Modeling ductal carcinoma in situ: a HER2–Notch3 collaboration enables luminal filling

Abstract

A large fraction of ductal carcinoma in situ (DCIS), a non-invasive precursor lesion of invasive breast cancer, overexpresses the HER2/neu oncogene. The ducts of DCIS are abnormally filled with cells that evade apoptosis, but the underlying mechanisms remain incompletely understood. We overexpressed HER2 in mammary epithelial cells and observed growth factor-independent proliferation. When grown in extracellular matrix as 3- dimensional spheroids, control cells developed a hollow lumen, but HER2-overexpressing cells populated the lumen by evading apoptosis. We demonstrate that HER2 overexpression in this cellular model of DCIS drives transcriptional up-regulation of multiple components of the Notch survival pathway. Importantly, luminal filling required up-regulation of a signaling pathway comprising Notch3, its cleaved intracellular domain (NICD) and the transcriptional regulator HES1, resulting in elevated levels of c-MYC and Cyclin D1. In line with HER2- Notch3 collaboration, drugs intercepting either arm reverted the DCIS-like phenotype. In addition, we report up-regulation of Notch3 in hyperplastic lesions of HER2 transgenic animals, as well as an association between HER2 levels and expression levels of components of the Notch pathway in tumor specimens of breast cancer patients. Therefore, it is conceivable that the integration of the Notch and HER2 signaling pathways contributes to the pathophysiology of DCIS.

Cyclin D1-Dependent Induction of Luminal Inflammatory Breast Tumors by Activated Notch3

“…Its expression correlates with Her2 levels in human breast tumors (20). Its overexpression was found to be associated with poor overall survival (19).…”

“…Overexpression of N3, along with N1, is associated with poor overall survival (19). N3 signaling was also reported to play a crucial role in the proliferation of HER-2-overexpressing ductal carcinoma in situ (20) and of ErbB2-negative breast cancer cells (21), to favor osteolytic bone metastasis of some breast cancer cell lines (22) and to be required for the growth of aggressive inflammatory breast cancer cells (23). Moreover, N3 controls survival of human mammary stem/progenitor cells in hypoxic environment (24).…”

FXR1a-associated microRNP: A driver of specialized non-canonical translation in quiescent conditions

“…[125][126][127][128] Hes1, a downstream effector of Notch signaling, is important for stem cell maintenance, prevents quiescent cells from differentiation and apoptosis, and is implicated in cancer progression. 59,121,[129][130][131][132][133] Consistently, components of the FXR1a-microRNP are implicated in cancer progression: FXR1 is known to promote tumor invasion and progression, 30 while its interacting partners, PARN and p97, are increased in activity or levels in many cancers. 98,134 Targeting components of the FXR1a-microRNP mechanism or associated microRNAs may help block translation of critical genes required for maintaining dormant cancer cells, and might be a promising approach against cancer recurrence.…”

Induction of Lumen Formation in a Three-dimensional Model of Mammary Morphogenesis by Transcriptional Regulator ID4

“…Lumen formation, a central feature of mammary morphogenesis, is lost during mammary tumorigenesis, starting with filling in the lumen with cancer cells in ductal carcinoma in situ (1) and becoming more evident in invasive solid tumors (2). Identification of the molecules that change during this process and the underlying mechanisms causing these changes are major goals of breast cancer research.…”