Abstract PS16-36: Paracrine signalling with stromal fibroblasts drives recovery of cancer cells after chemotherapy treatment
Authors: Maia Ana , Gu Zuguang , Koch André , Berdiel-Acer Mireia , Will Rainer , Schlesner Matthias , Wiemann Stefan 
Published: February 2021

Abstract
Introduction: The main cause of death for cancer patients is the development of metastasis. These arise mainly due to irresponsiveness of cancer cells to the administered therapy, which then fails to eliminate all cancer cells present in the patient. To overcome this problem, it is essential to understand which mechanisms are involved in the lack of treatment response. We are investigating how the tumour microenvironment (TME) affects the response of cancer cells to chemotherapy (CTX) and how it can be modulated to improve the outcome of patients to therapy. Materials and Methods: Co-culture of chemotherapy-treated breast cancer cell lines with primary fibroblasts isolated from breast cancer patients was performed to investigate if fibroblasts affect the response of tumour cells to commonly used agents, such as epirubicin and paclitaxel. Recovery of cells was assessed using colony formation assays (CFA) and cell cycle profiling by EdU and the FUCCI system. To further explore the complex crosstalk between cancer cells and fibroblasts in the context of CTX, gene expression analysis of both cell types was done using next generation sequencing. Validation and evaluation of the biological impact of the identified pathways was done using RT-qPCR, western-blot and perturbation experiments. Lastly, publicly available datasets for breast cancer were used to investigate the clinical relevance of our findings. Results and Discussion: We show that cancer cells utilize paracrine signalling with stromal fibroblasts to drive their recovery after treatment withdrawal. Cell cycle analysis and RNA-sequencing revealed an increase in cell cycle re-entry of CTX-treated cancer cells in co-culture with fibroblasts. In addition, we have successfully shown that treated cancer cells upregulate an important secreted factor that modulates fibroblasts into a pro-tumorigenic state. Moreover, analysis of human breast carcinomas supported the proposed role of the identified factor since its expression is inversely correlated with recurrence free survival (RFS). Moreover, expression of the gene signature identified in stromal fibroblasts in co-culture with CTX-treated cancer cells was equally associated with higher recurrence rates and a worse outcome in breast cancer patients. Conclusion: CTX-induced secretory profile of cancer cells orchestrates the reprogramming of stromal fibroblasts into a pro-tumorigenic state, which drives the expansion of cancer cells. Our study unravels a novel paracrine communication between cancer cells and stromal fibroblasts that ultimately results in the escape of malignant cells to treatment, highlighting the importance of the TME in drug response. Targeting of this axis could potentially improve the outcome of breast cancer patients to CTX treatment.
Citation Format: Ana Maia, Zuguang Gu, André Koch, Mireia Berdiel-Acer, Rainer Will, Matthias Schlesner, Stefan Wiemann. Paracrine signalling with stromal fibroblasts drives recovery of cancer cells after chemotherapy treatment [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-36.