Importance of proliferation markers in oral pathology

The significance of Epstein Barr virus (EBV) & DNA topoisomerase II alpha (DNA-Topo II alpha) immunoreactivity in normal oral mucosa, oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC)

Background

Head and neck cancer including oral cancer is considered to develop by accumulated genetic alterations and the major pathway is cancerization from lesions such as intraepithelial dysplasia in oral leukoplakia and erythroplakia. The relationship of proliferation markers with the grading of dysplasia is uncertain. The involvement of EBV in oral carcinogenesis is not fully understood.

Aim

The present study was designed to investigate the role of EBV and DNA Topoisomerase II∝ (DNA-Topo II∝) during oral carcinogenesis and to examine the prognostic significance of these protein expressions in OSCCs.

Methods

Using specific antibodies for EBV and DNA-Topo II∝, we examined protein expressions in archival lesion tissues from 16 patients with oral epithelial dysplasia, 22 oral squamous cell carcinoma and 20 normal oral mucosa by immunohistochemistry. Clinical information was obtained through the computerized retrospective database from the tumor registry.

Results

DNA-Topo II∝ was expressed in all examined specimens. Analysis of Variance ANOVA revealed highly significant difference (P < 0.01) in young aged labial tissues and significant (P ≤ 0.05) in gingival and not significant (P > 0.05) in inferior surface of tongue and in hard palatal tissues. Significant differences were observed between OEDs and NSE (P < 0.001) and SCCs and controls (P < 0.001), also, significant differences could be observed between SCCs and OEDs. DNA-Topo II∝ expression was significantly higher in tumors of low differentiation versus tumors of moderate and high differentiation (P < 0.001), DNA-Topo II∝ expression was correlated with age, tumor size, tumor stage, node metastasis and tumor differentiation, but not with gender and tumor site. None of normal squamous epithelium (NSE) expressed EBV. Heterogenous reactivity for EBV was observed through the series of dysplasia and squamous cell carcinoma. Its expression increased progressively with lymph node metastasis and low tumor differentiation, but no significant association could be observed with other clinicopathological parameters. EBV protein expression was increased with elevated Topo II-∝ LI in OEDs and OSCCs. A tendency to positive correlation between EBV and Topo II∝ expression was observed in OEDs but not in OSCCs.

Conclusion

EBV and DNA Topo II-αLI expression are possible indicators in oral carcinogenesis and may be valuable diagnostic and prognostic indices in oral carcinoma.

Immunohistochemical study on topoisomerase IIα, Ki-67 and cytokeratin-19 in oral lichen planus lesions

Oral lichen planus (OLP) is a chronic muco-cutaneous inflammatory disease defined as a precancerous condition. We determined the expression patterns of proliferation markers topoisomerase IIalpha (topo IIalpha) and Ki-67 and an intermediated filament protein cytokeratin-19 (CK-19) in atrophic OLP. These markers were selected because our recent microarray analysis indicated they might aid in identification of potentially malignant lesions. The expression patterns were correlated with the DNA content of these lesions shown to be useful in detection lesions at risk for malignant transformation of OLP. A series of 81 formalin-fixed, paraffin-embedded biopsies from 70 patients suffering from atrophic OLP were immunostained with monoclonal antibodies against topo IIalpha, Ki-67 and CK-19 using standard methods. Of the 70 patients, there were eight patients who had dysplastic changes in OLP lesions. During the follow-up, altogether five patients got cancer in the OLP area even though no dysplastic changes were present in the preceding lesion. On light microscopy, 500 cells were examined in the basal and parabasal epithelial layers of biopsy samples at 400x magnification. All biopsy samples were topo IIalpha positive and approximately 70% of the counted cells were positive. Strong staining of topo IIalpha was significantly correlated with dysplasia (P = 0.019), basal cell hyperplasia (P = 0.005) and ulceration (P = 0.008) in the samples. Ki-67 was expressed in all samples but only 36% of the cells were positive. CK-19 positivity was found in 29% of the specimens. Histological parameters were not related to either Ki-67 or CK-19. The comparison of the staining patterns with the DNA content of lesions showed that strongly stained cells with topo IIalpha were significantly more frequent in the samples with 2.5cER higher than 15% than in those below 15% (P = 0.013; Mann-Whitney). The percentage of the measured cells is 2.5cER exceeding the 2.5c value on the DNA scale. We earlier showed that this cut-off value of 2.5cER discriminated DNA aneuploidy. To conclude, topo IIalpha is a proliferation and also an apoptotic marker in atrophic OLP lesions and it might have a predictive value in oral lichen planus lesions prone to develop malignancy.

Comparison of cell proliferation in the centre and advancing fronts of oral squamous cell carcinomas using Ki-67 index

The cell proliferation status of 60 oral squamous cell carcinomas from Sri Lankan subjects was examined by immunohistochemistry using the Ki-67 index. A comparison was made between the indices derived from the centre of the tumours and those derived from the invasive fronts of the same tumours. There was a positive correlation between the two indices suggesting a clonal expansion of malignant cells, but the mean index derived for the invasive fronts (29.75 11.64) was significantly higher than the mean index for the body of these tumours (25.65 11.64). Thus, at a given time, more peripheral cells at the invasive front are proliferating and this compartment is likely to be more informative in prognostic and other behavioural studies involving the cell cycle. In squamous carcinomas, increased and uncontrolled cell proliferation at the invasive front may be one feature contributory to the invasion.

Prognosis of oral pre-malignant lesions: significance of clinical, histopathological, and molecular biological characteristics

The concept of a two-step process of cancer development in the oral mucosa, i.e., the initial presence of a precursor subsequently developing into cancer, is well-established. Oral leukoplakia is the best-known precursor lesion. The evidence that oral leukoplakias are pre-malignant is mainly derived from follow-up studies showing that between < 1 and 18% of oral pre-malignant lesions will develop into oral cancer; it has been shown that certain clinical sub-types of leukoplakia are at a higher risk for malignant transformation than others. The presence of epithelial dysplasia may be even more important in predicting malignant development than the clinical characteristics. Three major problems, however, are attached to the importance of epithelial dysplasia in predicting malignant development: (1) The diagnosis is essentially subjective, (2) it seems that not all lesions exhibiting dysplasia will eventually become malignant and some may even regress, and (3) carcinoma can develop from lesions in which epithelial dysplasia was not diagnosed in previous biopsies. There is, therefore, a substantial need to improve the histologic assessment of epithelial dysplasia or, since epithelial dysplasia does not seem to be invariably associated with or even a necessary prerequisite for malignant development, it may be necessary to develop other methods for predicting the malignant potential of pre-malignant lesions. As a consequence of these problems, numerous attempts have been made to relate biological characteristics to the malignant potential of leukoplakias. Molecular biological markers have been suggested to be of value in the diagnosis and prognostic evaluation of leukoplakias. Markers of epithelial differentiation and, more recently, genomic markers could potentially be good candidates for improving the prognostic evaluation of precursors of oral cancer. As yet, one or a panel of molecular markers has not been determined that allows for a prognostic prediction of oral pre-cancer which is any more reliable than dysplasia recording. However, these new markers could be considered complementary to conventional prognostic evaluation.

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.

Dynamics of parenchymal cell division, differentiation, and apoptosis in the young adult female mouse submandibular gland

The submandibular salivary gland of the young adult female mouse has two secretory cell types, acinar and granular duct, which are separated by intercalated ducts. Based on the occurrence of autologous cell division in these cells, they have been traditionally classified as expanding populations. However, differentiation from stem or progenitor cells in the intercalated ducts, usually associated with renewing populations, has also been detected. The question of renewing or expanding populations is resolved by quantitating and integrating the rates of autologous cell division, differentiation, and apoptosis for each cell type. The integrated data shows that both acinar and granular duct cell populations exhibit a substantial positive growth index, whereas the growth index for the intercalated duct cells is moderately negative. On balance, it suggests that the submandibular gland of the young adult female mouse is still growing. Comparison of young female mice with older females suggests that, although overall parenchymal growth slows with age, there is no longer a net loss of intercalated duct cells. Comparison with young adult male submandibular glands indicates that gender differences exist in the rates and mechanisms used for maintaining the different cell populations. The acinar and granular duct cell populations in young adult female mouse submandibular glands are expanding at the expense of the intercalated duct cell population, which appears to be contracting.