Abstract 2908: EDB+FN is an attractive therapeutic target in oncology: Insights from protein expression analysis of solid tumors

Abstract

Abstract Stroma plays a major role in the initiation, growth, survival, and drug-resistance of solid tumors, yet few therapeutics specifically target tumor-associated stroma. Extra-domain-B fibronectin (EDB+FN) is an oncofetal splice variant of fibronectin upregulated in solid tumor stroma, which is associated with tumor growth, angiogenesis, and metastases. Here we developed an immunohistochemistry (IHC) assay to assess EDB+FN protein expression in the stroma of tumor and normal tissues to characterize the potential of EDB+FN as a therapeutic target for solid tumors with high unmet need. We validated a primary detection antibody and titrated assay conditions to achieve specificity and a broad dynamic range of EDB+FN expression levels across indications, including thyroid cancer, head and neck squamous cell carcinoma, hepatocellular carcinoma, soft tissue sarcoma, pancreatic cancer, non-small cell lung cancer, ovarian cancer, and renal cancer. Considering the stroma-specific expression pattern of EDB+FN, we developed a scoring algorithm weighting both the intensity and distribution of EDB+FN expression specifically in the stroma compartment and separately in tumor cells. Using this assay and scoring approach, we screened more than 200 tumor samples from 10 solid tumor indications and found EDB+FN to be highly differentially expressed in tumor-associated stroma with little to no expression on tumor cells and trace to undetectable levels in healthy tissue. EDB+FN was expressed across the indications evaluated with a wide range of expression both within and between indications. Stromal EDB+FN expression was not correlated with stromal density, which also varied widely within and across indications. In parallel, we developed an algorithm using digital pathology to approximate pathologist scoring of stromal density and EDB+FN expression, allowing streamlined screening of preclinical samples for in vivo studies and indication selection. The disease-specific expression pattern of EDB+FN and high incidence of expression across indications make EDB+FN an ideal target for high-unmet-need solid tumors. The specificity and dynamic range of our IHC assay for detection of EDB+FN protein expression position it as a robust potential biomarker assay for EDB+FN-targeting therapeutics. Citation Format: Sara Lewandowski, Liyang Diao, Alyssa Quigley, Marsha Crochiere, Jan Pinkas. EDB+FN is an attractive therapeutic target in oncology: Insights from protein expression analysis of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2908.