Thesis (Ph.D.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Oral and Maxillofacial Pathology

Aim: to examine whether the expression of miRNA-16 and 21 (which are considered as apoptosis regulating miRNAs) alters in oral squamous cell carcinoma (OSCC) versus normal oral epithelium, and correlate their expression levels with that of one of their common downstream targets (the antiapoptotic BCL-2 protein). Methodology: this study was conducted on a total of 32 OSCC cases and 16 normal epithelium control cases. OSCC cases were graded as well, moderately, or poorly differentiated SCC, based on the degree of differentiation, cellular pleomorphism, and mitotic activity. Both moderately and poorly differentiated cases were placed as one group, whereas well differentiated cases were placed as a separate group. Quantitative real time polymerase chain reaction (qRT-PCR) was used to evaluate the expression of miRNA-16 and miRNA-21 in the 3 studied groups. The expression of BCL2 protein was evaluated by Immunohistochemical staining. Results: there was a statistically significant difference in miRNA-16 expression among the 3 studied groups, where it decreased gradually from the normal control group (mean 0.93) , followed by the well differentiated OSCC group (mean 0.36) , reaching the least levels in the moderate/poorly differentiated group (mean 0.17) . Also, the 3 groups showed a statistically significant difference in miRNA-21 expression, where the highest levels were observed in the moderate/poorly differentiated OSCC group (mean 9.35), followed by the well differentiated group (mean 3.70), and finally the normal control group (mean 0.96). However, all the studied groups showed negative BCL-2 immunostaining

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