Abstract 5297: ONC201 suppresses cancer cell growth in a reconstructed tumor microenvironment that includes chemotherapy-induced senescent fibroblasts

Abstract Cellular senescence and its associated secretory phenotype (SASP) can promote cancer progression in the tumor microenvironment (TME). The TME includes tumor cells, stromal cells, immune cells, endothelial cells, and extracellular matrix. Senescent cancer-associated fibroblasts (CAF) may contribute to tumor growth and therapy resistance. Targeting senescent CAF by means of removal, modulation of the SASP, or through cellular reprogramming might provide therapeutic avenues for treating cancer. We investigated the impact of chemotherapy-induced fibroblast senescence in the TME on tumor growth and response to cancer therapy. Expression of cytokines in chemo-induced senescent fibroblasts and cancer cells was assessed by bulk and single cell cytokine profiling. As expected, there were alterations in SASP factors with increased pro-tumorigenic immune factors and decreased anti-tumor cytokines during IMR90 etoposide-induced fibroblast senescence. We co-cultured luciferase-labeled HT29 cancer cells with senescent IMR90 and found that the senescent fibroblasts promoted HT29 cell growth in culture and accelerated xenograft tumor formation in mice. We next inhibited cellular senescence and its SASP with the senolytic drug ABT263 or the senostatic/senomorphic drug lamivudine (3TC). Both ABT263 and 3TC significantly reduced bioluminescence of HT29-Luc cells co-cultured with senescent IMR90 compared to non-treated IMR90 cells. Therapy-induced senescence confers 5-Fluorouracil (5-FU) resistance in colorectal cancer. We found that 5-FU treatment significantly reduced colony formation of HT29 cells in the presence of proliferating or senescent IMR90 cells, with a lesser reduction in the presence of the senescent IMR90 cells. This suggests that a microenvironment that includes senescent cells promotes tumor cell resistance to 5-FU. We hypothesize that SASP factors might confer cancer cell resistance to 5-FU treatment. Cytokine profiling showed that TRAIL expression is reduced in senescent cells. Treatment with the TRAIL-inducer ONC201 reduced colony formation and cell viability of HT29 cells co-cultured with senescent IMR90 fibroblasts. Single-cell cytokine profiling showed subpopulations of cancer cells with increased polyfunctionality strength index (PSI, secretion of more than 2 dominant types of cytokines per cell in a population). Combined treatment with ABT263 and ONC201 synergically reduced viability HT29 cells co-cultured with senescent IMR90, and this correlated with reduced PSI. Our results indicate that TME targeting by increasing antitumor cytokines in conjunction with senolytic therapies can inhibit tumor growth. We are continuing to unravel the cytokine landscape of chemotherapy-induced cell senescence to gain insights into therapeutic strategies targeting chemotherapy-induced TME-senescence and drug resistance. Citation Format: Shengliang Zhang, Kelsey E. Huntington, Bianca Kun, Lanlan Zhou, Jill Kreiling, John M. Sedivy, Wafik S. El-Deiry. ONC201 suppresses cancer cell growth in a reconstructed tumor microenvironment that includes chemotherapy-induced senescent fibroblasts [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 5297.