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The role of polymorphisms in segregation genes in cancer

Research activity

Code Science Field Subfield
3.04.00  Medical sciences  Oncology   

Code Science Field
B007  Biomedical sciences  Medicine (human and vertebrates) 

Code Science Field
3.02  Medical and Health Sciences  Clinical medicine 
Keywords
gastric cancer, adenocarcinom, chromosomal instability, aneuploidy, mitotic seggregation genes, genetic polymorphisms, SNP, GWAS, AURKA, ZW10, ZWINT, TPX2, BUB1B, functional analysis, genetic variants, yeast test system
Evaluation (rules)
source: COBISS
Researchers (11)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  16104  PhD Apolonija Bedina Zavec  Biotechnology  Researcher  2013 - 2016  154 
2.  18622  PhD Nataša Debeljak  Biochemistry and molecular biology  Researcher  2013 - 2016  249 
3.  21395  PhD Petra Hudler  Medical sciences  Researcher  2013 - 2016  156 
4.  29388  PhD Nina Kočevar Britovšek  Natural sciences and mathematics  Researcher  2013  37 
5.  06135  PhD Radovan Komel  Biochemistry and molecular biology  Head  2013 - 2016  1,054 
6.  14305  PhD Mirjana Liović  Metabolic and hormonal disorders  Researcher  2013 - 2016  148 
7.  10614  PhD Mirko Omejc  Oncology  Researcher  2013 - 2016  259 
8.  34353  PhD Marija Rogar  Biochemistry and molecular biology  Junior researcher  2013 - 2016  25 
9.  06013  PhD Damjana Rozman  Biochemistry and molecular biology  Researcher  2013 - 2016  896 
10.  33735  PhD Neja Šamec  Biochemistry and molecular biology  Technical associate  2013 - 2015  82 
11.  33509  Tina Zupančič  Biotechnology  Technical associate  2013 - 2014  25 
Organisations (3)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0104  National Institute of Chemistry  Ljubljana  5051592000  21,237 
2.  0312  University Medical Centre Ljubljana  Ljubljana  5057272000  77,904 
3.  0381  University of Ljubljana, Faculty of Medicine  Ljubljana  1627066  48,704 
Abstract
During the last few decades, studies of gastric cancer (GC) have shown that it results from a series of complex gene-environment interactions. New high-throughput techniques have revealed its heterogeneous nature with alterations to many genes, deregulation of signalling pathways, aberrant DNA methylation patterns, and chromosomal imbalances. Nevertheless, there is still no clear agreement on the molecular changes underlying the initiation and progression of adenocarcinoma. Furthermore, it is evident that DNA polymorphisms along with the functionality of an individual’s immune system and a variety of environmental factors contribute to the disease. In addition, the biological characteristics of gastric tumours vary from case to case, and tumours from one individual are comprised of malignant cells showing different characteristics, growth preferences, and gene expression profiles. A body of research evidence supports the hypothesis that chromosomal instability (CIN) and aneuploidy are probably early events implicated in the initiation and development of epithelial cancers. The consequence of CIN and aneuploidy is slow accumulation of chromosomal aberrations in replicating epithelial cells, leading to inactivation of tumour suppressors, activation of oncogenes, and inducing changes in genes implicated in controlling normal cellular homeostasis, thus promoting malignant transformation. It was suggested that telomerase activation, impairment of DNA damage repair systems, and mutations in cell cycle checkpoint genes could lead to genome instability. However, recent studies revealed that subtle changes in mitotic segregation genes, controlling chromatids separation, are prime candidates for inducing the slow process of accumulation of genetic changes, leading to CIN. This new hypothesis is further supported by the fact that this process is, as mentioned, slow, and explains the late onset of sporadic epithelial cancers. On the other hand, pathogenic mutations in oncogenes and tumour suppressors are usually more aggressive and induce the development of disease in younger patients. The goal of the proposed application is identification and characterization of polymorphisms in mitotic segregation genes in patients with GC. We will develop a method for the determination of aneuploidy in frozen gastric tissues using flow cytometry. Any polymorphisms which show association with GC, will be functionally characterized in the yeast system, where we will look into the effect of polymorphisms introduced into homologous yeast genes on genome stability. We will also analyse these polymorphic variants in primary and immortalised cultures of mammalian epithelial cell lines, analysing their expression patterns and effects upon cell cycle arrest and integrity of the centrosome cycle. Furthermore, promoter polymorphisms will be functionally characterized using promoter assays, while the effect of coding polymorphisms on protein structure will be envisaged with in silico modelling. With these studies we will identify specific gene polymorphisms associated with elevated GC risk in the Slovenian population. The results will be useful for the development of early diagnostic tests, based on new biomarkers for predicting tumour initiation and progression, and for selecting the most appropriate targets for possible new therapeutic approaches. New methods of high-throughput genotyping with a proven applicability in defining a large number of genomic alterations, will in future be useful also in research into the genetic background of other diseases. Currently, there is a lack of information on the functional effects of polymorphisms in heterologous and homologous systems; therefore we believe that investigation of new methods for the exploration of functional effects of polymorphisms at the protein and functional level in yeast and epithelial cells will contribute to a better understanding of the molecular mechanisms of GC initiation and development.
Significance for science
Gastric cancer is a complex and heterogeneous disease, and although much has been learned about the different genetic changes that eventually lead to its development, the detailed mechanisms still remain unclear. After decades of research it is now believed that malignant transformation of gastric cells is the consequence of a multistep process involving different genetic and epigenetic changes in numerous genes in combination with the host genetic background and environmental factors. Recent experimental evidence in several types of solid cancers including gastric adenocarcinoma supports the hypothesis that chromosomal instability (CIN) is probably an early event implicated in the initiation and development of epithelial cancers. Recent studies revealed that subtle changes in mitotic segregation genes, controlling chromatids separation, are the most probable candidates for inducing the slow process of accumulation of genetic changes, leading to CIN. Molecular mechanisms underlying CIN are cellular processes involved in the regulation of mitotic spindle checkpoints genes that control kinetochore structure and function, centrosome and microtubule formation, chromosome condensation, sister chromatid cohesion and cell cycle checkpoints. However, mutations in these genes are rare, while naturally occurring genetic variations known as SNPs are common and appear with variable frequency within different ethnic groups. Particular SNPs can alter the gene expression profile and affect gene function, which may result in increased risk of susceptibility to different diseases, including cancer. Single nucleotide polymorphisms (SNPs) in mitotic genes could affect the chromosome duplication and segregation in a subtle way, so that the changes would not trigger repair mechanisms and/or cell death. In this respect slow accumulation of chromosomal aberrations could eventually lead to stepwise malignant transformation of cells via inactivation of tumour suppressors, activation of oncogenes, and inducing changes in genes, implicated in normal homeostasis of cells. In the context of the research project we verified the hypothesis that polymorphisms in genes involved in the regulation of the formation of the mitotic spindle and in the process of segregation of chromosomes can affect the risk of developing gastric cancer. Our results showed significant associations of certain genetic variants of AURKA, AURKB, AURKC, BUB1R, CASC5, PTTG1 and ZWINT genes with an increased risk for the development of the disease. In addition, certain SNPs were more frequently observed in association with particular histopathological features, including intestinal or diffuse types of gastric cancer or well-differentiated or undifferentiated morphology. The research results support the hypothesis of CIN as early cause for the occurrence and development of gastric cancer, and may contribute to a better understanding of its pathogenesis and the development of early diagnostic procedures.
Significance for the country
Gastric cancer is the fourth most common (7.6% of all cancers) and the second leading cause of cancer deaths worldwide (9.6% of all cancer deaths). In Slovenia according to the incidence and by the cause of death it takes the sixth place and accounts for 7% of cancers in men and 4% of cancers in women. The disease begins after age 40 with a peak between 60 and 80 years. Signs of the disease are unspecific and occur relatively late, when the disease is already widespread and almost 50% of patients are not suitable for surgery. Early detection of gastric cancer and improved diagnostic procedures in that respect may affect the improvement in overall survival and quality of life of patients after removal of the first stomach neoplasia. Our findings could lead to better diagnosis, as the detection and confirmation of several genetic markers that show correlation with the risk of gastric cancer and. even for a specific form of the disease, allow completion of a set of a screening markers for determining the risk of developing gastric cancer. Certain polymorphisms could also be used as prognostic markers. By identifying the presence of patient specific polymorphic genotypes, which are associated with different cliniopathological features, medical doctors could choose tighter regime of chemotherapy in patients with gastric cancer. As an example, we highlight polymorphism rs17747633, for which we have shown that patients with AA genotype are more likely to express tumors at the gastroesophageal-border. This type of cancer is on the rise in Europe, and it is significantly associated with worse survival. Identification of prognostic polymorphic biomarkers could thus have an impact on improving patient survival through optimized therapeutic approaches. The project also harboured an important educational component in the field of molecular oncology, allowing the implementation of two doctoral theses, one graduation thesis and three student research tasks. In this respect, it also contributed to establishing the appropriate expertise at the Medical Faculty of the University of Sarajevo, Bosnia and Herzegovina, and thus opening better prospects for eventual international cooperation in the future.
Most important scientific results Annual report 2013, 2014, 2015, final report
Most important socioeconomically and culturally relevant results Annual report 2013, 2014, 2015, final report
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