Diphthamide-deficiency syndrome: a novel human developmental disorder and ribosomopathy

We describe a novel type of ribosomopathy that is defined by deficiency in diphthamidylation of translation elongation factor 2. The ribosomopathy was identified by correlating phenotypes and biochemical properties of previously described patients with diphthamide biosynthesis gene 1 (DPH1) deficiencies with a new patient that carried inactivating mutations in both alleles of the human diphthamide biosynthesis gene 2 (DPH2). The human DPH1 syndrome is an autosomal recessive disorder associated with developmental delay, abnormal head circumference (microcephaly or macrocephaly), short stature, and congenital heart disease. It is defined by variants with reduced functionality of the DPH1 gene observed so far predominantly in consanguineous homozygous patients carrying identical mutant alleles of DPH1. Here we report a child with a very similar phenotype carrying biallelic variants of the human DPH2. The gene products DPH1 and DPH2 are components of a heterodimeric enzyme complex that mediates the first step of the posttranslational diphthamide modification on the nonredundant eukaryotic translation elongation factor 2 (eEF2). Diphthamide deficiency was shown to reduce the accuracy of ribosomal protein biosynthesis. Both DPH2 variants described here severely impair diphthamide biosynthesis as demonstrated in human and yeast cells. This is the first report of a patient carrying compound heterozygous DPH2 loss-of-function variants with a DPH1 syndrome-like phenotype and implicates diphthamide deficiency as the root cause of this patient's clinical phenotype as well as of DPH1-syndrome. These findings define "diphthamide-deficiency syndrome" as a special ribosomopathy due to reduced functionality of components of the cellular machinery for eEF2-diphthamide synthesis.

Discriminative value of FRAX for fracture prediction in a cohort of Chinese postmenopausal women

We followed 2,266 postmenopausal Chinese women for 4.5 years to determine which model best predicts osteoporotic fracture. A model that contains ethnic-specific risk factors, some of which reflect frailty, performed as well as or better than the well-established FRAX model.

INTRODUCTION

Clinical risk assessment, with or without T-score, can predict fractures in Chinese postmenopausal women although it is unknown which combination of clinical risk factors is most effective. This prospective study sought to compare the accuracy for fracture prediction using various models including FRAX, our ethnic-specific clinical risk factors (CRF) and other simple models.

METHODS

This study is part of the Hong Kong Osteoporosis Study. A total of 2,266 treatment naïve postmenopausal women underwent clinical risk factor and bone mineral density assessment. Subjects were followed up for outcome of major osteoporotic fracture and receiver operating characteristic (ROC) curves for different models were compared. The percentage of subjects in different quartiles of risk according to various models who actually fractured was also compared.

RESULTS

The mean age at baseline was 62.1 ± 8.5 years and mean follow-up time was 4.5 ± 2.8 years. A total of 106 new major osteoporotic fractures were reported, of which 21 were hip fractures. Ethnic-specific CRF with T-score performed better than FRAX with T-score (based on both Chinese normative and National Health and Nutrition Examination Survey (NHANES) databases) in terms of AUC comparison for prediction of major osteoporotic fracture. The two models were similar in hip fracture prediction. The ethnic-specific CRF model had a 10% higher sensitivity than FRAX at a specificity of 0.8 or above.

CONCLUSION

CRF related to frailty and differences in lifestyle between populations are likely to be important in fracture prediction. Further work is required to determine which and how CRF can be applied to develop a fracture prediction model in our population.

Effect of the immune modulating peptide, SCV-07, in the murine B16 melanoma model

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Background: SCV-07 (gamma-D-glutamyl-L-tryptophan) is a synthetic peptide with proven immune stimulating effects and efficacy against various viral and bacterial infections. As several cancers, including melanoma, are known to be sensitive to immune modulation, it was of interest to evaluate the effects of this compound in the murine B16 melanoma model. Methods: Tumors (1x106 B16 melanoma cells) were implanted subcutaneously (sc) into the right axillary area of C57BL/6 mice (Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences, Beijing, P. R. China). SCV-07 was dissolved in phosphate buffered saline (PBS) and administered once daily via sc administration (at a different site from tumor implantation) at doses of 0.01, 0.10, 1.0, or 5.0 mg/kg for 14 consecutive days. Positive control, dacarbazine (DTIC) was given at a dose of 50 mg/kg once daily for 14 consecutive days via sc injection. Tumor size (by caliper) and body weights were measured once every 3 days throughout the study. The study was terminated on day 17, and the animals euthanized. The tumors were excised, separated, and weighed. Results: SCV-07 treatment led to a significant inhibition of tumor growth compared to vehicle control, with decreases of 16.5% (p=0.030) and 30.2% (p=0.014) seen at the highest doses of 1.0 and 5.0 mg/kg, respectively, on day 15 at the end of treatment. Growth inhibition in the DTIC control was 95.1% (p<0.001). Evaluation of tumor weight also demonstrated a significant inhibition by SCV-07, compared to vehicle, of 23.5% (p=0.008) and 30.8% (p=0.015) at dose levels of 1.0 and 5.0 mg/kg SCV-07. DTIC treated animals had a decrease in tumor weight of 85%. Evaluation of animal body weights demonstrated a significant decrease in those treated with DTIC, suggesting a toxic effect, while no decrease was noted in any SCV-07 treatment groups. Conclusions: Administration of SCV-07 once daily for 14 consecutive days via the sc route is effective against B16 melanoma tumor growth. Tumor growth in animals treated with dose levels of 1 or 5 mg/kg of SCV-07 was significantly reduced compared to the vehicle control group. The overall animal body weights were unchanged after treatment with SCV-07, indicating a lack of toxicity of the test article.

No significant financial relationships to disclose.

Suppression of HOX A cluster genes inhibits proliferation and induces cell death in human mixed-lineage leukemias

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Background: Leukemias harboring translocations of the mixed lineage leukemia locus (MLL) are generally associated with poor clinical prognosis. Using gene expression profiling we and others have previously shown that Homeobox (HOX) A cluster genes are highly expressed in leukemias with MLL rearrangements. Methods: Here we studied the role of aberrant HOXA9 expression in human MLL- rearranged and non-rearranged leukemias utilizing an shRNA mediated knockdown approach. Results: Three different shRNA constructs targeting human HOXA9 were synthesized and stably introduced into t(9;11) MOLM14 cells utilizing a lentiviral vector system. 75–80% HOXA9 RNA knockdown was confirmed by quantitative PCR and Western Blot analysis. In a panel of 17 AML/ALL cell lines (7 MLL rearranged, 10 non rearranged), HOXA9 directed shRNA inhibited cell proliferation starting as early as 48h after transduction, and induced apoptosis beginning at 72h. Interestingly, impaired cell proliferation and induction of apoptosis was significantly higher in the MLL rearranged cell lines (mean viability: 51.88%) than in the non-rearranged cells (mean viability: 90.98%; p=0.007) and also significantly correlated with the baseline HOXA9 mRNA expression before knockdown (R= 0.8, p=0.00017). We then further analyzed the effect of HOXA9 knockdown in MLL rearranged and non-rearranged primary human AML cells. Similar to our findings in cell lines, a marked induction of cell death was observed, which was significantly higher in leukemias with an MLL translocation (p=0.005) and also significantly correlated with the baseline HOXA9 mRNA expression (R= 0.8, p=0.001). Next, the in vivo effect of HOXA9 knockdown was assessed by transplanting luciferase-expressing SEMK2 (t4;11) cells into SCID-beige mice followed by in vivo bioluminescent imaging. Leukemia burden was significantly reduced in HOXA9 shRNA treated mice (n=10) with a peak difference at day 15 (p=0.000059) shortly before mice of the control group (n=10) succumbed from overt leukemia. At this point all mice of the HOXA9 shRNA treated group were still healthy with no signs of leukemia. Conclusions: Taken together our data implicates that depletion of HOXA9 might be a novel approach for targeted therapy in human MLL rearranged leukemias.

No significant financial relationships to disclose.

Favorable outcome of allogeneic hematopoietic stem cell transplantation for relapsed or refractory acute promyelocytic leukemia in childhood

The optimal therapy for children with relapsed or refractory acute promyelocytic leukemia (APL) is unclear. We therefore reviewed our institutional outcomes for children undergoing allogeneic hematopoietic stem cell transplantation (HSCT) for advanced APL. Between 1986 and 2003, 12 allogeneic HSCTs (five related donor, seven unrelated donor) were performed for 11 patients (median age, 13 years) with relapsed (n = 8) or refractory (n = 3) APL. All patients engrafted, after a median of 18.5 days. Grade B-D acute graft-versus-host disease (GVHD) developed after five transplants (42%; 90% CI, 18-68%), and the cumulative incidence of chronic GVHD was 45% (90% CI, 19-71%). The cumulative incidence of overt relapse post-HSCT was 10% (90% CI, 0-28%). The overall 5-year survival was 73% (90% confidence interval (CI), 51-95%), with a median post-HSCT follow-up of 64 months. The Lansky/Karnofsky performance scores are 100% in six of eight survivors. In view of the low risk of subsequent relapse and favorable survival suggested by other reports and our own experience, we continue to recommend allogeneic HSCT for children with advanced APL for whom a suitably HLA-matched donor is identified.

A simple tool to identify asian women at increased risk of osteoporosis

Patients with low bone mineral density (BMD) have a high risk of future fractures, and should be actively considered for treatment to reduce their risk. However, BMD measurements are not widely available in some communities, because of cost and lack of equipment. Simple questionnaires have been designed to help target high-risk women for BMD measurements, thereby avoiding the cost of measuring women at low risk. However, such tools have previously focused on evaluation of non-Asian women. We collected information about numerous risk factors from postmenopausal Asian women in eight countries in Asia using questionnaires, and evaluated the ability of these risk factors to identify women with osteoporosis as defined by femoral neck BMD T-scores < or =-2.5. Multiple variable regression analysis and item reduction yielded a final tool based on only age and body weight. This risk index had a sensitivity of 91% and specificity of 45%, with an area under the curve of 0.79. Previously published risk indices based on larger numbers of variables performed similarly well in this Asian population. Large differences in risk were identified using our index to create three categories: 61% of the high-risk women had osteoporosis, compared with only 15% and 3% of the intermediate- and low-risk women, respectively. The low-risk group represented 40% of all women, for whom BMD measurements are probably not needed unless important risk factors, such as prior nonviolent fracture or corticosteroid use, are present. An existing population-based sample of postmenopausal Japanese women was used to validate our index. In this sample of Japanese women the sensitivity was 98% and specificity was 29%; the low-risk category, for whom BMD is probably unnecessary, represented 25% of all women. We conclude that our index performed well for classifying the risk of osteoporosis among postmenopausal Asian women and applying it would result in more prudent use of BMD technology.

Life, death and genomic change in perturbed cell cycles

HeLaS3 cells undergo apoptosis after 18-24 h of cell cycle stasis irrespective of the agent employed (colcemid, aphidicolin, cis-platin). At high drug concentrations apoptosis occurs in cells arrested in the cell cycle in which the drug is applied and at a cell cycle position dependent on the mechanism of drug action. At low concentrations (or short exposure times) cells undergo apoptosis after progressing through an aberrant mitosis and only after 18 h of cell cycle stasis in a 'pseudo G1/S' cell cycle position. Aberrent mitoses result in multipolar mitoses, chromosomal breakage and interchromosomal concatenation events. We propose that the ability of cells to delay progression into aberrent mitosis, as well as their propensity to undergo apoptosis, are important determinants of clinical cytotoxicity. We also suggest that apoptosis plays an important role in preventing the generation of aneuploidy and recombination and rearrangement events commonly associated with cancer.

Decreased bone mineral density in premenopausal asthma patients receiving long-term inhaled steroids

Inhaled corticosteroids have become a key element in the maintenance treatment of bronchial asthma. It is well-known that long-term systemic steroid use causes osteoporosis, whereas its inhaled counterpart has been believed to be devoid of such a side-effect. However, recent studies showed that administration of inhaled corticosteroids was associated with biochemical evidence of derangement in bone turnover. We therefore studied bone mineral density (BMD) by dual energy x-ray absorptiometry in 30 patients (18 females, 12 males) with bronchial asthma treated with steroids, essentially by the inhaled route only (both nasal and tracheobronchial), and compared them with healthy subjects individually matched for age, sex, menopausal status, and body mass index (BMI). There was a significant decrease in BMD in the patient group at the hip (neck of femur, p = 0.007; trochanter of femur, p = 0.034; Ward's triangle, p = 0.016) and the lumbar area of the spine (L2-4, p = 0.041). Further analysis showed that this difference from control subjects was mainly seen in the female patients and not in the male patients (neck of femur, p = 0.049; Ward's triangle, p = 0.025; lumbar spine, p = 0.039). In the female patients, there was significant negative correlation of BMD of the lumbar area of the spine and the trochanter of femur with daily inhaled steroid dose and positive correlation of BMD of the trochanter with BMI.

An assessment of drug information sheets for diabetic patients: only active involvement by patients is helpful

Insulin/sulphonylurea-treated diabetics attending a busy university diabetic clinic were studied to determine whether issuing drug information sheets and/or age influenced understanding and behaviour regarding their disease and its treatment, especially with respect to avoiding hypoglycaemia. Patients were each asked 10 basic questions (each correct answer scoring 1), stratified by age (20 were less than or equal to 45 years and 91 greater than 45 years). According to a single-blind randomised protocol, they were issued or not issued with drug information sheets (providing information to correctly answer all 10 questions). After 2-3 months, 107 (88 aged greater than 45 years) were retested and asked whether they recalled an information sheet, read it themselves or had it read to them. Whether or not patients received sheets, corresponding mean aggregate scores were very similar in both age groups and there was no correlation with age. Second test scores yielded clinically and statistically significant increments in both the sheet and no sheet groups, respective mean aggregate scores increasing from 4.48 to 5.80 and 5.14 to 6.27 (P less than 0.001). Among patients issued with sheets, 32 who recalled reading them achieved the greatest improvement in mean scores (4.53 to 6.16, P less than 0.001). Active interaction/communication (participation in first test, recall and reading of information sheet) had a favourable educational impact irrespective of age, but merely issuing drug information sheets had no benefit.

Glomerulonephropathy of Laurence-Moon-Biedl syndrome

A patient with Laurence-Moon-Biedl syndrome and nephrotic range proteinuria is presented. Radiological investigation of the urinary tract revealed clubbed calyces but no evidence of obstruction or vesicoureteric reflux. Renal biopsy revealed occasional sclerotic glomeruli, extensive foot-process fusion and segmental glomerular basement membrane abnormalities with negative immunofluorescence for immunoglobulins and complement. Nephrotic proteinuria responded to steroid therapy but mild proteinuria persisted. The findings were consistent with minimal change nephropathy superimposed on the glomerular lesions of Lawrence-Moon-Biedl syndrome.