H products from a single donor show .90 purity of cd T cells. (c and d) Cytotoxicity assays from two separate expansions (panel c and d, respectively) of unmodified cd T cells (solid line) versus TMZ P140KMGMT transduced cd T cells (dashed line) against the TMZ-resistant glioma cell line U87 were conducted to Title Loaded From File determine if genetic modification impairs cd T cell function. Cytolytic activity of cd T cells against U87 cells was nearly equivalent at all E:T ratios, verifying that P140KMGMT transduced cd T cells function is equivalent to that of unmodified cd T cells. doi:10.1371/journal.pone.0051805.gaddition of temozolomide to drug resistant GBM cells induces transient but consistent upregulation of several NKG2D ligands on the U87 GBM cell line that displays partial resistance to TMZ. In this scenario, the addition of genetically engineered variants of the parental cd T cells, that possess MHC unrestricted cytolytic properties, can potentially enhance tumor cell killing. The strategy of up-regulation of the stress/danger response of malignant cells following chemotherapy as a means of increasing their vulnerability to immune recognition and attack has been recentlyreviewed by others [26,49,50]. Consequently, up-regulation of stress-induced expression of NKG2D ligands on gliomas Title Loaded From File during chemotherapy can potentiate a DRI based anti-tumor strategy provided that immunocompetent cell therapies maintain efficacy during cytoreductive therapy. We have also shown that in the presence of high concentrations of temozolomide the genetically engineered cd T cells mediate significant killing of GBM cells that have been rendered resistant to temozolomide, whereas non-modified cells are ineffective. SNB-Table 1. Proliferation of Modified vs. Transduced cd T cells in Culture.Specimen 20100504 20100812Initial cd T cell number 5.Final* (unmodified) 2.Fold Expansion 46.3 73.1 438.Final* (transduced) 2.Fold Expansion 39.9 46.1 191.3.46106 2.1.66108 1.2.56108 5.*Cell dose is extrapolated to final volume of unmodified cells based on starting volume removed for transfection. doi:10.1371/journal.pone.0051805.tDrug Resistant cd T Cell ImmunotherapyFigure 5. TMZ-resistant clones of the GBM cell line (a) U373TMZ-R and (b) SNB-19TMZ-R were selected by incubation in increasing concentrations of TMZ over 60 days. The cell lines were labeled with PKH-26 and incubated for 4 hours in the presence of 100 mM TMZ alone (upper panel) and with P140KMGMT transduced cd T cells (cdTMZ-R) at a 10:1 effector:target ratio. The culture was then labeled with ToPro Iodide and acquired for flow cytometric phenotyping. A minimum of 5000 PKH26+ events was acquired to insure statistical validity of the data. All plots gated on PKH-26+ target cells. Note that the cloned cell lines are resistant to killing in media supplemented with TMZ with SNB-19TMZ-R showing less cell loss than U373TMZ-R. Addition of cdTMZ-R results in much greater incorporation of ToPro Iodide after 4 h incubation suggesting that the increased cytotoxicity is overwhelmingly due to genetically modified cd T cells. Dose-dependent cytotoxicity of cdTMZ-R is significantly less when assayed against SNB-19TMZ-R (c) with no TMZ in the media vs. cdTMZ-R against SNB-19TMZ-R in the presence of TMZ (p = 0.0085). Cytotoxicity was also trended greater against TMZ-resistant U373 with cdTMZ-R as effectors as well when the assay was conducted in 12926553 the presence of TMZ (p = .0875). These assays were conducted as separate experiments from dif.H products from a single donor show .90 purity of cd T cells. (c and d) Cytotoxicity assays from two separate expansions (panel c and d, respectively) of unmodified cd T cells (solid line) versus TMZ P140KMGMT transduced cd T cells (dashed line) against the TMZ-resistant glioma cell line U87 were conducted to determine if genetic modification impairs cd T cell function. Cytolytic activity of cd T cells against U87 cells was nearly equivalent at all E:T ratios, verifying that P140KMGMT transduced cd T cells function is equivalent to that of unmodified cd T cells. doi:10.1371/journal.pone.0051805.gaddition of temozolomide to drug resistant GBM cells induces transient but consistent upregulation of several NKG2D ligands on the U87 GBM cell line that displays partial resistance to TMZ. In this scenario, the addition of genetically engineered variants of the parental cd T cells, that possess MHC unrestricted cytolytic properties, can potentially enhance tumor cell killing. The strategy of up-regulation of the stress/danger response of malignant cells following chemotherapy as a means of increasing their vulnerability to immune recognition and attack has been recentlyreviewed by others [26,49,50]. Consequently, up-regulation of stress-induced expression of NKG2D ligands on gliomas during chemotherapy can potentiate a DRI based anti-tumor strategy provided that immunocompetent cell therapies maintain efficacy during cytoreductive therapy. We have also shown that in the presence of high concentrations of temozolomide the genetically engineered cd T cells mediate significant killing of GBM cells that have been rendered resistant to temozolomide, whereas non-modified cells are ineffective. SNB-Table 1. Proliferation of Modified vs. Transduced cd T cells in Culture.Specimen 20100504 20100812Initial cd T cell number 5.Final* (unmodified) 2.Fold Expansion 46.3 73.1 438.Final* (transduced) 2.Fold Expansion 39.9 46.1 191.3.46106 2.1.66108 1.2.56108 5.*Cell dose is extrapolated to final volume of unmodified cells based on starting volume removed for transfection. doi:10.1371/journal.pone.0051805.tDrug Resistant cd T Cell ImmunotherapyFigure 5. TMZ-resistant clones of the GBM cell line (a) U373TMZ-R and (b) SNB-19TMZ-R were selected by incubation in increasing concentrations of TMZ over 60 days. The cell lines were labeled with PKH-26 and incubated for 4 hours in the presence of 100 mM TMZ alone (upper panel) and with P140KMGMT transduced cd T cells (cdTMZ-R) at a 10:1 effector:target ratio. The culture was then labeled with ToPro Iodide and acquired for flow cytometric phenotyping. A minimum of 5000 PKH26+ events was acquired to insure statistical validity of the data. All plots gated on PKH-26+ target cells. Note that the cloned cell lines are resistant to killing in media supplemented with TMZ with SNB-19TMZ-R showing less cell loss than U373TMZ-R. Addition of cdTMZ-R results in much greater incorporation of ToPro Iodide after 4 h incubation suggesting that the increased cytotoxicity is overwhelmingly due to genetically modified cd T cells. Dose-dependent cytotoxicity of cdTMZ-R is significantly less when assayed against SNB-19TMZ-R (c) with no TMZ in the media vs. cdTMZ-R against SNB-19TMZ-R in the presence of TMZ (p = 0.0085). Cytotoxicity was also trended greater against TMZ-resistant U373 with cdTMZ-R as effectors as well when the assay was conducted in 12926553 the presence of TMZ (p = .0875). These assays were conducted as separate experiments from dif.