Autophagy analysis in oral carcinogenesis.

OBJECTIVE: The aim of this study was to evaluate the levels of autophagy in oral leukoplakia and squamous cell carcinoma and to correlate with clinical pathological features, as well as, the evolution of these lesions. METHODOLOGY: 7 Normal oral mucosa, 51 oral leukoplakias, and 120 oral squamous cell carcinomas (OSCC) were included in the study. Histological sections of the mucosa and leukoplakias were evaluated throughout their length, while the carcinomas were evaluated using Tissue Microarray. After the immunohistochemical technique, LC3-II positive cells were quantified in the different epithelial layers of the mucosa and leukoplakias and in the microarrays of the squamous cell carcinomas. The correlation between positive cells with the different clinical-pathological variables and with the evolution of the lesions was tested using the t test, ANOVA, and Kaplan-Meier survival analysis. RESULTS: We observed increased levels of autophagy in the oral squamous cell carcinomas (p<0.001) in relation to the other groups, but without any association with poorer evolution or survival of these patients. Among the leukoplakias, we observed a higher percentage of positive cells in the intermediate layer of the dysplastic leukoplakias (p=0.0319) and in the basal layer of lesions with poorer evolution (p=0.0133). CONCLUSION: The levels of autophagy increased during the process of oral carcinogenesis and are correlated with poorer behavior of the leukoplakias.

Survivin phosphorylation and M-phase promoting factor in oral carcinogenesis.

Survivin is a recently described inhibitor of apoptosis and mitotic regulator which is selectively over-expressed in human tumors. Its expression rate is predictive of disease progression, early recurrences and resistance to therapy. Up-regulation of survivin in oral pre-malignant lesions (OPL) and in oral squamous cell carcinoma (OSCC) has already been demonstrated in previous studies. A critical step for activation of survivin has been identified in the phosphorylation on Thr34 by the main mitotic kinase p34cdc2-cyclin B1. The aim of this work was to investigate the relationship between survivin, its phosphorylated active form (p-survivin) and M-phase promoting factor (MPF), p34cdc2-cyclin B1 in oral carcinogenesis. 32 OSCCs and 17 OPLs from surgical specimens were studied for cyclin B1, p-survivin, survivin, and p34cdc2 expression by immunohistochemistry. All cases of OSCC expressed survivin and its expression rate was correlated to p-survivin levels (P<0.05). Cyclin B1 was positive in 80% of cases, while p-34cdc2 was over-expressed in all OSCCs. All OPLs associated with OSCC expressed survivin and its levels were correlated to p-survivin levels (P<0.05). Cyclin B1 was positive in 70% of cases, while p-34cdc2 was positive in all OPLs. In conclusion, this study demonstrated that MPF, survivin and p-survivin are expressed during early and late phase of oral carcinogenesis. MPF proteins, which are co-expressed on mitotic apparatus, could represent a potential target for therapies based on manipulation of survivin phosphorylation, which would induce apoptosis in cancer cells.