Mila Ljujic

The integrated stress response

In response to diverse stress stimuli, eukaryotic cells activate a common adaptive pathway, termed the integrated stress response (ISR), to restore cellular homeostasis. The core event in this pathway is the phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α) by one of four members of the eIF2α kinase family, which leads to a decrease in global protein synthesis and the induction of selected genes, including the transcription factor ATF4, that together promote cellular recovery. The gene expression program activated by the ISR optimizes the cellular response to stress and is dependent on the cellular context, as well as on the nature and intensity of the stress stimuli. Although the ISR is primarily a pro‐survival, homeostatic program, exposure to severe stress can drive signaling toward cell death. Here, we review current understanding of the ISR signaling and how it regulates cell fate under diverse types of stress.

Alpha-1-Antitrypsin in Pathogenesis of Hepatocellular Carcinoma

Context Alpha-1-antitrypsin (A1AT) is the most abundant liver-derived, highly polymorphic, glycoprotein in plasma. Hereditary deficiency of alpha-1-antitrypsin in plasma (A1ATD) is a consequence of accumulation of polymers of A1AT mutants in endoplasmic reticulum of hepatocytes and other A1AT-producing cells. One of the clinical manifestations of A1ATD is liver disease in childhood and cirrhosis and/or hepatocellular carcinoma (HCC) in adulthood. Epidemiology and pathophysiology of liver failure in early childhood caused by A1ATD are well known, but the association with hepatocellular carcinoma is not clarified. The aim of this article is to review different aspects of association between A1AT variants and hepatocellular carcinoma, with emphasis on the epidemiology and molecular pathogenesis. The significance of A1AT as a biomarker in the diagnosis of HCC is also discussed. Evidence Acquisitions Search for relevant articles were performed through Pub Med, HighWire, and Science Direct using the keywords “alpha-1-antitrypsin”, “liver diseases”, “hepatocellular carcinoma”, “SERPINA1”. Articles published until 2011 were reviewed. Results Epidemiology studies revealed that severe A1ATD is a significant risk factor for cirrhosis and HCC unrelated to the presence of HBV or HCV infections. However, predisposition to HCC in moderate A1ATD is rare, and probably happens in combination with HBV and/or HCV infections or other unknown risk factors. It is assumed that accumulation of polymers of A1ATD variants in endoplasmic reticulum of hepatocytes leads to damage of hepatocytes by gain-of-function mechanism. Also, increased level of A1AT was recognized as diagnostic and prognostic marker of HCC. Conclusions Clarification of a carcinogenic role for A1ATD and identification of proinflammatory or some still unknown factors that lead to increased susceptibility to HCC associated with A1ATD may contribute to a better understanding of hepatic carcinogenesis and to the development of new drugs.

A common haplotype of protamine 1 and 2 genes is associated with higher sperm counts

Sperm chromatin compaction in the sperm head is achieved when histones are replaced by protamines during spermatogenesis. Haploinsufficiency of the protamine 1 (PRM1) or PRM2 gene causes infertility in mice. However, the published data remain inconclusive about a role of PRM1/2 variants in male infertility and their association with semen parameters. By full sequence analysis, we assessed the frequency of sequence variations in PRM1 and PRM2 in three groups of Caucasian patients with idiopathic teratozoospermia and normal (n = 88) or reduced sperm concentration (n = 83) and in men with a high percentage of normal sperm morphology and normal concentrations (n = 77). Two rare (c.54G>A and c.102G>T) and one common SNP (c.230A>C) were identified in PRM1. In PRM2, some rare heterozygous mutations and the two common intronic SNPs 298G>C and 373C>A were detected. None of the PRM1/2 variants was associated with teratozoospermia or individually with other semen parameters. However, significant linkage disequilibrium was detected between the common SNPs of PRM1 and PRM2 which formed haplotypes. Analysis of the pooled group (n = 248) revealed that homozygous carriers of the common haplotype ACC had a twofold higher sperm concentration and count than men lacking this haplotype, with sperm counts of heterozygotes for ACC being midway between the homozygotes. This markedly decreased sperm output might either be caused by spermatozoa lacking the ACC haplotype not being viable, or subject to negative selection. In addition, a significant deviation from Hardy-Weinberg-Equilibrium of these SNPs might indicate natural selection in favour of the ACC allele which leads to higher sperm output and therefore better fertility. In conclusion, for the first time we describe an association of a common haplotype formed by PRM1 and PRM2 with sperm output in a large group of men.

A1ATVar: a relational database of human SERPINA1 gene variants leading to α1‐antitrypsin deficiency and application of the VariVis software

We have developed a relational database of human SERPINA1 gene mutations, leading to α1‐antitrypsin (AAT) deficiency, called A1ATVar, which can be accessed over the World Wide Web at www.goldenhelix.org/A1ATVar. Extensive information has been extracted from the literature and converted into a searchable database, including genotype information, clinical phenotype, allelic frequencies for the commonest AAT variant alleles, methods of detection, and references. Mutation summaries are automatically displayed and user‐generated queries can be formulated based on fields in the database. A separate module, linked to the FINDbase database for frequencies of inherited disorders allows the user to access allele frequency information for the three most frequent AAT alleles, namely PiM, PiS, and PiZ. The available experimental protocols to detect AAT variant alleles at the protein and DNA levels have been archived in a searchable format. A visualization tool, called VariVis, has been implemented to combine A1ATVar variant information with SERPINA1 sequence and annotation data. A direct data submission tool allows registered users to submit data on novel AAT variant alleles as well as experimental protocols to explore SERPINA1 genetic heterogeneity, via a password‐protected interface. Database access is free of charge and there are no registration requirements for querying the data. The A1ATVar database is the only integrated database on the Internet offering summarized information on AAT allelic variants and could be useful not only for clinical diagnosis and research on AAT deficiency and the SERPINA1 gene, but could also serve as an example for an all‐in‐one solution for locus‐specific database (LSDB) development and curation. Hum Mutat 0,1–6, 2008.

Alpha-1-antitrypsin phenotypes and neutrophil elastase gene promoter polymorphisms in lung cancer.

Imbalance between neutrophil elastase and alpha-1-antitrypsin (AAT) leads to emphysema in smokers as well as in patients with inherited alpha-1-antitrypsin deficiency. AAT as a proven inhibitor of apoptosis may play role in lung cancer (LC) progression. The aim was to analyse AAT protein variants and polymorphism in promoter region of the neutrophil elastase gene (ELA2) in patients with primary lung cancer. AAT phenotypisation by isoelectric focusing method and ELA2 gene promoter characterization by DNA sequencing were performed in 66 patients with primary lung cancer. Results showed that the frequency of M1 allele and PiM1 homozygotes in LC patients was significantly higher when compared to the healthy subjects (f = 0.6360 and 0.7424 respectively). The most frequent ELA2 promoter region genotypes in LC patients were −903TT and −741GG. There were significantly more patients with intermediate and high ELA2 genotype activity, compared to those with low activity (91% vs. 9%, respectively). In conclusion, we found that PiM1 homozygosity could be associated with the lung cancer, probably due to increased synthesis of this antiapoptotic protein. Non-MM variants of AAT and ELA2 genotypes with predicted intermediate or high activity could also represent a risk factor for aggressive form of lung cancer associated with extrathoracic metastases.

Isoelectric focusing phenotyping and denaturing gradient gel electrophoresis genotyping: a comparison of two methods in detection of alpha-1-antitrypsin variants

Laboratory diagnosis of alpha-1-antitrypsin (AAT) deficiency is routinely performed by phenotyping methods, which include measurement of serum alpha-1-antitrypsin concentration and isoelectric focusing (IEF). Several DNA-based methods are also used for AAT deficiency testing, but they still have not become part of routine diagnostics. The aim of the study was to identify AAT variants using 2 different methods, isoelectric focusing and denaturing gradient gel electrophoresis (DGGE), and to compare obtained results as well as practical application of these 2 methods. The study has encompassed 27 emphysema patients. In all patients, AAT phenotypization was conducted using IEF, whereas genotypization was performed by DGGE. Variations detected by DGGE were characterized by DNA sequencing. Mutations in the AAT gene were detected in 6 patients. Three patients were homozygous for the Z allele, whereas 1 patient was heterozygous. In 2 patients, novel AAT variants, G320R and V321F, were detected. When results obtained by IEF and DGGE were compared, it was observed that IEF results were inconclusive or misinterpreted in 5 cases (18.5%). Both methods proved to be reliable for detection of the Z alleles, whereas discrepancy existed for M4 allele and rare variants. Therefore, the optimal strategy for diagnostics of AAT deficiency should encompass detection of the most common AAT variants by IEF and screening for the less common variants by DGGE in combination with sequencing.

Identification of a rare p.G320R alpha-1-antitrypsin variant in emphysema and lung cancer patients

The alpha-1-antitrypsin (A1AT) gene is highly polymorphic, with more than 100 genetic variants identified of which some can affect A1AT protein concentration and/or function and lead to pulmonary and/or liver disease. This study reports on the characterization of a p.G320R variant found in two patients, one with emphysema and the other with lung cancer. This variant results from a single base-pair substitution in exon 4 of the A1AT gene, and has been characterized as P by isoelectric focusing. Functional evaluation of the A1AT p.G320R variant was through comparing specific trypsin inhibitory activity in two patients with pulmonary disorders, carriers of the p.G320R variant, and 19 healthy individuals, carriers of normal A1AT M variants. Results showed that specific trypsin inhibitory activity was lower in both emphysema (2.45 mU/g) and lung cancer (2.07 mU/g) patients than in carriers of the normal variants (range 2.51-3.71 mU/g). This rare A1AT variant is associated with reduced functional activity of A1AT protein. Considering that it was found in patients with severe pulmonary disorders, this variant could be of clinical significance.

Is an integrative laboratory algorithm more effective in detecting alpha-1-antitrypsin deficiency in patients with premature chronic obstructive pulmonary disease than AAT concentration based screening approach?

Introduction: Alpha-1-antitrypsin deficiency (AATD), genetic risk factor for premature chronic obstructive pulmonary disease (COPD), often remains undetected. The aim of our study was to analyse the effectiveness of an integrative laboratory algorithm for AATD detection in patients diagnosed with COPD by the age of 45 years, in comparison with the screening approach based on AAT concentration measurement alone. Subjects and methods: 50 unrelated patients (28 males/22 females, age 52 (24–75 years) diagnosed with COPD before the age of 45 years were enrolled. Immunonephelometric assay for alpha-1-antitrypsin (AAT) and PCR-reverse hybridization for Z and S allele were first-line, and isoelectric focusing and DNA sequencing (ABI Prism BigDye) were reflex tests. Results: AATD associated genotypes were detected in 7 patients (5 ZZ, 1 ZMmalton, 1 ZQ0amersfoort), 10 were heterozygous carriers (8 MZ and 2 MS genotypes) and 33 were without AATD (MM genotype). Carriers and patients without AATD had comparable AAT concentrations (P = 0.125). In majority of participants (48) first line tests were sufficient to analyze AATD presence. In two remaining cases reflex tests identified rare alleles, Mmalton and Q0amersfoort, the later one being reported for the first time in Serbian population. Detection rate did not differ between algorithm and screening both for AATD (P = 0.500) and carriers (P = 0.063). Conclusion: There is a high prevalence of AATD affected subjects and carriers in a group of patients with premature COPD. The use of integrative laboratory algorithm does not improve the effectiveness of AATD detection in comparison with the screening based on AAT concentration alone.

Targeting autophagy to modulate cell survival: a comparative analysis in cancer, normal and embryonic cells

AbstractAutophagy is linked to multiple cancer-related signaling pathways, and represents a defense mechanism for cancer cells under therapeutic stress. The crosstalk between apoptosis and autophagy is essential for both tumorigenesis and embryonic development. We studied the influence of autophagy on cell survival in pro-apoptotic conditions induced by anticancer drugs in three model systems: human cancer cells (NCI-H460, COR-L23 and U87), human normal cells (HaCaT and MRC-5) and zebrafish embryos (Danio rerio). Autophagy induction with AZD2014 and tamoxifen antagonized the pro-apoptotic effect of chemotherapeutics doxorubicin and cisplatin in cell lines, while autophagy inhibition by wortmannin and chloroquine synergized the action of both anticancer agents. This effect was further verified by assessing cleaved caspase-3 and PARP-1 levels. Autophagy inhibitors significantly increased both apoptotic markers when applied in combination with doxorubicin while autophagy inducers had the opposite effect. In a similar manner, autophagy induction in zebrafish embryos prevented cisplatin-induced apoptosis in the tail region while autophagy inhibition increased cell death in the tail and retina of cisplatin-treated animals. Autophagy modulation with direct inhibitors of the PI3kinase/Akt/mTOR pathway (AZD2014 and wortmannin) triggered the cellular response to anticancer drugs more effectively in NCI-H460 and zebrafish embryonic models compared to HaCaT suggesting that these modulators are selective towards rapidly proliferating cells. Therefore, evaluating the autophagic properties of chemotherapeutics could help determine more accurately the fate of different cell types under treatment. Our study underlines the importance of testing autophagic activity of potential anticancer agents in a comparative approach to develop more rational anticancer therapeutic strategies.

ALPHA-1 antitrypsin affects U0126-induced cytotoxicity in colon cancer cell line (HCT116)

Alpha-1-antitrypsin (AAT), an acute phase protein, is the principal circulatory anti-protease. This multifunctional protein is encoded by the SERPINA1 gene. Although AAT was recognised as a potential tumour marker, its role in cancer biology remains unknown. Given that it has been demonstrated that AAT has an anti-apoptotic property against non-malignant cells, we aimed to investigate whether AAT affects apoptosis in a colon cancer cell line (HCT116). The presence of AAT in the HCT116 cell culture antagonized cytotoxicity of blockers of MEK1/2, PI3K/Akt pathways as well as NF-κB. The dominantly recovered cell viability was observed in the co-treatment with MEK1/2 inhibitor U0126. In addition, it was revealed that AAT almost completely abolished U0126-induced apoptosis through maintenance of the autophagy process. Our study revealed for the first time that the observed cyto-protection triggered by AAT was accompanied by sustained autophagy which opposed apoptosis. These results may contribute to understanding of the role of AAT in cancer development and evaluation of efficacy of cancer therapy.