Accumulation of the p53 tumor-suppressor gene product in oral leukoplakia

Biomarkers of malignant transformation in oral leukoplakia: from bench to bedside

Oral leukoplakia is a common precursor lesion of oral squamous cell carcinoma, which indicates a high potential of malignancy. The malignant transformation of oral leukoplakia seriously affects patient survival and quality of life; however, it is difficult to identify oral leukoplakia patients who will develop carcinoma because no biomarker exists to predict malignant transformation for effective clinical management. As a major problem in the field of head and neck pathologies, it is imperative to identify biomarkers of malignant transformation in oral leukoplakia. In this review, we discuss the potential biomarkers of malignant transformation reported in the literature and explore the translational probabilities from bench to bedside. Although no single biomarker has yet been applied in the clinical setting, profiling for genomic instability might be a promising adjunct.

A Systematic Review of Oral Biopsies, Sample Types, and Detection Techniques Applied in Relation to Oral Cancer Detection

Background: Early identification of the stage of oral cancer development can lead to better treatment outcomes and avoid malignant transformation. Therefore, this review aims to provide a comprehensive overview that describes the development of standardized procedures for oral sample collection, characterization, and molecular risk assessment. This can help investigators to choose the appropriate sampling method and downstream analyses for different purposes. Methods: This systematic review was conducted according to the PRISMA guidelines. Using both PubMed and Web of Science databases, four independent authors conducted a literature search between 15 and 21 June 2021. We used key search terms to broaden the search for studies. Non-conforming articles were removed using an EndNote-based and manual approach. Reviewers used a designed form to extract data. Results: This review included a total of 3574 records, after eliminating duplicate articles and excluding papers that did not meet the inclusion criteria. Finally, 202 articles were included in this review. We summarized the sampling methods, biopsy samples, and downstream analysis. The biopsy techniques were classified into tissue and liquid biopsy. The common sequential analysis of tissue biopsy includes histopathological examination such as H&E or IHC to identify various pathogenic features. Meanwhile, liquid samples such as saliva, blood, and urine are analyzed for the purpose of screening to detect mutations in cancer. Commonly used technologies are PCR, RT-PCR, high-throughput sequencing, and metabolomic analysis. Conclusions: Currently, tissue biopsies provide increased diagnostic value compared to liquid biopsy. However, the minimal invasiveness and convenience of liquid biopsy make it a suitable method for mass screening and eventual clinical adoption. The analysis of samples includes histological and molecular analysis. Metabolite analysis is rising but remains scarce.

Clinical, pathological, cellular and molecular lesions caused by oral smokeless tobacco - a review

While carcinogenicity of smokeless tobacco (ST) to humans is well established the oral lesions that precede development of cancer are less well characterized. The clinical appearances of ST-associated lesions are variable. Epidemiological studies show a strong significant association of risk with chronic daily use but population differences are noted because of various commercial products in use. Morphological features observed are some what different to oral lesions caused by smoking and oral dysplasia in ST-associated lesions is less common. Effects of ST on oral keratinocytes observed in vitro include alterations in cell proliferation, apoptosis and activation of inflammatory markers. Genetic aberrations caused by ST include activation of ras, uncommon in smokers but mutational hot spots in p53 encountered are similar to those in smokers.

Immunohistochemical study of syndecan-1 down-regulation and the expression of p53 protein or Ki-67 antigen in oral leukoplakia with or without epithelial dysplasia

BACKGROUND

Leukoplakia is an oral pre-cancerous lesion that sometimes develops into squamous cell carcinoma. Therefore, leukoplakia with epithelial dysplasia is useful for studying carcinogenesis at the cellular level. The purpose of this study was to evaluate a potential association between the loss of syndecan-1 expression and the expression of p53 protein and Ki-67 antigen, and to identify reliable markers for predicting malignant changes in oral leukoplakia with epithelial dysplasia.

METHODS

Changes in the expression of syndecan-1, p53, and Ki-67 were examined immunohistochemically in 43 cases of oral leukoplakia with or without epithelial dysplasia. The subjects were categorized as: none, 13 cases; mild dysplasia, 5 cases; moderate dysplasia, 17 cases; and severe dysplasia, 8 cases. The expression of these molecules in normal oral epithelia (22 cases) was also investigated.

RESULTS

Strong syndecan-1 expression was observed on the surface of keratinocytes in normal epithelium. Immunopositivity was lost gradually as the extent of epithelial dysplasia increased. In normal epithelium, p53 and Ki-67 appeared mainly in the basal cell layer, while they were more widely distributed in leukoplakia. Specifically, significant changes were observed in the labeling index of p53 and Ki-67 in leukoplakia as epithelial dysplasia progressed from mild to moderate or severe.

CONCLUSION

Our results reveal that overexpression of p53 protein and Ki-67 antigen, and down-regulation of syndecan-1 expression in the lower part of the epithelium, are associated with dysplastic changes. Therefore, the down-regulation of syndecan-1 expression may be the most important reliable marker for dysplastic changes.

Proliferation and differentiation markers in snuff-induced oral mucosal lesions

BACKGROUND

Regular use of snuff is known to cause whitish oral mucosal lesions of variable severity at the usual quid placement site. The main aim of this study was to elucidate cellular mechanisms involved in snuff-induced epithelial changes.

METHODS

Expression patterns for markers of cell proliferation (PCNA, Ki-67), cell cycle regulation (p53, p21), keratin changes (pankeratin, CK18, CK19), cell stress (HSP 70) and collagen type IV in 14 snuff-induced oral mucosal lesions and 12 control samples were analyzed by immunohistochemistry (IHC).

RESULTS

On light microscopy, all snuff-induced lesions were characterized by a hyperkeratinized and thickened epithelium. Some vacuolized cells, markers of cell degeneration, were frequently seen (in 9/14 of the samples) in the superficial layers in epithelia. Expression of PCNA and Ki-67 was found in a statistically significantly fewer cells in snuff-induced lesions (P < 0.001) than in the controls. This indicates that epithelia in snuff-induced lesions are not thickened as a result of increased cellular proliferation, but by protracted turnover of differentiating cells. Of cell cycle markers, p21 was found be up-regulated in 4/14 snuff-induced lesions, probably by p53-independent pathways. Only two snuff-induced lesions showed p53 positivity. However, the number of stained cells with p53 and p21 was not statistically different from that in controls. Expression of CK18, but not any alterations in CK19 expression, was seen in 5 of 14 snuff-induced lesions. Snuff also seems to stimulate the expression of collagen type IV, possibly by basal cells, as indicated by the thickened staining of the basal lamina.

CONCLUSIONS

The findings of this study showing suppressed cellular proliferation and infrequent p53 dysfunction in snuff lesions may partly explain why dysplastic changes are seldom seen in mucosal lesions induced by the Scandinavian type of snuff.

p53 expression in oral precancer as a marker for malignant potential

The potential of p53 protein expression as a marker for determining which oral precancerous lesions may transform to malignancy with time was assessed. We compared the p53 expression in archival formalin-fixed, paraffin-embedded tissues from 22 baseline biopsies of precancerous lesions that transformed to cancer in 4-25 years against that in 68 similar lesions that did not transform over the same time period. Twenty-nine percent of precancers that transformed were p53-positive at baseline, compared to 31% of the biopsies that did not transform to malignancy. When examined by immunohistochemical methods p53 expression failed to detect potential malignant status of oral precancer. Non-specificity of the assay may account for this result but overexpression of p53 due to DNA damage by tobacco/betel-quid in non-progressive lesions needs further study. Nine precancerous lesions became p53-immunoreactive from precancer to cancer. This may suggest p53 overexpression peaks close to the time of transition from precancer to cancer rather than early in the natural history of oral precancer.

Identification of p53 and human papilloma virus in Schneiderian papillomas

Schneiderian papilloma of the nose is an unusual neoplasm with the propensity for local tissue destruction, recurrence, and malignant degeneration. Human papilloma virus (HPV) is related to a subset of sinonasal papillomas and has been implicated in the pathogenesis of cancer by interaction with the host p53 protein. Detection of p53 and HPV could be clinically useful as tumor markers for lesions with oncogenic potential. Thirty specimens for p53 were studied and nine (30%) stained positive. HPV was detected in six (20%). In the presence of p53, an odds ratio for carcinoma was 1.19:1, or 19% higher than expected. In the presence of HPV the odds ratio for carcinoma was 11.5:1, or 11.5 times higher than expected. In the presence of HPV an odds ratio for finding an elevated amount of p53 was 2.2:1. The data support the hypothesis that HPV and p53 may interact in a novel manner and elevate the risk for neoplasia.

p53 expression above the basal cell layer in oral mucosa is an early event of malignant transformation and has predictive value for developing oral squamous cell carcinoma

Epithelial dysplasia is usually used to establish the prognosis of oral premalignant lesions. Its assessment, however, is subjective and does not always correctly predict the outcome of the lesions in terms of malignant transformation. Early molecular alteration(s) that dictate the development of cancer should be identified and used to evaluate oral premalignant lesions. In this context, alterations in the expression of p53 were investigated. Thirty-five oral premalignant lesions and 11 carcinomas that developed from them in a period of 16 years were investigated for p53 expression by immunohistochemistry. Normal oral mucosa from healthy individuals and oral benign lesions were used as controls. In benign lesions and normal mucosa, p53 staining, when present, was confined to the basal cell layer. Seven out of 35 (20 per cent) premalignant lesions showed p53 expression clearly above the basal cell layer and six of these (86 per cent) developed carcinomas. Suprabasal p53 expression was found in three lesions with no or mild dysplasia that developed carcinomas. All carcinomas derived from premalignant lesions with p53 suprabasal expression showed p53 expression in neoplastic cells. The combined use of histological parameters (presence of moderate or severe dysplasia) with p53 expression patterns (p53 staining above the basal cell layer) showed the highest sensitivity for the detection of lesions that progressed to carcinoma (91 per cent). When used individually, the p53 expression pattern showed higher specificity than assessment of dysplasia (96 per cent vs. 54 per cent) and higher positive predictive value (86 per cent vs. 44 per cent) for correct prediction of the malignant transformation of the lesions. The results suggest that clear expression of p53 above the basal cell layer is an early event in oral carcinogenesis and an indicator of a developing carcinoma, even preceding morphological tissue alterations. However, since immunohistochemistry cannot always detect changes in p53 expression in lesions preceding carcinoma, p53 immunohistochemical analysis is strongly recommended in conjunction with histological parameters, to increase the sensitivity of detection of cases that will progress to carcinoma.

p53 expression and p53 gene mutation in oral cancer and dysplasia

BACKGROUND

The aim of the current study was to examine the possible association of the p53 tumor suppressor gene with the development of oral cancer. We examined biopsy material from patients with oral squamous cell carcinoma for p53 protein expression and p53 mutations.

METHODS

Eighteen samples were analyzed. These comprised oral squamous cell carcinoma biopsy samples and oral dysplastic biopsy material taken from nine patients. An immunohistochemical technique was used to determine p53 protein expression. A direct sequencing technique was used to detect mutations in the p53 gene itself.

RESULTS

Overall seven of nine (77%) oral squamous cell carcinomas and seven of nine (77%) oral dysplastic lesions analyzed showed evidence of p53 protein over-expression. Mutations in exons 5 and 6 of the p53 gene were detected in five of nine (55%) oral squamous cell carcinomas and four of nine (44%) dysplastic lesions analyzed.

CONCLUSIONS

Both p53 protein over-expression and p53 mutations were noted in dysplastic oral lesions. Over-expression of the p53 protein and p53 gene mutations were not always coexistent, however, suggesting that gene mutation may be only one of the mechanisms responsible for stabilization of the p53 protein.

Patterns of p53 and Ki-67 protein expression in epithelial dysplasia from the floor of the mouth

Oral squamous cell carcinoma develops through a series of precancerous stages manifested at the microscopic level as epithelial dysplasia. Mutation of the p53 tumour suppressor gene is thought to be an important component of oral carcinogenesis. p53 regulates cell proliferation and DNA repair by inhibiting the cell cycle at G1/S; loss of p53 function may therefore lead to aberrant cell kinetics. To date, no studies have examined the relationship between p53 protein and alterations in cell kinetics in oral epithelial dysplasia from a single anatomical site. Serial sections were studied from 40 routinely processed biopsy specimens of epithelial dysplasia from the floor of the mouth. The expression of p53 protein was determined by immunohistochemistry and cell proliferation was studied by immunostaining for the cell cycle-dependent protein Ki-67. The number of positive cells per millimetre of basement membrane was determined using computer image analysis and compared with site-matched normal controls. The mean p53 labelling index (LI) in normal mucosa was low, 3.48 +/- 0.92 [mean +/- 95 per cent confidence interval (CI)], and increased sharply in the transition from mild (42.49 +/- 21.71) to moderate (104.86 +/- 51.39) epithelial dysplasia. The mean p53 LI for severe dysplasia was 119.09 +/- 56.50. Differences were also observed in the distribution of p53-positive cells between grades of dysplasia, with the development of compact p53-positive foci in severe dysplasia. Mean proliferative indices, as determined by Ki-67 expression, were significantly associated with grade of epithelial dysplasia. Furthermore, there was a significant correlation between p53 LI and Ki-67 score (r2 = 0.37, P = 0.01). It is concluded that altered p53 protein expression is probably an early event in oral carcinogenesis in the floor of the mouth and is associated with dysregulation of cell proliferation at this site.