Pyrido- and benzisothiazolones as inhibitors of histone acetyltransferases (HATs)

We present structure–activity studies on pyrido- and benzisothiazolones as histone acetyltransferase (HAT) inhibitors. Distinct subtype-selectivity profiles were obtained in vitro that correlate with cytotoxicity profiles on cancer cells.

A history of shoulder surgery

Shoulder surgery has emerged from being a marginalised sub-speciality to being an area of much research and advancement within the last seventy years. This has been despite the complexity of the joint, and success majorly rests on parallel development of biomedical technology. This article looks at the past and present of shoulder surgery and discusses future directions in the speciality.

WITHDRAWN: MUA with steroid injection vs. arthroscopic capsular release for adhesive capsulitis: A prospective randomised study

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Abstract P6-05-02: Endocrine biomarkers in response to AR-inhibition with bicalutamide for the treatment of AR(+), ER/PR(−) metastatic breast cancer (MBC) (TBCRC011)

Background: Our group and others have identified a subset of ER/PR(−) breast cancers characterized by expression of the androgen receptor (AR) and androgen-dependent growth (Doane 2006). We conducted a proof-of-concept multicenter phase II study to test the efficacy of the AR-antagonist, bicalutamide for the treatment of AR(+) ER/PR(−) MBC (NCT00468715). Results of the primary endpoint, clinical benefit rate (CBR), were presented at ASCO (Gucalp 2012). Data for the impact of bicalutamide on circulating hormone levels in women are limited. Elevations in serum testosterone (T) and estradiol (E) have been observed for men treated with bicalutamide. We hypothesized comparable patterns of change in circulating endocrine markers in response to bicalutamide for women with MBC.

Methods: Patients (pts) with AR(+) (IHC ≥10%), ER/PR(−) (IHC <10%) MBC were eligible for treatment (tx) if ECOG performance status ≤2 and normal organ function regardless of menopausal status. There was no limit to prior tx except prior trastuzumab required if HER2(+). Tx consisted of bicalutamide 150mg orally daily in 28-day cycles (C). Toxicity assessed q4 weeks, response q12wks. Primary endpoint was CBR. Peripheral blood was collected for total and free T, E and sex hormone binding globulin (SHBG) at baseline, start of C2 (C2) and at end of study (EOS). Standard institutional assays were used. A Wilcoxon signed-rank test was done to compare baseline to C2 and EOS values.

Results: 26 patients with AR(+) ER/PR(−) MBC were treated on study. Evaluable number (n) of pts at baseline, C2 and EOS are 26, 26 and 19 respectively. Two pts remain on study. Menopausal status: pre=2, post=24. Baseline median total and free T and estradiol were consistent with expected norms, however a wide range was observed (Table). There were no significant differences observed for median free T, total T, E or SHBG between baseline and C2 or baseline and EOS. Changes in hormone levels could not be stratified by menopausal status or response to bicalutamide given small sample size. Given the wide range of baseline values, we examined the percent change for each endocrine biomarker from baseline to C2 and EOS. As shown in the Table, there was no difference in median percent change observed across time points for each biomarker.

Males absent on the first (MOF): from flies to humans

Histone modifications such as acetylation, methylation and phosphorylation have been implicated in fundamental cellular processes such as epigenetic regulation of gene expression, organization of chromatin structure, chromosome segregation, DNA replication and DNA repair. Males absent on the first (MOF) is responsible for acetylating histone H4 at lysine 16 (H4K16) and is a key component of the MSL complex required for dosage compensation in Drosophila. The human ortholog of MOF (hMOF) has the same substrate specificity and recent purification of the human and Drosophila MOF complexes showed that these complexes were also highly conserved through evolution. Several studies have shown that loss of hMOF in mammalian cells leads to a number of different phenotypes; a G2/M cell cycle arrest, nuclear morphological defects, spontaneous chromosomal aberrations, reduced transcription of certain genes and an impaired DNA repair response upon ionizing irradiation. Moreover, hMOF is involved in ATM activation in response to DNA damage and acetylation of p53 by hMOF influences the cell's decision to undergo apoptosis instead of a cell cycle arrest. These data, highlighting hMOF as an important component of many cellular processes, as well as links between hMOF and cancer will be discussed.

Complex posterior fracture-dislocation of the shoulder. Epidemiology, injury patterns, and results of operative treatment

BACKGROUND

Complex posterior fracture-dislocations of the shoulder are rare and often associated with poor long-term function regardless of the choice of treatment. The purposes of this study were to evaluate the epidemiology and pathological anatomy of posterior fracture-dislocations of the shoulder and to assess the clinical and radiographic outcomes of a specific treatment protocol of open reduction and internal fixation.

METHODS

We studied the demographic details of a consecutive series of twenty-six patients (twenty-eight shoulders in nineteen men and seven women with a mean age of fifty-three years) who sustained acute posterior dislocation of the humeral head with an associated Neer two, three, or four-part fracture. We used age and gender-specific local census data to assess the incidence of injury in our local population. All patients were treated by open relocation of the humeral head, bone-grafting of humeral head defects if they were causing residual shoulder instability, and internal fixation of the fracture. We recorded the prevalence of fracture complications that were clinically and radiographically apparent and assessed the functional outcome using three validated scoring systems (the Short Form-36 general health measure, the Disabilities of the Arm, Shoulder and Hand score, and the Constant score).

RESULTS

The overall incidence of posterior fracture-dislocations was 0.6 per 100,000 population per year. The peak incidence was in middle-aged men, and most injuries were sustained during a seizure or a fall from a height. In all patients, there was a displaced primary fracture of the anatomic neck of the humerus, propagating from the area of an osteochondral fracture of the anterior aspect of the humeral head (a reverse Hill-Sachs lesion). We recognized three subtypes determined by the extent of the secondary fracture lines. At two years after surgery, the median Constant score was 83.5 points and the median Disabilities of the Arm, Shoulder and Hand score was 17.5 points. The eight components of the Short Form-36 score were not significantly different from those of age and sex-matched controls at two years.

CONCLUSIONS

Acute complex posterior fracture-dislocations of the shoulder are rare, but they occur in patients who are younger than the majority of other patients who sustain a proximal humeral fracture. The use of open reduction and internal fixation to treat these fractures is associated with a relatively low risk of postoperative complications, and the functional outcome is generally favorable.

MSL proteins and the regulation of gene expression

Epigenetics describes changes in genome function that occur without a change in the DNA sequence. Dosage compensation is a prime example of the regulation of gene expression by an epigenetic mechanism. Dosage compensation has evolved to balance the expression of sex-linked genes in males and females, which possess different numbers of sex chromosomes. However, the genetic sequence of the chromosomes is the same in both sexes. This mechanism therefore needs (1) to function in a sex-specific manner, (2) to target the sex chromosome from amongst the autosomes and (3) to establish and maintain through development a precise, equalised level of gene expression in one sex compared to the other. The process by which dosage compensation is orchestrated has been well characterised in fruit flies and mammals. Although each has evolved a specific dosage-compensation mechanism, these systems share some underlying themes; the molecular components that mediate dosage compensation in both include non-coding RNA molecules, which act as nucleation points for the compensation process. Both systems utilise chromatin-modifying enzymes to remodel large domains of a chromosome. This review will discuss the mechanism of dosage compensation in Drosophila in light of recent developments that have brought into question the previous model of dosage compensation.

Symptomatic fibroid uterus in a 15-year-old girl

A 15 year-old gravida 1, abortus 1 black girl presented with chief complaints of menorrhagia, severe dysmenorrhea, and progressively worsening abdominal pain, which was caused by a very large uterine leiomyoma. The symptoms began 6 months earlier, shortly after a 10-week spontaneous abortion at age 14. A solitary 25-cm uterine leiomyoma was removed uneventfully with an abdominal laparotomy. In the English literature of the past 50 years, this case represents the sixth, and we believe, the largest, documented uterine fibroid among teenagers, which required corrective surgery.

The histone H4 acetyltransferase MOF uses a C2HC zinc finger for substrate recognition

Site-specific acetylation of histone H4 by MOF is central to establishing the hyperactive male X chromosome in Drosophila. MOF belongs to the MYST family of histone acetyltransferases (HATs) characterized by an unusual C2HC-type zinc finger close to their HAT domains. The function of these rare zinc fingers is unknown. We found that this domain is essential for HAT activity, in addition to the established catalytic domain. MOF uses its zinc finger to contact the globular part of the nucleosome as well as the histone H4 N-terminal tail substrate. Point mutations that leave the zinc-finger structure intact nevertheless abolish its interaction with the nucleosome. Our data document a novel role of the C2HC-type finger in nucleosome binding and HAT activity.

Chromodomains are protein-RNA interaction modules

In Drosophila, compensation for the reduced dosage of genes located on the single male X chromosome involves doubling their expression in relation to their counterparts on female X chromosomes. Dosage compensation is an epigenetic process involving the specific acetylation of histone H4 at lysine 16 by the histone acetyltransferase MOF. Although MOF is expressed in both sexes, it only associates with the X chromosome in males. Its absence causes male-specific lethality. MOF is part of a chromosome-associated complex comprising male-specific lethal (MSL) proteins and at least one non-coding roX RNA. How MOF is integrated into the dosage compensation complex is unknown. Here we show that association of MOF with the male X chromosome depends on its interaction with RNA. MOF specifically binds through its chromodomain to roX2 RNA in vivo. In vitro analyses of the MOF and MSL-3 chromodomains indicate that these chromodomains may function as RNA interaction modules. Their interaction with non-coding RNA may target regulators to specific chromosomal sites.

Activation of transcription through histone H4 acetylation by MOF, an acetyltransferase essential for dosage compensation in Drosophila

Dosage compensation in Drosophila involves a 2-fold increase in transcription from the single male X relative to the two female X chromosomes. Regulation at the level of the chromosome involves alterations in chromatin organization: male X chromosomes appear decondensed and are marked by acetylation of histone H4 at lysine 16. We demonstrate that MOF, a protein required for dosage compensation with significant sequence similarity to the MYST family of acetyltransferases, is a histone acetyltransferase that acetylates chromatin specifically at histone H4 lysine 16. This acetylation relieves chromatin-mediated repression of transcription in vitro and in vivo if MOF is targeted to a promoter by fusion to a DNA-binding domain. Acetylation of chromatin by MOF, therefore, appears to be causally involved in transcriptional activation during dosage compensation.

Use of V79 cells with stably transfected cytochrome P450 cDNAs in studying the metabolism and effects of cytotoxic drugs

PURPOSE

Studying the metabolism of cytotoxic drugs has become increasingly necessary to predict clinically significant drug-drug interactions and to understand the basis of interindividual variations in the pharmacokinetics of anticancer agents. The aim of this study was to determine the feasibility of using V79 Chinese hamster fibroblasts, which are stably transfected with cytochrome P450 (CYP) cDNAs, to study the metabolism of cytotoxic drugs in vitro.

METHODS

The 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine cell survival after incubation with drugs. Gas chromatography/mass spectroscopy was used for the quantitation of metabolites of cyclophosphamide and ifosfamide in culture medium. The coculture technique was used to study the generation of cytotoxic metabolites in culture medium.

RESULTS

After treatment with either cyclophosphamide or ifosfamide (100 microM to 1 mM) cytotoxicity was demonstrated in only cytochrome CYP2B1- and cytochrome CYP3A4-expressing cells. Treatment of parental nontransfected cells that were cocultured with CYP-expressing cells with cyclophosphamide resulted in increased sensitivity to this drug. All active and inactive metabolites of cyclophosphamide and ifosfamide were detected in the culture medium. Cyclophosphamide-induced cytotoxicity in CYP2B1- and CYP3A4-expressing cells was abrogated by metyrapone and midazolam/ troleandomycin, respectively. Paclitaxel showed greater cytotoxicity against parental V79 cells than against the CYP2BI-, 2E1-, or 3A4-expressing cells, which was also influenced by cotreatment with CYP inhibitors.

CONCLUSIONS

Stable expression of CYP cDNAs by V79 cells provided an in vitro system to study cytotoxic drug metabolism. Cell viability and metabolite assays were used to determine the differential metabolism and effects in different CYP-transfected cell lines treated with cytotoxic drugs. The potential use of this V79 cell expression system is in studying enzymes involved in the metabolism of cytotoxic drugs, especially early in drug development. In addition, this system may be used to determine drug interactions that may influence the outcome of therapy in patients with cancer.

Serum lipids : new biological markers in depression ?

Several studies suggest that a low cholesterol concentration is associated with depression. The authors sought to determine whether an association exists between serum lipid concentrations and depression. 28 drug-naive patients of major depression diagnosed according to DSMlll- R criteria were included in the study and severity of depression was measured on Hamilton Rating Scale for Depression. Suicidal intent was assessed on Suicidal Intent Questionnaire. 28 normal healthy controls were selected and matched for age, sex and body-mass index with the depressives. Serum lipid estimations were done in each subject after 12 hours overnight fasting. The main finding of the study is that total serum cholesterol, serum triglycerides and serum LDL cholesterol are decreased while serum HDL cholesterol is increased in depression and these changes were more marked in depressed subjects with definite suicidal intent. On regression analysis, total serum cholesterol was the most important predictive variable of the severity of depression.

Successful allogeneic bone marrow transplantation in selected patients over 50 years of age--a single institution's experience

As allogeneic bone marrow transplantation (BMT) is a procedure with a higher risk of morbidity and mortality in older patients, many institutions place a limit of 50 to 55 years for allogeneic BMT. Consequently, older patients may not be offered potentially curative treatment for otherwise poor prognosis diseases such as AML or myelodysplastic syndrome. We compared the outcome of 59 patients aged over 50, 124 aged 40-50, and 253 aged 18-39 years who underwent allogeneic BMT in our institution between August 1987 and April 1996. Our results show little influence of age on outcome when comparing patients over 50 years with patients 40-50 years. Apart from an initial higher transplant mortality rate, overall survival was not significantly different between the three age groups. The 1-year and 2-year overall survival rates were 57% and 48%, 57% and 48%, and 62% and 58% for the >50 years, 40-50 years, and <40 years patients, respectively. The incidence of GVHD was also comparable. We conclude that allogeneic BMT can be performed in selected patients over the age of 50 years with acceptable morbidity and mortality and that older patients should not be denied this treatment based on age alone.

Distinct activated and non-activated RNA polymerase II complexes in yeast

We used a transcriptional run-on assay in permeabilized yeast cells to study the distribution of RNA polymerase II (pol II) complexes before and after activation by Gal4. Polymerases were found engaged on the gene at the 5' end before activation, but only appeared at the 3' end after activation. Mutations of the pol II C-terminal domain (CTD), the CTD kinase Kin28 and the holoenzyme subunit Srb2 all inhibited the formation of 3' polymerases in response to activator. However, these mutations did not inhibit the establishment of polymerases at the 5' end. The differences between 3' and 5' ternary complexes suggest that they represent qualitatively distinct 'activated' and 'non-activated' forms of polymerase. The results implicate CTD phosphorylation in a switch from 'non-activated' transcription, which is confined to the 5' end, to an 'activated' mode that traverses the length of the gene.