Estrogen regulates divergent transcriptional and epigenetic cell states in breast cancer

Breast cancers are known to be driven by the transcription factor estrogen receptor and its ligand estrogen. While the receptor's cis-binding elements are known to vary between tumors, heterogeneity of hormone signaling at a single-cell level is unknown. In this study, we systematically tracked estrogen response across time at a single-cell level in multiple cell line and organoid models. To accurately model these changes, we developed a computational tool (TITAN) that quantifies signaling gradients in single-cell datasets. Using this approach, we found that gene expression response to estrogen is non-uniform, with distinct cell groups expressing divergent transcriptional networks. Pathway analysis suggested the two most distinct signatures are driven separately by ER and FOXM1. We observed that FOXM1 was indeed activated by phosphorylation upon estrogen stimulation and silencing of FOXM1 attenuated the relevant gene signature. Analysis of scRNA-seq data from patient samples confirmed the existence of these divergent cell groups, with the FOXM1 signature predominantly found in ER negative cells. Further, multi-omic single-cell experiments indicated that the different cell groups have distinct chromatin accessibility states. Our results provide a comprehensive insight into ER biology at the single-cell level and potential therapeutic strategies to mitigate resistance to therapy.

Combined androgen excess and Western-style diet accelerates adipose tissue dysfunction in young adult, female nonhuman primates

STUDY QUESTION

What are the separate and combined effects of mild hyperandrogenemia and consumption of a high-fat Western-style diet (WSD) on white adipose tissue (WAT) morphology and function in young adult female nonhuman primates?

SUMMARY ANSWER

Combined exposure to mild hyperandrogenemia and WSD induces visceral omental (OM-WAT) but not subcutaneous (SC-WAT) adipocyte hypertrophy that is associated with increased uptake and reduced mobilization of free fatty acids.

WHAT IS KNOWN ALREADY

Mild hyperandrogenemia in females, principally in the context of polycystic ovary syndrome, is often associated with adipocyte hypertrophy, but the mechanisms of associated WAT dysfunction and depot specificity remain poorly understood.

STUDY DESIGN, SIZE AND DURATION

Female rhesus macaques were randomly assigned at 2.5 years of age (near menarche) to receive either cholesterol (C; n = 20) or testosterone (T; n = 20)-containing silastic implants to elevate T levels 5-fold above baseline. Half of each of these groups was then fed either a low-fat monkey chow diet or WSD, resulting in four treatment groups (C, control diet; T alone; WSD alone; T + WSD; n = 10/group) that were maintained until the current analyses were performed at 5.5 years of age (3 years of treatment, young adults).

PARTICIPANTS/MATERIALS, SETTING AND METHODS

OM and SC-WAT biopsies were collected and analyzed longitudinally for in vivo changes in adipocyte area and blood vessel density, and ex vivo basal and insulin-stimulated fatty acid uptake and basal and isoproterenol-stimulated lipolysis.

MAIN RESULTS AND THE ROLE OF CHANCE

In years 2 and 3 of treatment, the T + WSD group exhibited a significantly greater increase in OM adipocyte size compared to all other groups (P < 0.05), while the size of SC adipocytes measured at the end of the study was not significantly different between groups. In year 3, both WAT depots from the WSD and T + WSD groups displayed a significant reduction in local capillary length and vessel junction density (P < 0.05). In year 3, insulin-stimulated fatty acid uptake in OM-WAT was increased in the T + WSD group compared to year 2 (P < 0.05). In year 3, basal lipolysis was blunted in the T and T + WSD groups in both WAT depots (P < 0.01), while isoproterenol-stimulated lipolysis was significantly blunted in the T and T + WSD groups only in SC-WAT (P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

At this stage of the study, subjects were still relatively young adults, so that the effects of mild hyperandrogenemia and WSD may become more apparent with increasing age.

WIDER IMPLICATIONS OF THE FINDINGS

The combination of mild hyperandrogenemia and WSD accelerates the development of WAT dysfunction through T-specific (suppression of lipolytic response by T), WSD-dependent (reduced capillary density) and combined T + WSD (increased fatty acid uptake) mechanisms. These data support the idea that combined hyperandrogenemia and WSD increases the risk of developing obesity in females.

STUDY FUNDING/COMPETING INTEREST(S)

Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health under award number P50 HD071836 to C.T.R. and award number OD 011092 from the Office of the Director, National Institutes of Health, for operation of the Oregon National Primate Research Center. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Long-lasting effect of obesity on skeletal muscle transcriptome

BACKGROUND

Reduced physical activity and increased intake of calorically-dense diets are the main risk factors for obesity, glucose intolerance, and type 2 diabetes. Chronic overnutrition and hyperglycemia can alter gene expression, contributing to long-term obesity complications. While caloric restriction can reduce obesity and glucose intolerance, it is currently unknown whether it can effectively reprogram transcriptome to a pre-obesity level. The present study addressed this question by the preliminary examination of the transcriptional dynamics in skeletal muscle after exposure to overnutrition and following caloric restriction.

RESULTS

Six male rhesus macaques of 12-13 years of age consumed a high-fat western-style diet for 6 months and then were calorically restricted for 4 months without exercise. Skeletal muscle biopsies were subjected to longitudinal gene expression analysis using next-generation whole-genome RNA sequencing. In spite of significant weight loss and normalized insulin sensitivity, the majority of WSD-induced (n = 457) and WSD-suppressed (n = 47) genes remained significantly dysregulated after caloric restriction (FDR ≤0.05). The Metacore^TM pathway analysis reveals that western-style diet induced the sustained activation of the transforming growth factor-β gene network, associated with extracellular matrix remodeling, and the downregulation of genes involved in muscle structure development and nutritional processes.

CONCLUSIONS

Western-style diet, in the absence of exercise, induced skeletal muscle transcriptional programing, which persisted even after insulin resistance and glucose intolerance were completely reversed with caloric restriction.