a diagnostic marker of pulmonary tuberculosis (PTB) and the molecular mechanism of SIRPα regulating macrophages to kill Mycobacterium tuberculosis (MTB).

Methods

Meta-analysis combined with subsequent qRT-PCR, western-blotting and flow cytometry assay were used to detect SIRPα expression in PTB patients. Cell-based assays were used to explore the regulation of macrophage function by SIRPα. SIRPα^−/- and wide type macrophages transplanted C57BL/6J mice were used to determine the function of SIRPα on MTB infection in vivo.

Findings

SIRPα levels are closely correlated with the treatment outcomes among PTB patients. Cell-based assay demonstrated that MTB significantly induces the expression of SIRPα on macrophages. SIRPα deficiency enhances the killing ability of macrophages against MTB through processes that involve enhanced autophagy and reduced necroptosis of macrophages. Mechanistically, SIRPα forms a direct interaction with PTK2B through its intracellular C-terminal domain, thus inhibiting PTK2B activation in macrophages. Necroptosis inhibition due to SIRPα deficiency requires PTK2B activity. The transfer of SIRPα-deficient bone marrow-derived macrophages (BMDMs) into wild type mice resulted in a drop of bacterial load in the lungs but an enhancement of inflammatory lung damage, and the combination of ulinastatin and SIRPα^−/−→WT treatment could decrease the inflammation and maintain the bactericidal capacity.

Interpretation

Our data define SIRPα a novel biomarker for tuberculosis infection and underlying mechanisms for maintaining macrophage homeostasis.

Funding

This work was financially supported by the Chinese National Natural Science Foundation project (No.81401635). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

MicroRNA-382 Promotes M2-Like Macrophage via the SIRP-α/STAT3 Signaling Pathway in Aristolochic Acid-Induced Renal Fibrosis

Aristolochic acid nephropathy (AAN) is a type of drug-induced nephropathy and is correlated with a potentially progression of kidney fibrosis. However, whether miR-382 is implicated in macrophage activation in AA-induced kidney fibrosis remains elusive. Here, cell-sorting experiments defined a significant miR-382 enrichment in renal macrophage after AAN 14 days. Then, we found that treatment of AA induced a significant switch in the phenotype of macrophage both in vivo and in vitro. Furthermore, miR-382 knockout (KO) mice and miR-382-/- bone marrow-derived macrophage (BMDM) were subjected to AA induction. We found that both systemic KO and macrophage-specific miR-382 depletion notably suppressed M2-like macrophage activation as well as kidney interstitial fibrosis. Additionally, adoptive transfer of miR-382 overexpression BMDMs into mice promoted AA-induced kidney injury. Moreover, in cultured macrophage, upregulation of miR-382 promoted M2-related gene expression, accompanied by downregulation of signal regulatory protein α (SIRP-α) and activation of signal transducer and activator of transcription 3 (STAT3). The interaction between miR-382 and SIRP-α was evaluated via dual-luciferase assay. Knockdown of SIRP-α upregulated phosphorylated STAT3 at S727 and Y705. Pharmacological inhibition of STAT3 was performed both in vivo and in vitro. Inhibition of STAT3 attenuated AA-induced kidney fibrosis, in parallel to lesser macrophage M2 polarization. Coculture experiments further confirmed that overexpressed miR-382 in macrophage promoted injuries of tubular cells. Luminex bio-chip detection suggested that IL-4 and CCL-5 were critical in the cross talk between macrophages and tubular cells. Taken together, our data suggest that miR-382 is a critical mediator in M2-like macrophage polarization and can be a promising therapeutic target for kidney fibrosis.

Monocytes engineered with iSNAP inhibit human B-lymphoma progression

Monocytes are important regulators for the maintenance of homeostasis in innate and adaptive immune system and have been reported to play important role in cancer progression. CD47-SIRPα recognition is a coinhibitory immune signal to inhibit phagocytosis in monocytes and macrophages and has been well-known as the "Don't eat me" signal. By using an approach of integrated sensing and activating proteins (iSNAPs), we have rewired the CD47-SIRPα axis to create iSNAP-M which activates pathways in engineered human monocytes (iSNAP-MC). The mRNA expression levels of the monocyte/macrophage markers CD11b, CD14, and CD31 are upregulated in iSNAP-monocytes (iSNAP-MC). With PMA induction, the iSNAP-MC-derived macrophages (iSNAP-MΦ) showed upregelation in CD86 and CD80, but not CD206. TNFα expression and secretion were also increased in iSNAP-MΦ. Furthermore, the injection of iSNAP-MC into mice bearing human B-lymphoma tumors led to the suppression of tumor progression. Therefore, the engineered monocytes, via blockage of coinhibitory immune signals by rewiring CD47-SIRPα axis, can be applied to suppress target tumors for cancer immunotherapy.

Suppression of the hyaluronic acid pathway induces M1 macrophages polarization via STAT1 in glioblastoma

Immunosuppressive tumor microenvironment is a crucial factor that impedes the success of tumor immunotherapy, and tumor-associated macrophages (TAMs) are essential for the formation of tumor immunosuppressive microenvironment. Hyaluronic acid (HA) is highly important brick for glioblastoma microenvironment, but whether it contributes to TAM polarization and glioblastoma immunosuppressive microenvironment is less well known. In our study, we observed that disrupting glioblastoma HA synthesis or blocking HA binding to its receptor CD44 on macrophages increased the proportion of M1 macrophages by upregulating SIRPα in macrophages, the underlying mechanism was elevated SIRPα enhanced STAT1 phosphorylation and suppressed STAT3 phosphorylation in macrophages. Subsequently, the induced macrophages could inhibit glioblastoma growth via a feedback effect. In addition, 4-methylumbelliferone (4MU), a cholecystitis drug, can disrupt the CD47/SIRPα axis by disturbing glioblastoma HA synthesis. Collectively, these findings indicated that HA plays a crucial role in macrophages polarization and CD47/SIRPα signaling between glioblastoma cells and macrophages, and suppressing the HA pathway may be a new immunotherapeutic approach for glioblastoma.

Context dependent isoform specific PI3K inhibition confers drug resistance in hepatocellular carcinoma cells

BACKGROUND

Targeted therapies for Primary liver cancer (HCC) is limited to the multi-kinase inhibitors, and not fully effective due to the resistance to these agents because of the heterogeneous molecular nature of HCC developed during chronic liver disease stages and cirrhosis. Although combinatorial therapy can increase the efficiency of targeted therapies through synergistic activities, isoform specific effects of the inhibitors are usually ignored. This study concentrated on PI3K/Akt/mTOR pathway and the differential combinatory bioactivities of isoform specific PI3K-α inhibitor (PIK-75) or PI3K-β inhibitor (TGX-221) with Sorafenib dependent on PTEN context.

METHODS

The bioactivities of inhibitors on PTEN adequate Huh7 and deficient Mahlavu cells were investigated with real time cell growth, cell cycle and cell migration assays. Differentially expressed genes from RNA-Seq were identified by edgeR tool. Systems level network analysis of treatment specific pathways were performed with Prize Collecting Steiner Tree (PCST) on human interactome and enriched networks were visualized with Cytoscape platform.

RESULTS

Our data from combinatory treatment of Sorafenib and PIK-75 and TGX-221 showed opposite effects; while PIK-75 displays synergistic effects on Huh7 cells leading to apoptotic cell death, Sorafenib with TGX-221 display antagonistic effects and significantly promotes cell growth in PTEN deficient Mahlavu cells. Signaling pathways were reconstructed and analyzed in-depth from RNA-Seq data to understand mechanism of differential synergistic or antagonistic effects of PI3K-α (PIK-75) and PI3K-β (TGX-221) inhibitors with Sorafenib. PCST allowed as to identify AOX1 and AGER as targets in PI3K/Akt/mTOR pathway for this combinatory effect. The siRNA knockdown of AOX1 and AGER significantly reduced cell proliferation in HCC cells.

CONCLUSIONS

Simultaneously constructed and analyzed differentially expressed cellular networks presented in this study, revealed distinct consequences of isoform specific PI3K inhibition in PTEN adequate and deficient liver cancer cells. We demonstrated the importance of context dependent and isoform specific PI3K/Akt/mTOR signaling inhibition in drug resistance during combination therapies. ( https://github.com/cansyl/Isoform-spesific-PI3K-inhibitor-analysis ).

A novel immune checkpoint-related gene signature for hepatocellular carcinoma to predict clinical outcomes and therapeutic response

Immune checkpoint genes (ICGs) have recently been proven to perform instrumental functions in the maintenance of immune homeostasis and represent a promising therapeutic strategy; however, their expression patterns and prognostic values are not fully elucidated in hepatocellular carcinoma (HCC). In this investigation, we focused on establishing and validating a prognostic gene signature to facilitate decision-making in clinical practice. Clinical information, as well as transcriptome data, was obtained from the Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) database. Univariate Cox regression and least absolute shrinkage and selection operator (LASSO) Cox method were employed to build a multi-gene signature in the TCGA database, while the ICGC database was used for validation. Subsequently, utilizing the six-gene signature, we were able to categorize patients into high- and low-risk groups. In two cohorts, survival analysis findings revealed a dismal outlook for the high-risk group. The receiver operating characteristic curves were utilized to estimate the gene signature's prediction ability. Moreover, correlation analysis showed high-risk group was linked to advanced pathological stage, infiltration of immune cells and therapeutic response. In summary, this unique gene profile might serve not only as a useful prognostic indicator but also as a marker of therapy responsiveness in HCC.

Selenium donor restricts the intracellular growth of Mycobacterium tuberculosis through the induction of c-Jun-mediated both canonical autophagy and LC3-associated phagocytosis of alveolar macrophages

The relationship between selenium and Mycobacterium tuberculosis (MTB) infection has been reported previously; however, the specific mechanism is still not clear. In this study, selenium levels decreased in the serum of patients with pulmonary tuberculosis (PTB) compared with the healthy controls; they were associated with the treatment outcome of such patients. The qRT-PCR assay revealed that selenium might function through proinflammatory and autophagy pathways. The treatment with methylseleninic acid (MSeA), a selenium donor, blocked the M1 polarization of MTB-infected macrophages through the induction of both canonical autophagy and LC3-associated phagocytosis (LAP). c-Jun is vital in mediating the MSeA-triggered canonical autophagy and LAP process, thus displaying a restricting function against intracellular MTB. An in vivo study confirmed that the activity of MSeA was shown through enhancing macrophage autophagy related pathway. The results showed that selenium had a restricting function against intracellular MTB by regulating autophagy in macrophages. The findings might provide a novel direction for PTB therapy in the future.

Clinical significance of signal regulatory protein alpha (SIRPα) expression in esophageal squamous cell carcinoma

Signal regulatory protein alpha (SIRPα) is a type I transmembrane protein that inhibits macrophage phagocytosis of tumor cells upon interaction with CD47, and the CD47‐SIRPα pathway acts as an immune checkpoint factor in cancers. This study aims to clarify the clinical significance of SIRPα expression in esophageal squamous cell carcinoma (ESCC). First, we assessed SIRPα expression using RNA sequencing data of 95 ESCC tissues from The Cancer Genome Atlas (TCGA) and immunohistochemical analytic data from our cohort of 131 patients with ESCC. Next, we investigated the correlation of SIRPα expression with clinicopathological factors, patient survival, infiltration of tumor immune cells, and expression of programmed cell death‐ligand 1 (PD‐L1). Overall survival was significantly poorer with high SIRPα expression than with low expression in both TCGA and our patient cohort (P < .001 and P = .027, respectively). High SIRPα expression was associated with greater depth of tumor invasion (P = .0017). Expression of SIRPα was also significantly correlated with the tumor infiltration of M1 macrophages, M2 macrophages, CD8⁺ T cells, and PD‐L1 expression (P < .001, P < .001, P = .03, and P < .001, respectively). Moreover, patients with SIRPα/PD‐L1 coexpression tended to have a worse prognosis than patients with expression of either protein alone or neither. Taken together, SIRPα indicates poor prognosis in ESCC, possibly through inhibiting macrophage phagocytosis of tumor cells and inducing suppression of antitumor immunity. Signal regulatory protein alpha should be considered as a potential therapeutic target in ESCC, especially if combined with PD‐1‐PD‐L1 blockade.

Nicotine promotes brain metastasis by polarizing microglia and suppressing innate immune function

Up to 40% of lung cancer patients develop brain metastasis, and the median survival of these patients remains less than 6 months. Smoking is associated with lung cancer. However, how smoking impacts the development of brain metastasis remains elusive. We examined 281 lung cancer patients with distant metastasis and found that smokers exhibited a significantly high incidence of brain metastasis. We found that nicotine enhanced brain metastasis, while a depletion of microglia suppressed this effect in vivo. Nicotine skewed the polarity of microglia to the M2 phenotype, thereby increasing the secretion of IGF-1 and CCL20, which promoted tumor progression and stemness. Importantly, nicotine enhanced the expression of SIRPα in microglia and restricted their phagocytic ability. We also identified a compound, parthenolide, that suppressed brain metastasis by blocking M2 polarization. Our results indicate that nicotine promotes brain metastasis by skewing the polarity of M2 microglia, which enhances metastatic tumor growth. Our results also highlight a potential risk of using nicotine for tobacco cessation.

Signaling of Macrophages that Contours the Tumor Microenvironment for Promoting Cancer Development

The immune response is critical in the maintenance of an organism’s health. The immune response can be broken down into two groups. The innate response, which is fast-acting and rids the body of most foreign material before infection occurs, and the adaptive response, a more specific defense against pathogen composed mostly of antibody production and killer cells. Linking the two responses via cytokine and chemokine secretion are macrophages, motile phagocytic cells that ingest and present foreign material playing a role in the innate and adaptive immune response. Although macrophages are necessary for the survival of an organism, studies have also shown macrophages play a more sinister role in the initiation, progression, and metastasis in tumorous cells. In this comprehensive review, we show how macrophages induce such a response through abnormal cellular signaling and creating a cellular microenvironment conducive for tumor growth and metastasis, as well as the future outlook of this field.

SIRPα expression delineates subsets of intratumoral monocyte/macrophages with different functional and prognostic impact in follicular lymphoma

Signal regulatory protein-α (SIRPα) is a key member of the “do-not-eat-me” signaling pathway, but its biological role and clinical relevance in B-cell NHL is relatively unknown. Using biopsy specimens from follicular lymphoma (FL), we identified three subsets (CD14⁺SIRPα^hi, CD14⁻SIRPα^low, and CD14⁻SIRPα^neg) of monocyte/macrophages (Mo/MΦ) based on CD14 and SIRPα expression. CD14⁺SIRPα^hi cells expressed common Mo/MΦ markers; exhibited characteristic differentiation, migration, and phagocytosis; and suppressed T-cell function. CD14⁻SIRPα^low cells expressed fewer typical Mo/MΦ markers; migrated less and phagocytosed tumor cells less efficiently; and stimulated rather than suppressed T-cell function. Interestingly, the CD14⁻SIRPα^neg subset expressed distinct Mo/MΦ markers compared to the other two subsets; had limited ability to migrate and phagocytose; but stimulated T-cell function. When using SIRPα-Fc to block the interaction between SIRPα and CD47, alone or in combination with rituximab, phagocytosis of tumor cells was differentially increased in the three Mo/MΦ subsets. Clinically, increased numbers of CD14⁺SIRPα^hi cells were associated with an inferior survival in FL. In contrast, increased numbers of the CD14⁻SIRPα^low subset appeared to correlate with a better survival. Taken together, our results show that SIRPα expression delineates unique subsets of intratumoral Mo/MΦs with differing prognostic importance.

Signal regulatory protein alpha blockade potentiates tumoricidal effects of macrophages on gastroenterological neoplastic cells in syngeneic immunocompetent mice

AIM

Immunotherapies blocking the CD47-SIRPα pathway by targeting CD47 enhance macrophage phagocytosis of neoplastic cells in mouse models. As SIRPα exhibits relatively restricted tissue expression, SIRPα antagonists may be better tolerated than agents targeting CD47, which is ubiquitously expressed in many tissues. Here, we investigated the therapeutic impact of monoclonal antibodies (mAbs) against CD47 and/or SIRPα on gastroenterological tumors in syngeneic immunocompetent mouse models.

METHODS

We used in vitro and in vivo phagocytosis assays in C57BL/6J (B6) mice to investigate anti-CD47/SIRPα mAb effects on Hepa1-6 and CMT93 originating from B6 mice. The influence of these mAbs on macrophage transmigration was also assessed. To investigate anti-SIRPα mAb therapy-induced inhibitory effects on sporadic colon cancer growth, we used a CDX2P9.5-NLS Cre;APC + /FLOX (CPC-APC) mouse model.

RESULTS

Systemic anti-SIRPα mAb administration significantly increased Hepa1-6 and CMT93 cell susceptibility to macrophage phagocytosis, both in vitro and in vivo. Conversely, similarly administered anti-CD47 mAb did not promote macrophage phagocytosis of target cells, whereas cells incubated with anti-CD47 mAb prior to inoculation were more susceptible to macrophage phagocytosis. In vitro cell migration assays revealed that binding with anti-CD47 mAb inhibited macrophage transmigration. Anti-SIRPα mAb treatment inhibited tumor progression in CPC-APC mice and significantly improved overall survival. Anti-CD47 mAb administration in vivo eliminated the phagocytosis-promoting CD47 blockade effect, probably by inhibiting macrophage transmigration/chemotaxis. In contrast, anti-SIRPα mAb exhibited enhanced macrophage phagocytic activity and marked anti-tumor effects against gastroenterological malignancies.

CONCLUSION

SIRPα mAb augmentation of macrophage phagocytic activity may represent an effective treatment strategy for human gastrointestinal tumors.

Histone deacetylase 2 is essential for LPS-induced inflammatory responses in macrophages

The role of specific histone deacetylase (HDAC) proteins in regulating the lipopolysaccharide (LPS)‐induced inflammatory response and its underlying mechanisms are unclear. Here, HDAC2, a class I HDAC family protein, is essential for the LPS‐triggered inflammatory response in macrophages. LPS stimulation increases HDAC2 expression in macrophages. Knockdown of HDAC2 decreases the expression of proinflammatory genes, such as IL‐12, TNF‐α and iNOS following stimulation with LPS. The adoptive transfer of HDAC2 knockdown macrophages attenuates the LPS‐triggered innate inflammatory response in vivo, and these mice are less sensitive to endotoxin shock and Escherichia coli‐induced sepsis. Mechanistically, the c‐Jun protein is the main target of HDAC2‐mediated LPS‐induced production of proinflammatory cytokines. Moreover, HDAC2 knockdown increases the expression of c‐Jun, which directly binds the promoters of proinflammatory genes and forms nuclear receptor corepressor complexes to inhibit the transcription of proinflammatory genes in macrophages. These effects are rescued by c‐Jun expression. According to the chromatin immunoprecipitation analysis, HDAC2 also selectively suppresses c‐Jun expression by directly binding to its promoter and modifying histone acetylation after LPS stimulation. Our findings define a new function and mechanism of the HDAC2/c‐Jun signaling network that regulates the LPS‐induced immune response in macrophages.

Notch Signaling Modulates Macrophage Polarization and Phagocytosis Through Direct Suppression of Signal Regulatory Protein α Expression

The Notch pathway plays critical roles in the development and functional modulation of myeloid cells. Previous studies have demonstrated that Notch activation promotes M1 polarization and phagocytosis of macrophages; however, the downstream molecular mechanisms mediating Notch signal remain elusive. In an attempt to identify Notch downstream targets in bone marrow-derived macrophages (BMDMs) using mass spectrometry, the signal regulatory protein α (SIRPα) appeared to respond to knockout of recombination signal-binding protein Jk (RBP-J), the critical transcription factor of Notch pathway, in macrophages. In this study, we validated that Notch activation could repress SIRPα expression likely via the Hes family co-repressors. SIRPα promoted macrophage M2 polarization, which was dependent on the interaction with CD47 and mediated by intracellular signaling through SHP-1. We provided evidence that Notch signal regulated macrophage polarization at least partially through SIRPα. Interestingly, Notch signal regulated macrophage phagocytosis of tumor cells through SIRPα but in a SHP-1-independent way. To access the translational value of our findings, we expressed the extracellular domains of the mouse SIRPα (mSIRPα^ext) to block the interaction between CD47 and SIRPα. We demonstrated that the soluble mSIRPα^ext polypeptides could promote M1 polarization and increase phagocytosis of tumor cells by macrophages. Taken together, our results provided new insights into the molecular mechanisms of notch-mediated macrophage polarization and further validated SIRPα as a target for tumor therapy through modulating macrophage polarization and phagocytosis.

Arginase-1 is neither constitutively expressed in nor required for myeloid-derived suppressor cell-mediated inhibition of T-cell proliferation

Although previous reports suggest that tumor-induced myeloid-derived suppressor cells (MDSC) inhibit T cells by L-arginine depletion through arginase-1 activity, we herein show that arginase-1 is neither inherently expressed in MDSC nor required for MDSC-mediated inhibition. Employing Percoll density gradients, large expansions of MDSC in the bone marrow of tumor-bearing mice were isolated and demonstrated potent inhibition in T-cell proliferation activated by TCR-ligation, Concanavalin A, PMA plus ionomycin, or IL-2. Despite demonstrating characteristic immunosuppressive capacity, these MDSC exhibit no arginase-1 expression and/or exert their inhibitory effects independent of arginase-1 activity. However, arginase-1 expression in MDSC can be induced by exposure to TCR-activated T cells or their culture medium, but not T cells activated by other means or growing tumor cells. Further investigation reveals multiple cytokines secreted by TCR-activated T cells as orchestrating two signaling-relay axes, IL-6-to-IL-4 and GM-CSF/IL-4-to-IL-10, leading to arginase-1 expression in MDSC. Specifically, IL-6 signaling increases IL-4R, enabling IL-4 to induce arginase-1 expression; similarly, GM-CSF in concert with IL-4 induces IL-10R, allowing IL-10-mediated induction. Surprisingly, our study indicates that induction of arginase-1 expression is not conducive to the critical MDSC-mediated inhibition toward T cells, which is rather dependent on direct cell contacts undiminished by PD-L1 blockade or SIRPα deficiency.

Signal regulatory protein α associated with the progression of oral leukoplakia and oral squamous cell carcinoma regulates phenotype switch of macrophages

Signal regulatory protein α (SIRPα) is a cell-surface protein expressed on macrophages that are regarded as an important component of the tumor microenvironment. The expression of SIRPα in oral leukoplakia (OLK) and oral squamous cell carcinoma (OSCC), and further explored the role of SIRPα on the phenotype, phagocytosis ability, migration, and invasion of macrophages in OSCC were investigated. The expression of SIRPα in OLK was higher than in OSCC, correlating with the expression of CD68 and CD163 on macrophages. After cultured with the conditioned media of oral cancer cells, the expression of SIRPα on THP-1 cells was decreased gradually. In co-culture system, macrophages were induced into M2 phenotype by oral cancer cells. Blockade of SIRPα inhibited phagocytosis ability and IL-6, TNF-α productions of macrophages. In addition, the proliferation, migration, and IL-10, TGF-β productions of macrophages were upregulated after blockade of SIRPα. Macrophages upregulated the expression of SIRPα and phagocytosis ability, and inhibited the migration and invasion when the activation of NF-κB was inhibited by pyrrolidine dithiocarbamate ammonium (PDTC). Hence, SIRPα might play an important role in the progression of OLK and oral cancer, and could be a pivotal therapeutic target in OSCC by regulating the phenotype of macrophages via targeting NF-κB.

Phylogenetic, antigenic and biological characterization of pigeon paramyxovirus type 1 circulating in China

Background

For many years, ND has been one of the most important infectious pigeon diseases in China. In recent years, a high mortality has been observed in ND-infected pigeons in China. Mortality is from 40% to 80% or 100% in some cases.

Methods

The full-length genomes of four pigeon paramyxovirus type 1 (PPMV-1) strains, which were isolated from infected pigeons in China in 2012 and 2013, were sequenced and analyzed to determine the phylogenetic characteristics of PPMV-1 circulating in pigeons of China in recent years. Furthermore, cross hemagglutination inhibition and cross virus neutralization assays, as well as animal experiments were conducted to determine the antigenicity and pathogenicity of those viruses. Proteolytic cleavage sites (residues 112–117) of the F proteins were identified as the typical virulence motif, ¹¹²RRQKR↓F¹¹⁷ for all four PPMV-1 strains investigated.

Results

Phylogenetic analysis based on sequences of complete genomes and F gene revealed that the four PPMV-1 isolates and most of recent isolates in China were highly homologous to European isolates from 1998 to 2011. All those isolates were clustered in one clade of genotype VI NDV, termed as subgroup 4bii f. The R value was calculated based on cross hemagglutination inhibition and cross virus neutralization results, and confirmed antigenic difference of the PPMV-1 strains isolated in 2013 from the LaSota vaccine strain. Several mutations were identified in the surface glycoproteins F and HN, which probably gave rise to those antigenic differences.

Conclusion

Our result suggested that the PPMV-1 strain prevailing in China in the last decade diverged from a common ancestor and was presumably transmitted from Europe. PPMV-1 isolates displayed obvious antigenic differences from vaccine strain LaSota. Even though PPMV-1 did not cause high mortality in experimental pigeons, the infected pigeons were exhibiting viral shedding for 3 weeks after infection, suggesting PPMV-1 is a potential threat to NDV control worldwide.

Electronic supplementary material

The online version of this article (10.1186/s12985-017-0857-7) contains supplementary material, which is available to authorized users.

Immune-camouflaged graphene oxide nanosheets for negative regulation of phagocytosis by macrophages

Signal regulatory protein alpha (SIRPα) is highly expressed in macrophages of the reticuloendothelial system and in tumor-associated macrophages, whereas tumor cells express the surface membrane protein, CD47, which interacts with SIRPα to negatively regulate phagocytosis. In this study, we modified the surfaces of graphene oxide (GO) nanosheets with a CD47-like SIRPα-binding peptide (SP). The presence of SP on GO nanosheets reduced the macrophage uptake to a greater extent than the PEGylation of such nanosheets. This reduced uptake was found to be mediated by the activation of Src homology region 2 domain-containing phosphatase 1 (SHP-1) and the downstream inhibition of myosin assembly, which is necessary for phagosome formation. Unlike SP-coated GO nanosheets, PEGylated GO nanosheets did not affect myosin assembly or phagocytosis. After in vivo systemic administration, the clearance of SP-coated GO nanosheets was slower than that of PEGylated GO nanosheets, and this difference increased with repeated administration. Finally, SP-coated GO nanosheets showed a higher distribution to tumor tissues than PEGylated GO nanosheets or a physical mixture of SP and GO nanosheets. Our findings indicate that immune-camouflaged GO nanosheets with natural CD47-like SIRPα-binding molecules can reduce the nonspecific loss of such nanosheets through macrophage uptake, thereby enhancing their blood circulation and tumor delivery after multiple injections.

Engineering macrophages to eat cancer: from "marker of self" CD47 and phagocytosis to differentiation

The ability of a macrophage to engulf and break down invading cells and other targets provides a first line of immune defense in nearly all tissues. This defining ability to "phagos" or devour can subsequently activate the entire immune system against foreign and diseased cells, and progress is now being made on a decades-old idea of directing macrophages to phagocytose specific targets, such as cancer cells. Engineered T cells provide precedence with recent clinical successes against liquid tumors, but solid tumors remain a challenge, and a handful of clinical trials seek to exploit the abundance of tumor-associated macrophages instead. Although macrophage differentiation into such phenotypes with deficiencies in phagocytic ability can raise challenges, newly recognized features of cancer cells that might be manipulated to increase the phagocytosis of those cells include ≥1 membrane protein, CD47, which broadly inhibits phagocytosis and is abundantly expressed on all healthy cells. Physical properties of the target also influence phagocytosis and again relate-via cytoskeleton forces-to differentiation pathways in solid tumors. Such pathways extend to mechanosensing by the nuclear lamina, which is known to influence signaling by soluble retinoids that can regulate the macrophage SIRPα, the receptor for CD47. Here, we highlight some of those past, present, and rapidly emerging efforts to understand and control macrophages for cancer therapy.

SIRPA-Inhibited, Marrow-Derived Macrophages Engorge, Accumulate, and Differentiate in Antibody-Targeted Regression of Solid Tumors

Marrow-derived macrophages are highly phagocytic, but whether they can also traffic into solid tumors and engulf cancer cells is questionable, given the well-known limitations of tumor-associated macrophages (TAMs). Here, SIRPα on macrophages from mouse and human marrow was inhibited to block recognition of its ligand, the "marker of self" CD47 on all other cells. These macrophages were then systemically injected into mice with fluorescent human tumors that had been antibody targeted. Within days, the tumors regressed, and single-cell fluorescence analyses showed that the more the macrophages engulfed, the more they accumulated within regressing tumors. Human-marrow-derived macrophages engorged on the human tumors, while TAMs were minimally phagocytic, even toward CD47-knockdown tumors. Past studies had opsonized tumors in situ with antibody and/or relied on mouse TAMs but had not injected SIRPα-inhibited cells; also, unlike past injections of anti-CD47, blood parameters remained normal and safe. Consistent with tumor-selective engorge-and-accumulate processes in vivo, phagocytosis in vitro inhibited macrophage migration through micropores that mimic features of dense 3D tissue. Accumulation of SIRPα-inhibited macrophages in tumors favored tumor regression for 1-2 weeks, but donor macrophages quickly differentiated toward non-phagocytic, high-SIRPα TAMs. Analyses of macrophages on soft (like marrow) or stiff (like solid tumors) collagenous gels demonstrated a stiffness-driven, retinoic-acid-modulated upregulation of SIRPα and the mechanosensitive nuclear marker lamin-A. Mechanosensitive differentiation was similarly evident in vivo and likely limited the anti-tumor effects, as confirmed by re-initiation of tumor regression by fresh injections of SIRPα-inhibited macrophages. Macrophage motility, phagocytosis, and differentiation in vivo are thus coupled.

Genome variation across cancers scales with tissue stiffness - an invasion-mutation mechanism and implications for immune cell infiltration

Many different types of soft and solid tumors have now been sequenced, and meta-analyses suggest that genomic variation across tumors scales with the stiffness of the tumors' tissues of origin. The opinion expressed here is based on a review of current genomics data, and it considers multiple 'mechanogenomics' mechanisms to potentially explain this scaling of mutation rate with tissue stiffness. Since stiff solid tissues have higher density of fibrous collagen matrix, which should decrease tissue porosity, cancer cell proliferation could be affected and so could invasion into stiff tissues as the nucleus is squeezed sufficiently to enhance DNA damage. Diversification of a cancer genome after constricted migration is now clear. Understanding genome changes that give rise to neo-antigens is important to selection as well as to the development of immunotherapies, and we discuss engineered monocytes/macrophages as particularly relevant to understanding infiltration into solid tumors.

Anti-SIRP antibodies as a potential new tool for cancer immunotherapy

Tumor cells are thought to evade immune surveillance through interaction with immune cells. Much recent attention has focused on the modification of immune responses as a basis for new cancer treatments. SIRPα is an Ig superfamily protein that inhibits phagocytosis in macrophages upon interaction with its ligand CD47 expressed on the surface of target cells. Here, we show that SIRPα is highly expressed in human renal cell carcinoma and melanoma. Furthermore, an anti-SIRPα Ab that blocks the interaction with CD47 markedly suppressed tumor formation by renal cell carcinoma or melanoma cells in immunocompetent syngeneic mice. This inhibitory effect of the Ab appeared to be mediated by dual mechanisms: direct induction of Ab-dependent cellular phagocytosis of tumor cells by macrophages and blockade of CD47-SIRPα signaling that negatively regulates such phagocytosis. The antitumor effect of the Ab was greatly attenuated by selective depletion not only of macrophages but also of NK cells or CD8⁺ T cells. In addition, the anti-SIRPα Ab also enhances the inhibitory effects of Abs against CD20 and programmed cell death 1 (PD-1) on tumor formation in mice injected with SIRPα-nonexpressing tumor cells. Anti-SIRPα Abs thus warrant further study as a potential new therapy for a broad range of cancers.

Anti-CD47 Treatment Stimulates Phagocytosis of Glioblastoma by M1 and M2 Polarized Macrophages and Promotes M1 Polarized Macrophages In Vivo

Tumor-associated macrophages (TAMs) represent an important cellular subset within the glioblastoma (WHO grade IV) microenvironment and are a potential therapeutic target. TAMs display a continuum of different polarization states between antitumorigenic M1 and protumorigenic M2 phenotypes, with a lower M1/M2 ratio correlating with worse prognosis. Here, we investigated the effect of macrophage polarization on anti-CD47 antibody-mediated phagocytosis of human glioblastoma cells in vitro, as well as the effect of anti-CD47 on the distribution of M1 versus M2 macrophages within human glioblastoma cells grown in mouse xenografts. Bone marrow-derived mouse macrophages and peripheral blood-derived human macrophages were polarized in vitro toward M1 or M2 phenotypes and verified by flow cytometry. Primary human glioblastoma cell lines were offered as targets to mouse and human M1 or M2 polarized macrophages in vitro. The addition of an anti-CD47 monoclonal antibody led to enhanced tumor-cell phagocytosis by mouse and human M1 and M2 macrophages. In both cases, the anti-CD47-induced phagocytosis by M1 was more prominent than that for M2. Dissected tumors from human glioblastoma xenografted within NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice and treated with anti-CD47 showed a significant increase of M1 macrophages within the tumor. These data show that anti-CD47 treatment leads to enhanced tumor cell phagocytosis by both M1 and M2 macrophage subtypes with a higher phagocytosis rate by M1 macrophages. Furthermore, these data demonstrate that anti-CD47 treatment alone can shift the phenotype of macrophages toward the M1 subtype in vivo.

Macrophage activation marker soluble CD163 may predict disease progression in hepatocellular carcinoma

BACKGROUND

Tumor associated macrophages are present in hepatocellular carcinoma (HCC) and associated with a poor prognosis. The aim of the present study was to investigate the levels and dynamics of soluble (s)CD163, a specific macrophage activation marker, in patients with HCC.

METHODS

In a cohort from Australia, we studied 109 HCC patients, 116 patients with chronic liver disease (CLD), and 52 healthy controls. We examined associations between baseline sCD163 and parameters of HCC severity as well as overall and progression-free survival. In a cohort of 42 Danish HCC patients, we measured sCD163 at baseline and 1, 4 and 12 weeks after ablative treatment.

RESULTS

In the Australian cohort, median sCD163 was similarly increased in HCC (5.6[interquartile range 3.5-8.0] mg/L) and CLD (6.1[3.6-9.6] mg/L) patients as compared to controls (2.0[1.5-2.7] mg/L, p < 0.001). sCD163 correlated with Child-Pugh and MELD scores in both HCC and CLD patients. Patients with high sCD163 levels had shorter progression-free survival (p < 0.001), but not overall survival (p = 0.15). In the Danish cohort, patients with HCC progression at 12 weeks had an increase in sCD163. There was no association between sCD163 and HCC size, number, vascular invasion or metastasis in any of the cohorts.

CONCLUSIONS

We confirmed increased sCD163 levels in CLD and HCC patients associated with Child-Pugh and MELD scores and portal hypertension, but not with HCC size and number, or metastasis. As a novel finding, baseline sCD163 appeared to predict a rapid HCC progression, as sCD163 increased during follow-up in HCC patients who showed progression.

Heterogeneity of liver cancer and personalized therapy

Liver cancer is an extraordinarily heterogeneous malignant disease among the tumors that have so far been identified. Hepatocellular carcinoma (HCC) arises most frequently in the setting of chronic liver inflammation and fibrosis, and takes a variety of course in individual patients to process to tumor. The risk factors such as HBV and/or HCV infections, aflatoxin infection, abuse alcohol intake, metabolic syndrome, obesity and diabetes are closely related to the environmental and genetic susceptibilities to HCC. The consequent resulting genomic instability, molecular and signal transduction network disorders and microenvironmental discrepancies are characterized by the extraordinary heterogeneity of liver cancer. The histology-based definition of the morphological heterogeneity of liver cancer has been modified and refined to treat patients with targeted therapies, but this still cannot solve all the problems. Lack of consistent outcome for anticancer agents and conventional therapies in liver cancer treatment calls for assessing the benefits of new molecularly targeted drugs and combined therapy, under the heterogeneity condition of tumor. The present review article will provide the complex mechanism and phenotype of liver cancer heterogeneity, and help us to execute precision medicine in a really personalized manner.

PTPROt maintains T cell immunity in the microenvironment of hepatocellular carcinoma

Intratumoral T cells play a central role in anti-tumor immunity, and the balance between T effector cells (Teff) and regulatory T cells (Treg) affects the prognosis of cancer patients. However, educated by tumor microenvironment, T cells frequently fail in their responsibility. In this study, we aimed to investigate the role of truncated isoform of protein tyrosine phosphatase receptor-type O (PTPROt) in T cell-mediated anti-tumor immunity. We recruited 70 hepatocellular carcinoma (HCC) patients and 30 healthy volunteers for clinical investigation, and analyzed cellular tumor immunity by using ptpro(-/-) C57BL/6 mice and NOD/SCID mice. PTPROt expression was significantly downregulated in human HCC-infiltrating T cells due to the hypoxia microenvironment; PTPROt expression highly correlated with the intratumoral Teff/Treg ratio and clinicopathologic characteristics. Moreover, PTPROt deficiency attenuated T cell-mediated anti-tumor immunity and remarkably promoted mouse HCC growth. Mechanistically, deletion of PTPROt decreased Teff quantity and quality through phosphorylation of lymphocyte-specific tyrosine kinase, but increased Treg differentiation through phosphorylation of signal transducer and activator of transcription 5. In support of the Teff/Treg homeostasis, PTPROt serves as an important tumor suppressor in HCC microenvironment.

Activation of glioma cells generates immune tolerant NKT cells

Therapeutic outcomes of glioma are currently not encouraging. Tumor tolerance plays an important role in the pathogenesis of glioma. It is reported that micro RNAs (miR) are associated with tumor development. This study aims to investigate the role of miR-92a in the development of tolerant natural killer T (NKT) cells. In this study, U87 cells (a human glioma cell line) and primary glioma cells were prepared. The assessment of miR-92a was performed by real time RT-PCR. The expression of interleukin (IL)-10 and IL-6 in NKT cells was evaluated by flow cytometry. Results showed that abundant IL-6(+) IL-10(+) NKT cells were detected in glioma tissue. Cultures of glioma cells and NKT cells induced the expression of IL-6 and IL-10 in NKT cells. Glioma cells expressed miR-92a; the latter played a critical role in the induction of IL-6 and IL-10 expression in NKT cells. The expression of the antitumor molecules, including perforin, Fas ligand, and interferon-γ, was significantly attenuated compared with control NKT cells. The IL-6(+) IL-10(+) NKT cells showed less capability in the induction of apoptosis in glioma cells, but showed the immune suppressor functions on CD8(+) T cell activities. We conclude that glioma-derived miR-92a induces IL-6(+) IL-10(+) NKT cells; this fraction of NKT cells can suppress cytotoxic CD8(+) T cells.