Cell survival and proliferation signaling pathways are downregulated by plasma-activated medium in glioblastoma brain tumor cells

Abstract

We previously reported that plasma-activated medium (PAM) selectively kills glioblastoma brain tumor cells by downregulating the signaling molecule, the serine-threonine kinase AKT. AKT kinase plays a key role in survival and proliferation by acting as a hub molecule in the signaling network to inhibit apoptosis. The pathways that contain AKT and that are affected by PAM are unclear. In this study of glioblastoma brain tumor cells, phosphorylation of AKT at both Ser473 and Thr308 was downregulated by PAM, suggesting that upstream signaling by the mammalian target of rapamycin complex 2 (mTORC2) and phosphatidylinositol-3 kinase (PI3K)/ 3-phosphoinositide-dependent protein kinase-1 (PDK1) were affected by PAM. Furthermore, the extracellular regulated kinase (ERK) signaling pathway, which is parallel to the AKT signaling pathway, was downregulated by PAM, and the mTORC1 signaling pathway, which is a major downstream signaling pathway of AKT and ERK, was also downregulated by PAM. In addition, CD44, a cell membrane-bound receptor that promotes both the AKT pathway and the ERK pathway, was downregulated by PAM. Taken together, these results suggest that PAM completely downregulates the survival and proliferation signaling network in glioblastoma brain tumor cells. FIG. 7: PAM downregulated CD44 expression in GBM cells. A) Schematic of the cell surface receptor, CD44, which transmits survival/proliferation signaling to the AKT and ERK signaling pathways. B) Western blotting of CD44 was performed with U251SP cells and WI-38 cells. Cells treated with PAM or control (Ar gas and untreated) medium. β-actin was used as a loading control. FIG. 8: PAM downregulated CD44 expression on the cell surface in GBM cells.U251SP GBM cells were observed with a microscope 4 hours after treatment with PAM, Ar gastreated medium, or untreated medium, which replaced the medium on the cells. Scale bar represents 50 μm.

Non-thermal atmospheric pressure plasma activates lactate in Ringer’s solution for anti-tumor effects

“…Cold plasma affects biological targets not only directly but also indirectly through the medium, which has broadened the potential applications of non-thermal atmospheric pressure plasma in medicine41424344454647484950. We have demonstrated that plasma-irradiated medium, also called plasma-activated medium (PAM), has anti-tumor effects against glioblastoma5152, as well as ovarian5354, gastric55, pancreatic56, and lung cancer cells57. Plasma interacts with oxygen, nitrogen, and water in air to produce various radicals, such as hydroxyl radicals and nitric oxide.…”

State of the art in medical applications using non-thermal atmospheric pressure plasma

“…For example, PAM induced apoptosis by downregulating the survival and proliferation of signaling molecules which are constitutively activated in a glioblastoma cell line (Tanaka et al , 2014a, caused caspase-independent apoptosis in a lung cancer cell line (Adachi et al 2014), elevated intracellular ferrous ion and the generation of hydroxyl radical in a lung cancer cell line (Adachi et al 2016), and caused cell death resulting from liberated intracellular zinc in a neuroblastoma cell line (Hara et al 2015).…”

“…mTOR complex 2 (mTORC2) is composed of mTOR, Rictor, GbL, Sin1, PRR5/Protor-1 proteins, and DEPTOR and acts upstream of AKT. Tanaka et al ( , 2014a investigated whether PAM affects the survival and proliferation signaling networks in glioblastoma brain tumor cells that constitutively activate both the PI3K-AKT and RAS-MAPK signaling pathways. They found that both signaling pathways were down-regulated in PAM-treated glioblastoma cells and constructed a model of the intracellular molecular mechanism by which PAM induces apoptosis in glioblastoma (namely, by inhibiting survival and proliferation signaling networks) [see Fig.…”

Plasma Medical Science for Cancer Therapy: Toward Cancer Therapy Using Nonthermal Atmospheric Pressure Plasma

“…We have recently discovered that PAM downregulated activities in the survival and proliferation signaling networks on glioblastoma brain tumor cells [20], [51]. Cancer cells often activate the specific survival and proliferation signaling by mutations, while normal cells activate the signaling only when the cells receive growth signals.…”

“…PAM downregulated survival and proliferation signaling networks on glioblastoma brain tumor cells[51]. (a) Western Blot analyses of survival and proliferation signaling molecules.…”