Abstract
Breast tumors overexpressing human epidermal growth factor receptor (HER2) confer intrinsic resistance to endocrine therapy (ET), and patients with HER2/estrogen receptor-positive (HER2+/ER+) breast cancer (BCa) are less responsive to ET than HER2-/ER+. However, real-world evidence reveals that a large subset of patients with HER2+/ER+ receive ET as monotherapy, positioning this treatment pattern as a clinical challenge. In the present study, we developed and characterized 2 in vitro models of ET-resistant (ETR) HER2+/ER+ BCa to identify possible therapeutic vulnerabilities. To mimic ETR to aromatase inhibitors (AIs), we developed 2 long-term estrogen deprivation (LTED) cell lines from BT-474 (BT474) and MDA-MB-361 (MM361). Growth assays, PAM50 subtyping, and genomic and transcriptomic analyses, followed by validation and functional studies, were used to identify targetable differences between ET-responsive parental and ETR-LTED HER2+/ER+ cells. Compared to their parental cells, MM361 LTEDs grew faster, lost ER, and increased HER2 expression, whereas BT474 LTEDs grew slower and maintained ER and HER2 expression. Both LTED variants had reduced responsiveness to fulvestrant. Whole-genome sequencing of aggressive MM361 LTEDs identified mutations in genes encoding transcription factors and chromatin modifiers. Single-cell RNA sequencing demonstrated a shift towards non-luminal phenotypes, and revealed metabolic remodeling of MM361 LTEDs, with upregulated lipid metabolism and ferroptosis-associated antioxidant genes, including GPX4. Combining a GPX4 inhibitor with anti-HER2 agents induced significant cell death in both MM361 and BT474 LTEDs. The BT474 and MM361 AI-resistant models capture distinct phenotypes of HER2 +/ER+ BCa and identify altered lipid metabolism and ferroptosis remodeling as vulnerabilities of this type of ETR BCa.
| Original language | English |
|---|---|
| Article number | bqad159 |
| Journal | Endocrinology (United States) |
| Volume | 164 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 1 2023 |
Funding
The authors would like to thank members of the Riggins laboratory, Drs. Michael Johnson, Marc Lippman, and Joyce Slingerland (Lombardi Comprehensive Cancer Center, Georgetown University), and members of NR IMPACT for sharing reagents, scientific insights, and/or technical assistance. This work was funded by the Department of Defense (DoD) Breast Cancer Research Program awards W81XWH-20-1-0759 and W81XWH-20-1-0760 (to R.B.R. and R.A.B., respectively), the Oak Ridge National Laboratory Director's R&D fund (to M.P. and R.A.B.), and philanthropy support from Lombardi Women at Georgetown Lombardi's Nina Hyde Center for Breast Cancer Research (to R.B.R.). Fellowship support for H.S. and S.T. was provided by the Tumor Biology Training Grant T32 CA009686 (principal investigator: Dr. Anna T. Riegel). D.M. received support from the Georgetown Regents Scholars Program. Technical services were provided by the Genomics and Epigenomics, Microscopy and Imaging, and Tissue Culture Shared Resources at GUMC, which are supported, in part, by NIH/NCI Cancer Center Support Grant P30 CA051008 (principal investigator: Dr. Louis M. Weiner). The content of this article is the sole responsibility of the authors and does not represent the official views of the DoD or NIH. This work was funded by the Department of Defense (DoD) Breast Cancer Research Program awards W81XWH-20-1-0759 and W81XWH-20-1-0760 (to R.B.R. and R.A.B., respectively), the Oak Ridge National Laboratory Director's R&D fund (to M.P. and R.A.B.), and philanthropy support from Lombardi Women at Georgetown Lombardi’s Nina Hyde Center for Breast Cancer Research (to R.B.R.). Fellowship support for H.S. and S.T. was provided by the Tumor Biology Training Grant T32 CA009686 (principal investigator: Dr. Anna T. Riegel). D.M. received support from the Georgetown Regents Scholars Program. Technical services were provided by the Genomics and Epigenomics, Microscopy and Imaging, and Tissue Culture Shared Resources at GUMC, which are supported, in part, by NIH/NCI Cancer Center Support Grant P30 CA051008 (principal investigator: Dr. Louis M. Weiner). The content of this article is the sole responsibility of the authors and does not represent the official views of the DoD or NIH.
| Funders | Funder number |
|---|---|
| Joyce Slingerland | |
| Oak Ridge National Laboratory | T32 CA009686 |
| National Institutes of Health | |
| U.S. Department of Defense | W81XWH-20-1-0759, W81XWH-20-1-0760 |
| National Cancer Institute | P30 CA051008 |
| Georgetown University | |
| Lombardi Comprehensive Cancer Center, Georgetown University |
Keywords
- HER2+/ER+
- breast cancer
- endocrine resistance
- human epidermal growth factor receptor 2
