Abstract 3024: Lipid treatment induces a neural-like phenotype in non-transformed breast epithelial cells
Authors: Eduardo Mariana Bustamante , Yadav Shivangi , Khan Seema , Clare Susan 
Published: June 2022

Introduction. Genes involved in lipid metabolism have been shown to be overexpressed in the contralateral unaffected breast of women with estrogen receptor negative (ER-) breast cancer (BC) (PMID: 28263391). Exposure of non-transformed MCF10A breast epithelial cells to lipids results in altered chromatin structure, epigenomic reprogramming and changes in gene expression. Within the upregulated genes are numerous gene sets related to nervous system development, neurons and synapses. Neural genes are more highly expressed in Triple Negative Breast Cancers (TNBC) compared to non-TNBC, and several studies have shown a connection between neural stemness and tumorigenicity. We hypothesized that stem-like cells have a survival advantage when exposed to lipids and that lipid-induced molecular changes underlying malignant transformation are connected with a neural-like phenotype.

Methods. To validate the association of lipids and neural genes, a second non-transformed, estrogen and progesterone receptor negative breast epithelial cell line, MCF12A, was exposed to vehicle or octanoic acid (OA) for 24 hours. Gene expression was assayed by RNA-seq and OA responsive genes were identified. Gene set enrichment analysis was utilized to identify gene sets affected by OA. The 954 neural genes identified to be upregulated in TNBC (PMID: 32080331) were compared to OA responsive genes in both cell lines. The Aldefluor assay was used to identify stem-like (ALDH+) cells in vehicle and OA treated MCF10A cells. To determine if lipid-exposed cells adopt a neural-like phenotype, MCF10A cells were grown on Poly-D-Lysine/Laminin (PDL/LM) coated plates.

Results. 5,684 and 5,305 genes were up- and down-regulated (FDR &lt; 0.01), respectively, in MCF12A OA treated cells. Numerous gene sets were significantly associated with OA exposure, including many neural-related pathways. More than 50% of the gene sets identified following OA-exposure were common to both cell lines. 418 and 303 neural genes upregulated in TNBC were significantly (FDR &lt; 0.01) upregulated after OA treatment in MCF10A and MCF12A, respectively. Cells growing on PDL/LM plates assumed the normal MCF10A phenotype in presence of vehicle while OA-treated cells adopted a neuronal-like phenotype. Upon OA treatment the percentage of ALDH+ cells increased by a minimum of 10%.

Conclusions. OA treatment was associated with the enrichment of ALDH+ cells, expression of neuronal-related genes and the development of neural-like phenotype. The upregulation neural genes upregulated in TNBC upon OA treatment may in part explain the association of lipid exposure and ER- BC. The upregulation of neural-related genes, and the development of neural-like phenotype suggests that lipid exposure results in cell state instability or plasticity, leading to reprogramming/selecting cells with a multi-potential embryonic or stem-like state that has been associated with tumor progression.

Citation Format: Mariana Bustamante Eduardo, Shivangi Yadav, Seema Khan, Susan Clare. Lipid treatment induces a neural-like phenotype in non-transformed breast epithelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3024.