Bacterial genotoxin colibactin as a risk factor of cancer development

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00027162%3A_____%2F22%3AN0000069" target="_blank" >RIV/00027162:_____/22:N0000069 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Bacterial genotoxin colibactin as a risk factor of cancer development

Original language description

Cancer is a complex of multifactorial processes and carcinogenesis can be induced beside other factors by chronical inflammatory disease and microbiota changes. Conversely, tumour cells may change the microenvironment and structure of microbiome. Nowadays, Helicobacter pylori is the best example of the role of bacteria in cancer promotion and finally, WHO classified this G- bacterium for gastric cancer as carcinogen of class I. It became evident that genetic events in cancer can be associated with abnormalities in microbiome. Pathogenic bacteria can secrete toxins that may have cytostatic or cytotoxic effects on host cells. It was described that E. coli harbouring polyketide synthase (pks) genes can synthetize bacterial toxin colibactin, which was first described by Nougayrede’s group in 2006. Colibactin increases the likelihood of gut colonisation or mucosal invasion and serious complications of bacterial infections, such as development of meningitis and potentially tumorigenesis. E. coli positive for pks genes were overexpressed in colorectal cancer biopsies. Although K. pneumoniae is an undoubted colonizer of the airway epithelial cells, the role of pks+ K. pneumoniae has not been investigated in either bronchial or pulmonary cells. The aim of our study was to compare cytotoxic effects of pks+ K. pneumoniae on epithelial cells. First of all, eighty K. pneumoniae strains were screened for pks genomic island by seven colibactin genes - clb A, B, M, N, P, Q, S. The strains were collected from food, animals, environment and humans, and stored at the strain collection. Moreover, whole genome sequencing (WGS) of bacterial strains and comparison with the international collection strain was performed based on core genome MLST (cgMLST). Next, human lung cancer cell line (A549), normal bronchial (HBEC-12KT) and cancer bronchial cells (HBEC-KT12-B1) were infected by different concentrations MOI 1-5-10-20-100-200-1000. The cells were washed 4 hours after infection and proliferation was analysed by flow cytometry (Amnis CellStream, Luminex Corporation) 24 hours after infection (24 hpi). The selected two pks+ K. pneumoniae and two pks- K. pneumoniae were used for next detail study. Protein expression of NSCLC driver genes, cell cycle and cell death were detected by Western blot (Biorad Laboratories and imaging system Vilber), confocal microscopy (Leica SP8) and flow cytometry analysis (Amnis CellStream, Luminex Corporation) 24 hpi. Our preliminary results have shown that the highest occurrence of pks genes was detected in human samples. Flow cytometry analysis showed that colibactin increased cell death and arrested cell cycle in G2/M in dose dependent manner. Finally, two selected pks+ K. pneumoniae and 2 selected pks- K. pneumoniae were used for infection of human epithelial cells and analysis of the effects of the bacterial toxin on cell death, cell cycle, DNA damage response and p21 expression. The human body colonizing consortium of microbes can affect cancer initiation, progression or therapy response. According to our knowledge, effects of colibactin producing K. pneumoniae on bronchial or lung cells has not been investigated at all, despite K. pneumoniae is a pathogen of respiratory tract. Our results showed that pks+ K. pneumoniae caused DNA damage response leading to the cell cycle arrest in G2/M phases in contrast to pks- K. pneumoniae. In conclusion, dysregulation of the cell cycle may result in uncontrolled cell proliferation or excessive cell death and thereby colibactin producing K. pneumoniae can contribute to carcinogenesis.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

30108 - Toxicology

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů