A Novel Effect of β-Adrenergic Receptor on Mammary Branching Morphogenesis and its Possible Implications in Breast Cancer

Abstract

Understanding the mechanisms that govern normal mammary gland development is crucial to the comprehension of breast cancer etiology. β-adrenergic receptors (β-AR) are targets of endogenous catecholamines such as epinephrine that have gained importance in the context of cancer biology. Differences in β-AR expression levels may be responsible for the effects of epinephrine on tumor vs non-tumorigenic breast cell lines, the latter expressing higher levels of β-AR. To study regulation of the breast cell phenotype by β-AR, we over-expressed β-AR in MCF-7 breast cancer cells and knocked-down the receptor in non-tumorigenic MCF-10A breast cells. In MCF-10A cells having knocked-down β-AR, epinephrine increased cell proliferation and migration, similar to the response by tumor cells. In contrast, in MCF-7 cells overexpressing the β-AR, epinephrine decreased cell proliferation and migration and increased adhesion, mimicking the response of the non-tumorigenic MCF-10A cells, thus underscoring that β-AR expression level is a key player in cell behavior. β-adrenergic stimulation with isoproterenol induced differentiation of breast cells growing in 3-dimension cell culture, and also the branching of murine mammary epithelium in vivo. Branching induced by isoproterenol was abolished in fulvestrant or tamoxifen-treated mice, demonstrating that the effect of β-adrenergic stimulation on branching is dependent on the estrogen receptor (ER). An ER-independent effect of isoproterenol on lumen architecture was nonetheless found. Isoproterenol significantly increased the expression of ERα, Ephrine-B1 and fibroblast growth factors in the mammary glands of mice, and in MCF-10A cells. In a poorly differentiated murine ductal carcinoma, isoproterenol also decreased tumor growth and induced tumor differentiation. This study highlights that catecholamines, through β-AR activation, seem to be involved in mammary gland development, inducing mature duct formation. Additionally, this differentiating effect could be resourceful in a breast tumor context.

Prognostic significance of α‐ and β2‐adrenoceptor gene expression in breast cancer patients

“…41 In fact, our group has recently reported that the differentiation of BALB/c mouse mammary glands promoted by the β-agonist isoproterenol, is highly dependent on OR activity. 18 Although α 2 and β-adrenoceptors has been classically described as antagonistic, in the present investigation their expression was associated with similar outcomes, functional enrichment analysis suggesting distinctive mechanisms. High expression of ADRA2A appears to be related to inhibited tumour cell proliferation whereas the ADRB2 gene seems to be involved in antitumour immunity.…”

“…A concomitant stimulatory effect of macrophages has been described in these models . Other groups, including our own, found on the contrary, that these receptors are associated with decreased cell proliferation, tumour growth, migration and experimental metastases …”

“…Associations between OR and the β 2 ‐adrenoceptor are recurrent in the bibliography, suggesting that interactions between their signalling pathways may be essential for the regulation of breast cancer biology . In fact, our group has recently reported that the differentiation of BALB/c mouse mammary glands promoted by the β‐agonist isoproterenol, is highly dependent on OR activity …”

“…11,13 Other groups, including our own, found on the contrary, that these receptors are associated with decreased cell proliferation, tumour growth, migration and experimental metastases. [14][15][16][17][18] The relevance of α 2 -adrenoceptors in human breast cancer has been less studied. Our group has described their presence in breast models, in association with increased cell proliferation and tumour growth upon activation with specific agonists.…”

A fast genetically encoded fluorescent sensor for faithfulin vivoacetylcholine detection in mice, fish, worms and flies

“…Moreover, the sensor responds (positively or negatively) to all molecules that normally bind the M3 receptor, precluding the use of GACh2.0 in combination with many cholinergic drugs. Finally, over-expression of GPCRs perturbs the function of endogenous proteins such as G-proteins 21,22 and can disrupt cellular behavior 23 , creating concerns that GACh2.0-expressing cells may have altered ACh and/or other signaling pathways.…”