天然来源抗肿瘤化合物作用于MAPK通路的机制

天然来源抗肿瘤活性产物是抗肿瘤药物先导化合物的重要资源。促分裂原活化蛋白激酶(MAPK)通路是细胞内重要的信号转导系统,可以调节细胞的生长、凋亡、黏附、迁移等过程,继而影响肿瘤的发生、发展、侵袭、转移,是潜在的抗肿瘤药物作用靶点之一。本文将对天然来源化合物作用于MAPK信号通路的靶点分子及生物效应进行阐述,为肿瘤的化学预防及治疗提供启发。     

A Novel Statistic for Genome-Wide Interaction Analysis

Although great progress in genome-wide association studies (GWAS) has been made, the significant SNP associations identified by GWAS account for only a few percent of the genetic variance, leading many to question where and how we can find the missing heritability. There is increasing interest in genome-wide interaction analysis as a possible source of finding heritability unexplained by current GWAS. However, the existing statistics for testing interaction have low power for genome-wide interaction analysis. To meet challenges raised by genome-wide interactional analysis, we have developed a novel statistic for testing interaction between two loci (either linked or unlinked). The null distribution and the type I error rates of the new statistic for testing interaction are validated using simulations. Extensive power studies show that the developed statistic has much higher power to detect interaction than classical logistic regression. The results identified 44 and 211 pairs of SNPs showing significant evidence of interactions with FDR<0.001 and 0.001<FDR<0.003, respectively, which were seen in two independent studies of psoriasis. These included five interacting pairs of SNPs in genes LST1/NCR3, CXCR5/BCL9L, and GLS2, some of which were located in the target sites of miR-324-3p, miR-433, and miR-382, as well as 15 pairs of interacting SNPs that had nonsynonymous substitutions. Our results demonstrated that genome-wide interaction analysis is a valuable tool for finding remaining missing heritability unexplained by the current GWAS, and the developed novel statistic is able to search significant interaction between SNPs across the genome. Real data analysis showed that the results of genome-wide interaction analysis can be replicated in two independent studies.     

Polymorphisms of the DNA repair gene MGMT and risk and progression of head and neck cancer

Methylating agents are involved in carcinogenesis, and the DNA repair protein O⁶-methylguanine-DNA methyltransferase (MGMT) removes methyl group from O⁶-methylguanine. Genetic variation in DNA repair genes has been shown to contribute to susceptibility to squamous cell carcinoma of the head and neck (SCCHN). We hypothesize that MGMT polymorphisms are associated with risk of SCCHN. In a hospital-based case–control study of 721 patients with SCCHN and 1234 cancer-free controls frequency-matched by age, sex and ethnicity, we genotyped four MGMT polymorphisms, two in exon 3, 16195C > T and 16286C > T and two in the promoter region, 45996G > T and 46346C > A. We found that none of these polymorphisms alone had a significant effect on risk of SCCHN. However, when these four polymorphisms were evaluated together by the number of putative risk genotypes (i.e. 16195CC, 16286CC, 45996GT + TT, and 46346CA + AA), a statistically significantly increased risk of SCCHN was associated with the combined genotypes with three to four risk genotypes, compared with those with zero to two risk genotypes (adjusted odds ratio (OR) = 1.27; 95% confidence interval (CI) = 1.05–1.53). This increased risk was also more pronounced among young subjects (OR = 1.81; 95% CI = 1.11–2.96), men (OR = 1.24; 95% CI = 1.00–1.55), ever smokers (OR = 1.25; 95% = 1.01–1.56), ever drinkers (OR = 1.29; 95% CI = 1.04–1.60), patients with oropharyngeal cancer (OR = 1.45; 95% CI = 1.12–1.87), and oropharyngeal cancer with regional lymph node metastasis (OR = 1.52; 95% CI = 1.16–1.89). In conclusion, our results suggest that any one of MGMT variants may not have a substantial effect on SCCHN risk, but a joint effect of several MGMT variants may contribute to risk and progression of SCCHN, particularly for oropharyngeal cancer, in non-Hispanic whites.     

In Vitro Degradation of Insulin-like Peptide 3 by Insulin-degrading Enzyme

Insulin-like peptide 3 (INSL3) is an insulin superfamily peptide hormone, primarily expressed in the testes and playing a key role in the fetus testes descent and suppression of male germ cell apoptosis. Insulin-degrading enzyme (IDE) is a zinc-metalloprotease, responsible for in vivo degradation of insulin, Aβ, and other peptide hormones. IDE has high expression level in the testes, implying it might be involved in INSL3 turnover in vivo. In present work, we studied in vitro degradation of INSL3 by IDE. Recombinant human IDE degraded human INSL3, but its degradation rate for INSL3 is more than a magnitude lower than that for insulin. However, IDE bound INSL3 and insulin with almost same affinity. IDE cleaved the peptide bond between B26R and B27W of INSL3, and released a pentapeptide, WSTEA, from the C-terminal of B-chain. Our present work suggested that IDE might play a role in INSL3 degradation in vivo.     

An Analysis of Reentrant Loops

Reentrant loops are an important structural motif in alpha-helical transmembrane proteins. A reentrant loop is a structural motif that goes only halfway through the membrane and then turns back to the side from which it originates. The question of what causes the reentrant loops to form such a unique topology is still unanswered. In this study, we try to answer this question by analyzing the hydrophobicity distribution on the amino acid sequences of the reentrant loops. Our results show that reentrant loops have very low hydrophobicity around the deepest point buried in the membrane and relative high hydrophobicity close to the membrane surfaces. We speculate that this hydrophobicity distribution is a major force that stabilizes the unique reentrant loop structure. Our results also show that this hydrophobicity distribution results in special patterns on protein sequences, which can be captured using profile hidden Markov models (HMMs). The resulting profile HMMs can detect reentrant loops on protein sequences with high sensitivity and perfect specificity.     

Chemical composition and antidiabetic activity of Opuntia Milpa Alta extracts

Three new compounds, 1 – 3 , and 20 known compounds were isolated from the AcOEt and BuOH extract of edible Opuntia Milpa Alta. The petroleum ether extract was examined by GC and MS. A total of 26 compounds were identified, representing 95.6% of the total extract, phytosterol (36.03%) being the most abundant component, and polyunsaturated fatty acids (18.57%) represented the second largest group, followed by phytol (12.28%), palmitic acid, palmitate (13.54%), vitamin E (4.51%), and other compounds (7.47%). The effects of various extracts from edible Opuntia Milpa Alta (petroleum ether extract, AcOEt extract, BuOH extract, aqueous extract, H₂O parts) and the positive control (received dimethylbiguanide) were tested on streptozotocin (STZ)‐induced diabetic mice. The results indicated that all the treatment groups could significantly decrease blood glucose levels in STZ‐induced diabetic mice compared to the model control group (P<0.01), except the aqueous extract group (P<0.05). Especially, the petroleum ether extract group and the positive control group showed remarkable decrease of blood glucose levels. Taken together, the results indicate that the petroleum ether extract is the major hypoglycemic part in edible Opuntia Milpa Alta, which may be developed to a potential natural hypoglycemic functional ingredient.     

Electrochemical recognition for sugars on the chitosan-poly(diallyldimethylammonium chloride)-nano-Prussian blue/nano-Au/4-mercaptophenylboronic acid modified glassy carbon electrode

A new amperometric biosensor for the detection of sugars was prepared. A glassy carbon electrode was modified with Prussian blue (PB) nanoparticles protected by chitosan (CS) and poly(diallyldimethylammonium chloride) (PDDA), and then gold nanoparticles were assembled onto the electrode followed by the assembly of 4-mercaptophenylboronic acid (MPBA) onto the surface of gold nanoparticles through a sulfur–Au bond to fabricate a self-assembled biosensor. The PB nanoparticles protected by CS and PDDA were characterized using transmission electron microscopy and UV–vis absorption spectroscopy. The characterization of the self-assembled electrode was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The pK _a values of the MPBA monolayer before and after combining with sugars were determined. The fabricated electrode exhibited excellent performances for determining d(+)-glucose, d(+)-mannose, and d(−)-fructose on the basis of the change in i _p of the Fe(CN)₆^3−/4− ion in the presence of sugars.     

An ordered EST catalogue and gene expression profiles of cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis>) at key growth stages

A cDNA library was constructed from the root tissues of cassava variety Huanan 124 at the root bulking stage. A total of 9,600 cDNA clones from the library were sequenced with single-pass from the 5′-terminus to establish a catalogue of expressed sequence tags (ESTs). Assembly of the resulting EST sequences resulted in 2,878 putative unigenes. Blastn analysis showed that 62.6% of the unigenes matched with known cassava ESTs and the rest had no ‘hits’ against the cassava database in the integrative PlantGDB database. Blastx analysis showed that 1,715 (59.59%) of the unigenes matched with one or more GenBank protein entries and 1,163 (40.41%) had no ‘hits’. A cDNA microarray with 2,878 unigenes was developed and used to analyze gene expression profiling of Huanan 124 at key growth stages including seedling, formation of root system, root bulking, and starch maturity. Array data analysis revealed that (1) the higher ratio of up-regulated ribosome-related genes was accompanied by a high ratio of up-regulated ubiquitin, proteasome-related and protease genes in cassava roots; (2) starch formation and degradation simultaneously occur at the early stages of root development but starch degradation is declined partially due to decrease in UDP-glucose dehydrogenase activity with root maturity; (3) starch may also be synthesized in situ in roots; (4) starch synthesis, translocation, and accumulation are also associated probably with signaling pathways that parallel Wnt, LAM, TCS and ErbB signaling pathways in animals; (5) constitutive expression of stress-responsive genes may be due to the adaptation of cassava to harsh environments during long-term evolution.