Abstract B024: A histological data-driven analysis of the hypoxic microenvironment of preclinical murine bladder tumors
Authors: Ojwang Awino Maureiq E. , Hu Anjun , Williams McKenzie , Bazargan Sarah , Johnson Joseph O. , Pilon-Thomas Shari , Rejniak Katarzyna A. 
Published: February 2024

Abstract
Hypoxia is common in many solid tumors, including bladder cancer (BC). Preclinical murine models that mimic relevant molecular and phenotypical characteristics of clinical BC were used to analyze the immune cell composition within the hypoxic tumor microenvironment. The experimental protocols involve intravesical installations, adoptively transferred T cells, and chemotherapy and were designed to recreate therapeutic procedures used in a recently open feasibility clinical trial of intravesical adoptive cell therapy (ACT) for BC patients. We analyzed 18 murine BC tissues from a treatment protocol that included intravesical installment of MB49-OVA tumor cells on day 0, gemcitabine treatment on day 10, and/or intravesical transfer of OT-I transgenic T cells on day 14, in addition to untreated controls and normal bladder tissues. The OT-I cells mimic the T cells used in clinical ACT. The collected tissues were sliced, and consecutive sections were stained for vasculature, tumor, and immune cells: CD8+, CD4+, and myeloid-derived suppressor cells (MDSCs). Subsequently, these histology images were co-registered, segmented, and preprocessed to identify the tumor boundaries, select viable vasculature, resolve cell overlaps, and annotate bladder cavities. A multi-cell off-lattice hybrid agent-based model that combines discrete cells and vasculature with continuous oxygen kinetics was developed to recreate the differential oxygenation in the tumor microenvironment. In all tissues, the hypoxic microenvironment was more prevalent in the tumor regions than in the nontumor regions due to differences between the irregular tumor vasculature vs. normal vasculature. The T cell and MDSC infiltration was increased in the tumors treated with gemcitabine (as mono- or combination therapy). Despite the significant hypoxia level in these tumors, only small proportions of CD8+s and CD4+s were hypoxic, as the majority resided in the well-oxygenated portions of the tumor. High infiltration of CD8+ cells was observed in tumors treated with OT-I cells compared to the controls. However, only a small proportion were hypoxic, and most CD8+s and MDSCs were well-oxygenated. The CD8+s were located far from the intravesical source, with some cells near the vasculature. Hypoxic native CD8+s in untreated tissues were observed inside the tumors, and most well-oxygenated CD8+s were near the tumor borders. The CD8+s also resided in the well-oxygenated regions in the normal tissues. Our reconstructed tissue oxygenation based on histology images revealed that the hypoxic tumor microenvironment hinders T cell accumulation in treated and untreated tumors. Such quantitative analyses may encourage designing more effective hypoxia-mediated therapies.
Citation Format: Awino Maureiq E. Ojwang, Anjun Hu, McKenzie Williams, Sarah Bazargan, Joseph O. Johnson, Shari Pilon-Thomas, Katarzyna A. Rejniak. A histological data-driven analysis of the hypoxic microenvironment of preclinical murine bladder tumors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Cancer Evolution and Data Science: The Next Frontier; 2023 Dec 3-6; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_2):Abstract nr B024.