It has been reported that cancer stem cells may contribute to glioma radioresistance through preferential activation of the DNA damage checkpoint response and an increase in DNA repair capacity. We have examined DNA repair in five stem and nonstem glioma cell lines. The population doubling time was significantly increased in stem compared with nonstem cells, and enhanced activation of Chk1 and Chk2 kinases was observed in untreated CD133 + compared with CD133 À cells. Neither DNA base excision or single-strand break repair nor resolution of pH2AX nuclear foci were increased in CD133 + compared with CD133 À cells. We conclude that glioma stem cells display elongated cell cycle and enhanced basal activation of checkpoint proteins that might contribute to their radioresistance, whereas enhanced DNA repair is not a common feature of these cells. (Mol Cancer Res 2009;7(3):383 -92)

Herein we describe that in classic Hodgkin lymphomas (cHL, n ‫؍‬ 25) the lymph node (LN) stroma displayed in situ high levels of transcription and expression of the disulfide-isomerase ERp5 and of the disintegrin-metalloproteinase ADAM10, able to shed the ligands for NKG2D (NKG2D-L) from the cell membrane. These enzymes were detected both in LN mesenchymal stromal cells ( IntroductionIt is now accepted that the so-called stress surveillance contributes to the anti-neoplastic immunity, both in solid tumors and hematologic malignancies, through the activation of the NKG2D receptor that recognizes NKG2D ligands (NKG2D-L) on cancer cells, including the MHC class-I related chain-A and -B (MIC-A/B) and the UL16-binding proteins 1-4 (ULBPs). [1][2][3][4][5] These ligands are commonly expressed at very low levels or retained in the cytoplasm, in healthy tissues, but their transcription and surface expression are enhanced on viral infection or tumor transformation. [5][6][7][8][9] Besides natural killer cells and CD8 ϩ T lymphocytes, ␥␦ T cells can recognize these molecules and activate an antitumor response in different cancers. [10][11][12][13][14][15][16][17] In this regard, we have described that ␥␦ T lymphocytes belonging to the V␦1 subset are expanded in patients with chronic lymphocytic leukemia (CLL) and nonHodgkin lymphomas (NHLs), where they proliferate in response to tumor cells, provided they express NKG2D-L, exert cytotoxicity, and produce anti-neoplastic or pro-differentiating cytokines, such as TNF-␣ and IL-4. 15,16 However, NKG2D-L can be shed by tumor cells and, in their soluble form, interact with NKG2D expressed by effector lymphocytes and hinder the recognition of tumor cells. 18,19 Proteolytic cleavage of MIC-A has been shown to depend on the thiol isomerase ERp5 and the disintegrins and metalloproteinases ADAM10 and ADAM17, which are also able to cleave ULBPs. 19,22 Overexpression of these enzymes has been reported in multiple myeloma and other tumors. [19][20][21][22][23] In turn, soluble (s) NKG2D-L and cytokines produced at the tumor site can down-regulate the expression of the NKG2D receptor on effector lymphocytes, contributing to tumor escape from immunosurveillance. [22][23][24][25] Indeed, the TGF-␤ has been shown to reduce the surface density of the NKG2D receptor on CD8 ϩ T and NK cells, impairing their antitumor reactivity in cancer patients. [24][25][26] Moreover, we and others reported that plasma levels of sNKG2D-L correlate with disease progression in multiple myeloma, CLL, NHL, and acute myeloid leukemias; in particular, among sNKG2D-L, both sMIC-A and sULBP2 have been shown as a prognostic marker for multiple myeloma and for the identification of early-stage CLL patients with risk of disease progression. [14][15][16]21,27,28 In this paper, we studied 25 classic HL (cHL) and found that the tumor microenvironment is prone to inhibit the development of an antitumor response. This is mainly because of the release of soluble MIC-A and ULBP3 by lymph node mesenchymal stromal cells (LN MS...

We have previously shown that pharmacological inhibition of ataxia telangiectasia mutated (ATM) protein sensitizes glioblastoma-initiating cells (GICs) to ionizing radiation (IR). Herein, we report the experimental conditions to overcome GIC radioresistance in vitro using the specific ATM inhibitor KU-60019, two major determinants of the tumor response to this drug and the absence of toxicity of this treatment in vitro and in vivo. Repeated treatments with KU-60019 followed by IR substantially delayed GIC proliferation in vitro and even eradicated radioresistant cells, whereas GIC treated with vehicle plus radiation recovered early and expanded. The tumor response to the drug occurred under a cutoff level of expression of TP53 and over a cutoff level of expression of phosphatidylinositol 3-kinase (PI3K). No increased clastogenicity or point mutagenicity was induced by KU-60019 plus radiation when compared to vehicle plus radiation. No significant histological changes to the brain or other organs were observed after prolonged infusion into the brain of KU-60019 at millimolar concentrations. Taken together, these findings suggest that GIC-driven tumors with low expression of TP53 and high expression of PI3K might be effectively and safely radiosensitized by KU-60019.Glioblastoma multiforme (GBM) is difficult to eradicate for its highly infiltrating nature and resistance to therapies (reviewed in Ref. 1). Autopsy findings have shown infiltration of tumoral cells even in the contralateral hemisphere, suggesting that GBM may be considered as a "whole brain disorder." 2,3 As a consequence, to eradicate high-grade gliomas we have to treat large portions or even the whole brain. This cannot be done with toxic treatments that would seriously affect patients' cognitive and physiological functions. To specifically target glioma-initiating cells (GICs) we have to

Exposure of freshly drawn lymphocytes and lymphoblastoid cells (LB and COR3) to simulated microgravity decreased the intracellular ATP concentration to 50%-40% of the value found in normal growth conditions. The decrease was reversible although recovery to normal values occurred only slowly both in lymphocytes and in lymphoblastoid cells. Poly(ADP-ribose) polymerase (PARP ) activity was increased indicating that cells exposed to conditions of reduced gravitation experience stress. Exposure to microgravity forces cells into a condition of metabolic quiescence in which they appear to be particularly sensitive to subsequent exposures to a genotoxic agent. Thus, treatment of cells with the strong redox agent potassium bromate under microgravity conditions, indicated an impairment in repair of DNA 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidized derivative of deoxyguanosine. We conclude that gravitational modulation of the kind routinely obtained under laboratory conditions and during spaceflights is a stressful process to which cells appear to be extremely sensitive. These effects may reflect the physiological alterations observed in astronauts and in animals following spaceflights or exposure to conditions of simulated microgravity.