Recruitment Of Myeloid-derived Suppressor Cells Research Articles

DNA methyltransferase inhibition promotes recruitment of myeloid-derived suppressor cells to the tumor microenvironment through induction of tumor cell-intrinsic interleukin-1

DNA methyltransferase (DNMT) inhibitors are used for treatment of certain hematological malignancies and exert anti-cancer activity through diverse mechanisms, including reexpression of tumor suppressor genes and anti-viral responses triggered by expression of endogenous retroviruses. Despite advances in the pharmacokinetic properties of DNMT inhibitors, the efficacy of these drugs in solid cancers remains low. Here, we show in cell lines and clinical and experimental tumors across multiple cancer types that DNMT inhibition induces the expression of interleukin-1 (IL-1), a cytokine with proinflammatory and protumorigenic properties. Specifically, this tumor-intrinsic IL-1 expression modulates the chemokine landscape of tumors and leads to the recruitment of monocytic myeloid-derived suppressor cells to the tumor microenvironment, processes that can be blocked by IL-1 antagonists. Molecular analysis demonstrates complex patterns of IL-1 and interferon activation and crosstalk in response to DNMT inhibition, which depend on the integrity of IRF- and NF-κB-mediated antiviral pathways and may determine the outcome of DNMT-inhibitor treatment. Together, our results show that DNMT inhibitors may negatively affect the microenvironment of a large subset of tumors and suggest that co-treatment with IL-1 antagonists may be a favorable combination for these patients.

Neddylation pathway promotes myeloid-derived suppressor cell infiltration via NF-κB-mCXCL5 signaling in lung cancer

Myeloid-derived suppressor cells (MDSCs), a population derived from immature myeloid progenitors, are present in the tumors of patients and highly protumorigenic. However, the molecular mechanisms regulating MDSC infiltration remain unclear. Neddylation pathway is overactivated in multiple cancers and has a significant role in tumor progression. We established a subcutaneous transplantation model of Lewis lung cancer in mice and showed that inactivation of neddylation pathway inhibits MDSC infiltration and impairs lung cancer growth. A high expression level of neuronal precursor cell-expressed developmentally downregulated protein 8 (NEDD8) is positively correlated with MDSC infiltration in human lung adenocarcinomas (LUADs). Moreover, inactivation of neddylation pathway inhibits the expression of murine CXCL5 (mCXCL5; human homolog CXCL6, hCXCL6), an important cytokine implicated in MDSC recruitment. Mechanistically, inactivation of neddylation pathway inhibits activity of Cullin-RING ligase 1, a typical neddylation substrate, and induces accumulation of phosphorylated IκBα and subsequent blockage of NF-κB translocation, thus suppressing transcriptional activation of mCxcl5 or hCXCL6. Collectively, our data suggest that neddylation-NF-κB-mCXCL5 axis is involved in MDSC recruitment to the tumor sites and demonstrate that neddylation pathway is a good therapeutic target for patients with LUAD, particularly those receiving anti-MDSC therapy.

Targeting FAPα-expressing hepatic stellate cells overcomes resistance to antiangiogenics in colorectal cancer liver metastasis models.

Vessel co-option has been demonstrated to mediate colorectal cancer liver metastasis (CRCLM) resistance to antiangiogenic therapy. The current mechanisms underlying vessel co-option have mainly focused on “hijacker” tumor cells, whereas the function of the “hijackee” sinusoidal blood vessels has not been explored. Here, we found that the occurrence of vessel co-option in bevacizumab-resistant CRCLM xenografts was associated with increased expression of fibroblast activation protein α (FAPα) in the co-opted hepatic stellate cells (HSCs), which was dramatically attenuated in HSC-specific conditional Fap-knockout mice bearing CRCLM allografts. Mechanistically, bevacizumab treatment induced hypoxia to upregulate the expression of fibroblast growth factor–binding protein 1 (FGFBP1) in tumor cells. Gain- or loss-of-function experiments revealed that the bevacizumab-resistant tumor cell–derived FGFBP1 induced FAPα expression by enhancing the paracrine FGF2/FGFR1/ERK1/-2/EGR1 signaling pathway in HSCs. FAPα promoted CXCL5 secretion in HSCs, which activated CXCR2 to promote the epithelial-mesenchymal transition of tumor cells and the recruitment of myeloid-derived suppressor cells. These findings were further validated in tumor tissues derived from patients with CRCLM. Targeting FAPα+ HSCs effectively disrupted the co-opted sinusoidal blood vessels and overcame bevacizumab resistance. Our study highlights the role of FAPα+ HSCs in vessel co-option and provides an effective strategy to overcome the vessel co-option–mediated bevacizumab resistance.

Chemotherapy-induced complement signaling modulates immunosuppression and metastatic relapse in breast cancer

Mortality from breast cancer is almost exclusively a result of tumor metastasis and resistance to therapy and therefore understanding the underlying mechanisms is an urgent challenge. Chemotherapy, routinely used to treat breast cancer, induces extensive tissue damage, eliciting an inflammatory response that may hinder efficacy and promote metastatic relapse. Here we show that systemic treatment with doxorubicin, but not cisplatin, following resection of a triple-negative breast tumor induces the expression of complement factors in lung fibroblasts and modulates an immunosuppressive metastatic niche that supports lung metastasis. Complement signaling derived from cancer-associated fibroblasts (CAFs) mediates the recruitment of myeloid-derived suppressor cells (MDSCs) to the metastatic niche, thus promoting T cell dysfunction. Pharmacological targeting of complement signaling in combination with chemotherapy alleviates immune dysregulation and attenuates lung metastasis. Our findings suggest that combining cytotoxic treatment with blockade of complement signaling in triple-negative breast cancer patients may attenuate the adverse effects of chemotherapy, thus offering a promising approach for clinical use.

Postoperative Plasmacytoid Dendritic Cells Secrete IFNα to Promote Recruitment of Myeloid-Derived Suppressor Cells and Drive Hepatocellular Carcinoma Recurrence.

IFNα secreted by plasmacytoid dendritic cells drives postoperative immunosuppression and early recurrence of hepatocellular carcinoma, providing new biomarkers and therapeutic targets to improve patient outcomes after surgical resection.

The Sympathetic Nervous System Contributes to the Establishment of Pre-Metastatic Pulmonary Microenvironments.

Emerging evidence suggests that neural activity contributes to tumor initiation and its acquisition of metastatic properties. More specifically, it has been reported that the sympathetic nervous system regulates tumor angiogenesis, tumor growth, and metastasis. The function of the sympathetic nervous system in primary tumors has been gradually elucidated. However, its functions in pre-metastatic environments and/or the preparation of metastatic environments far from the primary sites are still unknown. To investigate the role of the sympathetic nervous system in pre-metastatic environments, we performed chemical sympathectomy using 6-OHDA in mice and observed a decrease in lung metastasis by attenuating the recruitment of myeloid-derived suppressor cells. Furthermore, we note that neuro-immune cell interactions could be observed in tumor-bearing mouse lungs in conjunction with the decreased expression of Sema3A. These data indicate that the sympathetic nervous system contributes to the preparation of pre-metastatic microenvironments in the lungs, which are mediated by neuro-immune cell interactions.

Th17, Th22, and Myeloid-Derived Suppressor Cell Population Dynamics and Response to IL-6 in 4T1 Mammary Carcinoma.

Immunotherapies relying on type 1 immunity have shown robust clinical responses in some cancers yet remain relatively ineffective in solid breast tumors. Polarization toward type 2 immunity and expansion of myeloid-derived suppressor cells (MDSC) confer resistance to therapy, though it remains unclear whether polarization toward type 3 immunity occurs or has a similar effect. Therefore, we investigated the involvement of type 3 Th17 and Th22 cells and their association with expanding MDSC populations in the 4T1 mouse mammary carcinoma model. Th17 and Th22 were detected in the earliest measurable mass at d 14 and remained present until the final sampling on d 28. In peripheral organs, Th17 populations were significantly higher than the non-tumor bearing control and peaked early at d 7, before a palpable tumor had formed. Peripheral Th22 proportions were also significantly increased, though at later times when tumors were established. To further address the mechanism underlying type 3 immune cell and MDSC recruitment, we used CRISPR-Cas9 to knock out 4T1 tumor production of interleukin-6 (4T1-IL-6-KO), which functions in myelopoiesis, MDSC recruitment, and Th maturation. While 4T1-IL-6-KO tumor growth was similar to the control, the reduced IL-6 significantly expanded the total CD4+ Th population and Th17 in tumors, while Th22 and MDSC were reduced in all tissues; this suggests that clinical IL-6 depletion combined with immunotherapy could improve outcomes. In sum, 4T1 mammary carcinomas secrete IL-6 and other factors, to polarize and reshape Th populations and expand distinct Th17 and Th22 populations, which may facilitate tumor growth and confer immunotherapy resistance.

Pharmacological modulation of myeloid-derived suppressor cells to dampen inflammation.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population with potent suppressive and regulative properties. MDSCs’ strong immunosuppressive potential creates new possibilities to treat chronic inflammation and autoimmune diseases or induce tolerance towards transplantation. Here, we summarize and critically discuss different pharmacological approaches which modulate the generation, activation, and recruitment of MDSCs in vitro and in vivo, and their potential role in future immunosuppressive therapy.

Genetically engineered exosomes for targetedly preventing premetastatic niche formation and suppressing postoperative melanoma lung metastasis

Premetastatic niche (PMN) is a prerequisite for initiation of tumor metastasis. Targeting prevention of PMN formation in distant organs is becoming a promising strategy to suppress metastasis of primary tumor. Based on “organotropic metastasis”, melanoma tends to metastasize to lungs, where granulocytic myeloid-derived suppressor cells (G-MDSCs) recruitment in lungs significantly contributes to the PMN formation. Herein, functional exosomes (GExoI) were designed to present pulmonary targeting peptide GFE1 on the membrane and load PI3Kγ inhibitor (IPI549) inside, aiming at suppressing postoperative lung metastasis of melanoma. In postoperative mice model, intravenously injected GExoI could significantly accumulate in lungs and release IPI549 to block G-MDSCs recruitment through interfering with CXCLs/CXCR2/PI3Kγ signaling. The increased percentages of CD4+ T cells and CD8+ T cells in lungs could transform microenvironment from immunosuppression to immunostimulation, leading to metastasis inhibition. This study suggests an effective anti-metastasis strategy of targeting prevention of PMN formation through specifically blocking G-MDSCs recruitment.

B7H3-dependent myeloid-derived suppressor cell recruitment and activation in pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease without effective curative therapy. Recent evidence shows increased circulating myeloid-derived suppressor cells (MDSCs) in cancer, inflammation, and fibrosis, with some of these cells expressing B7H3. We sought to investigate the role of MDSCs in IPF and its potential mediation via B7H3. Here we prospectively collected peripheral blood samples from IPF patients to analyze for circulating MDSCs and B7H3 expression to assess their clinical significance and potential impact on co-cultured lung fibroblasts and T-cell activation. In parallel, we assess MDSC recruitment and potential B7H3 dependence in a mouse model of pulmonary fibrosis. Expansion of MDSCs in IPF patients correlated with disease severity. Co-culture of soluble B7H3 (sB7H3)-treated mouse monocytic MDSCs (M-MDSCs), but not granulocytic MDSCs (G-MDSCs), activated lung fibroblasts and myofibroblast differentiation. Additionally, sB7H3 significantly enhanced MDSC suppression of T-cell proliferation. Activated M-MDSCs displayed elevated TGFβ and Arg1 expression relative to that in G-MDSCs. Treatment with anti-B7H3 antibodies inhibited bone marrow-derived MDSC recruitment into the bleomycin-injured lung, accompanied by reduced expression of inflammation and fibrosis markers. Selective telomerase reverse transcriptase (TERT) deficiency in myeloid cells also diminished MDSC recruitment associated with the reduced plasma level of sB7H3, lung recruitment of c-Kit+ hematopoietic progenitors, myofibroblast differentiation, and fibrosis. Lung single-cell RNA sequencing (scRNA-seq) revealed fibroblasts as a predominant potential source of sB7H3, and indeed the conditioned medium from activated mouse lung fibroblasts had a chemotactic effect on bone marrow (BM)-MDSC, which was abolished by B7H3 blocking antibody. Thus, in addition to their immunosuppressive activity, TERT and B7H3-dependent MDSC expansion/recruitment from BM could play a paracrine role to activate myofibroblast differentiation during pulmonary fibrosis with potential significance for disease progression mediated by sB7H3.

CD147 mediates epidermal malignant transformation through the RSK2/AP-1 pathway

BackgroundMalignant transformation of the epidermis is an essential process in the pathogenesis of cutaneous squamous-cell carcinoma (cSCC). Although evidence has demonstrated that CD147 plays key roles in various tumors, the role of CD147 in epidermal malignant transformation in vivo remains unclear.MethodsEpidermal CD147-overexpression or knockout (EpiCD147-OE or EpiCD147-KO) transgenic mouse models were generated for in vivo study. RNA-sequencing and q-PCR were performed to identify the differentially expressed genes. Immunohistochemistry and flow cytometry were performed to investigate the role of CD147 in regulating myeloid-derived suppressor cells (MDSCs). Immunoprecipitation, EMSA and ChIP assays were performed to investigate the mechanism of CD147 in cell transformation.ResultsWe found that specific overexpression of CD147 in the epidermis (EpiCD147-OE) induces spontaneous tumor formation; moreover, a set of chemokines and cytokines including CXCL1, which play essential function in MDSC recruitment, were significantly upregulated in EpiCD147-OE transgenic mice. As expected, overexpression of CD147 in the epidermis remarkably facilitated tumorigenesis by increasing the rate of tumor initiation and the number and size of tumors in the DMBA/TPA mouse model. Interestingly, the expression of CXCL1 and the infiltration of MDSCs were dramatically increased in EpiCD147-OE transgenic mice. Our findings also showed that knockdown of CD147 attenuated EGF-induced malignant transformation as well as CXCL1 expression in HaCaT cells. Consistently, CD147 was found overexpressed in cutaneous squamous cell carcinoma (cSCC), and positively related with the expression of CD33, a myeloid-associated marker. We further identified RSK2, a serine/threonine kinase, as an interacting partner of CD147 at the binding site of CD147D207-230. The interaction of CD147 and RSK2 activated RSK2, thus enhancing AP-1 transcriptional activation. Furthermore, EMSAs and ChIP assays showed that AP-1 could associate with the CXCL1 promoter. Importantly, RSK2 inhibitor suppressed the tumor growth in DMBA/TPA mouse model by inhibiting the recruitment of MDSCs.ConclusionOur findings demonstrate that CD147 exerts a key function in epidermal malignant transformation in vivo by activating keratinocytes and recruiting MDSCs via the RSK2/AP-1 pathway.

Ablation of NLRP3 inflammasome rewires MDSC function and promotes tumor regression.

Myeloid-derived suppressor cells (MDSCs) are myeloid precursors that exert potent immunosuppressive properties in cancer. Despite the extensive knowledge on mechanisms implicated in mobilization, recruitment, and function of MDSCs, their therapeutic targeting remains an unmet need in cancer immunotherapy, suggesting that unappreciated mechanisms of MDSC-mediated suppression exist. Herein, we demonstrate an important role of NLRP3 inflammasome in the functional properties of MDSCs in tumor-bearing hosts. Specifically, Nlrp3-deficient mice exhibited reduced tumor growth compared to wild-type animals and induction of robust anti-tumor immunity, accompanied by re-wiring of the MDSC compartment. Interestingly, both monocytic (M-MDSCs) and granulocytic (G-MDSCs) subsets from Nlrp3-/- mice displayed impaired suppressive activity and demonstrated significant transcriptomic alterations supporting the loss-of-function and associated with metabolic re-programming. Finally, therapeutic targeting of NLRP3 inhibited tumor development and re-programmed the MDSC compartment. These findings propose that targeting NLRP3 in MDSCs could overcome tumor-induced tolerance and may provide new checkpoints of cancer immunotherapy.

Inhibition of myeloid-derived suppressor cell arginase-1 production enhances T-cell-based immunotherapy against Cryptococcus neoformans infection

Cryptococcosis is a potentially lethal disease that is primarily caused by the fungus Cryptococcus neoformans, treatment options for cryptococcosis are limited. Here, we show glucuronoxylomannan, the major polysaccharide component of C. neoformans, induces the recruitment of neutrophilic myeloid-derived suppressor cells in mice and patients with cryptococcosis. Depletion of neutrophilic myeloid-derived suppressor cells enhances host defense against C. neoformans infection. We identify C-type lectin receptor-2d recognizes glucuronoxylomannan to potentiate the immunosuppressive activity of neutrophilic myeloid-derived suppressor cells by initiating p38-mediated production of the enzyme arginase-1, which inhibits T-cell mediated antifungal responses. Notably, pharmacological inhibition of arginase-1 expression by a specific inhibitor of p38, SB202190, or an orally available receptor tyrosine kinase inhibitor, vandetanib, significantly enhances T-cell mediated antifungal responses against cryptococcosis. These data reveal a crucial suppressive role of neutrophilic myeloid-derived suppressor cells during cryptococcosis and highlight a promising immunotherapeutic application by inhibiting arginase-1 production to combat infectious diseases.

Bv8 Blockade Sensitizes Anti-PD1 Therapy Resistant Tumors.

Myeloid-derived suppressor cells (MDSCs) are known to promote tumor growth in part by their immunosuppressive activities and their angiogenesis support. It has been shown that Bv8 blockade inhibits the recruitment of MDSCs to tumors, thereby delaying tumor relapse associated with resistance to antiangiogenic therapy. However, the impact of Bv8 blockade on tumors resistant to the new immunotherapy drugs based on the blockade of immune checkpoints has not been investigated. Here, we demonstrate that granulocytic-MDSCs (G-MDSCs) are enriched in anti-PD1 resistant tumors. Importantly, resistance to anti-PD1 monotherapy is reversed upon switching to a combined regimen comprised of anti-Bv8 and anti-PD1 antibodies. This effect is associated with a decreased level of G-MDSCs and enrichment of active cytotoxic T cells in tumors. The blockade of anti-Bv8 has shown efficacy also in hyperprogressive phenotype of anti-PD1-treated tumors. In vitro, anti-Bv8 antibodies directly inhibit MDSC-mediated immunosuppression, as evidenced by enhanced tumor cell killing activity of cytotoxic T cells. Lastly, we show that anti-Bv8-treated MDSCs secrete proteins associated with effector immune cell function and T cell activity. Overall, we demonstrate that Bv8 blockade inhibits the immunosuppressive function of MDSCs, thereby enhancing anti-tumor activity of cytotoxic T cells and sensitizing anti-PD1 resistant tumors. Our findings suggest that combining Bv8 blockade with anti-PD1 therapy can be used as a strategy for overcoming therapy resistance.

Single-cell transcriptomics reveals immune dysregulation mediated by IL-17A in initiation of chronic lung injuries upon real-ambient particulate matter exposure

BackgroundLong-term exposure to fine particulate matter (PM2.5) increases susceptibility to chronic respiratory diseases, including inflammation and interstitial fibrosis. However, the regulatory mechanisms by which the immune response mediates the initiation of pulmonary fibrosis has yet to be fully characterized. This study aimed to illustrate the interplay between different cell clusters and key pathways in triggering chronic lung injuries in mice following PM exposure.ResultsSix-week-old C57BL/6J male mice were exposed to PM or filtered air for 16 weeks in a real-ambient PM exposure system in Shijiazhuang, China. The transcriptional profiles of whole lung cells following sub-chronic PM exposure were characterized by analysis of single-cell transcriptomics. The IL-17A knockout (IL-17A−/−) mouse model was utilized to determine whether the IL-17 signaling pathway mediated immune dysregulation in PM-induced chronic lung injuries. After 16-week PM exposure, chronic lung injuries with excessive collagen deposition and increased fibroblasts, neutrophils, and monocytes were noted concurrent with a decreased number of major classes of immune cells. Single-cell analysis showed that activation of the IL-17 signaling pathway was involved in the progression of pulmonary fibrosis upon sub-chronic PM exposure. Depletion of IL-17A led to significant decline in chronic lung injuries, which was mainly triggered by reduced recruitment of myeloid-derived suppressor cells (MDSCs) and downregulation of TGF-β.ConclusionThese novel findings demonstrate that immunosuppression via the IL-17A pathway plays a critical role in the initiation of chronic lung injuries upon sub-chronic PM exposure.

IL-1R1 blockade attenuates liver injury through inhibiting the recruitment of myeloid-derived suppressor cells in sepsis

Myeloid-derived suppressor cells (MDSCs) mobilize and migrate from bone marrow to peripheral tissues or immune organs, which is associated with poor prognosis in sepsis. Intervention of MDSCs might be a potential target for the effective treatment of sepsis. In the present study, we demonstrated that IL-1R1 blockade with either recombinant human IL-1R antagonist Anakinra or IL-1R1 deficiency had a protective effect on the liver injury in septic mice. The possible mechanism was that Anakinra treatment and IL-1R1 knockout inhibited the migration of MDSCs to the liver in sepsis, thus attenuating the immune suppression of MDSCs on effector T cells characterized with the decrease in proportion of CD4+ and CD8+ T cells. Furthermore, the switch from pro-inflammatory M1 macrophage to anti-inflammatory M2 phenotype and the ability of bacterial clearance in the liver of septic mice were enhanced obviously by Anakinra and IL-1R1 deficiency, which contributes to the attenuated liver injury. Taken together, these findings provide new ideas for revealing the relationship between IL-1R1 and MDSCs in sepsis, thereby providing a potentially effective target for ameliorating septic liver injury.

Abstract 3508: Exosome-mediated delivery of antisense oligonucleotides targeting C/EBPβ reprograms tumor-associated macrophages and induces potent single agent anti-tumor activity

Abstract Background: Tumor-associated macrophages (TAMs) and myeloid derived suppressor cells (MDSCs) promote an immunosuppressive milieu by inhibiting T-cell activation and recruitment, leading to resistance to immune checkpoint therapies. Interleukin 10 (IL10) and prostaglandin E2 (PGE2) promote tumor initiation and spread, in part, through TAM polarization and MDSC recruitment. C/EBPβ is a critical transcription factor that regulates the immunosuppressive state of TAMs and MDSCs and is activated by IL10 and PGE2 signaling. We developed a proprietary engineered exosome loaded with antisense oligonucleotides (ASOs) targeting C/EBPβ (exoASO-C/EBPβ), that selectively delivers ASO to TAMs and MDSCs, thereby inhibiting C/EBPβ expression and inducing reprogramming from an immunosuppressive (M2) to a pro-inflammatory (M1) phenotype. Results: exoASO-C/EBPβ demonstrated dose-dependent target gene knockdown (KD) in primary human M2 macrophages in vitro with a 2-fold higher potency (IC50) compared to free ASO. C/EBPβ KD resulted in profound changes in gene expression and cytokine secretion profile consistent with reprogramming to a M1 phenotype. exoASO-C/EBPβ induced a significant induction of pro-inflammatory cytokines, in M2 macrophages generated with IL10 or PGE2, both of which show prominent activation of the C/EBPβ pathway. Biodistribution in tumor-bearing mice (IT and IV) demonstrate selective uptake by MDSCs and TAMs. Intra-tumoral (IT) administration of exoASO-C/EBPβ in CT26 tumors resulted in a significantly higher KD of C/EBPβ in tumor-associated CD11b+ cells, as compared to CD11b- cells. Additionally, exoASO-C/EBPβ induced changes in Nos2, CD206 and Csf1r mRNA expression in CD11b+ cells, demonstrating in vivo M2 to M1 reprogramming. Furthermore, IT microinjections of exoASO-C/EBPβ in YUMM1.7 tumor-bearing mice resulted in a significant induction of pro-inflammatory M1 markers TNFα and iNOS, in contrast, free C/EBPβ ASO showed limited increase in M1 markers. exoASO-C/EBPβ administered IT as a single agent demonstrated significant anti-tumor activity in multiple tumor models including: the CT26-colorectal cancer (60% complete responses (CRs)), MB49-bladder cancer (70% CRs) and B16F10-melanoma (30% CRs). Combination treatment with anti-PD1 in all these models further increased the anti-tumor efficacy. Finally, we used a myeloid cell specific C/EBPβ/PGE2/IL10 gene signature to identify cancer indications where exoASO-C/EBPβ therapy might have the most therapeutic significance. Conclusion: exoASO-C/EBPβ is a novel therapeutic candidate that selectively targets and attenuates a critical transcription factor in immunosuppressive myeloid cells, resulting in reprogramming of TAMs and potent anti-tumor activity across multiple TAM-rich mouse models as a monotherapy. Citation Format: Sushrut Kamerkar, Charan Leng, Olga Burenkova, SuChul Jang, Kelvin Zhang, Yanyan Liu, William Dahlberg, Kyriakos Economides, Timothy Soos, Dalia Burzyn, Sriram Sathyanarayanan. Exosome-mediated delivery of antisense oligonucleotides targeting C/EBPβ reprograms tumor-associated macrophages and induces potent single agent anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3508.

Abstract 1335: Ovarian cancer cell glucocorticoid receptor activity is associated with cytokine secretion promoting infiltration of immunosuppressive cells into the tumor microenvironment

Abstract Immunosuppressive cells abundantly infiltrate tumors during cancer progression. Notably, immunosuppressive myeloid-derived suppressor cells (MDSCs) have recently been identified as a heterogeneous cell population that expand during tumor-associated inflammation and are significantly increased in the tumor, peripheral blood, as well as ascites of ovarian cancer patients. MDSCs contribute to tumor immune tolerance via inhibition of T-cell proliferation and activation. Signals from the tumor microenvironment in the form of soluble cytokines are proposed to lead to MDSC infiltration. It is also known that high tumor cell glucocorticoid receptor (GR) expression is associated with a relatively poor prognosis in ovarian cancer patients. We hypothesized that ovarian cancer cell GR expression and activity may modulate tumor cell cytokine secretion thereby leading to increased MDSC generation and recruitment to the tumor, eventually creating an immunosuppressive environment. Our preliminary data confirm that GR activation in two high-grade ovarian cancer cell lines (HEYA8 and SKOV3) modulates the cytokine secretome. Our results demonstrate GR-mediated secretion of several pro-tumorigenic and immunosuppressive proteins including G-CSF, M-CSF, TGF-β, and MCP-1 in those ovarian cancer models. We also observed downregulation of potent cytotoxic T-cell activating cytokines required for anti-tumor T-cell function including IL-2, IFN-γ and MIP1 upon GR activation. Importantly, treatment of cells with a competitive GR antagonist reverses this immunosuppressive secretome effect. Furthermore, upon culturing healthy peripheral blood mononuclear cells (PBMCs) with tumor conditioned media from GR activated ovarian cancer cells, we show that secreted immunomodulatory factors have the capacity to promote differentiation of human MDSCs from PBMCs. The resulting MDSC population was characterized via expression of activation markers including Arginase-1, iNOS, VEGF and TGF-β. Most importantly, the suppressive function of these MDSCs is being evaluated by determining their inhibitory potential on cytotoxic T-cell proliferation and/or activation. Based on the insight provided by these data, we propose to determine whether ovarian tumor cell-intrinsic GR activation and resulting MDSC generation contributes to earlier relapse of GR-positive ovarian cancers, and eventually whether this mechanism may be targeted to improve patient outcomes in this subset of ovarian cancers. Citation Format: Manisha Taya, Janet Gonzalez, Lynda Bennett, Suzanne D. Conzen. Ovarian cancer cell glucocorticoid receptor activity is associated with cytokine secretion promoting infiltration of immunosuppressive cells into the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1335.

Madecassic acid alleviates colitis-associated colorectal cancer by blocking the recruitment of myeloid-derived suppressor cells via the inhibition of IL-17 expression in γδT17 cells

IntroductionMadecassic acid (MA), a triterpene compound isolated from Centella Asiatica herbs, has previously been shown to attenuate colitis induced by DSS in mice. In the present study, we address whether and how MA ameliorates colitis-associated colorectal cancer (CAC), which accounts for a considerable proportion of colorectal cancer. MethodsCAC was induced by AOM/DSS in mice, and MA was administered orally once a day. To identify the source cells of IL-17 and the target cells for MA reducing the expression of IL-17 in the colons of CAC mice, single-cell suspensions were prepared from the colons of CAC mice and analyzed by flow cytometry. An adoptive transfer experiment was performed to verify the importance of the decreasing γδT17 cell population in the anti-CAC effect of MA. ResultsOral administration of MA reduced the burden and incidence of tumors in the CAC mice. MA decreased the number of MDSCs in the colon tissues of CAC mice and ameliorated anti-tumor immune responses. MA could prevent the migration of MDSCs by inhibiting the activation of γδT17 cells and the expression of chemokines. The population of activated-γδT17 cells in the tumor microenvironment of CAC mice positively correlated with the number of MDSCs and tumors as well as tumor load. Moreover, the anti-CAC effect of MA was significantly counteracted by the adoptive transfer of γδT17 cells. ConclusionsMA alleviates CAC by blocking the recruitment of MDSCs to increase the population of anti-tumor immune cells in tumor microenvironment via inhibition of the activation of γδT17 cells.

Role of vitamin D3 in tumor aggressiveness and radiation response for hepatocellular carcinoma.

Locoregional control is a significant prognostic factor for hepatocellular carcinoma (HCC). Historically, the use of radiotherapy (RT) for HCC was limited owing to the low radiotolerance of the liver and the need for high RT doses for disease control. We aimed to examine if 1α,25-dihydroxyvitamin D3 (calcitriol) has a role in the tumor inhibition and the radiation response of HCC in vitro and in vivo, and explore the underlying mechanisms. The human and murine liver cancer cell lines were selected for cellular and animal experiments to investigate the changes in tumor characteristics and the radiation response after calcitriol supplementation. The effects induced by calcitriol supplementation on interleukin-6 (IL-6) signaling and the tumor immune microenvironment following RT were also examined. Our data revealed that calcitriol supplementation attenuated tumor aggressive behavior, decrease IL-6 expression, and augmented radiation-induced tumor inhibition. The biological changes following calcitriol treatment included suppressed epithelial-mesenchymal transition, attenuated cancer stem cell-like properties and increased radiation-induced reactive oxygen species and cell death in vitro. Regarding immune microenvironment, calcitriol attenuated the recruitment of myeloid-derived suppressor cell (MDSC) recruitment and increased the infiltration of cytotoxic T cells in tumor following RT. Furthermore, When the primary liver tumor was irradiated with larger dose per fraction, calcitriol induced a smaller size of synchronous unirradiated tumor in mice, which linked with attenuated IL-6 signaling and MDSC recruitment. In conclusion, calcitriol treatment reduced tumor aggressiveness and enhanced the radiation response. The inhibited IL-6 signaling and subsequently enhanced antitumor immunity might be responsible to augment radiation-induced tumoricidal effect induced by calcitriol. Based on our results, we suggest that calcitriol could exert the antitumor and radiosensitization effects for HCC, especially for multifocal tumors.