Plasma-activated medium promotes autophagic cell death along with alteration of the mTOR pathway

Abstract

the biological function of non-thermal atmospheric pressure plasma has been widely accepted in several types of cancer. We previously developed plasma-activated medium (pAM) for clinical use, and demonstrated that PAM exhibits a metastasis-inhibitory effect on ovarian cancer through reduced MMP-9 secretion. However, the anti-tumor effects of PAM on endometrial cancer remain unknown. In this study, we investigated the inhibitory effect of PAM on endometrial cancer cell viability in vitro.Our results demonstrated that AMEC and HEC50 cell viabilities were reduced by PAM at a certain PAM ratio, and PAM treatment effectively increased autophagic cell death in a concentration dependent manner. in addition, we evaluated the molecular mechanism of pAM activity and found that the mtoR pathway was inactivated by pAM. Moreover, our results demonstrated that the autophagy inhibitor MHY1485 partially inhibited the autophagic cell death induced by PAM treatment. These findings indicate that pAM decreases the viability of endometrial cancer cells along with alteration of the mtoR pathway, which is critical for cancer cell viability. collectively, our data suggest that pAM inhibits cell viability while inducing autophagic cell death in endometrial cancer cells, representing a potential novel treatment for endometrial cancer.Endometrial cancer is the most common gynecologic malignancy in Japan, with an estimated 13,600 new cases diagnosed in 2015 1 . The incidence of new cases is believed to have increased over the last few decades due to increased levels of obesity, hypertension, and diabetes mellitus, particularly in South Africa and several Asian countries including Japan 1,2 . Although the majority of endometrial cancer patients are diagnosed in the early stage and outcomes are generally favorable because of the typical symptom of irregular vaginal bleeding in women of menopausal age, the prognoses of patients in advanced stages not amenable to localized therapies remain poor 1 . Indeed, a frequent pattern of progression and recurrence is peritoneal metastasis, which is often resistant to systemic chemotherapy 3 . In addition, cytotoxic agents for endometrial cancer are relatively limited compared with other gynecologic malignancies. Thus, there is an increasing demand for novel approaches to peritoneal dissemination.For the past decade, nonequilibrium atmospheric pressure plasma (NEAPP) has been studied for its clinical applications such as sterilization, wound healing, and cancer therapy 4-6 . NEAPP represents a partially ionized gas with energy mainly accumulated as free electrons 7 . Recent studies have revealed that in addition to the direct irradiation of NEAPP to bacteria or tissues, indirect plasma treatment with plasma-activated medium (PAM) and plasma-activated lactate (PAL), which are activated by NEAPP, exhibit anti-tumor activity in several types of cancer, including ovarian, pancreatic, colorectal and gastric cancers 4,8-13 . The molecular mechanism of the anti-tumor effects triggered by PAM have been investigat...

Autophagy as a decisive process for cell death

“…Neferine, a natural alkaloid isolated from Nelumbo nucifera, induces ACD via calcium release after the activation of ryanodine receptor (RYR) and ULK1-PERK and AMPK-mTOR signaling cascades, especially in apoptosis-resistant cancer cell lines, including HeLa, H1299, HepG2, and Lo2 cells 44 . Plasma-activated medium (PAM), which was developed for ovarian cancer suppression, induced ACD in some types of endometrial cancer cells 45 . PAM treatment increased ACD by inactivating the mTOR pathway, providing a potential novel treatment for endometrial cancer.…”

Gas Plasma-Oxidized Liquids for Cancer Treatment: Preclinical Relevance, Immuno-Oncology, and Clinical Obstacles

“…The clearest effects are made by the activation of caspases, or the involvement of p53 and increased BAX over BCL-2, as described above [33,57,63,64,66,67,86]. Further in vitro experiments that utilized gas plasma-oxidized liquids for cancer treatment made further suggestions for plasma effects playing an important role in the formation of cell death dependent on autophagy [50,52], the downregulation of survival proteins that are involved in the AKT pathway [87,88], targeting cell organelles like mitochondria and the endoplasmic reticulum [89][90][91], and redox-regulated changes in cell pathway activation and gene expression [92][93][94][95]. Moreover, alteration of the metastatic capacities of tumor cells [60,96] and their morphology, oxidation of the membrane [76,97,98], senescence (through intracellular zink) [36,45], and disturbances in the cells' metabolic profile [47] are examples of promising research.…”

Targeting Autophagy in Breast Cancer

“…In this context, an interplay between autophagy and apoptosis is supposed by the finding that in cancer models, when autophagy is inhibited, apoptosis is promoted [63]. Else, in preclinical models with defective apoptosis, other forms of cell death, such ACD, could occur [64][65][66][67][68][69][70][71][72].…”