Reprogramming tumor-associated macrophages to outcompete endovascular endothelial progenitor cells and suppress tumor neoangiogenesis.

Tumors develop by invoking a supportive environment characterized by aberrant angiogenesis and infiltration of tumor-associated macrophages (TAMs). In a transgenic model of breast cancer, we found that TAMs localized to the tumor parenchyma and were smaller than mammary tissue macrophages. TAMs had low activity of the metabolic regulator mammalian/mechanistic target of rapamycin complex 1 (mTORC1), and depletion of negative regulator of mTORC1 signaling, tuberous sclerosis complex 1 (TSC1), in TAMs inhibited tumor growth in a manner independent of adaptive lymphocytes. Whereas wild-type TAMs exhibited inflammatory and angiogenic gene expression profiles, TSC1-deficient TAMs had a pro-resolving phenotype. TSC1-deficient TAMs relocated to a perivascular niche, depleted protein C receptor (PROCR)-expressing endovascular endothelial progenitor cells, and rectified the hyperpermeable blood vasculature, causing tumor tissue hypoxia and cancer cell death. TSC1-deficient TAMs were metabolically active and effectively eliminated PROCR-expressing endothelial cells in cell competition experiments. Thus, TAMs exhibit a TSC1-dependent mTORC1-low state, and increasing mTORC1 signaling promotes a pro-resolving state that suppresses tumor growth, defining an innate immune tumor suppression pathway that may be exploited for cancer immunotherapy.

Nivolumab plus ipilimumab in advanced salivary gland cancer: a phase 2 trial.

Salivary gland cancers (SGCs) are rare, aggressive cancers without effective treatments when metastasized. We conducted a phase 2 trial evaluating nivolumab (nivo, anti-PD-1) and ipilimumab (ipi, anti-CTLA-4) in 64 patients with metastatic SGC enrolled in two histology-based cohorts (32 patients each): adenoid cystic carcinoma (ACC; cohort 1) and other SGCs (cohort 2). The primary efficacy endpoint (≥4 objective responses) was met in cohort 2 (5/32, 16%) but not in cohort 1 (2/32, 6%). Treatment safety/tolerability and progression-free survival (PFS) were secondary endpoints. Treatment-related adverse events grade ≥3 occurred in 24 of 64 (38%) patients across both cohorts, and median PFS was 4.4 months (95% confidence interval (CI): 2.4, 8.3) and 2.2 months (95% CI: 1.8, 5.3) for cohorts 1 and 2, respectively. We present whole-exome, RNA and T cell receptor (TCR) sequencing data from pre-treatment and on-treatment tumors and immune cell flow cytometry and TCR sequencing from peripheral blood at serial timepoints. Responding tumors universally demonstrated clonal expansion of pre-existing T cells and mutational contraction. Responding ACCs harbored neoantigens, including fusion-derived neoepitopes, that induced T cell responses ex vivo. This study shows that nivo+ipi has limited efficacy in ACC, albeit with infrequent, exceptional responses, and that it could be promising for non-ACC SGCs, particularly salivary duct carcinomas. ClinicalTrials.gov identifier: NCT03172624 .

Tumor-associated macrophages expressing the transcription factor IRF8 promote T cell exhaustion in cancer.

Tumors are populated by antigen-presenting cells (APCs) including macrophage subsets with distinct origins and functions. Here, we examined how cancer impacts mononuclear phagocytic APCs in a murine model of breast cancer. Tumors induced the expansion of monocyte-derived tumor-associated macrophages (TAMs) and the activation of type 1 dendritic cells (DC1s), both of which expressed and required the transcription factor interferon regulatory factor-8 (IRF8). Although DC1s mediated cytotoxic T lymphocyte (CTL) priming in tumor-draining lymph nodes, TAMs promoted CTL exhaustion in the tumor, and IRF8 was required for TAMs' ability to present cancer cell antigens. TAM-specific IRF8 deletion prevented exhaustion of cancer-cell-reactive CTLs and suppressed tumor growth. Tumors from patients with immune-infiltrated renal cell carcinoma had abundant TAMs that expressed IRF8 and were enriched for an IRF8 gene expression signature. Furthermore, the TAM-IRF8 signature co-segregated with CTL exhaustion signatures across multiple cancer types. Thus, CTL exhaustion is promoted by TAMs via IRF8.

Functional landscapes of POLE and POLD1 mutations in checkpoint blockade-dependent antitumor immunity.

Defects in pathways governing genomic fidelity have been linked to improved response to immune checkpoint blockade therapy (ICB). Pathogenic POLE/POLD1 mutations can cause hypermutation, yet how diverse mutations in POLE/POLD1 influence antitumor immunity following ICB is unclear. Here, we comprehensively determined the effect of POLE/POLD1 mutations in ICB and elucidated the mechanistic impact of these mutations on tumor immunity. Murine syngeneic tumors harboring Pole/Pold1 functional mutations displayed enhanced antitumor immunity and were sensitive to ICB. Patients with POLE/POLD1 mutated tumors harboring telltale mutational signatures respond better to ICB than patients harboring wild-type or signature-negative tumors. A mutant POLE/D1 function-associated signature-based model outperformed several traditional approaches for identifying POLE/POLD1 mutated patients that benefit from ICB. Strikingly, the spectrum of mutational signatures correlates with the biochemical features of neoantigens. Alterations that cause POLE/POLD1 function-associated signatures generate T cell receptor (TCR)-contact residues with increased hydrophobicity, potentially facilitating T cell recognition. Altogether, the functional landscapes of POLE/POLD1 mutations shape immunotherapy efficacy.

Single-cell sequencing links multiregional immune landscapes and tissue-resident T cells in ccRCC to tumor topology and therapy efficacy.

Clear cell renal cell carcinomas (ccRCCs) are highly immune infiltrated, but the effect of immune heterogeneity on clinical outcome in ccRCC has not been fully characterized. Here we perform paired single-cell RNA (scRNA) and T cell receptor (TCR) sequencing of 167,283 cells from multiple tumor regions, lymph node, normal kidney, and peripheral blood of two immune checkpoint blockade (ICB)-naïve and four ICB-treated patients to map the ccRCC immune landscape. We detect extensive heterogeneity within and between patients, with enrichment of CD8A+ tissue-resident T cells in a patient responsive to ICB and tumor-associated macrophages (TAMs) in a resistant patient. A TCR trajectory framework suggests distinct T cell differentiation pathways between patients responding and resistant to ICB. Finally, scRNA-derived signatures of tissue-resident T cells and TAMs are associated with response to ICB and targeted therapies across multiple independent cohorts. Our study establishes a multimodal interrogation of the cellular programs underlying therapeutic efficacy in ccRCC.

Mutations in BRCA1 and BRCA2 differentially affect the tumor microenvironment and response to checkpoint blockade immunotherapy.

Immune checkpoint blockade (ICB) has improved outcomes for patients with advanced cancer, but the determinants of response remain poorly understood. Here we report differential effects of mutations in the homologous recombination genes BRCA1 and BRCA2 on response to ICB in mouse and human tumors, and further show that truncating mutations in BRCA2 are associated with superior response compared to those in BRCA1. Mutations in BRCA1 and BRCA2 result in distinct mutational landscapes and differentially modulate the tumor-immune microenvironment, with gene expression programs related to both adaptive and innate immunity enriched in BRCA2-deficient tumors. Single-cell RNA sequencing further revealed distinct T cell, natural killer, macrophage, and dendritic cell populations enriched in BRCA2-deficient tumors. Taken together, our findings reveal the divergent effects of BRCA1 and BRCA2-deficiency on ICB outcome, and have significant implications for elucidating the genetic and microenvironmental determinants of response to immunotherapy.

Diverse Neoantigens and the Development of Cancer Therapies.

Cancer is the manifestation of uncontrolled cellular growth and immune escape mechanisms. Unrestrained tumor growth can be associated with incidental errors in the genome during replication and genotoxic agents can alter the structure and sequence of our DNA. Among all genetic aberrations in cancer, only limited number of mutations can produce immunogenic antigens which have the potential to bind human leukocyte antigen class I or human leukocyte antigen class II, and help activate the adaptive immune system. These neoantigens can be recognized by CD8+ and CD4+ neoantigen-specific T lymphocytes. Recently, several immune checkpoint targeting drugs have been approved for clinical use. Primarily, these drugs expand and facilitate the cytotoxic activity of neoantigen-specific T cells to eradicate tumors. Differential drug response across cancers could be attributed, at least in part, to differences in the 'tumor antigen landscape' and 'antigen presentation pathway' in patients. Although tumor mutational burden correlates with response to immune checkpoint inhibitors in many cancer types and has evolved as a broad biomarker, a comprehensive understanding of the neoantigen landscape and the function of cognate T cell responses is lacking and is needed for improved patient selection criteria and neoantigen vaccine design. Here, we review cancer neoantigens, their implications for antitumor responses, the dynamics of neoantigen-specific T cells, and the advancement of neoantigen-based therapy in proposed clinical trials.

Immunogenic neoantigens derived from gene fusions stimulate T cell responses.

Anti-tumor immunity is driven by self versus non-self discrimination. Many immunotherapeutic approaches to cancer have taken advantage of tumor neoantigens derived from somatic mutations. Here, we demonstrate that gene fusions are a source of immunogenic neoantigens that can mediate responses to immunotherapy. We identified an exceptional responder with metastatic head and neck cancer who experienced a complete response to immune checkpoint inhibitor therapy, despite a low mutational load and minimal pre-treatment immune infiltration in the tumor. Using whole-genome sequencing and RNA sequencing, we identified a novel gene fusion and demonstrated that it produces a neoantigen that can specifically elicit a host cytotoxic T cell response. In a cohort of head and neck tumors with low mutation burden, minimal immune infiltration and prevalent gene fusions, we also identified gene fusion-derived neoantigens that generate cytotoxic T cell responses. Finally, analyzing additional datasets of fusion-positive cancers, including checkpoint-inhibitor-treated tumors, we found evidence of immune surveillance resulting in negative selective pressure against gene fusion-derived neoantigens. These findings highlight an important class of tumor-specific antigens and have implications for targeting gene fusion events in cancers that would otherwise be less poised for response to immunotherapy, including cancers with low mutational load and minimal immune infiltration.

STING activation enhances cetuximab-mediated NK cell activation and DC maturation and correlates with HPV+ status in head and neck cancer.

OBJECTIVES: The intracellular DNA sensor stimulator of interferon genes (STING) has recently been shown to play a vital role in anti-viral and anti-tumor immune responses stimulating cytokine production. While human papillomavirus (HPV) is a causative agent for a subset of head and neck squamous cell carcinoma (HNSCC) with unique etiology and clinical outcome, how the STING pathway is regulated in a virus-induced tumor microenvironment is not well understood. Since STING inactivation likely reflects immunoescape via innate immunity, we hypothesized that its restoration would improve efficacy of the immune modulatory monoclonal antibody (mAb), cetuximab. MATERIALS AND METHODS: We correlated STING protein expression with clinical parameters by immunohistochemistry (n = 106) and its mRNA expression from The Cancer Genome Atlas (TCGA) in HNSCC tissue specimens. STING protein expression was tested for association with cancer-specific survival (CSS). We further examined the impact of STING activation on cetuximab-mediated immunity using an in vitro NK:DC:tumor cells co-culture system. RESULTS: In this study, we found that expression of STING both at the protein and mRNA level was higher in HPV positive (HPV+) specimens but unrelated to TNM stage or cancer-specific survival. Our in vitro studies verified that STING activation enhanced cetuximab mediated NK cell activation and DC maturation. CONCLUSION: Our findings suggest a novel role of STING in HPV-related carcinogenesis, in which activation of the STING signaling pathway may facilitate anti-tumor response in HNSCC patients, particularly in combination with therapeutic monoclonal antibodies (mAbs) such as cetuximab, an epidermal growth factor receptor (EGFR) inhibitor.

Phase Ib Study of Immune Biomarker Modulation with Neoadjuvant Cetuximab and TLR8 Stimulation in Head and Neck Cancer to Overcome Suppressive Myeloid Signals.

Purpose: The response rate of patients with head and neck squamous cell carcinoma (HNSCC) to cetuximab therapy is only 15% to 20%, despite frequent EGFR overexpression. Because immunosuppression is common in HNSCC, we hypothesized that adding a proinflammatory TLR8 agonist to cetuximab therapy might result in enhanced T-lymphocyte stimulation and anti-EGFR-specific priming.Experimental Design: Fourteen patients with previously untreated HNSCC were enrolled in this neoadjuvant trial and treated preoperatively with 3 to 4 weekly doses of motolimod (2.5 mg/m2) and cetuximab. Correlative tumor and peripheral blood specimens were obtained at baseline and at the time of surgical resection and analyzed for immune biomarker changes. Preclinical in vitro studies were also performed to assess the effect of cetuximab plus motolimod on myeloid cells.Results: TLR8 stimulation skewed monocytes toward an M1 phenotype and reversed myeloid-derived suppressor cell (MDSC) suppression of T-cell proliferation in vitro These data were validated in a prospective phase Ib neoadjuvant trial, in which fewer MDSC and increased M1 monocyte infiltration were found in tumor-infiltrating lymphocytes. Motolimod plus cetuximab also decreased induction of Treg and reduced markers of suppression, including CTLA-4, CD73, and membrane-bound TGFß. Significantly increased circulating EGFR-specific T cells were observed, concomitant with enhanced CD8+ T-cell infiltration into tumors. These T cells manifested increased T-cell receptor (TCR) clonality, upregulation of the costimulatory receptor CD27, and downregulation of inhibitory receptor TIGIT.Conclusions: Enhanced inflammatory stimulation in the tumor microenvironment using a TLR agonist overcomes suppressive myeloid and regulatory cells, enhancing the cellular antitumor immune response by therapeutic mAb in HNSCC. Clin Cancer Res; 24(1); 62-72. ©2017 AACR.

PD-1 Status in CD8+ T Cells Associates with Survival and Anti-PD-1 Therapeutic Outcomes in Head and Neck Cancer.

Improved understanding of expression of immune checkpoint receptors (ICR) on tumor-infiltrating lymphocytes (TIL) may facilitate more effective immunotherapy in head and neck cancer (HNC) patients. A higher frequency of PD-1+ TIL has been reported in human papillomavirus (HPV)+ HNC patients, despite the role of PD-1 in T-cell exhaustion. This discordance led us to hypothesize that the extent of PD-1 expression more accurately defines T-cell function and prognostic impact, because PD-1high T cells may be more exhausted than PD-1low T cells and may influence clinical outcome and response to anti-PD-1 immunotherapy. In this study, PD-1 expression was indeed upregulated on HNC patient TIL, and the frequency of these PD-1+ TIL was higher in HPV+ patients (P = 0.006), who nonetheless experienced significantly better clinical outcome. However, PD-1high CD8+ TILs were more frequent in HPV- patients and represented a more dysfunctional subset with compromised IFN-γ secretion. Moreover, HNC patients with higher frequencies of PD-1high CD8+ TIL showed significantly worse disease-free survival and higher hazard ratio for recurrence (P < 0.001), while higher fractions of PD-1low T cells associated with HPV positivity and better outcome. In a murine HPV+ HNC model, anti-PD-1 mAb therapy differentially modulated PD-1high/low populations, and tumor rejection associated with loss of dysfunctional PD-1high CD8+ T cells and a significant increase in PD-1low TIL. Thus, the extent of PD-1 expression on CD8+ TIL provides a potential biomarker for anti-PD-1-based immunotherapy. Cancer Res; 77(22); 6353-64. ©2017 AACR.

Preclinical immunoPET/CT imaging using Zr-89-labeled anti-PD-L1 monoclonal antibody for assessing radiation-induced PD-L1 upregulation in head and neck cancer and melanoma.

Radiation therapy (RT) can induce upregulation of programmed death ligand 1 (PD-L1) on tumor cells or myeloid cells, which may affect response to PD-1-based immunotherapy. PD-L1 upregulation during RT is a dynamic process that has been difficult to monitor during treatment. The aim of this study was to evaluate the RT-induced PD-L1 upregulation in the tumor and its microenvironment using immunoPET/CT imaging of two syngeneic murine tumor models (HPV+ head and neck squamous cell carcinoma (HNSCC) or B16F10 melanoma). Tumors were established in two locations per mouse (neck and flank), and fractionated RT (2 Gy × 4 or 2 Gy × 10) was delivered only to the neck tumor, alone or during anti-PD-1 mAb immunotherapy. PD-L1 expression was measured by PET/CT imaging using Zr-89 labeled anti-mouse PD-L1 mAb, and results were validated by flow cytometry. PET/CT imaging demonstrated significantly increased tracer uptake in irradiated neck tumors compared with non-irradiated flank tumors. Ex vivo analysis by biodistribution and flow cytometry validated PD-L1 upregulation specifically in irradiated tumors. In the HNSCC model, RT-induced PD-L1 upregulation was only observed after 2 Gy × 10 fractionated RT, while in the B16F10 model upregulation of PD-L1 occurred after 2 Gy × 4 fractionated RT. Fractionated RT, but not anti-PD-1 therapy, upregulated PD-L1 expression on tumor and infiltrating inflammatory cells in murine models, which could be non-invasively monitored by immunoPET/CT imaging using Zr-89 labeled anti-mouse PD-L1 mAb, and differentially identified anti-PD-1 responsive as well as selectively irradiated tumors in vivo.

Nimotuzumab Induces NK Cell Activation, Cytotoxicity, Dendritic Cell Maturation and Expansion of EGFR-Specific T Cells in Head and Neck Cancer Patients.

Survival benefit and long-term duration of clinical response have been seen using the epidermal growth factor receptor (EGFR)-targeted monoclonal antibody (mAb) nimotuzumab. Blocking EGFR signaling may not be the only mechanism of action underlying its efficacy. As an IgG1 isotype mAb, nimotuzumab's capacity of killing tumor cells by antibody dependent cellular cytotoxicity (ADCC) and to induce an immune response in cancer patients have not been studied. ADCC-induced by nimotuzumab was determined using a 51Cr release assay. The in vitro effect of nimotuzumab on natural killer (NK) cell activation and dendritic cell (DC) maturation and the in vivo frequency of circulating regulatory T cells (Tregs) and NK cells were assessed by flow cytometry. Cytokine levels in supernatants were determined by ELISA. ELISpot was carried out to quantify EGFR-specific T cells in nimotuzumab-treated head and neck cancer (HNSCC) patients. Nimotuzumab was able to kill EGFR+ tumor cells by NK cell-mediated ADCC. Nimotuzumab-activated NK cells promoted DC maturation and EGFR-specific CD8+ T cell priming. Interestingly, nimotuzumab led to upregulation of some immune checkpoint molecules on NK cells (TIM-3) and DC (PD-L1), to a lower extent than another EGFR mAb, cetuximab. Furthermore, circulating EGFR-specific T cells were identified in nimotuzumab-treated HNSCC patients. Notably, nimotuzumab combined with cisplatin-based chemotherapy and radiation increased the frequency of peripheral CD4+CD39+FOXP3+Tregs which otherwise were decreased to baseline values when nimotuzumab was used as monotherapy. The frequency of circulating NK cells remained constant during treatment. Nimotuzumab-induced, NK cell-mediated DC priming led to induction of anti-EGFR specific T cells in HNSCC patients. The association between EGFR-specific T cells and patient clinical benefit with nimotuzumab treatment should be investigated.

Increased PD-1+ and TIM-3+ TILs during Cetuximab Therapy Inversely Correlate with Response in Head and Neck Cancer Patients.

Despite emerging appreciation for the important role of immune checkpoint receptors in regulating the effector functions of T cells, it is unknown whether their expression is involved in determining the clinical outcome in response to cetuximab therapy. We examined the expression patterns of immune checkpoint receptors (including PD-1, CTLA-4, and TIM-3) and cytolytic molecules (including granzyme B and perforin) of CD8+ tumor-infiltrating lymphocytes (TIL) and compared them with those of peripheral blood T lymphocytes (PBL) in patients with head and neck cancer (HNSCC) during cetuximab therapy. The frequency of PD-1 and TIM-3 expression was significantly increased in CD8+ TILs compared with CD8+ PBLs (P = 0.008 and P = 0.02, respectively). This increased CD8+ TIL population coexpressed granzyme B/perforin and PD-1/TIM-3, which suggests a regulatory role for these immune checkpoint receptors in cetuximab-promoting cytolytic activities of CD8+ TILs. Indeed, the increased frequency of PD-1+ and TIM-3+ CD8+ TILs was inversely correlated with clinical outcome of cetuximab therapy. These findings support the use of PD-1 and TIM-3 as biomarkers to reflect immune status of CD8+ T cells in the tumor microenvironment during cetuximab therapy. Blockade of these immune checkpoint receptors might enhance cetuximab-based cancer immunotherapy to reverse CD8+ TIL dysfunction, thus potentially improving clinical outcomes of HNSCC patients. Cancer Immunol Res; 5(5); 408-16. ©2017 AACR.

CD137 Stimulation Enhances Cetuximab-Induced Natural Killer: Dendritic Cell Priming of Antitumor T-Cell Immunity in Patients with Head and Neck Cancer.

PURPOSE: Cetuximab, an EGFR-specific antibody (mAb), modestly improves clinical outcome in patients with head and neck cancer (HNC). Cetuximab mediates natural killer (NK) cell:dendritic cell (DC) cross-talk by cross-linking FcγRIIIa, which is important for inducing antitumor cellular immunity. Cetuximab-activated NK cells upregulate the costimulatory receptor CD137 (4-1BB), which, when triggered by agonistic mAb urelumab, might enhance NK-cell functions, to promote T-cell-based immunity. EXPERIMENTAL DESIGN: CD137 expression on tumor-infiltrating lymphocytes was evaluated in a prospective cetuximab neoadjuvant trial, and CD137 stimulation was evaluated in a phase Ib trial, in combining agonistic urelumab with cetuximab. Flow cytometry and cytokine release assays using NK cells and DC were used in vitro, testing the addition of urelumab to cetuximab-activated NK, DC, and cross presentation to T cells. RESULTS: CD137 agonist mAb urelumab enhanced cetuximab-activated NK-cell survival, DC maturation, and tumor antigen cross-presentation. Urelumab boosted DC maturation markers, CD86 and HLA DR, and antigen-processing machinery (APM) components TAP1/2, leading to increased tumor antigen cross-presentation. In neoadjuvant cetuximab-treated patients with HNC, upregulation of CD137 by intratumoral, cetuximab-activated NK cells correlated with FcγRIIIa V/F polymorphism and predicted clinical response. Moreover, immune biomarker modulation was observed in an open label, phase Ib clinical trial, of patients with HNC treated with cetuximab plus urelumab. CONCLUSIONS: These results suggest a beneficial effect of combination immunotherapy using cetuximab and CD137 agonist in HNC. Clin Cancer Res; 23(3); 707-16. ©2016 AACR.

Anti-EGFR Targeted Monoclonal Antibody Isotype Influences Antitumor Cellular Immunity in Head and Neck Cancer Patients.

PURPOSE: EGF receptor (EGFR) is highly overexpressed on several cancers and two targeted anti-EGFR antibodies which differ by isotype are FDA-approved for clinical use. Cetuximab (IgG1 isotype) inhibits downstream signaling of EGFR and activates antitumor, cellular immune mechanisms. As panitumumab (IgG2 isotype) may inhibit downstream EGFR signaling similar to cetuximab, it might also induce adaptive immunity. EXPERIMENTAL DESIGN: We measured in vitro activation of cellular components of the innate and adaptive immune systems. We also studied the in vivo activation of components of the adaptive immune system in patient specimens from two recent clinical trials using cetuximab or panitumumab. RESULTS: Both monoclonal antibodies (mAb) primarily activate natural killer (NK) cells, although cetuximab is significantly more potent than panitumumab. Cetuximab-activated neutrophils mediate antibody-dependent cellular cytotoxicity (ADCC) against head and neck squamous cell carcinomas (HNSCC) tumor cells, and interestingly, this effect was FcγRIIa- and FcγRIIIa genotype-dependent. Panitumumab may activate monocytes through CD32 (FcγRIIa); however, monocytes activated by either mAb are not able to mediate ADCC. Cetuximab enhanced dendritic cell (DC) maturation to a greater extent than panitumumab, which was associated with improved tumor antigen cross-presentation by cetuximab compared with panitumumab. This correlated with increased EGFR-specific cytotoxic CD8+ T cells in patients treated with cetuximab compared with those treated with panitumumab. CONCLUSIONS: Although panitumumab effectively inhibits EGFR signaling to a similar extent as cetuximab, it is less effective at triggering antitumor, cellular immune mechanisms which may be crucial for effective therapy of HNSCC. Clin Cancer Res; 22(21); 5229-37. ©2016 AACR.

Identification of the Cell-Intrinsic and -Extrinsic Pathways Downstream of EGFR and IFNγ That Induce PD-L1 Expression in Head and Neck Cancer.

Many cancer types, including head and neck cancers (HNC), express programmed death ligand 1 (PD-L1). Interaction between PD-L1 and its receptor, programmed death 1 (PD-1), inhibits the function of activated T cells and results in an immunosuppressive microenvironment, but the stimuli that induce PD-L1 expression are not well characterized. Interferon gamma (IFNγ) and the epidermal growth factor receptor (EGFR) utilize Janus kinase 2 (JAK2) as a common signaling node to transmit tumor cell-mediated extrinsic or intrinsic signals, respectively. In this study, we investigated the mechanism by which these factors upregulate PD-L1 expression in HNC cells in the context of JAK/STAT pathway activation, Th1 inflammation, and HPV status. We found that wild-type, overexpressed EGFR significantly correlated with JAK2 and PD-L1 expression in a large cohort of HNC specimens. Furthermore, PD-L1 expression was induced in an EGFR- and JAK2/STAT1-dependent manner, and specific JAK2 inhibition prevented PD-L1 upregulation in tumor cells and enhanced their immunogenicity. Collectively, our findings suggest a novel role for JAK2/STAT1 in EGFR-mediated immune evasion, and therapies targeting this signaling axis may be beneficial to block PD-L1 upregulation found in a large subset of HNC tumors.

Cetuximab ameliorates suppressive phenotypes of myeloid antigen presenting cells in head and neck cancer patients.

BACKGROUND: Myeloid-derived suppressor cells (MDSC) and M2 monocytes/macrophages are two types of suppressive myeloid antigen presenting cells that have been shown to promote tumor progression and correlate with poor prognosis in cancer patients. Tumor antigen specific monoclonal antibodies (mAb) have emerged as important agents for cancer therapy. In addition to the direct inhibition of tumor growth, the Fc portions of the therapeutic mAbs, such as the IgG1 portion of the anti-epidermal growth factor receptor (EGFR) mAb cetuximab, might interact with the Fc-gamma receptors (FcγR) on myeloid cells and modulate their suppressive activity. METHODS: Patients with locally advanced head and neck squamous cell carcinoma (HNSCC) on the UPCI 08-013 NCT01218048 trial were treated with single-agent cetuximab before surgery. Blood were collected pre- and post-cetuximab treatment to analyze frequency of monocytic MDSC (CD11b(+)CD14(+)HLA-DR(lo/-)), granulocytic MDSC (LIN(-)CD11b(+)CD15(+)) and CD11b(+)CD14(+)HLA-DR(hi) monocytes by flow cytometry. Besides, CD11b(+)CD14(+)HLA-DR(hi) monocytes were sorted for qPCR analysis of IL-10 and IL-12B transcripts. MDSC were generated in vitro with or without coated hIgG1 and tested for suppressive activity in mixed leukocyte reaction (MLR). Naïve monocytes from HNSCC patients co-cultured with tumor cell lines in the presence of cetuximab or hIgG1 were analyzed for M1/2 surface markers and cytokines. RESULTS: We observed significantly increased monocytic MDSC in non-responders and decreased granulocytic MDSC in responders after cetuximab treatment. In addition, circulating CD11b(+)CD14(+)HLA-DR(hi) monocytes of cetuximab responders displayed attenuated M2 polarization, with decreased CD163(+) expression and IL-10 transcripts after cetuximab treatment. This beneficial effect appeared to be FcγR dependent, since CD16 ligation reproduced the reversal of suppressive activity of MDSC in vitro. CD14(+) naïve monocytes from the co-cultures of tumor cells, cetuximab and HNSCC patient PBMC or purified monocytes were skewed to an M1-like phenotype, with increased expression of HLA-DR, CD86 and production of IL-12 p70. Likewise, reduced M2 features (expression of CD163 and production of IL-10) were found after crosslinking CD16 on the surface of monocytes to cetuximab-coated tumor cells. CONCLUSION: Our studies demonstrate a novel function of cetuximab in ameliorating suppressive phenotypes of FcγR bearing myeloid cells in cancer patients, which is associated with better clinical outcome of cetuximab-treated patients. CLINICAL TRIAL REGISTRY: #NCT01218048. Registered 7 October 2010.