Expression of anti-SRP19 antibody in muscle tissues from patients with autoimmune necrotizing myopathy

This study aimed to investigate the role of anti-SRP19 antibody in muscle tissues of patients with autoimmune necrotizing myopathy. Immunohistochemistry staining was used to determine the expression of anti-SRP19 antibodies in muscle tissues of autoimmune necrotizing myopathy patients. Results demonstrated that anti-SRP19 antibody was expressed in 71.4% (20/28) of muscle tissue specimens from patients with autoimmune necrotizing myopathy. Anti-SRP19 antibody expression was mainly localized in cytoplasm of necrotic muscle fibers surrounding the small blood vessels and interstitial cells. There were no significant differences in the age, course of disease, muscle, and creatine kinase levels between patients with positive or negative expression of anti-SRP19 antibodies. The expression levels of anti-SRP19, serum anti-nuclear antibodies, as well as anti-Ro-52, anti- SSA, anti-Sm, and anti-Jo-1 antibodies were not significantly different among groups. This study demonstrates that anti-SRP19 antibody is highly expressed in muscle tissues of patients with autoimmune necrotizing myopathy, and suggests that this protein may be involved in the origin and progression of the disease.

[The roles of serum free light chain ratio in the diagnosis and prognosis of newly diagnosed multiple myeloma]

目的

分析血清游离轻链（sFLC）κ/λ比率（sFLCR）在初诊多发性骨髓瘤（MM）患者诊断和预后中的作用。

方法

回顾性分析2012年9月至2015年7月收治的82例初诊MM患者的临床资料，采用血清蛋白电泳（SPE）和免疫固定电泳（IFE）法检测血清单克隆蛋白（M蛋白）的表达，采用免疫比浊法检测sFLCκ、λ的表达水平，分析初诊时sFLCR在MM患者诊断和预后中的作用。

结果

初诊时82例患者中SPE法检测M蛋白阳性率为85.5%，IFE法检测M蛋白阳性率为93.9%，sFLC异常以及sFLCR异常者占96.3%。初诊时高比率组（sFLCR≥100或≤0.01，42例）与低比率组（0.01 <sFLCR<100，40例）患者40个月的总生存率分别为87％和61%，差异有统计学意义（P=0.034）。与低比率组患者比较，高比率组患者初诊时血肌酐值、浆细胞数、β₂微球蛋白增高，血红蛋白降低，肾功能不全及需要透析者、DS分期Ⅲ期B组者、ISS分期Ⅲ期者、FISH检查异常者、λ轻链异常者较多，κ轻链异常者较少（P值均<0.05）。两组患者经过3~4个疗程诱导治疗后，高比率组和低比率组患者的治疗有效率（非常好的部分缓解及其以上）差异有统计学意义（45.2％对72.5%，P=0.012）。初诊肾功能不全者（肌酐≥178 µmol/L, 14例）与肾功能正常者（68例）的2年总生存率差异无统计学意义（85.7％对91.2%，P=0.894）。

结论

初诊时sFLC的检测相对于SPE和IFE法检测M蛋白对诊断MM有更高的敏感性；初诊时sFLCR明显异常的患者可能具有更高的肿瘤负荷和更强的侵袭性，可提示患者预后不良；初诊时伴有肾功能不全的MM患者经积极治疗后可获得与肾功能正常患者同样的疗效。

Genome-wide identification and evolutionary analysis of nucleotide-binding site-encoding resistance genes in Lotus japonicus (Fabaceae)

Nucleotide-binding site (NBS) disease resistance genes play a crucial role in plant defense responses against pathogens and insect pests. Many NBS-encoding genes have been detected in Lotus japonicus, an important forage crop in many parts of the world. However, most NBS genes identified so far in L. japonicus were only partial sequences. We identified 45 full-length NBS-encoding genes in the L. japonicus genome, and analyzed gene duplications, motifs, and the molecular phylogeny to further understand the NBS gene family. We found that gene duplication events rarely occur in L. japonicus NBS-encoding (LjNBS) genes. In addition, LjNBS genes were subjected to selection pressure, and codon usage bias was evident. We tested for purifying selection (specifically in the CC-NBS-LRR and TIR-NBS-LRR groups), and found strong purifying selection in the TIR-domain-containing sequences, indicating that the CC-NBS-LRR group is more likely to undergo expansion than the TIR-NBS-LRR group. Moreover, our results showed that both selection and mutation contributed to LjNBS codon usage bias, but mutational bias was the major influence on codon usage.

A novel glucose 6-phosphate isomerase from Listeria monocytogenes

D-Arabinose 5-phosphate isomerases (APIs) catalyze the interconversion of D-ribulose 5-phosphate and D-arabinose 5-phosphate (A5P). A5P is an intermediate in the biosynthesis of 3-deoxy-D-manno-octulosonate (Kdo), an essential component of lipopolysaccharide, the lipopolysaccharide found in the outer membrane of Gram-negative bacteria. The genome of the Gram-positive pathogen Listeria monocytogenes contains a gene encoding a putative sugar isomerase domain API, Q723E8, with significant similarity to c3406, the only one of four APIs from Escherichia coli CFT073 that lacks a cystathionine-β-synthase domain. However, L. monocytogenes lacks genes encoding any of the other enzymes of the Kdo biosynthesis pathway. Realizing that the discovery of an API in a Gram-positive bacterium could provide insight into an alternate physiological role of A5P in the cell, we prepared and purified recombinant Q723E8. We found that Q723E8 does not possess API activity, but instead is a novel GPI (D-glucose 6-phosphate isomerase). However, the GPI activity of Q723E8 is weak compared with previously described GPIS. L. monocytogenes contains an ortholog of the well-studied two-domain bacterial GPI, so this maybe redundant. Based on this evidence glucose utilization is likely not the primary physiological role of Q723E8.

Heparin-functionalized collagen matrices with controlled release of basic fibroblast growth factor

Tissue engineering scaffolds with controlled long-term release of growth factors are constructed in an attempt to mimic the intelligent ability of the extracellular matrix (ECM) to release endogenous growth factors. In this study, collagen sponges (Collagen group) were modified by N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) crosslinking (EDC/NHS group) and heparin immobilization (EDC/NHS-H group), and subsequently seeded with human umbilical vein endothelial cells (HUVECs). Native and modified sponges were pre-adsorbed with basic fibroblast growth factor (bFGF) to evaluate the sustained release and bioactive maintenance of bFGF from the sponges. We found that modified collagen matrices permitted HUVECs to proliferate and migrate well and to distribute uniformly. The EDC/NHS-H group exhibited an excellent sustained-release profile and bioactive maintenance of the pre-adsorbed bFGF as compared with the Collagen and EDC/NHS groups. These results suggest that heparin-functionalized collagen matrices can support a controlled release of bFGF and thus, have potential as a tissue engineering scaffold.

Integrated biomarker response index for the assessment of environmental stress of the Yangtze River (Nanjing section)

In the present study, multibiomarker effects of the river water of three representative sections in Nanjing section of the Yangtze River were investigated in goldfish (Carassius auratus). The organic toxicants were extracted from the water samples using solid phase extraction. Acetylcholinesterase (AChE), glutathione-S-transferase (GST), 7-ethoxyresorufin-O-deethylase (EROD), glutathione peroxidase (GPx) and Na+/K+-ATPase activities were determined after exposure of the extracted components. The fractions of water samples from three sections (Daqiao, Sanchahe and Jiangxinzhou) altered these enzymatic activities. With the change of the extracts polarity, the levels of AChE, GST, EROD, Na+/K+-ATPase activities were different. The responses of enzymatic activities were mostly significant for those exposures of intermediate polar components (50-80% methanol extracts) and weakly polar components (ether and ether/hexane extracts). It has been shown that toxicants were mainly concentrated in these fractions in the Yangtze River (Nanjing section). With regard to response for different sections, EROD and GST activities seem to be more sensitive biomarkers. Integrated biomarker response index (IBR) were calculated and used to evaluate an integrated impact of pollutants from different sampling sections. The order of negative biological effects of the three sections was Jiangxinzhou>Sanchahe>Daqiao. The wild fish living in Nanjing section of the Yangtze River were at potential ecological risk.

Adult hepatic cavernous haemangioma with highly elevated alpha-fetoprotein

A 35-year-old Chinese man presented with dull pain in the right hypochondrial region for the previous 2 months. Laboratory examination revealed that his serum alpha-fetoprotein level was 1890 microg/L (reference range, 0-20 microg/L), and computed tomographic scan showed a hypodense lesion in the left liver lobe. At laparotomy, a dark reddish soft tumour (3.0 x 3.5 cm in diameter) was found in the medial segment of the liver (segment III). The tumour became markedly smaller than that before resection, and a vessel-like structure was found on the cut surface. Intra-operative pathology and postoperative histopathology examinations revealed that the tumour was a cavernous haemangioma of the liver. The serum alpha-fetoprotein level decreased to 3.5 microg/L by the fourth postoperative week. Clinicians should be aware that some rare tumours besides hepatocellular carcinoma and endodermal sinus tumours (yolk sac tumour), for example, hepatic haemangioma, can produce alpha-fetoprotein.

Tunable electrical properties of silicon nanowires via surface-ambient chemistry

p-Type surface conductivity is a uniquely important property of hydrogen-terminated diamond surfaces. In this work, we report similar surface-dominated electrical properties in silicon nanowires (SiNWs). Significantly, we demonstrate tunable and reversible transition of p(+)-p-i-n-n(+) conductance in nominally intrinsic SiNWs via changing surface conditions, in sharp contrast to the only p-type conduction observed on diamond surfaces. On the basis of Si band energies and the electrochemical potentials of the ambient (pH value)-determined adsorbed aqueous layer, we propose an electron-transfer-dominated surface doping model, which can satisfactorily explain both diamond and silicon surface conductivity. The totality of our observations suggests that nanomaterials can be described as a core-shell structure due to their large surface-to-volume ratio. Consequently, controlling the surface or shell in the core-shell model represents a universal way to tune the properties of nanostructures, such as via surface-transfer doping, and is crucial for the development of nanostructure-based devices.

Clinical and economic impact of infusion reactions in patients with colorectal cancer treated with cetuximab

Background: Systemic agents in cancer treatment were often associated with possible infusion reactions (IRs). This study estimated the incidence of IRs requiring medical intervention and assessed the clinical and economic impacts of IRs in patients with colorectal cancer (CRC) treated with cetuximab.

Patients and methods: Details on patients with CRC receiving cetuximab in 2004–2006 were extracted from a large USA administrative claims database. IRs were identified based on the occurrence of outpatient treatment, emergency room (ER) visit, and/or hospitalization for hypersensitivity and allergic reactions. Multivariate regressions were used to examine potential risk factors and quantify the economic impact of IRs.

Results: A total of 1122 CRC patients receiving cetuximab were identified. The incidence of IRs requiring medical intervention was 8.4%. Sixty-eight percent of the patients had treatment disruptions and 34% discontinued cetuximab treatment. Mean adjusted costs were $13 863 for cetuximab administrations with an IR requiring ER visit or hospitalization and $6280 for those with an IR requiring outpatient treatment, compared with $4555 for those without an IR.

Conclusions: The incidence rate of cetuximab-related IRs requiring medical intervention in clinical practice was found to be higher than rates reported in the product label and clinical trials. The clinical and economic impacts of these IRs are substantial.

Joint toxicity evaluation and QSAR modeling of aromatic amines and phenols to bacteria

Acute toxicity of aromatic amines and phenols and their mixtures to bacteria in natural waters was determined and the median inhibition concentration IC(50) values for single compounds and IC(50mix) values for binary and multiple mixtures were obtained. Based on the quantitative structure-activity relationship model for single chemical toxicity, a two-descriptor model accounting for n-octanol/water partition coefficient (log P(mix)) and the energy of the lowest unoccupied molecular orbital (E(LUMOmix)) was developed for the toxicity of a mixture: log(1/IC(50mix) = 0.326 log P(mix) - 0.660E(LUMOmix) + 3.323 (n = 32, R(2) = 0.834). This model can be used successfully to predict the toxicity of a mixture, whether binary mixtures or multiple mixtures of three or four chemicals are used as predictors.

p-Type ZnO nanowire arrays

Well-aligned ZnO nanowire (NW) arrays with durable and reproducible p-type conductivity were synthesized on alpha-sapphire substrates by using N2O as a dopant source via vapor-liquid-solid growth. The nitrogen-doped ZnO NWs are single-crystalline and grown predominantly along the [110] direction, in contrast to the [001] direction of undoped ZnO NWs. Electrical transport measurements reveal that the nondoped ZnO NWs exhibit n-type conductivity, whereas the nitrogen-doped ZnO NWs show compensated highly resistive n-type and finally p-type conductivity upon increasing N2O ratio in the reaction atmosphere. The electrical properties of p-type ZnO NWs are stable and reproducible with a hole concentration of (1-2) x 10(18) cm(-3) and a field-effect mobility of 10-17 cm2 V(-2) s(-1). Surface adsorptions have a significant effect on the transport properties of NWs. Temperature-dependent PL spectra of N-doped ZnO NWs show acceptor-bound-exciton emission, which corroborates the p-type conductivity. The realization of p-type ZnO NWs with durable and controlled transport properties is important for fabrication of nanoscale electronic and optoelectronic devices.

Removal of COD(Cr) and nitrogen in severely polluted river water by bank filtration

Laboratory column experiments on the colmation layer and a three-year successive field observation at the Xucun and Huangqiao sections of the Kui River--a severely polluted river in the Huai River basin in China--have been carried out. The transport and removal ratios for COD(Cr), NH4- -N, and NO3- -N in river water infiltrated through the riverbed colmation layer, the unsaturated zone, and the saturated aquifer, as well as to the pumping well, were investigated. The results of the column tests show that the colmation laver can effectively clog the infiltration of water and contaminants and the non-conservative contaminants can be effectively adsorbed or degraded by riverbed microbes in the colmation layer and its sludge. The removal ratios were approximately 48-51% for COD(Cr) and NH4- -N, and 23.5-25.5% for NO3- -N. Field observations indicate that the colmation layer and the unsaturated zone possess an obvious capacity to adsorb and degrade contaminants. A significant accumulation could be identified at the interface between the unsaturated and saturated zones. In the saturated zone of groundwater, contaminant concentrations declined sharply and were very low at the pumping well. Additionally, one- and two-dimensional numerical models were used to simulate the transport and transformation processes of water and contaminants filtered through the unsaturated zone and the saturated zone, and the model equations were solved numerically with a fully implicit difference method. The good agreement between calculated and measured values suggests the feasibility and reliability of the simulation method.

Exploring the role of the active site cysteine in human muscle creatine kinase

All known guanidino kinases contain a conserved cysteine residue that interacts with the non-nucleophilic eta1-nitrogen of the guanidino substrate. Site-directed mutagenesis studies have shown that this cysteine is important, but not essential for activity. In human muscle creatine kinase (HMCK) this residue, Cys283, forms part of a conserved cysteine-proline-serine (CPS) motif and has a pKa about 3 pH units below that of a regular cysteine residue. Here we employ a computational approach to predict the contribution of residues in this motif to the unusually low cysteine pKa. We calculate that hydrogen bonds to the hydroxyl and to the backbone amide of Ser285 would both contribute approximately 1 pH unit, while the presence of Pro284 in the motif lowers the pKa of Cys283 by a further 1.2 pH units. Using UV difference spectroscopy the pKa of the active site cysteine in WT HMCK and in the P284A, S285A, and C283S/S285C mutants was determined experimentally. The pKa values, although consistently about 0.5 pH unit lower, were in broad agreement with those predicted. The effect of each of these mutations on the pH-rate profile was also examined. The results show conclusively that, contrary to a previous report (Wang et al. (2001) Biochemistry 40, 11698-11705), Cys283 is not responsible for the pKa of 5.4 observed in the WT V/K(creatine) pH profile. Finally we use molecular dynamics simulations to demonstrate that, in order to maintain the linear alignment necessary for associative inline transfer of a phosphoryl group, Cys283 needs to be ionized.

Heterogeneity of Escherichia coli -expressed human muscle creatine kinase

Creatine kinase (CK) plays an important role in maintaining a constant ATP:ADP ratio during periods of high energy usage. Elevated levels of CK give an early indication of myocardial infarction. The enzyme has four major isozymes with heterogeneity being observed for each of them. In many cases the source of the heterogeneity is unclear. However, some of the isoforms are known to result from exposure to serum proteases, and analysis of the plasma isoforms provides an estimate of the time of onset of the infarction. Somewhat surprisingly, isoelectric focusing (IEF) experiments provided evidence of heterogeneity in human muscle CK (HMCK) expressed in E. coli. To investigate this further, HMCK was purified to apparent homogeneity utilizing Blue Sepharose affinity chromatography and HiPrep Q anion exchange chromatography. Additional purification on a PBE 94 chromatofocusing column resulted in four fractions, three of which, HMCK I - III, were characterized. The three isoforms are all active and have similar kinetic parameters. They exhibited identical bands on SDS PAGE but different anodal mobility on non-denaturing gels. Modification of C-terminal and/or cysteine residues has been ruled out, and deamidation of asparagine or glutamine residue(s) is proposed to be the cause of isoform formation. In addition each of these isoforms showed a similar four-band pattern on a carrier ampholytes-based IEF gel. Two-dimensional IEF analysis showed that an equilibrium was established between the four bands, suggesting that the four components were unstable and generated only when the protein was subjected to IEF.

Loop movement and catalysis in creatine kinase

Recently the crystal structure of creatine kinase from Torpedocalifornica was determined to 2.1 A. The dimeric structure revealed two different forms in the unit cell: one monomer was bound to a substrate, MgADP, and the other monomer was bound to a transition-state analogue complex composed of MgADP, nitrate and creatine. The most striking difference between the structures is the movement of two loops (comprising residues 60-70 and residues 323-333) into the active site in the transition state structure. This loop movement effectively occludes the active site from solvent, and the loops appear to be locked into place by a salt bridge formed between His66 and Asp326. His66 is of particular interest as it is located within a PGHP motif conserved in all creatine kinases but not found in other guanidino kinases. We have carried out alanine-scanning mutagenesis of each of the residues in the PGHP motif and determined that only the His66 plays a significant role in the creatine kinase reaction. Although neither residue interacts directly with the substrate, the interaction His66 and Asp326 appears to be important in providing the precise alignment of substrates necessary for phosphoryl group transfer. Finally, it is clear that neither His66 nor Asp326 are responsible for the pKs observed in the pH-rate profile for HMCK.

HRPT2, a tumor suppressor gene for hyperparathyroidism-jaw tumor syndrome

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is a familial multi-tumor syndrome resulting from inactivating mutations in the HRPT2 tumor suppressor gene, which encodes a protein product named parafibromin. Here, we will review recent advances in genetic and protein studies on parafibromin, and examine its biological functions.

Isoleucine 69 and valine 325 form a specificity pocket in human muscle creatine kinase

Creatine kinase (CK) catalyzes the reversible phosphorylation of creatine by ATP. From a structural perspective, the enzyme utilizes two flexible loop regions to sequester and position the substrates for catalysis. There has been debate over the specific roles of the flexible loops in substrate specificity and catalysis in CK and other related phosphagen kinases. In CK, two hydrophobic loop residues, I69 and V325, make contacts with the N-methyl group of creatine. In this study, we report the alteration of the substrate specificity of CK through the mutagenesis of V325. The V325 to glutamate mutation results in a more than 100-fold preference for glycocyamine, while mutation of V325 to alanine results in a slight preference of the enzyme for cyclocreatine (1-carboxymethyl-2-iminoimidazolidine). This study enhances our understanding of how the active sites of phosphagen kinases have evolved to recognize their respective substrates and catalyze their reactions.

The 2.1 A structure of Torpedo californica creatine kinase complexed with the ADP-Mg(2+)-NO(3)(-)-creatine transition-state analogue complex

Creatine kinase (CK) catalyzes the reversible conversion of creatine and ATP to phosphocreatine and ADP, thereby helping maintain energy homeostasis in the cell. Here we report the first X-ray structure of CK bound to a transition-state analogue complex (CK-TSAC). Cocrystallization of the enzyme from Torpedo californica (TcCK) with ADP-Mg(2+), nitrate, and creatine yielded a homodimer, one monomer of which was liganded to a TSAC complex while the second monomer was bound to ADP-Mg(2+) alone. The structures of both monomers were determined to 2.1 A resolution. The creatine is located with the guanidino nitrogen cis to the methyl group positioned to perform in-line attack at the gamma-phosphate of ATP-Mg(2+), while the ADP-Mg(2+) is in a conformation similar to that found in the TSAC-bound structure of the homologue arginine kinase (AK). Three ligands to Mg(2+) are contributed by ADP and nitrate and three by ordered water molecules. The most striking difference between the substrate-bound and TSAC-bound structures is the movement of two loops, comprising residues 60-70 and residues 323-332. In the TSAC-bound structure, both loops move into the active site, resulting in the positioning of two hydrophobic residues (one from each loop), Ile69 and Val325, near the methyl group of creatine. This apparently provides a specificity pocket for optimal creatine binding as this interaction is missing in the AK structure. In addition, the active site of the transition-state analogue complex is completely occluded from solvent, unlike the ADP-Mg(2+)-bound monomer and the unliganded structures reported previously.

Expression of Torpedo californica creatine kinase in Escherichia coli and purification from inclusion bodies

The pET17 expression vector was used to express creatine kinase from the electric organ of Torpedo californica as inclusion bodies in Escherichia coli BL21(DE3) cells. The insoluble aggregate was dissolved in 8M urea and, following extraction with Triton X-100, the enzyme was refolded by dialysis against Tris buffer (pH 8.0) containing 0.2M NaCl. After two buffer changes, chromatography on Blue Sepharose was used as a final step in the purification procedure. Approximately 54mg active protein was recovered from a 1L culture and the refolded enzyme had a specific activity of 75U/mg. The molecular mass of the purified protein was consistent with that predicted from the amino acid sequence and the CD spectrum of the refolded enzyme was essentially identical to that of creatine kinase from human muscle (HMCK). The K(m) values of ATP and ADP were also similar to those of HMCK, while the K(m) values for both phosphocreatine and creatine were approximately 5-10-fold higher. The purification described here is in marked contrast with earlier attempts at purification of this isozyme where, in a process yielding less than 1mg/L culture, enzyme with a specific activity of ca. 5U/mg was obtained.

[Spectral characterization of amorphous fluorinated carbon film with a low dielectric constant]

Amorphous fluorinated carbon films have been prepared from the gaseous mixture of CH4 and C4F8 by plasma enhanced chemical vapor deposition (PECVD) method. The dielectric constant of the deposited film under the experimental conditions is 2.3. Fourier transform infrared spectrum (FTIR) indicates that the film contains minor unsaturated double bonds such as C=O, C=C, etc in addition to CFn (n = 1-3) configurations. However, no sign reveals the existence of C-H and O-H in the film. Further, X-ray photoelectron spectrum (XPS) verifies that carbon in the deposited film has six chemical states, which are CF3 (8%), CF2(19%), CF (26.7%), C-CFn (42.5%), C-C(3.3%) and C=O (0.5%). It indicates that about 54% of carbon atoms in the film bond with fluorine atoms, and around 43% bond with carbon atoms of CFn configurations instead of bonding directly with fluorine atoms. The adjacent carbon atoms without bonding with fluorine are very less.

An unusually low pK(a) for Cys282 in the active site of human muscle creatine kinase

All phosphagen kinases contain a conserved cysteine residue which has been shown by crystallographic studies, on both creatine kinase and arginine kinase, to be located in the active site. There are conflicting reports as to whether this cysteine is essential for catalysis. In this study we have used site-directed mutagenesis to replace Cys282 of human muscle creatine kinase with serine and methionine. In addition, we have replaced Cys282, conserved across all creatine kinases, with alanine. No activity was found with the C282M mutant. The C282S mutant showed significant, albeit greatly reduced, activity in both the forward (creatine phosphorylation) and reverse (MgADP phosphorylation) reactions. The K(m) for creatine was increased approximately 10-fold, but the K(m) for phosphocreatine was relatively unaffected. The V and V/K pH-profiles for the wild-type enzyme were similar to those reported for rabbit muscle creatine kinase, the most widely studied creatine kinase isozyme. However, the V/K(creatine) profile for the C282S mutant was missing a pK of 5.4. This suggests that Cys282 exists as the thiolate anion, and is necessary for the optimal binding of creatine. The low pK of Cys282 was also determined spectrophotometrically and found to be 5.6 +/- 0.1. The S284A mutant was found to have reduced catalytic activity, as well as a 15-fold increase in K(m) for creatine. The pK(a) of Cys282 in this mutant was found to be 6.7 +/- 0.1, indicating that H-bonding to Ser284 is an important, but not the sole, factor contributing to the unusually low pK(a) of Cys282.

Characteristics of mutations in the p53 gene in oral squamous cell carcinoma associated with betel quid chewing and cigarette smoking in Taiwanese

p53 mutations are etiologically associated with the development of oral squamous cell carcinomas (OSCCs) or are associated with exposure to specific carcinogens. In this study, we used PCR-single strand conformation polymorphism and DNA sequencing to analyze the conserved regions of the p53 gene (exons 5-9) in OSCC tumor specimens from 187 patients with varied histories of betel quid, tobacco and alcohol use. Ninety-one of the 187 OSCCs (48.66%) showed p53 gene mutations at exons 5-9. The incidence of p53 mutations was not associated with age, sex, TNM stage, status of cigarette smoking or betel quid chewing. However, alcohol drinkers exhibited a significantly higher incidence (57/101, 56.44%) of p53 mutations than non-users (39.53%, 34/86) (P = 0.02). The effect of alcohol on the incidence of p53 mutations was still statistically significant (RR = 2.24; 95% CI, 1.21-4.15) after adjustment for cigarette smoking and betel quid (BQ) chewing. G:C to A:T transitions were the predominant mutations observed and associated with BQ and tobacco use. Alcohol drinking could enhance these transitions. After adjustment for cigarette smoking and BQ chewing, alcohol drinking still showed an independent effect on G:C to A:T transitions (RR = 2.41; 95% CI, 1.01-5.74). These findings strongly suggest an important contributive role of tobacco carcinogens to p53 mutation in this series of Taiwanese OSCCs and alcohol might enhance these mutagenic effects. As safrole-DNA adducts have been detected in 77% (23/30) of the OSCC tissues from Taiwanese oral cancer patients with a BQ chewing history, we cannot rule out the possibility that safrole or other carcinogens present in the BQ may cause a similar pattern of mutagenesis. Determination of the role of safrole and other carcinogens present in BQ on the pattern of p53 gene mutation in OSCC will require further study.

Mutations of p53 gene in human colorectal cancer: distinct frameshifts among populations

We analyzed 57 p53 gene mutations in 181 colorectal cancer patients in Taiwan and compiled data on 475 independent p53 mutations in 1,156 primary colorectal cancer patients worldwide between 1992 to 1998. Transitions at the CpG sites were observed in 31 (54%) and 232 cases (49%), respectively. Frameshift mutations occurring within exons were observed in 11 (20%) and 50 cases (10%), respectively. Among the various populations studied, colorectal cancer in Taiwan had the lowest p53 mutation rate (31%), highest frequency (20%) of frameshift mutations and the second lowest rate (13%) of transversion mutation. Based on their relation to the base runs, the 61 frameshift mutations could be grouped into 4 subclasses. After corrections were made for differences in the base number in a run, the relative mutational frequency at a base run was found to be 9- to 47-fold over that in the no-run residues. The p53 frameshift mutational spectrum found in the cases in Taiwan, with respect to hotspot sequence, was significantly different from those in the selected database (p = 0.008). These data support that the patterns of high frequency of transitions at CpG sites and low frequency of transversions in base substitutions in the p53 gene are similar regardless of patient origin. However, these data also illustrate that frameshift mutations in the p53 gene in colorectal cancer patients are sequence dependent and are distinct among populations.