Epithelial p53 gene expression and mutational analysis, combined with growth fraction assessment, in oral lichen planus

A Molecular Hypothesis on Malignant Transformation of Oral Lichen Planus: A Systematic Review and Meta-Analysis of Cancer Hallmarks Expression in This Oral Potentially Malignant Disorder

We aimed to qualitatively and quantitatively analyze, through a systematic review and meta-analysis, the current evidence on the differential expression of the hallmarks of cancer in oral lichen planus (OLP) samples, in order to know the earliest molecular mechanisms that could be involved in the malignant transformation of this oral potentially malignant disorder. We searched MEDLINE/PubMed, Embase, Web of Science, and Scopus for studies published before November 2023. We evaluated the methodological quality of studies and carried out meta-analyses to fulfill our objectives. Inclusion criteria were met by 110 primary-level studies, with 7065 OLP samples, in which the expression of 104 biomarkers were analyzed through immunohistochemistry. Most OLP samples showed sustained cell proliferation signaling (65.48%, 95%CI = 51.87-78.02), anti-apoptotic pathways (55.93%, 95%CI = 35.99-75.0), genome instability (48.44%, 95%CI = 13.54-84.19), and tumor-promoting inflammation events (83.10%, 95%CI = 73.93-90.74). Concurrently, OLP samples also harbored tumor growth suppressor mechanisms (64.00%, 95%CI = 53.27-74.12). In conclusion, current evidence indicates that molecular mechanisms promoting hyperproliferative signaling, an antiapoptotic state with genomic instability, and an escape of epithelial cells from immune destruction, are developed in LP-affected oral mucosa. It is plausible that these events are due to the actions exerted by the chronic inflammatory infiltrate. Malignant transformation appears to be prevented by tumor suppressor genes, which showed consistent upregulation in OLP samples.

Evaluation of polymorphism of P53 protein codon 72 in oral lichen planus by PCR technique

Background. Our research was aimed to study p53 protein codon 72 polymorphism, a single base pair change of either arginine (Arg; CGC) or proline (Pro; CCC) that creates 3 distinct genotypes in reticular oral lichen planus (OLP) in comparison to oral SCC which is the most common oral mucosal malignancy as positive control and inflammatory fibrous hyperplasia (IFH) lesion as negative control.

Methods. Seventy paraffin-embedded tissue samples (30 OLP, 20 OSCC and 20 IFH) were studied. DNA was purified and amplified using allele-specific polymerase chain reaction to detect polymorphism. The final amplified products were identified using gel electrophoresis. Data were analyzed using chi-squared test and odds ratio.

Results. The mean ages in the OLP, OSCC and IFH groups were 43.28, 58.2 and 53.47 years, respectively, with significant differences. There were no significant differences in gender between the three groups (P=0.413); however, the differences in genotypes and alleles were significant between the three groups (P=0.021 and P=0.030, respectively). By considering IFH as a reference, the frequency of proline allele in OLP and OSCC was significantly higher than that of arginine allele (P=0.015 and P=0.028, respectively). In addition, by considering OSCC as a reference and at P=1, there were no significant differences in the frequencies of alleles between OSCC and OLP.

Conclusion. The results might indicate the premalignant potential of OLP, and such polymorphism might be a genetic predisposing factor for conversion of OLP to OSCC. In addition, in the subjects evaluated the proline allele was considered a risk factor.

Identification of potential therapeutic target genes, key miRNAs and mechanisms in oral lichen planus by bioinformatics analysis

The study aimed to identify the potential target genes and key miRNAs as well as to explore the underlying mechanisms in the pathogenesis of oral lichen planus (OLP) by bioinformatics analysis. The microarray data of GSE38617 were downloaded from Gene Expression Omnibus (GEO) database. A total of 7 OLP and 7 normal samples were used to identify the differentially expressed genes (DEGs) and miRNAs. The DEGs were then performed functional enrichment analyses. Furthermore, DEG-miRNA network and miRNA-function network were constructed by Cytoscape software. Total 1758 DEGs (598 up- and 1160 down-regulated genes) and 40 miRNAs (17 up- and 23 down-regulated miRNAs) were selected. The up-regulated genes were related to nuclear factor-Kappa B (NF-κB) signaling pathway, while down-regulated genes were mainly enriched in the function of ribosome. Tumor necrosis factor (TNF), caspase recruitment domain family, member 11 (CARD11) and mitochondrial ribosomal protein (MRP) genes were identified in these functions. In addition, miR-302 was a hub node in DEG-miRNA network and regulated cyclin D1 (CCND1). MiR-548a-2 was the key miRNA in miRNA-function network by regulating multiple functions including ribosomal function. The NF-κB signaling pathway and ribosome function may be the pathogenic mechanisms of OLP. The genes such as TNF, CARD11, MRP genes and CCND1 may be potential therapeutic target genes in OLP. MiR-548a-2 and miR-302 may play important roles in OLP development.

P53 and bcl-2 immunoexpression in patients with oral lichen planus and oral squamous cell carcinoma

OBJECTIVE

The aim of this study was to determine by immunohistochemistry the presence and significance of p53 and bcl-2 proteins in oral lichen planus (OLP) and oral squamous cell carcinoma (OSCC).

STUDY DESIGN

We used 21 cases diagnosed as OLP 16 diagnosed as OSCC and four normal gingival biopsies taken from healthy patients were used as controls. Slides were processed for immunohistochemistry using anti-p53 and anti-bcl-2 monoclonal antibodies.

RESULTS

We found p53 immunoexpression in 71.4% OLP cases and 68.7% OSCC cases, with no immunoexpression in control cases. Bcl-2 was negative for all OLP and OSCC cases, and mild positivity was observed in normal tissue. We found significant correlation among p53 expression and OSCC malignancy.

CONCLUSIONS

Our results suggest that TP53 system mainly promotes a hyperproliferative state by cell cycle arrest of the OLP epithelial cells for repairing damaged DNA nor apoptosis and that anti-apoptotic action of bcl-2 is not important in this disease.

Oral lichen planus is a unique disease model for studying chronic inflammation and oral cancer

Oral lichen planus (OLP) is a chronic inflammatory disease, which has been defined by the World Health Organization as a potential precancerous condition, representing a generalized state associated with a significantly increased risk of oral cancer. We would like to put forward a hypothesis that inflammatory mediators such as cytokines and chemokines released from infiltrating T lymphocytes induce fundamental changes of proteins in oral epithelial cells, leading to the progression of OLP to oral squamous cell carcinoma (OSCC). These altered proteins can act as the key risk factors associated with the local microenvironment and development of OSCC. Identification of these proteins would add to our understanding of the connection between chronic inflammation and OSCC.

Role of TP53 in the progression of pre-malignant and malignant oral mucosal lesions. A follow-up study of 144 patients

BACKGROUND

Prediction of progression from pre-malignant oral mucosal lesions to malignancy, or recurrence of an existing oral squamous cell carcinoma (OSCC), is an important clinical problem in oral medicine.

METHODS

This study presents a follow-up of a study published in 2002. Samples from 54 patients with OSCC, 45 with oral lichen planus (OLP) and 45 with hyperkeratosis (clinically leukoplakia), diagnosed between 1987 and 1996, were analysed for TP53 protein expression and TP53 mutation. Follow-up was 11-17 years for OSCC (mean 13.3), 12-22 years for OLP (mean 15.9) and 12-17 years for hyperkeratosis (mean 14.5).

RESULTS

Of the 54 OSCC patients, 28 experienced recurrent disease, 21 died of OSCC, 22 died of other causes. Of the 14 OSCC patients with mutated TP53 (n = 11), the cancer recurred in eight (57%) and in 20/39 (51%) without mutation. Expression of TP53 protein was significantly associated with reduced overall survival. Among OLP patients, nine were TP53-mutated out of 31 tested. One TP53-mutated OLP patient developed OSCC in a different site. Of the hyperkeratosis patients, three were mutated of 22 tested. One hyperkeratosis patient (non-mutated) developed OSCC in the same site.

CONCLUSION

TP53 mutations can exist in benign oral mucosal lesions for many years without progression to malignancy. No association was found between TP53 protein expression or TP53 mutation and recurrence of OSCC or disease-related survival. Overall survival was reduced in patients with positive TP53 protein expression.

Ultraviolet A within sunlight induces mutations in the epidermal basal layer of engineered human skin

The ultraviolet B (UVB) waveband within sunlight is an important carcinogen; however, UVA is also likely to be involved. By ascribing mutations to being either UVB or UVA induced, we have previously shown that human skin cancers contain similar numbers of UVB- and UVA-induced mutations, and, importantly, the UVA mutations were at the base of the epidermis of the tumors. To determine whether these mutations occurred in response to UV, we exposed engineered human skin (EHS) to UVA, UVB, or a mixture that resembled sunlight, and then detected mutations by both denaturing high-performance liquid chromatography and DNA sequencing. EHS resembles human skin, modeling differential waveband penetration to the basal, dividing keratinocytes. We administered only four low doses of UV exposure. Both UVA and UVB induced p53 mutations in irradiated EHS, suggesting that sunlight doses that are achievable during normal daily activities are mutagenic. UVA- but not UVB-induced mutations predominated in the basal epidermis that contains dividing keratinocytes and are thought to give rise to skin tumors. These studies indicate that both UVA and UVB at physiological doses are mutagenic to keratinocytes in EHS.

A role for the substance P/NK-1 receptor complex in cell proliferation and apoptosis in oral lichen planus

OBJECTIVES

To determine whether substance P (SP) and NK-1 receptor (NK-1R) are expressed in oral lichen planus (OLP) and are related to cell proliferation and apoptosis in this disease.

MATERIAL AND METHODS

Tissue samples from 50 OLP patients and 26 healthy controls were studied. Immunohistochemistry was performed with anti-SP, anti-NK-1R, anti-ki-67 and anti-caspase-3 monoclonal antibodies and the clinical and pathological data of the OLP patients were evaluated.

RESULTS

With the exception of NK-1R expression in epithelial cell membrane and cytoplasm, all markers were more frequently present in OLP patients than in controls (P < 0.05). Higher cytoplasmatic expression of NK-1R was associated with higher epithelial expression of caspase-3 (P < 0.05). Higher epithelial expression of NK-1R and SP was associated with higher suprabasal and basal epithelial expression of ki-67 (P < 0.05 and P < 0.005, respectively).

CONCLUSIONS

Actions of the SP/NK-1R complex may contribute to the immune disorder underlying OLP and trigger stimuli to induce cell proliferation. These results indicate that this complex might play a role in the malignant transformation of OLP.

Oral lichen planus: controversies surrounding malignant transformation

Studies of the malignant potential of oral lichen planus (OLP) have been hampered by inconsistencies in the diagnostic criteria used for OLP, the criteria adopted to identify a true case of malignant transformation in OLP, the risk factors for malignant transformation and the optimum management of patients to ensure the early diagnosis of transformation. Consensus remains elusive, and leading workers in this field have recently published conflicting reports on the malignant potential of OLP and on the important question of the advisability of excluding patients with epithelial dysplasia or a tobacco habit from studies on this issue. The present review outlines these debates and proposes a possible a molecular basis for the malignant transformation in this disease.

Significance of liquefaction degeneration in oral lichen planus: a study of its relationship with apoptosis and cell cycle arrest markers

OBJECTIVE

To assess the utility of liquefaction degeneration as a marker of apoptosis in oral lichen planus (OLP).

METHODS

TdT-mediated dUTP-biotin nick-end labelling (TUNEL) assay and immunohistochemical methods were used to detect p21 proteins and the active form of caspase 3 in 32 tissue samples of oral mucosa with OLP and 20 samples of normal oral mucosa.

RESULTS

Liquefaction degeneration was moderate or intense in 27.5% (n=8) and slight in 72.4% (n=21) of OLP samples. There was low expression of apoptosis markers (TUNEL, active caspase 3 form), which was not significantly associated with liquefaction degeneration of the basal cell layer. Basal and suprabasal expression of p21 was significantly more frequent in samples with more intense liquefaction degeneration of basal cells (P<0.01).

CONCLUSIONS

Our results demonstrate that liquefaction degeneration, as a morphological expression of T lymphocyte attack, does not unequivocally indicate apoptosis. Attacked basal cells more frequently respond with cell-cycle arrest or senescence than with apoptosis.

Prevalence of stratified epithelium-specific antinuclear antibodies in 138 patients with lichen planus

BACKGROUND

Antibodies to stratified epithelia characterize chronic ulcerative stomatitis, an entity that very closely resembles erosive lichen planus both clinically and histologically. These antibodies are directed against a 70-kd antigen.

OBJECTIVE

Our aim was to verify whether antibodies to stratified epithelia are present in patients with common lichen planus.

PATIENTS AND METHODS

One hundred thirty-eight patients with various forms of lichen planus were studied. Indirect immunofluorescence was performed on both monkey esophagus and HEp2-2000 cells. Immunoblotting was done with cultured keratinocytes used as the source antigen.

RESULTS

Nineteen patients had antibodies to stratified epithelia (in 9 directed against an antigen of 70 kd). Forty-eight patients had circulating antibodies detected by indirect immunofluorescence on both monkey esophagus and HEp2-2000 cells (in 7 directed against an antigen of 70 kd). Indirect immunofluorescence was positive only on HEp2-2000 cells in 21 patients. Indirect immunofluorescence was negative in 50 patients on both HEp2-2000 cells and monkey esophagus. None of the last 71 patients had antibodies directed to an antigen of 70 kd.

LIMITATIONS

This is a serological study; results from direct immunofluorescence studies would be interesting.

CONCLUSION

Antibodies to stratified epithelia directed to an antigen of 70 kd are not exclusive to chronic ulcerative stomatitis, but are also present in some patients with lichen planus.

Expression of novel p53 isoforms in oral lichen planus

Oral 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.

Cell cycle regulating mechanisms in oral lichen planus: Molecular bases in epithelium predisposed to malignant transformation

OBJECTIVE

Expression of p53, p21, ki-67, Bcl-2 and caspase-3 proteins in oral lichen planus (OLP) was studied to investigate cell cycle regulation mechanisms in this disease.

MATERIAL AND METHODS

Oral biopsies were obtained from 51 patients with OLP and 26 controls for immunohistochemical analysis (peroxidase antiperoxidase) to quantify expression of the proteins under study (-: 0%, +: <10%, ++: 10-25%, +++: 26-50%, ++++: >50% positive cells).

RESULTS

Basal expression of caspase-3 was negative in 22 cases (46.8%) and positive in <10% of basal cells in 22 cases (46.8%); caspase-3 expression in inflammatory infiltrate was negative in 22 cases (46.8%) and positive in <10% of lymphocytes in 20 cases (42.5%). Basal expression of Bcl-2 was negative in 35 cases (74.5%); Bcl-2 was expressed in inflammatory infiltrate in 34 cases (72.3%) and was positive in <25% of lymphocytes in 14 of these (29.7%). Basal expression of p53 and p21 was positive in 32 (67.9%) and 23 (48.8%) cases, respectively. Basal expression of ki-67 was positive in 45 cases (95.7%), of which 20 (42.5%) showed positivity in >25% of cells; ki-67 was expressed in inflammatory infiltrate in 23 cases (48.9%). Significant associations were found between basal expressions of p53 and ki-67 (p<0.001) and between Bcl-2 expression in infiltrate and basal expression of ki-67 (p<0.001). No association was observed between basal expressions of p53 and caspase-3 (p=0.08). Bcl-2 expression in infiltrate and basal expression of ki-67 were independently associated with presence of OLP.

CONCLUSIONS

Epithelial cells in OLP do not preferentially develop apoptosis but rather cycle arrest or an increased proliferation rate, which may create a suitable substrate for malignant transformation.

Evaluation of proliferative potential in oral lichen planus and oral lichenoid lesions using immunohistochemical expression of p53 and Ki67

A small proportion of cases diagnosed as oral lichen planus (OLP) and oral lichenoid lesions (OLL) can undergo malignant transformation. Some authors, however, stand that only dysplastic lichenoid lesions, not true OLP, have the potential to progress to oral squamous cell carcinoma (OSCC). The histologic diagnosis is a subjective resource and is not always accurate in differentiating OLP from OLL. Thus, this study attempted to evaluate the malignant potential of lesions diagnosed as OLP and as OLL without dysplasia. The Streptavidin-biotin method of immunohistochemistry was used for the staining with p53 and Ki67 in 22 cases of OLP and 27 cases diagnosed as OLL. Ki67 immunoexpression was not statistically different between OLP and OLL (p = 0.353), but, p53 staining showed a significant contrast (p = 0.036). A higher average of staining was detected in the group of OLP. The study showed that apparently a diagnosis of OLP or OLL makes no difference for the patient regarding malignant transformation, although in OLP p53 showed a higher index of expression, probably related to the intensity of inflammatory infiltrate.

Higher expressions of p53 and proliferating cell nuclear antigen (PCNA) in atrophic oral lichen planus and patients with areca quid chewing

OBJECTIVE

The aim of the study was to examine the expressions of p53 and proliferating cell nuclear antigen (PCNA) in oral lichen planus (OLP) in relation to its clinical behavior and the patients' oral habits.

STUDY DESIGN

Immunohistochemical study was carried out to investigate the expressions of p53 and PCNA in 56 OLP specimens. The results were correlated with the clinical behavior of the disease and the patients' oral habits. The expression rates were further compared with those of normal oral mucosa (NOM), epithelial hyperkeratosis (EH), epithelial dysplasia (ED), and squamous cell carcinoma (SCC).

RESULTS

The staining rate of p53 (28.6%) and PCNA labeling index (LI) (27.6 +/- 8.8%) in OLP were similar to those in EH ( P = .868, .074, respectively), but higher than those of NOM and lower than those of ED and SCC (all P < .05). In OLP, no significant correlations were found between p53 or PCNA expression and the patients' age, gender, lesion duration, location, size, number of site, presence of pain, presence of local irritant, and the habits of alcohol drinking and cigarette smoking (all P > .05). In addition, the mean PCNA LI of p53+ cases was close to that of p53- cases (P = .38). However, the staining rate of p53 in OLP was higher in areca quid (AQ) chewers compared to abstainers (P = .001), and the mean PCNA LI in atrophic cases was higher than that in hypertrophic cases (P = .029). Interestingly, the staining rate of p53 and mean PCNA LI were significantly increased in AQ chewers with atrophic OLP (100%, 36.7% +/- 9.0%, respectively), which were similar to those in ED and SCC (all P > .05).

CONCLUSIONS

Although this study could not confirm the precancerous nature of OLP by the relatively low p53 and PCNA expression, the results do suggest that atrophic form OLP and patients with AQ chewing habit may have a higher disease activity in view of higher expression rates of p53 and PCNA in the lesions.

Apoptosis and cell cycle arrest in oral lichen planus Hypothesis on their possible influence on its malignant transformation

The quantitative importance of cell cycle arrest and apoptosis mechanisms in oral lichen planus (OLP) was analysed in order to assess the cell response to T lymphocyte aggression and establish a hypothesis on the influence of these phenomena in the malignant transformation process. The TUNEL assay and immunohistochemical methods were used to detect caspase-3, bax, and p21 in 32 tissue samples of oral mucosa with OLP and in 20 samples of normal oral mucosa. Positivity for TUNEL, caspase-3 and p21 was significantly more frequent in cases than in controls (p<0.001). Both TUNEL and caspase-3 positivity was significantly greater in the basal versus suprabasal layer (p=0.004 and 0.052, respectively). The basal and suprabasal expression of p21 was significantly higher in cases with a more intense liquefaction degeneration (p<0.01). There was no significant difference in basal expression of bax between cases and controls. The quantitative importance of apoptosis was small in OLP. Epithelial cells attacked in OLP have a very low response to apoptosis and cell cycle arrest mechanisms, which may produce an epithelial substrate that favours malignant transformation.

Analysis of p53 and bcl-2 protein expression in the non-tumorigenic, pretumorigenic, and tumorigenic keratinocytic hyperproliferative lesions

BACKGROUND

The hyperproliferative keratinocytic lesions encompass a wide range of non-tumorigenic, pretumorigenic, and tumorigenic conditions. The aim of this work was to examine the expression patterns of apoptosis-linked molecules (bcl-2 and p53) in these lesions.

METHODS

Immunoperoxidase staining methods were applied to analyze p53 and bcl-2 protein expression in a total of 66 cases, including 12 squamous cell carcinomas (both in situ and invasive SCC), 11 actinic keratoses (AK), 13 psoriasis vulgaris (PV), eight verruca vulgaris (VV), six chronic dermatitis (CD), five seborrheic keratosis (SK), four lichen planus (LP), three epidermodysplasia verruciformis (EDV), two condyloma acuminata (CA), two lichen simplex chronicus (LSC), and 10 specimens from normal skin.

RESULTS

As compared to normal skin (0.70 +/- 0.26), the bcl-2 average weighted scores in the non-tumorigenic (0.76 +/- 0.16), pretumorigenic (1.45 +/- 0.28), and tumorigenic lesions (2.83 +/- 0.50 and 2.92 +/- 0.50 for in situ and invasive SCC, respectively) showed significant up-regulation (p = 0.001). In the non-tumorigenic lesions, the bcl-2 expression values decreased in the following order: SK > EDV > CD > LP > CA > PV > VV (1.40 +/- 0.24 > 1.33 +/- 0.67 > 0.83 +/- 0.40 > 0.67 +/- 0.21 > 0.50 +/- 0.20 > 0.46 +/- 0.22 > 0.13 +/- 0.01, respectively). As compared to normal skin (1.10 +/- 0.23), the p53 average weighted scores in the non-tumorigenic (1.86 +/- 0.18), pretumorigenic (3.64 +/- 0.53), and tumorigenic lesions (5.00 +/- 1.00 and 5.08 +/- 0.86 for in situ and invasive SCC, respectively) showed significant up-regulation (p = 0.021). In the non-tumorigenic lesions, p53 average weighted scores decreased in the following order: SK > PV > CA > LP > CD > VV > EDV (3.20 +/- 0.49 > 2.38 +/- 0.27 > 2.0 +/- 0.0 > 1.83 +/- 0.48 > 1.0 +/- 0.37 > 1.0 +/- 0.33 > 1.0 +/- 0.0, respectively). There was a positive correlation between bcl-2 and p53 protein expression in normal skin (r = 0.966, p = 0.0001), non-tumorigenic (r = 0.775, p = 0.0001), pretumorigenic (r = 0.830, p = 0.001), and tumorigenic lesions (r = 0.757, p = 0.003).

CONCLUSIONS

Bcl-2 and p53 proteins are altered in the keratinocytic hyperproliferative lesions. Determination of whether these alterations reflect underlying gene mutations will require further investigations.

The basal layer in human squamous tumors harbors more UVA than UVB fingerprint mutations: a role for UVA in human skin carcinogenesis

We hypothesized that a substantial portion of the mutagenic alterations produced in the basal layer of human skin by sunlight are induced by wavelengths in the UVA range. Using laser capture microdissection we examined separately basal and suprabasal keratinocytes from human skin squamous cell carcinomas and premalignant solar keratosis for both UVA- and UVB-induced adduct formation and signature mutations. We found that UVA fingerprint mutations were detectable in human skin squamous cell carcinomas and solar keratosis, mostly in the basal germinative layer, which contrasted with a predominantly suprabasal localization of UVB fingerprint mutations in these lesions. The epidermal layer bias was confirmed by immunohistochemical analyses with a superficial localization of cyclobutane thymine dimers contrasting with the localization of 8-hydroxy-2'-deoxyguanine adducts to the basal epithelial layers. If unrepaired, these adducts may lead to fixed genomic mutations. The basal location of UVA-rather than UVB-induced DNA damage suggests that longer-wavelength UVR is an important carcinogen in the stem cell compartment of the skin. Given the traditional emphasis on UVB, these results may have profound implications for future public health initiatives for skin cancer prevention.

Epithelial cell proliferation in oral lichen planus

Although the pathogenesis of oral lichen planus (OLP) is not clear, a small proportion of cases with OLP are reported to transform to cancer. We examined the epithelial cell proliferation status of OLP to relate the labelling index to microscopic features surveyed routinely in pathology. Mucosal biopsies obtained from 44 cases diagnosed with OLP with an intact oral epithelium and 10 normal control specimens from Japanese subjects were immunohistochemically stained with MIB and p53 antibodies. The Ki67 labelling index (LI) was significantly higher in OLP compared with normal controls. A particularly large number of OLP lesions (64%) were p53 positive. No association was, however, found with p53 expression and the Ki67 LI. Atrophic and flat epithelia had a quantitatively higher LI, which did not significantly differ from acanthotic biopsies. Increased cell proliferation in OLP is likely to be a secondary phenomenon due to the damage inflicted on keratinocytes by infiltrating mononuclear cells in the submucosa.

Telomerase activity detected in oral lichen planus by RNA in situ hybridisation: not a marker for malignant transformation

BACKGROUND

Oral lichen planus (OLP) is a chronic inflammatory condition. Clinically, it is characterised by the presence of a white lace-like lesion on the buccal mucosa, tongue, and gingivae, with erosions and ulceration. The World Health Organisation considers OLP to be a premalignant condition.

AIMS

To investigate expression of the telomerase RNA component (hTR) in OLP compared with normal control buccal mucosa and to assess the possibility of using hTR expression as a marker for malignant transformation in OLP.

METHODS

hTR expression was analysed in 40 cases of OLP and 18 normal control buccal mucosa samples using an RNA in situ hybridisation approach.

RESULTS

Strong hTR RNA expression was seen in the basal, suprabasal, and to a lesser extent in the upper epithelial layers in 36 of the 40 OLP lesions examined. Infiltrating subepithelial lymphocytes in OLP were also shown to express hTR RNA. Weak hTR RNA expression was seen in seven of the 18 normal control buccal mucosa specimens, with expression confined exclusively to the basal layer of the epithelium and absent in the suprabasal and upper layers.

CONCLUSION

The telomerase RNA component hTR is found to be highly expressed in the epithelium of non-dysplastic OLP lesions. It is possible that this high expression is related to the increased cellular proliferation seen in OLP lesions rather than being an indicator of susceptibility to malignancy. Thus, hTR RNA expression may not be a suitable marker for predicting malignant transformation in OLP.

Effect of nifedipine on the expression of p53 protein in rat gingiva

The aim of the present study was to determine the profile of p53 protein expression in gingival tissues after treatment with nifedipine in rats. Rats were treated daily by gastric intubation with or without DMSO alone or DMSO-dissolved nifedipine at concentrations of 15, 30 or 60 mg/kg body weight for 1, 3 or 6 week(s). Gingival width and height were measured macroscopically. Monoclonal antibodies recognizing both wild-type and mutant p53 protein were applied on paraffin-embedded gingival sections using microwave pretreatment and immunohistochemical methods. The gingival width and height were increased in the animals treated with nifedipine at concentrations of 30 and 60 mg/kg body weight. Increased gingival width and height were already seen in the animals treated with 60 mg of nifedipine for 1 week, whereas treatments with 30 mg of nifedipine resulted in increased gingival width and height after treatment for at least 3 weeks. The expression of p53 protein was elevated in the animals treated with 30 or 60 mg of nifedipine. Treatments with nifedipine at the concentration of 60 mg/kg body weight for 1 week induced the expression of p53 protein in the gingival tissues. Treatment with nifedipine in rats led to the inducement of gingival hyperplasia and increase in the numbers of p53-positive gingival epithelial cells by a dose and frequency dependent mechanism, suggesting that p53 protein may play a crucial role in the regulation of nifedipine-induced gingival hyperplasia.

Oral lichen planus has a high rate of TP53 mutations. A study of oral mucosa in icelanD

Oral squamous cell carcinoma (OSCC) is a world-wide health problem. In addition to external exposure (smoking and alcohol), certain oral lesions may increase the risk of oral cancer (e.g. leukoplakia, erythroplakia, and oral lichen planus). TP53 has been implicated in OSCC, but there are limited studies of mutations in premalignant oral lesions. In this study, 55 samples from OSCC, 47 from hyperkeratotic (HK) oral mucosa, clinically diagnosed as white patches, 48 samples from oral lichen planus (OLP), and 12 biopsies from normal oral mucosa were studied immunohistochemically for expression of TP53 protein. From all the carcinoma samples and selected non-malignant samples showing moderate or strong TP53 protein expression, malignant cells or TP53-positive nuclei were microdissected and screened for mutations in exons 5-8 by constant denaturation gel electrophoresis. Moderate to strong TP53 protein staining was seen in 56% of OSCC, 32% of OLP but only in 13% of HK. All OLP samples showed a characteristic pattern of positive nuclei confined to the basal layer, whereas TP53 staining was seen in suprabasal nuclei in HK. Mutation rate was 11 out of 52 for OSCC, three out of 20 tested for HK and, remarkably, nine out 27 tested for OLP. There was no correlation between TP53 protein staining and TP53 mutations. No associations were found with anatomical sites or disease progression. The unexpectedly high mutation rate of OLP might explain the premalignant potential of this lesion.

Cell proliferation activity and the expression of cell cycle regulatory proteins in oral lichen planus

BACKGROUND

In oral lichen planus (OLP), destruction of the basal cell layer, which is one of the characteristic histological features, is seen and many changes in cell proliferation, cell repair and cell death occur in the injured mucosal epithelium.

METHODS

We studied mucosal tissues from 19 patients of OLP and 10 controls, with immunohistochemistry for Ki-67, p53, cyclin dependent kinase inhibitors (CDKI) and cyclins. Mitotic count was calculated. TUNEL assay was also performed for evaluation of apoptotic cell death.

RESULTS

Mitotic count, Ki-67 and cyclin D1 labeling indices in the basal and parabasal layers of OLP mucosa were elevated in comparison with those of controls. p53, p21Cip1 and TUNEL indices of OLP mucosa were also increased.

CONCLUSIONS

These complex changes, which concomitantly occur in the injured mucosal epithelium, could contribute to the development and maintenance of characteristic mucosal epithelial architectures seen in OLP.