Abstract 6103: Reshaping the myeloid-dependent pro-tumorigenic microenvironment in PDAC by targeting the extracellular adenosine pathway: A therapeutic opportunity
Authors: Graziano Vincenzo , Dannhorn Andreas , Williamson Kate , Hulme Heather , Buckley Hannah , Lee Sheng Y. , Islam Sabita , Thaventhiran James E. , Goodwin Richard , Brais Rebecca , Dovedi Simon J. , Schuller Alwin , Eyles Jim , Jodrell Duncan I. 
Published: June 2022

Abstract
The prognosis for patients with pancreatic adenocarcinoma (PDAC) remains extremely poor. PDAC is resistant to both conventional therapies and emerging immunotherapies (IOT), apart from tumors with mismatch repair deficiency. This may be explained in part by its low tumor mutational burden (TMB) but also by its immunosuppressive tumor microenvironment (TME). It has been suggested that CD73, a member of the adenosine pathway, expressed on cancer cells contributes to immune escape and resistance to cytotoxic/radiotherapy treatment. The adenosine pathway converts the immune activator ATP, released by dying cells during cell turnover or after treatment, to extracellular Adenosine (eAdo), which is immunosuppressive.
Using syngeneic, in vivo models by s.c. implantation of KPC-derived cell lines (courtesy of Ben Stanger, UPenn) with differential immune infiltration and response to IOT [resistant (IOTResi) or responsive (IOTResp)], we showed by flow cytometry that the adenosine pathway is enriched in the tumor-infiltrating immune cells (in particular myeloid populations) which co-express CD39 and CD73, enabling the formation of eAdo. Mass Spec Imaging (MSI) revealed that adenosine distribution is heterogeneous in the tumors with high concentrations in the hypoxic margins that surround necrotic areas. Subpopulations of myeloid cells infiltrating the lesions are a target for eAdo, expressing high levels of adenosine receptor Adora2a. We discovered that pro-tumorigenic M2 macrophages have the highest expression of the receptor and significantly higher in the IOTResi model. Blocking the in vivo formation and function of eAdo in IOTResi tumors, using a combination of anti-CD73 antibody (2C5, murine IgG1-Fc) and an inhibitor of Adora2a (AZD4635) reduced the presence of eAdo, slowed tumor growth and reduced the lung metastatic burden. The combination remodeled the TME, reducing the infiltration by M2 macrophages, particularly those that are PD-L1 positive and diminished the frequency of infiltrating Tregs. Bulk RNAseq analysis demonstrated a profound dependency of the TME on the presence of eAdo. Genes related to cytokine/chemokine signaling, immunosuppression/inflammation, hypoxia, metastasis and collagen production are strongly downregulated following administration of anti-CD73Ab/Adora2ai. In addition, blocking the adenosine pathway improved the efficacy of combinations of cytotoxics (gemcitabine/ATR inhibitor) and immunotherapy (aCD40/anti-PDL1Ab).
The formation of eAdo appears to be a factor in the development of the immunosuppressive TME in PDAC, contributing to its resistance to conventional and novel therapies. Therefore, inhibition of the adenosine pathway using a CD73Ab and an Adora2ai may represent a strategy to modulate the PDAC stroma and improve therapy response in patients with PDAC.
Citation Format: Vincenzo Graziano, Andreas Dannhorn, Kate Williamson, Heather Hulme, Hannah Buckley, Sheng Y. Lee, Sabita Islam, James E. Thaventhiran, Richard Goodwin, Rebecca Brais, Simon J. Dovedi, Alwin Schuller, Jim Eyles, Duncan I. Jodrell. Reshaping the myeloid-dependent pro-tumorigenic microenvironment in PDAC by targeting the extracellular adenosine pathway: A therapeutic opportunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6103.