Azhar bin Ali

Expression of major HDL-associated antioxidant PON-1 is gender dependent and regulated during inflammation.

Paraoxonase 1, an HDL-associated enzyme that confers antioxidant activity on HDL, and its activity in serum have been correlated with protection against atherosclerosis, an oxidative disease. However, serum PON-1 activity is highly variable and its regulation is complex, involving both genetic and environmental factors. It is influenced by gender and inflammation, two important factors in atherosclerosis. Serum PON-1 activity has been shown to be lower in male mice and is decreased in male Syrian hamster during inflammation. Here we show that male mice had lower hepatic PON-1 mRNA that increased by 170% after castration. Our data also suggested that this effect was testes but not plasma testosterone dependent. Ovariectomy had no effect on PON-1 mRNA in female mice. LPS caused hepatic PON-1 mRNA to decrease further in male mice, and to increase moderately in female mice. Anti-inflammatory dexamethasone enhanced PON-1 mRNA level by 2-fold in male and female LPS-treated mice, and increased PON-1 expression by 8-fold in Hepa cell, a mouse hepatoma cell line. Therefore, antioxidant PON-1 is regulated at the mRNA level in a gender-specific manner by proinflammatory LPS and anti-inflammatory dexamethasone.

Identification of novel BRCA large genomic rearrangements in Singapore Asian breast and ovarian patients with cancer.

Large genomic rearrangements have been reported to account for about 10–15% of BRCA1 gene mutations. Approximately, 90 BRCA rearrangements have been described to date, all of which but one have been reported in Caucasian populations of predominantly Western European descent. Knowledge of BRCA genomic rearrangements in Asian populations is still largely unknown. In this study, we have investigated for the presence of BRCA rearrangements among Asian patients with early onset or familial history of breast or ovarian cancer. Using multiplex ligation‐dependent probe amplification (MLPA), we have analyzed 100 Singapore patients who previously tested negative for deleterious BRCA mutations by the conventional polymerase chain reaction‐based mutation detection methods. Three novel BRCA rearrangements were detected, two of which were characterized. The patients with the rearrangements, a BRCA1 exon 13 duplication, a BRCA1 exon 13–15 deletion and a BRCA2 exon 4–11 duplication, comprise 3% of those previously tested negative for BRCA mutations. Of the BRCA1 and BRCA2 pathogenic mutations identified in our studies on Asian high‐risk breast and ovarian patients with cancer to date, these rearrangements constitute 2/19 and 1/2 of the BRCA1 and BRCA2 pathogenic mutations, respectively. Given the increasing number of rearrangements reported in recent years and their contribution to the BRCA mutation spectrum, the presence of BRCA large exon rearrangements in Asian populations should be investigated where clinical, diagnostic service is recommended.

Gonadal effects on plasma ACE activity in mice

Angiotensin-converting enzyme (ACE) regulates blood pressure and is an important target in the management of hypertension. Hypertension is a gender biased disease. Plasma ACE activity is significantly higher in male mice (309 U/l) than female mice (237 U/l) and is reduced significantly upon gonadectomy to 224 and 209 U/l, respectively. Although, the gonads influence plasma ACE activity in both male and female mice, the effect is more pronounced in male mice. Plasma ACE is derived from the cleavage of tissue ACE and lung has the highest concentration of tissue ACE. However, lung ACE activity is not gender dimorphic but increases significantly upon gonadectomy in both male and female. ACE mRNA level in the lung is not influenced by gender or gondaectomy. Therefore, the gonads affect plasma ACE activity by influencing cleavage of tissue ACE to plasma ACE and/or decrease stability of plasma ACE in gonadectomized mice is mediated.

Hepatic expression of PPARα, a molecular target of fibrates, is regulated during inflammation in a gender‐specific manner

Dyslipidemia, inflammation and gender are major risk factors in cardiovascular disease. Here we show that hepatic expression of Peroxisome proliferator‐activated receptor α (PPARα), a nuclear receptor that regulates lipid metabolism and inflammation, is regulated in a gender‐specific manner during lipopolysaccharide (LPS)‐induced systemic inflammation. Immediately following LPS‐induced systemic inflammation, hepatic PPARα mRNA level decreased dramatically in mice. It was restored to baseline within 24 h in females but remained below baseline for >72 h in male mice. In gonadectomized mice of both sexes, PPARα mRNA level was restored to baseline within 48 h after the initial decrease.

Role of Chaperone Mediated Autophagy (CMA) in the Degradation of Misfolded N-CoR Protein in Non-Small Cell Lung Cancer (NSCLC) Cells

Nuclear receptor co-repressor (N-CoR) plays important role in transcriptional control mediated by several tumor suppressor proteins. Recently, we reported a role of misfolded-conformation dependent loss (MCDL) of N-CoR in the activation of oncogenic survival pathway in acute promyelocytic leukemia (APL). Since N-CoR plays important role in cellular homeostasis in various tissues, therefore, we hypothesized that an APL like MCDL of N-CoR might also be involved in other malignancy. Indeed, our initial screening of N-CoR status in various leukemia and solid tumor cells revealed an APL like MCDL of N-CoR in primary and secondary tumor cells derived from non-small cell lung cancer (NSCLC). The NSCLC cell specific N-CoR loss could be blocked by Kaletra, a clinical grade protease inhibitor and by genistein, an inhibitor of N-CoR misfolding previously characterized by us. The misfolded N-CoR presented in NSCLC cells was linked to the amplification of ER stress and was subjected to degradation by NSCLC cell specific aberrant protease activity. In NSCLC cells, misfolded N-CoR was found to be associated with Hsc70, a molecular chaperone involved in chaperone mediated autophagy (CMA). Genetic and chemical inhibition of Lamp2A, a rate limiting factor of CMA, significantly blocked the loss of N-CoR in NSCLC cells, suggesting a crucial role of CMA in N-CoR degradation. These findings identify an important role of CMA-induced degradation of misfolded N-CoR in the neutralization of ER stress and suggest a possible role of misfolded N-CoR protein in the activation of oncogenic survival pathway in NSCLC cells.

Are medullary breast cancers an indication for BRCA1 mutation screening? A mutation analysis of 42 cases of medullary breast cancer.

Recommended guidelines have limited breast cancer gene (BRCA1) mutation testing to individuals with a personal or family history of early onset breast and/or ovarian cancer, and those with multiple affected close relatives. Such large breast cancer families are rare in the general population, limiting the clinical application of the BRCA1 discovery. Previous reports have suggested an association between medullary breast cancer and BRCA1 mutation carriers. To test the feasibility of using these rare histological subtypes as an alternative to epidemiological factors, 42 cases of medullary cancer unselected for family history were screened for BRCA1 point mutations and large exon rearrangements. The large majority (83%) of these patients did not have significant family of breast or ovarian cancer. Two deleterious mutations resulting in a premature stop codon, and one exon 13 duplication were found. All mutations were detected in patients with typical medullary cancer, who had family history of multiple breast and ovarian cancers. Our findings suggest that medullary breast cancers are not an indication for BRCA1 mutation screening in the absence of significant family risk factors.

BRCA1 c.2845insA is a recurring mutation with a founder effect in Singapore Malay women with early onset breast/ovarian cancer

Breast cancer is the third most common form of cancer worldwide, after lung and stomach cancer, and is the most common cause of cancer death in women.1 The age-adjusted incidence rates of breast cancer are 176% higher in developed than developing countries.2 In Singapore, breast cancer is the most common cancer in women and the incidence rate in 1993–1997 was 2.3 times higher than in 1968–1972, with an annual increase significantly higher in pre-menopausal than post-menopausal women (5.7% v 3.9%).3,4 Of note, the Malay ethnic group in Singapore has shown the greatest increase in the incidence of breast cancer (4.4%) over the past three decades compared with the Chinese and Indian subpopulations. In addition, breast cancer in Malay women has shown a bimodal distribution in age specific incidence, at 45 and 65 years, and a strong birth cohort effect has been noticed in this group. The majority of breast cancer is sporadic, but about 5% to 10% of all breast and ovarian cancer cases are believed to be attributable to the inheritance of germline mutations in high penetrance, autosomal dominant susceptibility genes.5–7 The identification and cloning of one such gene BRCA1 (OMIM # 113705)8,9 has rapidly led to the characterisation of mutations in this gene among high risk families, as well as early onset breast and/or ovarian cancer patients or tumour series in populations worldwide.10–14 Several founder and recurrent mutations have now been identified in specific ethnic groups, such as African-Americans, Ashkenazi Jews, Dutch, Finns, French-Canadians, Icelanders, Japanese, Norwegians, Swedes, and Russians, among others.15–17 However, almost all molecular studies of BRCA1 performed have defined breast cancer risks and related genetic factors in Caucasian women of European descent, and studies in Asian populations, although on the increase, have been …

Synthesis and Evaluation of Bisbenzylidenedioxotetrahydrothiopranones as Activators of Endoplasmic Reticulum (ER) Stress Signaling Pathways and Apoptotic Cell Death in Acute Promyelocytic Leukemic Cells

Curcumin is known to trigger ER-stress induced cell death of acute promyelocytic leukemic (APL) cells by intercepting the degradation of nuclear co-repressor (N-CoR) protein which has a key role in the pathogenesis of APL. Replacing the heptadienedione moiety of curcumin with a monocarbonyl cross-conjugated dienone embedded in a tetrahydrothiopyranone dioxide ring resulted in thiopyranone dioxides that were more resilient to hydrolysis and had greater growth inhibitory activities than curcumin on APL cells. Several members intercepted the degradation of misfolded N-CoR and triggered the signaling cascade in the unfolded protein response (UPR) which led to apoptotic cell death. Microarray analysis showed that genes involved in protein processing pathways that were germane to the activation of the UPR were preferentially up-regulated in treated APL cells, supporting the notion that the UPR was a consequential mechanistic pathway affected by thiopyranone dioxides. The Michael acceptor reactivity of the scaffold may have a role in exacerbating ER stress in APL cells.

1.5 MeV proton irradiation effects on electrical and structural properties of TiO2/n-Si interface

In this paper, we report the effect of 1.5 MeV proton beam irradiation dose on the structural and electrical properties of TiO2 thin films deposited on n–Si substrates. The formation and transformation of different TiO2 phases in the irradiated thin films were characterized by X-ray diffraction and X-ray photoelectron spectroscopy (XPS). X-ray diffraction measurements revealed that the as grown film was rich in Ti5O9 phase and then converted to mixed phases of TiO2 (rutile and anatase) after exposure with radiation doses up to 5 × 1014 cm−2. The XPS results revealed the formation of oxygen vacancy (negative) traps in the exposed TiO2 films, which showed strong dependence on the dose. The C-V measurements showed that proton radiations also damaged the Si substrate and created deep level defects in the substrate, which caused a shift of 0.26 ± 0.01 V in the flat band voltage (VFB). I–V measurements showed that the ideality factor increased and the rectification ratio dropped with the increase in the radiati...

Cancer-specific methylation in the BRCA1 promoter in sporadic breast tumours

To the EditorSilencing of the BRCA1 gene via promoter hyperme-thylation has been proposed as one mechanism for itsinactivation and found to occur in 10–31% of all sporadicbreast tumours [1, 2]. The impact of promoter hyperme-thylation on the BRCA1 gene is similar to that of a germ-line BRCA1 mutation in terms of gene expression patterns[3, 4]. Breast cancer tumours, with extensive hyperme-thylation in the BRCA1 promoter, have consistently beencorrelated with reduced BRCA1 expression [2, 5].Previous studies have shown a region of 267 bp (-224to ?43; GenBank for BRCA1, U37574) within the BRCA1promoter to be functionally important for its optimaltranscriptional regulation. In particular, deletion of a 222bp (-220 to ?20) fragment within this region, termed thepositive regulatory region (PRR), has been shown to resultin complete loss of the BRCA1 promoter activity [6, 7].Alterations by DNA methylation are thought to be animportant event in tumour initiation; hence, the identifi-cation of tumour-specific methylation patterns in BRCA1promoter may serve as targets for breast cancer detection.The aim of this study was to investigate the presence ofcancer-specific methylation within the PRR of BRCA1 insporadic breast tumours. Histologically proven archivalmatched breast cancer tissues, as well as normal breasttissues from the affected breast, from 23 sporadic breastcancer cases were selected, and their use had the approvalof the institutional ethical committee, National UniversitySingapore-Institutional Review Board (NUS-IRB). Mat-ched tumour and corresponding normal tissues of the samepatient were used to compensate for any age-relatedmethylation [8, 9].BRCA1 promoter hypermethylation was detected in34.8% (8/23) of Asian sporadic breast tumours using MS-PCR-based method (Fig. 1a, b). MS-PCR was carried outat least twice for all samples to confirm the percentage ofcases with BRCA1 promoter hypermethylation. Differencein BRCA1 methylation levels between each matchedtumour and normal tissue was initially determined by cal-culating the mean, standard deviation and 95% CI of the 23matched samples. Tumour samples with difference inBRCA1 methylation levels greater than the upper value of95% CI were considered to be hypermethylated. In addi-tion, methylation in the BRCA1 promoter was alsoobserved in normal breast tissues from breast cancerpatients, an observation similarly reported in a previousstudy [10].Our data also showed that breast tumours with BRCA1hypermethylation exhibited a significant loss of BRCA1transcripts (Fig. 1c). BRCA1 hypermethylated tumourswere then screened for BRCA1 mutation where the entirecoding sequence, including splice junctions and neigh-bouring intronic regions of BRCA1 were analysed usingpreviously described methods [11]. This was carried out toexclude somatic mutation as the cause for loss of BRCA1expression in these samples. No mutations were found thussuggesting BRCA1 transcriptional silencing by promoterhypermethylation in these tumours. MS-PCR products