A study on DNA methylation status in promoter region of p15 gene in patients of acute myeloid leukemia and myelodysplastic syndrome

BackgroundAcute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) are a spectrum of hematological malignancies with a multistep process of accumulated genetic and epigenetic alterations. DNA methylation is most extensively studied epigenetic alteration in malignancies. Recent research studies in the field have brought out translational implications of promoter methylation of tumor suppressor gene p15 in tumors. Therefore, we studied the role of DNA Methylation of p15 gene in AML and MDS.MethodsThe study was carried out in 41 consecutive AML/MDS cases reporting to hematological OPD of a tertiary care center along with 25 age and sex-matched healthy controls. The methylation status in the promoter region of the p15 gene was assessed by methylation-specific PCR (MSP) from blood samples after ethical approval and informed consent of the patients and controls. The association of methylation status was studied with clinical presentations, AML subtypes, and cytogenetics using Chi-square test/Fisher''s exact test tools.ResultsA total of 41 cases included in the study comprised 33 cases of AML and 08 cases of MDS with an age range between 06 months and 82 years. Of the 41 cases, 29 revealed promoter methylation of the p15 gene, which compared to healthy controls was found statistically significant (p < 0.001). The methylation status did not significantly correlate with AML subtypes or the cytogenetic abnormalities detected in cases.ConclusionThe outcome of the study indicates p15 promoter DNA methylation in cases of AML and MDS may identify those individuals who might benefit from the targeted therapeutic approaches.     

Characterization of two mutations, M287L and Q266I, in the α1 glycine receptor subunit that modify sensitivity to alcohols

Glycine receptors (GlyRs) are inhibitory ligand-gated ion channels. Ethanol potentiates glycine activation of the GlyR, and putative binding sites for alcohol are located in the transmembrane (TM) domains between and within subunits. To alter alcohol sensitivity of GlyR, we introduced two mutations in the GlyR α1 subunit, M287L (TM3) and Q266I (TM2). After expression in Xenopus laevis oocytes, both mutants showed a reduction in glycine sensitivity and glycine-induced maximal currents. Activation by taurine, another endogenous agonist, was almost abolished in the M287L GlyR. The ethanol potentiation of glycine currents was reduced in the M287L GlyR and eliminated in Q266I. Physiological levels of zinc (100 nM) potentiate glycine responses in wild-type GlyR and also enhance the ethanol potentiation of glycine responses. Although zinc potentiation of glycine responses was unchanged in both mutants, zinc enhancement of ethanol potentiation of glycine responses was absent in M287L GlyRs. The Q266I mutation decreased conductance but increased mean open time (effects not seen in M287L). Two lines of knockin mice bearing these mutations were developed. Survival of homozygous knockin mice was impaired, probably as a consequence of impaired glycinergic transmission. Glycine showed a decreased capacity for displacing strychnine binding in heterozygous knockin mice. Electrophysiology in isolated neurons of brain stem showed decreased glycine-mediated currents and decreased ethanol potentiation in homozygous knockin mice. Molecular models of the wild-type and mutant GlyRs show a smaller water-filled cavity within the TM domains of the Q266I α1 subunit. The behavioral characterization of these knockin mice is presented in a companion article (J Pharmacol Exp Ther 340:317-329, 2012).     

Dietary phytochemicals induce p53- and caspase-independent cell death in human neuroblastoma cells

Neuroblastoma (NB) is the most prevalent pediatric solid tumor and a leading cause of cancer-related death in children. In the present study, a novel cytotoxic role for the dietary compounds, curcumin, andrographolide, wedelolactone, dibenzoylmethane, and tanshinone IIA was identified in human S-type NB cells, SK-N-AS and SK-N-BE(2). Mechanistically, cell death appeared apoptotic by flow cytometry; however, these effects proceeded independently from both caspase-3 and p53 activation, as assessed by both genetic (shRNA) and pharmacological approaches. Notably, cell death induced by both curcumin and andrographolide was associated with decreased NFκB activity and a reduction in Bcl-2 and Bcl-xL expression. Finally, curcumin and andrographolide increased cytotoxicity following co-treatment with either cisplatin or doxorubicin, two chemotherapeutic agents widely used in the clinical management of NB. Coupled with the documented safety in humans, dietary compounds may represent a potential adjunct therapy for NB.     

Corrosion protection and improved cytocompatibility of biodegradable polymeric layer-by-layer coatings on AZ31 magnesium alloys

Composite coatings of electrostatically assembled layer-by-layer anionic and cationic polymers combined with an Mg(OH)₂ surface treatment serve to provide a protective coating on AZ31 magnesium alloy substrates. These ceramic conversion coating and layer-by-layer polymeric coating combinations reduced the initial and long-term corrosion progression of the AZ31 alloy. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful application of coatings. Potentiostatic polarization tests indicate improved initial corrosion resistance. Hydrogen evolution measurements over a 2 week period and magnesium ion levels over a 1 week period indicate longer range corrosion protection and retention of the Mg(OH)₂ passivation layer in comparison to the uncoated substrates. Live/dead staining and DNA quantification were used as measures of biocompatibility and proliferation while actin staining and scanning electron microscopy were used to observe the cellular morphology and integration with the coated substrates. The coatings simultaneously provided improved biocompatibility, cellular adhesion and proliferation in comparison to the uncoated alloy surface utilizing both murine pre-osteoblast MC3T3 cells and human mesenchymal stem cells. The implementation of such coatings on magnesium alloy implants could serve to improve the corrosion resistance and cellular integration of these implants with the native tissue while delivering vital drugs or biological elements to the site of implantation.