| Co-Investigator(Kenkyū-buntansha) |
HISATOME Ichiro Tottori University, Graduate School of Medical Science, Professor, 大学院・医学系研究科, 教授 (60211504)
ITOH Toshiyuki Tottori University, Faculty of Engineering, Professor, 工学部, 教授 (50193503)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
Anaplastic thyroid carcinoma is a poorly differentiated carcinoma found in elderly people. The patients with anaplastic carcinoma always suffer from poor prognosis. It is an urgent business to develop the effective strategy to suppress the growth of anaplastic carcinoma and prolong the prognosis of patients. We focused on the ubiquitin-proteasome sytem. Proteasome is a major intracellular proteinase found as a large protein complex composed of at least 14 distinct but homologous subunits with molecular masses of 21-32kD and they are assembled into an approximately 700kDa cylindcal structure. We analyzed the expression of proteasome subunits in anaplastic thyroid carcinoma and found that proteasome subunit C2 and proteasome activator g(PA28g) are highly expressed in its rapid-growing cancer cells. Interestinglly, PA28g is localized in nuclei of cancer cells, suggesting PA28g, could be one of the good candidate for manipulating the growth of cancer cells. Proteasome inhibitors such as la
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ctacystin significantly blocked the DNA synthesis of thyroid carcinoma cell line, indicating the intrinsic 20S proteasome is involved in cancer cell growth. We then analyzed the detailed turn-over of PA28g using rat functional thyroid cell line, FRTL5 cells. Interestingly, TSH and insulin treatment not only upregulate PA28-γ expression but also recruite PA28-γ from cytosol to nucleus. The combination of TSH and insulin showed highest inducibility of PA28-γ as well as dual DNA synthesis of FRTL5. Thus, our results indicate PA28-γ is induced by goitrogenic factors, TSH and insulin, in thyroid cell and potentially contribute to thyroid cell growth by potentiating 20S proteasome activity. Taken together, overexpressed proteasome component such as C2 or PA28-γ will be good candidates for manipulating proteasome activity, thereby interfering with anaplastic cancer cell growth.
Simultaneously, we searched novel candidate genes for mapipulating the growth rate of anaplastic thyroid cancer. In order to isolate a novel gene, we used a unique strategy named SEREX. We used expression library derived from cancer tissue and surveyed 1X106 plaque by autologous patient sera. After all, we could isolate two positive clones. One of them was WD repeat protein 1(WDR1), which is the human counterpart of actin interacting protein 1. WDR1 is highly expressed in anaplastic thyroid cancer tissues, indicating that WDR1 could be involved in cancer cell proliferation. It still remains unclear that WDR1 protein is degraded by ubiquitin-proteasome dependent pathway. But, if it is degraded via proteasome-dependent fashion, WDR1 will be a good candidate for anti-cancer therapy. Less
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