Skeletal Colonization by Breast Cancer Cells Is Stimulated by an Osteoblast and β2AR-Dependent Neo-Angiogenic Switch

Abstract

The skeleton is a common site for breast cancer metastasis. Although significant progress has been made to manage osteolytic bone lesions, the mechanisms driving the early steps of the bone metastatic process are still not sufficiently understood to design efficacious strategies needed to inhibit this process and offer preventative therapeutic options. Progression and recurrence of breast cancer, as well as reduced survival of patients with breast cancer, are associated with chronic stress, a condition known to stimulate sympathetic nerve outflow. In this study, we show that stimulation of the beta 2-adrenergic receptor (β2AR) by isoproterenol, used as a pharmacological surrogate of sympathetic nerve activation, led to increased blood vessel density and Vegf-a expression in bone. It also raised levels of secreted Vegf-a in osteoblast cultures, and accordingly, the conditioned media from isoproterenol-treated osteoblast cultures promoted new vessel formation in two ex vivo models of angiogenesis. Blocking the interaction between Vegf-a and its receptor, Vegfr2, blunted the increase in vessel density induced by isoproterenol. Genetic loss of the β2AR globally, or specifically in type 1 collagen-expressing osteoblasts, diminished the increase in Vegf-positive osteoblast number and bone vessel density induced by isoproterenol, and reduced the higher incidence of bone metastatic lesions induced by isoproterenol following intracardiac injection of an osteotropic variant of MDA-MB-231 breast cancer cells. Inhibition of the interaction between Vegf-a and Vegfr2 with the blocking antibody mcr84 also prevented the increase in bone vascular density and bone metastasis triggered by isoproterenol. Together, these results indicate that stimulation of the β2AR in osteoblasts triggers a Vegf-dependent neo-angiogenic switch that promotes bone vascular density and the colonization of the bone microenvironment by metastatic breast cancer cells.

Nerves in Bone: Evolving Concepts in Pain and Anabolism

“…In the context of cancer, both progression and metastasis are associated with chronic stress, a condition that stimulates sympathetic outflow . In bone metastasis, sympathetic signaling via activation of β 2 ‐AR on osteoblasts leads directly to cancer cell recruitment and indirectly to vascular changes that promote colonization of metastatic cancer cells in the bone marrow . Last, NE uptake by bone and immune cells may also contribute to extraneuronal control of local NE homeostasis and actions on the skeleton …”

“…(120)(121)(122) In bone metastasis, sympathetic signaling via activation of β 2 -AR on osteoblasts leads directly to cancer cell recruitment and indirectly to vascular changes that promote colonization of metastatic cancer cells in the bone marrow. (121,123,124) Last, NE uptake by bone and immune cells may also contribute to extraneuronal control of local NE homeostasis and actions on the skeleton. (56,125,126) NPY NPY is the most abundant neuropeptide in the mammalian CNS and is also released from peripheral sympathetic nerves with NE.…”

β2AR-HIF-1α-CXCL12 signaling of osteoblasts activated by isoproterenol promotes migration and invasion of prostate cancer cells

“…Isoproterenol of sympathetic nerve activation factor has no direct effect on migration and invasion of prostate cancer cells Psychological distress was highest in men with biochemical recurrence and elevated clinical symptoms [21]. As chronic stress has been linked to cancer progression [7][8][9], whether increasing stress hormone in sympathetic outflow, typically caused by chronic stress, could directly alter migration and invasion of prostate cancer cells is of particular interest. Therefore, we first determined whether 10 μM isoproterenol(ISO), a non-selective bAR agonist as a pharmacological surrogate of sympathetic nerve activation [8], increased migration and invasion of human prostate cancer cells.…”

“…As chronic stress has been linked to cancer progression [7][8][9], whether increasing stress hormone in sympathetic outflow, typically caused by chronic stress, could directly alter migration and invasion of prostate cancer cells is of particular interest. Therefore, we first determined whether 10 μM isoproterenol(ISO), a non-selective bAR agonist as a pharmacological surrogate of sympathetic nerve activation [8], increased migration and invasion of human prostate cancer cells. As shown in Figure 1A-B, ISO treatment did not increase the number of cells of prostate cancer PC-3 and DU145 cells that migrated or invaded through transwell insert, suggesting that ISO has no direct effect on migration and invasion of prostate cancer cells.…”

“…Accumulating evidence showed that persistent secretion of stress-related hormones and neurotransmitters plays pivotal roles in the initiation and promotion of tumors [7]. Isoproterenol (ISO), a non-selective b-adrenergic receptor (bAR) agonist as a pharmacological surrogate of sympathetic nerve activation, promoted invasion and metastasis of tumors both in vitro and in vivo [8][9][10]. Current studies demonstrated that central and sympathetic nervous systems activated by chronic stress contributed to the tumor metastasis through b2-adrenergic receptor (b2AR) [11].…”