Eixo XPC-P53-H202 e disfunção mitocondrial: qual é o fator central? / XPC-p53-H2O2 axis and mitochondrial disfunction: Which is the key player

A ausência de XPC, uma proteína canonicamente envolvida em reparo de DNA por excisão de nucleotídeos, está associada a vários fenótipos característicos de disfunção mitocondrial como o desequilíbrio entre os complexos da cadeia transportadora de elétrons (CTE), redução no consumo de oxigênio, maior produção de peróxido de hidrogênio, e maior sensibilidade a agentes que causam estresse mitocondrial. Contudo, uma descrição mecanística da relação entre deficiência de XPC e disfunção mitocondrial ainda não está bem estabelecida. Aqui mostramos que a deficiência de XPC está associada ao aumento na expressão do supressor de tumor p53. Essa alteração é acompanhada pelo aumento da expressão de diversas proteínas que participam em importantes funções mitocondriais. A inibição de p53 reverte a superexpressão de algumas dessas proteínas. O tratamento com o inibidor do Complexo III da CTE antimicina A induz aumento da expressão de p53 de forma mais acentuada na linhagem Xpc-/-, enquanto o tratamento com o antioxidante N-acetilcisteína diminue a produção basal de H2O2, expressão de p53 e sensibilidade aumentada ao tratamento com antimicina A. Em conjunto, nossos resultados suportam a hipótese de que o aumento da produção de H2O2 em células Xpc-/- tem um papel causal na regulação da expressão de p53 e na disfunção mitocondrial

Although XPC has been initially implicated in the nucleotide excision DNA repair pathway, its deficiency is associated with mitochondrial dysfunction, including unbalanced electron transport chain (ETC) activity, lower oxygen consumption, increased hydrogen peroxide production, and greater sensitivity to mitochondrial stress. However, a mechanistic understanding of the role of XPC in regulating mitochondrial function is still not well established. Here we show that XPC deficiency is associated with increased expression of the tumor suppressor p53, which is accompanied by increased expression of several proteins that participate in important mitochondrial functions. Inhibition of p53 reverses the overexpression of some of these proteins. In addition, treatment with the ETC inhibitor antimycin A induces p53 expression more robustly in the Xpc-/- cells, while treatment with the antioxidant N-acetylcysteine decreases basal H2O2 production, p53 expression and sensitivity to antimycin A treatment. Together, our results support a model in which increased H2O2 production in Xpc-/- causes upregulation of p53 expression and mitochondrial dysfunction

effect of exogenous expression of TP53 gene carried by dendrosme, an lranian vector, on human T-lymphomd and leukemia cells

The tumor suppressor p53 protein can induce apoptosis in some cellular contexts. Among the apoptosis-inducing genes, p53 has received the most attention for cancer gene therapy. In this study, the role of Dendrosome and Lipofectin mediated normal cDNA of TP53 into MOLT-4, CCRF-CEM[T-lymphoma] and K562 cell lines was assessed. At first, CCRF-CEM, MOLT-4 and K562 [erythroleukemic] cell lines were transfected by Dendrosome and Lipofectin separately. Then, viability study was carried out by Trypan blue exclusion. The rate of apoptosis and necrosis in transfected cell lines was evaluated by Flow Cytometry. Trypan blue exclusion assay in K562 and CCRF-CEM revealed 55.8% and 17.97% viability reduction in the Dend+p53 in comparison to Dend+pcDNA3 [control], respectively. Flow Cytometry studies confirmed a significant enhancement of apoptosis and necrosis in TP53 transrected K562 and CCRF-CEM cells. Flow Cytometry and viability studies on transfected MOLT-4 cells showed no significant changes. The results showed that expression of normal cDNA of TP53 in K562 and CCRF-CEM cell lines could induce apoptosis in these cell lines with different levels. Transfection of MOLT-4 cell Line by Dend+p53 and Lipo+53 could not result in apoptosis

Relación entre P53, estadío y pronóstico en el cancer colorrectal: nuestra experiencia / Correlation between p53, staging and prognosis in colorectal cancer: our experience

La recidiva locoregional en cáncer de colon y recto es uno de los mayores problemas que enfrenta el cirujano de colon y el encólogo. Una adecuada estadificación es esencial para planificar y establecer el tratamiento post operatorio. P53 es un evento frecuente en el cáncer de colon y recto y se postuló como un posible factor pronóstico independiente. Objetivo: este estudio fue diseñado para evaluar si la sobreexpresión de p53 en pacientes con carcinoma primario de colon y recto con seguimiento clínico mayor de 5 años en estadío A, B ó C de Dukes y correlacionar con edad, sexo, grado de diferenciación histológico y nuclear, estadíos de Dukes y supervivencia. Resultados: sobreexpresión de p53 se detectó en 32 pacientes (71 por ciento). No se encontró diferencia significativa entre la sobreexpresión de p53 y los factores clínico-patológicos analizados. Se encontró correlación estadística entre estadío de Dukes y supervivencia. Conclusión: en nuestro estudio no hemos encontrado que p53 fuera un factor pronóstico independiente en los estadíos A, B y C de Dukes. El estadío de Dukes continúa siendo el factor pronóstico más importante.

Immunohistochemical study of p53 in gastric carcinoma

P53 is a tumor suppressor gene product identified in a wide variety of tumors. It is a nuclear phosphoprotein encoded by a gene at position 13 on the short arm of chromosome 17. Studies have shown that wild type p53 has an inhibitory effect on cell proliferation and transformation. Mounting evidence indicated that p53 is involved in the pathogenesis of a large proportion of human neoplasms as a major biochemical regulator of growth control. Mutation of p53 was found in 50% of gastric cancer and 90% of esophageal cancer. This work studied the accumulation of p53 by immunohistochemistry in 20 patients with gastric carcinoma who underwent surgery in Kasr El-Aini Hospital. Expression of the p53 protein was found in 50% of all tumors. Expression of p53 was found in 62.5% of patients with tumors in the upper region, 50% of the patients with tumors in the middle region and 33.3% of patients with tumors in the low region of the stomach. Expression of p53 was slightly common in the ulcerative type than in the polypoidal type. P53 was found in 54.5% of patients with advanced tumor and positive lymph node infiltration and in 44.4% of patients with early tumor and without lymph node infiltration. There was significant relationship between p53 expression and the histological type of the tumors. Many cancer cells in the intestinal type carcinomas showed nuclear p53 expression, but only few cells in diffuse type carcinomas expressed nuclear p53. The results suggested that gene alterations of p53 are not rare in gastric carcinoma and may participate in carcinogenesis of intestinal type carcinomas of the stomach. P53 expression is at present not a predictor of the outcome of patients with gastric carcinoma and can not identify subgroups of patients who may be at a higher risk

Determinación inmunohistoquímica de la proteína p53 en biopsias de cuello uterino / Immunohistochemistry determination of the p53 protein in cervical biopsy

El gen p53 regula el ingreso de las células a la fase S del ciclo celular mediante la síntesis de una proteína efectora. La mutación de este gen se relacionaría con la pérdida de la capacidad supresora y la concomitante progresión tumoral. La génesis del carcinoma de cérvix podría vincularse a la mutación del gen p53 por acción del ADN viral (HPV). Realizamos la inmunomarcación de la proteína p53 en 88 biopsias de cérvix. De éstas, 10 correspondieron a cuello normal, 41 a lesiones intraepiteliales de bajo grado, 24 a lesiones intraepiteliales de alto grado y 13 a carcinomas invasores. La positividad fue del 10 por ciento, 58,5 por ciento, 70,8 por ciento y 92,3 por ciento respectivamente. Se evaluó también: atipia coilocitótica, reacción inflamatoria, localización e intensidad de la inmunomarcación, tipo de carcinoma invasor, etc. En este informe queda demostrado que el mayor grado de lesión correlaciona con mayor expresión de proteína p53 anómala o mutada

The effects of wild type p53 tumor suppressor gene expression on the normal human cervical epithelial cells or human epidermal keratinocytes transformed with human papillomavirus type 16 DNA

The inactivation of p53 and p105RB by viral proteins or by mutations plays a key role in the oncogenesis of cervical carcinoma. The E6 and E7 proteins of HPV type 16 can bind to p53 and p105RB tumor suppressor gene products, respectively. In the present study, we tested a simple in vivo model that could explain the interactions between HPV E6 oncoprotein and p53 tumor suppressor protein. Our results showed that the life span of normal cervical epithelial cells was increased up to 4.5 times when transfected with expression vector containing E6/E7 ORF of HPV type 16. However, these cells did not divide after second crisis. Therefore, we employed an established human epidermal keratinocytes, RHEK-1. When transfected with an expression vector containing E6 ORF of HPV type 16, RHEK-1 cells showed anchorage independent growth character. When RHEK-E6 cells were transfected with wild type p53 expression vector, the growth rate of the RHEK-E6 cells was diminished. After 48 hours of transfection, many cells showed apoptotic signal but no more apoptotic signal was observed thereafter. These results suggested that the overexpression of the wild type p53 could overcome the dysfunction of the p53 on the cell cycle regulation imposed by E6 protein although not being of physiological condition.