Abstract 2019: Primary cancer associated fibroblasts increase the chemoresistance of triple negative breast cancer cells by mitochondria metabolic upregulation

Abstract Breast cancers (BCs) are the most prevalent cancers occurring in women. Tumor reoccurrence attributed to chemotherapy resistance remains a main challenge in fighting disease relapse. Cancer associated fibroblasts (CAFs) are the most prominent component of the tumor microenvironment (TME) and have already been implicated in therapy resistances. Although the exact molecular mechanisms behind this resistance remain unclear. In this regard, we recently identified 4 CAF populations (S1-S4) in ovarian and BCs, and showed that only CAF-S1 promote immunotherapy resistance as well as metastasis. Based on these observations, we are now investigating the impact of CAF-S1 on the chemotherapy response of BCs. To study the interactions between CAF-S1 and BC cells, we developed a tumor on chip (ToC) device, mimicking the TME in 3D. Using ToC live imaging, we show that primary CAF-S1 mediate a chemoprotective effect over luminal and triple negative BC (TNBC) cells by significantly decreasing their apoptosis rate as early as 10h after Doxorubicin and 40h after Paclitaxel treatment. Interestingly, CAF-S1 display a highly heterogenous response to Doxorubicin, allowing the classification into chemo-sensitive and -resistant CAF-S1. Regardless of premature CAF-S1 cell death, the chemoprotective effect over BC cells is maintained for at least 3 days. This indicates a crucial CAF-S1 - cancer cell cross talk at early timepoints. Additionally, by applying machine learning algorithms on live imaging videos, we demonstrate that physical proximity of CAF-S1 to BC cells immediately after treatment initiation correlates with BC cell survival, even after several days of treatment. This again implies cancer cell priming by CAF-S1 as a possible mechanism of chemotherapy resistance. To investigate this molecular interplay further, we performed scRNA-seq of ToC extracted and treatment naïve CAF-S1 and TNBC cells as well as bulk RNA-seq of patient derived TNBC tumors before/after chemotherapy treatment. We identify mitochondrial metabolic pathways to be upregulated in TNBC cells after CAF-S1 co-culture inside ToC devices and in TNBC cells of chemo-resistant patients enriched in CAF-S1 at baseline. We are now validating the impact of target gene knock downs on the survival of TNBC cells in CAF-S1 co-cultures after chemotherapy treatment on chip. Overall, these results provide insights into molecular mechanisms by which CAF-S1 promote chemotherapy resistance of breast cancers. Citation Format: Isabella Hofer, Arianna Mencattini, Yann Kieffer, Eugenio Martinelli, Maria Carla Parrini, Fatima Mechta-Grigoriou. Primary cancer associated fibroblasts increase the chemoresistance of triple negative breast cancer cells by mitochondria metabolic upregulation 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 (6Suppl): Abstract nr 2019.