京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22307号 / 医博第4548号 / 新制||医||1040(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 武藤 学, 教授 松田 道行, 教授 髙折 晃史 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The bulk degradative process of macroautophagy requires the dynamic growth of autophagosomes, which carry cellular contents to the lysosome for recycling. Atg9A, a multi-pass transmembrane protein, is an apical regulator of autophagosome growth, yet its regulatory mechanism remains unclear. Our work suggests that hypoxia (low glucose and oxygen) triggers a rearrangement of the small adapter protein 14-3-3ζ interactome. Our data suggest that the localization of mammalian Atg9A to autophagosomes requires phosphorylation on the C terminus of Atg9A at S761, which creates a 14-3-3z docking site. Under basal conditions, this phosphorylation is maintained at a low level and is dependent on both ULK1 and AMPK. However, upon induction of hypoxic stress, activated AMPK bypasses the requirement for ULK1 and mediates S761 phosphorylation directly, resulting in an increase in 14-3-3z interactions, recruitment of Atg9A to LC3-positive autophagosomes, and enhanced autophagosome production. These observations suggested to us that long unstructured C-terminus of Atg9A may be a site of protein docking and regulation. We used BioID, along with conventional interactomics, to map the C- and N-terminal proximity-based interactions of Atg9A. We identified a network of Atg9A C-terminal interactions that include members of the ULK1 complex. Using gel filtration, we find that Atg9A co-immunoprecipitates with the ULK1 complex in high molecular weight fractions. Moreover, phosphorylation of the Atg9A C-terminus at S761 occurs within the ULK1 complex under nutrient-replete conditions, while hypoxia triggers a redistribution of phosphorylated Atg9A to low molecular weight fractions. Probing these relationships further, we find that Atg13, a component of the ULK1 complex, directly interacts with Atg9A and is required for Atg9A C-terminal phosphorylation. Furthermore, a non-phosphorylatable mutant of Atg9A (S761A) accumulates with Atg13 in high molecular weight complexes. Together, these data suggest that Atg13 recruits Atg9A to the ULK1 complex at the phagophore assemble site (PAS) and that S761 phosphorylation triggers Atg9A retrieval from the PAS

Les cancers de l’ovaire présentent un taux de survie à 5 ans inférieur à 40% et constituent la principale cause de décès par cancer gynécologique dans le monde. Ce sombre pronostic s’explique par un diagnostique tardif (du à un développement asymptomatique dans les premiers stades) et une résistance aux traitements existants et souligne la nécessité de développer de nouvelles approches thérapeutiques. La découverte ces dernières années, d’un nombre important de lncRNAs a permis d’ouvrir de nouvelles perspectives pour la recherche en oncologie. Peu d’études ont à ce jour exploré leur implication dans la chimiorésistance, a fortiori dans les cancers de l’ovaire. Parmi ces lncRNAs, ‘UCA1’ exerce de multiples fonctions oncogéniques par des mécanismes encore peu décrits. Son expression constitue un facteur de mauvais pronostique dans diverses tumeurs malignes dont les cancers de l’ovaire. Nous avons pu démontrer un rôle de ceRNA pour le miR-27a-5p, qui une fois libéré suite à l’inhibition d’UCA1, régule négativement UBE2N, une cible directe. UBE2N est un acteur connu des voies de réparation de l’ADN et de la régulation de la voie NF-kB, et son inhibition dans nos modèles entraîne une augmentation de l’expression de BIM et perturbe les mécanismes de réparation de l’ADN, sensibilisant des cellules cancéreuses ovariennes à l’action des sels de platine et des PARPi. L’inhibition d’UBE2N sensibilise également aux sels de platine plusieurs cultures organoïdes tridimensionnelles dérivées de patientes, et pourrait ainsi constituer une stratégie thérapeutique innovante pour lutter contre la chimiorésistance dans le cancer de l'ovaire. / Ovarian cancers present a 5-year survival rate of under 40% and are the leading cause of death from gynecological cancer worldwide. This poor prognosis is explained by a late diagnosis (due to asymptomatic development in the early stages) and resistance to existing treatments and highlights the need to develop new therapeutic approaches. The discovery in recent years of a significant number of lncRNAs has opened up new opportunities for oncology research. Few studies have so far explored their involvement in chemoresistance, let alone ovarian cancer. Among these lncRNAs, 'UCA1' performs multiple oncogenic functions through mechanisms not yet well described. Its expression is a factor of poor prognosis in various malignant tumours including ovarian cancers. We were able to demonstrate a role of ceRNA for miR-27a-5p, which when released following the inhibition of UCA1, negatively regulates UBE2N, a direct target. UBE2N is a known actor in DNA repair pathways and NF-kB pathway regulation, and its inhibition in our models leads to an increase in BIM expression and disrupts DNA repair mechanisms, sensitizing ovarian cancer cells to the action of platinum salts and PARPi. The inhibition of UBE2N also sensitizes to platinum salts, several three-dimensional organoid cultures derived from patients, thus may provide an innovative therapeutic strategy to combat chemoresistance in ovarian cancer.

Yes / Malignant pleural mesothelioma (MPM) is associated with an extremely poor prognosis, and most patients initially are or rapidly become unresponsive to platinum-based chemotherapy. MicroRNA-31 (miR-31) is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many MPM tumors. Based on previous findings in a variety of other cancers, we hypothesized that miR-31 alters chemosensitivity and that miR-31 reconstitution may influence sensitivity to chemotherapeutics in MPM. Reintroduction of miR-31 into miR-31 null NCI-H2452 cells significantly enhanced clonogenic resistance to cisplatin and carboplatin. Although miR-31 re-expression increased chemoresistance, paradoxically, a higher relative intracellular accumulation of platinum was detected. This was coupled to a significantly decreased intranuclear concentration of platinum. Linked with a downregulation of OCT1, a bipotential transcriptional regulator with multiple miR-31 target binding sites, we subsequently identified an indirect miR-31-mediated upregulation of ABCB9, a transporter associated with drug accumulation in lysosomes, and increased uptake of platinum to lysosomes. However, when overexpressed directly, ABCB9 promoted cellular chemosensitivity, suggesting that miR-31 promotes chemoresistance largely via an ABCB9-independent mechanism. Overall, our data suggest that miR-31 loss from MPM tumors promotes chemosensitivity and may be prognostically beneficial in the context of therapeutic sensitivity.

Tumour necrosis has long been associated with poor prognosis and reduced survival in cancer. Hypotheses to explain this include the idea that as aggressive tumours tend to grow rapidly, they outgrow their blood supply leading to areas of hypoxia and subsequently necrosis. However whilst this and similar hypotheses have been put forward to explain the association, the biological significance of the cells which make up necrotic tissue has been largely ignored. This stems from the belief that because a tumour is more aggressive and fast growing it develops areas of necrosis, rather than, the tumour is more aggressive because it contains areas of necrosis. Which came first like the egg and chicken is yet to be determined, however to date most research has only considered the possibility of the former. Viable cells were found in the necrotic core of Multicellular Tumour Spheroids. When examined these cells were found to be different to the original cell line in terms of proliferation, migration, and chemosensitivity. A proteomic analysis showed that these phenotypical changes were accompanied by changes in a large number of proteins within the cells, some of which could be potential therapeutic targets. Furthermore this has led to a new hypothesis for tumour necrosis and its association with poor prognosis. Necrotic tissue provides a microenvironemental niche for cells with increased survival capabilities. Protected from many chemotherapeutics by their non-proliferative status once conditions improve these cells can return to proliferation and repopulate the tumour with an increasingly aggressive population of cells. / Yorkshire Cancer Research

In patients with acute myeloid leukemia (AML), cytarabine-based chemotherapy usually achieves remission, but this is commonly followed by relapse and chemo-resistance. In this study, we aim to establish next-generation sequencing (NGS)-based microRNA expression profiling and pathway analysis to identify pathways regulated differentially between chemo-sensitive and -resistant AML as potential therapeutic targets. MicroRNA expression profiles differ significantly between chemo-sensitive and chemo-resistant AML cells and reflect differences in the activity of intracellular signaling cascades. Alterations in signaling pathway activities contribute to treatment resistance and thus represent potential drug targets. Our microRNA-led approach indicates a role for activin receptor type 2A in ARA-C resistance of AML cells and suggests activin receptor signaling to be a candidate pathway for targeted therapy.

Gliomas are aggressive glial cell tumors that are nearly impossible to treat successfully, yielding strikingly low survival rates for patients. Glioblastomas, the most severe type of gliomas, have even poorer prognoses. In the past decade, new literature has shown that H19, a long non-coding RNA (lncRNA), is not only highly expressed in human gliomas, but that it plays several important roles in glioma progression and can even impede certain treatment measures. H19 directly and indirectly promotes several features of glioma cells including their survival, growth, migration, invasion, metastasis – essentially every stage of glioma development – and even stemness. Simply knocking down H19, in vitro, hampered every single one of these features to some degree. High H19 levels have also been linked to a lack of response to temozolomide and radiation treatments, two of the main therapeutic methods currently used to target gliomas. In vivo observations also followed this pattern of high H19 levels correlating with glioma tumorigenicity. So far, due to the accumulation of such findings, H19 has already become valued as both a prognostic and theragnostic marker. However, having seen how damaging H19 knockdown is to gliomas, there is no reason the role of H19 should be limited to that of an indicator; rather, the proto-oncogenic lncRNA should be viewed as a potential therapeutic target. Moreover, given that high H19 expression is an attribute unique to the human embryo stage, any instances of upregulation are typically oncogenic in nature, making H19 an ideal target for cancer therapy. Thus, targeting H19 in glioma patients should be integrated into existing treatment plans as this will obstruct glioma tumorigenesis, improve responsiveness to other therapies, and is not likely to impede normal biological functions.

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