Fibrocytes enhance mammary gland fibrosis in obesity

The impact of the tumor microenvironment in the dual burden of obesity-cancer link

Obesity induces systemic perturbations of tissue homeostasis, leading to dyslipidemia, insulin resistance and chronic state of inflammation. Evidence from clinical and preclinical studies links excess of adiposity with increased cancer incidence and suggests that chronic inflammation may contribute to increased cancer risk in obese patients. Over the last decades of obesity research, multifaced and complicated effects of abnormal or excessive expansion of Adipose Tissue have been uncovered. In particular, it is widely described how obesity can exacerbate the tumorigenesis for instance by fueling soluble signals and adipokines and by enhancing tissue inflammation and altering the hormonal balance. Less is known about the paracrine effects of the cancer-associated adipocytes on the tumor cells and still poorly explored is the reciprocal communication between cancer cells and the adipose component of the tumor microenvironment (TME). In this review, we will address the mechanisms by which the peritumoral Adipose Tissue can influence the dynamics of tumoral cells. We will discuss how obesity-induced changes in the tumor microenvironment may enhance tumor growth and aggressive characteristics leading to increased invasiveness and metastatic progression of cancer that leads to a worsen cancer survival in obese subjects. We conclude that targeting the peritumoral adipose component of the TME would be a therapeutic option to prevent cancer development.

Gestational Intermittent Hypoxia Enhances Mammary Stem Cells and Alters Tumor Phenotype in Adult Female Offspring

An adverse perinatal environment can increase long-term cancer risk, although the precise nature of associated perinatal triggers remain unknown. Sleep apnea is a common condition during pregnancy, characterized by recurrent cessations in breathing during sleep, and the potential consequences of sleep apnea during pregnancy as it relates to breast cancer risk in offspring have not been explored. To model sleep apnea, Sprague-Dawley dams were exposed during gestation to nightly intermittent hypoxia (GIH) or normoxia (GNx), and the mammary glands of female offspring were examined. GIH offspring demonstrated increased epithelial stem and progenitor cell populations, which are associated with diminished transforming growth factor beta (TGFβ) activity. Elevations in adipose tissue stem cells in the mammary gland were also identified in GIH offspring. In aging females, mammary tumors formed in GIH offspring. These tumors displayed a dramatic increase in stroma compared to tumors from GNx offspring, as well as distinct patterns of expression of stem cell-related pathways. Together, these results suggest that exposure to sleep apnea during pregnancy leads to lasting changes in the mammary glands of female offspring. Increased stem and progenitor cell populations as a result of GIH exposure could enhance long-term breast cancer risk, as well as alter the clinical behavior of resulting breast tumors.