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Background Hyperoxia is a well-known cause of cerebral white matter injury in preterm infants with male sex being an independent and critical risk factor for poor neurodevelopmental outcome. Sex is therefore being widely considered as one of the major decisive factors for prognosis and treatment of these infants. But unfortunately, we still lack a clear view of the molecular mechanisms that lead to such a profound difference. Hence, using mouse-derived primary oligodendrocyte progenitor cells (OPCs), we investigated the molecular factors and underlying mechanisms behind the differential response of male and female cells towards oxidative stress. Results We demonstrate that oxidative stress severely affects cellular functions related to energy metabolism, stress response, and maturation in the male-derived OPCs, whereas the female cells remain largely unaffected. CNPase protein level was found to decline following hyperoxia in male but not in female cells. This impairment of maturation was accompanied by the downregulation of nucleoporin and nuclear lamina proteins in the male cells. We identify Nup133 as a novel target protein affected by hyperoxia, whose inverse regulation may mediate this differential response in the male and female cells. Nup133 protein level declined following hyperoxia in male but not in female cells. We show that nuclear respiratory factor 1 (Nrf1) is a direct downstream target of Nup133 and that Nrf1 mRNA declines following hyperoxia in male but not in female cells. The female cells may be rendered resistant due to synergistic protection via the estrogen receptor alpha (ERα) which was upregulated following hyperoxia in female but not in male cells. Both Nup133 and ERα regulate mitochondrial function and oxidative stress response by transcriptional regulation of Nrf1. Conclusions These findings from a basic cell culture model establish prominent sex-based differences and suggest a novel mechanism involved in the differential response of OPCs towards oxidative stress. It conveys a strong message supporting the need to study how complex cellular processes are regulated differently in male and female brains during development and for a better understanding of how the brain copes up with different forms of stress after preterm birth.

Hepatocellular carcinoma (HCC) is a frequent and deadly disease worldwide. The absence of effective therapies when the tumor is surgically unresectable leads to an extremely poor outcome of HCC patients. Thus, it is mandatory to elucidate the molecular pathogenesis of HCC in order to develop novel therapeutic strategies against this pernicious tumor. Mounting evidence indicates that suppression of the DNA damage response machinery might be deleterious for the survival and growth of the tumor cells. In particular, DNA dependent protein kinase catalytic subunit (DNA-PKcs), a major player in the non-homologous end-joining (NHEJ) repair process, seems to represent a valuable target for innovative anti-neoplastic therapies in cancer. DNA-PKcs levels are strongly upregulated and associated with a poor clinical outcome in various tumor types, including HCC. Importantly, DNA-PKcs not only protects tumor cells from harmful DNA insults coming either from the microenvironment or chemotherapeutic drug treatments, but also possesses additional properties, independent from its DNA repair activity, that provide growth advantages to cancer cells. These properties (metabolic and gene reprogramming, invasiveness and metastasis, resistance to apoptosis, etc.) have started to be elucidated. In the present review, we summarize the physiologic and oncogenic roles of DNA-PKcs, with a special emphasis on liver cancer. In particular, this work focuses on the molecular mechanism whereby DNA-PKcs exerts its pro-tumorigenic activity in cancer cells. In addition, the upstream regulator of DNA-PKcs activation as well as its downstream effectors thus far identified are illustrated. Furthermore, the potential therapeutic strategies aimed at inhibiting DNA-PKcs activity in HCC are discussed.

The present study identified a novel mechanism of induction of apoptosis in glioblastoma cells by scriptaid – a histone deacetylase (HDAC) inhibitor. Scriptaid reduced glioma cell viability by increasing Jun N-terminal kinase (JNK) activation. Although scriptaid induced activation of both p38MAPK and JNK, it was the inhibition of JNK that attenuated scriptaid-induced apoptosis significantly. Scriptaid also increased the expression of (i) p21 and p27 involved in cell-cycle regulation and (ii) γH2AX associated with DNA damage response in a JNK-dependent manner. Treatment with scriptaid increased Ras activity in glioma cells, and transfection of cells with constitutively active RasV12 further sensitized glioma cells to scriptaid-induced apoptosis. Scriptaid also inhibited telomerase activity independent of JNK. Taken together, our findings indicate that scriptaid (i) induces apoptosis and reduces glioma cell proliferation by elevating JNK activation and (ii) also decreases telomerase activity in a JNK-independent manner.

Background & Aims Cumulating evidence underlines the crucial role of aberrant lipogenesis in human hepatocellular carcinoma (HCC). Here, we investigated the oncogenic potential of fatty acid synthase (FASN), the master regulator of de novo lipogenesis, in the mouse liver. Methods FASN was overexpressed in the mouse liver, either alone or in combination with activated N-Ras, c-Met, or SCD1, via hydrodynamic injection. Activated AKT was overexpressed via hydrodynamic injection in livers of conditional FASN or Rictor knockout mice. FASN was suppressed in human hepatoma cell lines via specific small interfering RNA. Results Overexpression of FASN , either alone or in combination with other genes associated with hepatocarcinogenesis, did not induce histological liver alterations. In contrast, genetic ablation of FASN resulted in the complete inhibition of hepatocarcinogenesis in AKT -overexpressing mice. In human HCC cell lines, FASN inactivation led to a decline in cell proliferation and a rise in apoptosis, which were paralleled by a decrease in the levels of phosphorylated/activated AKT, an event controlled by the mammalian target of rapamycin complex 2 (mTORC2). Downregulation of AKT phosphorylation/activation following FASN inactivation was associated with a strong inhibition of rapamycin-insensitive companion of mTOR (Rictor), the major component of mTORC2, at post-transcriptional level. Finally, genetic ablation of Rictor impaired AKT-driven hepatocarcinogenesis in mice. Conclusions FASN is not oncogenic per se in the mouse liver, but is necessary for AKT-driven hepatocarcinogenesis. Pharmacological blockade of FASN might be highly useful in the treatment of human HCC characterized by activation of the AKT pathway.

Resistance to tumor necrosis factor (TNFalpha)-induced apoptosis in various cancer cells has been attributed to the activation of the transcription factor NF-kappaB. Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]one)-a selenoorganic compound is known to prevent TNFalpha-mediated NF-kappaB activity. As glioblastoma are resistant to the cytotoxic effect of TNFalpha, we investigated the potential of Ebselen in sensitizing glioma cells to TNFalpha-induced apoptosis. Although treatment with Ebselen reduced viability of glioma cells, cotreatment with TNFalpha enhanced apoptosis further through alteration of TNFalpha-mediated signaling pathways. Sensitization of TNFalpha activated glioma cells to apoptosis by Ebselen involved 2 pathways: (i) abrogation of TNFalpha induced NF-kappaB activation and (ii) induction of Fas-associated death inducing signaling complex (DISC) formation. Ebselen inhibited the prosurvival pathway mediated by NF-kappaB by altering the association of TNF receptor associated factor 2 (TRAF2) with TNFalpha receptor associated death domain (TRADD) in the TNFR1-TRADD-TRAF2 complex -an interaction crucial for mediating NF-kappaB activity. Ebselen also induced the formation of DISC involving Fas, Fas-associated death domain (FADD) and active caspase 8 to transduce apoptotic signals in situations where NF-kappaB function was inhibited. Cotreatment with Ebselen and TNFalpha induced G2/M phase arrest in cell cycle and modulated the expression of molecules involved in cell cycle progression. These results raise the possibility of overcoming resistance to TNFalpha-induced apoptosis by cotreatment with organoselenium Ebselen as a strategy to kill glioma cells.

Polyphenol epigallocatechin-3-gallate (EGCG) induced apoptosis in glioma cells by elevating oxidative stress through increased reactive oxygen species (ROS) generation. Signs of apoptosis included altered mitochondrial membrane potential and elevated expression of caspase-3 and cytochrome c. The increase in ROS was concomitant with the decrease in expression of thioredoxin (TRX-1) and ceruloplasmin (CP), mediators associated with protection against oxidative stress. EGCG downregulated the levels of pro-inflammatory cytokine interleukin (IL)-6 and chemokines IL-8, monocyte-chemoattractant protein (MCP)-1 and RANTES. EGCG also decreased the invasive potential of gliomas, possibly by affecting the urokinase plasminogen activator (uPA) and cytoskeletal architecture. Our study indicates that EGCG might serve as an effective therapeutic strategy against glioma as it not only promotes cell death through redox perturbation, but also downregulates the release of pro-inflammatory mediators while concomitantly decreasing the invasive potential of glioma cells.

Despite recent advances in understanding molecular mechanisms involved in glioblastoma progression, the prognosis of the most malignant brain tumor continues to be dismal. Because the flavonoid kaempferol is known to suppress growth of a number of human malignancies, we investigated the effect of kaempferol on human glioblastoma cells. Kaempferol induced apoptosis in glioma cells by elevating intracellular oxidative stress. Heightened oxidative stress was characterized by an increased generation of reactive oxygen species (ROS) accompanied by a decrease in oxidant-scavenging agents such as superoxide dismutase (SOD-1) and thioredoxin (TRX-1). Knockdown of SOD-1 and TRX-1 expression by small interfering RNA (siRNA) increased ROS generation and sensitivity of glioma cells to kaempferol-induced apoptosis. Signs of apoptosis included decreased expression of Bcl-2 and altered mitochondrial membrane potential with elevated active caspase-3 and cleaved poly(ADP-ribose) polymerase expression. Plasma membrane potential and membrane fluidity were altered in kaempferol-treated cells. Kaempferol suppressed the expression of proinflammatory cytokine interleukin-6 and chemokines interleukin-8, monocyte chemoattractant protein-1, and regulated on activation, normal T-cell expressed and secreted. Kaempferol inhibited glioma cell migration in a ROS-dependent manner. Importantly, kaempferol potentiated the toxic effect of chemotherapeutic agent doxorubicin by amplifying ROS toxicity and decreasing the efflux of doxorubicin. Because the toxic effect of both kaempferol and doxorubicin was amplified when used in combination, this study raises the possibility of combinatorial therapy whose basis constitutes enhancing redox perturbation as a strategy to kill glioma cells. [Mol Cancer Ther 2007;6(9):2544–53]