Abstract 1565: Fat cells in breast cancer microenvironment: NCoA3 coactivator, a key molecule to understand adipocyte behavior
Authors: Lira Maria Cecilia , Rosa Francisco Damian , Aiello Ignacio , Machado Mileni Soares , Guemes Maria Cecilia Salazar , Paz Leonardo Agustin , Burlando Silvia , Azurmendi Pablo Javier , Paladino Natalia , Costas Monica Alejandra , Rubio Maria Fernanda 
Published: September 2020

Nuclear receptor Coactivator 3 (NCoA3) is a member of p160 family of transcriptional coactivators. It is present at low levels in normal cells and it is amplified or overexpressed in several types of cancer. Its oncogenic role is widely studied in breast tumors, however, its function is still unknown in the microenvironment. Adipocytes account for the largest proportion among the cells that comprise mammary gland and are considered to be a critical cell type in the tumor context of breast cancer. Since we have previously demonstrated that NCoA3 decreases during adipogenesis, we aimed to study its expression in cancer associated-adipocytes. Breast tumor-surrounding adipose tissue (AT) samples were collected from female postmenopausal patients (n=31). NCoA3 mRNA and protein levels were measured, which allowed us to classify samples as high and normal expression according to levels in non-tumoral AT. Regarding tumoral features, there were more AT samples with high NCoA3 levels from patients with triple negative tumors and thus a worse prognosis, than from patients with luminal tumors (p&lt;0.05). Concerning clinical stage, more stage III patients had NCoA3 overexpressed in AT than earlier stages (p&lt;0.05). As NCoA3 is a NF-κB coactivator, we studied the presence of its phosphorylated subunit p65 (p-p65) by immunohistochemistry as well as its target TNF by dot blot in conditioned media (CM) from AT samples. We observed an increased staining in adipocyte nuclei and an augmented TNF secretion in samples with high NCoA3 expression respect to those with normal levels (p&lt;0.05). Then, we studied the role of this coactivator in vitro stimulating 3T3-L1 derived-adipocytes with serum-free medium (basal), CM from non-tumoral (MCF10A) or tumoral (MDA-MB-231 and T47D) breast cell lines. NCoA3 expression resulted significantly higher in adipocytes stimulated with CM from T47D cells compared to the other conditions (p&lt;0.05). Moreover, anti-p-p65 immunofluorescence evidenced an augmented nuclear signal in adipocytes treated with CM from both tumoral cells. Interestingly, only adipocytes stimulated with CM from T47D cells secreted more TNF compared to other treatments (p&lt;0.05). The data obtained from patient samples indicate that aggressive tumors more frequently upregulate NCoA3 levels in adjacent AT which results in more nuclear p65 and TNF secreted. Accordingly, in vitro studies show that although both tumoral cell lines increase nuclear p65 in adipocytes, only T47D CM is capable to upregulate NCoA3 levels, which could explain a higher secretion of TNF. Remarkably, T47D line has higher NCoA3 and TNF levels than MDA-MB-231 cells and it is known that TNF upregulates NCoA3 expression via NF-κB. Altogether, these results suggest NCoA3 as a key factor to understand adipocyte behavior in the tumor context that could trigger changes in the adipokine secreted pattern.

Citation Format: Maria Cecilia Lira, Francisco Damian Rosa, Ignacio Aiello, Mileni Soares Machado, Maria Cecilia Salazar Guemes, Leonardo Agustin Paz, Silvia Burlando, Pablo Javier Azurmendi, Natalia Paladino, Monica Alejandra Costas, Maria Fernanda Rubio. Fat cells in breast cancer microenvironment: NCoA3 coactivator, a key molecule to understand adipocyte behavior [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1565.