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Mycoplasma promotes malignant transformation in vivo, and its DnaK, a bacterial chaperone protein, has broad oncogenic properties.

ABSTRACT: We isolated a strain of human mycoplasma that promotes lymphomagenesis in SCID mice, pointing to a p53-dependent mechanism similar to lymphomagenesis in uninfected p53^-/- SCID mice. Additionally, mycoplasma infection in vitro reduces p53 activity. Immunoprecipitation of p53 in mycoplasma-infected cells identified several mycoplasma proteins, including DnaK, a member of the Hsp70 chaperon family. We focused on DnaK because of its ability to interact with proteins. We demonstrate that mycoplasma DnaK interacts with and reduces the activities of human proteins involved in critical cellular pathways, including DNA-PK and PARP1, which are required for efficient DNA repair, and binds to USP10 (a key p53 regulator), impairing p53-dependent anticancer functions. This also reduced the efficacy of anticancer drugs that depend on p53 to exert their effect. mycoplasma was detected early in the infected mice, but only low copy numbers of mycoplasma DnaK DNA sequences were found in some primary and secondary tumors, pointing toward a hit-and-run/hide mechanism of transformation. Uninfected bystander cells took up exogenous DnaK, suggesting a possible paracrine function in promoting malignant transformation, over and above cells infected with the mycoplasma. Phylogenetic amino acid analysis shows that other bacteria associated with human cancers have similar DnaKs, consistent with a common mechanism of cellular transformation mediated through disruption of DNA-repair mechanisms, as well as p53 dysregulation, that also results in cancer-drug resistance. This suggests that the oncogenic properties of certain bacteria are DnaK-mediated.

SUBMITTER: Zella D

PROVIDER: S-EPMC6304983 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Mycoplasmas are the smallest microorganisms capable of self-replication. Our previous studies show that some mycoplasmas are able to induce malignant transformation of host mammalian cells. This malignant transformation is a multistage process with the early infection, reversible and irreversible stages, and similar to human tumor development in nature. The purpose of this study is to explore mechanisms for this malignant transformation. METHODS: To better understand mechanisms for this unique process, we examined gene expression profiles of C3H cells at different stages of the mycoplasma-induced transformation using cDNA microarray technology. A total of 1185 genes involved in oncogenesis, apoptosis, cell growth, cell-cycle regulation, DNA repair, etc. were examined. Differences in the expression of these genes were compared and analyzed using the computer software AtlasImage. RESULTS: Among 1185 genes screened, 135 had aberrant expression at the early infection stage, 252 at the reversible stage and 184 at the irreversible stage. At the early infection stage, genes with increased expression (92 genes) were twice more than those with decreased expression (42 genes). The global gene expression at the reversible stage appeared to be more volatile than that at any other stages but still resembled the profile at the early infection stage. The expression profile at the irreversible stage shows a unique pattern of a wide range of expression levels and an increased number of expressing genes, especially the cancer-related genes. Oncogenes and tumor suppressors are a group of molecules that showed significant changes in expression during the transformation. The majority of these changes occurred in the reversible and irreversible stages. A prolonged infection by mycoplasmas lead to the expression of more cancer related genes at the irreversible stage. CONCLUSION: The results indicate that the expression profiles correspond with the phenotypic features of the cells in the mycoplasma induced transformation process. The early mycoplasma infection stage shares a common phenomenon with many other acute infections, genes with increased expression significantly outnumbering those with decreased expression. The reversible stage is a transition stage between benignancy and malignancy at the molecular level. Aberrant expression of oncogenes and tumor repressors plays a key role in mycoplasma-induced malignant transformation.

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Mycoplasma promotes malignant transformation in vivo, and its DnaK, a bacterial chaperone protein, has broad oncogenic properties.

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