Loss of ΔNp63α promotes mitotic exit in epithelial cells

Epstein-Barr Virus Gene BARF1 Expression is Regulated by the Epithelial Differentiation Factor ΔNp63α in Undifferentiated Nasopharyngeal Carcinoma

Epstein-Barr Virus (EBV) BamHI-A rightward frame 1 (BARF1) protein is considered a viral oncogene in epithelial cells and has immune-modulating properties. During viral lytic replication BARF1 is expressed as an early gene, regulated by the immediate early EBV protein R. However, in viral latency BARF1 is exclusively expressed in epithelial tumors such as nasopharyngeal (NPC) and gastric carcinoma (GC) but not in lymphomas, indicating that activation of the BARF1 promoter is cell type specific. Undifferentiated NPC is characterized by high expression of ΔNp63 isoforms of the epithelial differentiation marker p63, a member of the p53 family of transcription factors. Transcription factor binding site analysis indicated potential p53 family binding sites within the BARF1 promoter region. This study investigated ability of various p53 family members to transactivate the BARF1 promoter. Using BARF1 promoter luciferase reporter constructs we demonstrate that only p63 isoform ΔNp63α is capable of transactivating the BARF1 promoter, but not the TAp63 isoforms, p53 or p73. Direct promoter binding of ΔNp63α was confirmed by Chromatin Immune Precipitation (ChIP) analysis. Deletion mutants of the BARF1 promoter revealed multiple ΔNp63 response elements to be responsible for BARF1 promoter transactivation. However, ΔNp63α alone was not sufficient to induce BARF1 in tumor cells harboring full EBV genomes, indicating that additional cofactors might be required for full BARF1 regulation. In conclusion, in EBV positive NPC and GC, BARF1 expression might be induced by the epithelial differentiation marker ΔNp63α, explaining BARF1 expression in the absence of lytic reactivation.

ΔNp63α controls YB-1 protein stability: evidence on YB-1 as a new player in keratinocyte differentiation

Y-box binding protein 1 (YBX-1 or YB-1) is an oncoprotein that promotes replicative immortality, tumor cell invasion and metastasis. The increase in the abundance of YB-1 in the cell or YB-1 translocation from the cytoplasm to the nucleus is characteristic of malignant cell growth. We have previously reported that ΔNp63α, a transcription factor that is known to play a pivotal role in keratinocyte proliferation and differentiation, promotes YB-1 nuclear accumulation. Here, we show that YB-1 is highly expressed in proliferating keratinocytes and is down-regulated during keratinocyte differentiation. ΔNp63α reduces YB-1 protein turnover and leads to accumulation of ubiquitin-conjugated YB-1 into the nucleus. Reduction of YB-1 protein level, following treatment with a DNA-damaging agent, is inhibited by ΔNp63α suggesting that YB-1 and ΔNp63α interplay can support keratinocyte proliferation and protect cells from apoptosis under genotoxic stress.

ΔNp63 activates the Fanconi anemia DNA repair pathway and limits the efficacy of cisplatin treatment in squamous cell carcinoma

TP63, a member of the p53 gene family gene, encodes the ΔNp63 protein and is one of the most frequently amplified genes in squamous cell carcinomas (SCC) of the head and neck (HNSCC) and lungs (LUSC). Using an epiallelic series of siRNAs with intrinsically different knockdown abilities, we show that the complete loss of ΔNp63 strongly impaired cell proliferation, whereas partial ΔNp63 depletion rendered cells hypersensitive to cisplatin accompanied by an accumulation of DNA damage. Expression profiling revealed wide-spread transcriptional regulation of DNA repair genes and in particular Fanconi anemia (FA) pathway components such as FANCD2 and RAD18 - known to be crucial for the repair of cisplatin-induced interstrand crosslinks. In SCC patients ΔNp63 levels significantly correlate with FANCD2 and RAD18 expression confirming ΔNp63 as a key activator of the FA pathway in vivo Mechanistically, ΔNp63 bound an upstream enhancer of FANCD2 inactive in primary keratinocytes but aberrantly activated by ΔNp63 in SCC. Consistently, depletion of FANCD2 sensitized to cisplatin similar to depletion of ΔNp63. Together, our results demonstrate that ΔNp63 directly activates the FA pathway in SCC and limits the efficacy of cisplatin treatment. Targeting ΔNp63 therefore would not only inhibit SCC proliferation but also sensitize tumors to chemotherapy.

Effects of curcumin on the gene expression profile of L-02 cells

Curcumin has been utilized in the treatment and prevention of disease, including cancer and cardiovascular disease, but the molecular mechanism behind such numerous effects remains unclear. To explore the molecular mechanism and action sites of curcumin at the cellular level, human hepatic L-02 cells were used to assess these effects. Microarray technology was employed to detect the gene expression of L-02 cells treated with curcumin. According to the microarray results and the data from the National Center for Biotechnology Information, the present study classified and concluded that these curcumin-sensitive genes were associated with diseases and their signaling pathway. The study supports the evidence for treating cancer and cardiovascular disease, and found certain potential marker genes for conducting systematic research into the effects of curcumin. A total of 80 genes were identified as significantly differentially expressed between samples treated with and without curcumin. Curcumin is capable of developing physiological reactions and functions by regulating the gene expression and affecting its signal transduction pathway. Tumor protein p63, MYC-associated factor X and certain other genes associated with tumors act on a potential therapeutic target, while apolipoprotein B receptor and oxysterol-binding protein-like 7, and their signaling pathways may be involved in the cardioprotective effects of curcumin.

Characterization of a novel cell line from the caudal fin of koi carp Cyprinus carpio

A continuous cell line (KF-101) derived from the caudal fin of the koi carp Cyprinus carpio was established and characterized. The KF-101 cell line multiplied abundantly in Leibovitz's L-15 medium containing 10% foetal bovine serum at 25° C, and was subcultured for >90 passages over a period of 3 years. Immunocytochemistry revealed that the KF-101 cells contain keratin, junction proteins connexin-43 and occludin, and ectodermal stem-cell marker Pax-6, but not vimentin. Furthermore, the KF-101 cells reacted with anti-human DARPP-32 and anti-human GATA-4 antibodies, and the labelling was regulated according to the cell cycle. The labels of the DARPP-32 and GATA-4 antibodies in the KF-101 cells were the suggested phosphatase-1 inhibitor-1 and GATA-3, respectively. In addition, the KF-101 cells were susceptible to koi herpesvirus but were resistant to eel herpesvirus, iridovirus, grouper nodavirus and chum salmon (Oncorhynchus keta) virus. The results indicate that the KF-101 cells are suitable materials for investigating biological and virological development.

MicroRNAs in pathogenesis, diagnosis, and treatment of gastroesophageal cancers

The incidence of gastroesophageal cancers is increasing each year, but despite much research, their molecular mechanisms are incompletely understood. microRNAs (miRNAs) are noncoding RNAs that have been associated with gastroesophageal carcinogenesis. We review the involvement of miRNAs in gastric and esophageal cancers and their mechanisms of regulation, effects on gene expression, and biological functions. Many miRNAs are dysregulated in gastroesophageal cancer cells via alterations in transcription, epigenetic features, or copy number of the genes that encode them. Each type of gastroesophageal tumor has a unique gene expression profile. miRNAs contribute to gastroesophageal carcinogenesis by altering expression of oncogenes and tumor suppressors to affect cell proliferation, apoptosis, and motility and invasion. A number of miRNAs, including circulating miRNAs, have been associated with tumor type or stage, or patient survival, and might be developed as diagnostic or prognostic markers. Greater understanding of the roles of miRNAs in gastroesophageal carcinogenesis could provide insights into the mechanisms of tumor development and identify therapeutic targets.