The β ₂ ^{‐adrenoceptor} activates a positive cAMP‐calcium feedforward loop to drive breast cancer cell invasion

Abstract

Activation of the sympathetic nervous system by stress increases breast cancer metastasis in vivo. Preclinical studies suggest that stress activates b-adrenoceptors (bARs) to enhance metastasis from primary tumors and that b-blockers may be protective in breast cancer. However, the subtype of bAR that mediates this effect, as well as the signaling mechanisms underlying increased tumor cell dissemination, remain unclear. We show that the b 2 AR is the only functionally relevant bAR subtype in the highly metastatic human breast cancer cell line MDA-MB-231HM. b 2 AR activation results in elevated cAMP (formoterol pEC 50 9.86 6 0.32), increased intracellular Ca 2+ (formoterol pEC 50 8.20 6 0.33) and reduced phosphorylated ERK (pERK; formoterol pIC 50 11.62 6 0.31). We demonstrate that a highly amplified positive feedforward loop between the cAMP and Ca 2+ pathways is responsible for efficient inhibition of basal pERK. Importantly, activation of the b 2 AR increased invasion (formoterol area under the curve [AUC] relative to vehicle: 1.82 6 0.36), which was dependent on the cAMP/ Ca 2+ loop (formoterol AUC in the presence of 2959-dideoxyadenosine 0.64 6 0.03, or BAPTA-AM 0.45 6 0.23) but independent of inhibition of basal pERK1/2 (vehicle AUC with U0126 0.60 6 0

Cancer cells become less deformable and more invasive with activation of β-adrenergic signaling

“…In cancer cells, β-adrenoceptors activate adenylyl cyclase, which results in accumulation of cAMP (Mukherjee et al, 1976;Pon et al, 2016). As shown in Fig.…”

“…To model invasive breast cancer in vitro, we used MDA-MB-231 breast cancer cells (Creed et al, 2015;Pon et al, 2016). We used both pharmacological and genetic tools to manipulate β-adrenergic signaling in cancer cells.…”

β 2 -Adrenoceptors on tumor cells play a critical role in stress-enhanced metastasis in a mouse model of breast cancer

“…We have previously shown that β 2 AR is the only functional βAR subtype in MDA-MB-231 HM cells (Pon et al, 2016). Therefore, we used two different hairpin sequences that target the gene encoding β 2 AR ( ADRB2 ) to knock down expression of β 2 AR in MDA-MB-231 HM breast cancer cells, and generated shADRB2a and shADRB2b cell lines.…”

“…Tumor cells also express βARs (Pon et al, 2016; Reeder et al, 2015), and activation of βAR signaling increases invasion of tumor cells, as measured by in vitro assays (Creed et al, 2015; Kim-Fuchs et al, 2014; Pon et al, 2016; Yamazaki et al, 2014) and in explant cultures (Creed et al, 2015). Previously, we discovered that the β 2 AR-selective agonist formoterol, but not the β 1 AR-selective agonist xamoterol, induced the formation of invadopodia in breast cancer cells (Creed et al, 2015).…”

Role of ESR Pathway Genes in Breast Cancer: A Review

“…While one report suggests that breast cancer cell migration is significantly inhibited by the activation of cAMP signaling, through either application of cell permeable cAMP analogs or by treatment with PDE inhibitors [183]. Another study claims that the positive cAMP/Ca 2+ loop is linked to increased invasion of breast cancer [184]. These reports are in direct contrast to one another, and consequently suggest that cAMPs function in breast cancer must alter depending on other cellular factors.…”