Background: Chronic stress is known to promote cancer progression, in part by modulating immune responses through the β ₂ -adrenergic receptor (ADRB2). Inhibiting ADRB2 with β-blockers has demonstrated potential in boosting the effectiveness of immune checkpoint inhibitors across a spectrum of cancers, yet the precise mechanisms remain to be fully elucidated. Methods: In vivo and in vitro experiments were performed to evaluate the role of ADRB2 in melanoma models, including its effects on T cells. RNA sequencing analysis highlighted the importance of the transcription factor SRY-related HMG-box 10 (SOX10), which transcriptionally regulates programmed death-ligand 1 (PD-L1). This regulatory role was further validated using luciferase reporter assays and chromatin immunoprecipitation-PCR assays. Mechanistic studies focused on ADRB2 signaling through protein kinase A (PKA) and its downstream target SOX10. To investigate SOX10’s role in mediating the effects of ADRB2, knockdown and overexpression experiments were conducted. Additionally, similar studies in colorectal cancer (CRC) models confirmed the conserved function of the ADRB2-SOX10-PD-L1 axis. Results: This study explores the role of ADRB2 in regulating tumor PD-L1 expression and T cell functionality, offering insights for cancer immunotherapy. Clinical data revealed that patients with melanoma with high ADRB2 expression responded better to programmed cell death protein 1 inhibitors. In melanoma models, ADRB2 inhibition reduced PD-L1 expression, enhanced T cell infiltration, and promoted antitumor immunity, while ADRB2 activation had the opposite effect. Mechanistically, ADRB2 signaling through PKA upregulated SOX10, which transcriptionally modulates PD-L1. SOX10 knockdown replicated the effects of ADRB2 inhibition, while SOX10 overexpression reversed them. Similar findings in CRC models confirmed the conserved role of the ADRB2-SOX10-PD-L1 axis. Targeting ADRB2 and SOX10 may enhance immune checkpoint inhibitor efficacy in cancer treatment. Conclusions: These findings underscore the potential of ADRB2 and SOX10 as therapeutic targets for mitigating stress-induced immunosuppression and for augmenting the effectiveness of immunotherapies in a variety of cancer types.

Gastric cancer has one of the highest mortality rate in the world, but the treatment is still limited. Building on previous studies, mechanistic studies on propranolol in gastric cancer mice models and gastric cancer patients were performed. Propranolol inhibited thein vitroproliferation of gastric cancer cells in a time- and concentration-dependent manner. Consistent findings were observed in MFC tumors engrafted 615 mice, which were treated with propranolol at 10 mg/kg daily for 14 days. Propranolol inhibited the phosphorylation of AKT, MEK, and ERK proteins than control in mice tumor tissues respectively (p-AKT 26.16 vs. 56.82,P= 0.0196, p-MEK 28.27 vs. 59.28,P= 0.1102, p-ERK 48.2 vs. 107.4, P = 0.0062). Propranolol had antiproliferative activity in gastric cancer patients receiving 60 mg daily for 7 days prior to surgery(ki67 44.8 vs 125.3 for placebo; P = 0.02). Phosphorylated AKT, MEK, and ERK did not differ between propranolol and placebo treatment in gastric cancer patients. The expression of molecules on CD8⁺T cells was not changed both in mice model and patients nor was there a statistically significant difference in CD8⁺T cell subsets in patients, although suggestion of an effect was evident. These results prove that propranolol may inhibit the growth of gastric cancer in mice model and patients and the possible mechanism wasviainhibiting the AKT and MAPK pathways, but the frequency of tumor infiltration CD8⁺T cells did not increase significantly.

Oncolytic viruses (OVs) are considered a promising therapeutic alternative for cancer. However, despite the development of novel OVs with improved efficacy and tumor selectivity, their limited efficacy as monotherapeutic agents remains a significant challenge. This study extended our previously observed combination effects of propranolol, a nonselective β-blocker, and the T1012G oncolytic virus into colorectal cancer models. A cell viability assay showed that cotreatment could induce synergistic killing effects on human and murine colorectal cell lines. Moreover, cotreatment caused sustained tumor regression compared with T1012G monotherapy or propranolol monotherapy in human HCT116 and murine MC38 tumor models. The propranolol activity was not via a direct effect on viral replication in vitro or in vivo. Western blotting showed that cotreatment significantly enhanced the expression of cleaved caspase-3 in HCT116 and MC38 cells compared with the propranolol or T1012G alone. In addition, propranolol or T1012G treatment induced a 35.06% ± 0.53% or 35.49% ± 2.68% reduction in VEGF secretion in HUVECs (p < 0.01/p < 0.01). Cotreatment further inhibited VEGF secretion compared with the monotherapies (compared with propranolol treatment: 75.06% ± 1.50% decrease, compared with T1012G treatment: 74.91% ± 0.68%; p＜0.001, p < 0.001). Consistent with the in vitro results, in vivo data showed that cotreatment could reduce Ki67 and enhance cleaved caspase 3 and CD31 expression in human HCT116 and murine MC38 xenografts. In summary, β-blockers could improve the therapeutic potential of OVs by enhancing oncolytic virus-mediated killing of colorectal cancer cells and colorectal tumors.