High-voltage pulsed electric field plus photodynamic therapy kills breast cancer cells by triggering apoptosis

This study evaluated the effects and mechanism of action of combining irreversible electroporation (IRE) and photodynamic therapy (PDT) in breast cancer cells in vitro and in vivo. Jin's formula was used to assess killing efficacy of different IRE+PDT dosing combinations in breast cancer MCF-7 cells. Flow cytometry, high-content imaging, and confocal laser scanning microscopy were used to detect apoptosis. qRT-PCR and western blotting were used to evaluate expression of apoptosis-related genes and proteins. IRE+PDT combination therapy was administered to BALB/C mice with breast cancer tumors in vivo; tumor size was used to assess treatment efficacy. Killing mechanisms were examined using transmission electron microscopy and immunohistochemistry. We found that IRE+PDT combination therapy produced significant synergistic killing effects in breast cancer cells (highest Jin q value of 1.32). Early apoptosis rates were significantly higher in the IRE+PDT group (16.0%) than in IRE-alone (7.6%) and PDT-alone (4.6%) groups (P<0.05). qRT-PCR showed higher Caspase-1, -3, -5, -6, -7, -8, and -9 and TNFRSF1A expression with IRE+PDT than with control. Western blots showed increased cleaved Caspase-3, -7, and -9, and PARP levels in the IRE+PDT group. In vivo tumor suppression rate for IRE (1200 V)+PDT (10 mg/kg) was 68.3%. Combination therapy produced the most obvious apoptosis effects. Compared with controls, the IRE+PDT group exhibited lower new blood vessel (VEGF, CD31), metastasis (TGF-β), and cell proliferation (Ki-67) indicators and higher inflammation indicator (TNF-α) 1 day post-treatment. Thus, combining IRE and PDT enhanced their anti-tumor effects in breast cancer, and apoptosis played a key role in this process.