NOTCH1 PEST domain variants are responsive to standard of care treatments despite distinct transformative properties in a breast cancer model.

Karen Cravero,Daniel J Zabransky,Kelly Kyker-Snowman,Dan Shinn,Ben Ho Park,Joshua Donaldson,Dong Ho Shin,Berry Button,Morgan V Pantone,David Chu,Swathi Karthikeyan,Hong Yuen Wong,Natasha Hunter,Sarah Croessmann,W Brian Dalton,Paula J Hurley,Ian Waters ,Rory L Cochran ,Riley E Bergman ,David Rosen

doi:10.18632/oncotarget.28200

Abstract

Activating variants in the PEST region of NOTCH1 have been associated with aggressive phenotypes in human cancers, including triple-negative breast cancer (TNBC). Previous studies suggested that PEST domain variants in TNBC patients resulted in increased cell proliferation, invasiveness, and decreased overall survival. In this study, we assess the phenotypic transformation of activating NOTCH1 variants and their response to standard of care therapies. AAV-mediated gene targeting was used to isogenically incorporate 3 NOTCH1 variants, including a novel TNBC frameshift variant, in two non-tumorigenic breast epithelial cell lines, MCF10A and hTERT-IMEC. Two different variants at the NOTCH1 A2241 site (A2441fs and A2441T) both demonstrated increased transformative properties when compared to a non-transformative PEST domain variant (S2523L). These phenotypic changes include proliferation, migration, anchorage-independent growth, and MAPK pathway activation. In contrast to previous studies, activating NOTCH1 variants did not display sensitivity to a gamma secretase inhibitor (GSI) or resistance to chemotherapies. This study demonstrates distinct transformative phenotypes are specific to a given variant within NOTCH1 and these phenotypes do not correlate with sensitivities or resistance to chemotherapies or GSIs. Although previous studies have suggested NOTCH1 variants may be prognostic for TNBC, our study does not demonstrate prognostic ability of these variants and suggests further characterization would be required for clinical applications.

Highlights

Triple negative breast cancer (TNBC) is a subtype of breast cancer that accounts for 15–20% of all diagnosed patients
This study investigated a novel NOTCH1 PEST domain frameshift variant as well as two previously reported variants to determine cancerous phenotypes and whether these variants could serve as predictive markers for therapeutic response in triple-negative breast cancer (TNBC)
These efforts have led to the identification of Notch1 as a key player in breast carcinogenesis

Summary

Introduction

Triple negative breast cancer (TNBC) is a subtype of breast cancer that accounts for 15–20% of all diagnosed patients. Patients with TNBC lack expression of these receptors and are limited to standard surgery, chemotherapy, and radiation for treatment options. In 2011, Lehmann et al demonstrated TNBC can be classified into distinct subtypes based on gene expression profiles and these molecular differences may dictate response to therapy [1]. These distinct molecular differences combined with the aggressive nature of TNBC have resulted in poor treatment options, increased rates of recurrence and metastases, and decreased overall survival [2–4]. Clinical studies for TNBC have begun focusing on new targeted therapies, such as poly (ADP-ribose) polymerase (PARP) inhibitors, anti-Trop antibody drug conjugates and immunotherapies, along with potential predictive markers for these therapies [5]

Methods

Results

Conclusion