The Sympathetic Nervous System Modulates Cancer Vaccine Activity through Monocyte-Derived Cells

Abstract

The sympathetic nervous system (SNS) is an important regulator of immune cell function during homeostasis and states of inflammation. Recently, the SNS has been found to bolster tumor growth and impair the development of antitumor immunity. However, it is unclear whether the SNS can modulate APC function. Here, we investigated the effects of SNS signaling in murine monocyte-derived macrophages (moMФ) and dendritic cells (DCs) and further combined the nonspecific β-blocker propranolol with a peptide cancer vaccine for the treatment of melanoma in mice. We report that norepinephrine treatment dramatically altered moMФ cytokine production, whereas DCs were unresponsive to norepinephrine and critically lack β2-adrenergic receptor expression. In addition, we show that propranolol plus cancer vaccine enhanced peripheral DC maturation, increased the intratumor proportion of effector CD8+ T cells, and decreased the presence of intratumor PD-L1+ myeloid-derived suppressor cells. Furthermore, this combination dramatically reduced tumor growth compared with vaccination alone. Taken together, these results offer insights into the cell-specific manner by which the SNS regulates the APC immune compartment and provide strong support for the use of propranolol in combination with cancer vaccines to improve patient response rates and survival.

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“…8 In addition, propranolol administration together with tumour vaccines enhanced vaccine immunity and the accumulation of T cells within tumour tissues. [51][52][53][54] Similar immune enhancing effects were observed when propranolol was co-administered with ICI (immune checkpoint inhibitor) immunotherapy. 4,[26][27][28]55 Importantly, studies have also demonstrated that pharmacologic activation of the SNS pathway, using beta agonists such as isoproterenol, stimulated tumour growth associated with greater mobilisation of MDSC from bone marrow and accumulation in tumour tissues.…”

“…For example, in one study propranolol treatment reversed the recruitment of MDSC into tumour and lymphoid tissues, slowed the growth of subcutaneous tumours and blocked tumour metastases 8 . In addition, propranolol administration together with tumour vaccines enhanced vaccine immunity and the accumulation of T cells within tumour tissues 51–54 . Similar immune enhancing effects were observed when propranolol was co‐administered with ICI (immune checkpoint inhibitor) immunotherapy 4,26–28,55 .…”