ATM: Functions of ATM Kinase and Its Relevance to Hereditary Tumors

Ataxia-telangiectasia mutated (ATM) functions as a key initiator and coordinator of DNA damage and cellular stress responses. ATM signaling pathways contain many downstream targets that regulate multiple important cellular processes, including DNA damage repair, apoptosis, cell cycle arrest, oxidative sensing, and proliferation. Over the past few decades, associations between germline ATM pathogenic variants and cancer risk have been reported, particularly for breast and pancreatic cancers. In addition, given that ATM plays a critical role in repairing double-strand breaks, inhibiting other DNA repair pathways could be a synthetic lethal approach. Based on this rationale, several DNA damage response inhibitors are currently being tested in ATM-deficient cancers. In this review, we discuss the current knowledge related to the structure of the ATM gene, function of ATM kinase, clinical significance of ATM germline pathogenic variants in patients with hereditary cancers, and ongoing efforts to target ATM for the benefit of cancer patients

卵巣明細胞癌においてHNF-1β -USP28-Claspin pathwayはDNA損傷によるChk1活性化を促進する

Transcription factor hepatocyte nuclear factor 1-beta (HNF-1β) enhances checkpoint kinase 1 (Chk1) activation and promotes G2/M cell cycle progression in ovarian clear cell carcinoma (CCC) following exposure to diverse genotoxic agents including bleomycin. However, the underlying mechanism leading to checkpoint activation of HNF-1β still remains largely unknown. To clarify the effects of HNF-1β on cell cycle checkpoints, human CCC cell lines were transfected with siRNAs targeting HNF-1β, Claspin, USP28, or a control vector. Ubiquitination and stabilization of Claspin protein by HNF-1β was assessed by immunoprecipitation. Loss-of-function studies using RNAi-mediated gene silencing indicated that HNF-1β facilitated the Claspin expression after treatment with a genotoxic agent bleomycin, resulting in accumulation of phosphorylated Chk1 (p-Chk1) and promotion of survival in CCC cell lines. This study showed for the first time that USP28, a de-ubiquitinase crucial for Claspin expression, is one target gene of HNF-1β. Knockdown of endogenous USP28 suppressed the Claspin expression and p-Chk1 activation and cell viability. Our findings identify a novel pathway of the HNF-1β-USP28-Claspin-Chk1 axis in checkpoint signal amplification in response to DNA damage. Targeting this pathway may represent a putative, novel, anticancer strategy in ovarian CCC.博士（医学）・乙第1435号・令和元年9月27日Copyright © 2018 Impact Journals, LLCCopyright © Ito et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC BY 3.0 https://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

卵巣子宮内膜症性嚢胞の癌化におけるCD44v9と8-OHdGの発現

Aim: Expression of CD44 variant isoforms (CD44v) promotes the synthesis of reduced glutathione and contributes to reactive oxygen species defense through up-regulation of the intracellular antioxidant. The aim of the study was to investigate the expression of CD44v9 and oxidative DNA damage marker, 8-OHdG, in benign ovarian endometrioma (OE) and OE harboring clear cell carcinomas (CCC). Methods: A retrospective study was performed at the Department of Gynecology, Nara Medical University hospital from January 2006 to December 2012. Patients with histologically confirmed benign OE (n = 27) and OE harboring areas of CCC (n = 8) were selected. Tissue samples were immunohistochemically analyzed for the presence of CD44v9 and 8-OHdG using avidin-biotin complex method. Results: CD44v9 was located on the cell membrane of endometriotic epithelial cells and expressed in 88.9% (24/27) of benign OE tissues. Only 25.0% (2/8) of benign endometriotic lesions adjacent to CCC was found to stain weakly for CD44v9. Percentage of CD44v9 positive cells was 68.5 ± 20.2% (mean ± standard deviation) of benign OE, 16.7 ± 16.5% of CCC endometriotic tissue (P < 0.001). Compared to benign OE, CCC endometriotic tissue showed a significant increase in the proportion of 8-OHdG expression (77.3 ± 22.5% vs 94.9 ± 3.0%, P = 0.049). A significant negative correlation was observed between CD44v9 status and 8-OHdG nuclear expression (r = -0.458, P = 0.006). Conclusion: Alterations in CD44v9 and 8-OHdG may be associated with malignant transformation of benign OE.博士（医学）・乙第1452号・令和2年3月16日© 2019 Japan Society of Obstetrics and Gynecology.This is the peer reviewed version of the following article: [https://obgyn.onlinelibrary.wiley.com/doi/full/10.1111/jog.14093], which has been published in final form at [https://doi.org/10.1111/jog.14093]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

卵巣明細胞腺癌における転写因子HNF-1βはDNA損傷チェックポイント機構の一つであるCHK1タンパクを制御し、抗癌剤耐性を獲得する

Objective Appropriate cell cycle checkpoints are essential for the maintenance of normal cells and chemosensitivity of cancer cells. Clear cell adenocarcinoma (CCA) of the ovary is highly resistant to chemotherapy. Hepatocyte nuclear factor-1β (HNF-1β) is known to be overexpressed in CCA, but its role and clinical significance is unclear. We investigated the role of HNF-1β in regulation of the cell cycle in CCA. Methods To clarify the effects of HNF-1β on cell cycle checkpoints, we compared the cell cycle distribution and the expression of key proteins involved in CCA cells in which HNF-1β had been stably knocked down and in vector-control cell lines after treatment with bleomycin. HNF-1β (+) cells were arrested in G2 phase because of DNA damage. Results HNF-1β (−) cells died because of a checkpoint mechanism. G2 arrest of HNF-1β (+) cells resulted from sustained CHK1 activation, a protein that plays a major role in the checkpoint mechanism. HNF-1β (+) cells were treated with a CHK1 inhibitor after bleomycin treatment. Flow cytometric analysis of the cell cycle demonstrated that DNA damage–induced G2-arrested cells were released from the checkpoint and killed by a CHK1 inhibitor. Conclusions The chemoresistance of CCA may be due to aberrant retention of the G2 checkpoint through overexpression of HNF-1β. This is the first study demonstrating cell cycle regulation and chemosensitization by a CHK1 inhibitor in CCA.博士（医学）・乙第1345号・平成26年12月3日© 2014 by the International Gynecologic Cancer Society and the European Society of Gynaecological Oncology

Potential role of LMP2 as an anti-oncogenic factor in human uterine leiomyosarcoma: Morphological significance of calponin h1

Uterine leiomyosarcoma (LMS) is a highly metastatic smooth muscle neoplasm for which calponin h1 is suspected to have a biological role as a tumor-suppressor. We earlier reported that LMP2-null mice spontaneously develop uterine LMS through malignant transformation of the myometrium, thus implicating this protein as an anti-tumorigenic candidate as well. In the present study, we show that LMP2 may negatively regulate LMS independently of its role in the proteasome. Moreover, several lines of evidence indicate that although calponin h1 does not directly influence tumorigenesis, it clearly affects LMP2-induced cellular morphological changes. Modulation of LMP2 may lead to new therapeutic approaches in human uterine LMS.ArticleFEBS LETTERS. 586(13):1824-1831 (2012)journal articl

Potential role of LMP2 as tumor-suppressor defines new targets for uterine leiomyosarcoma therapy

Although the majority of smooth muscle neoplasms found in the uterus are benign, uterine leiomyosarcoma (LMS) is extremely malignant, with high rates of recurrence and metastasis. We earlier reported that mice with a homozygous deficiency for LMP2, an interferon (IFN)-gamma-inducible factor, spontaneously develop uterine LMS. The IFN-gamma pathway is important for control of tumor growth and invasion and has been implicated in several cancers. In this study, experiments with human and mouse uterine tissues revealed a defective LMP2 expression in human uterine LMS that was traced to the IFN-gamma pathway and the specific effect of JAK-1 somatic mutations on the LMP2 transcriptional activation. Furthermore, analysis of a human uterine LMS cell line clarified the biological significance of LMP2 in malignant myometrium transformation and cell cycle, thus implicating LMP2 as an anti-tumorigenic candidate. This role of LMP2 as a tumor suppressor may lead to new therapeutic targets in human uterine LMS.ArticleSCIENTIFIC REPORTS. 1:180 (2011)journal articl

Self-Turn-on-Free 5V Gate Driving for 1200V Scaled IGBT

Negative biasing of the gate voltage in a scaled insulated gate bipolar transistor (IGBT) during the off-state was modeled and found to be effective against self-turn-on failures. The required self-turn-on-free criteria were verified experimentally.31st IEEE International Symposium on Power Semiconductor Devices and ICs (ISPSD 2019), 19-23 May 2019, Shanghai, Chin