Abstract LB-458: Cold plasma selectively affects HNSCC cell lines by non-apoptotic pathways

Abstract

Abstract Plasma is an ionized gas that is typically generated in high temperature laboratory conditions. Recent progress in atmospheric plasmas has led to the creation of cold plasmas with ion temperature close to room temperature. We recently examined the therapeutic potential of a cold plasma jet in cancer cell lines and tumors, showing selective tumor eradication capabilities and apoptotic signaling pathway deregulation in melanoma cell lines. We now wanted to examine cold plasma selectivity in Head and Neck Squamous Cell Carcinoma (HNSCC) cell lines and identify signaling pathway deregulation leading to selectivity in HNSCC. We choose four HNSCC cell lines (022, 028, 029, SCC25) and two normal oral cavity epithelium cell lines (OKF6 and NOKsi) to carry out this experiment. Cold plasma treatments were carried out at 8 kV, using a helium flow of 20 liters/min-1, with a distance from plasma source to cells of 3 cm, and treatment durations of 10s, 30s, and 45s. We exposed cells in 96 well plates to cold plasma treatment durations of 10s, 30s, and 45s and a helium flow of 20 liters/min-1 for 10s as a positive treatment control. After treatment we transferred the cell lines to two sets of six well plates per cell line. To examine selective cell viability and growth in HNSCC following cold plasma application we performed the MTT assay to plated cells 48 hours after cold plasma application. Clonogenic or colony formation assays were performed to determine cell reproductive death seven days after treatment with cold plasma. Western blot analysis of PARP cleavage was perfomed 48 hours after treatment to determine if cold plasma application leads to selective cell death via apoptotic pathways in HNSCC. The MTT assay results revealed that cold plasma selectively diminished cell viability in SCC25 and O28, in a dose response manner. O22 and O29 cell lines showed diminished cell viability only after 30s and 45s treatments. The viability of OKF6 cells was not affected by cold plasma, while the viability of NOKsi cell lines was slightly diminished after 30s and 45s treatments. The results of the colony formation assay also revealed a cell specific response to cold plasma application. Exposure to helium flow for 10s did not impede colony formation. O28 and O29 cell lines did not form any colonies after the three cold plasma treatment periods. O22, SCC25 and OKF6 only formed colonies after cold plasma treatment for 10s. NOKsi formed colonies after all three cold plasma treatment periods. Western blot analysis did not show evidence that PARP cleavage is taking place after cold plasma treatment. Our preliminary results indicate that cold plasma application selectively affects some HNSCC cell lines more than other, while having minimal effect on normal oral cavity epithelium cell lines. We plan further to perform examination of cold plasma selectivity in HNSCC, to examine the in vitro effects of using different voltage, helium flow conditions and application distance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-458. doi:1538-7445.AM2012-LB-458