RAD51 potentiates synergistic effects of chemotherapy with PCI-24781 and cis-diamminedichloroplatinum on gastric cancer

AIM:To explore the efficacy of PCI-24781,a broadspectrum,hydroxamic acid-derived histone deacetylase inhibitor,in the treatment of gastric cancer(GC).METHODS:With or without treatment of PCI-24781and/or cis-diamminedichloroplatinum(CDDP),GC cell lines were subjected to functional analysis,including cell growth,apoptosis and clonogenic assays.Chromatin immunoprecipitation and luciferase reporter assays were used to determine the interacting molecules and the activity of the enzyme.An in vivo study was carried out in GC xenograft mice.Cell culture-based assays were represented as mean±SD.ANOVA tests were used to assess differences across groups.All pairwise comparisons between tumor weights among treatment groups were made using the Tukey-Kramer method for multiple comparison adjustment to control experimental-wise typeⅠ error rates.Significance was set at P<0.05.RESULTS:PCI-24781 significantly reduced the growth of the GC cells,enhanced cell apoptosis and suppressed clonogenicity,and these effects synergized with the effects of CDDP.PCI-24781 modulated the cell cycle and significantly reduced the expression of RAD51,which is related to homologous recombination.Depletion of RAD51 augmented the biological functions of PCI-24781,CDDP and the combination treatment,whereas overexpressing RAD51 had the opposite effects.Increased binding of the transcription suppressor E2F4 on the RAD51 promoter appeared to play a major role in these processes.Furthermore,significant suppression of tumor growth and weight in vivo was obtained following PCI-24781 treatment,which synergized with the anticancer effect of CDDP.CONCLUSION:These data suggest that RAD51 potentiates the synergistic effects of chemotherapy with PCI-24781 and CDDP on GC.

Dietary Conjugated Linoleic Acids Arrest Cell Cycle Progression and Prevent Ovarian Cancer Xenografts Growth Suggesting a Trans-10 Cis-12 Isoform Specific Activity

Therapies for treating ovarian cancer (OvCa) successfully are largely inadequate. Alternative therapies and diet(s) with preventive potential to debilitated onset, and reduced OvCa tumor burden in situ, have not been systematically studied. Preventive role of conjugated linoleic acids (CLAs) has been reported in many other cancers. We report the first systematic in vitro and in vivo study modeling potential preventive mechanism(s) of CLA, an octadecadienolic fatty acid in clear cell OvCa cell line TOV-21G. We demonstrate that a dose and time-dependent down-regulation of cyclin E and A proteins (p 0.05) by CLA (t10,c12) was concomitant with cell cycle arrest of TOV-21G cell lines in S phase. To understand the molecular mechanism underlying CLA (t10,c12) induced S phase arrest, levels of cell cycle regulatory proteins were determined by western blot analyses. Exposure to CLA (t10,c12) increased p21(CIP1/WAF1), and p27(KIP1) protein levels in a time and dose-dependent manner. Interestingly CLA (t10,c12) did not significantly affect protein levels of cyclin-dependent kinase (cdk) 2, and p53, however, hyperphosphorylated form of pRb (p 0.05) was abrogated. Exposure to CLA (c9,t11) indicated a modest increase in p21(CIP1/WAF1) and p27(KIP1) levels, but changes in cyclin A and E levels were statistically insignificant. These results indicate that CLA (t10,c12) mediated p27(KIP1) upregulation and inhibition of hyperphosphorylation of ppRb may be the possible mechanism for the S phase arrest in TOV-21G cell line. Our in vivo data showed that CLA reduced the progression of TOV-21G xenografts by >50%. Together our results provide evidence of CLA exerted preventive effect on OvCa cell and tumor growth. Tumor growth arrest may be resultant from CLA (t10,c12) mediated modulation of cell cycle arrest.

Oral Symptoms and Bone Observations in Odonto-Hypophosphatasia

Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutation of the gene encoding tissue non-specific alkaline phosphatase (TNSALP). Odonto-HPP is well known as the mildest of HPP. The manifestations involve only the teeth, such as premature primary teeth exfoliation caused by reduction of alveolar bone, enlarged dental pulp chamber, and dental defects. We report a case of a 9-years-old boy who developed HPP. He was observed from the primary dentition to the mixed dentition period. At initial presentation at our hospital, he had multiple premature exfoliation of primary teeth and reduction of the alveolar bone. HPP was suspected due to the low level of ALP activity in serum, his oral manifestation, and dental history. He was referred to a physician for the final diagnosis. Therefore his compound heterozygote mutations, c.1559 delT (T/delT) and c.407G > A (G/A), were found in TNSALP and he diagnosed with odonto-HPP. Even though these mutations were reported as being involved in odonto-HPP, his mineral densities tended to be lower than that of his age. It is therefore necessary to investigate the bone mineralization level in odonto-HPP without other bone symptoms. Moreover, ongoing enzyme-replacement therapy in odonto-HPP might improve dental abnormality and bone disorders.

Deubiquitinating enzyme regulation of the p53 pathway: A lesson from Otub1

Deubiquitination has emerged as an important mechanism of p53 regulation. A number of deubiquitinating enzymes(DUBs) from the ubiquitin-specific protease family have been shown to regulate the p53-MDM2-MDMX networks. We recently reported that Otub1, a DUB from the OTU-domain containing protease family, is a novel p53 regulator. Interestingly, Otub1 abrogates p53 ubiquitination and stabilizes and activates p53 in cells independently of its deubiquitinating enzyme activity. Instead, it does so by inhibiting the MDM2 cognate ubiquitin-conjugating enzyme(E2) UbcH5. Otub1 also regulates other biological signaling through this non-canonical mechanism, suppression of E2, including the inhibition of DNA-damage-induced chromatin ubiquitination. Thus, Otub1 evolves as a unique DUB that mainly suppresses E2 to regulate substrates. Here we review the current progress made towards the understanding of the complex regulation of the p53 tumor suppressor pathway by DUBs, the biological function of Otub1 including its positive regulation of p53, and the mechanistic insights into how Otub1 suppresses E2.

Role of calcium in polycystic kidney disease:From signaling to pathology

Autosomal dominant polycystic kidney disease （ADPKD） is the most common inherited monogenic kidney disease. Characterized by the development and growth of cysts that cause progressive kidney enlargement, it ultimately leads to end-stage renal disease. Approximately 85% of ADPKD cases are caused by mutations in the PKD1 gene, while mutations in the PKD2 gene account for the remaining 15% of cases. The PKD1 gene encodes for polycystin-1 （PC1）, a large multi-functional memb-rane receptor protein able to regulate ion channel complexes, whereas polycystin-2 （PC2）, encoded by the PKD2 gene, is an integral membrane protein that functions as a calcium-permeable cation channel, located mainly in the endoplasmic reticulum （ER）. In the primary cilia of the epithelial cells, PC1 interacts with PC2 to form a polycystin complex that acts as a mechanosensor, regulating signaling pathways involved in the differentiation of kidney tubular epithelial cells. Despite progress in understanding the function of these proteins, the molecular mechanisms associated with the pathogenesis of ADPKD remain unclear. In this review we discuss how an imbalance between functional PC1 and PC2 proteins may disrupt calcium channel activities in the cilium, plasma membrane and ER, thereby altering intracellular calcium signaling and leading to the aberrant cell proliferation and apoptosis associated with the development and growth of renal cysts. Research in this feld could lead to the discovery of new molecules able to rebalance intracellular calcium, thereby normalizing cell proliferation and reducing kidney cyst progression.

Novel Y-chromosome Short Tandem Repeat Variants Detected Through the Use of Massively Parallel Sequencing

Massively parallel sequencing （MPS） technology is capable of determining the sizes of short tandem repeat （STR） alleles as well as their individual nueleotide sequences. Thus, single nucleotide polymorphisms （SNPs） within the repeat regions of STRs and variations in the pattern of repeat units in a given repeat motif can be used to differentiate alleles of the same length. In this study, MPS was used to sequence 28 forensically-relevant Y-chromosome STRs in a set of 41 DNA samples from the 3 major U.S. population groups （African Americans, Caucasians, and Hispanics）. The resulting sequence data, which were analyzed with STRait Razor v2.0, revealed 37 unique allele sequence variants that have not been previously reported. Of these, 19 sequences were variations of documented sequences resulting from the presence of intra-repeat SNPs or alternative repeat unit patterns. Despite a limited sampling, two of the most frequently-observed variants were found only in African American samples. The remaining 18 variants represented allele sequences for which there were no published data with which to compare. These findings illustrate the great potential of MPS with regard to increasing the resolving power of STR typing and emphasize the need for sample population characterization of STR alleles.

Biallelic mutations in UGDH cause congenital microcephaly

Hengel et al recently reported that bi-allelic loss-of-function mutations in UDP-Glucose 6-Dehydrogenase(UGDH)caused a severe epileptic encephalopathy syndrome-Jamuar syndrome(OMIM#618792).1 The functional studies partially recapitulated the clinical phenotypes in the patient-derived cerebral organoid.A reduced number of proliferating neuronal progenitors in cerebral organoids was shown,which is a critical mechanism in congenital microcephaly(CM)whose patients were born with an occipitofrontal circumference(OCF)more than 2 standard deviations below average for age and sex.However,none of the reported patients in the article presented the phenotype as CM.

Modulation of tau phosphorylation by environmental copper

Background:The transition metal copper enhances amyloidβaggregation and neurotoxicity,and in models of concomitant amyloid and tau pathology,copper also promotes tau aggregation.Since it is not clear if the effects of environmental copper upon tau pathology are dependent on the presence of pathological amyloidβ,we tested the effects of copper overload and complexing in disease models which lack pathological amyloidβ.Methods:We used cell culture and transgenic murine models to test the effects of environmental copper on tau phosphorylation.We used oral zinc acetate as a copper lowering agent in mice and examined changes in blood and brain metals through inductively coupled plasma mass spectroscopy.Behavioral effects of copper lowering were assessed with Morris water maze and novel object recognition tasks.Changes in tau phosphorylation were examined by phosphorylation specific antibodies on Western blots.Results:In human neuroblastoma cells,excess copper promoted tau phosphorylation and a copper complexing agent,tetrathiomolybdate,attenuated tau phosphorylation.In a transgenic mouse model expressing wild type human tau,copper-lowering by oral zinc suppressed plasma and brain levels of copper,and resulted in a marked attenuation of tau phosphorylation.No significant changes in behavior were observed with copper lowering,but a trend to improved recognition of the novel object was observed in zinc acetate treated mice.Conclusions:We propose that reduction of brain copper by blocking uptake of copper from the diet may be a viable strategy for modulating tau pathology in Alzheimer’s disease.The potential benefits of this approach are tempered by the absence of a behavioral benefit and by the health risks of excessive lowering of copper.

Diversity of Gene Expression in Hepatocellular Carcinoma Cells

Understanding tumor diversity has been a long-lasting and challenging question for researchers in the field of cancer heterogeneity or tumor evolution. Studies have reported that com- pared to normal cells, there is a higher genetic diversity in tumor cells, while higher genetic diversity is associated with higher progression risks of tumor. We thus hypothesized that tumor diversity also holds true at the gene expression level. To test this hypothesis, we used t-test to compare the means of Simpson＇s diversity index for gene expression （SDIG） between tumor and non-tumor samples. We found that the mean SDIG in tumor tissues is significantly higher than that in the non-tumor or normal tissues （P 〈 0.05） for most datasets. We also combined microarrays and next-generation sequencing data for validation. This cross-platform and cross-experimental validation greatly increased the reliability of our results.