Abstract 3862: Defining immune contexture in small cell lung cancer: Implications for immunotherapy

Introduction: Small cell lung cancer (SCLC) is an aggressive neuroendocrine malignancy with limited treatment options and median survival approximately 1 year after diagnosis even with treatment. SCLC patients typically respond to platinum-based cytotoxic chemotherapy, but drug resistance and resultant disease progression rapidly develop, driving the 5-year patient survival rate to <5%. The emergence of immunotherapy (IO) offers promising therapeutics for this disease. However, recently FDA approved immunotherapies only improve overall survival (OS) of SCLC patients by 2 months (chemotherapy OS: 10 mos.; chemotherapy + IO OS: 12 mos.). Little is known about the immune landscape in SCLC. We assert that a better understanding of this immune contexture, defined as abundance, type, and location of immune cells, in SCLC may provide important criteria for patient stratification.

Objectives: The primary objective of this study is to comprehensively and quantitatively identify immune cell subsets and their associated functional states in small cell lung cancer to address critical knowledge gaps in the tumor biology of the disease.

Methods: To broadly/robustly audit immune contexture in SCLC, we generated tissue-microarrays containing >200 unique patient specimens with fully annotated clinical data. Next, we used an innovative and highly multiplex immunohistochemistry (mIHC) platform consisting of a panel of highly validated antibodies and a computational pipeline. Importantly, mIHC enables cell classification via image cytometry, for identification of immune cell subsets, including: T cells (CD3+, CD4, CD8), B cells (CD20+), granulocytes (CD66b+) Th2-skewed monocytes and macrophages (CD11b+ CD68+ CD163+), and dendritic cells (CD68− CD11c+ HLA-DR+, DC-LAMP+/−). Further, functional markers provide insight into immune checkpoints (PD-1, PD-L1), proliferation (Ki67), and T cell functionality (EOMES, granzyme B).

Results: Preliminary observations show a wide variability in total immune cell (CD45+) infiltrate, with most infiltrate excluded or peripheral to tumor nests. Further, myeloid immune infiltrates often dominate over lymphoid infiltrates in terms of overall abundance, however variability exists. In particular CD8+ T cells are relatively low in abundance and often excluded from tumor nests in most tumors. Future analysis will deeply phenotype immune cell types and localization, as well as capture interpatient heterogeneity.

Conclusions: Understanding the immune landscape of SCLC could further understanding of SCLC immune suppression and evasion, ultimately leading to optimal single-agent immunotherapy deployment and rational, effective combination therapy for patients with SCLC.

Citation Format: Portia L. Thomas, Courtney Betts, Giovanney Gonzalez, Lisa M. Coussens, Christine M. Lovly. Defining immune contexture in small cell lung cancer: Implications for immunotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3862.

Evaluation of Cyclophosphamide/GVAX Pancreas Followed by Listeria-Mesothelin (CRS-207) with or without Nivolumab in Patients with Pancreatic Cancer

PURPOSE

Two studies in previously treated metastatic pancreatic cancer have been completed combining GVAX pancreas vaccine (GM-CSF-secreting allogeneic pancreatic tumor cells) with cyclophosphamide (Cy) and CRS-207 (live, attenuated Listeria monocytogenes-expressing mesothelin). In the current study, we compared Cy/GVAX followed by CRS-207 with (Arm A) or without nivolumab (Arm B).

PATIENTS AND METHODS

Patients with pancreatic adenocarcinoma who received one prior therapy for metastatic disease and RECIST measurable disease were randomized 1:1 to receive treatment on Arm A or Arm B. The primary objective was to compare overall survival (OS) between the arms. Additional objectives included assessment of progression-free survival, safety, tumor responses, CA19-9 responses, and immunologic correlates.

RESULTS

Ninety-three patients were treated (Arm A, 51; Arm B, 42). The median OS in Arms A and B were 5.9 [95% confidence interval (CI), 4.7-8.6] and 6.1 (95% CI, 3.5-7.0) months, respectively, with an HR of 0.86 (95% CI, 0.55-1.34). Objective responses were seen in 3 patients using immune-related response criteria (4%, 2/51, Arm A; 2%, 1/42, Arm B). The grade ≥3 related adverse event rate, whereas higher in Arm A (35.3% vs. 11.9%) was manageable. Changes in the microenvironment, including increase in CD8+ T cells and a decrease in CD68+ myeloid cells, were observed in long-term survivors in Arm A only.

CONCLUSIONS

Although the study did not meet its primary endpoint of improvement in OS of Arm A over Arm B, the OS was comparable with standard therapy. Objective responses and immunologic changes in the tumor microenvironment were evident.

Abstract IA26: Dynamic interactions between myeloid and lymphoid cells regulate response to therapy in solid tumors

The concept that leukocytes are critical components of solid tumors is now generally accepted; however, their role(s) in regulating aspects of neoplastic progression, and/or response to cytotoxic, targeted, and/or immune therapy is only beginning to be understood. Utilizing de novo mouse models of organ-specific solid tumor development (mammary, cutaneous, and pancreas carcinomas and mesothelioma), we now appreciate that adaptive leukocytes differentially regulate myeloid cell recruitment, activation, and effector function, and in turn, activated tumor-infiltrating myeloid cells engage tissue-based programs to foster malignancy and repress antitumor immunity by a diversity of mechanisms. Treatment of tumor-bearing mice with therapeutic agents that disrupt lymphocyte-myeloid cell interaction, myeloid cell activation, or myeloid cell functionality generally slows primary tumor growth kinetics when combined with cytotoxic therapy; however, their impact on metastases is variable. Similar to organ-specific regulatory programs co-opted to foster primary tumor growth, regulation of metastatic seeding and outgrowth is also regulated by tissue- and organ-specific mechanisms. Based on this, it stands to reason that therapeutic strategies may not be efficacious in both primary and metastatic locations. To be presented will be our recent insights into organ- and tissue-specific regulation of primary and metastatic cancer development by adaptive and innate immune cells, how systemic regulation of humoral immunity and complement-mediated pathways regulate pro- versus antitumor immune responses, and new studies evaluating how attenuating protumor properties of select lymphoid and myeloid cells can be exploited to enhance therapeutic responses to cytotoxic and immune-based therapy.

LMC acknowledges generous support from the NIH/NCI, the Department of Defense Breast Cancer Research Program Era of Hope Scholar Expansion Award, Susan G. Komen Foundation, the Breast Cancer Research Foundation, the Brenden-Colson Center for Pancreatic Health, and a Stand Up To Cancer-Lustgarten Foundation Pancreatic Cancer Convergence Dream Team Translational Research Grant.

Citation Format: Lisa M. Coussens. Dynamic interactions between myeloid and lymphoid cells regulate response to therapy in solid tumors [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr IA26.

Abstract A03: Relieving immune suppressive pathways in breast cancer to improve outcomes

Triple-negative breast cancer (TNBC) patients die at a disproportionately high rate due to multiple factors contributing to the aggressive and metastatic nature of the disease, exacerbated by the fact that treatment options are lacking once chemotherapy (CTX) and/or radiation therapy fails. While treatment of metastatic cancers with immune checkpoint inhibitors (ICIs) is offering great promise for many, early results from clinical trials evaluating ICIs in TNBC showed promise for only a small percentage of patients. Preclinical data indicate that myeloid cells, notably infiltrating tumor-associated macrophages (TAMs) and monocyte subtypes limit CD8+ T cell infiltration, activation and cytotoxic activity in tumor microenvironments, and thereby foster development of immunologically “cold” tumors. We hypothesized that response to ICI therapy in immunologically “cold” TNBCs would be enhanced by treating mammary tumor-bearing transgenic mice with a microtubule poison like paclitaxel (PTX) that enhances tumor immunogenicity, with macrophage-depleting/reprograming therapies, e.g., antagonists of colony-stimulating factor 1 or its receptor (CSF1/CSF1R), in combination with agents that inhibit checkpoint molecules expressed on CD8+ T cells, e.g., PD-1. Immune-competent mammary tumor-bearing MMTV-PyMT transgenic mice were randomized at day 80, and enrolled into experimental groups evaluating effects of PTX, CSF1/CSF1R antagonists, aPD-1 mAb each as monotherapy, each in combination with one other of the drugs, versus the triple combination. Where MMTV-PyMT mammary tumors are resistant to PTX, CSF1/CSF1R inhibitors and aPD-1 mAb as monotherapies, responsive tumors emerge when PTX is combined with either CSF1/CSF1R antagonists or aPD-1 mAb with primary tumor growth kinetics significantly slowed, but still growing. In contrast, mammary tumors in mice treated with the three agents together (PTX, CSF1/CSF1R antagonist, aPD-1 mAb) undergo rapid tumor regression in 60% of mice, coincident with significant diminution in presence of pulmonary metastasis as compared to PTX - CSF1/CSF1R antagonist dual combination therapy. Regressing tumors are associated with increased presence of effector memory and resident memory CD8+ T cells exhibiting antigen-specific clonal expansion (based on T-cell receptor sequence analysis). To be presented will be results from studies evaluating transcriptional programs differentially regulated in macrophages, dendritic cells, monocytes and CD8+ T cells in response to therapy and mechanistic findings underlying improved CD8+ T-cell cytotoxicity. The authors acknowledge generous support from the NIH / NCI, the Department of Defense Breast Cancer Research Program Era of Hope Scholar Expansion Award, Susan G. Komen Foundation, the Breast Cancer Research Foundation, and the Brenden-Colson Center for Pancreatic Health.

Citation Format: Amanda Poissonnier, Dhaarini Murugan, Wesley Horton, Tiziana Cotechini, Hope S. Rugo, Lisa M. Coussens. Relieving immune suppressive pathways in breast cancer to improve outcomes [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A03.

Abstract PR11: Tumor cell-intrinsic factors underlie the heterogeneity of immune infiltration and response to immunotherapy in pancreatic cancer

Intertumoral heterogeneity—the biologic and functional differences among different individual tumors—poses a challenge for immunotherapy. To understand the tumor cell-intrinsic factors underlying the heterogeneity of tumor immunity and sensitivity to immunotherapy, we established a new experimental system by generating a library of congenic pancreatic tumor cell clones from a genetic mouse model driven by mutant Kras and p53. These tumor cell clones robustly formed implanted tumors that recapitulated the T cell-inflamed and non-T cell-inflamed tumor microenvironments in human patients, associated with distinct patterns of infiltration by T cells and myeloid cells. We found that the non-T cell-inflamed phenotype was dominant over the T cell-inflamed phenotype in the local tumor microenvironment. Both quantitative and qualitative features, specifically expression of markers of prior TCR activation, of intratumoral CD8+ T cells predicted the response to immunotherapies. An integrated transcriptomic and epigenetic analysis revealed that tumor cell-intrinsic expression of the chemokine CXCL1 as a major determinant of the non-T cell-inflamed microenvironment, and ablation of tumor cell-intrinsic CXCL1, promoted T-cell infiltration and sensitivity to a combination of chemotherapies, CD40 agonist, and checkpoint blockades. These results demonstrated that heterogeneity of tumor immune phenotypes is driven by tumor cell-intrinsic factors that can be manipulated to influence the outcome of immunotherapies. The observation that non-T cell-inflamed phenotype is dominant emphasized the importance of targeting mechanisms driving T-cell low phenotype for improving immunotherapy response. This experimental system will provide opportunities for understanding other aspects of tumor heterogeneity as well.

This abstract is also being presented as Poster A45.

Citation Format: Jinyang Li, Katelyn T. Byrne, Fangxue Yan, Taiji Yamazoe, Zeyu Chen, Timour Baslan, Lee P. Richman, Jeffrey Lin, Yu H. Sun, Shannon M. Liudahl, John W. Tobias, Scott Lowe, Lisa M. Coussens, John E Wherry, Robert H. Vonderheide, Ben Z. Stanger. Tumor cell-intrinsic factors underlie the heterogeneity of immune infiltration and response to immunotherapy in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr PR11.

Myeloid Cells Orchestrate Systemic Immunosuppression, Impairing the Efficacy of Immunotherapy against HPV+ Cancers

Cancers induced by human papillomaviruses (HPV) should be responsive to immunotherapy by virtue of expressing the immunogenic oncoproteins E6/E7. However, advanced forms of cervical cancer, driven by HPV, are poorly responsive to immune response-enhancing treatments involving therapeutic vaccination against these viral neoantigens. Leveraging a transgenic mouse model of HPV-derived cancers, K14HPV16/H2b, we demonstrated that a potent nanoparticle-based E7 vaccine, but not a conventional "liquid" vaccine, induced E7 tumor antigen-specific CD8+ T cells in cervical tumor-bearing mice. Vaccination alone or in combination with anti-PD-1/anti-CTLA4 did not elicit tumor regression nor increase CD8+ T cells in the tumor microenvironment (TME), suggesting the presence of immune-suppressive barriers. Patients with cervical cancer have poor dendritic cell functions, have weak cytotoxic lymphocyte responses, and demonstrate an accumulation of myeloid cells in the periphery. Here, we illustrated that myeloid cells in K14HPV16/H2b mice possess potent immunosuppressive activity toward antigen-presenting cells and CD8+ T cells, dampening antitumor immunity. These immune-inhibitory effects inhibited synergistic effects of combining our oncoprotein vaccine with immune checkpoint-blocking antibodies. Our data highlighted a link between HPV-induced cancers, systemic amplification of myeloid cells, and the detrimental effects of myeloid cells on CD8+ T-cell activation and recruitment into the TME. These results established immunosuppressive myeloid cells in lymphoid organs as an HPV+ cancer-induced means of circumventing tumor immunity that will require targeted abrogation to enable the induction of efficacious antitumor immune responses.

Abstract I03: Immune contexture of human pancreatic cancer

The concept that leukocytes are critical components of solid tumors is now generally accepted; however, their role(s) in regulating aspects of neoplastic progression, and/or response to cytotoxic, targeted, and/or immune therapy is only beginning to be understood. Utilizing de novo mouse models of organ-specific solid tumor development (mammary, cutaneous, and pancreas carcinomas and mesothelioma), we now appreciate that adaptive leukocytes differentially regulate myeloid cell recruitment, activation, and effector function, and in turn, activated tumor-infiltrating myeloid cells engage tissue-based programs to foster malignancy and repress antitumor immunity by a diversity of mechanisms. Treatment of tumor-bearing mice with therapeutic agents that disrupt lymphocyte-myeloid cell interaction, myeloid cell activation, or myeloid cell functionality generally slow primary tumor growth kinetics when combined with cytotoxic therapy; however, their impact on metastases is variable. Similar to organ-specific regulatory programs co-opted to foster primary tumor growth, regulation of metastatic seeding and outgrowth is also regulated by tissue- and organ-specific mechanisms. Based on this, it stands to reason that therapeutic strategies may not be efficacious in both primary and metastatic locations. To be presented will be our recent insights into organ- and tissue-specific regulation of primary and metastatic cancer development by adaptive and innate immune cells, how systemic regulation of humoral immunity and complement-mediated pathways regulate pro- versus antitumor immune responses, and new studies evaluating how attenuating protumor properties of select lymphoid and myeloid cells can be exploited to enhance therapeutic responses to cytotoxic and immune-based therapy. (LMC acknowledges generous support from the NIH/NCI, the Department of Defense Breast Cancer Research Program, Susan G. Komen Foundation, the Breast Cancer Research Foundation, and the Brenden-Colson Center for Pancreatic Health.)

Citation Format: Lisa M. Coussens. Immune contexture of human pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr I03.

The TLR7/8 agonist R848 remodels tumor and host responses to promote survival in pancreatic cancer

A priority in cancer research is to innovate therapies that are not only effective against tumor progression but also address comorbidities such as cachexia that limit quality and quantity of life. We demonstrate that TLR7/8 agonist R848 induces anti-tumor responses and attenuates cachexia in murine models of pancreatic ductal adenocarcinoma (PDAC). In vivo, tumors from two of three cell lines were R848-sensitive, resulting in smaller tumor mass, increased immune complexity, increased CD8⁺ T-cell infiltration and activity, and decreased Treg frequency. R848-treated mice demonstrated improvements in behavioral and molecular cachexia manifestations, resulting in a near-doubling of survival duration. Knockout mouse studies revealed that stromal, not neoplastic, TLR7 is requisite for R848-mediated responses. In patient samples, we found Tlr7 is ubiquitously expressed in stroma across all stages of pancreatic neoplasia, but epithelial Tlr7 expression is relatively uncommon. These studies indicate immune-enhancing approaches including R848 may be useful in PDAC and cancer-associated cachexia.

In the treatment of pancreatic ductal adenocarcinoma (PDAC), comorbidities such as cachexia limit quality of life and survival. Here, the authors show TLR7/8 agonist R848 remodels host and tumour immune responses, promoting survival and attenuating cachexia in murine models of PDAC.

Clinical Response of Live-Attenuated, Listeria monocytogenes Expressing Mesothelin (CRS-207) with Chemotherapy in Patients with Malignant Pleural Mesothelioma

PURPOSE

Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with poor prognosis. CRS-207 is a live-attenuated Listeria monocytogenes engineered to express mesothelin, a tumor-associated antigen highly expressed in MPM. CRS-207 induces antitumor immune responses and increases susceptibility of neoplastic cells to immune-mediated killing.

PATIENTS AND METHODS

Patients with unresectable MPM, ECOG 0 or 1, and adequate organ and pulmonary function were enrolled in this multicenter, open-label phase Ib study. They received two priming infusions of 1 × 109 CFU CRS-207, followed by pemetrexed/cisplatin chemotherapy, and CRS-207 booster infusions. Primary objectives were safety and induction of immune response. Secondary/exploratory objectives included tumor response, progression-free survival (PFS), overall survival (OS), immune subset analysis, and gene-expression profiling of tumor.

RESULTS

Of 35 evaluable patients, 89% (31/35) had disease control with one complete response (3%), 19 partial responses (54%), and 10 stable disease (29%). The estimated median duration of response was 5.0 months (95% CI, 3.9-11.5). The median PFS and OS were 7.5 (95% CI, 7.0-9.9) and 14.7 (95% CI, 11.2-21.9) months, respectively. Tumor size reduction was observed post-CRS-207 infusion prior to chemotherapy in 11 of 35 (31%) patients. No unexpected treatment-related serious adverse events or deaths were observed. IHC analysis of pre- and post-CRS-207 treatment tumor biopsies revealed possible reinvigoration and proliferation of T cells, increased infiltration of dendritic and natural killer cells, increased CD8:Treg ratio, and a shift from immunosuppressive M2-like to proinflammatory M1-like macrophages following CRS-207 administration.

CONCLUSIONS

Combination of CRS-207 and chemotherapy induced significant changes in the local tumor microenvironment and objective tumor responses in a majority of treated patients.

Innate αβ T Cells Mediate Antitumor Immunity by Orchestrating Immunogenic Macrophage Programming

Unconventional T-lymphocyte populations are emerging as important regulators of tumor immunity. Despite this, the role of TCRαβ⁺CD4^-CD8^-NK1.1^- innate αβ T cells (iαβT) in pancreatic ductal adenocarcinoma (PDA) has not been explored. We found that iαβTs represent ∼10% of T lymphocytes infiltrating PDA in mice and humans. Intratumoral iαβTs express a distinct T-cell receptor repertoire and profoundly immunogenic phenotype compared with their peripheral counterparts and conventional lymphocytes. iαβTs comprised ∼75% of the total intratumoral IL17⁺ cells. Moreover, iαβT-cell adoptive transfer is protective in both murine models of PDA and human organotypic systems. We show that iαβT cells induce a CCR5-dependent immunogenic macrophage reprogramming, thereby enabling marked CD4⁺ and CD8⁺ T-cell expansion/activation and tumor protection. Collectively, iαβTs govern fundamental intratumoral cross-talk between innate and adaptive immune populations and are attractive therapeutic targets. SIGNIFICANCE: We found that iαβTs are a profoundly activated T-cell subset in PDA that slow tumor growth in murine and human models of disease. iαβTs induce a CCR5-dependent immunogenic tumor-associated macrophage program, T-cell activation and expansion, and should be considered as novel targets for immunotherapy.See related commentary by Banerjee et al., p. 1164.This article is highlighted in the In This Issue feature, p. 1143.

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

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.

Phase Ib study of the combination of pexidartinib (PLX3397), a CSF-1R inhibitor, and paclitaxel in patients with advanced solid tumors

Purpose:

To evaluate the safety, recommended phase II dose (RP2D) and efficacy of pexidartinib, a colony stimulating factor receptor 1 (CSF-1R) inhibitor, in combination with weekly paclitaxel in patients with advanced solid tumors.

Patients and Methods:

In part 1 of this phase Ib study, 24 patients with advanced solid tumors received escalating doses of pexidartinib with weekly paclitaxel (80 mg/m²). Pexidartinib was administered at 600 mg/day in cohort 1. For subsequent cohorts, the dose was increased by ⩽50% using a standard 3+3 design. In part 2, 30 patients with metastatic solid tumors were enrolled to examine safety, tolerability and efficacy of the RP2D. Pharmacokinetics and biomarkers were also assessed.

Results:

A total of 51 patients reported ≥1 adverse event(s) (AEs) that were at least possibly related to either study drug. Grade 3–4 AEs, including anemia (26%), neutropenia (22%), lymphopenia (19%), fatigue (15%), and hypertension (11%), were recorded in 38 patients (70%). In part 1, no maximum tolerated dose was achieved and 1600 mg/day was determined to be the RP2D. Of 38 patients evaluable for efficacy, 1 (3%) had complete response, 5 (13%) partial response, 13 (34%) stable disease, and 17 (45%) progressive disease. No drug–drug interactions were found. Plasma CSF-1 levels increased 1.6- to 53-fold, and CD14dim/CD16+ monocyte levels decreased by 57–100%.

Conclusions:

The combination of pexidartinib and paclitaxel was generally well tolerated. RP2D for pexidartinib was 1600 mg/day. Pexidartinib blocked CSF-1R signaling, indicating potential for mitigating macrophage tumor infiltration.

Dissecting the Stromal Signaling and Regulation of Myeloid Cells and Memory Effector T Cells in Pancreatic Cancer

PURPOSE

Myeloid cells are a prominent immunosuppressive component within the stroma of pancreatic ductal adenocarcinoma (PDAC). Previously, targeting myeloid cells has had limited success. Here, we sought to target the myeloid cells through modifying a specific stromal component.

EXPERIMENTAL DESIGN

A murine model of metastatic PDAC treated with an irradiated whole-cell PDAC vaccine and PDAC specimens from patients treated with the same type of vaccine were used to assess the immune-modulating effect of stromal hyaluronan (HA) degradation by PEGPH20.

RESULTS

Targeting stroma by degrading HA with PEGPH20 in combination with vaccine decreases CXCL12/CXCR4/CCR7 immunosuppressive signaling axis expression in cancer-associated fibroblasts, myeloid, and CD8⁺ T cells, respectively. This corresponds with increased CCR7^- effector memory T-cell infiltration, an increase in tumor-specific IFNγ, and improved survival. In the stroma of human PDACs treated with the same vaccine, decreased stromal CXCR4 expression significantly correlated with decreased HA and increased cytotoxic activities, suggesting CXCR4 is an important therapeutic target.

CONCLUSIONS

This study represents the first to dissect signaling cascades following PDAC stroma remodeling via HA depletion, suggesting this not only overcomes a physical barrier for immune cell trafficking, but alters myeloid function leading to downstream selective increases in effector memory T-cell infiltration and antitumor activity.

Toward a comprehensive view of cancer immune responsiveness: a synopsis from the SITC workshop

Tumor immunology has changed the landscape of cancer treatment. Yet, not all patients benefit as cancer immune responsiveness (CIR) remains a limitation in a considerable proportion of cases. The multifactorial determinants of CIR include the genetic makeup of the patient, the genomic instability central to cancer development, the evolutionary emergence of cancer phenotypes under the influence of immune editing, and external modifiers such as demographics, environment, treatment potency, co-morbidities and cancer-independent alterations including immune homeostasis and polymorphisms in the major and minor histocompatibility molecules, cytokines, and chemokines. Based on the premise that cancer is fundamentally a disorder of the genes arising within a cell biologic process, whose deviations from normality determine the rules of engagement with the host's response, the Society for Immunotherapy of Cancer (SITC) convened a task force of experts from various disciplines including, immunology, oncology, biophysics, structural biology, molecular and cellular biology, genetics, and bioinformatics to address the complexity of CIR from a holistic view. The task force was launched by a workshop held in San Francisco on May 14-15, 2018 aimed at two preeminent goals: 1) to identify the fundamental questions related to CIR and 2) to create an interactive community of experts that could guide scientific and research priorities by forming a logical progression supported by multiple perspectives to uncover mechanisms of CIR. This workshop was a first step toward a second meeting where the focus would be to address the actionability of some of the questions identified by working groups. In this event, five working groups aimed at defining a path to test hypotheses according to their relevance to human cancer and identifying experimental models closest to human biology, which include: 1) Germline-Genetic, 2) Somatic-Genetic and 3) Genomic-Transcriptional contributions to CIR, 4) Determinant(s) of Immunogenic Cell Death that modulate CIR, and 5) Experimental Models that best represent CIR and its conversion to an immune responsive state. This manuscript summarizes the contributions from each group and should be considered as a first milestone in the path toward a more contemporary understanding of CIR. We appreciate that this effort is far from comprehensive and that other relevant aspects related to CIR such as the microbiome, the individual's recombined T cell and B cell receptors, and the metabolic status of cancer and immune cells were not fully included. These and other important factors will be included in future activities of the taskforce. The taskforce will focus on prioritization and specific actionable approach to answer the identified questions and implementing the collaborations in the follow-up workshop, which will be held in Houston on September 4-5, 2019.

Reprogramming the Tumor Microenvironment to Improve Immunotherapy: Emerging Strategies and Combination Therapies

Emerging immunotherapeutic approaches have revolutionized the treatment of multiple malignancies. Immune checkpoint blockers (ICBs) have enabled never-before-seen success rates in durable tumor control and enhanced survival benefit in patients with advanced cancers. However, this effect is not universal, resulting in responder and nonresponder populations not only between, but also within solid tumor types. Although ICBs are thought to be most effective against tumors with more genetic mutations and higher antigen loads, this is not always the case for all cancers or for all patients within a cancer subtype. Furthermore, debilitating and sometimes deadly immune-related adverse events (irAEs) have resulted from aberrant activation of T-cell responses following immunotherapy. Thus, we must identify new ways to overcome resistance to ICB-based immunotherapies and limit irAEs. In fact, preclinical and clinical data have identified abnormalities in the tumor microenvironment (TME) that can thwart the efficacy of immunotherapies such as ICBs. Here, we will discuss how reprogramming various facets of the TME (blood vessels, myeloid cells, and regulatory T cells [Tregs]) may overcome TME-instigated resistance mechanisms to immunotherapy. We will discuss clinical applications of this strategic approach, including the recent successful phase III trial combining bevacizumab with atezolizumab and chemotherapy for metastatic nonsquamous non-small cell lung cancer that led to rapid approval by the U.S. Food and Drug Administration of this regimen for first-line treatment. Given the accelerated testing and approval of ICBs combined with various targeted therapies in larger numbers of patients with cancer, we will discuss how these concepts and approaches can be incorporated into clinical practice to improve immunotherapy outcomes.

Poor Response to Neoadjuvant Chemotherapy Correlates with Mast Cell Infiltration in Inflammatory Breast Cancer

Our understanding is limited concerning the tumor immune microenvironment of inflammatory breast cancer (IBC), an aggressive form of primary cancer with low rates of pathologic complete response to current neoadjuvant chemotherapy (NAC) regimens. We retrospectively identified pretreatment (N = 86) and matched posttreatment tissue (N = 27) from patients with stage III or de novo stage IV IBC who received NAC followed by a mastectomy. Immune profiling was performed including quantification of lymphoid and myeloid infiltrates by IHC and T-cell repertoire analysis. Thirty-four of 86 cases in this cohort (39.5%) achieved a pathologic complete response. Characterization of the tumor microenvironment revealed that having a lower pretreatment mast cell density was significantly associated with achieving a pathologic complete response to NAC (P = 0.004), with responders also having more stromal tumor-infiltrating lymphocytes (P = 0.035), CD8⁺ T cells (P = 0.047), and CD20⁺ B cells (P = 0.054). Spatial analysis showed close proximity of mast cells to CD8⁺ T cells, CD163⁺ monocytes/macrophages, and tumor cells when pathologic complete response was not achieved. PD-L1 positivity on tumor cells was found in fewer than 2% of cases and on immune cells in 27% of cases, but with no correlation to response. Our results highlight the strong association of mast cell infiltration with poor response to NAC, suggesting a mechanism of treatment resistance and a potential therapeutic target in IBC. Proximity of mast cells to immune and tumor cells may suggest immunosuppressive or tumor-promoting interactions of these mast cells.

Human Tumor-Associated Macrophage and Monocyte Transcriptional Landscapes Reveal Cancer-Specific Reprogramming, Biomarkers, and Therapeutic Targets

The roles of tumor-associated macrophages (TAMs) and circulating monocytes in human cancer are poorly understood. Here, we show that monocyte subpopulation distribution and transcriptomes are significantly altered by the presence of endometrial and breast cancer. Furthermore, TAMs from endometrial and breast cancers are transcriptionally distinct from monocytes and their respective tissue-resident macrophages. We identified a breast TAM signature that is highly enriched in aggressive breast cancer subtypes and associated with shorter disease-specific survival. We also identified an auto-regulatory loop between TAMs and cancer cells driven by tumor necrosis factor alpha involving SIGLEC1 and CCL8, which is self-reinforcing through the production of CSF1. Together these data provide direct evidence that monocyte and macrophage transcriptional landscapes are perturbed by cancer, reflecting patient outcomes.

Tumor immune microenvironment characteristics of papillary thyroid carcinoma are associated with histopathological aggressiveness and BRAF mutation status

BACKGROUND

Papillary thyroid carcinoma (PTC) follows an indolent course; however, up to 30% of patients develop recurrent disease requiring further treatment. Profiling PTC immune complexity may provide new biomarkers for improved risk prediction.

METHODS

Immune complexity profiles were quantitatively evaluated by multiplex immunohistochemistry (mIHC) in archived tissue sections from 39 patients with PTC, and were assessed for correlations with aggressive histopathological features based on the presence of lymphovascular invasion and/or extrathyroidal extension, and BRAF V600E mutational status.

RESULTS

mIHC revealed two distinct immune clusters stratifying patients: a lymphoid-inflamed group (higher CD8⁺ T cells, reduced dendritic and mast cells) and a myeloid/hypo-inflamed group that correlated with aggressive pathological features. BRAF mutation was not associated with aggressive pathological features but did correlate with increased mast cell density.

CONCLUSIONS

Distinct immune microenvironments exist in PTC correlating with pathological aggressiveness. Immune-based biomarkers associated with possible tumor-immune interactions may be used for risk stratification.

Robust Cell Detection and Segmentation for Image Cytometry Reveal Th17 Cell Heterogeneity

Image cytometry enables quantitative cell characterization with preserved tissue architecture; thus, it has been highlighted in the advancement of multiplex immunohistochemistry (IHC) and digital image analysis in the context of immune-based biomarker monitoring associated with cancer immunotherapy. However, one of the challenges in the current image cytometry methodology is a technical limitation in the segmentation of nuclei and cellular components particularly in heterogeneously stained cancer tissue images. To improve the detection and specificity of single-cell segmentation in hematoxylin-stained images (which can be utilized for recently reported 12-biomarker chromogenic sequential multiplex IHC), we adapted a segmentation algorithm previously developed for hematoxlin and eosin-stained images, where morphological features are extracted based on Gabor-filtering, followed by stacking of image pixels into n-dimensional feature space and unsupervised clustering of individual pixels. Our proposed method showed improved sensitivity and specificity in comparison with standard segmentation methods. Replacing previously proposed methods with our method in multiplex IHC/image cytometry analysis, we observed higher detection of cell lineages including relatively rare T_H 17 cells, further enabling sub-population analysis into T_H 1-like and T_H 2-like phenotypes based on T-bet and GATA3 expression. Interestingly, predominance of T_H 2-like T_H 17 cells was associated with human papilloma virus (HPV)-negative status of oropharyngeal squamous cell carcinoma of head and neck, known as a poor-prognostic subtype in comparison with HPV-positive status. Furthermore, T_H 2-like T_H 17 cells in HPV-negative head and neck cancer tissues were spatiotemporally correlated with CD66b⁺ granulocytes, presumably associated with an immunosuppressive microenvironment. Our cell segmentation method for multiplex IHC/image cytometry potentially contributes to in-depth immune profiling and spatial association, leading to further tissue-based biomarker exploration. © 2019 International Society for Advancement of Cytometry.

Reprogramming the Tumor Microenvironment to Improve Immunotherapy: Emerging Strategies and Combination Therapies

Emerging immunotherapeutic approaches have revolutionized the treatment of multiple malignancies. Immune checkpoint blockers (ICBs) have enabled never-before-seen success rates in durable tumor control and enhanced survival benefit in patients with advanced cancers. However, this effect is not universal, resulting in responder and nonresponder populations not only between, but also within solid tumor types. Although ICBs are thought to be most effective against tumors with more genetic mutations and higher antigen loads, this is not always the case for all cancers or for all patients within a cancer subtype. Furthermore, debilitating and sometimes deadly immune-related adverse events (irAEs) have resulted from aberrant activation of T-cell responses following immunotherapy. Thus, we must identify new ways to overcome resistance to ICB-based immunotherapies and limit irAEs. In fact, preclinical and clinical data have identified abnormalities in the tumor microenvironment (TME) that can thwart the efficacy of immunotherapies such as ICBs. Here, we will discuss how reprogramming various facets of the TME (blood vessels, myeloid cells, and regulatory T cells [Tregs]) may overcome TME-instigated resistance mechanisms to immunotherapy. We will discuss clinical applications of this strategic approach, including the recent successful phase III trial combining bevacizumab with atezolizumab and chemotherapy for metastatic nonsquamous non-small cell lung cancer that led to rapid approval by the U.S. Food and Drug Administration of this regimen for first-line treatment. Given the accelerated testing and approval of ICBs combined with various targeted therapies in larger numbers of patients with cancer, we will discuss how these concepts and approaches can be incorporated into clinical practice to improve immunotherapy outcomes.

Complement C5a Fosters Squamous Carcinogenesis and Limits T Cell Response to Chemotherapy

Complement is a critical component of humoral immunity implicated in cancer development; however, its biological contributions to tumorigenesis remain poorly understood. Using the K14-HPV16 transgenic mouse model of squamous carcinogenesis, we report that urokinase (uPA)+ macrophages regulate C3-independent release of C5a during premalignant progression, which in turn regulates protumorigenic properties of C5aR1+ mast cells and macrophages, including suppression of CD8+ T cell cytotoxicity. Therapeutic inhibition of C5aR1 via the peptide antagonist PMX-53 improved efficacy of paclitaxel chemotherapy associated with increased presence and cytotoxic properties of CXCR3+ effector memory CD8+ T cells in carcinomas, dependent on both macrophage transcriptional programming and IFNγ. Together, these data identify C5aR1-dependent signaling as an important immunomodulatory program in neoplastic tissue tractable for combinatorial cancer immunotherapy.

Ibuprofen supports macrophage differentiation, T cell recruitment, and tumor suppression in a model of postpartum breast cancer

BACKGROUND

Women diagnosed with breast cancer within 5 years postpartum (PPBC) have poorer prognosis than age matched nulliparous women, even after controlling for clinical variables known to impact disease outcomes. Through rodent modeling, the poor prognosis of PPBC has been attributed to physiologic mammary gland involution, which shapes a tumor promotional microenvironment through induction of wound-healing-like programs including myeloid cell recruitment. Previous studies utilizing immune compromised mice have shown that blocking prostaglandin synthesis reduces PPBC tumor progression in a tumor cell extrinsic manner. Given the reported roles of prostaglandins in myeloid and T cell biology, and the established importance of these immune cell populations in dictating tumor growth, we investigate the impact of involution on shaping the tumor immune milieu and its mitigation by ibuprofen in immune competent hosts.

METHODS

In a syngeneic (D2A1) orthotopic Balb/c mouse model of PPBC, we characterized the impact of mammary gland involution and ibuprofen treatment on the immune milieu in tumors and draining lymph nodes utilizing flow cytometry, multiplex IHC, lipid mass spectroscopy and cytokine arrays. To further investigate the impact of ibuprofen on programming myeloid cell populations, we performed RNA-Seq on in vivo derived mammary myeloid cells from ibuprofen treated and untreated involution group mice. Further, we examined direct effects of ibuprofen through in vitro bone marrow derived myeloid cell cultures.

RESULTS

Tumors implanted into the mammary involution microenvironment grow more rapidly and display a distinct immune milieu compared to tumors implanted into glands of nulliparous mice. This milieu is characterized by increased presence of immature monocytes and reduced numbers of T cells and is reversed upon ibuprofen treatment. Further, ibuprofen treatment enhances Th1 associated cytokines as well as promotes tumor border accumulation of T cells. Safety studies demonstrate ibuprofen does not impede gland involution, impact subsequent reproductive success, nor promote auto-reactivity as detected through auto-antibody and naïve T cell priming assays.

CONCLUSIONS

Ibuprofen administration during the tumor promotional microenvironment of the involuting mammary gland reduces overall tumor growth and enhances anti-tumor immune characteristics while avoiding adverse autoimmune reactions. In sum, these studies implicate beneficial prophylactic use of ibuprofen during the pro-tumorigenic window of mammary gland involution.