| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
We have previously reported a high prevalence of both aberrant β-catenin and cyclin D1 overexpression in radiation-associated thyroid cancers around the Semipalatinsk nuclear test site and Chernobyl accident-contaminated area. In our recent study, Pin1 expression seems to be closely correlated with the level of cyclin D1 overexpression and aberrant β-catenin expression, while neither mutation of β-catenin gene exon 3 nor APC is identified in papillary thyroid cancers (PTC) from radio-contaminated area. Furthermore, Pin 1 overexpression was confirmed in TPC-1, which is a cell line derived from PTC possessing no mutation in neither β-catenin exon 3 nor APC. Thus, Pin1 may be an important factor in regulating cyclin D1 and β-catenin expressions other than the activation of Wnt signaling pathway during thyroid carcinogenesis.
Points in the present study are as followings :
1 Up-regulation of cyclin D1 expression in thyroid canter by Pin1. : In two thyroid cancer cell lines, such as TPC-1 and ARO, an anaplastic thyroid cancer cell line, the level of cyclin D1 but β-catenin expression was significantly decreased by introduction of short interfering RNA s for Pin1.
2 Involvement of Pin1 in thyroid cellular response to irradiation : Pin1 can activate a role of p53 protein which induces apoptosis in radiation injury. The level of cyclin D1 expression was decreased at 2 hr after 10Gy X-ray irradiation in both TPC-1 (wild type p53) and ARO (mutant p53), while apoptotic cell death was more frequently observed in TPC-1 than ARO. Immunoprecipitation with TPC-1 and ARO demonstrated interactions between Pin1 and activated p53/cyclin D1 in irradiated cells.
In conclusion, Pin1 may be one of positive cell cycle regulators in thyroid cancer via up-regulation of cyclin D1 expression, and involved in cellular response to irradiation, such as apoptosis, by interactions with p53 and cyclin D1.
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