DEPARTMENT OF MOLECULAR BIOLOGY OF CANCER

Pavel Vodička, MD., PhD.
e-mail: pvodicka@biomed.cas.cz
tel: +420241062694

Laboratory of DNA Repair

Head: Pavel Vodička, MD., PhD.
e-mail: pvodicka@biomed.cas.cz
tel: +420241062694

Laboratory of Genetics of Cancer

Head: Alessio Naccarati, PhD.
e-mail: naccarati@biomed.cas.cz
tel: +420241062694

Scientists:

MUDr. Ľudmila Vodičková, CSc.
RNDr. Alessio Naccarati, PhD.

Ph.D. Students:

Ing. Veronika Poláková
Mgr. Monika Hánová
Mgr. Jana Slyšková
Mgr. Jiří Chadt
Mgr. Elena Tulupova
Mgr. Barbara Pardini
Mgr. Miroslava Kuricová

The molecular events involved in the mechanisms of DNA repair

DNA repair processes play a key role in the removal of DNA damage, thus preventing mutagenicity and/or carcinogenicity. Our effort has been aimed at understanding the DNA repair processes of the damage induced by various xenobiotics in cell cultures and experimental animals. Apparently, DNA repair seems to remove DNA damage induced by simple alkyl epoxides by different mechanisms (base excision repair,BER: short-patch repair) in comparison to methylating agents (BER: long-patch repair) and polycyclic aromatic hydrocarbons (nucleotide excision repair, NER). The mechanisms of DNA repair of the damage induced by styrene and 1,3-butadiene are currently studied on human xeroderma pigmentosum cell lines (XPA and XPC cells) with deficient NER. Increasing number of studies relating genetic polymorphisms in DNA repair genes and various kinds of cancer in the past 5 years do not provide unambiguous consistent associations. Most importantly, the relationship between the DNA repair genotype and the functional outcome (phenotype) is virtually unknown. We investigate associations between polymorphisms in DNA repair genes and the capacity to repair DNA damage induced by γ-irradiation and by base oxidation in healthy population. BER rates seem to decrease with XRCC1 Arg399Gln homozygous variant genotype. Similarly, the capacity to repair oxidative DNA damage appears to be significantly decreased among individuals with hOGG1 Ser326Cys homozygous variant genotype. Our recent effort is aimed at the development of the functional test for the determination of NER rates in humans.
General research in the Laboratory of DNA Repair focuses on the following topics:

• Investigation of mechanisms in DNA repair pathways
• Functional tests for DNA repair capacity
• Expression of relevant DNA repair candidate genes
• Interest in phenotype-genotype interactions

Interindividual variations in DNA repair genes may confer altered DNA repair capacity, and thus an enhanced cancer risk. The polymorphisms of different DNA repair genes, mainly single-nucleotide polymorphisms, modulate the individual repair capacity in response to DNA damage.

Research on fundamental molecular mechanisms of cancer

Laboratory of Genetics of Cancer is focused on the fundamental molecular mechanisms involved in the cascade of genotoxic/carcinogenic events in relation to exposure to xenobiotics, as well as on the factors of individual susceptibility modulating genotoxic and/or carcinogenic effects. Our interest is devoted to the investigations of the role of low-penetrance genes for the onset of sporadic cancers, colorectal cancer in particular. Additionally, interplay of low- and high penetrance genes in cancer development is studied.

General research in the Laboratory of Genetics of Cancer focuses on the following topics:

• Determination of various biomarkers defined as indicators of effect and individual susceptibility to various xenobiotics
• Investigation of genetic polymorphisms in DNA repair, cell cycle and XME genes
• Detection of DNA and chromosomal damage
• DNA adducts as biomarkers of genotoxicity
• Identification of relevant candidate genes affecting chromosomal and genomic instability
• The determination of the role of low-penetrance genes (cell cycle, DNA repair) for the onset of sporadic colorectal cancer and other types of cancer

Studies on both genetic and environmental/life style factors and their interactions may contribute to our understanding the onset of sporadic cancers and set up pilot information on the individualized therapeutical pattern.

Fig. 1: A simplified schema of the most important DNA repair pathways

zoom figure

The genome is continuously assaulted by reactive species within cells (reactive oxygen species and various metabolites) and by environmental agents from without (UV light, ionizing radation, and toxins). It is not surprising, therefore, that the human genome encodes a large number of proteins, at least 130, that function in DNA repair processes. Several types of DNA repair processes are tailored to deal with various type of damage, although some are overlaping. For example, three types of excision repair have been described: base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). Two additional types of DNA repair, homologous recombination (HR) and nonhomologous end-joining (NHEJ), are employd when the most serious type of DNA damage, a doublestrand break, occurs.

Fig. 2: Events involved in the cascade of genotoxic effects following exposure to xenobiotics.

zoom figure

Numerous environmental and/or occupational xenobiotics to which humans are exposed cause various adverse effects (general toxicity, disturbances in the immune system) and may tend to accumulate in the body if the enzymatic metabolizing system is less efficient. On the other hand, metabolic conversion may result in the formation of highly reactive intermediates, which are usually responsible for genotoxic effects due to a direct attack on the nucleophillic centers of biological macromolecules. As stated above, the pivotal role in preserving genomic integrity is being played by DNA repair processes, responsible for the removal of arising DNA damage, thus preventing mutagenicity and/or carcinogenicity.

Fig. 3: The tentative role of individual genetic susceptibility along with external/internal environmental factors in sporadic CRC risk.

zoom figure

Colorectal cancer (CRC) is a common neoplasia in both men and women with the estimated risk worldwide of 5% and ranks as the fourth most common cancer in the world with approximately 875000 new cases diagnosed each year. An increased incidence in Europe has been recorded over the past decade, with a severity of situation in central European region. The incidence of CRC in the Czech Republic ranks third worldwide, while the incidence of rectal cancer, particularly in men, is the highest. In CRC, the predominant form is the sporadic one (approx. 80% of all cases). For the onset of CRC both environmental and genetic factors are involved. It is believed that sporadic CRC is likely to involve multiple genes with moderate effects (low penetrance type) and progress materializes due to aggressive gene-environment interactions. The complex etiology of CRC and observed high incidence in Czech Republic stresses an importance of a systematic approach by combining epidemiological and molecular biological methods to understand critical pathways (Fig. 3) in CRC tumorigenesis. Our approach consists of two distint parts: A) Molecular epidemiology on white blood cell DNA samples from CRC patients, aimed at exploring associations between genetic polymorphisms in DNA repair and cell cycle genes and CRC, including haplotypes, on a cohort of more than 800 cases and 700 controls from the Czech Republic (sample collection still continues). B) Molecular genetic part, performed on tissues from colon polyposis, will be focused on the determination of molecular markers in high penetrance genes (MMR, tumour suppressor genes and oncogenes) relevant in colorectal carcinogenesis. The availability of tissue samples from colon polyposis offers an excellent opportunity to address expressions of the relevant genes (based on mRNA-cDNA approach).

Name of the grant	Agency	Number of the grant	Coordinator	Duration of the grant
Dietary exposures to polycyclic aromatic hydrocarbons and DNA Damage	Directorate General for Research of the Commision of the European Communities (6 RP)	FOOD-CT-505609	Professor Robert Nilson	2004 - 07
Genetic profiles of genes encoding xenobiotic metabolising and DNA repair enzymes in cancer patients and controls in the Czech Republic	IGA MZ ČR	IGA NR 8563-5/2005	Pavel Vodička, MD., PhD.	2005 - 09
Case-control study on colorectal carcinoma: Genetic profiling of xenobiotic metabolising and DNA repair enzymes	GAČR	GACR No 310/05/2626	Pavel Vodička, MD., PhD.	2005 - 07

1988 | 1989 | 1991 | 1992 | 1993 | 1994 | 1995 | 1996
1997 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009