Metformin prevents cancer metastasis by inhibiting M2-like polarization of tumor associated macrophages

Accumulated evidence suggests that M2-like polarized tumor associated macrophages (TAMs) plays an important role in cancer progression and metastasis, establishing TAMs, especially M2-like TAMs as an appealing target for therapy intervention. Here we found that metformin significantly suppressed IL-13 induced M2-like polarization of macrophages, as illustrated by reduced expression of CD206, down-regulation of M2 marker mRNAs, and inhibition of M2-like macrophages promoted migration of cancer cells and endothelial cells. Metformin triggered AMPKα1 activation in macrophage and silencing of AMPKα1 partially abrogated the inhibitory effect of metformin in IL-13 induced M2-like polarization. Administration of AICAR, another activator of AMPK, also blocked the M2-like polarization of macrophages. Metformin greatly reduced the number of metastases of Lewis lung cancer without affecting tumor growth. In tumor tissues, the percentage of M2-like macrophage was decreased and the area of pericyte-coated vessels was increased. Further, the anti-metastatic effect of metformin was abolished when the animals were treated with macrophages eliminating agent clodronate liposome. These findings suggest that metformin is able to block the M2-like polarization of macrophages partially through AMPKα1, which plays an important role in metformin inhibited metastasis of Lewis lung cancer.     

肿瘤相关巨噬细胞对恶性肿瘤临床预后和治疗的影响

肿瘤相关巨噬细胞(tumor-associated macrophages,TAMs)作为肿瘤微环境中(tumor microenvi-ronment,TME)的核心调控者在肿瘤的发生发展中具有重要作用.活化的肿瘤相关巨噬细胞可分化出具有不同活化状态和功能的M1型和M2型,M1型肿瘤相关巨噬细胞主要介导抗肿瘤免疫效应,...     

TGF-β-induced IRAK-M expression in tumor-associated macrophages regulates lung tumor growth

Tumor-associated macrophages (TAMs) constitute a major component of the immune cell infiltrate observed in the tumor microenvironment (TME). Factors present in the TME, including tumor growth factor-β (TGF-β), allow tumors to circumvent host-mediated immune responses to promote tumor progression. However, the molecular mechanism(s) involved are not clear. Toll-like receptors (TLRs) are important mediators of innate immune responses by immune cells, whose activation triggers the production of molecules required for anti-tumoral responses. Interleukin (IL) receptor-associated kinase (IRAK)-M is an inactive serine/threonine kinase, predominantly expressed in macrophages and is a potent negative regulator of TLR signaling. In this study, we show that TAMs express significantly higher levels of IRAK-M compared with peritoneal macrophages in a syngeneic mouse model of lung cancer. Subcutaneous implantation of Lewis lung carcinoma cells in IRAK-M(-/-) mice resulted in a five-fold reduction in tumor growth as compared with tumors in wild-type (WT) animals. Furthermore, compared with WT TAMs, TAMs isolated from IRAK-M(-/-) mice displayed features of a classically activated (M1) rather than alternatively activated (M2) phenotype, as manifest by greater expression of IL-12, interferon-γ (IFN-γ) and inducible nitric oxide synthase. Human lung cancer cells induced IRAK-M expression in human peripheral blood mononuclear cells (PBMCs) when co-cultured together. Tumor cell-induced expression of IRAK-M was dependent on the activation of TGF-β pathway. Similarly, treatment of human PBMCs or mouse macrophage cell line, RAW 264.4, with TGF-β, induced IRAK-M expression. Interestingly, IRAK-M gene expression in 439 human lung adenocarcinoma tumors correlated with poor survival in patients with lung cancer. Together, our data demonstrates that TGF-β-dependent induction of IRAK-M expression is an important, clinically relevant mechanism by which tumors may circumvent anti-tumor responses of macrophages.     

The effect and mechanism of nimesulide combined with cisplatin on proliferation and apoptosis of lung cancer

Objective To evaluate the effects of selective cyclooxygenase-2 inhibitor nimesulide lone and combined with cisplatin on tumor growth, Ki67 and Caspase-3 expression in lung cancer xenografts in nude mice. Methods The mice were randomly divided into 4 groups: the control group, the nimesulide group, the cisplatin group and the nimesulide combined with cisplatin group. A549 cells were injected into BALB／c nude mice subcutaneously. On the 21nd day after treatment tumor tissues were collected, and the xenografts growth were observed. The expression of Ki67 and Caspase-3 were detected by immunohistochemical method. Results Nimesulide combined with cisplatin could significantly inhibited the xenografts growth compared with nimesulide or cisplatin. The tumor inhibition rate was 44.33％ in the nimesulide group, 53.61％ in the cisplatin group and 80.41％ in the nimesulide combined with cisplatin group (P<0.05). Immunohistochemical analysis showed that the expression rates of caspase-3 was significantly increased in the nimesulide combined with cisplatin group (67.43±23.57)%, the cisplatin group (48.40±20.37)%, and the nimesulide group (38.65±15.37)%, compared with the control group (27.63±13.03)% (P <0.05). The expression rate of Caspase-3 was significantly increased in the nimesulide combined with cisplatin group compared with the nimesulide group or the cisplatin group (P<0.05). The expression rate of Ki67 was significantly decreased in the nimesulide group combined with cisplatin group (24.34±15.90)%, the cisplatin group (40.85±22.47)% and the nimesulide group (53.33±19.67)% compared with the control group (80.43±16.88)% (P<0.05). The expression of Ki67 was significantly decreased in the nimesulide combined with cisplatin group compared with the nimesulide group or the cisplatin group (P <0.05). Conclusion Nimesulide can inhibit human lung cancer A549 cells xenografts in nude mice growth, Nimesulide enhanced the inhibitory effects of cisplatin. The mechanism may be related to inhibition of tumor cell Ki-67 expression, increased expression of Caspase-3, inhibition of tumor cell proliferation, and inducing tumor cell apoptosis.     

肿瘤相关巨噬细胞糖代谢重编程及靶向治疗

肿瘤相关巨噬细胞（tumor-associated macrophages,TAMs）作为肿瘤微环境（tumor microenvironment,TME）中重要的免疫细胞,具有高度异质性及可塑性,在肿瘤细胞分泌的细胞因子刺激下,可发生表型、代谢及功能变化。TAMs代谢改变以糖代谢重编程为主,M1型TAMs有氧糖酵解、磷酸戊糖途径增强,三羧酸循环减弱,具有抗肿瘤功能;M2型TAMs具有完整的三羧酸循环,可促进肿瘤进展。而在TME作用下TAMs具有多种表现形式,其糖代谢重编程可影响肿瘤迁移、侵袭及血管生成,而具体作用机制尚不明确。本文旨在探讨TAMs糖代谢重编程作用机制及其与肿瘤免疫相关性,提示TME中TAMs糖代谢重编程对肿瘤发展和靶向治疗有重要意义,可为肿瘤治疗提供新思路。     

SI-CLP inhibits the growth of mouse mammary adenocarcinoma by preventing recruitment of tumor-associated macrophages

Chitinase-like proteins (CLP) are chitin-binding proteins that lack chitin hydrolyzing activity, but possess cytokine-like and growth factor-like properties, and play crucial role in intercellular crosstalk. Both human and mice express two members of CLP family: YKL-40 and stabilin-1 interacting chitinase-like protein (SI-CLP). Despite numerous reports indicating the role of YKL-40 in the support of angiogenesis, tumor cell proliferation, invasion and metastasis, the role of its structurally related protein SI-CLP in cancer was not reported. Using gain-of-function approach, we demonstrate in the current study that the expression of recombinant SI-CLP in mouse TS/A mammary adenocarcinoma cells results in significant and persistent inhibition of in vivo tumor growth. Using quantitative immunohistochemistry, we show that on the cellular level this phenomenon is associated with reduced infiltration of tumor-associated macrophages (TAMs), CD4+ and FoxP3+ cells in SI-CLP expressing tumors. Gene expression analysis in TAM isolated from SI-CLP-expressing and control tumors demonstrated that SI-CLP does not affect macrophage phenotype. However, SI-CLP significantly inhibited migration of murine bone-marrow derived macrophages and human primary monocytes toward monocyte-recruiting chemokine CCL2 produced in the tumor microenvironment (TME). Mechanistically, SI-CLP did not affect CCL2/CCR2 interaction, but suppressed cytoskeletal rearrangements in response to CCL2. Altogether, our data indicate that SI-CLP functions as a tumor growth inhibitor in mouse breast cancer by altering cellular composition of TME and blocking cytokine-induced TAM recruitment. Taking into consideration weak to absent expression of SI-CLP in human breast cancer, it can be considered as a therapeutic protein to block TAM-mediated support of breast tumor growth.     

结直肠癌免疫微环境中肿瘤相关巨噬细胞的作用

结直肠癌（colorectal cancer,CRC）的发生、发展不仅与肿瘤细胞本身的特性相关,也与肿瘤微环境（tumor microenvironment,TME）密切相关。肿瘤细胞及其微环境通过分泌多种细胞因子,将循环血液中的单核细胞招募至TME并使其极化为肿瘤相关巨噬细胞（tumor-associated macrophages,TAMs）。作为TME中最丰富的免疫细胞之一,TAMs的功能和特点与M2型巨噬细胞相似,TAMs主要具有刺激肿瘤细胞增殖、血管生成、基质重塑和促进肿瘤细胞侵袭及转移等作用。在多数肿瘤中,TAMs主要发挥促肿瘤作用并与患者的不良预后相关;但在CRC中,TAMs的作用仍存争议。本文主要就CRC免疫微环境中TAMs的作用及其机制进行综述,以展示TAMs对CRC患者的病程进展及预后的影响并探讨TAMs作为CRC免疫治疗靶点的可行性。      

Tumor-Associated Macrophages Facilitate the Proliferation and Migration of Cervical Cancer Cells

Tumor-associated macrophages (TAMs) are important components in tumor microenvironment. This study intended to explore the influence of TAMs on cervical cancer cells proliferation and migration. The expression levels of TAMs markers, CD68 and CD163, in tissues were examined by immunohistochemistry and increased with the progression of cervical lesions (p < 0.05). TAMs with M2-like phenotype (PMA(Polymethacrylate) induced THP-1 cells) were noticed to promote the proliferation of cervical cancer cells and improve the migration ability of tumor cells. These enhancements were attributed to secreting soluble components and the physical contact between macrophages and tumor cells. The tumor formation and tumor growth were significantly faster in the mixed group of induced THP-1 cells and SiHa than in the SiHa cells alone group (p < 0.05). The results indicated that the interaction of macrophages and cervical cancer cells, including the secretion of soluble components and physical contact, were responsible for shaping immunosuppression microenvironments and in promoting tumor cell proliferation and migration.     

M2型肿瘤相关巨噬细胞在肺癌中的研究进展

肿瘤相关巨噬细胞（TAMs）在肿瘤间质中占有很大的比例,可分为M1型（抗肿瘤型）与 M2型（促肿瘤型）。近来诸多实验和临床研究均表明M2型肿瘤相关巨噬细胞与肿瘤的分期、肿瘤细胞分化程度、浸润深度、新生血管的产生、淋巴结转移和治疗耐药具有显著相关性,影响肿瘤患者的预后。靶向TAMs的治疗有望使肿瘤患者获益。因此,本文就M2型TAMs在肺癌中相关研究进展进行综述。     

Prostate cancer-derived CCN3 induces M2 macrophage infiltration and contributes to angiogenesis in prostate cancer microenvironment

Tumor-associated macrophages (TAMs) are M2-polarized macrophages that infiltrate the tumor microenvironment and promote tumorigenesis. However, the mechanisms by which TAMs modulate prostate cancer (PCa) growth are poorly understood. Here, we found that expression of Nephroblastoma Overexpressed (NOV/CCN3) is upregulated in PCa cells and correlated with M2 macrophage infiltration. RAW264.7 macrophage migration was induced by conditioned media (CM) from various PCa cells in proportion to the cellular level of CCN3 expression and was inhibited by an anti-CCN3 neutralizing antibody. CCN3 and PCaCM treatment skewed RAW264.7 cell differentiation from an M1 phenotype to an M2 phenotype. PCa-derived CCN3 induced focal adhesion kinase (FAK)/Akt/NF-κB signaling in RAW264.7 cells, which resulted in VEGF expression and subsequently increased tube formation in endothelial progenitor cells. Finally, PCa-secreted CCN3 stimulated RAW264.7 cells and promoted angiogenesis in the chick chorioallantoic membrane assay (CAM), and increased tumor growth and tumor-associated angiogenesis in a PCa xenograft mouse model. Our results indicate that PCa-secreted CCN3 can recruit macrophages and skew their differentiation to an M2 phenotype. In turn, CCN3-stimulated macrophages contribute to VEGF-dependent angiogenesis. This study reveals a novel mechanism by which TAMs enhance PCa angiogenesis and identifies a potential therapeutic target for PCa.     

唑来膦酸通过NF-κB信号通路调控肺癌细胞的增殖和耐药

目的:探究唑来膦酸对肿瘤相关巨噬细胞（TAMs）表型转化和HGF表达的作用及对肺癌细胞增殖和耐药的影响。方法:通过Transwell系统将M2巨噬细胞与小鼠肺癌细胞Lewis共培养,得到M2型TAM(M2-TAMs)。采用不同浓度唑来膦酸作用于M2-TAMs,采用ELISA和RT-PCR检测M1型标记（IL-1β、TNFα、IL-6和iNOS）、M2型标记（HGF、EGF、IL-10和Arg1）的表达改变,采用Western blot检测NF-κB的表达。建立Transwell M2-TAMs-Lewis共培养模型,采用MTT方法检测肿瘤细胞的增殖和对吉非替尼耐药的影响;采用NF-κB特异性抑制剂PDCT作用唑来膦酸处理的TAMs,进一步检测TAMs M1/M2表型改变。结果:随着唑来膦酸浓度的增加,TAMs M1表型显著增强,M2表型逐渐减弱;与对照组相比,唑来膦酸处理的TAMs显著抑制了肺癌细胞的增殖,增强了其对吉非替尼的敏感性。在NF-κB特异性抑制剂（PDTC）的作用下,唑来膦酸处理的TAMs M1表型减弱,而M2表型增强。结论:唑来膦酸通过活化NF-κB信号通路促进肿瘤相关巨噬细胞M1表型转化并抑制肺癌细胞的增殖和耐药。     

Role of tumor-associated macrophages in common digestive system malignant tumors

Many digestive system malignant tumors are characterized by high incidence and mortality rate. Increasing evidence has revealed that the tumor microenvironment(TME) is involved in cancer initiation and tumor progression. Tumor-associated macrophages(TAMs) are a predominant constituent of the TME, and participate in the regulation of various biological behaviors and influence the prognosis of digestive system cancer. TAMs can be mainly classified into the antitumor M1 phenotype and protumor M2 ph...     

Effect of a selective cyclooxygenase-2 inhibitor, nimesulide, on the growth of lung tumors and their expression of cyclooxygenase-2 and peroxisome proliferator- activated receptor-gamma.

PURPOSE: The objectives of this study were to evaluate the effect of a cyclooxygenase (COX)-2 inhibitor, nimesulide, on the growth inhibition of s.c. human lung A549 adenocarcinoma tumors and to assess the effect of nimesulide on the expression of COX-2 and peroxisome proliferator-activated receptor (PPAR)-gamma in lung tumors harvested from mice. EXPERIMENTAL DESIGN: Female nu/nu mice were xenografted with s.c. A549 lung tumors, and 1 day after tumor implantation, the mice were fed with a diet containing nimesulide at 250-1500 ppm doses. Tumor dimensions were monitored twice weekly, and tumor samples isolated from mice were used to determine prostaglandin E(2) (PGE(2)) levels by enzyme immunoassay, expression of COX-2 and PPAR-gamma by Western blotting and immunohistochemistry. Furthermore, the induction of apoptosis in tumor specimens was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling staining. RESULTS: Nimesulide treatment showed a dose-dependent growth-inhibitory effect of A549 tumors with a maximum of 77.7% inhibition at 1500 ppm of nimesulide. Western blotting experiments showed similar expression of COX-2 in both control and nimesulide (250-1500 ppm)-treated mice tumor tissues. PPAR-gamma was found to be overexpressed as a result of 1500 ppm nimesulide treatment and was not detected in tumors from control or 250-1000 ppm nimesulide-treated mice. Nimesulide (1500 ppm) significantly reduced intratumor PGE(2) levels (P < 0.001) and induced apoptosis in 25% of tumor cells as compared with control tumors. CONCLUSIONS: Nimesulide (1500 ppm) induced growth inhibition of A549 lung tumors is associated with the reduction of intratumor PGE(2) levels but without affecting the expression of COX-2. Nimesulide-induced enhancement of the expression of PPAR-gamma may also contribute to its antitumor effect, which needs to be further investigated.     

Crosstalk between colon cancer cells and macrophages via inflammatory mediators and CD47 promotes tumour cell migration

Tumour-associated macrophages (TAMs) of the M2 phenotype are present in the stroma of many tumours and are frequently associated with the progression of several types of cancer. We investigated the role of M2 macrophages in colon cancer progression and found that human colon cancer tissue had elevated numbers of CD68⁺ (macrophage marker) cells and CD206⁺ (M2 macrophage marker) cells and increased CD47 expression. To explore potential interplay between colon cancer cells and M2 macrophages, we differentiated the monocyte cell line THP-1 into M1 and M2 macrophages (CD206^high and Th2 cytokine-secreting cells), respectively. M2 macrophages migrated faster than M1 macrophages towards SW480-conditioned medium. Similarly, M2 macrophage-conditioned medium induced SW480 cell migration and CD47 expression. Factors released by macrophages were involved in this induction. In addition, SW480 cells migrated faster when co-cultured with M2 macrophages. Inhibition of CD47 with blocking antibodies or siRNA significantly reduced the migration of SW480 cells in the presence of M2 macrophages. This effect was further decreased via blocking antibodies against the CD47 ligand signal-regulatory protein α (SIRPα). Additionally, cancer cells also secreted significant levels of IL-10, thereby promoting M2 macrophage differentiation. These findings indicate that a TAM-enriched tumour microenvironment promotes colon cancer cell migration and metastasis.     

Matrine suppresses lung cancer metastasis via targeting M2-like tumour-associated-macrophages polarization

Metastasis is the primary cause of death in lung cancer, one of the most prevalent and deadly neoplasms. The tumour-associated macrophages (TAMs) are crucial mediators to induce epithelial-mesenchymal transition (EMT) and promote lung metastasis via release of the cytokines. Matrine, a naturally occurring alkaloid, has been found with a variety of pharmacological effects, such as anti-cancer. In this study, an in vitro co-culture cell systems and a Lewis-bearing mouse model were employed to assay the potential effects of matrine on macrophages polarization, and its regulatory effects on EMT of Lewis lung cancer cells (LLCs). Our results clearly demonstrated that matrine inhibited M2-like RAW264.7 polarization, reducing the production of anti-inflammatory cytokines (IL-4, IL-10, and Arg-1), and M2 surface markers (CD206) were induced by LLCs via mTOR/PI3k/Akt signaling pathway, while it had no significant effect on M1 macrophages polarization. In vitro assays suggested that matrine partially blocked the metastasis of LLCs, and inhibited EMT induced by M2-like macrophages, which was evidenced by up-regulating the expression of E-cadherin and down-regulating the expression of N-cadherin, vimentin, and Snail. In vivo studies revealed that matrine decreased the ratio of CD206⁺/F4/80⁺, promoted the expression of CD4⁺ and CD8⁺ T cells, and inhibited the expression of Th2 in tumor and spleen tissues. Cell co-culture experiments revealed that Matrine promoted T-cell proliferation, which was impaired by tumour-derived CD11b⁺ myeloid cells. Collectively, our findings suggest that suppression of M2-like macrophages polarization of TAMs is a potential mechanism underlying the anti-metastasis effects of matrine in lung cancer.     

Clinical significance of macrophage heterogeneity in human malignant tumors

The fact that various immune cells, including macrophages, can be found in tumor tissue has long been known. With the recent introduction of the novel concept of macrophage differentiation into a classically activated phenotype (M1) and an alternatively activated phenotype (M2), the role of tumor‐associated macrophages (TAMs) is gradually beginning to be elucidated. Specifically, in human malignant tumors, TAMs that have differentiated into M2 macrophages act as “protumoral macrophages” and contribute to the progression of disease. Based on recent basic and preclinical research, TAMs that have differentiated into protumoral or M2 macrophages are believed to be intimately involved in the angiogenesis, immunosuppression, and activation of tumor cells. In this paper, we specifically discuss both the role of TAMs in human malignant tumors and the cell–cell interactions between TAMs and tumor cells.     

SLC3A2 promotes tumor-associated macrophage polarization through metabolic reprogramming in lung cancer

Tumor-associated macrophages (TAMs) are one of the most abundant immunosuppressive cells in the tumor microenvironment and possess crucial functions in facilitating tumor progression. Emerging evidence indicates that altered metabolic properties in cancer cells support the tumorigenic functions of TAMs. However, the mechanisms and mediators the underly the cross-talk between cancer cells and TAMs remain largely unknown. In the present study, we revealed that high solute carrier family 3 member 2 (SLC3A2) expression in lung cancer patients was associated with TAMs and poor prognosis. Knockdown of SLC3A2 in lung adenocarcinoma cells impaired M2 polarization of macrophages in a coculture system. Using metabolome analysis, we identified that SLC3A2 knockdown altered the metabolism of lung cancer cells and changed multiple metabolites, including arachidonic acid, in the tumor microenvironment. More importantly, we showed that arachidonic acid was responsible for SLC3A2-mediated macrophage polarization in the tumor microenvironment to differentiate into M2 type both in vitro and in vivo. Our data illustrate previously undescribed mechanisms responsible for TAM polarization and suggest that SLC3A2 acts as a metabolic switch on lung adenocarcinoma cells to induce macrophage phenotypic reprogramming through arachidonic acid.     

肿瘤相关巨噬细胞的极化方式及其对乳腺癌进展的影响

乳腺癌是严重威胁女性健康的恶性肿瘤之一，在全球范围内，其发病率呈逐年升高以及年轻化的趋势。肿瘤相关巨噬细胞（tumor-associated macrophages,TAMs）是乳腺癌肿瘤微环境中重要的免疫细胞，功能多样，具有高度的可塑性。当前的研究认为，TAMs在乳腺癌形成早期常表现为M1样表型，而在乳腺癌进展的过程中则极化为M2样表型，M2型TAMs能够促进乳腺癌的细胞增殖、血管生成、免疫抑制以及耐药性，与乳腺癌的预后呈负相关。因此，对TAMs极化方向的干预可作为乳腺癌抗癌治疗的一个新的研究方向。本文主要对乳腺癌中TAMs极化的分子机制以及对乳腺癌进展的影响进行综述。