Abstract B082: A pro-tumorigenic, aged microenvironment may aid in worsened disease progression in an HGSOC model

Abstract Over 70% of HGSOC patients are diagnosed after 55 and the average patient succumbs to disease at 70 years old. Despite this, most ovarian cancer research, and cancer studies generally, utilize young mice that are mimetic of human teenagers and/or do not investigate age as a variable despite it being the top cancer risk factor. An improved understanding of how age affects HGSOC progression may enable development of alternative treatment strategies aimed at intercepting metastasis and preventing cancer cells from establishing in the peritoneum. Our preliminary studies show tumor burden and disease severity are significantly higher in aged versus young animals. We developed an epithelial cell line derived from C57Bl/6 oviducts and used CRISPR-Cas9 genome editing to develop a syngeneic tumorigenic line harboring Trp53, Pten, and Brca2 deletions. After intraperitoneal injection into 6-week and 14-month-old immunocompetent C57Bl/6 mice, we observed a stark increase in tumor burden in aged mice. Furthermore, older mice died at a faster rate; all aged mice succumbed to disease within 1-month of inoculation compared to young mice surviving up to 3 months. Total RNA-sequencing of tumors harvested from aged and young mice is ongoing. Characterization of the tumor-naïve peritoneal compartment revealed the aged microenvironment to be highly inflammatory. When assessed via cytokine array, peritoneal fluid of aged mice had higher concentrations of inflammatory markers including soluble TNF receptor-1 (sTNFR-1), L-selectin, and VCAM-1. Flow cytometry of peritoneal lavage indicated an over 2-fold increase in the number CD45+ cells present in the peritoneal cavity, coinciding with cytokine array results. Within this population, there was nearly complete depletion of macrophage and neutrophil populations and a significant increase in B cells and CD4+ and CD8+ T cells. The percentage of PD-1+ CD8+ cells also increased. In addition to increased signs of inflammation, a significantly higher concentration of insulin-like growth factor-1 (IGF-I) and higher concentrations of the associated IGF binding proteins -3 and -6 were found in peritoneal fluid of aged mice. In addition, during tissue collection, organs of the aged mice were found to be much larger than young mice, a common effect of elevated IGF-I; aged omentum weighed 2-4 times that of young. Notably, IGF-I is known to inhibit apoptosis and promote proliferation and increased IGF-I is correlated with increased risk of breast, prostate, and lung cancer. A drastic difference in disease severity occurs when identical cancer cells are injected into 6-week and 14-month-old mice. To identify possible microenvironmental differences in the two populations, a broad panel of cytokines was assessed, and immune populations were quantified in pre-cancerous mice. Overall, multiple pro-inflammatory markers and the number of lymphocytes were upregulated in the aged peritoneal cavity, and markers of immune fatigue were present. Further work is aimed at identifying immune cell state via further cytometry and sequencing. Citation Format: Katherine A. Cummins, Ronny I. Drapkin, Matthew Knarr. A pro-tumorigenic, aged microenvironment may aid in worsened disease progression in an HGSOC model abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B082.