Megan M. Kaneda

PI3Kγ is a molecular switch that controls immune suppression

Macrophages play critical, but opposite, roles in acute and chronic inflammation and cancer. In response to pathogens or injury, inflammatory macrophages express cytokines that stimulate cytotoxic T cells, whereas macrophages in neoplastic and parasitic diseases express anti-inflammatory cytokines that induce immune suppression and may promote resistance to T cell checkpoint inhibitors. Here we show that macrophage PI 3-kinase γ controls a critical switch between immune stimulation and suppression during inflammation and cancer. PI3Kγ signalling through Akt and mTor inhibits NFκB activation while stimulating C/EBPβ activation, thereby inducing a transcriptional program that promotes immune suppression during inflammation and tumour growth. By contrast, selective inactivation of macrophage PI3Kγ stimulates and prolongs NFκB activation and inhibits C/EBPβ activation, thus promoting an immunostimulatory transcriptional program that restores CD8+ T cell activation and cytotoxicity. PI3Kγ synergizes with checkpoint inhibitor therapy to promote tumour regression and increased survival in mouse models of cancer. In addition, PI3Kγ-directed, anti-inflammatory gene expression can predict survival probability in cancer patients. Our work thus demonstrates that therapeutic targeting of intracellular signalling pathways that regulate the switch between macrophage polarization states can control immune suppression in cancer and other disorders.

Bruton Tyrosine Kinase–Dependent Immune Cell Cross-talk Drives Pancreas Cancer

UNLABELLED Pancreas ductal adenocarcinoma (PDAC) has one of the worst 5-year survival rates of all solid tumors, and thus new treatment strategies are urgently needed. Here, we report that targeting Bruton tyrosine kinase (BTK), a key B-cell and macrophage kinase, restores T cell-dependent antitumor immune responses, thereby inhibiting PDAC growth and improving responsiveness to standard-of-care chemotherapy. We report that PDAC tumor growth depends on cross-talk between B cells and FcRγ(+) tumor-associated macrophages, resulting in T(H)2-type macrophage programming via BTK activation in a PI3Kγ-dependent manner. Treatment of PDAC-bearing mice with the BTK inhibitor PCI32765 (ibrutinib) or by PI3Kγ inhibition reprogrammed macrophages toward a T(H)1 phenotype that fostered CD8(+) T-cell cytotoxicity, and suppressed PDAC growth, indicating that BTK signaling mediates PDAC immunosuppression. These data indicate that pharmacologic inhibition of BTK in PDAC can reactivate adaptive immune responses, presenting a new therapeutic modality for this devastating tumor type. SIGNIFICANCE We report that BTK regulates B-cell and macrophage-mediated T-cell suppression in pancreas adenocarcinomas. Inhibition of BTK with the FDA-approved inhibitor ibrutinib restores T cell-dependent antitumor immune responses to inhibit PDAC growth and improves responsiveness to chemotherapy, presenting a new therapeutic modality for pancreas cancer.

Macrophage PI3Kγ Drives Pancreatic Ductal Adenocarcinoma Progression

UNLABELLED Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a low 5-year survival rate, yet new immunotherapeutic modalities may offer hope for this and other intractable cancers. Here, we report that inhibitory targeting of PI3Kγ, a key macrophage lipid kinase, stimulates antitumor immune responses, leading to improved survival and responsiveness to standard-of-care chemotherapy in animal models of PDAC. PI3Kγ selectively drives immunosuppressive transcriptional programming in macrophages that inhibits adaptive immune responses and promotes tumor cell invasion and desmoplasia in PDAC. Blockade of PI3Kγ in PDAC-bearing mice reprograms tumor-associated macrophages to stimulate CD8(+) T-cell-mediated tumor suppression and to inhibit tumor cell invasion, metastasis, and desmoplasia. These data indicate the central role that macrophage PI3Kγ plays in PDAC progression and demonstrate that pharmacologic inhibition of PI3Kγ represents a new therapeutic modality for this devastating tumor type. SIGNIFICANCE We report here that PI3Kγ regulates macrophage transcriptional programming, leading to T-cell suppression, desmoplasia, and metastasis in pancreas adenocarcinoma. Genetic or pharmacologic inhibition of PI3Kγ restores antitumor immune responses and improves responsiveness to standard-of-care chemotherapy. PI3Kγ represents a new therapeutic immune target for pancreas cancer. Cancer Discov; 6(8); 870-85. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 803.

Combination immunotherapy with TLR agonists and checkpoint inhibitors suppresses head and neck cancer

Checkpoint inhibitors have demonstrated efficacy in patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). However, the majority of patients do not benefit from these agents. To improve the efficacy of checkpoint inhibitors, intratumoral (i.t.) injection with innate immune activators, TLR7 and TLR9 agonists, were tested along with programmed death-1 receptor (PD-1) blockade. The combination therapy suppressed tumor growth at the primary injected and distant sites in human papillomavirus-negative (HPV-negative) SCC7 and MOC1, and HPV-positive MEER syngeneic mouse models. Abscopal effects and suppression of secondary challenged tumor suggest that local treatment with TLR agonists in combination with anti-PD-1 provided systemic adaptive immunity. I.t. treatment with a TLR7 agonist increased the ratio of M1 to M2 tumor-associated macrophages (TAMs) and promoted the infiltration of tumor-specific IFNγ-producing CD8+ T cells. Anti-PD-1 treatment increased T cell receptor (TCR) clonality of CD8+ T cells in tumors and spleens of treated mice. Collectively, these experiments demonstrate that combination therapy with i.t. delivery of TLR agonists and PD-1 blockade activates TAMs and induces tumor-specific adaptive immune responses, leading to suppression of primary tumor growth and prevention of metastasis in HNSCC models.

PI3Kgamma activates integrin alpha4 and promotes immune suppressive myeloid cell polarization during tumor progression.

Myeloid-derived suppressor cells and tumor-associated macrophages, aided by PI3Kγ and integrin α4, accumulate in tumors and block antitumor immune responses. Suppression of PI3Kγ or integrin α4 alleviated the block and supported antitumor immune responses. Immunosuppressive myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) accumulate in tumors where they inhibit T cell–mediated antitumor immune responses and promote tumor progression. Myeloid cell PI3Kγ plays a role in regulating tumor immune suppression by promoting integrin α4–dependent MDSC recruitment to tumors and by stimulating the immunosuppressive polarization of MDSCs and TAMs. Here, we show that integrin α4 promotes immunosuppressive polarization of MDSCs and TAMs downstream of PI3Kγ, thereby inhibiting antitumor immunity. Genetic or pharmacological suppression of either PI3Kγ or integrin α4 blocked MDSC recruitment to tumors and also inhibited immune suppressive myeloid cell polarization, thereby reducing expression of IL10 and increasing expression of IL12 and IFNγ within tumors. Inhibition of PI3Kγ or integrin α4 within tumors stimulated dendritic cell and CD8+ T-cell recruitment and maturation, as well as tumor cell cytotoxicity in vivo, thereby inhibiting tumor growth. As blockade of PI3Kγ or integrin α4 prevents accumulation of MDSC and reduces myeloid cell expression of immunosuppressive factors that stimulate tumor immune escape, these results highlight PI3Kγ and integrin α4 as targets for the design of cancer therapeutics. Cancer Immunol Res; 5(11); 957–68. ©2017 AACR.

Abstract LB-207: PI3Kγ inhibition suppresses glioblastoma tumorigenicity through disruption of an IL11-STAT3-MYC signaling axis between microglia and glioblastoma

While mutations in isocitrate dehydrogenase (IDH) gene are associated with favorable prognosis in glioblastoma patients, the biologic basis for favorable survival in patients with wild-type IDH (wtIDH) glioblastoma remains poorly understood. We identified an inflammatory gene signature whose expression inversely correlated with patient survival in three independent, wtIDH glioblastoma cohorts (The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA), and REMEBRANDT). Systematic analysis of the inflammatory infiltrates of the glioblastoma microenvironment revealed microglia as the predominant cell type driving this survival association. We show that the growth stimulatory effects of microglia can be recapitulated using conditioned media derived microglia. We cross-referenced proteomic profile of microglia conditioned media with the TCGA and the CGGA to identify constituent soluble factors with survival association and identified IL11. In both clinical datasets, increased IL11 expression was associated with shortened survival. Further, IL11 mRNA and protein expression are elevated in clinical glioblastoma specimen relative to the surrounding cerebrum. Analysis of samples secured from three unrelated patients revealed that IL11 level in microglia was significantly higher than in tumor cells. In vitro and in vivo experiments demonstrated that IL11 was necessary and sufficient for enhancement of glioblastoma tumorigenicity. IL11 induced activation of a STAT3-MYC signaling axis in tumor cells, which upregulates the genes required for glioblastoma tumorigenicity, including OLIG2, SOX2, and POU3F2. PI3Kγ activation in myeloid-derived cells, including microglia, is essential for its trafficking into the tumor microenvironment. We hypothesized that PI3Kγ inhibition or inactivation should impede microglia trafficking to the glioblastoma microenvironment and suppress tumorigenicity. Supporting our hypothesis, PI3Kγ inhibitor suppressed tumorigenicity in vivo by reducing microglia density and IL11 release in murine glioblastoma GL261 tumors. These effects were recapitulated when GL261 was implanted into PI3Kγ -/- mice. Importantly, ectopic expression IL11 reversed the tumor-suppressive effect of PI3Kγ inhibitor. The anti-glioblastoma effects of PI3Kγ inhibitor were enhanced by temozolomide, the standard of care chemotherapy for glioblastoma. These results suggest microglia is a mediator of clinical glioblastoma survival and disruption of microglia-glioblastoma interaction as potential therapeutic strategy. Citation Format: Jie Li, Megan M. Kaneda, Jiangfei Wang, Kunal Patel, Johnny Akers, Valya Ramakrishnan, Tao Jiang, Bob S. Carter, Judith A. Varner, Clark C. Chen. PI3Kγ inhibition suppresses glioblastoma tumorigenicity through disruption of an IL11-STAT3-MYC signaling axis between microglia and glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-207. doi:10.1158/1538-7445.AM2017-LB-207

Abstract 3966: Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages

Tumor associated macrophages are involved in regulation of cancer growth and aggressiveness. Whereas M1 macrophages trigger an inflammatory response and inhibit tumor growth, M2 macrophages secrete pro-tumor cytokines into the microenvironment to support tumor progression. A macrophage switch from M1 to M2 has been associated with lung cancer progression, and cancer stem cells have been implicated as a driver of this reprogramming. We recently reported that integrin αvβ3 expression is induced on lung adenocarcinoma cells during drug resistance and is both necessary and sufficient to reprogram these tumors to a stem-like state. Given the role that cancer stem cells play in switching M1 to M2 macrophages, we asked whether αvβ3 expression on lung adenocarcinoma cells account for this macrophage conversion. The M1/M2 macrophage ratio in αvβ3-positive tumors was markedly decreased relative to tumors lacking αvβ3. We next treated mice bearing αvβ3-positive tumors with a monoclonal antibody (LM609) targeting this receptor to assess its ability to alter the macrophage phenotype within these tumors. LM609 was able to selectively eliminate the αvβ3-positive cancer stem cells via antibody-dependent cell-mediated cytotoxicity (ADCC), and this not only increased the M1 macrophage population, but also markedly enhanced the sensitivity of these tumors to the effects of therapy. These findings reveal that αvβ3-expressing cancer stem cells favor the pro-tumor M2 macrophage phenotype. Eliminating αvβ3-positive cancer stem cells via ADCC serves to both increase pro-inflammatory macrophages within the tumor microenvironment and prolong tumor sensitivity to therapy. Citation Format: Hiromi I. Wettersten, Toshiyuki Minami, Megan M. Kaneda, Laetitia Seguin, Judith A. Varner, Sara M. Weis, David A. Cheresh. Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3966. doi:10.1158/1538-7445.AM2017-3966

Abstract 718: Macrophage PI3Kgamma signaling promotes cancer immune suppression

Innate immune cells can switch from a pro-inflammatory state that defends against pathogens and to an anti-inflammatory state that repairs damaged tissue. Pro-inflammatory myeloid cells activate cytotoxic T cells to eliminate pathogens, but anti-inflammatory myeloid cells inhibit T cell mediated immunity, stimulate angiogenesis, and stimulate fibrosis, all of which promote tumor progression. The predominant isoform of PI(3)Kinase in myeloid cells, PI3Kgamma, controls the switch between immune stimulation and immune suppression during inflammation and cancer. Myeloid cell PI3Kgamma and its effectors Akt1, mTor, and S6Kinase stimulate C/EBPbeta-dependent expression of immunosuppressive factors, including Arginase and TGFbeta, but suppress NFkappaB-dependent expression of pro-inflammatory cytokines such as IL12 and IFNgamma, thereby inducing tumor immune suppression and consequent tumor growth and metastasis. In contrast, inhibition of PI3Kgamma activity by genetic or pharmacological means suppresses C/EPBbeta-mediated transcription of anti-inflammatory factors and stimulates NFkappaB-mediated transcription of the pro-inflammatory cytokines IL12 and IFNgamma, thereby restoring CD8+ T cell-dependent cytotoxicity that inhibits tumor growth and metastasis. Therefore, inhibitory targeting of PI3Kgamma indirectly restores cytotoxic T cell immune responses that elicit tumor suppression without unwanted side effects. Our studies highlight the strong therapeutic potential of targeting this kinase to control inflammation and cancer. This work was supported by grants to JAV from the NIH (5R01CA126820), the Landon Foundation-AACR (12-60-27-VARN), the Lustgarten Foundation for Pancreatic Research and the Whitworth Foundation for Cancer Research. Citation Format: Megan M. Kaneda, Judith A. Varner. Macrophage PI3Kgamma signaling promotes cancer immune suppression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 718.

Abstract IA22: Innate immune cell PI3K gamma as a target for suppression of pancreatic ductal adenocarcinoma

Ductal adenocarcinoma of the pancreas (PDAC) is a devastating disease that will afflict greater than 40,000 Americans. Less than 5% of these new pancreatic cancer patients will survive 5 years following diagnosis. PDAC is rarely detected in the early stages, with more than 80% of patients presenting with locally unresectable or metastatic disease at the time of diagnosis. As this form of cancer is also resistant to current cytotoxic therapies and ionizing radiation, novel therapeutic and diagnostic approaches are desperately needed to improve patient outcome. A characteristic feature of PDAC is the presence of an abundant, inflammatory infiltrate. In response to tumor-derived chemoattractants, we found that myeloid cells invade tumors where they promote immunosuppression, resulting in tumor growth and metastasis. We discovered that myeloid cell PI3-kinase gamma (PI3Kgamma) controls tumor immunosuppression, as PI3Kgamma signaling inhibits pro-inflammatory gene expression responses in macrophages, monocytes and granulocytes and promotes anti-inflammatory responses. Suppression of PI3Kgamma in mutant mice and in mice treated with pharmacologic inhibitors of PI3Kgamma promotes CD8+ T cell anti-tumor immune responses, leading to a 50% reduction in tumor growth and metastasis in orthotopic mouse models of pancreatic carcinoma and significant extension of survival in GEM models of PDAC (PDX1-cre; LSL-KrasG12D/+; LSL-Trp53 R172H/+). Furthermore, PI3Kgamma inhibition blocks macrophage stimulation of collagen deposition by fibroblasts in PDAC. We are exploring the combination of PI3kinase gamma inhibition with tumor cell and T cell targeted therapeutics could significantly reduce tumor growth and metastasis of PDAC. These approaches could improve patient outcomes by reducing tumor progression and preserving organ function by inhibiting desmoplasia. Citation Format: Megan Kaneda, Chanae Hardamon, Michael C. Schmid, Michael Bouvet, Franco Novelli, Emilio Hirsch, Andrew Lowy, Judith A. Varner. Innate immune cell PI3K gamma as a target for suppression of pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr IA22.

Abstract 3650: PI3-kinase gamma controls the macrophage M1-M2 switch, thereby promoting tumor immunosuppression and progression

Innate immune cells (macrophages, monocytes and neutrophils) rapidly migrate to sites of tissue damage where they initially activate T cells (M1 classical response). These cells gradually transition to suppress T cell responses, while stimulating wound healing (M2 alternative response). In tumors, however, the normal immune response is chronically disrupted and an exaggerated immunosuppressive, wound healing, tumor-promoting (M2) response prevails. In order to identify the mechanisms regulating this M2 response in tumor inflammation and to develop novel therapeutics to control it, we set out to explore the role of macrophage signaling in control of the M1-M2 switch. Using RNA seq analysis of gene expression patterns in M1 and M2 macrophages in vitro and gene expression analysis of myeloid cells in spontaneous and orthotopic mouse models of lung, pancreatic and breast cancer, we found that myeloid cell PI3Kinase gamma controls the switch between the M1-M2 phenotype in human and murine macrophages. PI3Kinase gamma signaling stimulates an immunosuppressive, wound healing gene expression program exemplified by expression of immunosuppressive and pro-angiogenic factors, such as Arginase1, TGFbeta1, PDGFBB, MMP9, and MMP13, and suppression of pro-inflammatory factors such as IL12, iNos, and interferon gamma. Blockade of this pathway by genetic or pharmacological inhibition of PI3Kgamma blocks this immunosuppressive, wound healing gene expression program and stimulates instead a T cell activating gene expression program as well as T cell mediated tumor cell killing. PI3Kgamma blockade inhibits tumor growth and metastasis in mouse models of lung, pancreatic and breast carcinoma. Our studies demonstrate the critical role of PI3Kgamma signaling in the control of the M1-M2 macrophage switch and demonstrate that this kinase is an important therapeutic target to suppress tumor growth by targeting inflammation that is associated with all solid tumors. Citation Format: Megan Kaneda, Sara Gorjestani, Judith A. Varner. PI3-kinase gamma controls the macrophage M1-M2 switch, thereby promoting tumor immunosuppression and progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3650. doi:10.1158/1538-7445.AM2014-3650