Dual anticancer role of metformin: an old drug regulating AMPK dependent/independent pathways in metabolic, oncogenic/tumorsuppresing and immunity context.

Metformin has been known to treat type 2 diabetes for decades and is widely prescribed antidiabetic drug. Recently, its anticancer potential has also been discovered. Moreover, metformin has low cost thus it has attained profound research interest. Comprehensing the complexity of the molecular regulatory networks in cancer provides a mode for advancement of research in cancer development and treatment. Metformin targets many pathways that play an important role in cancer cell survival outcome. Here, we described anticancer activity of metformin on the AMPK dependent/independent mechanisms regulating metabolism, oncogene/tumor suppressor signaling pathways together with the issue of clinical studies. We also provided brief overwiev about recently described metformin's role in cancer immunity. Insight in these complex molecular networks, will simplify application of metformin in clinical trials and contribute to improvement of anti-cancer therapy.

Protective effect of autophagy in laser-induced glioma cell death in vitro.

BACKGROUND AND OBJECTIVE: Laser phototherapy could be potentially used for cancer treatment, but the mechanisms of laser-induced cell death are not completely understood. Autophagy is the process in which the damaged cellular proteins and organelles are engulfed by and destroyed in acidified multiple-membrane vesicles. The aim of the present study was to investigate the role of autophagy in laser-induced tumor cell death in vitro. STUDY DESIGN/MATERIALS AND METHODS: The monolayers of U251 human glioma tumor cells were exposed to 532 nm laser light from a single mode frequency-doubled Nd-YVO4 laser. A flattened Gaussian radial profile of laser beam (0.5-4 W) was used to uniformly illuminate entire colony of cells for various amounts of time (15-120 seconds) in the absence of cell culture medium. The cells were grown for 24 hours and the cell viability was determined by crystal violet or MTT assay. The presence of autophagy was assessed after 16 hours by fluorescence microscopy/flow cytometric analysis of acridine orange-stained autophagolysosomes and Western blot analysis of the autophagosome-associated LC3-II protein. The concentration of the principal pro-autophagic protein beclin-1 was determined after 6 hours by cell-based ELISA. RESULTS: The intracytoplasmic accumulation of autophagic vesicles, increase in LC3-II and up-regulation of beclin-1 expression were clearly observed under irradiation conditions that caused approximately 50% cytotoxicity. Post-irradiation addition of three different autophagy inhibitors (bafilomycin A1, chloroquine, or wortmannin) further increased the laser-induced cytotoxicity, without affecting non-irradiated cells. CONCLUSIONS: These data indicate that beclin-1-dependent induction of autophagy can protect glioma cells from laser-mediated cytotoxicity.

Opposite effects of nanocrystalline fullerene (C(60)) on tumour cell growth in vitro and in vivo and a possible role of immunosupression in the cancer-promoting activity of C(60).

In the present study, we compared the effects of nanocrystalline fullerene suspension (nanoC(60)) on tumour cell growth in vitro and in vivo. NanoC(60) suspension was prepared by solvent exchange using tetrahydrofuran to dissolve C(60). In vitro, nanoC(60) caused oxidative stress, mitochondrial depolarization and caspase activation, leading to apoptotic and necrotic death in mouse B16 melanoma cells. Biodistribution studies demonstrated that intraperitoneally injected radiolabeled (125I) nanoC(60) readily accumulated in the tumour tissue of mice subcutaneously inoculated with B16 cells. However, intraperitoneal administration of nanoC(60) over the course of two weeks starting from melanoma cell implantation not only failed to reduce, but significantly augmented tumour growth. The tumour-promoting effect of nanoC(60) was accompanied by a significant increase in splenocyte production of the immunoregulatory free radical nitric oxide (NO), as well as by a reduction in splenocyte proliferative responses to T- and B-cell mitogens ConcanavalinA and bacterial lipopolysaccharide, respectively. A negative correlation between NO production and splenocyte proliferation indicated a possible role of NO in reducing the proliferation of splenocytes from nanoC(60)-injected mice. These data demonstrate that nanoC(60), in contrast to its potent anticancer activity in vitro, can potentiate tumour growth in vivo, possibly by causing NO-dependent suppression of anticancer immune response.

The protection of cells from nitric oxide-mediated apoptotic death by mechanochemically synthesized fullerene (C(60)) nanoparticles.

The influence of fullerene (C(60)) nanoparticles on the cytotoxicity of a highly reactive free radical nitric oxide (NO) was investigated. Fullerene nanoparticles were prepared by mechanochemically assisted complexation with anionic surfactant sodium dodecyl sulfate, macrocyclic oligosaccharide gamma-cyclodextrin or the copolymer ethylene vinyl acetate-ethylene vinyl versatate. C(60) nanoparticles were characterized by UV-vis and atomic force microscopy. While readily internalized by mouse L929 fibroblasts, C(60) nanoparticles were not cytotoxic. Moreover, they partially protected L929 cells from the cytotoxic effect of NO-releasing compounds sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), S-nitrosoglutathione (GSNO) and 3-morpholino-sydnonimine (SIN-1). C(60) nanoparticles reduced SNP-induced apoptotic cell death by preventing mitochondrial depolarization, caspase activation, cell membrane phosphatidylserine exposure and DNA fragmentation. The protective action of C(60) nanoparticles was not exerted via direct interaction with NO, but through neutralization of mitochondria-produced superoxide radical in NO-treated cells, as demonstrated by using different redox-sensitive reporter fluorochromes. These data suggest that C(60) complexes with appropriate host molecules might be plausible candidates for preventing NO-mediated cell injury in inflammatory/autoimmune disorders.