Cold plasma treatment of in vitro gliomas and patient-derived tumors – Role of human myeloid cells

Abstract

Tumor-associated macrophages (TAM) are the pre-dominant myeloid cells within malignant glioma and are a poor prognostic factor in patients. TAM in malignant glioma show a tumor-supporting, so-called M2 phenotype. The aim of this study was to characterize phenotype and relevant markers of monocytes/macrophages in the tumor microenvironment following exposure to cold physical plasma Monocytes were enriched from peripheral blood mononuclear cells derived from young healthy volunteers donating blood after informed consent and in accordance with the guidelines of the local ethics committee. Monocytes were co-cultured with a glioma cell line (U87MG). The latter readily induced a M2 phenotype in these monocytes as seen by an increase in CD163 expression. Prior to co-culture, either U87MG cells or monocytes were treated with an atmospheric pressure argon plasma jet (kINPen) for 15 seconds or 5 seconds, respectively. Non-treated co-cultures as well as single monocytes cultures served as controls. FACS immuno-phenotyping of monocytes/macrophages was performed for CD55, CD97, CD162, CD163, CD169, CD204, CD276, HLA-DR, and HLA-ABC after 24h, 48h, and 72h. M2 polarization of monocytes by U87MG was neither attenuated nor reversed by plasma treatment. We next exposed primary glioblastoma patient material to cold physical plasma (kINPen) ex vivo. After treatment, tissues were incubated for 24h, and supernatants were collected. Multiplex cytokine analysis of supernatants. Results of five patients showed an absence of IFNα, IFNγ, IL12p70, IL17α, and IL23, and a presence of IL1β, TNFα, MCP1, IL6, IL8, IL10, IL18, and IL33 in samples. A mixed response was observed. For instance, both of the myeloid-cell interacting proteins MCP1 and IL1β are associated with glioma aggressiveness, and secretion of IL1β decreased after plasma treatment whereas MCP1 was increased. Glioma tissue sections will determine the distribution of myeloid cells within the tumor after plasma treatment compared to controls.

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Figure 1: Fold change of several chemokines/cytokines in kINPen plasma-treated primary human glioblastoma samples compared to untreated glioma tissue.