Abstract PR017: Stromal Netrin G1 ligand (NGL-1): A new modulator of tumorigenesis and immunosuppression in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is soon to be the second deadliest types of cancer, with a 5-year survival of only 10%. The unique features of PDAC are the expansion of cancer-associated fibroblasts (CAFs), presence of a dense fibrous stroma with high bundled collagen I and immunosuppression, representing a challenge for therapies. Ways to overcome these unique pro-tumor features will be key for the development of better therapeutic strategies for PDAC. Herein we report that, in addition to the identified ectopic expression of NGL-1 in PDAC cells, it is also expressed in the stroma (CAFs and immune cells) of PDAC patients, inversely correlating with overall survival. Stromal NGL-1 was important for tumorigenesis in vivo, as NGL-1 knockout mice (KO) orthotopically allografted with pancreatic cancer cells presented less tumor burden. Further analysis showed that the tumors from KO mice presented more CD8+ T cells and less immunosuppressive cytokines, such as TGFβ. Single cell RNAseq analysis of these tumors showed decreased expression of pro-tumor factors, such as immune checkpoint molecules in T cells and TGFβ related genes across different cellular compartments (epithelial, immune and fibroblasts). In accordance with these results, these tumors presented a limited amount of desmoplastic bundled collagen, suggestive of a TGFβ-deficient environment. In order to further dissect between the NGL-1-dependent contributions of immune vs. local stroma (e.g., CAFs) cells, we generated bone marrow chimeras and performed orthotopic injections to generate tumors. The loss of NGL-1 in each cellular compartment alone failed to phenocopy the full body loss of NGL-1, suggesting that NGL-1 in both immune cells and local stromal are important for tumorigenesis. Functionally, NGL-1 deficient CAFs failed to support the survival of starved PDAC cells in vitro, downregulated important myofibroblastic molecules such as p-smad, and produced less immunosuppressive cytokines, suggesting a role for NGL-1 in key pro-tumor features of CAFs. In fact, the fibroblastic NGL-1 dependent immunomodulatory effects were confirmed with human CD8+ T cells from healthy donors, which lost their cytotoxic profile in the presence of conditioned media (CM) from NGL-1+ CAFs, but were able to keep this profile when exposed to CM from NGL-1 deficient CAFs. Bone marrow derived macrophages from KO mice produced less pro-tumor cytokines and CD8+ T cells lacking NGL-1 proliferated more than those from wild type animals, when stimulated in vitro. Mechanistically, while immune cells and CAFs deficient in NGL-1 are both tumor suppressive, the latter can regain pro-tumor functions in response to TGFβ, explaining the need for a global modulation of NGL-1 expression for an anti-tumor effect. Finally, NGL-1 KO mice orthotopically allografted with PDAC cells responded better (smaller tumors) to chemotherapeutical regimen (FOLFIRINOX) compared to WT animals. All these results point to NGL-1 as a potential new target to modulate immunosuppression and tumorigenesis in pancreatic cancer.

Citation Format: Debora Barbosa Vendramini Costa, Ralph Francescone, Janusz Franco-Barraza, Tiffany Luong, Esteban Martinez, Stephen Sykes, Nina Steele, Marina Pasca di Magliano, Dmitry Zhigarev, Charline Ogier, Huamin Wang, Igor Astsaturov, Kerry Campbell, Edna Cukierman. Stromal Netrin G1 ligand (NGL-1): A new modulator of tumorigenesis and immunosuppression in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR017.

IL27 Signaling Serves as an Immunologic Checkpoint for Innate Cytotoxic Cells to Promote Hepatocellular Carcinoma

Although inflammatory mechanisms driving hepatocellular carcinoma (HCC) have been proposed, the regulators of anticancer immunity in HCC remain poorly understood. We found that IL27 receptor (IL27R) signaling promotes HCC development in vivo. High IL27EBI3 cytokine or IL27RA expression correlated with poor prognosis for patients with HCC. Loss of IL27R suppressed HCC in vivo in two different models of hepatocarcinogenesis. Mechanistically, IL27R sig-naling within the tumor microenvironment restrains the cytotoxicity of innate cytotoxic lymphocytes. IL27R ablation enhanced their accumulation and activation, whereas depletion or functional impairment of innate cytotoxic cells abrogated the effect of IL27R disruption. Pharmacologic neutralization of IL27 signaling increased infiltration of innate cytotoxic lymphocytes with upregulated cytotoxic molecules and reduced HCC development. Our data reveal an unexpected role of IL27R signaling as an immunologic checkpoint regulating innate cytotoxic lymphocytes and promoting HCC of different etiologies, thus indicating a therapeutic potential for IL27 pathway blockade in HCC.

SIGNIFICANCE

HCC, the most common form of liver cancer, is characterized by a poor survival rate and limited treatment options. The discovery of a novel IL27-dependent mechanism controlling anticancer cytotoxic immune response will pave the road for new treatment options for this devastating disease. This article is highlighted in the In This Issue feature, p. 1825.

Lymphocyte Exhaustion in AML Patients and Impacts of HMA/Venetoclax or Intensive Chemotherapy on Their Biology

Simple Summary

Patients with acute myeloid leukemia (AML) are routinely treated with either intensive chemotherapy or DNA hypomethylating agents (HMA) in combination with the Bcl-2 inhibitor, venetoclax. While both treatment regimens are highly cytotoxic to the aggressive AML tumor cells, they are also toxic to immune cells. Therefore, we sought to establish the detrimental impacts of these therapies on lymphocytes and their recovery over time in AML patients. Even prior to treatment initiation, the patients were found to have exhausted lymphocytes in peripheral blood, and additional signs of exhaustion were noted after treatment with HMA/venetoclax. In fact, the lymphocytes were still suppressed for two to three months after the initiation of induction therapy. Furthermore, T cells in a subset of patients subsequently found to be resistant to venetoclax therapy exhibited a higher expression of perforin and CD39 and more pronounced IFN-γ production.

Abstract

Acute myeloid leukemia (AML) is an aggressive malignancy that requires rapid treatment with chemotherapies to reduce tumor burden. However, these chemotherapies can compromise lymphocyte function, thereby hindering normal anti-tumor immune responses and likely limiting the efficacy of subsequent immunotherapy. To better understand these negative impacts, we assessed the immunological effects of standard-of-care AML therapies on lymphocyte phenotype and function over time. When compared to healthy donors, untreated AML patients showed evidence of lymphocyte activation and exhaustion and had more prevalent CD57⁺NKG2C⁺ adaptive NK cells, which was independent of human cytomegalovirus (HCMV) status. HMA/venetoclax treatment resulted in a greater fraction of T cells with effector memory phenotype, inhibited IFN-γ secretion by CD8⁺ T cells, upregulated perforin expression in NK cells, downregulated PD-1 and 2B4 expression on CD4⁺ T cells, and stimulated Treg proliferation and CTLA-4 expression. Additionally, we showed increased expression of perforin and CD39 and enhanced IFN-γ production by T cells from pre-treatment blood samples of venetoclax-resistant AML patients. Our results provide insight into the lymphocyte status in previously untreated AML patients and the effects of standard-of-care treatments on their biology and functions. We also found novel pre-treatment characteristics of T cells that could potentially predict venetoclax resistance.

671 Biological impacts of standard of care chemotherapies on immune effector cells from AML patients

Background

Acute myeloid leukemia (AML) is a heterogeneous group of malignant bone marrow diseases, characterized by massive and uncontrolled proliferation of myeloid precursor cells, which alters normal blood cell ratios. This disease is common to older adults and collectively displays one of the lowest 5-year overall survival rates (<25%) among all cancers, currently representing the deadliest form of leukemia. Improved treatments are clearly needed, and immunotherapies are attractive candidate therapies to explore.There are currently several standard chemotherapeutic treatment schemes for AML, which could be divided into two major groups: (1) cytotoxic chemotherapy (“7+3” or daunorubicin-cytarabine) and (2) hypomethylating agents (HMAs). HMAs include both 5-azacytidine and decitabine, which are cytidine analogs that inhibit DNA methyltransferase, resulting in the hypomethylation of DNA and inducing expression of silenced gene loci. Currently, HMAs are routinely delivered in combination with the Bcl-2 inhibitor venetoclax.The goals of this study are to determine how these standard first line therapies can affect the frequency and functional integrity of effector immune cells in patients' blood and establish when the phenotype and function of immune cells are restored to identify time windows when second line immunotherapies could be most effective.

Methods

More than 100 blood samples were obtained from 33 previously untreated AML patients. More than 50 measurable biomarkers were analyzed using 14-color flow cytometry to assess immune phenotypes of T and NK cells in peripheral blood of AML patients prior to treatment and at up to four timepoints after initiation of treatment with HMA or chemotherapy.

Results

We found several significant changes in immune cell phenotype and function that occur in response to these therapies. Treatment with HMAs was strikingly less impactful on immune cells in patients compared to previously published in vitro studies. Nevertheless, HMA treatment increased perforin levels in T and NK cells, inhibited IFN-gamma secretion by CD8+ T cells, and changed expression of several checkpoint molecules. While chemotherapy caused fewer phenotypic changes it dramatically decreased the total number of immune cells. We also determined viable, functional and phenotypical recovery periods for immune effector cells after the treatments.

Conclusions

Our results are important for introducing new second line immunotherapies to these chemotherapeutic regimens for treating AML and to improve overall understanding of immune cell behavior under conditions of anti-tumor treatment.

Acknowledgements

Supported by grants from Janssen and the U.S./Israel Binational Science Foundation.

Ethics Approval

The study was approved by the Fox Chase Cancer Center Institutional Review Board, approval number 17-8010, and all patients provided informed consent before taking part in the study.