Association between circulating levels of sex steroid hormones and Barrett's esophagus in men: a case-control analysis

BACKGROUND & AIMS

Esophageal adenocarcinoma is believed to result from the progression of gastroesophageal reflux disease to erosive esophagitis and re-epithelialization of the esophagus with a columnar cell population termed Barrett's esophagus (BE). Men develop BE and esophageal adenocarcinoma more frequently than women, yet little is known about the mechanisms of this difference. We assessed whether sex steroid hormones were associated with BE in a male population.

METHODS

We analyzed data from the Barrett's Esophagus Early Detection Case Control Study, based at the Walter Reed National Military Medical Center. Blood samples were collected from 174 men with BE and 213 men without BE (controls, based on endoscopic analysis); 13 sex steroid hormones were measured by mass spectrometry and sex hormone binding globulin was measured by enzyme-linked immunosorbent assay. We also calculated free estradiol, free testosterone, and free dihydrotestosterone (DHT). We used multivariable logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for age, race, smoking status, alcohol consumption, body mass index, heartburn, regurgitation, and gastroesophageal symptom score (excluding heartburn and regurgitation).

RESULTS

Levels of free testosterone and free DHT were associated positively with BE risk; patients in the highest quartile for these hormones were most likely to have BE (free testosterone: OR, 5.36; 95% CI, 2.21-13.03; P = .0002; free DHT: OR, 4.25; 95% CI, 1.87-9.66; P = .001). Level of estrone sulfate was associated inversely with BE risk (P for trend = .02). No other hormone was associated with BE risk. Relationships were not modified by age or BMI.

CONCLUSIONS

In an analysis of men, levels of free testosterone and free DHT were significantly associated with BE.

Global changes in gene expression of Barrett's esophagus compared to normal squamous esophagus and gastric cardia tissues

BACKGROUND

Barrett's esophagus (BE) is a metaplastic precursor lesion of esophageal adenocarcinoma (EA), the most rapidly increasing cancer in western societies. While the prevalence of BE is increasing, the vast majority of EA occurs in patients with undiagnosed BE. Thus, we sought to identify genes that are altered in BE compared to the normal mucosa of the esophagus, and which may be potential biomarkers for the development or diagnosis of BE.

DESIGN

We performed gene expression analysis using HG-U133A Affymetrix chips on fresh frozen tissue samples of Barrett's metaplasia and matched normal mucosa from squamous esophagus (NE) and gastric cardia (NC) in 40 BE patients.

RESULTS

Using a cut off of 2-fold and P<1.12E-06 (0.05 with Bonferroni correction), we identified 1324 differentially-expressed genes comparing BE vs NE and 649 differentially-expressed genes comparing BE vs NC. Except for individual genes such as the SOXs and PROM1 that were dysregulated only in BE vs NE, we found a subset of genes (n = 205) whose expression was significantly altered in both BE vs NE and BE vs NC. These genes were overrepresented in different pathways, including TGF-β and Notch.

CONCLUSION

Our findings provide additional data on the global transcriptome in BE tissues compared to matched NE and NC tissues which should promote further understanding of the functions and regulatory mechanisms of genes involved in BE development, as well as insight into novel genes that may be useful as potential biomarkers for the diagnosis of BE in the future.

The non-nucleoside reverse transcriptase inhibitor efavirenz stimulates replication of human immunodeficiency virus type 1 harboring certain non-nucleoside resistance mutations

We measured the effects of non-nucleoside reverse transcriptase (RT) inhibitor-resistant mutations K101E+G190S, on replication fitness and EFV-resistance of HIV(NL4-3). K101E+G190S reduced fitness in the absence of EFV and increased EFV resistance, compared to either single mutant. Unexpectedly, K101E+G190S also replicated more efficiently in the presence of EFV than in its absence. Addition of the nucleoside resistance mutations L74V or M41L+T215Y to K101E+G190S improved fitness and abolished EFV-dependent stimulation of replication. D10, a clinical RT backbone containing M41L+T215Y and K101E+G190S, also demonstrated EFV-dependent stimulation that was dependent on the presence of K101E. These studies demonstrate that non-nucleoside reverse transcriptase inhibitors can stimulate replication of NNRTI-resistant HIV-1 and that nucleoside-resistant mutants can abolish this stimulation. The ability of EFV to stimulate NNRTI-resistant mutants may contribute to the selection of HIV-1 mutants in vivo. These studies have important implications regarding the treatment of HIV-1 with combination nucleoside and non-nucleoside therapies.

The HIV-1 reverse transcriptase mutants G190S and G190A, which confer resistance to non-nucleoside reverse transcriptase inhibitors, demonstrate reductions in RNase H activity and DNA synthesis from tRNA(Lys, 3) that correlate with reductions in replication efficiency

We evaluated the replication efficiency of the HIV reverse transcriptase (RT) mutants K103N, G190A, and G190S, which confer resistance to the non-nucleoside RT inhibitor efavirenz, using growth competition assays in cell culture. In the absence of efavirenz, the fitness hierarchy was G190S < G190A < K103N < wild-type. The fitness reduction of G190S relative to K103N was less evident at high efavirenz concentrations, although K103N still replicated more efficiently. Efficiency of RNase H cleavage and RNA-dependent DNA synthesis from tRNA(Lys, 3) correlated with relative fitness, in biochemical studies of mutant RTs. Presteady state and steady state polymerization assays using DNA primers detected no abnormalities. This work is consistent with previous studies demonstrating that initiation of viral DNA synthesis is reduced in mutants with slowed RNase H cleavage, and suggests that both abnormalities contribute to the replication defect of these mutants. It also suggests that high concentrations of efavirenz are unlikely to favor the selection of G190S clinically.

Single-nucleotide polymorphism alleles in the insulin receptor gene are associated with typical migraine

We have identified a migraine locus on chromosome 19p13.3/2 using linkage and association analysis. We isolated 48 single-nucleotide polymorphisms within the locus, of which we genotyped 24 in a Caucasian population comprising 827 unrelated cases and 765 controls. Five single-nucleotide polymorphisms within the insulin receptor gene showed significant association with migraine. This association was independently replicated in a case-control population collected separately. We used experiments with insulin receptor RNA and protein to investigate functionality for the migraine-associated single-nucleotide polymorphisms. We suggest possible functions for the insulin receptor in migraine pathogenesis.

Impact of clinical reverse transcriptase sequences on the replication capacity of HIV-1 drug-resistant mutants

We have shown that the HIV-1 laboratory strain NL4-3 that contains P236L [a reverse transcriptase mutation conferring resistance to the nonnucleoside reverse transcriptase inhibitor (NRTI) delavirdine] replicates more slowly than wild-type NL4-3. Other NNRTI-resistance mutations, such as K103N and Y181C, do not reduce the replication capacity of NL4-3 as much as P236L and develop more frequently in HIV-1 isolates from patients failing delavirdine. However, a minority of patients on delavirdine therapy still have isolates with P236L. We postulated that reverse transcriptase (RT) sequences from these patient isolates contain other mutations that compensate for the adverse effect of P236L. To test this hypothesis, we created 15 chimeric NL4-3 isolates that contained delavirdine-resistant RT sequences derived from eight patient isolates and characterized their replication kinetics. Nine of 10 patient-derived clones containing P236L replicated as slowly as NL4-3 with P236L. In contrast, three of five clones that did not have P236L (but had either K103N or Y181C) replicated significantly better than NL4-3 with P236L. Thus, the majority of patients who acquire P236L during delavirdine therapy do not have RT mutations that compensate for the replication defect conferred by P236L. We hypothesize that HIV-1 isolates with P236L may have a compensatory mutation outside RT. Alternatively, variants of HIV-1 with reduced replication fitness may be selected during antiretroviral therapy, suggesting that stochastic events rather than viral replication fitness may determine which drug-resistant mutants emerge early during antiretroviral failure. In some isolates, it appears that the background RT sequence can contribute significantly to the replication fitness of drug-resistant HIV-1 variants.

Mutants of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase resistant to nonnucleoside reverse transcriptase inhibitors demonstrate altered rates of RNase H cleavage that correlate with HIV-1 replication fitness in cell culture

Three mutants of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (V106A, V179D, and Y181C), which occur in clinical isolates and confer resistance to nonnucleoside reverse transcriptase inhibitors (NNRTIs), were analyzed for RNA- and DNA-dependent DNA polymerization and RNase H cleavage. All mutants demonstrated processivities of polymerization that were indistinguishable from wild-type enzyme under conditions in which deoxynucleoside triphosphates were not limiting. The V106A reverse transcriptase demonstrated a three- to fourfold slowing of both DNA 3'-end-directed and RNA 5'-end-directed RNase H cleavage relative to both wild-type and V179D enzymes, similar to what was observed for P236L in a previously published study (P. Gerondelis et al., J. Virol. 73:5803-5813, 1999). In contrast, the Y181C reverse transcriptase demonstrated a selective acceleration of the secondary RNase H cleavage step during both modes of RNase H cleavage. The relative replication fitness of these mutants in H9 cells was assessed in parallel infections as well as in growth competition experiments. Of the NNRTI-resistant mutants, V179D was more fit than Y181C, and both of these mutants were more fit than V106A, which demonstrated the greatest reduction in RNase H cleavage. These findings, in combination with results from previous work, suggest that abnormalities in RNase H cleavage are a common characteristic of HIV-1 mutants resistant to NNRTIs and that combined reductions in the rates of DNA 3'-end- and RNA 5'-end-directed cleavages are associated with significant reductions in the replication fitness of HIV-1.

Analysis of env sequence evolution in human immunodeficiency virus-infected patients receiving therapy with nonnucleoside reverse-transcriptase inhibitors

Nonnucleoside reverse-transcriptase inhibitors (NNRTIs) can rapidly select for drug-resistant human immunodeficiency virus type 1 (HIV-1) variants, although their effect on HIV-1 quasi-species diversity is unknown. To determine if changes in env gene diversification occur with NNRTI therapy, we used the heteroduplex tracking assay (HTA) to study HIV-1 env sequence diversity in 2 groups of patients: those who were on no therapy or were on chronic antiretroviral therapy and those who had just initiated NNRTIs. Forty-nine paired samples from 46 patients were analyzed. Fourteen of 32 paired samples from the NNRTI group and 9 of 17 paired samples from the control group had HTA changes (P>.10). There was no correlation between HTA change and sampling time interval, baseline virus load, change in virus load, or development of NNRTI resistance. Thus, we found no significant correlation of NNRTI therapy with changes in env HTA patterns, suggesting that these treatments had little short-term impact on HIV-1 quasi-species diversity.

Stringent structural and sequence requirements of the human herpesvirus 6B lytic-phase origin of DNA replication

The lytic-phase origin of DNA replication from human herpesvirus 6B (HHV-6B oriLyt) contains two binding sites for the origin-binding protein (OBPH6B), both of which are required for DNA replication and which are separated by an AT-rich spacer. We have tested the functional significance of the structural, spatial and sequence characteristics of this spacer element by constructing a series of mutated origin sequences and analysing their replication efficiency. Changes in the sequence composition of length of the spacer resulted in dramatic decreases in replication efficiency. Furthermore, in contrast to what has been observed for herpes simplex virus type 1 (HSV-1) oriS, insertion of a complete helical turn of DNA into the spacer also resulted in abrogation of origin function. These data suggest that the arrangement of OBP sites in HHV-6B oriLyt is stringently constrained in terms of spacing and intervening sequence.

Identification and analysis of a lytic-phase origin of DNA replication in human herpesvirus 7

Human herpesvirus 7 (HHV-7) DNA sequences colinear with the HHV-6 lytic-phase origin of DNA replication (oriLyt) were amplified by PCR. Plasmid constructs containing these sequences were replicated in HHV-7-infected cord blood mononuclear cells but not in HHV-6-infected cells. In contrast, plasmids bearing HHV-6 oriLyt were replicated in both HHV-6- and HHV-7-infected cells. Finally, the minimal HHV-7 DNA element necessary for replicator activity was mapped to a 600-bp region which contains two sites with high homology to the consensus binding site for the HHV-6 origin binding protein. At least one of these binding sites was shown to be essential for replicator function of HHV-7 oriLyt.

Practical computer applications for endoscopy

A computer can facilitate a nurse's administrative tasks, resulting in increased time to spend with patients. Data can easily be organized and retrieved. Forms can be created when there is no ready-made form at hand. Document revision is easy and cost-effective because the form is not typeset until it has been tried and is ready for permanent adoption. The outcome will be a nursing practice that is more efficient, effective, and professionally rewarding.

Human herpesvirus 6B origin: sequence diversity, requirement for two binding sites for origin-binding protein, and enhanced replication from origin multimers

A previously identified human herpesvirus 6B (HHV-6B) origin of DNA replication contains two binding sites for the origin-binding protein (OBPH6B). We have investigated the functional significance of these sites by determining the replication efficiencies of mutated origin sequences, using a transient replication assay. The results indicate that both sites are required for DNA replication. In addition, we have tested the functional consequences of linear sequence amplifications in the origin. The data show that tandemized origin elements are more efficiently replicated than single-copy origins. Finally, we have determined the extent of interstrain origin sequence variation that exists among HHV-6 isolates by cloning, sequencing, and analyzing origins from a number of virus isolates, including examples of both HHV-6A and HHV-6B.