| Budget Amount *help |
¥3,830,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥330,000)
Fiscal Year 2007: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2006: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
This research project was carried out in order to study a possible molecular pathway of secondary malignant transformation from oral benign tumors. We mainly focused on calcifying cystic odontogenic tumor (COT), because we had already proposed a possible of malignant changes within calcifying odontogenic cyst. To this end, we have isolated six cell systems (designated COT1 to COT6) from a calcifying odontogenic cyst arising in the maxilla of a 54 year-old male. COT1-COT6 showed odontogenic epithelial characteristics with polygonal cell shapes: they were immunopositive for keratin and expressed distinct mRNA levels for keratin 16, amelogenin, tuftelin, BSP, MMP-20, and ALP. In co-cultures with fibroblasts, COT6 cells grew to form nestic structures, in which ghost cells and calcified materials appeared in the later stage. Finally, they developed into calcified nodules within the COT6 cell nests. Chromosome analyses showed the cells had not only numeral abnormalities such as 3n ploidies w
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ith average numbers of 59 chromosomes but also various kinds of structural abnormalities. Among them, der(9)t(9; 13)(p13.3;q12.3) was shared by all of the six cell systems. COT cells formed tumors with a squamous cell carcinoma-like appearance in nude mice. Keratinization in transplanted tumor cell foci was closely associated with ghost cell differentiation and calcification. Also in surgical specimens of COC, ghost cells were positive for extracellular matrix (ECM) molecules including perlecan as well as MMP7 or β-catenin. The results indicated that ghost cells were generated by cytoplasmic retention of ECM molecules, which were related to Wnt signaling pathways.
These results show that COT is potentially neoplastic, and that the six COT cell systems are useful models for investigating the molecular mechanisms of ghost cell differentiation and epithelial calcification. In addition, the findings suggest that COT contains precancerous tumor cells which are able to transform into malignant with above mentioned gene alterations. The present study is the first in-vitro demonstration of secondary malignant transformation from a benign odontogenic tumor. Less
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