UTMD inhibits pancreatic cancer growth and metastasis by inducing macrophage polarization and vessel normalization

Pancreatic cancer (PaCa) is a hypovascular type of tumor and is not very responsive to conventional chemotherapy due to the problem of low drug accumulation. Recent advancements in ultrasound targeted microbubble destruction (UTMD) have improved drug delivery into target tissues. UTMD operates via microbubble interaction with vascular endothelial cells; however, the molecular mechanism and interrelationship in the PaCa microenvironment remain enigmatic. Tumor-associated macrophages (TAMs) have different phenotypes and regulate tumorigenesis. Using a PaCa orthotopic model, we established that UTMD improved chemotherapy by redirecting TAM polarization from M2 macrophages to tumor-inhibiting M1 macrophages, remodeling vessel normalization, and inducing anti-tumor immune responses. Tumor vascular maturity and function were also improved, and an insignificant change in vascular density resulting in enhanced blood perfusion and inhibited tumor growth and metastasis were observed. Therefore, this research unveils the crucial role of TAM polarization on UTMD-induced tumor vessel normalization and inhibition of tumor progression. These findings offer a novel insight into UTMD-mediated drug delivery for anti-tumor and anti-angiogenic treatment.