ABSTRACT
Inorganic arsenic is a well-known carcinogen associated with several types of cancer, but the mechanisms involved in arsenic-induced carcinogenesis are not fully understood. Recent evidence points to epigenetic dysregulation as an important mechanism in this process; however, the effects of epigenetic alterations in gene expression have not been explored in depth. Using microarray data and applying a multivariate clustering analysis in a Gaussian mixture model, we describe the alterations in DNA methylation around the promoter region and the impact on gene expression in HaCaT cells during the transformation process caused by chronic exposure to arsenic. Using this clustering approach, the genes were grouped according to their methylation and expression status in the epigenetic landscape, and the changes that occurred during the cellular transformation were identified adequately. Thus, we present a valuable method for identifying epigenomic dysregulation.
Subject(s)
Arsenic/toxicity , Cell Transformation, Neoplastic/pathology , DNA Methylation/drug effects , Gene Expression Profiling/methods , Skin Neoplasms/pathology , Animals , Cell Line, Tumor , Cell Transformation, Neoplastic/chemically induced , Cell Transformation, Neoplastic/genetics , Epigenesis, Genetic/drug effects , Female , Gene Expression Regulation, Neoplastic/drug effects , Humans , Mice , Neoplasm Transplantation , Oligonucleotide Array Sequence Analysis , Promoter Regions, Genetic , Skin Neoplasms/chemically induced , Skin Neoplasms/geneticsABSTRACT
Canine transmissible venereal tumor (CTVT) is the only neoplasm that can be spread among dogs through cell transplantation. Therefore, this tumor does not originate from host cell transformation. Although CTVT has a monophyletic origin, several studies have shown the presence of genetic diversity which was probably acquired after the development of its original clone. To investigate the genetic diversity of CTVT in Mexico and its relation with CTVTs disseminated worldwide, we sequenced a fragment of mitochondrial DNA in 50 tumor samples and matched blood samples from dog hosts from Mexico. We found ten new haplotypes in tumor samples, which were all distinct from their matched host. The TVT1 haplotype was the most frequent in our samples, suggesting that it could be the origin of the others. We found that haplotypes in Mexico and other countries are distributed in two well-defined clusters. Our data also suggest a close relationship among American haplotypes (Mexico, USA, Chile and Brazil). Interestingly, these American haplotypes were also closely related to Asian haplotypes. Taking into account the estimated timing of the origin of CTVT, we propose that CTVT might have originated in Asia; consequently, haplotypes currently present in America could descend from Asiatic lineages.
Subject(s)
Dog Diseases/genetics , Phylogeny , Venereal Tumors, Veterinary/genetics , Animals , Base Sequence , DNA, Mitochondrial/genetics , Dogs , Genotype , Haplotypes/genetics , Locus Control Region/genetics , Mexico , Molecular Sequence Data , Polymorphism, Single Nucleotide , Sequence Analysis, DNA , Venereal Tumors, Veterinary/pathologyABSTRACT
The canine transmissible venereal tumor (CTVT) is found mainly in dogs' sexual organs. Currently, it is widely accepted that all samples of CTVT show similar histopathological characteristics and share common genetic alterations. Despite the common genetic origin of CTVT, mutations in the P53 gene have been reported. In this study, we proposed that tumor samples can be genetically grouped using this gene. The presence of different subgroups of CTVT was determined in Mexican dogs using the TP53 gene sequence in CTVT samples. Four new polymorphisms were found and therefore, the CTVT samples were classified in five subgroups.
Subject(s)
Dog Diseases/genetics , Polymorphism, Genetic , Tumor Suppressor Protein p53/genetics , Venereal Tumors, Veterinary/genetics , Animals , Base Sequence , Dogs , Gene Expression Regulation, Neoplastic/physiology , Molecular Sequence Data , MutationABSTRACT
Tumor necrosis factor alpha (TNF-alpha) is one of the best-described cell death promoters. In murine L929 fibroblasts, dexamethasone inhibits TNF-alpha-induced cytotoxicity. Since phosphatidyl inositol 3 kinase (PI3K) and nuclear factor kappa B (NF-kappaB) proteins regulate several survival pathways, we evaluated their participation in dexamethasone protection against TNF-alpha cell death. We interfered with these pathways by overexpressing a negative dominant mutant of PI3K or a non-degradable mutant of inhibitor of NF-kappaB alpha (IkappaBalpha) (the cytoplasmic inhibitor of NF-kappaB) in L929 cells. The mutant IkappaB, but not the mutant PI3K, abrogated dexamethasone-mediated protection. The loss of dexamethasone protection was associated with a diminished accumulation in XIAP and c-IAP proteins.
Subject(s)
Dexamethasone/pharmacology , NF-kappa B/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Tumor Necrosis Factor-alpha/metabolism , Animals , Blotting, Western , Cell Death , Cell Line , Cell Nucleus/metabolism , Cell Proliferation , Cell Survival , Dexamethasone/chemistry , Dose-Response Relationship, Drug , Down-Regulation , Fibroblasts/metabolism , Glucocorticoids/pharmacology , Inhibitor of Apoptosis Proteins , Mice , Mutation , Plasmids/metabolism , Proteins/metabolism , Signal Transduction , X-Linked Inhibitor of Apoptosis ProteinABSTRACT
BACKGROUND: Human papillomavirus (HPV) infection is the most prevalent factor in anogenital cancers. However, epidemiological surveys and molecular data indicate that viral presence is not enough to induce cervical cancer, suggesting that cellular factors could play a key role. One of the most important genes involved in cancer development is the RAS oncogene, and activating mutations in this gene have been associated with HPV infection and cervical neoplasia. Thus, we determined the effect of HRAS oncogene expression on cell proliferation in a cell line immortalized by E6 and E7 oncogenes. METHODS: HPV positive human cervical carcinoma-derived cell lines (HeLa), previously transfected with the HRAS oncogene or the empty vector, were used. We first determined the proliferation rate and cell cycle profile of these cells by using flow cytometry and BrdU incorporation assays. In order to determine the signaling pathway regulated by HRAS and implicated in the alteration of proliferation of these cells, we used specific chemical inhibitors to inactivate the Raf and PI3K pathways. RESULTS: We observed that HeLa cells stably transfected with oncogenic HRAS progressed faster than control cells on the cell cycle by reducing their G1 phase. Additionally, HRAS overexpression accelerated the G1/S transition. Specific chemical inhibitors for PI3K and MEK activities indicated that both PI3K/AKT and RAF/MEK/ERK pathways are involved in the HRAS oncogene-induced reduction of the G1 phase. CONCLUSIONS: Our results suggest that the HRAS oncogene could play an important role in the development of cervical cancer, in addition to the presence of HPV, by reducing the G1 phase and accelerating the G1/S transition of infected cells.
