HSPB1 as a novel regulator of ferroptotic cancer cell death

Ferroptosis is an iron-dependent form of non-apoptotic cell death, but its molecular mechanism remains largely unknown. Here, we demonstrate that heat shock protein beta-1 (HSPB1) is a negative regulator of ferroptotic cancer cell death. Erastin, a specific ferroptosis-inducing compound, stimulates heat shock factor 1 (HSF1)-dependent HSPB1 expression in cancer cells. Knockdown of HSF1 and HSPB1 enhances erastin-induced ferroptosis, whereas heat shock pretreatment and overexpression of HSPB1 inhibits erastin-induced ferroptosis. Protein kinase C-mediated HSPB1 phosphorylation confers protection against ferroptosis by reducing iron-mediated production of lipid reactive oxygen species. Moreover, inhibition of the HSF1-HSPB1 pathway and HSPB1 phosphorylation increases the anticancer activity of erastin in human xenograft mouse tumor models. Our findings reveal an essential role for HSPB1 in iron metabolism with important effects on ferroptosis-mediated cancer therapy.

Mechanism of action of eukaryotic DNA topoisomerase I and drugs targeted to the enzyme

DNA topoisomerase I is essential for cellular metabolism and survival. It is also the target of a novel class of anticancer drugs active against previously refractory solid tumors, the camptothecins. The present review describes the topoisomerase I catalytic mechanisms with particular emphasis on the cleavage complex that represents the enzyme's catalytic intermediate and the site of action for camptothecins. Roles of topoisomerase I in DNA replication, transcription and recombination are also reviewed. Because of the importance of topoisomerase I as a chemotherapeutic target, we review the mechanisms of action of camptothecins and the other topoisomerase I inhibitors identified to date.

Current insights into the regulation of programmed cell death by NF-kappaB

The nuclear factor-kappaB (NF-kappaB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-kappaB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-kappaB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-kappaB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-kappaB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-kappaB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-kappaB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-kappaB in many disease conditions including tumor development, tumor progression and anticancer treatment.

Sequential Monte Carlo without likelihoods

Recent new methods in Bayesian simulation have provided ways of evaluating posterior distributions in the presence of analytically or computationally intractable likelihood functions. Despite representing a substantial methodological advance, existing methods based on rejection sampling or Markov chain Monte Carlo can be highly inefficient and accordingly require far more iterations than may be practical to implement. Here we propose a sequential Monte Carlo sampler that convincingly overcomes these inefficiencies. We demonstrate its implementation through an epidemiological study of the transmission rate of tuberculosis.

Molecular cloning, tissue distribution and chromosomal localization of a novel member of the opioid receptor gene family

A cDNA was isolated from rat brain by low stringency hybridization with the rat mu opioid receptor cDNA. Sequence analysis of this clone indicated that it contains an open reading frame capable of encoding a 367 amino acid protein. The deduced amino acid sequence of this protein shows high degrees of homology to all three opioid receptors, mu, kappa, and delta, suggesting that it is a member of the opioid receptor gene family. RNA blot analysis detected high level expression of the receptor mRNA in the brain. Southern blot analysis suggests that it is a single-copy gene, and mapping studies localized the gene on mouse chromosome 2. Despite the high sequence homologies between this protein and the other opioid receptors, expression studies of this clone in COS-7 cells did not show binding to [3H]diprenorphine, a ligand that binds to the other three opioid receptors. Furthermore, co-expression of this receptor with a G protein-activated potassium channel in Xenopus oocytes did not show functional coupling upon stimulation with mu, kappa and delta agonists. Given the similar degrees of high homology to the mu, kappa and delta opioid receptors and the lack of apparent affinity for their ligands, this receptor does not appear to belong to any of the three known classes of opioid receptors. Rather, it represents a novel member of the opioid receptor gene family, not identified from previous pharmacological studies.

Results from a multicenter, open-label, pivotal phase II study of chidamide in relapsed or refractory peripheral T-cell lymphoma

BACKGROUND

Chidamide is a novel benzamide type of subtype-selective histone deacetylase (HDAC) inhibitor with unique mechanisms of action compared with marketed HDAC inhibitors. This phase II study was to evaluate the efficacy and safety of chidamide in relapsed or refractory peripheral T-cell lymphoma (PTCL) in Chinese population.

PATIENTS AND METHODS

Patients with relapsed or refractory PTCL of different subtypes received chidamide of 30 mg orally twice per week. The primary end point was overall response rate (ORR). Responding patients should be confirmed at least 4 weeks after the criteria of the response were first met, and were reviewed by an independent review committee.

RESULTS

Eighty-three patients were enrolled and 79 patients with eligible PTCL histology were for efficacy assessments. Patients enrolled over 10% were with subtypes of PTCL not otherwise specified (34%), anaplastic large-cell lymphoma (22%), extranodal natural killer (NK)/T-cell lymphoma, nasal type (20%), or angioimmunoblastic T-cell lymphoma (AITL, 13%). The ORR was 28% (22 of 79) including 14% (11 of 79) with complete response/unconfirmed complete response (CR/CRu). Median progression-free survival and overall survival were 2.1 and 21.4 months, respectively. AITL patients tended to have higher ORR (50%) and CR/CRu rate (40%), as well as more durable responses, to chidamide treatment. Most adverse events (AEs) were grade 1 or 2, and AEs ≥grade 3 that occurred in ≥10% patients were thrombocytopenia (22%), leucopenia (13%) and neutropenia (11%), respectively.

CONCLUSION

Chidamide represents a novel oral benzamide class of HDAC inhibitor with significant single-agent activity and manageable toxicity in relapsed or refractory PTCL, and provides a much needed treatment option in this indication in China. Results led to China Food and Drug Administration approval of chidamide in this indication.

UV activates growth factor receptors via reactive oxygen intermediates

Exposure of mammalian cells to UV irradiation induces rapid and transient expression of early growth response-1 gene (Egr-1) encoding a transcription factor that plays a role in cell survival. These signals from the irradiated cell surface are likely to involve more than one pathway, and we show here that an essential pathway involves activation of several growth factor receptors by reactive oxygen intermediates (ROI). UVC irradiation causes the tyrosine phosphorylation of EGF receptor (EGFR) in mouse NIH 3T3 fibroblasts and HC11 mouse mammary cells. EGFR activation by irradiation of cells is abrogated by suramin, by antioxidants, and by the presence of a dominant negative EGFR. UV induces the formation of complexes between activated EGFR and SOS, Grb2, PLC gamma, and SHC that can be precipitated with antibodies to EGFR. The activation of EGFR by UV is mimicked by H2O2, suggesting that ROI may function upstream of EGFR activation. Our observations support the hypothesis that ROI and growth factor receptors operate in the early steps of the UV signal that lead to the enhanced expression and activity of Egr-1.

Classifying spatial patterns of brain activity with machine learning methods: application to lie detection

Patterns of brain activity during deception have recently been characterized with fMRI on the multi-subject average group level. The clinical value of fMRI in lie detection will be determined by the ability to detect deception in individual subjects, rather than group averages. High-dimensional non-linear pattern classification methods applied to functional magnetic resonance (fMRI) images were used to discriminate between the spatial patterns of brain activity associated with lie and truth. In 22 participants performing a forced-choice deception task, 99% of the true and false responses were discriminated correctly. Predictive accuracy, assessed by cross-validation in participants not included in training, was 88%. The results demonstrate the potential of non-linear machine learning techniques in lie detection and other possible clinical applications of fMRI in individual subjects, and indicate that accurate clinical tests could be based on measurements of brain function with fMRI.

Comparison of human genetic and sequence-based physical maps

Recombination is the exchange of information between two homologous chromosomes during meiosis. The rate of recombination per nucleotide, which profoundly affects the evolution of chromosomal segments, is calculated by comparing genetic and physical maps. Human physical maps have been constructed using cytogenetics, overlapping DNA clones and radiation hybrids; but the ultimate and by far the most accurate physical map is the actual nucleotide sequence. The completion of the draft human genomic sequence provides us with the best opportunity yet to compare the genetic and physical maps. Here we describe our estimates of female, male and sex-average recombination rates for about 60% of the genome. Recombination rates varied greatly along each chromosome, from 0 to at least 9 centiMorgans per megabase (cM Mb(-1)). Among several sequence and marker parameters tested, only relative marker position along the metacentric chromosomes in males correlated strongly with recombination rate. We identified several chromosomal regions up to 6 Mb in length with particularly low (deserts) or high (jungles) recombination rates. Linkage disequilibrium was much more common and extended for greater distances in the deserts than in the jungles.

Rapid death of injected myoblasts in myoblast transfer therapy

Myoblast transplantation has been proposed as a potential therapy for Duchenne muscular dystrophy (DMD). A Y-chromosome-specific probe was used to track the fate of donor male myoblasts injected into dystrophic muscles of female mdx mice (which are an animal model for DMD). In situ analysis with the Y-probe showed extremely poor survival of isolated normal male (C57B1/10Sn) donor myoblasts after injection into injured or uninjured muscles of dystrophic (mdx) and normal (C57B1/10Sn) female host mice. A decrease in the numbers of donor (male) myoblasts was seen from 2 days and was marked by 7 days after injection: few or no donor myoblasts were detected in host muscles examined at 3-12 months. There was limited movement of the injected donor myoblasts and fusion into host myofibers was rare. The results of this study strongly suggest that the failure of clinical trials of myoblast transplantation in boys with DMD may have been due to rapid and massive death of the donor myoblasts soon after myoblast injection.

Global patterns of groundwater table depth

Shallow groundwater affects terrestrial ecosystems by sustaining river base-flow and root-zone soil water in the absence of rain, but little is known about the global patterns of water table depth and where it provides vital support for land ecosystems. We present global observations of water table depth compiled from government archives and literature, and fill in data gaps and infer patterns and processes using a groundwater model forced by modern climate, terrain, and sea level. Patterns in water table depth explain patterns in wetlands at the global scale and vegetation gradients at regional and local scales. Overall, shallow groundwater influences 22 to 32% of global land area, including ~15% as groundwater-fed surface water features and 7 to 17% with the water table or its capillary fringe within plant rooting depths.

Decreased Egr-1 expression in human, mouse and rat mammary cells and tissues correlates with tumor formation

We have examined several types of tumor cell lines and shown that they invariably expressed little or no Egr-1, in contrast to their normal counterparts. We have previously shown that the expression of exogenous Egr-1 in human breast and other tumor cells markedly reduces transformed growth and tumorigenicity. We therefore hypothesized that the loss of Egr-1 expression plays a role in transformation. All human and mouse breast cancer cell lines and tumors examined had reduced Egr-1 expression compared with their normal counterparts. Reduced Egr-1 expression was also observed in 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumors, and this level increased to normal levels in tumors that regressed after tamoxifen treatment. We concluded, therefore, that loss of Egr-1 expression may play a role in the deregulation of normal growth in the tumorigenic process and that Egr-1 acts as a tumor suppressor gene.

Simultaneous detection of multiple cytokines from conditioned media and patient's sera by an antibody-based protein array system

We have developed a novel technique for high-throughput simultaneous screening of multiple cytokine expression based on a protein array system. Our method has the advantage of showing the specificity of enzyme-linked immunosorbent assays, sensitivity of enhanced chemiluminescence (ECL), and high-throughput of microspot. In this system, the cytokine array membranes were created by spotting capture antibodies onto the membranes. The membranes were then incubated with biological samples such as conditioned media and patient's sera. The bound proteins were then recognized by biotin-conjugated antibodies and detected by horseradish peroxidase-conjugated streptavidin coupled with ECL. Experiments demonstrated that 24 cytokines from conditioned media and patient's sera could be simultaneously detected using this new approach. This methodology should allow us to develop many high-density protein array systems to detect a variety of proteins. To validate and quantitate the expression of key molecules in a wide range of samples, we have developed conditioned medium arrays to evaluate hundreds and even thousands of samples from individual cells and patients in a single microarray. The combinations of protein arrays and conditioned medium arrays or serum arrays will provide a powerful tool to identify the protein expression profiles and rapidly validate their expression in many types and numbers of samples.

Human glutathione S-transferase P1-1 interacts with TRAF2 and regulates TRAF2-ASK1 signals

Human glutathione S-transferase P1-1 (GSTP1-1) is an ubiquitously expressed protein that plays an important role in the detoxification and xenobiotics metabolism. It has been shown that GSTP1-1 interacts with c-Jun NH(2)-terminal kinase (JNK) and suppresses its activity. Here, we report a novel function of GSTP1-1 in regulating tumor necrosis factor-alpha (TNF-alpha)-triggered signaling. The present experiments showed that GSTP1-1 physically associated with tumor necrosis factor receptor-associated factor 2 (TRAF2) in vivo and in vitro. Overexpression of GSTP1-1 inhibited TRAF2-induced activation of both JNK and p38 but not of nuclear factor-kappaB (NF-kappaB). Glutathione S-transferase P1-1 also attenuated TRAF2-enhanced apoptosis signal-regulating kinase 1 (ASK1) autophosphorylation and inhibited TRAF2-ASK1-induced cell apoptosis by suppressing the interaction of TRAF2 and ASK1. Conversely, silencing of GSTP1-1 expression through RNA interference (RNAi) resulted in increase of TNF-alpha-dependent TRAF2-ASK1 association followed by hyper-activation of ASK1 and JNK. A mutant GSTP1-1 lacking TRAF domain-binding motif exhibited a significant decline of capacity to bind TRAF2 and block TRAF2-ASK1 signaling compared with the wild type of GSTP1-1. Moreover, the glutathione-conjugating activity of GSTP1-1 was not involved in the regulation of TRAF2 signaling. These findings indicate that GSTP1-1 plays an important regulatory role in TNF-alpha-induced signaling by forming ligand-binding interactions with TRAF2, which provides a new insight for analysing the protective effects of GSTP1-1 in tumor cells.

Diabetes mellitus and risk of hip fractures: a meta-analysis

This meta-analysis revealed that diabetic adults had a twofold greater risk of hip fractures compared with non-diabetic populations, and this association was more pronounced in type 1 diabetes.

INTRODUCTION

The relationship between diabetes mellitus and risk of hip fracture yielded conflicting results. We conducted a meta-analysis to investigate the association between diabetes mellitus and the risk of hip fractures based on observational studies.

METHODS

We conducted a systematic literature search of PubMed and Embase databases through May 2015. We selected cohort and case-control studies providing at least age-adjusted risk ratio (RR) and corresponding 95 % confidence intervals (CI) of hip fractures among diabetic and non-diabetic subjects. Moreover, we pooled the female-to-male RR of hip fractures from studies that reported gender-specific risk estimate in a single study.

RESULTS

Twenty-one studies involving 82,293 hip fracture events among 6,995,272 participants were identified. Diabetes mellitus was associated with an increased risk of hip fractures (RR 2.07; 95 % CI 1.83-2.33) in a random effects model. Subgroup analysis indicated that excess risk of hip fracture was more pronounced in type 1 diabetes (RR 5.76; 95 % CI 3.66-9.07) than that in type 2 diabetes (RR 1.34; 95 % CI 1.19-1.51). The pooled female-to-male RR of hip fractures was 1.09 (95 % CI 0.93-1.28).

CONCLUSIONS

Individuals with diabetes mellitus have an excessive risk of hip fractures, and this relationship is more pronounced in type 1 diabetes. The association between diabetes and hip fracture risk is similar in men and women.

Quantitative structure-antitumor activity relationships of camptothecin analogues: cluster analysis and genetic algorithm-based studies

Topoisomerase 1 (top1) inhibitors are proving useful against a range of refractory tumors, and there is considerable interest in the development of additional top1 agents. Despite crystallographic studies, the binding site and ligand properties that lead to activity are poorly understood. Here we report a unique approach to quantitative structure-activity relationship (QSAR) analysis based on the National Cancer Institute's (NCI) drug databases. In 1990, the NCI established a drug discovery program in which compounds are tested for their ability to inhibit the growth of 60 different human cancer cell lines in culture. More than 70 000 compounds have been screened, and patterns of activity against the 60 cell lines have been found to encode rich information on mechanisms of drug action and drug resistance. Here, we use hierarchical clustering to define antitumor activity patterns in a data set of 167 tested camptothecins (CPTs) in the NCI drug database. The average pairwise Pearson correlation coefficient between activity patterns for the CPT set was 0.70. Coherence between chemical structures and their activity patterns was observed. QSAR studies were carried out using the mean 50% growth inhibitory concentrations (GI(50)) for 60 cell lines as the dependent variables. Different statistical methods, including stepwise linear regression, principal component regression (PCR), partial least-squares regression (PLS), and fully cross-validated genetic function approximation (GFA) were applied to construct quantitative structure-antitumor relationship models. For our data set, the GFA method performed better in terms of correlation coefficients and cross-validation analysis. A number of molecular descriptors were identified as being correlated with antitumor activity. Included were partial atomic charges and three interatomic distances that define the relative spatial dispositions of three significant atoms (the hydroxyl hydrogen of the E-ring, the lactone carbonyl oxygen of the E-ring, and the carbonyl oxygen of the D-ring). The cross-validated r(2) for the final GFA model was 0.783, indicating a predictive QSAR model.

Individual somatic H1 subtypes are dispensable for mouse development even in mice lacking the H1(0) replacement subtype

H1 linker histones are involved in facilitating the folding of chromatin into a 30-nm fiber. Mice contain eight H1 subtypes that differ in amino acid sequence and expression during development. Previous work showed that mice lacking H1(0), the most divergent subtype, develop normally. Examination of chromatin in H1(0-/-) mice showed that other H1s, especially H1c, H1d, and H1e, compensate for the loss of H1(0) to maintain a normal H1-to-nucleosome stoichiometry, even in tissues that normally contain abundant amounts of H1(0) (A. M. Sirotkin et al., Proc. Natl. Acad. Sci. USA 92:6434-6438, 1995). To further investigate the in vivo role of individual mammalian H1s in development, we generated mice lacking H1c, H1d, or H1e by homologous recombination in mouse embryonic stem cells. Mice lacking any one of these H1 subtypes grew and reproduced normally and did not exhibit any obvious phenotype. To determine whether one of these H1s, in particular, was responsible for the compensation present in H1(0-/-) mice, each of the three H1 knockout mouse lines was bred with H1(0) knockout mice to generate H1c/H1(0), H1d/H1(0), or H1e/H1(0) double-knockout mice. Each of these doubly H1-deficient mice also was fertile and exhibited no anatomic or histological abnormalities. Chromatin from the three double-knockout strains showed no significant change in the ratio of total H1 to nucleosomes. These results suggest that any individual H1 subtype is dispensable for mouse development and that loss of even two subtypes is tolerated if a normal H1-to-nucleosome stoichiometry is maintained. Multiple compound H1 knockouts will probably be needed to disrupt the compensation within this multigene family.

Altered hematopoiesis, behavior, and sexual function in mu opioid receptor-deficient mice

The mu opioid receptor is thought to be the cellular target of opioid narcotics such as morphine and heroin, mediating their effects in both pain relief and euphoria. Its involvement is also implicated in a range of diverse biological processes. Using a mouse model in which the receptor gene was disrupted by targeted homologous recombination, we explored the involvement of this receptor in a number of physiological functions. Mice homozygous for the disrupted gene developed normally, but their motor function was altered. Drug-naive homozygotes displayed reduced locomotor activity, and morphine did not induce changes in locomotor activity observed in wild-type mice. Unexpectedly, lack of a functional receptor resulted in changes in both the host defense system and the reproductive system. We observed increased proliferation of granulocyte-macrophage, erythroid, and multipotential progenitor cells in both bone marrow and spleen, indicating a link between hematopoiesis and the opioid system, both of which are stress-responsive systems. Unexpected changes in sexual function in male homozygotes were also observed, as shown by reduced mating activity, a decrease in sperm count and motility, and smaller litter size. Taken together, these results suggest a novel role of the mu opioid receptor in hematopoiesis and reproductive physiology, in addition to its known involvement in pain relief.

Downregulation of FAP suppresses cell proliferation and metastasis through PTEN/PI3K/AKT and Ras-ERK signaling in oral squamous cell carcinoma

It is largely recognized that fibroblast activation protein (FAP) is expressed in cancer-associated fibroblasts (CAFs) of many human carcinomas. Furthermore, FAP was recently also reported to be expressed in carcinoma cells of the breast, stomach, pancreatic ductal adenocarcinoma, colorectum, and uterine cervix. The carcinoma cell expression pattern of FAP has been described in several types of cancers, but the role of FAP in oral squamous cell carcinoma (OSCC) is unknown. The role of endogenous FAP in epithelium-derived tumors and molecular mechanisms has also not been reported. In this study, FAP was found to be expressed in carcinoma cells of OSCC and was upregulated in OSCC tissue samples compared with benign tissue samples using immunohistochemistry. In addition, its expression level was closely correlated with overall survival of patients with OSCC. Silencing FAP inhibited the growth and metastasis of OSCC cells in vitro and in vivo. Mechanistically, knockdown of FAP inactivated PTEN/PI3K/AKT and Ras-ERK and its downstream signaling regulating proliferation, migration, and invasion in OSCC cells, as the inhibitory effects of FAP on the proliferation and metastasis could be rescued by PTEN silencing. Our study suggests that FAP acts as an oncogene and may be a potential therapeutic target for patients with OSCC.

Beta-synuclein gene alterations in dementia with Lewy bodies

OBJECTIVE

To determine whether mutations in the genes for alpha-synuclein or beta-synuclein are responsible for dementia with Lewy bodies (DLB), a disorder closely related to Parkinson disease (PD).

METHODS

The authors ascertained 33 sporadic cases of DLB and 10 kindreds segregating DLB. DNA samples from the 43 index cases were screened for alterations in the genes for alpha-synuclein and beta-synuclein, as alpha-synuclein alterations cause PD and beta-synuclein may modulate alpha-synuclein aggregation and neurotoxicity.

RESULTS

Two amino acid alterations were identified in unrelated DLB index cases: a valine to methionine substitution at codon 70 (V70M) and a proline to histidine substitution at codon 123 (P123H), both in the beta-synuclein gene. These amino acid substitutions occur at conserved residues in highly conserved regions of the beta-synuclein protein. Screening of at least 660 chromosomes from control subjects matched to the patients' population groups failed to identify another V70M or P123H allele. Cosegregation analysis of an extended pedigree segregating the P123H beta-synuclein alteration suggested that it is a dominant trait with reduced penetrance or a risk factor polymorphism. Histopathology and immunohistochemistry analysis of index case brain sections revealed widespread Lewy body pathology and alpha-synuclein aggregation without evidence of beta-synuclein aggregation.

CONCLUSION

Mutations in the beta-synuclein gene may predispose to DLB.

Antibacterial dental composites with chlorhexidine and mesoporous silica

One of the leading causes for the failure of dental composite restorations is secondary caries. Effectively inhibiting cariogenic biofilms and reducing secondary caries could extend the service life of composite restorations. Dental composites releasing antibacterial agents such as chlorhexidine (CHX) have shown biofilm-inhibitory efficacy, but they usually have poor physical and mechanical properties. Herein, we present a study of a new method to encapsulate and release CHX from dental composite using mesoporous silica nanoparticles (MSNs). SBA-15 MSNs were synthesized according to a reported procedure. CHX (62.9 wt%) was encapsulated into dried MSN from 0.3 M CHX ethanol solution. The dental composites containing 0% (control), 3%, 5%, and 6.3% CHX or the same amounts of CHX entrapped in MSN (denoted as CHX@MSN) were fabricated with methacrylate monomers and silanized glass fillers (CHX or CHX@MSN + glass filler particle = 70 wt%). The monomer mixture consisted of bisphenol A glycidyl methacrylate (BisGMA), hexanediol dimethacrylate (HDDMA), ethoxylated bisphenol A dimethacrylate (EBPADMA), and urethane dimethacrylates (UEDMA) at a weight ratio of 40:30:20:10. The composites were tested for CHX release and recharge, flexural strength and modulus (at 24 hr and 1 mo), surface roughness, in vitro wear, and antibacterial activity against Streptococcus mutans and Lactobacillus casei (in both planktonic growth and biofilm formation). The results showed that the composites with CHX@MSN largely retained mechanical properties and smooth surfaces and showed controlled release of CHX over a long time. In contrast, the composites with directly mixed CHX showed reduced mechanical properties, rough surfaces, and burst release of CHX in a short time. The composites with CHX either directly mixed or in MSN showed strong inhibition to S. mutans and L. casei. This research has demonstrated the successful application of MSNs as a novel nanotechnology in dental materials to inhibit oral biofilm without sacrificing materials' mechanical properties and surface integrity.

Molecular modeling studies of the DNA-topoisomerase I ternary cleavable complex with camptothecin

The present studies provide a three-dimensional model for the postulated ternary cleavable complex of topoisomerase I (top1), DNA, and camptothecin (CPT). Molecular simulations were done using the AMBER force field. The results suggest that a ternary cleavable complex might be stabilized by several hydrogen bonds in the binding site. In this proposed "drug-stacking" model, CPT is pseudointercalated in the top1-linked DNA cleavage site and interacts with the protein near its catalytic tyrosine through hydrogen bonding and stacking. The structural model is consistent with the following experimental observations: (i) the N3 position of the 5' terminal purine of the cleaved DNA strand is readily alkylated by 7-chloromethyl 10,11-methylenedioxy CPT; (ii) CPT generally tolerates substituents at positions 7, 9, and 10 but is inactivated by additions at position 12; (iii) 10,11-methylenedioxy (MDO) CPT is much more potent than 10,11-dimethoxy (DMO) CPT; (iv) the lactone portion of CPT is essential for top1 inhibitory activity; (v) 20S derivatives of CPT are much more potent than the 20R analogues; (vi) a catalytic tyrosine hydroxyl in top1 covalently links to the 3' terminal base, T, of the cleaved DNA strand; and (vii) top1 mutation Asn722Ser leads to CPT resistance. A total of 18 camptothecin derivatives with different DNA cleavage potencies were docked into the hypothetical cleavable complex binding site to test and refine the model. These studies provide insight into a possible mechanism of top1 inhibition by CPT derivatives and suggest rational approaches for the design of new CPT derivatives.

Phenotype and genotype of advanced premalignant head and neck lesions after chemopreventive therapy

BACKGROUND

The goal of chemoprevention is to reduce the risk of cancer development by reversing or blocking the tumorigenic process through the use of pharmacologic or natural agents. To determine the potential role of genetic alterations in assessing cancer risk and in evaluating the efficacy of chemopreventive agents, we studied 22 patients with advanced premalignant lesions of the head and neck who were part of a prospective cancer prevention trial that is investigating a regimen of 13-cis-retinoic acid, interferon alfa, and alpha-tocopherol administered for 12 months or until disease progression.

METHODS

We used polymerase chain reaction analysis of microsatellite DNA sequences in cells from precancerous lesions to determine the frequencies of genetic alterations--namely, loss of heterozygosity (LOH) and microsatellite instability--at chromosomal loci that are commonly deleted in head and neck cancer.

RESULTS

Prior to treatment, 17 (81%) of 21, eight (44%) of 18, and eight (42%) of 19 patients who were informative (i.e., heterozygous) at chromosomes 9p21, 3p14, and 17p13, respectively, exhibited LOH in at least one of their lesion biopsy specimens. Among nine patients who exhibited LOH at chromosome 9p21 in pretreatment biopsy specimens and who had completed at least 5 months of therapy, the genetic loss persisted in eight--including three of the four patients who exhibited complete histologic responses (i.e., no evidence of dysplasia in their biopsy specimens).

IMPLICATION

Our data suggest that clinical and histologic assessments of the response to chemopreventive agents may be insufficient to determine their efficacy and that critical genetic alterations could be used as independent biomarkers to augment the ability to evaluate the efficacy of such agents.