Novel Molecular Insight into the ESR1 Mutant/Adipocytes Crosstalk: a Pivotal Contribute of IGF1‐R
Authors: Caruso Amanda , Gelsomino Luca , Panza Salvatore , Gu Guowei , Giordano Cinzia , Barone Ines , Malivindi Rocco , Bonofiglio Daniela , Catalano Stefania , Fuqua Suzanne , Andò Sebastiano 
Published: May 2022

BackgroundObesity is considered a global epidemic and an important public health concerns worldwide. This medical condition is also recognized a risk factor for various diseases, including cancers. Epidemiological studies have reported a higher risk of breast cancer (BC) in obese women compared to normal‐weight ones. In fact, obesity may sustain BC development and progression and also, is considered a heavyweight player driving endocrine resistance. Adipocyte secretome‐factors, insulin resistance, hyper activation of insulin‐like growth factor (IGF‐1/IGF‐1R) pathways, and increased levels of estrogen are the mechanisms through which obesity impacts BC biology but there is a huge knowledge gap on the obesity/acquired endocrine resistance relationship. ESR1 mutations (ESR1m), mainly found in metastatic tumors, contribute to the acquired resistance through documented IGF‐1R signaling pathway altered activation. Thus, we evaluated the effects of adipocytes in influencing the behavior of BC cell expressing the most frequent ESR1m, Y537S, wherein the specific role of IGF‐1/IGF‐1R axis will be investigated.MethodsWe employed CRISPR/Cas9‐engineered human breast cancer cells (MCF‐7) and murine‐derived cells (mMTC2) to express Y537S mutation and 3T3‐L1 as adipocyte‐like cells. As ex vivo model we used human adipocytes (hAdipo) isolated from mammary adipose tissue biopsies of healthy women with varying body mass index. We performed co‐culture experiments testing the effects of adipocytes on BC cell behaviour in the presence or not of a specific IGF1R inhibitor, the GSK1838705A.ResultsConditioned media (CM) derived from mature adipocytes (3T3L1‐A) impacts BC cells behavior by enhancing growth, migration and invasion of MCF‐7 and mMCT2, but in a higher extent in the Y537S mutant clones. The latter effects appear to be amplified upon the treatment with CM derived from ex vivo model of hAdipo. In line with these data, microarray analysis evidenced that mutant BC cells exhibited higher mRNA levels of many essential mediators of tumor‐stroma interplay compared to parental cells. Among them, the most significant up‐regulated gene was IGF‐1R. These data have been confirmed by qRT‐PCR. Remarkably, the treatment with GSK1838705A reversed the enhanced growth, migration and invasion only in mutant cells. These data highlight the pivotal role of IGF‐1R axis in the ESR1m cells/tumor microenvironment interactions.ConclusionsOur data clearly demonstrated that adipocytes, the major compartment of tumor stroma, further sustain the aggressive malignant phenotype of mutant cells, mainly involving IGF‐1R signaling pathway. Prospectively our findings address the use of an IGF‐1R inhibitor to block the mutant/stroma cells interplay. In the era of precision medicine, the use of a specific IGF1R inhibitor may help to improve the outcome of BC patients expressing the ESR1 mutations, particularly in obese setting.