Synthesis and biological effects of NO in malignant glioma cells: modulation by cytokines including CD95L and TGF-β dexamethasone, and p53 gene transfer

Abstract

Nitric oxide (NO) is thought to play an important role in neurotransmission, in¯ammation, and regulation of cell death in the mammalian brain. Here, we examined the synthesis and biological e ects of NO in human malignant glioma cells. Exposure to cytokines such as interferon (IFN)-g, tumor necrosis factor (TNF)-a or interleukin (IL)-1b and lipopolysaccharide (LPS) induced NO synthesis in rat C6 and A172 human glioma cells, but not in LN-229, T98G or LN-18 human malignant glioma cells. Induced release of NO involved enhanced expression of inducible NO synthase (iNOS). Failure to detect NO release in the latter cell lines was not overcome by neutralization of endogenous TGF-b or by coexposure to cytokines, LPS, and antioxidants. Apoptosis induced by CD95 ligand (CD95L) did not involve NO formation. Neither NOS inhibitors nor NO donators modulated CD95L-induced apoptosis. Dexamethasone (DEX)-mediated protection of glioma cells from CD95L-induced apoptosis was also independent of DEX e ects on NO metabolism. DEX inhibited not only cytokine/ LPS-evoked NO release but also attenuated the toxicity of NO in three of ®ve cell lines. Forced expression of temperature-sensitive p53 val 135 in C6 cells in either mutant or wild-type conformation inhibited cytokine/LPS-induced NO synthesis. Further, accumulation of p53 in both mutant or wild-type conformation protected glioma cells from the toxicity of exogenous NO, consistent with a gain of p53 function associated with p53 accumulation. We conclude that resistance to NO-dependent immune defense mechanisms may contribute to the malignant progression of human cancers with p53 alterations, notably those associated with the accumulation of mutant p53 protein.

Adenovirus-mediated interferon-β gene therapy suppresses growth and metastasis of human prostate cancer in nude mice

“…Interestingly, similar observations were made in another tumor system, in which induction of tumor regression by bacterial products was associated with a decrease in TGF -1 and an increase in NO in tumors. 56,57 It is noteworthy that orthotopic PC3MM2 tumors were more susceptible to AdIFN -therapy than were their subcutaneous counterparts. Although it is not clear what caused this differential susceptibility, this observation cautions that experimental therapeutic studies for prostate cancer should be performed in the orthotopic organ.…”

TNF‐α‐ and TRAIL‐resistant glioma cells undergo autophagy‐dependent cell death induced by activated microglia

“…Expression of the inducible nitric oxide synthase (iNOS) and subsequent production of nitric oxide (NO) has been reported in some glioma cell lines exposed to LPS and IFN-g (Rieger et al, 1998). To investigate the possible involvement of NO in the toxicity mediated by LPS/IFN-g and/or SN1, the killing efficiency of these latter was tested in the presence of L-NIL, an inhibitor of iNOS.…”

Proteasome Inhibitors Induce p53/p21-Independent Apoptosis in Human Glioma Cells

“…Transfected cells were maintained at 38.5°C. Expression of the transfected p53 gene was confirmed by immunoblot analysis [10].…”

“…To further analyze the role of p53 in MG132 cytotoxicity, we took advantage of LN-229 expressing the transdominant-negative p53val 135 mutant which blocks camptothecin-induced, p53-mediated p21 accumulation in these cells [17]. This mouse mutant is temperature-sensitive and a functional mutant at 38.5°C but assumes p53 wild-type properties at 32.5°C in malignant glioma cells [10]. Interestingly, transdominant-negative mutant p53val 135 (38.5°C) prevented the accumulation of p21 induced by MG132 at 0.5 ÌM but did not abrogate the MG132-induced p21 accumulation at higher concentrations ( fig.…”