肺腺癌発生過程におけるDNAメチル化変化の解析

筑波大学 (University of Tsukuba)201

肺腺癌発生過程におけるDNAメチル化変化の解析

この博士論文は内容の要約のみの公開（または一部非公開）になっています筑波大学 (University of Tsukuba)201

Ubiquitin‐specific protease 8 is a novel prognostic marker in early‐stage lung adenocarcinoma

Alterations of epidermal growth factor receptor (EGFR) expression frequently occur in early‐stage lung adenocarcinoma. Ubiquitin‐specific protease 8 (USP8) has been reported to stabilize EGFR protein at the plasma membrane through the recycling pathway. Here, we examined the correlation between USP8 expression and the expression or mutation status of EGFR, as well as the clinicopathological features of lung adenocarcinoma and patient outcome. Expression of EGFR and USP8 in surgically resected specimens of lung adenocarcinoma (82 cases) was examined by immunohistochemistry. Overexpression of EGFR was mutually correlated with that of USP8, and was also associated with clinicopathological features including pathological subtype, lymphatic permeation, and vascular invasion. Moreover, patients who had USP8‐positive tumors had a significantly poorer outcome than those who were USP8‐negative, not only overall but also patients who were EGFR‐negative. Although EGFR was expressed in invasive adenocarcinoma but not in adenocarcinoma in situ (AIS), USP8 was overexpressed in not only invasive adenocarcinoma but also 38.1% of AIS cases. In vitro, USP8 regulated the expression and half‐life of EGFR in immortalized AIS cells, and also cell proliferation. Our findings indicate that overexpression of USP8 in lung adenocarcinoma is an early event during the course of tumor progression, and is related to EGFR expression

miR-3941: A novel microRNA that controls IGBP1 expression and is associated with malignant progression of lung adenocarcinoma

Immunoglobulin (CD79a) binding protein 1 (IGBP1) is universally overexpressed in lung adenocarcinoma and exerts an anti-apoptotic effect by binding to PP2Ac. However, the molecular mechanism of IGBP1 overexpression is still unclear. In the present study, we used a microRNA (miRNA) array and TargetScan Human software to detect IGBP1-related miRNAs that regulate IGBP1 expression. The miRNA array analysis revealed more than 100 miRNAs that are dysregulated in early invasive adenocarcinoma. On the other hand, in silico analysis using TargetScan Human revealed 79 miRNAs that are associated with IGBP1 protein expression. Among the miRNAs selected by miRNA array analysis, six (miR-34b, miR-138, miR-374a, miR-374b, miR-1909, miR-3941) were also included among those selected by TargetScan analysis. Real-time reverse transcription PCR (real-time RT-PCR) showed that the six microRNAs were downregulated in invasive adenocarcinoma (IGBP1+) relative to adjacent normal lung tissue (IGBP1−). Among these microRNAs, only miR-34b and miR-3941 depressed luciferase activity by targeting 3′UTR-IGBP1 in the luciferase vector. We transfected miR-34b and miR-3941 into lung adenocarcinoma cell lines (A549, PC-9), and both of them suppressed IGBP1 expression and cell proliferation. Moreover, the transfected miR-34b and miR-3941 induced apoptosis of a lung adenocarcinoma cell line, similarly to the effect of siIGBP1 RNA. As well as miR-34b, we found that miR-3941 targeted IGBP1 specifically and was able to exclusively downregulate IGBP1 expression. These findings indicate that suppression of miR-3941 has an important role in the progression of lung adenocarcinoma at an early stage