Abstract 2053: Phenotypic and functional analyses of response of lung tumor-associated myeloid cells to systemic oncolytic virotherapy
Authors: Atasheva Svetlana , Yao Jia , Shayakhmetov Dmitry 
Published: June 2022

Abstract
Introduction: Oncolytic virotherapy represents a promising cancer treatment modality. One of the appeals of oncolytic virotherapy approaches is the capacity of viruses to change tumor microenvironment, frequently interpreted as de-polarization of tumor-associated macrophages (TAMs) from highly pro-tumorigenic to less pro-tumorigenic phenotypes. The goal of this study was to analyze how systemic therapy with oncolytic adenovirus AVID-317 modulates complexity, phenotypes, and pro-tumorigenic function of tumor-associated myeloid cells in a mouse model of orthotopic metastatic lung cancer.
Methods: We utilized single cell RNAseq and a 37-marker mass-cytometry (Cy-TOF) analyses to explore phenotypic and functional states of distinct myeloid cell populations in the lungs of tumor-bearing mice before and after virotherapy. We further performed correlation analyses to reveal functional contribution of each identified myeloid cell population to tumor control or tumor progression after virotherapy on a large groups of mice treated with the virus (N=43) or buffer (N=23).
Summary of the results: Our phenotypic immunoprofiling identified 13 discrete TAM and DCs cell populations and 5 discrete populations of granulocytic cells, which were present in the lungs of lung tumor-bearing mice prior to virotherapy treatment. We found that in all TAM populations, the expression of CD274, ARG1, IL-10, and surprisingly, CD127 correlated with a higher tumor burden. In 7 out of 13 TAM populations, virotherapy further increased the expression of these pro-tumorigenic markers. Moreover, virotherapy led to a significant increase in the abundance of TAMs that correlated with tumor burden increase. In addition, in response to virotherapy, TAMs increased the expression of pro-tumorigenic growth factors. These data indicate the virotherapy indeed activated TAMs but did not trigger their de-polarization to lesser pro-tumorigenic phenotypes. To find whether virus-induced tumor cell death may drive TAM activation, we next treated tumor-bearing mice with a UV-inactivated AVID-317 virus that lacks the capacity of killing tumor cells. Our analyses confirmed that virus-mediated tumor cells death but not the exposure of TAMs to the virus drives TAM activation.
Conclusion: Our analyses showed that oncolytic virotherapy activates TAMs, which in response produce pro-tumorigenic growth factors that may promote tumor progression. Our findings do not support the universal assumption of de-polarization of TAMs to a lesser pro-tumorigenic phenotypes in response to oncolytic virotherapy. The clinical success of oncolytic virotherapy will require careful consideration of the TAM activation in response to virotherapy and finding effective drug combinations to suppress pro-tumorigenic function of myeloid cells prior to administration of viruses with potent anti-tumor activity.
Citation Format: Svetlana Atasheva, Jia Yao, Dmitry Shayakhmetov. Phenotypic and functional analyses of response of lung tumor-associated myeloid cells to systemic oncolytic virotherapy [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 2053.