Articles in 2012

Patrick Soon-Shiong has only one mode of thinking: big. The South Africa-born surgeon-scientist has founded two multi-billion-dollar pharmaceutical firms and is now setting his sights on transforming the entire US biomedical system with a modern, high-speed data network. Amber Dance sat down with Soon-Shiong to talk about how uniting physicians and scientists will surmount the most pressing challenges in biomedicine and cancer research.

Noise-induced hearing loss is caused primarily by damage to auditory hair cells; however, humans are unable to regenerate damaged hair cells, necessitating the development of new therapeutic strategies to protect auditory hair cells. A new study suggests that the use of phosphodiesterase 5 (PDE5) inhibitors may provide a protective therapeutic route for hearing loss (pages 252–259).

A newly identified role for SMAD specific E3 ubiquitin protein ligase 2 (Smurf2) in the regulation of histone ubiquitination uncovers a broad tumor suppressor activity that helps to maintain genomic stability in mice. A recent study suggests a new mechanism underlying the role of ubiquitination in cancer (pages 227–234).

Suicide is the third leading cause of death in the US among people under the age of 45. Yet psychiatrists know remarkably little about what treatments can most effectively prevent people from killing themselves. For the most part, investigators have shied away from studying the problem head-on because designing intervention studies with suicidal subjects is fraught with difficulty. Elie Dolgin talks to the small group of mental health professionals who are hoping to put an end to that.

Pathogens have remarkable abilities to flout therapeutic intervention. This characteristic is driven by evolution, either as a direct response to intervention (for example, the evolution of antibiotic resistance) or through long-term co-evolution that generates host or parasite traits that interact with therapy in undesirable or unpredicted ways. To make progress towards successful control of infectious diseases, the concepts and techniques of evolutionary biology must be deeply integrated with traditional approaches to immunology and pathogen biology. An interdisciplinary approach can inform our strategies to control pathogens or even the treatment of infected patients, positioning us to meet the current and future challenges of controlling infectious diseases.

T cell acute lymphoblastic leukemia (T-ALL) is an immature hematopoietic malignancy driven mainly by oncogenic activation of NOTCH1 signaling¹. In this study we report the presence of loss-of-function mutations and deletions of the EZH2 and SUZ12 genes, which encode crucial components of the Polycomb repressive complex 2 (PRC2)^2,3, in 25% of T-ALLs. To further study the role of PRC2 in T-ALL, we used NOTCH1-dependent mouse models of the disease, as well as human T-ALL samples, and combined locus-specific and global analysis of NOTCH1-driven epigenetic changes. These studies demonstrated that activation of NOTCH1 specifically induces loss of the repressive mark Lys27 trimethylation of histone 3 (H3K27me3)⁴ by antagonizing the activity of PRC2. These studies suggest a tumor suppressor role for PRC2 in human leukemia and suggest a hitherto unrecognized dynamic interplay between oncogenic NOTCH1 and PRC2 function for the regulation of gene expression and cell transformation.

Targeting mesenchymal stem cells (MSCs), progenitors of osteoblasts, to bone has been a long-standing goal but has had limited success so far. Here, Min Guan and her colleagues deliver a peptidomimetic integrin ligand against integrin α4β1 conjugated to the bone-seeking agent bisphosphonate alendronate as a means of attracting infused and/or endogenous MSCs to the bone surface to stimulate bone formation. The approach was tested in both xenotransplantation and immunocompetent mice, as well as in mouse models of trabecular bone loss induced by aging and estrogen deficiency (ovariectomy).

BMP7 has been previously shown to protect against renal fibrosis. Raghu Kalluri and his colleagues have now identified activin-like kinase 3 (Alk3) as the key co-receptor for BMP7 in the kidney and have identified an orally available, small-peptide agonist of Alk3 that reduces established fibrosis in five animal models of kidney injury.

Tau aggregation is associated with neurodegenerative diseases called tauopathies. Ashley Bush and colleagues now report that aged tau-deficient mice develop motor and cognitive dysfunction that is linked to elevated iron levels in the brains of the mice.

Zhang and colleagues have developed a new targeted delivery system for RNA interference–based bone anabolic therapy. Using dioleoyl trimethylammonium propane (DOTAP)-based cationic liposomes attached to six repetitive sequences of aspartate, serine, serine (AspSerSer)₆, the system provided selective enrichment of the encapsulated osteogenic siRNA in osteogenic lineage cells at the bone formation surface and the subsequent depletion of the target gene, encoding the bone formation inhibitor casein kinase-2 interacting protein-1 (PLEKHO1, also known as CKIP-1), leading to the promotion of bone formation in healthy and osteoporotic rats.

The role of T cells in modulating the course of influenza infection in humans is not clear. Wilkinson et al. now report that, in the absence of strain-specific humoral immunity, preexisting cytotoxic CD4⁺ T cells limit the severity and duration of symptoms in humans challenged with influenza virus and suggest these CD4⁺ T cell responses might be harnessed in vaccine development.

The ability of Mycobacterium leprae to upregulate miRNA-21 provides an effective mechanism for the pathogen to escape from the vitamin D–dependent antimicrobial pathway.

Mutations in isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) in the majority of people with grade 2 and 3 gliomas is associated with elevated levels of 2-hydroxyglutarate (2HG) within the tumor. As harboring IDH1 or IDH2 mutations confers a considerable survival benefit in these individuals, there has been considerable interest in studying this metabolite as a potential biomarker. Here, Changho Choi et al. report the successful noninvasive detection of 2HG in 30 subjects with gliomas using a proton magnetic resonance spectroscopy approach.

This report uncovers a direct link between cancer-driving inflammation and DNA methylation by showing that PGE₂ regulates the expression of DNA methylases, resulting in silencing of tumor-suppressor genes. The authors suggest that DNA methylation is an important component of the pathogenic effect of inflammatory signaling in colorectal cancer.

By modeling acquired resistance to the EGFR antibody cetuximab in metastatic colorectal cancer, the authors identify a new mutation in the ectodomain of the receptor. The mutation is present in patient tumors after cetuximab therapy, confirming that it represents a clinically-relevant mechanism for therapy resistance. Moreover, the mutation does not affect the response to other EGFR antibodies, suggesting that if independently confirmed it may be a useful indicator to tailor anti-EGFR therapy.

Kejia Cai et al. describe a method to non-invasively detect glutamate (Glu) concentrations in the brain with MRI at high resolution. The approach is based on the pH-dependent chemical exchange saturation transfer (CEST) effect between the amino group of Glu and bulk water and offers advantages over proton magnetic resonance spectroscopy. Feasibility of GluCEST was demonstrated in rat brain after middle cerebral artery occlusion stroke and in a rat brain tumor model, as well as in healthy human brain at 7 Tesla.

Noise-induced hearing loss (NIHL) is a prevalent problem in the industrialized world. Now, Lukas Rüttiger and colleagues show that the phosphodiesterase inhibitor vardenafil can prevent NIHL in rats and mice.

Using mice with an amino substitution in the kinase PKG, a key regulator of blood vessel tone, Oleksandra Prysyazhna et al. provide evidence for the physiological importance of PKG oxidation and disulfide formation in maintaining normal blood pressure. These results clarify the nature of an enigmatic vasodilatory activity termed endothelium-derived hyperpolarizing factor and suggest that vascular oxidative stress can have blood pressure-lowering effects.

Protective T helper 2 (T_H2)-type responses are induced by parasite infection and can control inflammation and induce parasite expulsion. In this issue, Chen et al. report that in a mouse model of helminth infection, T_H2-type responses protect against acute lung tissue damage by both suppressing inflammation and promoting macrophage-associated wound healing.

Cidea is typically thought of as a lipid droplet–associated cytoplasmic protein in brown adipose tissue. Peng Li and colleagues now show that it is also in the nucleus, and in mammary gland epithelial cells it acts as an essential transcriptional coactivator of C/EBPβ to regulate the expression of genes involved in milk lipid secretion during lactation.