Inhibition of autophagy promotes sonodynamic therapy-induced apoptosis of pancreatic cancer cells

Introduction. Sonodynamic therapy (SDT), a promising non-invasive therapeutic modality, has attracted increasing attention in the treatment of pancreatic cancer (PC). At present, the role of autophagy in SDT of PC remains unclear. This study aims to explore the role of autophagy in SDT of PC and its effect on apoptosis of PC cells. Material and methods. PC cells (Capan-1 and BxPC-3) underwent incubation with 5-aminolevulinic acid (5-ALA) or/and ultrasound (US) exposure (control, 5-ALA, US, and SDT groups), followed by measurement of cell apoptosis and autophagy. Specifically, cell viability, apoptosis, and the expression of apoptosis-related proteins (cleaved Caspase-3, Bax, and Bcl-2) were measured using CCK-8 assay, flow cytometry, and western blot analysis, respectively. The mitochondrial morphology was observed with the transmission electron microscopy, accompanied by the detection of autophagosome marker (LC3) co-located with Mito and the protein expression of LC3II/I. Before SDT treatment, the autophagy inhibitor 3-MA and the apoptosis inhibitor z-VAD were respectively added to PC cell cultures to evaluate the effects of autophagy inhibition on apoptosis and apoptosis inhibition on autophagy in PC cells. Results. Compared with the control group, cell viability was inhibited and cell apoptosis and autophagy were enhanced in the SDT group, while cell viability, autophagy, and apoptosis in the 5-ALA and US groups were not significantly changed. Moreover, 3-MA treatment inhibited autophagy and accelerated apoptosis, whereas z-VAD treatment reduced apoptosis but did not affect autophagy in PC cells. Conclusions. Autophagy was activated in SDT-treated PC cells, and inhibition of autophagy promoted cell apoptosis in PC cells. (Folia Histochemica et Cytobiologica 2023, Vol. 61, No. 3, 172-182)