Fig. 4.

Schematic showing how activators and blockers of the sympathetic nervous system affect tumor and immune mediators. Propranolol promotes cell apoptosis by upregulating p53. Norepinephrine increases tumor cell proliferation by inducing expression of IL-6, which is regulated by the cAMP/PKA signaling pathway. Chronic stress promotes tumor growth via phosphorylated STAT3, which induces the numbers of MDSCs. β-adrenergic signals enhance the numbers of CD14⁺ CD68⁺ TAMs and macrophages via increased production of MCP1. Chronic stress and norepinephrine inhibit DNA damage repair mechanisms and prevent p53-associated cell apoptosis. The figure was created with BioRender.com.