Study On Cell Proliferation And Differentiation Of Ameloblastoma

Objective: To investigate the proliferating activity and the molecular mechanisms of cell proliferation in ameloblastoma and this may lay a foundation to the therapy. To study the cell differentiation and differentiating markers in ameloblastoma and this may be helpful in histological diagnosis and prognostic prediction. Materials and Methods: 322 cases of ameloblastoma were collected and some of the cases were chosen to study the cell proliferation and differentiation. ① Expressions of PCNA, Ki-67 , CK10&13 and CK19 were detected in 43 ameloblastoma by SP immunohistochemical method , and investigate whether there existed difference between the peripheral cells and central cells of tumor nests or strands. ② 17 cases of malignant ameloblastoma were examined by HE, AgNOR, DNA staining and morphometric analysis. The quantitatively pathological diagnosis was carried out on malignant ameloblastoma. ③ The ameloblastoma-related genes were screened out using DNA microarray method, and this may be helpful for further study. ④ The expressions of cyclin D1, CDK4 and p16 proteins were examined in 52 cases of benign and malignant ameloblastoma immunohistochemically using SP method and the expression of cyclin D1 mRNA was investigated by in situ hybridization technique. ⑤ The total of 72 cases of ameloblastoma were chosen for detection of the expression of amelogenin mRNA using in situ hybridization. In addition, 6 cases of fresh ameloblastoma tissue samples were analyzed using RT-PCR method. ⑥ 322 cases of ameloblastoma were collected and stained with haematoxylin-erosin staining. The slides were reanalyzed according to the classifications of odontogenic tumors (WHO, 1992) to investigate the clinicopathological features. Results: ① The PCNA and Ki-67 labelling indices were significantly higher in peripheral cells of tumor nests or strands than those in central cells(p<0.01). The positive expressions of CK10&13 and CK19 were significantly higher in central cells than in peripheral cells (p<0.05). ② AgNOR count and DNA index in malignant ameloblastoma were significantly higher than those in benign ameloblastoma(P<0.01). Logistic regression equation was established according to nuclear morphometric parameters and DNA index. ③ Among 700 target genes, 32 differentially expressed genes were found between ameloblastoma and normal oral mucosa tissues. Up-and down-regulated genes were 5 and 27 respectively. ④ The expression of cyclin D1 and mRNA in benign or malignant ameloblastoma was significantly higher than that in normal oral mucosa(p<0.01). The expressions of CDK4 and p16 showed significant difference between each type of benign, malignant ameloblastoma and normal oral mucosa (p<0.01). ⑤ The positive expression of amelogenin mRNA was 42 cases out of 55 benign ameloblastoma (76.4%) and showed no significantly difference between different types(p>0.05). 2 cases out of 17 malignant ameloblastoma were positive and was significantly lower than that in benign ameloblastoma (p<0.01). The amplified products of amelogenin mRNA were detected in 4 cases out of 6 ameloblastoma using RT-PCR method. ⑥ Among the 322 cases of ameloblastoma , 117 cases were plexiform type, 85 cases were follicular type, 22 cases were mixed type, 25 cases were acanthomatous type, 6 cases were granular type, 11 cases were desmoplastic type, 51 cases were unicystic type, 3 cases were peripheral type,and 1 case was keratoameloblastoma and papilliferous keratoameloblastoma respectively. The total recurrence rate was 21.1% and benign type was 21.1%, malignant type, 41.2%. The recurrence rate of curettage and enucleation was 52.7% and 62.5% respectively and showed significantly higher than other types of operation (p<0.01). Conclusions: ① The peripheral zones of tumor nests or strands were regarded as proliferating areas; There existed a significantly different differentiation between central cells and peripheral cells ② Quantitative analysis of DNA content ,nuclear morphometric parameters and AgNOR count may be helpful in differentiating malignant from benign ameloblastoma ③ cDNA microarray technique was effective in screening the differentially expressed genes between two different kinds of tissues. Further analysis of those obtained genes will be helpful to understand the molecular mechanisms of ameloblastoma. ④ Cyclin D1, CDK4 and p16 may be concerned with the initiation and progression in ameloblastoma. CDK4 and p16 may be helpful in differentiating benign from malignant ameloblastoma. ⑤ The detection of amelogenin gene may be regarded as a specific marker in evaluating cell differentiation of ameloblastoma. ⑥ The histological spectrum of ameloblastoma was polymorphic. The prognosis was mainly concerned with clinicopathologic types and the ways of operation.