Methylating drugs such as temozolomide (TMZ) are widely used in the treatment of brain tumors including malignant glioblastoma. The mechanism of TMZ-induced glioblastoma cell death and apoptosis, however, is not fully understood. Here, we tested the potential involvement of AMP-activated protein kinase (AMPK) in this process. We found that methylating agents TMZ and N-methyl-N-nitro-N-nitrosoguanidine induce AMPK activation in primary cultured human glioblastoma and glioblastoma cell lines. TMZ-induced O 6 -methylguanine production is involved in AMPK activation. O 6 -benzylguanine, an O 6 -methylguanine-DNA methyltransferase inhibitor, enhances TMZ-induced O 6 -methylguanine production, leading to enhanced reactive oxygen species production, which serves as an upstream signal for AMPK activation. Activation of AMPK is involved in TMZ-induced glioblastoma cell death and apoptosis. AMPK inhibitor (Compound C) or AMPK␣ siRNA knockdown inhibits TMZ-induced glioblastoma cell death and apoptosis, whereas AMPK activator 5-aminoimidazole-4-carboxamide-1-␤-D-ribofuranoside enhances it. In further studies, we found that activation of AMPK is involved in TMZ-induced p53 activation and subsequent p21, Noxa, and Bax up-regulation. Activation of AMPK by TMZ also inhibits mTOR complex 1 (mTORC1) signaling and promotes anti-apoptosis protein Bcl-2 down-regulation, which together mediate TMZ-induced pro-cell apoptosis effects. Our study suggests that activation of AMPK by TMZ contributes to glioblastoma cell apoptosis, probably by promoting p53 activation and inhibiting mTORC1 signaling.Astrocytic tumors are the most common primary brain tumors. Of the astrocytic tumors, malignant glioblastoma is the most malignant form and has the worst prognosis. Complete surgical resection of glioblastoma is difficult, and the tumor generally recurs within a year after radiation and chemotherapy regardless of the initial response to these treatment modalities (1). Of the chemotherapeutic agents used to treat glioblastoma, alkylating agents including O 6 -methylating agent temozolomide (TMZ) 5 are the most widely used. Despite the use of O 6 -methylating agents (TMZ for example) in glioblastoma therapy, the median survival times of patients suffering from the most severe form glioblastoma are still remarkably low (12-14 months). There is an urgent need for improving glioblastoma therapy. One goal that needs to be reached in achieving this would be to improve our knowledge of the mechanism of alkylating agent-induced death in glioblastoma cells (2). Here, we focus on AMPK, a recently discovered kinase that is involved in anti-tumor growth/survival effects (3-9).AMP-activated protein kinase (AMPK) is a metabolic-sensing protein kinase, which plays an essential role as an energysensor mainly in ATP-deprived conditions (10). In the activated states, AMPK down-regulates several anabolic enzymes and thus shuts down the ATP-consuming metabolic pathways. Interestingly, several recent reports have observed the strong pro-apoptotic potential of AMPK ...

for many years. Unlike glass ceramics, Y-TZP cannot be etched by hydrofluoric acid under normal conditions (room temperature and ambient atmosphere). [4] Thus, the roughness of Y-TZP surface is generally achieved by grit blasting.Y-TZP is unlikely to react with silane coupling agents because of its low SiO 2 content (less than 1%). [5,6] Thus, primers containing phosphate ester monomers are typically used in combination with alumina grit blasting to improve the chemical bonding between Y-TZP and resin. [7] Among them, 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) is most commonly used. However, the disadvantage of 10-MDP is that it cannot maintain long-term bonding stability in a complex oral environment (0-67 °C); [8] for example, the shear strength of 10-MDP after 10 000 thermocycles is ≈18.0 ± 3.7 MPa. [9] In addition to primers, the bonding strength of Y-TZP/resin has been also increased by depositing SiO 2 films combined with silane coupling agents. [10][11][12][13] Common methods used for SiO 2 film deposition include sol-gel, tribochemical SiO 2 coating, plasma spraying, and chemical vapor deposition; [14][15][16] although, all these methods have their drawbacks. First, the SiO 2 films are not firmly attached to the Y-TZP and thus are easily peeled off. Second, the coverage of the SiO 2 films on the surface of Y-TZP is insufficient and uneven, and the thickness of the films cannot be controlled. [17,18] Plasma spraying requires high temperatures (2700-11 700 °C), which take a long time to reach, and the procedure is relatively complex. [19] These drawbacks limit the clinical applications of SiO 2 film deposition on the bonding surface of Y-TZP prostheses.Atomic layer deposition (ALD) was first proposed by Suntola and Antson in 1977. [20] ALD may produce nanoscale films with high precision, [21] controllable thickness, and extreme uniformity. [22,23] ALD has already been widely used to deposit films on a variety of materials and is thus expected to overcome the drawbacks of other common SiO 2 film deposition methods because of the following ALD advantages. [24] 1. The films are deposited by gas-solid chemical reactions; thus, the films are firmly and stably bonded with the substrate. [25] The retentive strength of zirconia crowns is derived from resin cement, and the weak interface between the two is the main reason for their failure. In this work, nano-thin silica (SiO 2 ) films of precisely controlled thickness are deposited over yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics via atomic layer deposition (ALD). The deposited films are modified using a silane coupling agent, which significantly improves the bonding strength between Y-TZP and resin. Scanning electron microscopy shows that the SiO 2 films deposited by ALD are uniform and can accurately maintain the morphology of grit-blasted Y-TZP. Spectroscopic ellipsometry demonstrates that the films are nano-thin, with thicknesses in the range of 5.58-26.58 nm. The increase in the shear bond strength is attributed to the chemic...