Propranolol Enhances the Oncolytic Effect of Newcastle Disease Virus on Canine Mammary Tumor Cell by Modulating the IFN-I-Mediated JAK-STAT Signaling Pathway

Canine mammary tumors (CMT) are the most common neoplasms in intact female dogs. While surgery remains the primary treatment, options for advanced or recurrent cases are limited. Newcastle disease virus (NDV), a promising oncolytic agent, exerts antitumor effects via direct oncolysis and immune activation. However, NDV infection concurrently induces Type I interferon (IFN-I) signaling, which stimulates antitumor immunity but restricts viral replication via the JAK-STAT pathway. Propranolol has been shown to enhance oncolytic virus efficacy by suppressing antiviral responses (e.g., STAT3 activation). Its potential synergy with NDV in CMT treatment remains unexplored. This study investigates whether propranolol potentiates NDV’s oncolytic activity in the canine mammary tumor cell line CMT-U27, by modulating IFN-I-mediated JAK-STAT signaling. IFN-I production and JAK-STAT activation were assessed in vitro and in vivo via ELISA, transcriptomic analysis, RT-qPCR, and Western blotting (WB). The combined effects of propranolol and NDV on CMT-U27 cells were evaluated using Cell Counting Kit-8 (CCK-8) assay, wound-healing assay, and Transwell assay. NDV uptake was assessed by immunofluorescence. The antitumor efficacy and safety of NDV were further investigated in CMT-U27 xenografted nude mice models. Transcriptomic analysis revealed NDV infection significant upregulated JAK-STAT pathway genes (JAK1, STAT1, STAT3 and MX1) in CMT-U27 cells. These findings were further validated by RT-qPCR and WB analyses. ELISA showed that NDV induced IFN-I release from CMT-U27 cells but not MDCK cells.Wound-healing assay and Transwell assays demonstrated that co-treatment with NDV and propranolol synergistically reduced CMT-U27 cell viability and suppressed migration and invasion more compared with either monotherapy. In the CMT-U27 xenograft model, intratumoral NDV combined with intraperitoneal propranolol significantly inhibited tumor growth and prolonged survival compared to monotherapy. Immunofluorescence analysis suggested that propranolol enhanced NDV replication. Moreover, ELISA, RT-qPCR, and WB analyses indicated that propranolol reduced the IFN-I release in NDV-infected nude mice and concurrently suppresses the activation of the JAK-STAT signaling pathway within their tumor tissues. This study demonstrates that propranolol enhances NDV-mediated oncolysis in CMT by suppressing IFN-I-dependent JAK-STAT signaling pathway and increaseing viral load in vitro and in vivo. NDV and propranolol co-treatment may offer a promising and well-tolerated therapeutic strategy for treating CMT.