Abstract
The claudin-low molecular subtype of breast cancer is of particular interest for clinically the majority of these tumors are poor prognosis, triple negative, invasive ductal carcinomas. Claudin-low tumors are characterized by cancer stem cell-like features and low expression of cell junction and adhesion proteins. Herein, we sought to define the role of lipolysis stimulated lipoprotein receptor (LSR) in breast cancer and cancer cell behavior as LSR was recently correlated with tumor-initiating features. We show that LSR was expressed in epithelium, endothelium, and stromal cells within the healthy breast tissue, as well as in tumor epithelium. In primary breast tumor bioposies, LSR expression was significantly correlated with invasive ductal carcinomas compared to invasive lobular carcinomas, as well as ERα positive tumors and breast cancer cell lines. LSR levels were significantly reduced in claudin-low breast cancer cell lines and functional studies illustrated that re-introduction of LSR into a claudin-low cell line suppressed the EMT phenotype and reduced individual cell migration. However, our data suggest that LSR may promote collective cell migration. Re-introduction of LSR in claudin-low breast cancer cell lines reestablished tight junction protein expression and correlated with transepithelial electrical resistance, thereby reverting claudin-low lines to other intrinsic molecular subtypes. Moreover, overexpression of LSR altered gene expression of pathways involved in transformation and tumorigenesis as well as enhanced proliferation and survival in anchorage independent conditions, highlighting that reestablishment of LSR signaling promotes aggressive/tumor initiating cell behaviors. Collectively, these data highlight a direct role for LSR in driving aggressive breast cancer behavior.
Highlights
Breast cancer is a heterogeneous disease that varies in its etiology, pathophysiology and response to therapy
It is of note that MCF7 cells appeared to have a more diffused localization and higher abundance of cytoplasmic LSR compared to normal breast epithelium
We show a funtional role for LSR in directing breast cancer cell behavior
Summary
Breast cancer is a heterogeneous disease that varies in its etiology, pathophysiology and response to therapy. In attempts to understand the biological and clinical diversity of breast tumors, Perou and colleagues have developed molecular profiles characterizing the various intrinsic breast cancer subtypes, which have been successful at prediction of overall survival, relapse, and response to chemotherapy [1,2,3,4]. The majority of these tumors are invasive ductal carcinomas with a triple negative phenotype (lacking the estrogen receptor (ER) and progesterone receptor (PR), and do not overexpress the growth factor receptor Her). The majority of these tumors are invasive ductal carcinomas with a triple negative phenotype (lacking the estrogen receptor (ER) and progesterone receptor (PR), and do not overexpress the growth factor receptor Her2) While these tumors initially respond to chemotherapy, there is a high risk of recurrence, disease progression and, patient survival is poor [5,6]
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