RESUMO
In the present study, the expression of P53 and MDM2 proteins were examined in 94 soft-tissue sarcomas (35 malignant fibrohistiocytomas, 15 neurosarcomas, 14 liposarcomas, 13 leiomyosarcomas, 11 fibrosarcomas and 6 dermatofibrosarcomas) by immunohistochemistry. The immunohistochemical findings were correlated with P53 mutation analysis using PCR-SSCP, PCR-HDF and direct sequencing, and MDM2 amplification studies by differential PCR. P53 immunopositivity was found in 25 out of 94 (26.6%) cases. Alterations of the P53 gene were detected in 12 (12.8%) tumors; eight of these tumors revealed P53 immunoreactivity. A high number of P53 positive and P53 mutated tumors were histologically defined as poorly differentiated G3 (64.0% and 75.0%, respectively). MDM2 immunopositivity was revealed in 36 out of 94 (38.3%) cases. MDM2 amplification occurred in 17 tumors (18.1%); only nine of these tumors exhibited MDM2 immunoreactivity. Overall, MDM2 positivity was not associated with MDM2 amplification in 27 out of 94 tumors (28.7%). There was no significant correlation between MDM2 overexpression and histological grade. However, when the samples were stratified by immunophenotype, the majority of tumors (52.5%) with isolated MDM2 overexpression (dissociated from P53 positivity) were defined histologically as low grade (G1 + G2). These results support the notion that besides P53 alterations, MDM2 gene deregulation seems to be an important event in sarcomas evolution. Additionally, the mechanism of MDM2-mediated degradation of P53 protein, without involving stabilization and inactivation of P53 gene, should be considered for better understanding of all features of tumor progression processes.
Assuntos
Biomarcadores Tumorais/genética , Genes p53 , Proteínas de Neoplasias/genética , Proteínas Nucleares , Proteínas Proto-Oncogênicas/genética , Sarcoma/genética , Neoplasias de Tecidos Moles/genética , Proteína Supressora de Tumor p53/análise , Adulto , Idoso , Idoso de 80 Anos ou mais , Biomarcadores Tumorais/análise , Análise Mutacional de DNA , Dermatofibrossarcoma/química , Dermatofibrossarcoma/genética , Feminino , Fibrossarcoma/química , Fibrossarcoma/genética , Amplificação de Genes , Análise Heteroduplex , Humanos , Leiomiossarcoma/química , Leiomiossarcoma/genética , Lipossarcoma/química , Lipossarcoma/genética , Masculino , Pessoa de Meia-Idade , Proteínas de Neoplasias/análise , Reação em Cadeia da Polimerase , Polimorfismo Conformacional de Fita Simples , Proteínas Proto-Oncogênicas/análise , Proteínas Proto-Oncogênicas c-mdm2 , Splicing de RNA , Sarcoma/química , Sarcoma/patologia , Neoplasias de Tecidos Moles/química , Neoplasias de Tecidos Moles/patologiaRESUMO
A protein showing lower electrophoretic mobility in acidic urea polyacrylamide gels than did the usual histone H1 subfractions has been detected among the H1 histones extracted from chromatin of a transplantable hamster hepatoma, originally induced by Kirkman and Robbins. It was proved to be a true H1 histone subfraction. It differs from the remaining ones by the total chain length, amino acid composition, and isoelectric point value. It is not a phosphorylated or phosphoribosylated metabolic form of another subfraction. Its proteolytic degradation products (obtained by thrombin and trypsin digestion) closely resembled those obtained from other H1 subfractions. The investigated hepatoma seems to provide an interesting model of neoplastic cells showing a distinct difference in histone composition from the homologous normal tissue.
Assuntos
Histonas/análise , Sequência de Aminoácidos , Aminoácidos/análise , Animais , Cromatina/metabolismo , Cromatografia DEAE-Celulose , Cricetinae , Eletroforese em Gel de Poliacrilamida , Histonas/isolamento & purificação , Ponto Isoelétrico , Neoplasias Hepáticas Experimentais/metabolismo , Peso Molecular , Trombina , TripsinaRESUMO
Electrophoretically slow H1 histone subfractions with mobilities identical to that of the subfraction found in the Kirkman-Robbins hamster hepatoma chromatin have been shown to be present in 12-day hamster embryos and in a sarcoma-type hamster tumor induced by SV40. No subfractions of such mobility were found in hamster liver, regenerating liver, thymus, spleen, and a fast-growing transplantable amelanotic hamster melanoma. A suggestion is made that some defective mechanisms of differentiation may affect the regulation of expression of the genes coding for the H1 histone subfractions. The same mechanisms may possibly but not necessarily be connected with the molecular events leading to neoplastic growth.
