Tumor-associated Macrophages In Tumors Research Articles

Lenvatinib‐resistant hepatocellular carcinoma promotes malignant potential of tumor‐associated macrophages via exosomal miR‐301a‐3p

AbstractBackgroundThe interactions between cancer cells and tumor‐associated macrophages (TAMs) via microRNAs (miRNAs) play crucial roles in malignant potential and drug resistance. However, it remains unclear how lenvatinib‐resistant hepatocellular carcinoma (LR HCC) promotes TAM tumor biology. Here we investigated the crosstalk between LR HCC cells and TAMs for cancer progression and lenvatinib resistance, focusing on an exosomal miRNA.MethodsWe used two bioinformatics software programs to identify miRNAs that target PTEN in gastrointestinal cancers, then investigated exosomal miRNA expression in LR HCC conditioned medium (CM). After modifying TAMs with LR HCC CM (LR TAM), macrophage phenotype and PTEN‐Nrf2 signaling pathway component expression were analyzed in LR TAMs. The malignant potential and drug resistance were investigated in naïve HCC cells cultured with LR TAM CM.ResultsLR HCC cells highly induced M2‐like properties in macrophages compared with naïve HCC cells. Exosomal miR‐301a‐3p expression was increased in LR HCC CM, with higher activation of the PTEN/PI3K/GSK3β/Nrf2 signaling pathway in LR TAMs. Naïve HCC cells were educated with LR TAM CM to promote malignant potential and lenvatinib resistance. Inhibition of exosomal miR‐301a‐3p prevented the malignant potential of LR TAMs. Activation of Nrf2 signaling by LR HCC cell‐derived exosomal miR‐301a‐3p skewed the transformation of macrophages to the M2 phenotype.ConclusionOur study provides new findings on the role of miR‐301a‐3p, suggesting it is a promising therapeutic target to improve HCC lenvatinib resistance.

Abstract LB077: CSF-1R inhibition with Pimicotinib (ABSK021) enhanced anti-tumor efficacy of KRASG12C inhibitors in preclinical non-small cell lung cancer mouse models

Abstract Background: KRAS mutations are highly prevalent oncogenic drivers in human cancers and KRASG12C is the most frequent mutations found in KRAS-mutant non-small lung cancer (NSCLC). It is reported that tumor associated macrophages (TAMs) are enriched in KRAS-driven transgenic lung cancer models. Depletion of macrophage results in a significant decrease in tumor burden and increased survival. Sotorasib (AMG510), the first KRASG12C inhibitor approved by FDA, has been found to modulate tumor immunity, impacting the recruitment of macrophages. CSF-1R signaling is critical for macrophage proliferation and survival. CSF-1R inhibition depletes TAMs and reprograms tumor microenvironment (TME), resulting in enhancement of anti-tumor immunity. Therefore, the combination of KRASG12C and CSF-1R inhibitors may synergize to enhance anti-tumor efficacy. Pimicotinib (ABSK021) is a potential best-in-class small molecule inhibitor of CSF-1R in clinical development of multiple indications. Here, we conducted in vivo experiments to explore the combined effects of KRASG12C and CSF-1R inhibitors. Methods: In vivo efficacy studies were performed to evaluate the combined treatment of KRASG12C inhibitors (AMG510 and ABSK071, a next-generation inhibitor targeting KRASG12C with better inhibitory activity) and CSF-1R inhibitor (ABSK021) in NCI-H2122 PBMC humanized mice and LLC syngeneic mice. RNA sequencing was employed to investigate the mechanism of action underlying the synergistic anti-tumor effect. Immunohistochemistry (IHC) was utilized to examine the changes of immune cell populations in TME. Results: The combinatory regimen of ABSK021 and KRASG12C inhibitors showed improved anti-tumor effects than each single agent alone in both mouse NSCLC models. Bioinformatics and follow-up analysis revealed a reduction in immune suppressive TAMs in tumors treated with ABSK021 alone or in combination with KRASG12C inhibitors. Furthermore, modulation of TME related to anti-tumor immunity, such as activated CD4 T, CD8 T and NK cells, was increased, and pro-tumor immunity, such as MDSC, regulatory T cells, was decreased in combination group. IHC results confirmed that ABSK021 addition led to macrophage depletion and more CD8 T cell infiltration in TME. Conclusions: For the first time, we demonstrate that the combined inhibition of KRASG12C and CSF-1R leads to superior therapeutic efficacy in preclinical NSCLC mouse models. This results suggests a potential novel therapeutic regimen that could yield improved clinical benefit to patients. Citation Format: Nannan Zhang, Bin Shen, Shenyan Liu, Cheng Dai, Haiyan Ying, Fushen Guo, Zhixuan Zhu, Wan Shi, Min Tu, Jie Wang, Jie Zhang, Manqi Liu, Qi Zhang, Zhui Chen. CSF-1R inhibition with Pimicotinib (ABSK021) enhanced anti-tumor efficacy of KRASG12C inhibitors in preclinical non-small cell lung cancer mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB077.

Abstract 3654: Olaparib combined with entinostat exerts differential effects on tumor-associated macrophages in tumors compared to ascites in syngeneic HR-proficient murine models of ovarian cancer

Abstract Poly ADP ribose inhibitors (PARPi) are most effective in ovarian cancer tumors with homologous recombination (HR) deficiency. Our group has shown that histone deacetylase inhibitors (HDACi) sensitize HR proficient ovarian cancer cells to PARPi. Our current efforts are directed towards understanding how this therapeutic regimen alters tumor-associated macrophages (TAMs) in murine models of high grade serous ovarian cancer. To investigate the effects of Ola combined with Ent, we used HR-proficient ID8 P53 wild-type and ID8 P53−/− syngeneic murine models. Mice were randomized into 4 groups: control, Ola, Ent and Ola+Ent. Mice (Ent and Ola+Ent) were pre-treated with 15 mg/kg entinostat or vehicle (Ola and Ola+Ent) for one week via oral gavage and then treated with vehicle/Ent/Ola (100 mg/kg)/Ola+Ent for two weeks. Mice were sacrificed 24 h after the last dose to harvest tumors and ascites. Tumors were processed for histology to determine cell proliferation (Ki67) and immune cell markers (CCL2, M1 and M2-like macrophages). Ascites fluid was processed for flow cytometric analysis of immune cells. Tumors from parental ID8 P53 wild type mice showed significantly lower cell proliferation marker Ki67 (P<0.05), higher anti-tumorigenic M1-like CCL2 (P<0.05), and lower pro-tumorigenic M2-like mannose receptor (P<0.05) in Ent and Ola+Ent groups compared to vehicle and Ola. Ascites showed no significant change in anti-tumorigenic M1-like macrophages, but significantly increased pro-tumorigenic M2-like macrophages (P<0.005). ID8 P53−/− mice tumors showed significantly lower Ki-67 (P<0.05) in Ola+Ent group compared to vehicle and mono-treatments. Ascites showed no significant change in total macrophage or pro-tumorigenic M2-like macrophages, but a significant decrease in anti-tumorigenic M1-like macrophages in Ent and Ola+Ent groups compared to vehicle. To summarize, in HR proficient ID8 P53 wildtype and ID8 P53−/− syngeneic mouse models, Ola and Ent treatment exerted anti-tumorigenic effects in tumors but potentially pro-tumorigenic effects in ascites. In conclusion, concomitant targeting of tumor TAMs and ascites TAMs may be a therapeutic regimen to investigate in the future. Citation Format: Vijayalaxmi G. Gupta, Tyler Woodard, Simona Miceska, Bisiyao Fashemi, Sangappa Chadchan, Wendy Zhang, Katherine Roby, Andrew Wilson, Fiona Yull, Marta Crispens, Sumanta Naik, Asya Smimov, Christina Stallings, Dineo Khabele. Olaparib combined with entinostat exerts differential effects on tumor-associated macrophages in tumors compared to ascites in syngeneic HR-proficient murine models of ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3654.

Crosstalk among long non-coding RNA, tumor-associated macrophages and small extracellular vesicles in tumorigenesis and dissemination.

Long noncoding RNAs (lncRNAs), which lack protein-coding ability, can regulate cancer cell growth, proliferation, invasion, and metastasis. Tumor-associated macrophages (TAMs) are key components of the tumor microenvironment that have a significant impact on cancer progression. Small extracellular vesicles (sEV) are crucial mediators of intercellular communications. Cancer cell and macrophage-derived sEV can carry lncRNAs that influence the onset and progression of cancer. Dysregulation of lncRNAs, TAMs, and sEV is widely observed in tumors which makes them valuable targets for cancer immunotherapy. In this review, we summarize current updates on the interactions among sEV, lncRNAs, and TAMs in tumors and provide new perspectives on cancer diagnosis and treatment.

The Role of TAMs in Tumor Microenvironment and New Research Progress.

Tumor-associated macrophages (TAMs) are an important part of tumor microenvironment (TME) and play a key role in TME, participating in the process of tumor occurrence, growth, invasion, and metastasis. Among them, metastasis to tumor tissue is the key step of malignant development of tumor. In this paper, the latest progress in the role of TAMs in the formation of tumor microenvironment is summarized. It is particularly noteworthy that cell and animal experiments show that TAMs can provide a favorable microenvironment for the occurrence and development of tumors. At the same time, clinical pathological experiments show that the accumulation of TAMs in tumor is related to poor clinical efficacy. Finally, this paper discusses the feasibility of TAMs-targeted therapy as a new indirect cancer therapy. This paper provides a theoretical basis for finding a potentially effective macrophage-targeted tumor therapy.

Abstract P053: Ablation of CCR1 relieves immunosuppression in pancreatic cancer

Abstract Pancreatic Cancer is one of the deadliest malignancies, with 5-year survival rate of 10%. The tumor microenvironment of pancreatic ductal adenocarcinoma (PDA) includes abundant fibroblasts and infiltrating immune cells, the latter largely immunosuppressive. Mono-immunotherapy or combination immunotherapy approaches has been ineffective in pancreatic cancer, pointing to the need for additional avenues to target in pancreatic cancer microenvironment. We previously showed that targeting regulatory T cell (Treg), a prevalent T cell population in pancreatic cancer, failed to relieve immunosuppression and led to accelerated tumor progression. We discovered that Treg depletion reprogrammed tumor associated fibroblasts and increased immunosuppressive myeloid cell recruitment, an effect that was partially mediated by CCLs/CCR1signaling. We found that tumor educated macrophages express the highest levels of Ccr1 compared to non-activated (M0), pro-inflammatory (M1), or anti-inflammatory (M2) bone marrow derived macrophage subsets. Thus, we sought to investigate the functional role of CCR1 in pancreatic cancer. By single cell RNA sequencing, we found CCR1 to be mainly expressed by tumor associated macrophages (TAMs) and neutrophils (or granulocytes) in both human and mouse PDA. We then orthotopically transplanted syngeneic mouse pancreatic cancer cells in CCR1 knockout hosts and observed reduced tumor growth which was rescued by CD8 T cell depletion. Histological analysis showed elevated Granzyme B expression in infiltrating T cells, as well as an increase in apoptotic cells in tumors implanted in Ccr1−/− mice. Through cytometry by time of flight (CyTOF) and co-immunofluorescence we also discovered that TAMs in tumors implanted in Ccr1−/− mice expressed less Arginase 1 and CD206 -both markers of immunosuppressive macrophages- compared to TAMs in wild type tumors. Thus, our data is consistent with the notion that tumor associated macrophages lacking CCR1 expression are less immunosuppressive, consequently allowing increased CD8 T cell-mediated anti-tumor immunity. We are currently exploring combination approaches targeting CCR1 in pancreatic cancer. Citation Format: Yaqing Zhang, Kristee L. Brown, Wei Yan, Zeribe C. Nwosu, Eileen K. Carpenter, Katelyn L. Donahue, Ashley Velez-Delgado, Sion Yang, Marina Pasca di Magliano. Ablation of CCR1 relieves immunosuppression in pancreatic cancer [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P053.

Abstract PO-129: Targeting CCR1 reprograms tumor associated macrophages in pancreatic cancer

Abstract The tumor microenvironment of pancreatic ductal adenocarcinoma (PDA) includes abundant fibroblasts and infiltrating immune cells, the latter largely immunosuppressive. We previously showed that targeting regulatory T cell (Treg), a prevalent T cell population in pancreatic cancer, failed to relieve immunosuppression and led to accelerated tumor progression. We discovered that Treg depletion reprogrammed tumor associated fibroblasts and increased immunosuppressive myeloid cell recruitment, an effect that was partially mediated by CCLs/CCR1signaling. Thus, we sought to investigate the potential therapeutic effect of targeting CCR1 in pancreatic cancer. By single cell RNA sequencing, we found CCR1 to be mainly expressed by tumor associated macrophages (TAMs) and neutrophils (or granulocytes) in both human and mouse PDA. We then orthotopically transplanted syngeneic mouse pancreatic cancer cells in CCR1 knockout hosts, and observed reduced tumor growth which was rescued by CD8 T cell depletion. Histological analysis showed elevated Granzyme B expression in infiltrating T cells, as well as an increase in cleaved caspase 3 positive cancer cells in tumors implanted in Ccr1−/− mice. Through cytometry by time of flight (CyTOF) and co-immunofluorescence we also discovered that TAMs in tumors implanted in Ccr1−/− mice expressed less Arginase 1 and CD206 -both markers of immunosuppressive macrophages- compared to TAMs in wild type tumors. Thus, our data is consistent with the notion that tumor associated macrophages lacking CCR1 expression are less immunosuppressive, consequently allowing increased CD8 T cell-mediated anti-tumor immunity. We are currently exploring combination approaches targeting CCR1 in pancreatic cancer. Citation Format: Yaqing Zhang, Kristee L. Brown, Wei Yan, Zeribe C. Nwosu, Eileen K. Carpenter, Katelyn L. Donahue, Ashley Velez-Delgado, Sion Yang, Marina Pasca di Magliano. Targeting CCR1 reprograms tumor associated macrophages in pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-129.

M2 macrophage-targeted iron oxide nanoparticles for magnetic resonance image-guided magnetic hyperthermia therapy

Tumor-associated macrophages (TAMs) play an important role in tumor development and progression. In particular, M2 TAMs can promote tumor growth by facilitating tumor progression and malignant behaviors. Selectively targeted elimination of M2 TAMs to inhibit tumor progression is of great significance for cancer treatment. Iron oxide nanoparticles based magnetic hyperthermia therapy (MHT) is a classical approach to destroy tumor tissue with deep penetration depth. In this study, we developed a typical M2 macrophage-targeted peptide (M2pep) functionalized superparamagnetic iron oxide nanoparticle (SPIO) for magnetic resonance imaging (MRI)-guided MHT in an orthotopic breast cancer mouse model. The obtained multifunctional SPIO-M2pep with a hydrodynamic diameter of 20 nm showed efficient targeting capability, high transverse relaxivity (149 mM−1 s−1) and satisfactory magnetic hyperthermia performance in vitro. In vivo studies demonstrated that the SPIO-M2pep based MRI can monitor the distribution of nanoparticles in tumor and indicate the suitable timing for MHT. The M2 macrophage-targeted MHT significantly reduced the tumor volume and the population of pro-tumoral M2 TAMs in tumor. In addition, the SPIO-M2pep based MHT can remodel the tumor immune microenvironment (TIME). The multifunctional SPIO-M2pep with M2 macrophage-targeting ability, high magnetic hyperthermia efficiency, MR imaging capability and effective role in remodeling the TIME hold great potential to improve clinical cancer therapy outcomes.

CD163 as a Biomarker in Colorectal Cancer: The Expression on Circulating Monocytes and Tumor-Associated Macrophages, and the Soluble Form in the Blood.

The macrophage-associated molecule CD163 has been reported as a prognostic biomarker in different cancer types, but its role in colorectal cancer (CRC) is unclear. We studied CD163 in the tumor microenvironment and circulation of patients with CRC in relation to clinicopathological parameters. An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum sCD163 levels and multiparameter flow cytometry was used to study the peripheral blood monocytes and their CD163 expression in CRC patients (N = 78) and healthy donors (N = 50). The distribution of tumor-associated macrophages (TAMs) was studied in primary colorectal tumors with multiplex immunofluorescence. We showed that CRC patients with above-median sCD163 level had a shorter overall survival (OS, p = 0.035) as well as disease-free survival (DFS, p = 0.005). The above-median sCD163 remained significantly associated with a shorter DFS in the multivariate analysis (p = 0.049). Moreover, a shorter OS was observed in CRC patients with an above-median total monocyte percentage (p = 0.007). The number and phenotype of the stromal and intraepithelial TAMs in colorectal tumors were not associated with clinical outcome. In conclusion, sCD163 and monocytes in the circulation may be potential prognostic biomarkers in CRC patients, whereas TAMs in the tumor showed no association with clinical outcome. Thus, our results emphasize the importance of the innate systemic immune response in CRC disease progression.

Redirecting Immune Activation in the Tumor Microenvironment of Estrogen Receptor Negative Breast Cancer

Abstract The tumor microenvironment (TME) is an essential contributor to the development and progression of malignancy. Within the TME, tumor associated macrophages (TAMs) mediate angiogenesis, metastasis, and immune suppression, which inhibits infiltration of tumor-specific cytotoxic CD8+ T cells. In previous work, we demonstrated that the synthetic triterpenoid CDDO-methyl ester (CDDO-Me) converts breast TAMs from tumor-promoting to tumor-inhibiting in vitro. We show now for the first time that CDDO-Me remodels the breast TME, redirecting TAM activation and T cell tumor infiltration in vivo. We demonstrate that CDDO-Me significantly attenuates IL-10 and VEGF expression but stimulates TNF production, and reduces surface expression of CD206 and CD115, markers of immunosuppressive TAMs. CDDO-Me treatment redirects the TAM transcriptional profile, inducing signaling pathways associated with immune stimulation, and inhibits TAM tumor infiltration, consistent with decreased expression of CCL2. In CDDO-Me-treated mice, both the absolute number and proportion of CD4+ T cells were reduced, while the proportion of CD8+ T cells was significantly increased in tumors and spleen. Moreover, mice fed CDDO-Me demonstrated significant reductions in numbers of tumor CD4+Foxp3+ regulatory T cells. These results demonstrate for the first time that CDDO-Me relieves immunosuppression in the breast TME and unleashes host adaptive anti-tumor immunity.

CDDO-Me Alters the Tumor Microenvironment in Estrogen Receptor Negative Breast Cancer

The tumor microenvironment (TME) is an essential contributor to the development and progression of malignancy. Within the TME, tumor associated macrophages (TAMs) mediate angiogenesis, metastasis, and immunosuppression, which inhibits infiltration of tumor-specific cytotoxic CD8+ T cells. In previous work, we demonstrated that the synthetic triterpenoid CDDO-methyl ester (CDDO-Me) converts breast TAMs from a tumor-promoting to a tumor-inhibiting activation state in vitro. We show now that CDDO-Me remodels the breast TME, redirecting TAM activation and T cell tumor infiltration in vivo. We demonstrate that CDDO-Me significantly attenuates IL-10 and VEGF expression but stimulates TNF production, and reduces surface expression of CD206 and CD115, markers of immunosuppressive TAMs. CDDO-Me treatment redirects the TAM transcriptional profile, inducing signaling pathways associated with immune stimulation, and inhibits TAM tumor infiltration, consistent with decreased expression of CCL2. In CDDO-Me-treated mice, both the absolute number and proportion of splenic CD4+ T cells were reduced, while the proportion of CD8+ T cells was significantly increased in both tumors and spleen. Moreover, mice fed CDDO-Me demonstrated significant reductions in numbers of CD4+ Foxp3+ regulatory T cells within tumors. These results demonstrate for the first time that CDDO-Me relieves immunosuppression in the breast TME and unleashes host adaptive anti-tumor immunity.

Enhancement of antitumor effect of radiotherapy via combination with Au@SiO2 nanoparticles targeted to tumor-associated macrophages

Tumor-associated macrophages (TAMs) exhibit the M2 phenotype and serve as critical tumor-promoting immune cells in the tumor microenvironment. As TAMs are an important target, we examined the effect of gold nanoparticles (AuNPs) with radiotherapy (RT) on M2 TAMs in tumors. We synthesized CD163 antibody-conjugated, silica-coated AuNPs (CD163-GNPs) that were specifically recognized by M2 TAMs. Bone marrow-derived macrophages and Raw 264.7 macrophages were polarized into M1 and M2 phenotypes. The effect of CD163-GNPs combined with RT was evaluated in a CT26 syngeneic mouse model (BALB/c mice). Immunostaining, flow cytometry, microscopic analyses, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction (qRT-PCR), and tumor growth delay assay were performed following irradiation combined with CD163-GNP treatment. We observed selective phagocytosis of CD163-GNPs by Raw 264.7 macrophages following M1/M2 polarization. Immunostaining analyses revealed higher numbers of CD163-GNPs taken up by M2 macrophages than M0 or M1 type. CD163-GNPs combined with RT significantly reduced tumor growth in the CT26 syngeneic mouse model. Macrophages subjected to the combination treatment showed increased expression of M1 markers. The depletion of M2 TAMs in tumors upon combination treatment with CD163-GNPs enhances the efficiency of RT.

Abstract 4491: Association of intratumoral immunologic profile with overall survival in metastatic pancreatic cancer patients treated with combination immunotherapy with or without PD-1 blockade

Abstract Background: Metastatic pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis with a 5-year survival rate of 8%. Single-agent immunotherapies fail to show clinical activity due to a complex tumor microenvironment (TME) and lack of effector T cells. We previously showed in a neoadjuvant clinical trial that an irradiated, granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic PDAC vaccine (GVAX) recruited T cells into tumor and upregulated the PD-1/PD-L1 pathway1. Here we describe the first clinical testing of GVAX prime given with attenuated listeria monocytogenes expressing mesothelin (CRS-207) boost alone or in combination with nivolumab to block PD-1 signaling in metastatic PDAC patients, and evaluated changes in the TME. Experimental Design: 22 metastatic PDAC biopsy pairs were obtained at baseline and after 2 GVAX prime and 1 CRS-207 boost from 96 vaccinated patients. Nivolumab was administered with each vaccine in patients randomized to vaccine + nivolumab arm. Biopsies containing >30% tumor cellularity were chosen for multiplex immunohistochemistry (IHC) to examine changes in immune cell subtypes and their signaling pathways in tumors. We did a comparative analysis looking at lymphoid and myeloid complexity, immune function, and PD-L1 status of patients with overall survival (OS) <150 days [short OS, n=6], 150-300 days [middle OS, n=11], and >300 days [long OS, n=5] or by treatment arm. Results: Favorable OS correlated with low CD68+ myeloid cell and high lymphoid cell numbers, which was detected after prime-boost. Evaluation of the functional status of CD8+ T cells after prime-boost of patients with long OS revealed a 10.2% increase in EOMES+PD1- effector memory and 1.4% decrease in EOMES+PD1+ exhausted T cells. At baseline, fewer CSF1R+ tumor associated macrophages (TAMs), CD68+CD163+ and CD163- myeloid cells in tumors was associated with long OS. We analyzed nivolumab’s effect on the TME and found that tumors from nivolumab-treated patients displayed a decrease in CD68+ myeloid cells after prime-boost compared to baseline. Interestingly, CD163+ TAMs in tumors of nivolumab-treated patients expressed higher PD-L1 levels. Conclusion: This study suggests that induction of lymphoid-inflamed expression profiles with less exhausted and more effector memory CD8+ T cells during treatment is associated with long OS independent of nivolumab treatment. Fewer TAMs in pre-treatment biopsies and a low myeloid: lymphoid cell ratio in post-immunotherapy tumor samples may be predictive of improved survival. Our findings also suggest that nivolumab induces PD-L1 expression on myeloid cells. Continual identification of key tissue-based biomarkers that correlate with OS may be useful for predicting therapeutic response. 1) Lutz E. (2014) Cancer Immunol Res. Jul;2(7):616-31. Citation Format: Annie A. Wu, Takahiro Tsujikawa, Gina Choe, Teresa Beechwood, Lisa M. Coussens, Jennifer N. Durham, Elizabeth M. Jaffee, Dung T. Le. Association of intratumoral immunologic profile with overall survival in metastatic pancreatic cancer patients treated with combination immunotherapy with or without PD-1 blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4491.

Abstract 4081: Efficacy of MERTK inhibitor in combination with pembrolizumab in lung cancer

Abstract Introduction: MERTK is thought to play a role in cancer immune evasion mechanism based on M2 type macrophage-driven immunosuppression in tumor microenvironment (TME). Thus, MERTK is a highly promising target for anti-cancer therapy under high tumor associated macrophages (TAMs) condition. We evaluated the anti-tumor effects and immune reaction of combination or single MERTK inhibitor in two lung squamous patients derived xenograft (PDX) tumor engrafted Hu-CD34-NSG models. Methods: The aPD-1 sensitive (YHIM2004) and aPD-1 non-sensitive (YHIM2009) squamous cell carcinoma PDX models were selected from pre-test with pembrolizumab. The selected two models were composed four groups; control, pembrolizumab, MERTK inhibitor, and combination. We applied pembrolizumab as aPD-1 blockade (10 mpk, q2w, i.p. inj.). The dose of MERTK inhibitor was 50 mpk, q1d by orally. The treatment was started when tumor size reached 100 mm3. Whole exome sequencing (WES), microarray (mRNA), flow cytometry, and multispectral image analysis were performed on the tumors. To elucidate the involvement of MERTK inhibitor in tumor, the tumor mutation burden, tumor microenvironment and immune cell phenotype were deconvoluted. Results: The TMB of YHIM2004 and YHIM2009 was 3.23 and 2.64 (mutations/Mb) respectively. The PD-L1 and TIL level of YHIM2004 were relatively higher than YHIM2009. Both two models were observed high macrophage in tumor. The two PDX-models, YHIM2004 (aPD-1 sensitive), YHIM2009 (aPD-1 non-sensitive) were observed anti-tumor effects in MERTK inhibitor single treatment groups (TGI = 44.23%, 67.40% respectively, p < 0.05, t-test). Especially, YHIM2004 tumor was reduced after combination therapy more than single treatment. Of note, the NOG-PDX model demonstrated no anti-tumor effect in MERTK inhibitor monotherapy, suggesting that this drug involves anti-cancer immune responses. Flow cytometry data showed increased PD-1+ and granzyme B+ T cells (p <0.05, t-test) in the combined group (YHIM2004) and MERTK inhibitor monotherapy group (YHIM2009) as much as the tumor suppressive effect. Conclusion: We concluded that MERTK signaling involves regulation of anti-cancer immune responses. Our results suggest an anti-cancer therapeutics of MERTK selective inhibitor on aPD-1 sensitive or non-sensitive tumors under high TAM tumor microenvironment. Citation Format: Kyoung-Ho Pyo, Ha-Ni Cho, Chun-Feng Xin, Jae Seok Cho, Han Na Kang, Jiyeon Yun, Hye Ryun Kim, Byoung Chul Cho. Efficacy of MERTK inhibitor in combination with pembrolizumab in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4081.

Abstract 137: Pharmacologic activation of integrin CD11b as a novel therapeutic strategy against lung cancer

Abstract Lung cancer is the leading cause of cancer related deaths in the United States. With a 5-year survival rate of 18%, lung cancer patients are in immediate need of new therapeutic options. A major problem facing immunotherapy for cancer is the active immune suppression by the tumor. Tumors show presence of large numbers of tumor associated macrophages (TAMs), which suppress the adaptive immune response, increase neo-vascularization to the tumor, and promote tumor survival. Integrin CD11b is highly expressed on TAMs and is essential for their recruitment and biological functions. Reasoning that CD11b activity is important for controlling tumor growth, we developed a novel small molecule agonist called leuhadherin-1 (LA1), which activates CD11b. We found that CD11b activation by LA1 significantly reduced tumor growth in wild type mice bearing Lewis Lung Carcinoma (LLC) tumors as early as one week post treatment. Conversely, LLC tumors grew at a faster rate in CD11b-/- mice, compared to wild type mice, showing that CD11b is important for controlling tumor growth. Importantly, LA1 treatment in tumor bearing CD11b-/- mice did not show any efficacy, demonstrating the specificity of LA1 to CD11b. These data suggest that CD11b activation via LA1 modulates TAMs in tumors and is a novel therapeutic strategy against cancer. Citation Format: Terese Geraghty, Anugraha Rajagopalan, Samia Khan, Judith Varner, Vineet Gupta. Pharmacologic activation of integrin CD11b as a novel therapeutic strategy against lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 137.

Tumor-Associated Macrophages: Therapeutic Targets for Skin Cancer.

Tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) are significant components of the microenvironment of solid tumors in the majority of cancers. TAMs sequentially develop from monocytes into functional macrophages. In each differentiation stage, TAMs obtain various immunosuppressive functions to maintain the tumor microenvironment (e.g., expression of immune checkpoint molecules, production of Treg-related chemokines and cytokines, production of arginase I). Although the main population of TAMs is immunosuppressive M2 macrophages, TAMs can be modulated into M1-type macrophages in each differential stage, leading to the suppression of tumor growth. Because the administration of certain drugs or stromal factors can stimulate TAMs to produce specific chemokines, leading to the recruitment of various tumor-infiltrating lymphocytes, TAMs can serve as targets for cancer immunotherapy. In this review, we discuss the differentiation, activation, and immunosuppressive function of TAMs, as well as their benefits in cancer immunotherapy.

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.

Inverse role of distinct subsets and distribution of macrophage in lung cancer prognosis: a meta-analysis.

BackgroundTumor-associated macrophages (TAMs) play a crucial role in the regulation of local inflammatory and immune response of tumor microenvironment, being associated with worse outcome of several solid tumors. But the prognostic value of tumor-infiltrating TAMs in lung cancer is still controversial.MethodsWe conduct a meta-analysis of 3055 patients in 21 studies searched from PubMed and Medline to investigate the correlation between tumor-infiltrating TAMs, including distinct TAM subsets and tissue distribution, and survival of lung cancer. Survival data were computed into odds ratios (ORs) and pooled using Mantel–Haenszel random-effect model. All statistical tests were two-sided.ResultsHigh density of tumor-infiltrating TAMs was significantly associated with worse overall survival (OS) at 3 years (OR = 2.45, 95% CI = 1.25 to 4.80, P = 0.009) and 5 years (OR = 2.04, 95% CI = 1.03 to 4.01, P = 0.04) of lung cancer. Results for disease free survival (DFS) were similar. M2 subset was associated with worse 3 year-OS and 5 year-OS, whereas M1 subset was associated with better 3-year OS and 5-year OS. Elevated TAM density in tumor stroma was associated with worse OS at 3 years and 5 years, while elevated TAMs in tumor islet/tumor stroma were associated with better OS at 3 years and 5 years.ConclusionsIncreased tumor-infiltrating TAMs are associated with poor prognosis of lung cancer. M2 subset and TAMs in tumor stroma were associated with worse survival, while M1 subset and TAMs in tumor islet were associated with favorable survival of lung cancer.

Enhanced tumor growth in the remaining lung after major lung resection

BackgroundPneumonectomy induces active growth of the remaining lung in order to compensate for lost lung tissue. We hypothesized that tumor progression is enhanced in the activated local environment. MethodsWe examined the effects of mechanical strain on the activation of lung growth and tumor progression in mice. The mechanical strain imposed on the right lung after left pneumonectomy was neutralized by filling the empty space that remained after pneumonectomy with a polypropylene prosthesis. ResultsThe neutralization of the strain prevented active lung growth. According to an angiogenesis array, stronger monocyte chemoattractant protein-1 (MCP-1) expression was found in the strain-induced growing lung. The neutralization of the strain attenuated the release of MCP-1 from the lung cells. The intravenous injection of Lewis lung cancer cells resulted in the enhanced development of metastatic foci in the strain-induced growing lung, but the enhanced development was canceled by the neutralization of the strain. An immunohistochemical analysis revealed the prominent accumulation of tumor-associated macrophages in tumors arising in the strain-induced growing lung, and that there was a relationship between the accumulation and the MCP-1 expression status. ConclusionsOur results suggested that mechanical lung strain, induced by pulmonary resection, triggers active lung growth, thereby creating a tumor-friendly environment. The modification of that environment, as well as the minimizing of surgical stress, may be a meaningful strategy to improve the therapeutic outcome after lung cancer surgery.

Abstract B64: CSF1R-dependent tumor-associated macrophages arise from bone marrow-derived monocytes and promote gastrointestinal stromal tumor development

Abstract Introduction: Gastrointestinal stromal tumors (GISTs) are densely infiltrated with tumor-associated macrophages (TAMs), which we have previously shown to exhibit an M1, inflammatory phenotype in established, untreated tumors in mice and humans. Since TAMs in most tumors are reported to be M2, we sought to determine the role of TAMs in early GIST development and the mechanism of TAM recruitment. Methods: Genetically engineered KitV558del/+ mice that develop GIST were treated as adults and from birth with PLX5622, a small molecule inhibitor of colony stimulating factor 1 receptor (CSF1R). Tumors were weighed and analyzed by flow cytometry, immunohistochemistry, and immunofluorescence. Adoptive transfer experiments utilized tail vein injection of freshly harvested CD45.1+, CFSE-labeled bone marrow cells 2 days following withdrawal of CSF1R inhibition. Cell proliferation was determined by Ki67 staining. Results: Tumors from KitV558del/+ mice treated with PLX5622 from birth for 4 weeks showed an 85% reduction of TAMs and a 40% decrease in size (n=8/group, p<0.05). TAMs from untreated 2 week old developing GIST mouse tumors tended to be more M2-like with 2.5x lower CD11c and 1.25x lower MHCII, while the M2 markers CD206 and MSR1 were increased 1.5x and 3x, respectively. Likewise, 3 days following withdrawal of PLX5622, newly recruited TAMs displayed a 20% reduction of MHCII+ cells (p<0.05). Furthermore, following PLX5622 withdrawal, flow cytometry revealed that TAM repopulation was preceded by an initial surge in Ly6Chi monocytes in the blood and the tumor. Subsequently, there was a reciprocal decrease of blood monocytes as the F4/80hi TAM population expanded to baseline levels of 35-40% of leukocytes over the course of 7 days. TAMs exhibited increased proliferation (55% Ki67+) compared to monocytes (17% Ki67+) and Kit+ tumor cells (2.5% Ki67+) 4 days after withdrawal of CSF1R inhibition. Following adoptive transfer of CD45.1+, CFSE-labeled bone marrow, the labeled cells showed an increasing TAM:monocyte ratio over time (2 on day 3, 7 on day 5, and 68 on day 10). Conclusion: Although TAMs infiltrating established GISTs in adult mice exhibit an M1-like, anti-tumor phenotype, newly recruited TAMs in tumor development or TAMs after CSF1R inhibition are relatively M2-like. Within the tumor, bone marrow-derived monocytes differentiate into CSF1R-dependent TAMs, which proliferate to fully repopulate the tumor. Citation Format: Michael J. Beckman, Michael Cavnar, Adrian Seifert, Juan Santamaria-Barria, Jennifer Zhang, Adam Levy, Ferdinand Rossi, Shan Zeng, Ronald P. DeMatteo. CSF1R-dependent tumor-associated macrophages arise from bone marrow-derived monocytes and promote gastrointestinal stromal tumor development. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B64.