Mice deficient in CuZn superoxide dismutase (CuZn-SOD) showed no overt abnormalities during development and early adulthood, but had a reduced lifespan and increased incidence of neoplastic changes in the liver. Greater than 70% of Sod1À/À mice developed liver nodules that were either nodular hyperplasia or hepatocellular carcinoma (HCC). Cross-sectional studies with livers collected from Sod1À/À and age-matched þ / þ controls revealed extensive oxidative damage in the cytoplasm and, to a lesser extent, in the nucleus and mitochondria from as early as 3 months of age. A marked reduction in cytosolic aconitase, increased levels of 8-oxo dG and F2-isoprostanes, and a moderate reduction in glutathione peroxidase activities and porin levels were observed in all age groups of Sod1À/À mice examined. There were also age-related reductions in Mn superoxide dismutase activities and carbonic anhydrase III. Parallel to the biochemical changes, there were progressive increases in the DNA repair enzyme APEX1, the cell cycle control proteins cyclin D1 and D3, and the hepatocyte growth factor receptor Met. Increased cell proliferation in the presence of persistent oxidative damage to macromolecules likely contributes to hepatocarcinogenesis later in life.

Sod2-/- mice, which are deficient in the mitochondrial form of superoxide dismutase (MnSOD), have a short survival time that is strongly affected by genetic background. This suggests the existence of genetic modifiers that are capable of modulating the degree of mitochondrial oxidative damage caused by the MnSOD deficiency, thereby altering longevity. To identify these modifier(s), we generated recombinant congenic mice with quantitative trait loci (QTL) containing the putative genetic modifiers on the short-lived C57BL/6J genetic background. MnSOD deficient C57BL/6J mice with a QTL from the distal region of chromosome 13 from DBA/2J were able to survive for as long as those generated on the long-lived DBA/2J background. Within this region, the gene encoding nicotinamide nucleotide transhydrogenase (Nnt) was found to be defective in C57BL/6J mice, and no mature NNT protein could be detected. The forward reaction of NNT, a nuclear-encoded mitochondrial inner membrane protein, couples the generation of NADPH to proton transport and provides NADPH for the regeneration of two important antioxidant compounds, glutathione and thioredoxin, in the mitochondria. This action of NNT could explain its putative protective role in MnSOD-deficient mice.

MYC overexpression has been implicated in the pathogenesis of most types of human cancers. MYC is likely to contribute to tumorigenesis by its effects on global gene expression. Previously, we have shown that the loss of MYC overexpression is sufficient to reverse tumorigenesis. Here, we show that there is a precise threshold level of MYC expression required for maintaining the tumor phenotype, whereupon there is a switch from a gene expression program of proliferation to a state of proliferative arrest and apoptosis. Oligonucleotide microarray analysis and quantitative PCR were used to identify changes in expression in 3,921 genes, of which 2,348 were down-regulated and 1,573 were up-regulated. Critical changes in gene expression occurred at or near the MYC threshold, including genes implicated in the regulation of the G1-S and G2-M cell cycle checkpoints and death receptor/apoptosis signaling. Using two-dimensional protein analysis followed by mass spectrometry, phospho-flow fluorescence-activated cell sorting, and antibody arrays, we also identified changes at the protein level that contributed to MYC-dependent tumor regression. Proteins involved in mRNA translation decreased below threshold levels of MYC. Thus, at the MYC threshold, there is a loss of its ability to maintain tumorigenesis, with associated shifts in gene and protein expression that reestablish cell cycle checkpoints, halt protein translation, and promote apoptosis.

Statins are a class of drugs that inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMGcoA) reductase, a critical enzyme in the mevalonate pathway. Several reports document that statins may prevent different human cancers. However, whether or not statins can prevent cancer is controversial due to discordant results. One possible explanation for these conflicting conclusions is that only some tumors or specific statins may be effective. Here, we demonstrate in an in vivo transgenic model in which atorvastatin reverses and prevents the onset of MYC-induced lymphomagenesis, but fails to reverse or prevent tumorigenesis in the presence of constitutively activated K-Ras (G12D). Using phosphoprotein fluorescence-activated cell sorter (FACS) analysis, atorvastatin treatment was found to result in the inactivation of the Ras and ERK1/2 signaling pathways associated with the dephosphorylation and inactivation of MYC. Correspondingly, tumors with a constitutively activated K-Ras (G12D) did not exhibit dephosphorylation of ERK1/2 and MYC. Atorvastatin's effects on MYC were specific to the inhibition of HMGcoA reductase, as treatment with mevalonate, the product of HMG-CoA reductase activity, abrogated these effects and inhibited the ability of atorvastatin to reverse or suppress tumorigenesis. Also, RNAi directed at HMGcoA reductase was sufficient to abrogate the neoplastic properties of MYC-induced tumors. IntroductionCancer is largely caused by genomic events which result in the activation of oncogenes or the loss of tumor-suppressor genes. 1 The targeted inactivation of oncogenes may be a specific and effective therapy for treating certain malignancies. 2,3 Experimental results in animal models validate the notion that the targeted inactivation of a single oncogene can be sufficient to reverse tumorigenesis. 4 Drugs that target specific proteins have been identified and shown to be effective in the treatment of certain cancers, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] which indicates that some neoplasms are susceptible to therapies that target their molecular causes. However, cancers can escape dependence upon oncogenes, as observed in animal models as well as in human patients. [21][22][23] Thus, the best targets may not be the suspected oncogenes but rather proteins essential to multiple signaling or metabolic pathways required for tumor maintenance.MYC is one of the oncogenes most commonly associated with human cancer. 24 Experimentally, the inactivation of MYC has been shown to induce sustained tumor regression in transgenic mouse models of many different tumors, suggesting that MYC may be a good target for cancer treatment. [25][26][27][28] However, MYC as a transcription factor is not easy to target directly with small molecules. Thus, rather than directly targeting MYC, it might be possible to inactivate MYC through the disruption of upstream regulatory signaling molecules such as those in pathways regulated by Ras and ERK1/2. 29,30 The enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMGcoA) r...

BackgroundDetection of single cell epitopes has been a mainstay of immunophenotyping for over three decades, primarily using fluorescence techniques for quantitation. Fluorescence has broad overlapping spectra, limiting multiplexing abilities.Methodology/Principal FindingsTo expand upon current detection systems, we developed a novel method for multi-color immuno-detection in single cells using “Composite Organic-Inorganic Nanoparticles” (COINs) Raman nanoparticles. COINs are Surface-Enhanced Raman Scattering (SERS) nanoparticles, with unique Raman spectra. To measure Raman spectra in single cells, we constructed an automated, compact, low noise and sensitive Raman microscopy device (Integrated Raman BioAnalyzer). Using this technology, we detected proteins expressed on the surface in single cells that distinguish T-cells among human blood cells. Finally, we measured intracellular phosphorylation of Stat1 (Y701) and Stat6 (Y641), with results comparable to flow cytometry.Conclusions/SignificanceThus, we have demonstrated the practicality of applying COIN nanoparticles for measuring intracellular phosphorylation, offering new possibilities to expand on the current fluorescent technology used for immunoassays in single cells.