Projects
PELP1/SRC-3 complexes promote breast cancer stem cell activity
Model for SRC-3/PELP1 regulation of BCSC activity. (a) Nuclear PELP1 functions to maintain normal (differentiated) cell lineages and is required for normal cell viability. (b) Imbalanced nuclear-cytoplasmic shuttling favors cytoplasmic localization and altered regulation of chromatin remodeling. (c) Cytoplasmic PELP1 finds new binding partners that activate key signaling pathways. (d) Cyto-PELP1 promotes phospho-SRC-3 that participates in ER/PR transcription complexes at newly “open” SR target gene promoter regions. (e) Cyto PELP1/p-SRC-3-dependent target genes mediate BCSC expansion and therapy resistance in vivo. Red arrows refer to altered localization/signaling in breast cancer.
Breast cancer stem or stem-like progenitor cells (BCSCs) are non-proliferative, long-lived, evade first-line therapies and lead to the metastatic disease that kills most patients. Standard chemo- and endocrine therapies fail to adequately target BCSCs. The goal of our studies is to identify targetable signaling biomarkers that drive therapy resistance, metastasis, and the survival and self-renewal of BCSCs. Filling this knowledge gap will pave the way for interventions that increase therapy duration by specifically targeting minority populations of BCSCs within heterogeneous tumors.
Our prior work identified an interaction between PELP1 and SRC-3. This interaction is enhanced in cells expressing cytoplasmic (cyto) PELP1, which also display an increase in BCSC markers and tumorsphere formation knockdown of SRC-3 or chemical inhibition disrupts the PELP1/SRC-3 interaction and inhibits cytoplasmic PELP1 induced tumorsphere formation. Published work can be found at https://pubmed.ncbi.nlm.nih.gov/29348189/. Current studies are focused on understanding the signaling and transcriptional pathways activated by PELP1/SRC-3 complexes. This work is funded by NIH R01CA236948.
Cytoplasmic PELP1 signaling promotes inflammatory crosstalk with macrophages
Cytoplasmic PELP1 expression, which has been shown to interact with growth factor receptors (GFR), induces an increase in IKK protein expression (1), which leads to an increase in NF-B-dependent gene expression (2). We propose that the secretion of these protein products from HMECs results in macrophage activation (3), which in turn secrete paracrine factors (4) that stimulates HMEC migration (5).
Our research indicates that cyto PELP1 expression has different effects in normal human mammary epithelial cells (HMECs) compared to breast cancer cell lines. As described above, cyto PELP1 expression in ER+ breast cancer models has effects on BCSC activity. In HMECs, cyto PELP1 expression induces robust expression of inflammatory cytokines and chemokines. We found an increase in IKKepsilon in HMECs expressing cyto PELP1. Knockdown of IKKe inhibited cyto-PELP1 induced inflammatory gene expression. Furthermore, we found that cyto PELP1 expressing cells promoted in vitro macrophage activation, which promoted subsequent HMEC migration. The published work can be found at https://pubmed.ncbi.nlm.nih.gov/27881676/
The Ostrander Lab is currently developing mouse models to test the effect of cyto PELP1 expression and signaling in normal mammary epithelial cells in vivo.
Effects of the Extracellular Matrix on PELP1 Localization in Human Breast Tumor Cells
PELP1 (proline, glutamic acid, leucine rich protein 1) is a transcriptional co-regulator that is overexpressed in invasive breast cancer. In normal breast epithelial cells, PELP1 is primarily localized in the nucleus, while in some invasive breast tumors, PELP1 localization becomes cytoplasmic. The Ostrander lab and others have shown that cytoplasmic PELP1 signaling promotes cancer phenotypes. Although altered PELP1 localization has been observed in breast tumors, how PELP1 locatization becomes cytoplasmic during breast cancer initiation and progression is unknown. One aim of our research is to determine the mechanism leads to altered PELP1 localization to cytoplasm. We exploit 2D, 3D cell cultures and confocal imaging in addition to Western blotting of following nuclear and cytoplasmic fractionation in this study.