p53 mutation is rare in oral mucosa brushings from patients previously treated for a head and neck squamous cell carcinoma

Downregulation of GBAS regulates oral squamous cell carcinoma proliferation and apoptosis via the p53 signaling pathway

Purpose: Oral squamous cell carcinoma (OSCC) is the most common and severe type of head and neck malignancy. The mechanisms by which OSCC arises depend on changes in a number of different factors and genes and the clinicopathological stage of the tumors. Better understanding the possible mechanisms of OSCC would help to identify a new target for molecular targeted therapy. The current study was focused on elucidating the significance of the glioblastoma-amplified sequence (GBAS) on malignant behaviors in OSCC, including proliferation and apoptosis.

Patients and methods: In this study, we measured the levels of mRNA in OSCC and normal oral tissue samples using Affymetrix microarrays. We examined GBAS expression in OSCC tissues and the effect of GBAS knockdown on cell proliferation and apoptosis in vitro and in vivo. The mechanisms underlying GBAS were investigated.

Results: In the present study, GBAS expression was substantially elevated in the majority of tested OSCC tissues. Further, knockdown of GBAS using lentiviral-delivered shRNA in cells had significant effects on cell proliferation, apoptosis and the cell cycle. A xenograft model was also used to assess the tumorigenicity of the GBAS knockdown on OSCC cells in vivo. Mechanistically, GBAS activated p53 signaling by regulating the mRNA and protein expression of CHEK1, AKT1, AKT2 and Bax. Finally, we also investigated the expression of GBAS in patients with OSCC, and the data revealed that GBAS expression was correlated with the rates of relapse and tumor grade.

Conclusion: Our studies provide evidence that GBAS regulates OSCC cell proliferation and apoptosis via p53 signaling, which may be a candidate biomarker for the prognosis and treatment of OSCC.

p53 Overexpression in Oral Mucosa in Relation to Shisha Smoking in Syria and Lebanon

Introduction

Shisha (waterpipe) smoking is becoming a very prevalent form of tobacco consumption in the Middle east and use is growing over the world. Smoking-related malignancies have a high genome-wide burden of mutations, including examples in the gene encoding p53.

Aims

To investigate alterations in p53 immunohistochemical expression in the normal, pre-malignant, malignant oral mucosa in relation to Shisha smoking habits.

Materials and Methods

A total of 105 paraffin embedded tissue sections of OSCCs (52 smokers,53 non-smokers), 96 of premalignant lesions (48 smokers,48 non-smokers) and 60 normal oral mucosa. Some 30 patients with a history of Shisha smoking daily for more than 5 years were also investigated for mutant expression of p53. Tissue samples were considered positive for p53 staining when any positive cells of epithelial origin could be detected.

Results

The majority (74.3%) of oral squamous cell carcinomas showed positive staining for p53 expression (83.1% and 65.5% with Shisha smokers and non-smokers, respectively). In the 96 premalignant lesions, about 23% from non-smokers and 41.7% from smokers showed p53 positivity. In normal epithelium, P53 positive cells were noted in 6.6% of non-smokers and 16.6% of smokers. Positive correlations with Shisha smoking were evident for the following groups: WDOSCC, MDOSCC, mild dysplasia G1, moderate dysplasia G2 and in normal mucosa using Student’s t- test, P value<0.05.

Conclusion

These results strongly suggest that p53 mutations are associated with Shisha smoking in OSCC, pre-malignant lesions and normal mucosa of the oral cavity.

No Mutation Detected in Five Hot Spot Codons of the Tp53 Gene by Restriction Site Mutation Analysis in Patients with Carcinoma of the Tongue

The present study evaluated 5 of the 8 main TP53 mutation hot spots in cancer by restriction site mutation analysis and compared the results with p53 protein expression in patients with cancer of the tongue. Tumor samples from 49 patients with tongue cancer were screened for TP53 mutations in exons 5 through 8 by PCR restriction site mutation analysis and for p53 protein expression by immunohistochemistry using the DO-7 antibody. Nuclear accumulation of p53 protein was seen in 22% (11/49) of the tumors, whereas none of the patients exhibited TP53 mutations in exons 5 through 8. The observed data suggest that TP53 mutations alone are not responsible for abnormal accumulation of p53 protein in tobacco-chewing-mediated tongue carcinogenesis.

Cytogenetic significance of chromosome 17 aberrations and P53 gene mutations as prognostic markers in oral squamous cell carcinoma

BACKGROUND

Cytogenetic analysis has detected an accumulation of genetic lesions in oral cancers. Numerical changes in chromosome 17 might be associated with an up-regulation of p53 gene, and could contribute to critical events in carcinogenesis. The aim of this study was to reveal possible correlations between the numerical aberrations of chromosome 17, deletion or amplification of the P53 gene and histological grading in patients with oral squamous cell carcinoma (OSCC).

METHODS

This study was performed retrospectively on anonymous forty paraffin embedded specimens diagnosed with a primary OSCC. Sections were prepared for p53 immunohistochemical staining and FISH technique evaluation.

RESULTS

All studied cases showed a positive nuclear staining with different indices for the p53 protein. Furthermore, statistical analysis showed a significant difference between all histological types of OSCC. In term of P53 immunoreactivity well differentiated OSCC showed the highest, whereas poorly differentiated showed weakest. Regarding chromosome 17 aberrations and p53 gene mutations, Spearman correlation test revealed a statistical significant positive correlation between chromosome 17 abnormalities and p53 gene mutations as well as with the immunohistochemical expression of p53 proteins. Moreover, the positive association between p53 gene mutations and the expression of p53 protein was statistically significant.

CONCLUSION

In the light of the previous findings, we concluded that numerical aberrations of chromosome 17 and p53 gene mutations as well as expression of p53 protein have enormous influence on various cellular processes including differentiation and carcinogenesis. Such knowledge provides an easy and simplified approach to prognosis predilection for OSCC.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2015_232 .