Beta-blockade enhances anthracycline control of metastasis in triple-negative breast cancer

Beta-adrenergic blockade has been associated with improved cancer survival in patients with triple-negative breast cancer (TNBC), but the mechanisms of these effects remain unclear. In clinical epidemiological analyses, we identified a relationship between beta-blocker use and anthracycline chemotherapy in protecting against TNBC progression, disease recurrence, and mortality. We recapitulated the effect of beta-blockade on anthracycline efficacy in xenograft mouse models of TNBC. In metastatic 4T1.2 and MDA-MB-231 mouse models of TNBC, beta-blockade improved the efficacy of the anthracycline doxorubicin by reducing metastatic development. We found that anthracycline chemotherapy alone, in the absence of beta-blockade, increased sympathetic nerve fiber activity and norepinephrine concentration in mammary tumors through the induction of nerve growth factor (NGF) by tumor cells. Moreover, using preclinical models and clinical samples, we found that anthracycline chemotherapy up-regulated β₂-adrenoceptor expression and amplified receptor signaling in tumor cells. Neurotoxin inhibition of sympathetic neural signaling in mammary tumors using 6-hydroxydopamine or genetic deletion of NGF or β₂-adrenoceptor in tumor cells enhanced the therapeutic effect of anthracycline chemotherapy by reducing metastasis in xenograft mouse models. These findings reveal a neuromodulatory effect of anthracycline chemotherapy that undermines its potential therapeutic impact, which can be overcome by inhibiting β₂-adrenergic signaling in the tumor microenvironment. Supplementing anthracycline chemotherapy with adjunctive β₂-adrenergic antagonists represents a potential therapeutic strategy for enhancing the clinical management of TNBC.