泛素是一種關鍵修飾因子，可以透過轉譯後修飾調控其靶蛋白的降解和功能。USP24是去泛素化酶之一，並且被研究過參與帕金森病和癌症發展。根據實驗室先前的研究得知USP24可以在惡性肺癌腫瘤相關的巨噬細胞中高度表現以增加癌症惡性。而根據我們的研究發現，USP24過度表現會透過穩定β-TrCP而降低DNMT1表現，我們假設USP24可以透過DNA甲基化調控基因表現進一步調控癌症發展，研究了肺癌中基因的表現和DNA甲基化之間的相關性。透過DNA微陣列發現了FZD7甲基化增加，而在靜默USP24後mRNA表現降低，表示USP24對FZD7是正調控且是透過DNMT1介導的DNA甲基化。在此研究中發現USP24可以透過增加FZD7的表現來正調控Wnt pathway。為了知道FZD7在肺癌中扮演的角色及對肺癌細胞的影響，在肺癌細胞中靜默FZD7並發現其細胞增生及爬行能力皆被抑制。我們也發現在A549細胞中靜默USP24可以明顯降低FZD7 啟動子的螢光素酶活性，表示USP24可以藉由FZD7 啟動子抑制FZD7的表現。最後知道分別在靜默USP24及FZD7後β-catenin的表現皆會下降，此結果指出USP24可能會正調控 FZD7 及 β-catenin 而影響Wnt pathway。由於Wnt pathway 對於癌症的發展很重要，因此該研究將有利於未來癌症治療的藥物開發。

Ubiquitin is a critical modifier that regulates the degradation and function of its target proteins through post-translational modification. USP24 is one of the deubiquitinases and has been studied to be involved in Parkinson disease and cancer progression previously. In our lab, we found USP24 can be highly expressed in malignant lung cancer progression tumor-associated macrophages to increase the cancer malignant. Our recent studies showed that USP24 overexpression decreased DNMT1 level through stabilizing β-TrCP, implying that USP24 may regulate gene expression through DNA methylation to regulate cancer progression. We studied the relevance between gene expression and DNA methylation in lung cancer systemically. Through the gene expression microarray and DNA methylation we found the gene, Frizzled 7 (FZD7), which was increased in DNA methylation repertoire and was decreased in mRNA level under knockdown of USP24, indicating that USP24 positive regulated FZD7 through DNMT1-mediated DNA methylation. In order to know the role of FZD7 in lung cancer cell, we knockdown of FZD7 expression and found that the cell migration and proliferation would be decreased in A549 cell. Also, we constructed FZD7 promoter and found its activity would decrease after USP24 knockdown in A549 cells, implying that USP24 can regulate FZD7 expression through activating FZD7 promoter. Last, we also silenced USP24 and FZD7 individual and both of the result would decrease β-catenin protein level. Above all the results, indicating that USP24 could positively regulate Wnt pathway through increase in the expression of FZD7. Since Wnt pathway is important in cancer progression, this study will be beneficial to the drug development for cancer therapy in the future.

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