Celastrol inhibits cancer metastasis by suppressing M2-like polarization of macrophages.

In recent years, a large amount of clinical and experimental data has shown that M2-like polarized tumor-associated macrophages (TAMs) play an important role in cancer metastasis. Therefore, TAMs, especially M2-like TAMs is a promising target for anti-tumor metastasis therapy. Here, we found that celastrol dose-dependently suppressed IL-13 induced CD206 expression both in RAW264.7 and in primary macrophages. Consistently, celastrol also inhibited the expression of M2-like specific genes, including MRC1, Arg1, Fizz1, Mgl2 and CD11c. Further, by the employment of 4T1 breast cancer model, we found that celastrol significantly prevented cancer metastasis in vivo. Mechanistically, celastrol completely ameliorated STAT6 phosphorylation, which is the key signal molecule responsible for M2 polarization. Our research puts forward a new application of celastrol in anti-cancer metastasis, by intervening M2-like polarization through inhibiting STAT6.

Imatinib prevents lung cancer metastasis by inhibiting M2-like polarization of macrophages.

Although M2-like tumor-associated macrophages (TAMs) have been considered as a vital therapeutic target in cancer therapy due to their role in promoting tumor progression and metastasis, very few compounds have been identified to inhibit M2-like polarization of TAMs. Here, we showed that Imatinib significantly prevented macrophage M2-like polarization induced by IL-13 or IL-4 in vitro, as illustrated by reduced expression of cell surface marker CD206 and M2-like genes, including Arg1, Mgl2, Mrc1, CDH1, and CCL2. Further, the migration of lung cancer cells promoted by the conditioned medium from M2-like macrophages could be restrained by Imatinib. Mechanistically, Imatinib inhibited STAT6 phosphorylation and nuclear translocation, resulting in the macrophage M2-like polarization arrest. Furthermore, Imatinib reduced the number of metastasis of Lewis lung cancer without affecting tumor growth. Both in tumor and lung tissues, the percentage of M2-like macrophages decreased after the administration of Imatinib for one week. Taken together, these data suggest that Imatinib is able to inhibit macrophage M2-like polarization, which plays a vital role in Imatinib suppressed metastasis of Lewis lung cancer.

Macrophage Polarization: Anti-Cancer Strategies to Target Tumor-Associated Macrophage in Breast Cancer.

Tumor-associated macrophages (TAMs) are the most abundant inflammatory cells and orchestrate different stages of breast cancer development. TAMs participate in the tumor angiogenesis, matrix remodeling, invasion, immunosuppression, metastasis, and chemoresistance in breast cancer. Several clinical studies indicate the association between the high influx of TAMs in tumor with poor prognosis in hepatocellular, ovarian, cervical, and breast cancer. Previously developed hypotheses have proposed that TAMs participate in antitumor responses of the body, while recently many clinical and experimental studies have revealed that TAMs in tumor microenvironment predominantly resemble with M2-like polarized macrophages and produce a high amount of anti-inflammatory factors which are directly responsible for the development of tumor. Various studies have shown that TAMs in tumor either enhance or antagonize the anti-tumor efficacy of cytotoxic agents, antibodies-targeting cancer cells, and therapeutic agents depending on the nature of treatment. Thereby, multiple roles of TAMs suggests that it is very important to develop novel therapeutic strategies to target TAMs in breast tumor. In this review, we have discussed the functional role of TAMs in breast cancer and summarized available recent advances potential therapeutic strategies that effectively target to TAMs cells. J. Cell. Biochem. 118: 2484-2501, 2017. © 2017 Wiley Periodicals, Inc.

Gefitinib inhibits M2-like polarization of tumor-associated macrophages in Lewis lung cancer by targeting the STAT6 signaling pathway.

M2-like polarized tumor-associated macrophages (TAMs) play a pivotal role in promoting cancer cell growth, invasion, metastasis and angiogenesis. The identification of M2-like TAMs during tumor progression is an attractive approach for cancer therapy. In this study, we investigated the relevance of macrophage polarization and the antitumor effect of gefitinib in Lewis Lung cancer (LLC) in vitro and in vivo. Gefitinib at a concentration below 2.5 µmol/L did not cause significant growth inhibition on LLC and RAW 264.7 cell lines and bone marrow-derived macrophage (BMDMs). However, a small concentration of gefitinib (0.62 µmol/L) significantly inhibited IL-13-induced M2-like polarization of macrophages, evidenced by the decreased expression of the M2 surface markers CD206 and CD163, down-regulation of specific M2-marker genes (Mrc1, Ym1, Fizz1, Arg1, IL-10 and CCL2) as well as inhibition of M2-like macrophage-mediated invasion and migration of LLC cells. In RAW 264.7 cells, gefitinib inhibits IL-13-induced phosphorylation of STAT6, which was a crucial signaling pathway in macrophage M2-like polarization. In LLC mice metastasis model, oral administration of gefitinib (75 mg·kg-1·d-1, for 21 d) significantly reduced the number of lung metastasis nodules, down-regulated the expression of M2 marker genes and the percentages CD206+ and CD68+ macrophages in tumor tissues. These results demonstrated that gefitinib effectively inhibits M2-like polarization both in vitro and in vivo, revealing a novel potential mechanism for the chemopreventative effect of gefitinib.

[Advances in study of macrophages in chemotherapy resistance of cancer].

As extremely important inflammatory cells in the tumor microenvironment, tumor-associated macrophages (TAMs) can secrete a variety of chemokines and cytokines, which play an important role in the occurrence of tumor growth and metastasis. Recent years, increasing studies have shown that macrophages are associated with tumor chemotherapy sensitivity. The chemical substances produced by macrophages affect the efficacy of chemotherapeutic agents. In addition, some chemotherapeutic agents have an effect on the recruitment and bioactivity of macrophages in the tumor issue, which influences the anti-tumor efficacy of chemotherapy drugs. In this review, we summarize the roles of macrophages in the chemotherapy resistance, including the regulatory mechanism and the strategy of targeting macrophages.

[Combination of lapatinib with chlorogenic acid inhibits breast cancer metastasis by suppressing macrophage M2 polarization].

OBJECTIVE: To determine the effect of the combination of lapatinib with chlorogenic acid on metastasis of breast cancer in mouse model. METHODS: The classical macrophage M2 polarization model induced by interlukin13in vitro was adopted in the study. Flow cytometric analysis was performed to detect the expression of M2 marker CD206. The transcription of M2-associated genes was measured by RT-PCR. HE staining was used to analyze the metastatic nodes of breast cancer in lungs of MMTV-PyVT mice. Immunostaining analysis was used to detect the expression of related proteins in breast cancer. RESULTS: The combination of lapatinib and chlorogenic acid inhibited the expression of CD206 induced by IL-13[(42.17%±2.59%) vs (61.15%±7.58%), P<0.05]. The combination more markedly suppressed expression of M2-associated gene Ym1 than lapatinib alone[(0.9±0.1) vs (1.8±0.0), P<0.05]. The combination of lapatinib and chlorogenic acid significantly reduced metastatic nodes in lung[P<0.05], and also significantly decreased the percentage of CD206(+) cells in breast cancer compared to controls[(6.08%±2.60%) vs(29.04%±5.86%), P<0.05]. CONCLUSION: The combination of lapatinib and chlorogenic acid can effectively inhibit macrophage M2 polarization and metastasis of breast cancer.

[Statins enhance anti-tumor effect of suberoylanilide hydroxamic acid on human non-small cell lung carcinoma cells].

OBJECTIVE: To evaluate the anti-tumor effect of the combination of suberoylanilide hydroxamic acid(SAHA) with statins(lovastatin or simvastatin) on non-small cell lung carcinoma(NSCLC) cells. METHODS: Human NSCLC A549 cells were treated with SAHA in combination of lovastatin or simvastatin. The cell growth was analyzed by SRB method, and the apoptosis of A549 cells was assessed by flow cytometer. The expression of cleaved poly-ADP-ribose polymerase(cleaved-PARP) and p21 protein was analyzed by Western-blotting when A549 cells were challenged with 2.5µmol/L SAHA and 5µmol/L lovastatin. RESULTS: Lovastatin and simvastatin synergized SAHA in the inhibition of A549 cells. SAHA induced apoptosis was also enhanced by lovastatin. Treatment with 2.5µmol/L SAHA significantly up-regulated the expression of p21 protein in 48 h, while the protein expression was reduced in combined treatment with 5µmol/L lovastatin. CONCLUSION: Statins can synergize the anti-tumor effect of SAHA in human NSCLC cells through a p21-dependent way.

PARP1 Suppresses the Transcription of PD-L1 by Poly(ADP-Ribosyl)ating STAT3.

Studies have pointed to a role of PARP1 in regulating gene expression through poly(ADP-ribosyl)ating, sequence-specific, DNA-binding transcription factors. However, few examples exist that link this role of PARP1 to the immunogenicity of cancer cells. Here, we report that PARP1 poly(ADP-ribosyl)ates STAT3 and subsequently promotes STAT3 dephosphorylation, resulting in reduced transcriptional activity of STAT3 and expression of PD-L1. In this study, we showed that PARP1 silencing or pharmacologic inhibition enhanced the transcription of PD-L1 in cancer cells, which was accompanied by the upregulation of PD-L1 protein expression, both in the cytoplasm and on the cell surface. This induction of PD-L1 was attenuated in the absence of the transcription factor STAT3. Cell-based studies indicated that PARP1 interacted directly with STAT3 and caused STAT3 poly(ADP-ribosyl)ation. STAT3's activation of PD-L1 transcription was abolished by the overexpression of wild-type PARP1 but not mutant PARP1, which lacks catalytic activity. PARP1 downregulation or catalytic inhibition enhanced the phosphorylation of STAT3, which was reversed by the ectopic expression of wild-type PARP1 but not by mutated PARP1. An inverse correlation between PARP1 and PD-L1 was also observed in clinical ovarian cancer samples. Overall, our study revealed PARP1-mediated poly(ADP-ribosyl)ation of STAT3 as a key step in inhibiting the transcription of PD-L1, and this mechanism exists in a variety of cancer cells.

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.

SAHA triggered MET activation contributes to SAHA tolerance in solid cancer cells.

Although SAHA is approved for the treatment of cutaneous T-cell lymphoma by the U.S. Food and Drug Administration, clinical trials using SAHA as a monotherapy or in combination with other chemotherapeutic agents in solid tumors have not met with success, and the mechanisms of tolerance remain unknown. In this study, using the prostate cancer cell line PC3 and the non-small lung cancer cell line A549, which have limited sensitivity to SAHA, we found that SAHA triggered MET and AKT phosphorylation at clinical concentrations. siRNA silencing of MET enhanced SAHA induced apoptosis in PC3 and A549 cells. However, MET protein expression and HGF secretion were not affected by SAHA, suggesting that the SAHA-induced MET activation was not due to MET over-expression or HGF paracrine secretion. However, mRNA and protein expression of the laminin receptor integrin α5ß1 was up-regulated by SAHA prior to MET activation. Silencing of integrin α5ß1 abolished SAHA-triggered MET phosphorylation, suggesting the involvement of integrin α5ß1 in MET activation. Further, the combination of SAHA and XL184 resulted in a synergistic induction of cancer cell apoptosis and a synergistic inhibition of tumor growth. These data indicate that SAHA triggered MET activation in an HGF independent manner. This effect is partially involved in the resistance to SAHA in solid cancers, warranting further clinical investigation into combining SAHA with MET inhibitors in solid cancer treatment.

Resistance of SMMC-7721 hepatoma cells to etoposide in hypoxia is reversed by VEGF inhibitor.

Hypoxia is associated with resistance to chemotherapy in a number of human cancer types; particularly in hepatocellular carcinoma (HCC), which is a highly vascularized tumor. To develop a potential combination therapy strategy that is capable of overcoming the hypoxia­induced insensitivity to chemotherapy, the HCC cell SMMC­7721 was employed to investigate the hypoxia­induced chemoresistance to etoposide. Increased levels of hypoxia­inducible factor­1α (HIF­1α) and vascular endothelial growth factor (VEGF) were observed when SMMC­7721 cells were exposed to hypoxia, and exposure of tumor cells to hypoxia impaired etoposide­induced DNA damage, as indicated by the failure of upregulation of γHA2X. Etoposide­induced apoptosis and cell cycle arrest of SMMC­7721 was also impaired in hypoxia. However, co­treatment with anti­VEGF significantly restored etoposide­induced cell apoptosis and cell cycle arrest, as indicated by the elimination of B­cell lymphoma 2 (Bcl­2), procaspase 3, cyclin B1 and Cdc2. Furthermore, anti­VEGF eliminated phosphorylation of AKT, ERK and IκB­α resulting from hypoxia, suggesting the involvement of VEGF in the activation of the survival pathways. In conclusion, the present study suggests a significant role of VEGF in the chemoresistance of etoposide in hypoxia. A rational chemotherapy should be developed based on a combination of etoposide and anti­VEGF.