RESUMO
The therapeutic thiopurines, including the immunosuppressant azathioprine (Aza) cause the accumulation of the UVA photosensitizer 6-thioguanine (6-TG) in the DNA of the patients' cells. DNA 6-TG and UVA are synergistically cytotoxic and their interaction causes oxidative damage. The MUTYH DNA glycosylase participates in the base excision repair of oxidized DNA bases. Using Mutyh-nullmouse fibroblasts (MEFs) we examined whether MUTYH provides protection against the lethal effects of combined DNA 6-TG/UVA. Surprisingly, Mutyh-null MEFs were more resistant than wild-type MEFs, despite accumulating higher levels of DNA 8-oxo-7,8-dihydroguanine (8-oxoG).Their enhanced 6-TG/UVA resistance reflected the absence of the MUTYH protein and MEFs expressing enzymatically-dead human variants were as sensitive as wild-type cells. Consistent with their enhanced resistance, Mutyh-null cells sustained fewer DNA strand breaks and lower levels of chromosomal damage after 6-TG/UVA. Although 6-TG/UVA treatment caused early checkpoint activation irrespective of the MUTYH status, Mutyh-null cells failed to arrest in S-phase at late time points. MUTYH-dependent toxicity was also apparent in vivo. Mutyh-/- mice survived better than wild-type during a 12-month chronicexposure to Aza/UVA treatments that significantly increased levels of skin DNA 8-oxoG. Two squamous cell skin carcinomas arose in Aza/UVA treated Mutyh-/- mice whereas similarly treated wild-type animals remained tumor-free.
Assuntos
DNA Glicosilases/metabolismo , DNA/metabolismo , Tioguanina/efeitos adversos , Animais , Humanos , Camundongos , Tioguanina/metabolismo , Transfecção , Raios Ultravioleta/efeitos adversosRESUMO
Analysis of seven candidate genes mapping in the 1-Mb region of the mouse pulmonary adenoma resistance 4 (Par4) locus revealed a single amino-acid change, consisting in a nonconservative Arg968Cys variation in the juxtamembrane domain of the Met proto-oncogene-encoded protein. The BALB/c strain (resistant allele) carried the Arg allele, whereas the SWR/J mouse strain (Par4-susceptible allele) carried the Cys variation, recently proven to functionally modulate tumorigenesis. Seven genetic linkage crosses herein analysed and six crosses reported in the literature pointed to the candidacy of the Met gene for Par4. Analysis of genomic DNA of 126 lung adenocarcinoma patients for the Met juxtamembrane domain revealed the same Arg/Cys variation at the mouse homologous position in one patient; two other patients carried additional variants in the same domain, suggesting a potential role for rare MET juxtamembrane variants in human lung cancer.
Assuntos
Adenocarcinoma/genética , Adenocarcinoma/fisiopatologia , Carcinoma Pulmonar de Células não Pequenas/genética , Carcinoma Pulmonar de Células não Pequenas/fisiopatologia , Transformação Celular Neoplásica , Predisposição Genética para Doença , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/fisiopatologia , Proteínas Proto-Oncogênicas/genética , Receptores de Fatores de Crescimento/genética , Alelos , Sequência de Aminoácidos , Animais , Arginina , Cisteína , Análise Mutacional de DNA , Modelos Animais de Doenças , Ligação Genética , Mutação em Linhagem Germinativa , Humanos , Camundongos , Camundongos Endogâmicos , Dados de Sequência Molecular , Herança Multifatorial , Proto-Oncogene Mas , Proteínas Proto-Oncogênicas c-met , Receptores de Trombina , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Reasons for early onset skin cancer are poorly understood. Microarray analysis revealed overexpression of the Scca2 gene in the 12-O-tetradecanoylphorbol-13-acetate-treated skin of Car-S mice, or line phenotypically selected for high susceptibility to two-stage skin carcinogenesis, as compared with 12-O-tetradecanoylphorbol-13-acetate-treated skin of Car-R mice, which is resistant. A human skin squamous cell carcinoma cell line (NCI-H520) transfected with mouse Scca2 or a related gene, Scca2-rs1, both expressed in the skin, showed significantly increased tumor growth as compared with controls when injected in nude mice. Immunohistochemical analysis of samples from two independent series of Italian and Korean patients with squamous cell carcinoma of the skin indicated a significant association between SCCA2 protein expression and younger age at tumor onset. These findings provide evidence that SCCA2-like serpins mediate genetic predisposition to skin cancer in a mouse model and in humans.
Assuntos
Antígenos de Neoplasias/genética , Carcinoma de Células Escamosas/genética , Serpinas/genética , Neoplasias Cutâneas/genética , Adulto , Idoso , Animais , Antígenos de Neoplasias/biossíntese , Carcinoma de Células Escamosas/induzido quimicamente , Carcinoma de Células Escamosas/metabolismo , Divisão Celular/genética , Predisposição Genética para Doença , Humanos , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Análise de Sequência com Séries de Oligonucleotídeos , Serpinas/biossíntese , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/metabolismo , Acetato de Tetradecanoilforbol , TransfecçãoRESUMO
The Car-R outbred mouse line was phenotypically selected for high resistance to two-stage skin tumorigenesis. In the present study we tested the hypothesis that a subset of genetic loci responsible for resistance to skin tumorigenesis of Car-R mice might also inhibit lung tumorigenesis. Skin and lung tumorigenesis were induced in groups of Car-R, SWR/J, (SWR/JxCar-R)F1 and SWR/Jx(SWR/JxCar-R) backcross mice by i.p. urethane initiation and skin TPA promotion. Car-R mice showed a much lower susceptibility to both skin and lung tumorigenesis as compared to SWR/J mice, which are susceptible to both lung and skin tumorigenesis. The Car-R-inherited genome significantly inhibited both skin and lung cancer development in the F1 progeny of Car-R with SWR/J mice. In the backcross population, skin and lung tumor phenotypes showed a statistically significant correlation, indicating that a subset of the cancer resistance alleles, which segregated in the Car-R line during selection for resistance to skin carcinogenesis, provides resistance to both skin and lung tumorigenesis.
