Inhibition Of Breast Cancer Cell Growth By PDT Is Mediated Though Autophagic Cell Death In Vitro

Objective: To understand the function and molecular mechanism underlying PDT induced autophagy in human breast cancer MDA-MB-231 cells in vitro. This study aims to provide theoretical basis for the application of MPPa-PDT in clinical setting for human breast cancer.Methods: The cytotoxicity on MDA-MB-231 cells was assessed using the cck-8 assay. Intracellular reaction oxygen species were detected by DCFH-DA staining. Evaluated the Apoptosis level of the MDA-MB-231 cells by FCM with Annexin V-FITC/PI staining. Detected autophagy level was observed by Monodansylcadaverine staining. The localization of photosensitizer(MPPa) was assessed using ER-Tracker? green. The expression of LC3 Beclin-1,P62,BIP,CHOP PPERK signaling pathway was tested by western blotting.Results: After treatment with 2 μM of MPPa for 24 h and combination with a series of light radiation, the viability of cells decreased in dose-dependent manner. With the treatment of 2 μM(2.7J/cm2) MPPa-PDT, it was found that the increase of ROS in PDT treatment group after light-activated 2 h were more obvious than other groups by DCFH-DA staining. FCM with Annexin V-FITC/PI staining showed the apoptotic rate of PDT treatment group after light-activated 24 h was significantly higher than other groups, autophagic vacuoles increased along with the increase expression of LC3 B II Beclin-1 and decline expression of P62 in PDT treatment group after light-activated 24 h were more obvious than other groups by monodansylcadaverine(MDC) staining and Western blot analysis respectively. However, pretreatment with autophagy inhibitor 3-MA, LC3B-II formation was blocked, and it also a reduction in cytotoxicity and apoptosis compared with the treatment of MPPa-PDT alone. MPPa-PDT caused an increase in ER stress markers(BIP,CHOP) due to MPPa accumulation in endoplasmic by ER-Tracker? green staining. However, pretreatment with ER stress inhibitor 4PBA, the expression of ER stress marker(BIP) and autophagy marker(LC3B II) were blocked and the PERK signaling pathway was activated during MPPa-PDTConclusion :MPPa-PDT effectively suppressed cancer development in MDA-MB-231 cells and autophagy regulated by ER stress, via PERK signaling pathway, participated in cell death in MPPa-PDT.