No abstract

Recent data indicate that, similar to p63 and p73, several different p53 isoforms can be produced in humans through alternative initiation of translation, usage of an internal promoter and alternative splicing. These isoforms are reported to have varying functions and expressions. In squamous cell carcinoma of the head and neck (SCCHN), disruption of the p53 pathway is one of the most common genetic alterations. However, to our knowledge, no studies regarding the expression of different p53 isoforms in SCCHN have so far been performed. We screened for the expression of different p53 isoforms in SCCHN and clinically normal oral epithelia using nested RT-PCR. p53 mRNA was expressed in all tumours, all matched clinically normal tissue adjacent to the tumour and in buccal mucosa from healthy volunteers. Of the novel isoforms, p53beta was detected in the majority of samples analysed, and all of the recently described isoforms were also detected in at least some tumour and normal epithelium samples, with the exception of Deltap53 isoforms. We conclude that p53 variant mRNAs are expressed in both normal oral stratified epithelium and SCCHN. Improvements in methodologies and reagents to detect and quantify p53 isoform expression in clinical material will be required to correlate p53 status with clinical outcomes.

The human p63 gene codes for multiple protein isoforms and is commonly over-expressed in squamous cell carcinoma of head and neck (SCCHN). This expression is predominantly of the DeltaN- and beta-isoforms, the former lacking the p53-related transactivation domain. p63 can activate or repress transcription of p53 and p73 target genes, but also has unique transcriptional targets and, unlike other p53 family members, is required for normal development and differentiation of squamous epithelia. We have identified novel targets of p63, using microarray analysis of SCCHN cells that stably over-express individual DeltaNp63 isoforms. All three isoforms induced expression of the cancer stem cell marker, CD44, with the DeltaNp63beta isoform showing strongest induction. Using chromatin immunoprecipitation, we were unable to show direct binding of p63 to the CD44 promoter, but found that p63 specifically increased expression of CD44 lacking variant exon 2. Each of the DeltaNp63 isoforms up-regulated expression of keratins 6A and 14 and down-regulated expression of keratins 4 and 19, in keeping with their expression patterns in SCCHN. The data strengthen the idea that p63 has key roles in regulating normal and abnormal differentiation processes through both induction and repression of genes with opposite functions. The identification of up-regulation and differential splicing of CD44 following p63 over-expression indicates roles in the regulation of adhesion, metastasis and the cancer stem cell phenotype.

No abstract

A growing number of long non-coding RNAs (lncRNAs) have been linked to squamous cell carcinoma of the head and neck (SCCHN). A subclass of lncRNAs, termed enhancer RNAs (eRNAs), are derived from enhancer regions and could contribute to enhancer function. In this study, we developed an integrated data analysis approach to identify key eRNAs in SCCHN. Tissue-specific enhancer-derived RNAs and their regulated genes previously predicted using the computational pipeline PreSTIGE, were considered as putative eRNA-target pairs. The interactive web servers, TANRIC (the Atlas of Noncoding RNAs in Cancer) and cBioPortal, were used to explore the RNA levels and clinical data from the Cancer Genome Atlas (TCGA) project. Requiring that key eRNAs should show significant associations with overall survival (Kaplan–Meier log-rank test, p < 0.05) and the predicted target (correlation coefficient r > 0.4, p < 0.001), we identified five key eRNA candidates. The most significant survival-associated eRNA was AP001056.1 with ICOSLG encoding an immune checkpoint protein as its regulated target. Another 1640 genes also showed significant correlation with AP001056.1 (r > 0.4, p < 0.001), with the “immune system process” being the most significantly enriched biological process (adjusted p < 0.001). Our results suggest that AP001056.1 is a key immune-related eRNA in SCCHN with a positive impact on clinical outcome.

Background:MicroRNAs (miRNAs) are small noncoding RNA molecules with an essential role in regulation of gene expression. miRNA expression profiles differ between tumor and normal control tissue in many types of cancers and miRNA profiling is seen as a promising field for finding new diagnostic and prognostic tools.Materials and Methods:In this study, we have analyzed expression of three miRNAs, miR-21, miR-125b, and miR-203, and their potential target proteins p53 and p63, known to be deregulated in squamous cell carcinoma of the head and neck (SCCHN), in two distinct and one mixed subsite in squamous cell carcinoma in the oral cavity.Results:We demonstrate that levels of miRNA differ between tumors of different subsites with tongue tumors showing significant deregulation of all three miRNAs, whereas gingival tumors only showed significant downregulation of miR-125b and the mixed group of tumors in tongue/floor of the mouth showed significant deregulation of miR-21 and miR-125b. In the whole group of oral squamous cell carcinoma (SCC), a significant negative correlation was seen between miR-125b and p53 as well as a significant correlation between TP53 mutation status and miR-125b.Conclusion:The present data once again emphasize the need to take subsite into consideration when analyzing oral SCC and clearly show that data from in vitro studies cannot be transferred directly to the in vivo situation.

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SummaryOral lichen planus (OLP) is a chronic inflammatory disease of unknown origin, showing little spontaneous regression. WHO classifies OLP as a premalignant condition, however, the underlying mechanisms initiating development of cancer in OLP lesions are not understood. The p53 tumour suppressor plays an important role in many tumours, and an increased expression of p53 protein has been seen in OLP lesions. Recently it was shown that the human TP53 gene encodes at least nine different isoforms. Another member of the p53 family, p63, comprises six different isoforms and plays a crucial role in the formation of oral mucosa, salivary glands, teeth and skin. It has also been suggested that p63 is involved in development of squamous cell carcinoma of the head and neck (SCCHN). In contrast to p53, a decreased expression of p63 protein has been seen in OLP lesions. In this study, we mapped the expression of five novel p53 isoforms at RNA and protein levels in OLP and matched normal controls. In the same samples we also measured levels of p63 isoforms using quantitative RT–PCR. Results showed p53 to be expressed in all OLP lesions and normal tissues. The p53β and Δ133p53 isoforms were expressed in the majority of samples whereas the remaining three novel isoforms analysed were expressed in only a few samples. Levels of p63 isoforms were lower in OLP lesions compared with normal tissue, however, changes were not statistically significant.