Identification of p53-target genes in human papillomavirus-associated head and neck cancer by integrative bioinformatics analysis.

Introduction: Head and neck cancer (HNC) is a highly prevalent and heterogeneous malignancy. Although extensive efforts have been made to advance its treatment, the prognosis remained poor with increased mortality. Human papillomaviruses (HPV) have been associated with high risk in HNC. TP53, a tumor suppressor, is the most frequently altered gene in HNC, therefore, investigating its target genes for the identification of novel biomarkers or therapeutic targets in HPV-related HNC progression is highly recommended. Methods: Transcriptomic profiles from three independent gene expression omnibus (GEO) datasets, including 44 HPV+ and 70 HPV- HNC patients, were subjected to integrative statistical and Bioinformatics analyses. For the top-selected marker, further in-silico validation in TCGA and GTEx databases and experimental validation in 65 (51 HPV- and 14 HPV+) subjects with histologically confirmed head and neck squamous cell carcinoma (HNSCC) have been performed. Results: A total of 498 differentially expressed genes (DEGs) were identified including 291 up-regulated genes and 207 down-regulated genes in HPV+ compared to HPV- HNSCC patients. Functional annotations and gene set enrichment analysis (GSEA) showed that the up-regulated genes were significantly involved in p53-related pathways. The integrative analysis between the Hub-genes identified in the complex protein-protein network and the top frequent genes resulting from GSEA showed an intriguing correlation with five biomarkers which are EZH2, MDM2, PCNA, STAT5A and TYMS. Importantly, the MDM2 gene showed the highest gene expression difference between HPV+ and HPV- HNSCC (Average log2FC = 1.89). Further in-silico validation in a large HNSCC cohort from TCGA and GTEx databases confirmed the over-expression of MDM2 in HPV+ compared to HPV- HNSCC patients (p = 2.39E-05). IHC scoring showed that MDM2 protein expression was significantly higher in HPV+ compared to HPV- HNSCC patients (p = 0.031). Discussion: Our findings showed evidence that over-expression of MDM2, proto-oncogene, may affect the occurrence and proliferation of HPV-associated HNSCC by disturbing the p53-target genes and consequently the p53-related pathways.

Isorhamnetin Promotes 53BP1 Recruitment through the Enhancement of ATM Phosphorylation and Protects Mice from Radiation Gastrointestinal Syndrome.

Flavonoids are a subclass of polyphenols which are attractive, due to possessing various physiological activities, including a radioprotective effect. Tumor suppressor p53 is a primary regulator in the radiation response and is involved in the pathogenesis of radiation injuries. In this study, we revealed that isorhamnetin inhibited radiation cell death, and investigated its action mechanism focusing on DNA damage response. Although isorhamnetin moderated p53 activity, it promoted phosphorylation of ataxia telangiectasia mutated (ATM) and enhanced 53BP1 recruitment in irradiated cells. The radioprotective effect of isorhamnetin was not observed in the presence of ATM inhibitor, indicating that its protective effect was dependent on ATM. Furthermore, isorhamnetin-treated mice survived gastrointestinal death caused by a lethal dose of abdominal irradiation. These findings suggested that isorhamnetin enhances the ATM-dependent DNA repair process, which is presumably associated with the suppressive effect against GI syndrome.

Loss of p53 enhances the function of the endoplasmic reticulum through activation of the IRE1α/XBP1 pathway.

Altered regulation of ER stress response has been implicated in a variety of human diseases, such as cancer and metabolic diseases. Excessive ER function contributes to malignant phenotypes, such as chemoresistance and metastasis. Here we report that the tumor suppressor p53 regulates ER function in response to stress. We found that loss of p53 function activates the IRE1α/XBP1 pathway to enhance protein folding and secretion through upregulation of IRE1α and subsequent activation of its target XBP1. We also show that wild-type p53 interacts with synoviolin (SYVN1)/HRD1/DER3, a transmembrane E3 ubiquitin ligase localized to ER during ER stress and removes unfolded proteins by reversing transport to the cytosol from the ER, and its interaction stimulates IRE1α degradation. Moreover, IRE1α inhibitor suppressed protein secretion, induced cell death in p53-deficient cells, and strongly suppressed the formation of tumors by p53-deficient human tumor cells in vivo compared with those that expressed wild-type p53. Therefore, our data imply that the IRE1α/XBP1 pathway serves as a target for therapy of chemoresistant tumors that express mutant p53.

Perfil de metilación de genes supresores de tumores APAF1, ASSP1, p73 y FHIT en pacientes con leucemia linfoblástica aguda infantil / Detection of hypermethylation in tumor suppressor genes APAF1, ASSP1, p73 and FHIT in childhood acute lymphoblastic leukemia

La leucemia linfoblástica aguda (LLA), es la neoplasia mas frecuente en la población infantil. Se manifiesta por una perdida de diferenciación de progenitores linfoides produciendo un aumento de células inmaduras. La hipermetilación en la región promotora de genes supresores de tumores (GST) puede producir un silenciamiento génico que le proporciona a la célula leucémica una ventaja proliferativa o la previene de la apoptosis. Se estudia el estado de hipermetilación de 4 GST involucrados en la apoptosis: APAF1, ASPP1, p73 y FHIT y su asociación con la sobrevida de pacientes menores de 15 años con diagnóstico de LLA. Se analizaron 38 muestras de médula ósea mediante modificación con bisulfito del ADN y reacción en cadena de la polimerasa especifica de metilación (MSP). El rango de edad al diagnóstico fue de 10 meses a 13,8 años. La sobrevida global fue de 69 por ciento a los 5 años. El 81,5 por ciento de los pacientes tuvo al menos un gen hipermetilado. La frecuencia de metilación observada fue: APAF1 68,4 por ciento, FHIT 56,4 por ciento, p73 42 por ciento y ASPP1 18,4 por ciento. La asociación entre hipermetilación y grupo <5 años y 5 años fue: Global p=0,20, APAF1 p=0,03, FHIT p=0,51, p73 p=0,51 y ASPP1 p=0.67. Las curvas de sobrevida se calcularon según frecuencia de hipermetilación de cada gen: APAF1 p=0,05, FHIT p=0,31, p73 p=0,98 y ASPP1 p=0,82. La alta frecuencia de hipermetilación obtenida reafirma la participación de la metilación en la región promotora de GST en la patogénesis de la LLA. La hipermetilación del gen APAF1 fue muy frecuente y se asoció significativamente a la sobrevida del grupo de estudio, mostrando a este gen como un factor predictivo de mal pronostico en pacientes con LLA.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. It is manifested by a loss of differentiation of lymphoid progenitors, producing an increase of immature cells. Hypermethylation in promoter region of tumor suppressor genes (GST) may produce a gene silencing that provides a leukemic cell a proliferative advantage or prevent apoptosis. We studied the hypermethylation status of 4 GST involved in apoptosis: APAF1, ASPP1, p73 and FHIT and its association with survival of patients <15 years diagnosed with ALL. We analyzed 38 samples of bone marrow by DNA bisulfite modification and chain reaction methylation-specific polymerase (MSP). The mean age at diagnosis was 10 months to 13.8 years. Overall survival was 69 percent at 5 years. 81.5 percent of patients had at least one hypermethylated gene. The frequency observed was: APAF1 68.4 percent, 56.4 percent FHIT, p73 ASPP1 42 percent and 18.4 percent. The association between hypermethylation and group <5 years and 5 years was: Global p = 0.20, APAF1 p = 0.03, FHIT p = 0.51, p73 p = 0.51, ASPP1 p = 0.67. Survival curves were calculated by frequency of hypermethylation of each gene: APAF1 p = 0.05, p = 0.31 FHIT, p73 p = 0.98 and ASPP1 p = 0.82. The high frequency of hypermethylation obtained confirms enrollment of methylation in the promoter region of GST in the pathogenesis of ALL. APAF1 gene hypermethylation was very frequent and was significantly associated with survival in the study group, showing this gene as a predictor of poor prognosis in patients with ALL.