Abstract
Background: Progesterone receptors (PR) are potent modifiers of endocrine responses. In aberrant signalling cancer contexts, phosphorylation events dramatically alter steroid hormone receptor action. Methods: The transcriptomes of primary tumours and metastases in mice harbouring ER+ breast cancer patient-derived xenografts (PDXs) were analysed following single-cell RNAseq. In vitro assays were employed to delineate mechanisms of endocrine resistance and stemness. Results: A 16-gene phospho-Ser294 PR (p-PR) signature predicted poor outcome in ER+ breast cancer. Relative to primary PDX tumours, metastatic lesions expressed abundant p-PR and exhibited an activated PR gene programme with elevated expression of PGR and IRS-1. Breast cancer models of activated PR lost the expression of IGF1R and acquired insulin hypersensitivity with tamoxifen insensitivity. Activated p-PR+ breast cancer cells formed increased tumourspheres with enlarged ALDH+ and CD24−/CD44 populations. E2 induced PR/IRS-1 interaction and exchange of IGF1Rβ for IRS-1 in p-PR-containing transcriptional complexes. Inhibition of IRS-1 or IR and inducible IRS-1 knockdown reduced tumourspheres. Endocrine-resistant models of luminal B breast cancer induced p-PR in 3D cultures and required PR and IRS-1 for tumoursphere formation. Conclusions: Phospho-PR-B cooperates with IRS-1 to promote outgrowth of endocrine-resistant and stem-like breast cancer cells. Targeting phospho-PR/IRS-1 crosstalk may block the emergence of endocrine resistance. [Figure not available: see fulltext.]
Original language | English (US) |
---|---|
Pages (from-to) | 217-227 |
Number of pages | 11 |
Journal | British Journal of Cancer |
Volume | 124 |
Issue number | 1 |
DOIs | |
State | Published - Jan 5 2021 |
Bibliographical note
Publisher Copyright:© 2020, The Author(s), under exclusive licence to Cancer Research UK.