OPG AND BCL-2 PROMOTE AMELOBLASTOMA CELL TUMORIGENESIS AND PREDICT PROGNOSIS FOR AMELOBLASTOMA PATIENTS

Ameloblastoma is the most frequent odontogenic epithelial tumor in the jaw. Though ameloblastoma belongs to benign odontogenic tumors, it exhibits a locally aggressive behavior with high recurrence rate. However, molecular markers predicting the recurrence have not been reported yet. The aim of this study was to find the prognostic markers in ameloblastoma. To detect apoptosis-related genes showing difference of expression level between ameloblastomas and normal oral tissues, the public database was analyzed. As results, OPG and Bcl-2 were identified as 2 most upregulated genes in ameloblastomas. To confirm public database analysis, in vitro study was conducted by use of AM-1 cell line. AM-1 cells expressed higher level of OPG and Bcl-2, compared with normal human epidermal keratinocytes (HEK). Exposing AM-1 cells to various environmental factors during culture in the 3-dimensional collagen gels were increased level of OPG and Bcl-2 than monoculture. To evaluate tumor-forming properties of AM-1 cells, subrenal capsule assay was conducted using AM-1 cells with hTERT-hNOF. As results, tumor formation were observed in 3 weeks, in which OPG and Bcl-2 expression was identified. To evaluate whether OPG and Bcl-2 regulates cell viability and apoptosis in AM-1 cells, siRNA transfection was conducted. As results, the knockdown of OPG and Bcl-2 reduced the cell viability and promoted the apoptosis of AM-1 cells. Knockdown of OPG and Bcl-2 decreased tumorigenesis. Eighty-nine cases of ameloblastomas were used for this study. Recurrence rate was 20.2%. Then, to validate whether these genes are associated to recurrence in ameloblastomas, immuno-histochemistry were performed. Each positivity classified 2 group by appropriate scoring system, low and high expression. The OPG and Bcl-2 expression was significantly associated with recurrence in conservative treatment group. These studies indicate that OPG and Bcl-2 status were independent predictive factors for recurrence.