The prognostic significance of proliferation markers Ki-67 and MCM2 and p53 protein expression in salivary gland neoplasms

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the research requirements for the degree of Master of Dentistry (MDent) in the field of Oral Pathology Johannesburg, 2015Cell proliferation is associated with tumour biological behaviour. Correlation of proliferation marker and p53 expression with histologic grade in salivary gland neoplasia is important to establish tumour behaviour and prognostic biomarkers may be useful in their histologic differentiation and treatment. Objectives: To evaluate expression of proliferation markers MCM2 and Ki-67, and tumour suppressor gene p53 in salivary gland neoplasms and to correlate this expression with tumour type. Materials and methods: Tissue from 19 pleomorphic adenomas (PAs), 15 polymorphous low grade adenocarcinomas (PLGAs), 11 mucoepidermoid carcinomas (MECs), 12 acinic cell carcinomas (AcCCs) and 13 adenoid cystic carcinomas (AdCCs) was analysed for immunohistochemical expression of MCM2, Ki-67 and p53. The labelling index (LI) for each tumour was determined by counting the percentage of positive cells per 1000 tumour cells. A Kruskal-Wallis test was used to assess differences in LIs. Results: Overall, MCM2 (p=0.0001) and Ki-67 (p=0.0001) expression was significantly higher compared to p53 (p=0.2447) amongst the five salivary gland tumours. The AdCC MCM2 LI was significantly higher compared to AcCC (p=0.0024), PLGA (p=0.0002), MEC (p=0.0028) and PA (p=0.0001). There were no significant differences in MCM-2 expression between the other neoplasms. Conclusion: MCM2 is a more sensitive marker than Ki-67 and showed significantly greater expression in all tumours studied. The Ki-67 and MCM2 labelling indices were significantly higher in AdCC than in MEC, AcCC, PA and PLGA