Obesity, proinflammatory mediators, adipose tissue progenitors, and breast cancer

Single-Cell RNA-seq Reveals Obesity-Induced Alterations in the Brca1-Mutated Mammary Gland Microenvironment

Clinical and experimental studies have shown that obesity increases the development and progression of breast cancer. The impact of obesity on the tumor microenvironment plays an important role in tumorigenesis, yet the precise mechanisms underlying obesity-mediated effects on cell-to-cell communication within the tumor microenvironment have been difficult to define. In this study, we conducted single-cell RNA sequencing (scRNA-seq) studies to investigate the impact of high-fat diet (HFD)-induced obesity on transcriptomic landscapes of stromal and immune cells in mammary glands of Brca1−/−; p53+/− mice, an animal breast cancer model. Hierarchical clustering and gene pathway enrichment analyses of scRNA-seq data showed that five different subtypes of stromal fibroblasts existed in mouse Brca1-mutated mammary glands. HFD-induced obesity led to upregulated expression of extracellular matrix (ECM) genes (Col3a1, Col6a3, Eln, and Sparc) and downregulated expression of immunoregulatory genes (Iigp1 and Cxcl10) in these stromal subtype cells. These findings, taken together, suggest that obesity alters the ECM composition and immune ecosystem through modulating the functionality of mammary stromal fibroblasts. Moreover, scRNA-seq analysis of mammary immune cells indicated that HFD-induced obesity promoted the generation and/or recruiting of pro-tumorigenic M2 macrophages in mammary glands. Our studies provide new insight into a mechanistic paradigm wherein obesity modulates the functions of stromal and immune cells to create the tumorigenic microenvironment for promoting breast tumorigenesis.

Pre-pregnancy obesity and childhood malignancies: A population-based cohort study

OBJECTIVE

Exploring the effect of maternal obesity during pregnancy on the long-term health of offspring is of great importance. The aim of this study was to evaluate the association between maternal pre-pregnancy obesity and future risk of childhood malignancies.

STUDY DESIGN

A population-based cohort analysis comparing the risk for long-term childhood malignancies (up to the age of 18 years) in children born (1991-2014) to mothers with and without pre-pregnancy obesity (body mass index > 30) was conducted in July 2017. Childhood malignancies were predefined based on ICD-9 codes, as recorded in the hospital medical files. Children with congenital malformations and multiple gestations were excluded from the analysis. The Kaplan-Meier survival curve was constructed to compare cumulative oncological morbidity in both groups over time. The Cox proportional hazards model was used to control for confounders.

RESULTS

During the study period, 241 273 infants met the inclusion criteria; 3268 were born to mothers with pre-pregnancy obesity. Children of obese women had significantly increased risk for several childhood malignancies (including brain tumors) as well as increased risk for total hospitalizations with malignancy diagnoses, even after controlling for several confounders (adjusted HR 1.90, 95% CI 1.07-3.37, P = 0.028). Cumulative incidence of oncological morbidity was also significantly increased over time in the studied group (log-rank P = 0.023).

CONCLUSION

Maternal pre-pregnancy obesity is significantly associated with an increased long-term risk for general childhood malignancies, and specifically brain tumors in the offspring. These results are important when counseling mothers regarding potential future risks and recommended lifestyle modifications.

Early or late recurrences of breast carcinoma are to be researched in relation to fat grafting

Not available.

Breast Lipofilling Does Not Pose Evidence of Chronic Inflammation in Rats

BACKGROUND

Laboratory reports on adipose tissue suggest that fat grafting to the breast may pose an oncologic risk. One possible reason for this is the theoretic chronic inflammation due to adipokynes released by grafted white adipose tissue (WAT).

OBJECTIVES

The aim of this study was to analyze inflammatory activity in lipofilled breast through the use of proinflammatory markers.

METHODS

Fifty-four paired-breasts of female rats were divided into 4 groups: control, sham, and breasts grafted with either autologous subcutaneous (SC) WAT or autologous omentum (OM). The WAT was prepared through centrifugation, and the grafting was performed with the use of 0.9-mm blunt-tip cannula. The rats were killed 8 weeks postoperatively, and their breasts were harvested for immunohistochemical staining for CD68-expressing macrophages, gene expression (real-time PCR) for monocyte chemoattractant protein 1 (MCP-1), F4/80, Cox-2, and IL-6.

RESULTS

The weights of the rats that underwent a procedure differed from those of the unmanipulated control group (P < 0.01). The macrophage counts of CD68 differed only between breasts lipofilled with OM and control (P < 0.01). MCP-1, F4/80, and Cox-2 were similarly expressed among the groups (P = 0.422, P = 0.143, and P = 0.209, respectively). The expression of IL-6 differed between breast samples grafted with SC and OM WAT (P = 0.015), but not between samples of control and OM (P = 0.752), and control and SC (P = 0.056).

CONCLUSIONS

No inflammation activity was identified in the microenvironment of lipofilled breasts, indicating that chronic inflammation does not seem to be triggered by the breast lipofilling procedure.

PDGFRα+ stromal adipocyte progenitors transition into epithelial cells during lobulo-alveologenesis in the murine mammary gland

The mammary gland experiences substantial remodeling and regeneration during development and reproductive life, facilitated by stem cells and progenitors that act in concert with physiological stimuli. While studies have focused on deciphering regenerative cells within the parenchymal epithelium, cell lineages in the stroma that may directly contribute to epithelial biology is unknown. Here we identify, in mouse, the transition of a PDGFRα⁺ mesenchymal cell population into mammary epithelial progenitors. In addition to being adipocyte progenitors, PDGFRα⁺ cells make a de novo contribution to luminal and basal epithelia during mammary morphogenesis. In the adult, this mesenchymal lineage primarily generates luminal progenitors within lobuloalveoli during sex hormone exposure or pregnancy. We identify cell migration as a key molecular event that is activated in mesenchymal progenitors in response to epithelium-derived chemoattractant. These findings demonstrate a stromal reservoir of epithelial progenitors and provide insight into cell origins and plasticity during mammary tissue growth.

Inhibitory effects of BMP9 on breast cancer cells by regulating their interaction with pre-adipocytes/adipocytes

Bone morphogenetic protein 9 (BMP9) possesses multiple functions, but its effects on breast cancer cells in adipose microenvironment are still unclear. This study aimed to investigate whether BMP9 is able to modulate the interaction between pre-adipocytes/adipocytes and breast cancer cells. An in vitro co-culture system was established by using pre-adipocytes/adipocytes and MDA-MB-231 breast cancer cells with BMP9 over-expression. The leptin expression and leptin-induced signaling pathway were evaluated in this co-culture system. MTT assay, EdU assay and flow cytometry were used to assess the proliferation of MDA-MB-231 cells. Wound-healing assay and Transwell migration assay were used to assess the migration of MDA-MB-231 cells. Immunofluorescence staining was used to detect the expression of leptin recepter (ObR) in MDA-MB-231 cells. The expression of key molecules in leptin signaling pathway in co-culture system were detected by Western blotting. MDA-MB-231 cells and pre-adipocytes/adipocytes were inoculated into nude mice, the tumor volume was measured, and the protein expression of key molecules in leptin signaling pathway was detected. Results showed BMP9 inhibited breast tumor growth in vitro and in vivo and reduced the migration of breast cancer cells in vitro. MDA-MB-231 cells with BMP9 over-expression decreased leptin expression in pre-adipocytes/adipocytes and had reduced phosphorylation of STAT3, ERK1/2 and AKT. Taken together, our study indicates that BMP9 can inhibit the growth and metastasis of breast cancer cells, which may be related to interaction between pre-adipocytes/adipocytes and MDA-MB-231 cells via leptin signaling pathway.

Prepregnancy obesity: a risk factor for future development of ovarian and breast cancer

The aim of this study was to investigate the association between a history of prepregnancy obesity and a woman's future long-term risk for the development of female malignancies. A population-based study compared the incidence of long-term female malignancies in a cohort of consecutive women with and without a diagnosis of prepregnancy obesity. Deliveries occurred between the years 1988 and 2013, with a mean follow-up duration of 11.6 years. Women with known malignancies before the index pregnancy and known genetic predisposition for malignancy were excluded from the study. Female malignancies were divided according to specific type (ovary, uterine, breast, and uterine cervix). A Kaplan-Meier survival curve was used to estimate the cumulative incidence of malignancies. A Cox proportional hazards model was used to estimate the adjusted hazard ratios for female malignancy. During the study period, 106 251 deliveries fulfilled the inclusion criteria; 2.2% (n=2360) occurred in patients with a history of prepregnancy obesity. During the follow-up period, patients with prepregnancy obesity had a significantly increased risk for hospitalization because of female malignancies as a group and specifically ovarian and breast cancer. Using a Kaplan-Meier survival curve, patients with a previous diagnosis of prepregnancy obesity had a significantly higher cumulative incidence of female malignancies. Using a Cox proportional hazards model, adjusted for confounders such as gestational diabetes mellitus and maternal age, prepregnancy obesity remained independently associated with long-term risk for female malignancies (adjusted hazard ratio: 1.4; 95% confidence interval: 1.1-1.9; P=0.045). Prepregnancy obesity is an independent risk factor for long-term female malignancies such as ovarian and breast cancer.

Adipose Progenitor Cell Secretion of GM-CSF and MMP9 Promotes a Stromal and Immunological Microenvironment That Supports Breast Cancer Progression

A cell population with progenitor-like phenotype (CD45-CD34⁺) resident in human white adipose tissue (WAT) is known to promote the progression of local and metastatic breast cancer and angiogenesis. However, the molecular mechanisms of the interaction have not been elucidated. In this study, we identified two proteins that were significantly upregulated in WAT-derived progenitors after coculture with breast cancer: granulocyte macrophage colony-stimulating factor (GM-CSF) and matrix metallopeptidase 9 (MMP9). These proteins were released by WAT progenitors in xenograft and transgenic breast cancer models. GM-CSF was identified as an upstream modulator. Breast cancer-derived GM-CSF induced GM-CSF and MMP9 release from WAT progenitors, and GM-CSF knockdown in breast cancer cells neutralized the protumorigenic activity of WAT progenitors in preclinical models. GM-CSF neutralization in diet-induced obese mice significantly reduced immunosuppression, intratumor vascularization, and local and metastatic breast cancer progression. Similarly, MMP9 inhibition reduced neoplastic angiogenesis and significantly decreased local and metastatic tumor growth. Combined GM-CSF neutralization and MMP9 inhibition synergistically reduced angiogenesis and tumor progression. High-dose metformin inhibited GM-CSF and MMP9 release from WAT progenitors in in vitro and xenograft models. In obese syngeneic mice, metformin treatment mimicked the effects observed with GM-CSF neutralization and MMP9 inhibition, suggesting these proteins as new targets for metformin. These findings support the hypothesis that GM-CSF and MMP9 promote the protumorigenic effect of WAT progenitors on local and metastatic breast cancer. Cancer Res; 77(18); 5169-82. ©2017 AACR.

Non-glycanated Decorin Is a Drug Target on Human Adipose Stromal Cells

Adipose stromal cells (ASCs) have been identified as a mesenchymal cell population recruited from white adipose tissue (WAT) by tumors and supporting cancer progression. We have previously reported the existence of a non-glycanated decorin isoform (ngDCN) marking mouse ASCs. We identified a peptide CSWKYWFGEC that binds to ngDCN and hence can serve as a vehicle for ASC-directed therapy delivery. We used hunter-killer peptides composed of CSWKYWFGEC and a pro-apoptotic moiety to deplete ASCs and suppress growth of mouse tumors. Here, we report the discovery of the human non-glycanated decorin isoform. We show that CSWKYWFGEC can be used as a probe to identify ASCs in human WAT and tumors. We demonstrate that human ngDCN is expressed on ASC surface. Finally, we validate ngDCN as a molecular target for pharmacological depletion of human ASCs with hunter-killer peptides. We propose that ngDCN-targeting agents could be developed for obesity and cancer treatment.

Assessment of the Cancer Risk of the Fat-Grafted Breast in a Murine Model

Background

The results of experimental studies indicate that grafting of autologous adipose tissue may induce tumorigenesis at the recipient site, but clinical results do not support a carcinogenic effect of fat grafting to the breast.

Objectives

The authors assessed cancer risk following transplantation of autologous fat into murine mammary tissue.

Methods

In this animal study, mammary tissues from 54 breasts of 9 female rats were either grafted with autologous subcutaneous fat, grafted with autologous omental fat, or unmanipulated. Tissues were harvested and processed for histologic and immunohistochemical analyses, and the mRNA expression levels of specific genes were determined.

Results

No atypia or changes in lobular structures were observed in lipofilled breasts compared with controls. The numbers of ductal cell layers and terminal ductal units were similar for lipofilled and control breasts. Macrophage concentrations also were similar for the 3 groups. The localization and magnitude of plasminogen activator inhibitor 1 were similar for lipofilled and unmanipulated breast tissue. The percentages of cells expressing Ki67 or estrogen receptor (ER) and the ER/Ki67 balance were similar for the 3 groups. Gene expression was not altered in lipofilled breasts, compared with controls.

Conclusions

No theoretical risk of cancer was detected in the microenvironment of the lipofilled rat breast.

BET bromodomain proteins and epigenetic regulation of inflammation: implications for type 2 diabetes and breast cancer

Chronic inflammation drives pathologies associated with type 2 diabetes (T2D) and breast cancer. Obesity-driven inflammation may explain increased risk and mortality of breast cancer with T2D reported in the epidemiology literature. Therapeutic approaches to target inflammation in both T2D and cancer have so far fallen short of the expected improvements in disease pathogenesis or outcomes. The targeting of epigenetic regulators of cytokine transcription and cytokine signaling offers one promising, untapped approach to treating diseases driven by inflammation. Recent work has deeply implicated the Bromodomain and Extra-Terminal domain (BET) proteins, which are acetylated histone "readers", in epigenetic regulation of inflammation. This review focuses on inflammation associated with T2D and breast cancer, and the possibility of targeting BET proteins as an approach to regulating inflammation in the clinic. Understanding inflammation in the context of BET protein regulation may provide a basis for designing promising therapeutics for T2D and breast cancer.

Central obesity and risks of pre- and postmenopausal breast cancer: a dose-response meta-analysis of prospective studies

Epidemiologic evidence has shown inconsistent findings regarding the relationships between abdominal fatness, as measured by waist circumferences (WC) or waist-to-hip ratio (WHR), and risks of pre- and postmenopausal breast cancer (BC). A dose-response meta-analysis of prospective studies was conducted to address these issues. Potentially eligible studies were identified by searching PubMed and EMBASE databases, and by carefully reviewing the bibliographies of retrieved publications and related reviews. The summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model. When the most fully adjusted RRs were combined, both WC (14 studies, RR _{per 10-cm increase}  = 1.06, 95% CI: 1.04-1.09, I²  = 29.9%) and WHR (15 studies, RR _{per 0.1-unit increase}  = 1.07, 95% CI: 1.01-1.14, I²  = 52.9%) were significantly positively associated with postmenopausal BC, but neither WC (eight studies, RR _{per 10-cm increase}  = 1.05, 95% CI: 0.99-1.10, I²  = 0%) nor WHR (11 studies, RR _{per 0.1-unit increase}  = 1.07, 95% CI: 0.95-1.21, I²  = 59.7%) were associated with premenopausal BC. The WHR-postmenopausal BC association lost statistical significance after correcting publication bias (RR _{per 0.1-unit increase}  = 1.06, 95% CI: 0.99-1.13). When considering BMI-adjusted RRs, WC was associated with both pre- (five studies, RR _{per 10-cm increase}  = 1.09, 95% CI: 1.02-1.16, I²  = 0%) and postmenopausal BC (seven studies, RR _{per 10-cm increase}  = 1.05, 95% CI: 1.02-1.08, I²  = 6.3%), whereas WHR was not associated with either pre- (seven studies, RR _{per 0.1-unit increase}  = 1.12, 95% CI: 0.94-1.34, I²  = 70.9%) or postmenopausal BC (eight studies, RR _{per 0.1-unit increase}  = 1.05, 95% CI: 0.98-1.13, I²  = 57.3%). Among non-current (former or never) users of hormone replacement therapy, the summary RR _{per 10-cm increase} of postmenopausal BC associated with WC was 1.08 (95% CI: 1.03-1.05, I²  = 69.2%, seven studies; BMI-adjusted RR = 1.05, 95% CI: 1.02-1.09, I²  = 22.8%, four studies). This meta-analysis indicates that central obesity measured by WC, but not by WHR, is associated with modestly increased risks of both pre- and postmenopausal BC independent of general obesity.

Cancer as a Proinflammatory Environment: Metastasis and Cachexia

The development of the syndrome of cancer cachexia and that of metastasis are related with a poor prognostic for cancer patients. They are considered multifactorial processes associated with a proinflammatory environment, to which tumour microenvironment and other tissues from the tumour bearing individuals contribute. The aim of the present review is to address the role of ghrelin, myostatin, leptin, HIF, IL-6, TNF-α, and ANGPTL-4 in the regulation of energy balance, tumour development, and tumoural cell invasion. Hypoxia induced factor plays a prominent role in tumour macro- and microenvironment, by modulating the release of proinflammatory cytokines.