Abigail Sproull

PELP1 Regulated Pathways that Enhance Mammary Stem Cell Activity

Proline, glutamic acid, leucine rich protein 1 (PELP1) is an estrogen receptor coactivator that serves as a potential biomarker for breast cancer initiation. Cytoplasmic PELP1 signaling and associated protein complexes have been shown to promote cancer stem cell expansion and self-renewal in ER+ breast cancers. Mammosphere assays of normal epithelial cells also suggest that PELP1 plays a role in promoting mammary stem cell self-renewal. To better understand PELP1-induced pathways that promote mammary stem cell self-renewal and differentiation, the Ostrander lab performed RNA sequencing (RNA-seq) on RNA isolated from MCF10A cells, a model of normal mammary epithelial cells, cultured in standard 2D and 3D mammosphere conditions. RNA-seq results from MCF10A cells expressing either vector control (LXSN) , wild-type (WT) PELP1, or cytoplasmic (Cyto) PELP1 were analyzed in Ingenuity Pathway Analysis (IPA) to identify cytoplasmic PELP1 regulated pathways. IPA suggests that Wnt/β-catenin and TGFβ signaling is significantly upregulated in cytoplasmic PELP1 expressing cells cultured in mammosphere conditions, revealed by the highest activation z-scores in both the canonical pathways and the upstream regulator analysis. Both qPCR and Western Blotting were performed to verify the upregulation of the Wnt/β-catenin and TGFβ signaling pathways. Results of qPCR revealed FZD1, the receptor involved in Wnt signalling, to be upregulated in 3D conditions and is consistent with the RNA sequencing IPA analysis. Interestingly, Western Blots suggest that at the protein level β-catenin is upregulated in PELP1 expressing cells. Future studies will focus on the mechanisms associated with β-catenin and their influence on cell signaling. 

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