Elevated plasma and synovial fluid interleukin-8 and interleukin-18 may be associated with the pathogenesis of knee osteoarthritis

PURPOSE

Osteoarthritis (OA) of the knee is a multifactorial degenerative disease typically defined as the 'wear and tear' of articular joint cartilage. However, recent studies suggest that OA is a disease arising from chronic low-grade inflammation. We conducted a study to investigate the relationship between chronic inflammatory mediators present in both the systemic peripheral blood system and localised inflammation in synovial fluid (SF) of OA and non-OA knees; and subsequently made direct comparative analyses to understand the mechanisms that may underpin the processes involved in OA.

METHODS

20-Plex proteins were quantified using Human Magnetic Luminex® assay (R&D Systems, USA) from plasma and SF of OA (n = 14) and non-OA (n = 14) patients. Ingenuity Pathway Analysis (IPA) software was used to predict the relationship and possible interaction of molecules pertaining to OA.

RESULTS

There were significant differences in plasma level for matrix metalloproteinase (MMP)-3, interleukin (IL)-27, IL-8, IL-4, tumour necrosis factor-alpha, MMP-1, IL-15, IL-21, IL-10, and IL-1 beta between the groups, as well as significant differences in SF level for IL-15, IL-8, vascular endothelial growth factor (VEGF), MMP-1, and IL-18. Our predictive OA model demonstrated that toll-like receptor (TLR) 2, macrophage migration inhibitory factor (MIF), TLR4 and IL-1 were the main regulators of IL-1B, IL-4, IL-8, IL-10, IL-15, IL-21, IL-27, MMP-1 and MMP-3 in the plasma system; whilst IL-1B, TLR4, IL-1, and basigin (BSG) were the regulators of IL-4, IL-8, IL-10, IL-15, IL-18, IL-21, IL-27, MMP-1, and MMP-3 in the SF system.

CONCLUSION

The elevated plasma IL-8 and SF IL-18 may be associated with the pathogenesis of OA via the activation of MMP-3.

Frequency of BRCA1 and BRCA2 Germline Variants in Women With Ovarian Cancer in Malaysia

Background: Germline BRCA1 or BRCA2 pathogenic variants in ovarian cancer patients may be informative in risk management and treatment, with the advent of poly(ADP-ribose) polymerase inhibitors. In the era of precision medicine, companion diagnostics for BRCA1 and BRCA2 genes have been featured as a strategy in the Malaysia National Strategic Plan for Cancer Control Program (2016-2020). To facilitate this strategy, frequency data from Malaysia's understudied multiethnic population will be required. Aim: To determine the prevalence of BRCA1 and BRCA2 germline variants in a population-based cohort of ovarian cancer patients in Malaysia. Methods: From August 2016, women with nonmucinous epithelial ovarian, peritoneal or fallopian tube carcinoma are prospectively recruited to the Malaysia-wide population-based MaGiC Observational Study. DNA were tested using a Hi-Plex next generation sequencing method and multiplex ligation-dependent probe amplification to detect < 10 bp alterations and exon deletions or duplications in the BRCA1 and BRCA2 genes. Results: Interim results from 325 patients tested until March 2018 have identified BRCA1 and BRCA2 pathogenic variants in 9.8% (32/325) and 3.1% (10/325) patients, respectively. Variants of uncertain significance were detected in 13.2% (43/325) patients and no pathogenic variants were detected in 73.8% (240/325) patients. Taken together, the frequency of BRCA1/2 pathogenic variants in ovarian cancer patients is approximately 12.9% (42/325). Conclusion: The identification of BRCA1 or BRCA2 carriers across the country have enabled the concentration of efforts from limited genetic counseling resources to high risk families. Results arising from the completion of this study will supplement cancer control programs and genetic services in Malaysia.

Patient-Reported Outcome Measures Among Breast Cancer Survivors in Malaysia: A Comparative Study With Patients From High-Income Countries

Background: Patient-reported outcome measures (PROMs) are essential for identifying how patients perceive the outcomes of their cancer treatment, and is the ultimate success of cancer care. Although a growing number of studies have focused on PROMs in high income countries (HICs), outcomes relevant to patients in developing countries are less understood. Furthermore, the lack of standardization in PROMs makes it difficult to interpret these data for research or quality monitoring. Aim: In this study, we compared the results of PROM measures between patients in Malaysia, a middle income country, and those in HICs, using standard PROMs questionnaires. We also explored the differences in perceived importance of patient reported outcomes within the multiracial Malaysian cohort. Methods: Breast cancer patients (n=1063) were recruited in hospitals serving suburban areas of Malaysia. Of these, 969 patients were eligible for analysis. The surveys were conducted through face-to-face interviews (68%) or were self-administered (30%). An outcome was considered important if it was scored between 7-9 on a 9-point Likert scale. We compared PROMs scores between Malaysian patients and data previously collected from patients in HICs using logistic regression models, adjusting for demographic and clinical characteristics. A two-step cluster analysis was conducted to explore differences in the perceived importance of PROMs between clusters of Malaysian patients. Results: Compared with 1777 patients from HICs, Malaysian patients were less likely to rate overall and recurrence free survival, as well as emotional, cognitive, social and sexual functioning as very important outcomes. Interestingly, more Malaysian women reported that pain (50% vs. 39%), breast symptoms (51% vs. 35%), and major complications (60% vs. 44%) were very important outcomes ( P < 0.001). Compared with young, married Malaysian women, the cluster of older married women (mean age of 57 vs. 52), who were less likely to have received breast reconstructive surgery (8.6% vs. 16.8%), was more likely to rate sexual functioning (32.8% vs. 25.0%, P = 0.036), body image (63.9% vs. 42.4%, P < 0.001), and satisfaction with the breast (50.7% vs. 37.0%, P = 0.011) as very important outcomes. Conclusion: The differences in breast cancer patient needs between and within populations should be considered carefully to better clinician-patient relationship, patient care and satisfaction and assess the outcomes of our cancer care. Future research is needed to find suitable targeted interventions to identify and address the diverse needs of breast cancer patients in low and middle income countries.

Identification of germline alterations in breast cancer predisposition genes among Malaysian breast cancer patients using panel testing

Although an association between protein-truncating variants and breast cancer risk has been established for 11 genes, only alterations in BRCA1, BRCA2, TP53 and PALB2 have been reported in Asian populations. Given that the age of onset of breast cancer is lower in Asians, it is estimated that inherited predisposition to breast cancer may be more significant. To determine the potential utility of panel testing, we investigated the prevalence of germline alterations in 11 established and 4 likely breast cancer genes in a cross-sectional hospital-based cohort of 108 moderate to high-risk breast cancer patients using targeted next generation sequencing. Twenty patients (19%) were identified to carry deleterious mutations, of whom 13 (12%) were in the BRCA1 or BRCA2, 6 (6%) were in five other known breast cancer predisposition genes and 1 patient had a mutation in both BRCA2 and BARD1. Our study shows that BRCA1 and BRCA2 account for the majority of genetic predisposition to breast cancer in our cohort of Asian women. Although mutations in other known breast cancer genes are found, the functional significance and breast cancer risk have not yet been determined, thus limiting the clinical utility of panel testing in Asian populations.

Frequent occurrence of gastric cancer in Asian kindreds with Li-Fraumeni syndrome

Type of cancer and age of onset in individuals with inherited aberrations in the tumour suppressor gene TP53 are variable, possibly influenced by genetic modifiers and different environmental exposure. Since 2009, the modified Chompret criteria (MCC) have been used to identify individuals for TP53 mutation screening. Using the TP53 mutation database maintained by the International Agency for Research on Cancer (IARC), we investigated if the MCC, mainly developed for a Caucasian population, was also applicable in Asia. We identified several differences in Asian families compared with similar Caucasian cohorts, suggesting that identification and management of Li-Fraumeni syndrome in Asia do not completely mirror that of North America and Western Europe. Early gastric cancer (<40 years) may be considered a new addition to the MCC especially for Asian families.

A review of breast cancer research in malaysia

Four hundred and nineteen articles related to breast cancer were found in a search through a database dedicated to indexing all original data relevant to medicine published in Malaysia between the years 2000-2013. One hundred and fifty four articles were selected and reviewed on the basis of clinical relevance and future research implications. Overall, Malaysian women have poor survival from breast cancer and it is estimated that half of the deaths due to breast cancer could be prevented. Five-year survival in Malaysia was low and varies among different institutions even within the same disease stage, suggesting an inequity of access to optimal treatment or a lack of compliance to optimal treatment. Malaysian women have poor knowledge of the risk factors, symptoms and methods for early detection of breast cancer, leading to late presentation. Moreover, Malaysian women experience cancer fatalism, belief in alternative medicine, and lack of autonomy in decision making resulting in delays in seeking or avoidance of evidence-based medicine. There are ethnic differences in estrogen receptor status, HER2 overexpression and incidence of triple negative breast cancer which warrant further investigation. Malay women present with larger tumours and at later stages, and even after adjustment for these and other prognostic factors (stage, pathology and treatment), Malay women have a poorer survival. Although the factors responsible for these ethnic differences have not been elucidated, it is thought that pharmacogenomics, lifestyle factors (such as weight-gain, diet and exercise), and psychosocial factors (such as acceptance of 2nd or 3rd line chemotherapy) may be responsible for the difference in survival. Notably, survivorship studies show self-management programmes and exercise improve quality of life, highlighting the need to evaluate the psychosocial impact of breast cancer on Malaysian women, and to design culturally-, religiously- and linguistically-appropriate psycho-education programmes to help women cope with the disease and improve their quality of life. Research done in the Caucasian populations may not necessarily apply to local settings and it is important to embark on local studies particularly prevention, screening, diagnostic, prognostic, therapeutic and psychosocial research.

FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium

BACKGROUND

Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium.

METHODS

Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression.

RESULTS

Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95% confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2.

CONCLUSION

Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2.

Targeted prostate cancer screening in men with mutations in BRCA1 and BRCA2 detects aggressive prostate cancer: preliminary analysis of the results of the IMPACT study

OBJECTIVE

To evaluate the role of targeted prostate cancer screening in men with BRCA1 or BRCA2 mutations, an international study, IMPACT (Identification of Men with a genetic predisposition to ProstAte Cancer: Targeted screening in BRCA1/2 mutation carriers and controls), was established. This is the first multicentre screening study targeted at men with a known genetic predisposition to prostate cancer. A preliminary analysis of the data is reported.

PATIENTS AND METHODS

Men aged 40-69 years from families with BRCA1 or BRCA2 mutations were offered annual prostate specific antigen (PSA) testing, and those with PSA > 3 ng/mL, were offered a prostate biopsy. Controls were men age-matched (± 5 years) who were negative for the familial mutation.

RESULTS

In total, 300 men were recruited (205 mutation carriers; 89 BRCA1, 116 BRCA2 and 95 controls) over 33 months. At the baseline screen (year 1), 7.0% (21/300) underwent a prostate biopsy. Prostate cancer was diagnosed in ten individuals, a prevalence of 3.3%. The positive predictive value of PSA screening in this cohort was 47·6% (10/21). One prostate cancer was diagnosed at year 2. Of the 11 prostate cancers diagnosed, nine were in mutation carriers, two in controls, and eight were clinically significant.

CONCLUSIONS

The present study shows that the positive predictive value of PSA screening in BRCA mutation carriers is high and that screening detects clinically significant prostate cancer. These results support the rationale for continued screening in such men.

Clinical and pathologic differences between BRCA1-, BRCA2-, and non-BRCA-associated breast cancers in a multiracial developing country

BACKGROUND

Mutations in BRCA1 and BRCA2 confer an increased risk to breast and other cancers, but to date there have only been limited numbers of studies of BRCA1- and BRCA2-associated cancers among Asians. Malaysia is a multiracial country with three main races: Malays, Chinese, Indians. We determined whether tumor pathologic features and clinical features differ in patients with and without BRCA mutations in this Asian population.

METHODS

We conducted a retrospective review of the medical records of 152 women with breast cancer who underwent genetic testing for BRCA mutations. The patients self-reported ethnicity, age at onset, and clinical stage at diagnosis and tumor pathology were reviewed.

RESULTS

A total of 31 patients carried germline deleterious mutations (16 BRCA1, 15 BRCA2). We found that tumors in BRCA1 carriers were more likely to be estrogen receptor (ER)-negative and progesterone receptor (PR)-negative. HER2 was more likely to be negative in both BRCA1 and BRCA2 subjects compared with non-BRCA subjects. We found a strong association between triple-negative status and BRCA1 carriers. In addition, tumors in BRCA1 carriers were more likely to be higher grade than those in BRCA2 and non-BRCA carriers; but the difference was not statistically significant.

CONCLUSIONS

These results suggest that tumors associated with BRCA1 mutations are distinct from those of BRCA2-associated and non-BRCA-associated breast cancers, and that the tumors associated with BRCA2 mutations are similar to the non-BRCA-associated breast cancers. Further studies are required to determine if the prognosis is different in each of these groups and the best management strategy for each group.

Clinical characteristics of triple-negative breast cancer: experience in an Asian developing country

INTRODUCTION

Triple negative (TN) breast cancers are defined by a lack of expression of oestrogen, progesterone, and HER2 receptors. They tend to have a higher grade, with a poorer outcome compared to non-TN breast cancers.

OBJECTIVE

The aim of this study is to determine the incidence of TN breast cancer in an Asian country consisting of Malays, Chinese and Indians, and to determine the factors associated with this type of breast cancer.

RESULTS

The incidence of TN breast cancer in the University Malaya Medical Center is 17.6%. There is no significant difference amongst the Malays, Chinese and Indians. In bivariate analysis, TN breast cancer was significantly associated with younger age and Grade 3. However, in multivariate analysis using logistic regression, TN breast cancer was only associated with Grade 3.

CONCLUSION

The incidence of TN breast cancer in our study is similar to other studies, and associated with a higher grade.

Gene expression in human oral squamous cell carcinoma is influenced by risk factor exposure

Oral squamous cell carcinoma (OSCC) is a world health problem and is associated with exposure to different risk factors. In the west, smoking and alcohol consumption are considered to be the main risk factors whilst in India and southeast Asia, betel quid (BQ) chewing is predominant. In this study, we compared the gene expression patterns of oral cancers associated with BQ chewing to those caused by smoking using Affymetrix microarrays. We found that 281 genes were differentially expressed between OSCC and normal oral mucosa regardless of aetiological factors including MMP1, PLAU, MAGE-D4, GNA12, IFITM3 and NMU. Further, we identified 168 genes that were differentially expressed between the BQ and smoking groups including CXCL-9, TMPRSS2, CA12 and RNF24. The expression of these genes was validated using qPCR using independent tissue samples. The results demonstrate that whilst common genes/pathways contribute to the development of oral cancer, there are also other gene expression changes that are specific to certain risk factors. The findings suggest that different carcinogens activate or inhibit specific pathways during cancer development and progression. These unique gene expression profiles should be taken into consideration when developing biomarkers for future use in prognostic or therapeutic applications.

Evaluation of BRCA1 and BRCA2 mutations and risk-prediction models in a typical Asian country (Malaysia) with a relatively low incidence of breast cancer

INTRODUCTION

The cost of genetic testing and the limited knowledge about the BRCA1 and BRCA2 genes in different ethnic groups has limited its availability in medium- and low-resource countries, including Malaysia. In addition, the applicability of many risk-assessment tools, such as the Manchester Scoring System and BOADICEA (Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm) which were developed based on mutation rates observed primarily in Caucasian populations using data from multiplex families, and in populations where the rate of breast cancer is higher, has not been widely tested in Asia or in Asians living elsewhere. Here, we report the results of genetic testing for mutations in the BRCA1 or BRCA2 genes in a series of families with breast cancer in the multi-ethnic population (Malay, Chinese and Indian) of Malaysia.

METHOD

A total of 187 breast cancer patients with either early-onset breast cancer (at age </= 40 years) or a personal and/or family history of breast or ovarian cancer were comprehensively tested by full sequencing of both BRCA1 and BRCA2. Two algorithms to predict the presence of mutations, the Manchester Scoring System and BOADICEA, were evaluated.

RESULTS

Twenty-seven deleterious mutations were detected (14 in BRCA1 and 13 in BRCA2), only one of which was found in two unrelated individuals (BRCA2 490 delCT). In addition, 47 variants of uncertain clinical significance were identified (16 in BRCA1 and 31 in BRCA2). Notably, many mutations are novel (13 of the 30 BRCA1 mutations and 24 of the 44 BRCA2). We report that while there were an equal proportion of BRCA1 and BRCA2 mutations in the Chinese population in our study, there were significantly more BRCA2 mutations among the Malays. In addition, we show that the predictive power of the BOADICEA risk-prediction model and the Manchester Scoring System was significantly better for BRCA1 than BRCA2, but that the overall sensitivity, specificity and positive-predictive value was lower in this population than has been previously reported in Caucasian populations.

CONCLUSION

Our study underscores the need for larger collaborative studies among non-Caucasian populations to validate the role of genetic testing and the use of risk-prediction models in ensuring that the other populations in the world may also benefit from the genomics and genetics era.

p53 Status does not affect photodynamic cell killing induced by hypericin

PURPOSE

Given that p53 is a tumor suppressor that plays a central role in the cellular response to DNA damage and that more than 50% of all cancers have mutated p53, the wider utility of photodynamic therapy (PDT) in the treatment of cancer will depend on an understanding of whether p53 status modulates response to PDT. In this study, we investigated the photosensitivity of isogenic cell lines that differ only in their p53 status to PDT using hypericin as the photosensitizer.

METHODS

Acute (MTT) and chronic (clonogenic) cytotoxic assays were performed on two osteosarcoma cell-lines (U2OS and U2OS+p53DD) that are isogenic except that the latter expresses dominant negative p53. The inducible expression of p53 was determined on western blots. Uptake of hypericin, cell cycle profile analysis, measurement of membrane phosphatidylserine externalization and changes in mitochondrial membrane potential were investigated using flow cytometry.

RESULTS

Hypericin uptake was observed to be equivalent in U2OS and U2OS+p53DD cells. There were no significant differences in cell killing between these cell-lines in both the MTT and clonogenic assays (IC(50) of 0.4 microg/ml from MTT assay). p53 expression did not increase up to 24 h after PDT treatment in both cell lines. There were also no significant differences in the cell-cycle arrest profiles and timing of onset of apoptosis.

CONCLUSIONS

Taken together, these results suggest that the status of p53 may not be important in PDT-mediated cell killing or induction of apoptosis. By extension, these results imply that PDT may be used with equal efficacy for the treatment of p53-positive and -negative tumors.

Tissue-limited mosaicism in Pallister-Killian syndrome -- a case in point

We report a case of Pallister-Killian syndrome in a term female infant. Antenatal ultrasound showed left diaphragmatic hernia and polyhydramnios. She was ventilated from birth and the diaphragm defect repaired on day 5. She had dysmorphic features, including median cleft palate, patchy frontotemporal alopecia, hypopigmented skin whorls, and bilateral profound sensorineural hearing loss. Fetal and postnatal karyotypes of peripheral lymphocytes were both normal, 46, XX. Subsequently, a skin fibroblast culture showed mosaic tetrasomy of isochromosome 12p both on G-banding and fluorescence in situ hybridization, consistent with Pallister-Killian syndrome. This case illustrates the importance of using the appropriate sample type for karyotype analysis with implications for prenatal and postnatal diagnosis.

Telomerase subunit overexpression suppresses telomere-specific checkpoint activation in the yeast yku80 mutant

Ku is a conserved heterodimeric DNA-binding protein that plays critical roles in DNA repair and telomere homeostasis. In Saccharomyces cerevisiae, deletion of YKU70 or YKU80 results in an inability to grow at 37 degrees C. This is suppressed by overexpression of several components of telomerase (EST1, EST2 and TLC1). We show that overexpression of EST2 or TLC1 in yku80 mutants does not restore efficient DNA repair, or restore normal telomere function, as measured by telomere length, single-stranded G-rich strand or transcriptional silencing. Instead, yku80 mutants activate a Rad53p-dependent DNA-damage checkpoint at 37 degrees C and this is suppressed by overexpression of EST2 or TLC1. Indeed, deletion of genes required for Rad53p activation also suppresses the yku80 temperature sensitivity. These results suggest that activation of the DNA-damage checkpoint in yku mutants at 37 degrees C does not result from reduced telomere length per se, but reflects an alteration of the telomere structure that is recognized as damaged DNA.

Lif1p targets the DNA ligase Lig4p to sites of DNA double-strand breaks

DNA ligases catalyse the joining of DNA single- and double-strand breaks. Saccharomyces cerevisiae Cdc9p is a homologue of mammalian DNA ligase I and is required for DNA replication, recombination and single-strand break repair. The other yeast ligase, Lig4p/Dnl4p, is a homologue of mammalian DNA ligase IV, and functions in the non-homologous end-joining (NHEJ) pathway of DNA double-strand break repair [1] [2] [3] [4]. Lig4p interacts with Lif1p, the yeast homologue of the human ligase IV-associated protein, XRCC4 [5]. This interaction takes place through the carboxy-terminal domain of Lig4p and is required for Lig4p stability. We show that the carboxy-terminal interaction region of Lig4p is necessary for NHEJ but, when fused to Cdc9p, is insufficient to confer NHEJ function to Cdc9p. Also, Lif1p stimulates the in vitro catalytic activity of Lig4p in adenylation and DNA ligation. Nevertheless, Lig4p is inactive in NHEJ in the absence of Lif1p in vivo, even when Lig4p is stably expressed. We show that Lif1p binds DNA in vitro and, through in vivo cross-linking and chromatin immuno precipitation assays, demonstrate that it targets Lig4p to chromosomal DNA double-strand breaks. Furthermore, this targeting requires another key NHEJ protein, Ku.

Purification and DNA binding properties of the ataxia-telangiectasia gene product ATM

The human neurodegenerative and cancer predisposition condition ataxia-telangiectasia is characterized at the cellular level by radiosensitivity, chromosomal instability, and impaired induction of ionizing radiation-induced cell cycle checkpoint controls. Recent work has revealed that the gene defective in ataxia-telangiectasia, termed ATM, encodes an approximately 350-kDa polypeptide, ATM, that is a member of the phosphatidylinositol 3-kinase family. We show that ATM binds DNA and exploit this to purify ATM to near homogeneity. Atomic force microscopy reveals that ATM exists in two populations, with sizes consistent with monomeric and tetrameric states. Atomic force microscopy analyses also show that ATM binds preferentially to DNA ends. This property is similar to that displayed by the DNA-dependent protein kinase catalytic subunit, a phosphatidylinositol 3-kinase family member that functions in DNA damage detection in conjunction with the DNA end-binding protein Ku. Furthermore, purified ATM contains a kinase activity that phosphorylates serine-15 of p53 in a DNA-stimulated manner. These results provide a biochemical assay system for ATM, support genetic data indicating distinct roles for DNA-dependent protein kinase and ATM, and suggest how ATM may signal the presence of DNA damage to p53 and other downstream effectors.

Identification of a defect in DNA ligase IV in a radiosensitive leukaemia patient

The major mechanism for the repair of DNA double-strand breaks (DSBs) in mammalian cells is non-homologous end-joining (NHEJ), a process that involves the DNA-dependent protein kinase [1] [2], XRCC4 and DNA ligase IV [3] [4] [5] [6]. Rodent cells and mice defective in these components are radiation-sensitive and defective in V(D)J-recombination, showing that NHEJ also functions to rejoin DSBs introduced during lymphocyte development [7] [8]. 180BR is a radiosensitive cell line defective in DSB repair, which was derived from a leukaemia patient who was highly sensitive to radiotherapy [9] [10] [11]. We have identified a mutation within a highly conserved motif encompassing the active site in DNA ligase IV from 180BR cells. The mutated protein is severely compromised in its ability to form a stable enzyme-adenylate complex, although residual activity can be detected at high ATP concentrations. Our results characterize the first patient with a defect in an NHEJ component and suggest that a significant defect in NHEJ that leads to pronounced radiosensitivity is compatible with normal human viability and does not cause any major immune dysfunction. The defect, however, may confer a predisposition to leukaemia.

DNA-binding properties of the tandem HMG boxes of high-mobility-group protein 1 (HMG1)

High-mobility-group protein 1 (HMG1) is a conserved chromosomal protein with two homologous DNA-binding HMG-box domains, A and B, linked by a short basic region to an acidic carboxy-terminal tail. NMR spectroscopy on the free didomain (AB) shows that the two HMG boxes do not interact. The didomain has a higher affinity for all DNA substrates tested than single HMG-box domains and has a significantly higher ability to distort DNA by bending and supercoiling. The interaction of the didomain with DNA is stabilized by the presence of the basic region (approximately 20 residues, 9 of which are Lys) that links the second HMG box to the acidic tail in intact HMG1; this may be, at least in part, why this region also enhances supercoiling of relaxed circular DNA by the didomain and circularization of short DNA fragments (in the presence of ligase). Competition assays suggest significantly different structure-specific preferences of single and tandem HMG boxes for four-way junction and supercoiled plasmid DNA. Binding to supercoiled DNA appears to be promoted by protein oligomerization, which is pronounced for the didomains. Electron microscopy suggests that the oligomers are globular aggregates, associated with DNA looping. One box versus two (or several) is likely to be an important determinant of the properties of (non-sequence specific) HMG-box proteins.

Ecthyma gangrenosum in a patient with hypogammaglobulinemia

Ecthyma gangrenosum is a characteristic skin lesion that is caused by Pseudomonas aeruginosa (P. aeruginosa) in the majority of cases. Systemic P. aeruginosa usually complicates debilitating conditions like leukaemia, burns and cystic fibrosis. We report a patient with underlying hypogammaglobulinemia who developed ecthyma gangrenosum secondary to P. aeruginosa septicaemia, which was potentially life-threatening. Recognition of the characteristic skin lesions with prompt initiation of appropriate antibiotics and intravenous immunoglobulins were life-saving. A review of the English literature reports three other cases of ecthyma gangrenosum in patients with underlying hypogammaglobulinemia.

Identification of Saccharomyces cerevisiae DNA ligase IV: involvement in DNA double-strand break repair

DNA ligases catalyse the joining of single and double-strand DNA breaks, which is an essential final step in DNA replication, recombination and repair. Mammalian cells have four DNA ligases, termed ligases I-IV. In contrast, other than a DNA ligase I homologue (encoded by CDC9), no other DNA ligases have hitherto been identified in Saccharomyces cerevisiae. Here, we report the identification and characterization of a novel gene, LIG4, which encodes a protein with strong homology to mammalian DNA ligase IV. Unlike CDC9, LIG4 is not essential for DNA replication, RAD52-dependent homologous recombination nor the repair of UV light-induced DNA damage. Instead, it encodes a crucial component of the non-homologous end-joining (NHEJ) apparatus, which repairs DNA double-strand breaks that are generated by ionizing radiation or restriction enzyme digestion: a function which cannot be complemented by CDC9. Lig4p acts in the same DNA repair pathway as the DNA end-binding protein Ku. However, unlike Ku, it does not function in telomere length homeostasis. These findings indicate diversification of function between different eukaryotic DNA ligases. Furthermore, they provide insights into mechanisms of DNA repair and suggest that the NHEJ pathway is highly conserved throughout the eukaryotic kingdom.

Williams syndrome--the Singapore General Hospital experience

Williams syndrome first described in 1961 is generally characterised by mental deficiency, gregarious personality, unusual "elfin" facies, supravalvular aortic stenosis and idiopathic infantile hypercalcaemia. Patients with Williams syndrome show a hemizygous submicroscopic deletion of 7q11.23 detectable by fluorescent in-situ hybridisation (FISH). The deleted portion of the chromosome corresponds to the Elastin gene. We report 3 girls with characteristics of Williams syndrome in whom the diagnosis was confirmed by demonstration of the hemizygous deletion of 7q11.23 in the karyotype by FISH. These patients, aged 6, 7 and 10 years, showed the characteristic facies and gregarious personalities. Some developmental delay with mild mental deficiency and dysmorphic facies were prominent features in the initial presentation. Cardiac lesions found in these patients were small patent ductus arteriosus which closed, pulmonary valvular stenosis and mitral valve prolapse associated with mitral regurgitation respectively. Hypercalcaemia was not documented in these patients. Learning difficulty was a major issue and all patients required special schooling. Chromosome analyses done on peripheral blood were found to be normal in all patients. FISH using the Elastin Williams Syndrome Chromosome Region (WSCR) probes (oncor) showed the hemizygous deletion of 7q11.23. Diagnosis of Williams syndrome can now be confidently confirmed with the help of FISH.

First prenatal diagnosis of the carnitine transporter defect

We report the first attempt at prenatal diagnosis of the carnitine transporter defect in a fetus at high risk of having the disorder. Analysis of cultured CVS after prolonged culture predicted that the fetus was not affected but might be heterozygous for the carnitine transporter defect, but chromosome 15 satellite DNA markers showed no paternal contribution, suggesting that the CVS cells assayed were of predominantly maternal origin. Subsequent assay of cultured amniocytes predicted that the fetus would be affected, and this was confirmed in the newborn period. We conclude that prenatal diagnosis of the carnitine transporter defect is possible, but where results depend on extended culture of CVS, molecular studies should be performed to confirm genetic contributions from both parents.

Two mutations in the HMG-box with very different structural consequences provide insights into the nature of binding to four-way junction DNA

Mutation of the highly conserved tryptophan residue in the A-domain HMG-box of HMG1 largely, but not completely, destroys the protein tertiary structure and abolishes its supercoiling ability, but does not abolish structure-specific DNA binding to four-way junctions. Circular dichroism shows that the protein has some residual alpha-helix (< 10%) and does not re-fold in the presence of DNA. Structure-specific DNA binding might therefore be a property of some primary structure element, for example the N-terminal extended strand, which even in the unfolded protein would be held in a restricted conformation by two, largely trans, X-Pro peptide bonds. However, mutation of P5 or P8 of the A-domain to alanine does not abolish the formation of the (first) complex in a gel retardation assay, which probably arises from binding to the junction cross-over, although the P8 mutation does affect the formation of higher complexes which may arise from binding to the junction arms. Since mutation of P8 in the W49R mutant has no effect on structure-specific junction binding, we propose that some residual alpha-helix in the protein might be involved, implicating this element in the interactions of HMG-boxes generally with DNA.

Differences in the DNA-binding properties of the HMG-box domains of HMG1 and the sex-determining factor SRY

High-mobility-group protein 1 (HMG1) is an abundant, non-sequence-specific, chromosomal protein with two homologous, HMG-box, DNA-binding domains, A and B, and an acidic tail. The HMG-box motif also occurs, as a single copy, in some sequence-specific transcription factors, e.g. the sex-determining factor, SRY. We have investigated whether or not there are differences in the DNA-binding properties of the isolated A and B HMG-box domains of HMG1 and SRY and whether, in the case of A and B, there might also be differences due to different sequence contexts within the native protein. The basic regions that flank the HMG1 B box, giving B', enhance its DNA-binding, supercoiling and DNA-bending activities, and promote the self-association of the DNA-bound B-box. All the HMG-box domains bind with structure specificity to four-way junctions, but the structure selectivity is significantly greater for A and the SRY box than for the HMG1 B or B' domains, as judged by competition with excess plasmid DNA. The domains self-associate to different extents on supercoiled DNA and this may explain differences in the ability to discriminate between four-way junctions and supercoiled DNA. The HMG1 A, B and B' domains constrain negative superhelical turns in DNA, but the SRY HMG box does not. Only the full B domain (B') bends DNA in a ligase-mediated circularisation assay; the minimal B box, the A domain and the SRY box do not. Thus, despite a common global fold, the HMG box appears to have been adapted to various functions in different protein contexts.

Pericentric inversion 9--incidence and clinical significance

Pericentric inversion of the chromosome 9, inv(9)(p11q13), is such a common occurrence that some cytogeneticists would consider them as normal variants. The incidence is said to be about 1% to 1.65% in the general population. Despite being categorised as a minor chromosomal rearrangement which does not correlate with abnormal phenotypes, many reports in the literature raised conflicting views regarding the association with subfertility and recurrent abortions, abnormal clinical conditions, as well as chromosomal abnormalities arising as a result of having this inversion. We studied the incidence and clinical significance of inv(9)(p11q13) patients retrospectively from 2448 antenatal cytogenetic analysis and 1058 peripheral blood karyotype collected over a 3-year period. Thirty cases of inv(9)(p11q13) from 29 families were found from the antenatal group, which gave an incidence of 1.2% and 6 cases from the peripheral blood karyotype analysis (incidence of 0.6%). The parental origin of the inv(9)(p11q13) in the antenatal group was of equal proportion and there was also no sex predilection for the fetuses carrying the inversion. The babies with the inversion were born with no phenotypic abnormalities. The 6 cases picked up from the peripheral blood karyotype analysis were 2 cases of paediatric patients with associated chromosomal abnormalities (one Trisomy 21 and the other del 13(q22q32)) and 4 adult patients with obstetric and fertility problems. The incidence of subfertility (36%) appeared to be high amongst the adult patients with inv(9)(p11q13). This may represent a true reflection of subfertility in inv(9)(p11q13) patients or a selective bias towards the older subfertile women who conceive at a later age and thus utilising the antenatal diagnostic setup.

Inborn errors of metabolism in Singapore

Between 1992 and 1994 the Paediatric Metabolic Centre screened 403 patients for inherited metabolic disease. Seventeen patients were diagnosed, including 7 with organic acidurias, 5 with mucopolysaccharidoses, 2 with amino acid disorders, 2 with carbohydrate disorders and 1 with hyperlipidaemia. The ethnic distribution of disorders in Singapore is compared with incidences reported by others in this part of the world. It is likely that further studies will indicate which diagnostic or screening tests would best serve this community.

Cytogenetic abnormalities in childhood acute lymphoblastic leukaemia

A retrospective study of 50 children newly diagnosed with acute lymphoblastic leukaemia (ALL) from December 1988 to November 1993 was carried out, examining the disease conditions and cytogenetic abnormalities. Of the 50 children, 8 had no cytogenetic examination of the marrow at the time of diagnosis and 7 had a poor yield from the marrow. Fifty percent of the remaining children had a normal karyotype. The rest of the children had hyperdiploidy and structural chromosomal abnormalities (mainly translocation and deletions) in equal proportions. Overall mortality of the whole group was about 26% with 2 lost to follow-up. There were 2 patients who relapsed while on treatment of whom 1 died. Cytogenetic abnormalities were correlated with clinical variables known to have prognostic significance. The group with hyperdiploidy had a significantly lower mean total white count at presentation and none of them died. The group with translocation abnormalities had a lower mean platelet count at presentation. Almost all in the group with hyperdiploidy and a great majority of the other 2 groups with normal or structural cytogenetic abnormalities were of B cell lineage. The median survival times for the hyperdiploid, normal karyotype and translocation patients were 1800 days, 1450 days and 700 days respectively.

Epidemiology and control of an outbreak of typhoid in a psychiatric institution

An outbreak of typhoid caused by Salmonella typhi of the same Vi-phage type (D1) and of the same antibiogram was reported in a large psychiatric institution in Singapore. A total of 95 (4.8%) of the 1965 inmates were infected, 47 with symptoms and 48 asymptomatic. Transmission was through close person-to-person contact and not through contaminated food or water. The source of infection could not be established. The outbreak was brought under control by maintaining a high standard of environmental sanitation, active search for fever and diarrhoeal cases, identification of asymptomatic cases by rectal swabbing, and isolation of those found to be infected. Mass immunization with two doses of heat-phenol inactivated typhoid vaccine was also carried out concurrently. The vaccine was found to have an efficacy of 65.8% in preventing clinical illness.

Influence of serum paraoxonase polymorphism on serum lipids and apolipoproteins

One hundred and sixty-three healthy Chinese subjects of both sexes were studied for serum paraoxonase (PON) polymorphism, and levels of lipids and apolipoproteins in order to examine effects of PON alleles on these parameters. The level of serum triglyceride was significantly higher in high activity allele (PON*B) compared with that in low activity allele (PON*A) in both sexes (P less than 0.01). The subjects with PON A had significantly higher LDL cholesterol (P less than 0.05) and lower Apo A-II and ApoB levels. The influence of serum paraoxonase on serum lipids was estimated further by Spearman's rank correlation. In the males, there was a significant negative correlation of serum paraoxonase activity with total (P less than 0.05) and LDL (P less than 0.01) cholesterol levels, and positive correlation with HDL cholesterol and Apo A-II levels (P less than 0.05). Serum paraoxonase activity had a high positive correlation with serum triglyceride levels in both sexes (P less than 0.001). Serum ApoB level had a positive correlation with the enzyme activity only in females (P less than 0.01). The allelic effect of PON on these parameters was studied by multiple regression analysis. The high activity allele (PON*B) was associated with higher serum triglyceride level (P less than 0.001) and ApoB (P less than 0.001), while it had lowering influence on total cholesterol (P less than 0.05) and LDL cholesterol (P less than 0.005) in men. The average allelic effect of PON was found to be about 22% for serum triglycerides, 11% for LDL cholesterol, 14% for Apo A-II and 19% for Apo B in the present study. This study suggests a possible significant role of serum paraoxonase alleles in the metabolism of serum lipids and apolipoproteins.

Person-to-person transmission of cholera in a psychiatric hospital

An outbreak of cholera caused by Vibrio cholerae O1, biotype el tor, serotype Ogawa, phage type 4, was reported in a psychiatric hospital in Singapore. A total of 74 inmates (18 symptomatic and 56 asymptomatic) were infected; two of them died. Extensive epidemiological investigations showed that the organism was not transmitted by contaminated food or water but through close person-to-person contact. Early recognition of the outbreak and prompt implementation of epidemic control measures comprising surveillance of diarrhoea, rectal swabbing of all asymptomatic inmates, isolation of those found to be infected, maintenance of a high standard of environmental sanitation and mass chemoprophylaxis with doxycycline, rapidly brought the outbreak under control.