Layered Single-Cell Heterogeneity in Hormone Receptor Signaling Across Mouse Organoids and Human ERα+ Cancer Cells

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Biology

Background:

• Hormone receptor signaling is crucial for mammary gland function.
• Receptor abundance is often used as a proxy for hormone responsiveness.
• The sources of variability in single-cell hormone responses are not well understood.

Purpose of the Study:

• To investigate the determinants of single-cell variability in estrogen (E2) and progesterone (P4) responses.
• To map hormone responses at single-cell resolution in murine mammary organoids.
• To explore the relationship between receptor abundance, co-regulators, and hormone response magnitude.

Main Methods:

• Utilized murine mammary organoids cultured in 3D.
• Performed single-cell resolution mapping of E2 and P4 transcriptional responses.
• Analyzed gene expression, including transcriptional co-regulators (Ncoa1, Ncor1, Ncor2).
• Examined ERα and PR protein abundance and activation kinetics in MCF7 cells.

Main Results:

• Murine mammary organoids show significant variability in hormone-induced transcriptional responses, independent of receptor abundance.
• Response magnitude correlates with the expression of transcriptional co-regulators.
• Mammary organoids possess a mixed basal-luminal enhancer landscape.
• ERα and PR protein abundance are remodeled in a growth factor-dependent manner.
• MCF7 cells exhibit delayed activation kinetics and a lower response plateau.

Conclusions:

• Hormone response magnitude in mammary organoids varies independently of receptor abundance.
• Transcriptional co-regulator balance plays a key role in modulating endocrine response magnitude.
• Mammary organoid enhancer landscape and protein remodeling influence hormone responsiveness.
• Human ERα-positive cancer cells display distinct hormone activation dynamics.