Abstract 86: Chemotherapy-induced microenvironmental changes promote dormant breast cancer cell outgrowth in adipose tissue

Abstract Despite the high 5-year survival rate for early-stage breast cancer patients, late recurrence of the disease remains a major challenge. Breast cancer can recur in approximately 20-25% of patients months to decades after an initial diagnosis, and there are few biomarkers that predict which patients will suffer from the recurrent disease. Unfortunately, this means clinicians and their patients must take a frustrating wait-and-see approach. Notably, disseminated tumor cells (DTCs) are frequently detected in early-stage breast cancer patients, and their presence predicts a higher chance of recurrence. However, why some patients with DTCs recur while others do not remains a mystery. Previous work has suggested that changes in the tumor microenvironment (TME) play an important role in the maintenance of tumor cell dormancy. When assessing the impact of doxorubicin (DOXO), a chemotherapeutic agent often used to treat breast cancer patients, on the TME, we noted that DOXO treatment led to the activation of dormant breast cancer cells in the visceral adipose tissue. Moreover, in accordance with the clinical observation that obese patients suffer a higher risk of cancer recurrence, we found that diet-induced obesity further exacerbated DOXO ability to reactivate dormant breast cancer cells in adipose tissue and this reactivation was associated with robust macrophage infiltration. These findings were interesting in light of our observation that tumor cells can metastasize to visceral fat depots in breast cancer patients. To understand why macrophages were recruited to the adipose tissue and how they led to tumor cell reactivation, we profiled the microenvironmental changes in visceral fat from Veh- and Doxo- treated mice using single-cell RNA-sequencing and found that the infiltrating macrophages exhibited unique pro-inflammatory and lipid-regulatory phenotypes. Our study provides novel insights into how TME impacts breast cancer dormancy and also highlights the importance of adipose tissue as a unique reservoir that potentiates cancer relapse. Citation Format: Qihao Ren, Jiayu Ye, Xiaoyu Yuan, Sheila Stewart. Chemotherapy-induced microenvironmental changes promote dormant breast cancer cell outgrowth in adipose tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 86.