Mieap forms membrane-less organelles involved in cardiolipin metabolism

Biomolecular condensates (BCs) are formed by proteins with intrinsically disordered regions (IDRs) via liquid-liquid phase separation. Mieap/Spata18, a p53-inducible protein, participates in suppression of colorectal tumors by promoting mitochondrial quality control. However, the regulatory mechanism involved remains unclear. Here, we report that Mieap is an IDR-containing protein that drives formation of BCs involved in cardiolipin metabolism. Mieap BCs specifically phase separate the mitochondrial phospholipid, cardiolipin. Mieap directly binds to cardiolipin in vitro. Lipidomic analysis of cardiolipin suggests that Mieap promotes enzymatic reactions in cardiolipin biosynthesis and remodeling. Accordingly, four cardiolipin biosynthetic enzymes, TAMM41, PGS1, PTPMT1, and CRLS1 and two remodeling enzymes, PLA2G6 and TAZ, are phase-separated by Mieap BCs. Mieap-deficient cells exhibit altered crista structure, leading to decreased respiration activity and ATP production in mitochondria. These results suggest that Mieap may form membrane-less organelles to compartmentalize and facilitate cardiolipin metabolism, thus potentially contributing to mitochondrial quality control.

Identification of a mitochondrial targeting sequence in cathepsin D and its localization in mitochondria

Cathepsin D (CTSD) is a major lysosomal protease harboring an N-terminal signal peptide (amino acids 1-20) to enable vesicular transport from endoplasmic reticulum to lysosomes. Here, we report the possibility of a mitochondrial targeting sequence and mitochondrial localization of CTSD in cells. Live-cell imaging analysis with C-terminal enhanced green fluorescent protein-tagged CTSD (EGFP-CTSD) indicated that CTSD localizes to mitochondria. CTSD amino acids 21-35 are responsible for its mitochondrial localization, which exhibit typical features of mitochondrial targeting sequences, and are evolutionarily conserved. A proteinase K protection assay and sucrose gradient analysis showed that a small population of endogenous CTSD molecules exists in mitochondria. These results suggest that CTSD is a dual-targeted protein that may localize in both lysosomes and mitochondria.

MIEAP and ATG5 are tumor suppressors in a mouse model of BRAFV600E-positive thyroid cancer

Mitochondria-eating protein (MIEAP) is a molecule important for non-canonical mitophagy and thought to be a tumor suppressor. Our previous study found that MIEAP expression is defective in thyroid oncocytomas, irrespective of being benign or malignant, and also in non-oncocytic thyroid cancers. Thyroid oncocytomas are composed of large polygonal cells with eosinophilic cytoplasm that is rich in abnormal mitochondria. Thus, our data indicate that, together with increased mitochondrial biogenesis that compensates for the dysfunction of the mitochondria, MIEAP plays a critical role in the accumulation of mitochondria in thyroid oncocytic tumors, whereas a defective MIEAP expression alone is not sufficient for mitochondrial accumulation in non-oncocytic cancers with normal mitochondria. To clarify whether MIEAP is a tumor suppressor in the thyroids and whether MIEAP knockout (KO) alone is sufficient for the oncocytic phenotype and also to extend our effort toward canonical mitophagy (a selective autophagy), we here conducted mouse studies using genetically engineered mice. BrafCA/wt mice developed thyroid cancers 1 year after intrathyroidal injection of adenovirus expressing Cre, while cancer development was observed at 6 months in adenovirus-Cre-injected BrafCA/wt;MieapKO/KO and BrafCA/wt;Atg5flox/flox mice [where autophagy-related 5 (ATG5) is a component of autophagic machinery], although KO of either molecule alone was not sufficient for cancer development. These data demonstrate that MIEAP or ATG5 KO accelerated thyroid cancer development. However, cancers in adenovirus-Cre-injected BrafCA/wt ;MieapKO/KO and BrafCA/wt ;Atg5flox/flox mice were not oncocytic. In conclusion, we here show that MIEAP and ATG5 are both tumor suppressors in thyroid carcinogenesis, but as we have anticipated from our previous data, KO of either molecule does not confer the oncocytic phenotype to BRAFV600E-positive thyroid cancers. The combination of disruptive mitochondrial function and impaired mitochondrial quality control may be necessary to establish a mouse model of thyroid oncocytoma.

Abstract 5806: Mieap forms membraneless organelles to compartmentalize and facilitate cardiolipin metabolism

Liquid droplets function as membraneless organelles that compartmentalize and facilitate efficient biological reactions. They are formed by proteins with intrinsically disordered regions (IDRs) via liquid-liquid phase separation. Mieap/SPATA18, a p53-inducible protein, participates in suppression of colorectal tumors by promoting mitochondrial quality control. However, the regulatory mechanism involved remains unclear. Here, we report that Mieap is an IDR-containing protein that drives formation of liquid droplets in mitochondria. Mieap liquid droplets specifically phase separate the mitochondrial phospholipid, cardiolipin. Lipidomic analysis of cardiolipin suggests that Mieap promotes enzymatic reactions involved in cardiolipin metabolism, including biosynthesis and remodeling. Accordingly, four cardiolipin biosynthetic enzymes, TAMM41, PGS1, PTPMT1, and CRLS1, and two remodeling enzymes, PLA2G6 and TAZ, are phase-separated by Mieap liquid droplets. Mieap-deficient mice exhibit altered crista structure in mitochondria of various tissues, including brown fat, and tend to become obese. These results suggest that Mieap drives formation of membraneless organelles to compartmentalize and promote cardiolipin metabolism at the inner mitochondrial membrane, thus potentially contributing to mitochondrial quality control.

Citation Format: Naoki Ikari, Yasuyuki Nakamura, Hirofumi Arakawa. Mieap forms membraneless organelles to compartmentalize and facilitate cardiolipin metabolism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5806.

First Application of Mass Measurements with the Rare-RI Ring Reveals the Solar r-Process Abundance Trend at A=122 and A=123

The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF-^{127}Sn, ^{126}In, ^{125}Cd, ^{124}Ag, ^{123}Pd-were injected in R3. Masses of ^{126}In, ^{125}Cd, and ^{123}Pd were measured whereby the mass uncertainty of ^{123}Pd was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new ^{123}Pd result on the solar r-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction Y_{e}. It is found that the neutron capture cross section on ^{123}Pd increases by a factor of 2.2 and β-delayed neutron emission probability, P_{1  n}, of ^{123}Rh increases by 14%. The neutron capture cross section on ^{122}Pd decreases by a factor of 2.6 leading to pileup of material at A=122, thus reproducing the trend of the solar r-process abundances. The trend of the two-neutron separation energies (S_{2n}) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S_{2n} value at N=77. Such large increase of the S_{2n} values before N=82 was proposed as an alternative to the quenching of the N=82 shell gap to reproduce r-process abundances in the mass region of A=112-124.

MIEAP, a p53-downstream gene, is associated with suppression of breast cancer cell proliferation and better survival

Mitochondria-eating protein (MIEAP; also known as SPATA18), a p53-downstream gene, is involved in mitochondrial quality control (MQC). Enforced MIEAP expression induces caspase-dependent cell death in vitro, and impairment of the p53/MIEAP-regulated MQC pathway is frequently observed in breast cancer (BC), resulting in poor disease-free survival (DFS). To investigate the clinical significance of MIEAP in BC, we identified 2,980 patients from two global, large-scale primary BC cohorts: the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC; n=1,904) and the Cancer Genome Atlas (TCGA; n=1,076). We divided patients in each cohort into high and low groups based on median gene expression levels and analyzed the association between MIEAP expression and clinical outcomes. Compared with normal tumors, MIEAP expression was significantly downregulated in all patients with p53-mutant BC regardless of subtype. MIEAP expression was negatively correlated with KI67 expression. Gene set enrichment analysis demonstrated that cell cycle- and proliferation-associated gene sets were significantly enriched in MIEAP-low tumors compared to MIEAP-high tumors. Patients with MIEAP-high luminal subtype were associated with significantly longer DFS than those with MIEAP-low luminal tumors in both cohorts, whereas significantly longer overall survival was observed only in the METABRIC cohort, which has roughly double the number of samples. These results indicated that the mechanistic role of MIEAP is clinically relevant in the two independent cohorts. This is the first study to use large cohorts to demonstrate the association between MIEAP expression and survival in patients with luminal subtype BC.

Bayesian inference of ion velocity distribution function from laser-induced fluorescence spectra

The velocity distribution function is a statistical description that connects particle kinetics and macroscopic parameters in many-body systems. Laser-induced fluorescence (LIF) spectroscopy is utilized to measure the local velocity distribution function in spatially inhomogeneous plasmas. However, the analytic form of such a function for the system of interest is not always clear under the intricate factors in non-equilibrium states. Here, we propose a novel approach to select the valid form of the velocity distribution function based on Bayesian statistics. We formulate the Bayesian inference of ion velocity distribution function and apply it to LIF spectra locally observed at several positions in a linear magnetized plasma. We demonstrate evaluating the spatial inhomogeneity by verifying each analytic form of the local velocity distribution function. Our approach is widely applicable to experimentally establish the velocity distribution function in plasmas and fluids, including gases and liquids.

Abstract 4786: Potential role of p53-Mieap-regulated mitochondrial quality control as a tumor suppressor in gastric and esophageal cancers Potential role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in gastric, esophageal and breast cancers

[Background] Despite its early diagnosis and improved intensive treatments, gastric cancer (GC) remains the third leading cause of death throughout the world. In particular among upper gastrointestinal cancers, it is most prevalent in eastern Asia including Japan, Korea, and China. p53 is a transcription factor that activates the expression of various downstream genes in response to DNA damage. The central functions of this protein in tumor suppression are cell cycle arrest, apoptosis, DNA repair, and anti-angiogenesis. Mitochondria-eating protein (Mieap) is a p53-target that plays an important role in mitochondrial quality control (MQC). Mieap has been reported to have a critical role in tumor suppression in colorectal and breast cancers. Here, we investigated its role as a tumor suppressor in gastric cancer (GC) and esophageal cancer (EC).

[Materials and Methods] To investigate the role of Mieap, Mieap-expressing adenovirus (Ad-Mieap) was used to infect GC cells, which were then analyzed by FACS, western blot, and caspase assays. Next, we evaluated the potential disruption of the p53-Mieap-regulated MQC pathway in vivo. Methylation-specific PCR (MPS) for Mieap, NIX, and BNIP3 promoters and p53 mutation detection were performed using genomic DNA from cryopreserved surgical specimens.

[Results] Exogenous Mieap in GC cells induced the formation of vacuole-like structures (called MIVs, Mieap-induced vacuoles) and caspase-dependent apoptosis, with the activation of both caspase-3 and caspase-9. In particular, NIX, a mitochondrial apoptotic factor was involved in this phenotype. Of 47 GC patient samples, promoter methylation of Mieap, BNIP3, and NIX was identified in two (4.3%), 29 (61.7%), and zero (0%) specimens, respectively. In total, 33 GC patient samples (70.2%) revealed inactivation of the p53/Mieap-regulated MQC pathway. Interestingly, we found that the BNIP3 promoter in the normal epithelium was highly methylated in 18 of 47 GC cases (38.3%). In EC patients, this MQC pathway was inactivated in ten of 12 patients (83.3%).

[Conclusion] These results indicate that p53/Mieap-regulated MQC has a critical role in not only breast cancer but also gastrointestinal cancer suppression, possibly in part through the mitochondrial apoptotic pathway.

Citation Format: Manabu Futamura, Hitoya Sano, Siqin Gaowa, Akira Nakakami, Kazuhiro Yoshida, Hirofumi Arakawa. Potential role of p53-Mieap-regulated mitochondrial quality control as a tumor suppressor in gastric and esophageal cancers Potential role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in gastric, esophageal and breast cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4786.

Swelling of Doubly Magic ^{48}Ca Core in Ca Isotopes beyond N=28

Interaction cross sections for ^{42-51}Ca on a carbon target at 280  MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N=28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N=28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare ^{48}Ca core in Ca isotopes beyond N=28.

Abstract 697: Degradation of cancer mitochondria by the mitochondria-eating protein induces iron-dependent cancer cell death

Parkin/Pink1-mediated mitophagy plays a critical role in mitochondrial quality control, in which the unhealthy mitochondria are sequestered by autophagosomes, and degraded by fusion between autophagosomes and lysosomes. Here, we report non-canonical mitophagy as a new function of tumor suppressor p53. The mitochondria-eating protein (Mieap) was originally identified as a p53-target gene. Mieap induced large vacuole-like structures (Mieap-induced vacuoles: MIVs) in cancer cells. MIVs were generated from around the mitochondria, and directly ate and degraded cancer mitochondria without autophagosomes. Therefore, we defined the function as the Mieap-regulated non-canonical mitophagy. UVRAG was found to be a Mieap-interacting protein that mediates the MIVs formation. Interestingly, degradation of cancer mitochondria by the MIVs induced cell death via iron-dependent production of reactive oxygen species. Introduction of exogenous Mieap strikingly suppressed in vivo tumor growth of Mieap-deficient colorectal cancer cells. Deficiency of endogenous Mieap dramatically promoted cancer development, malignancy, and aggressiveness in colorectal and gastric cancer model mice. The Mieap-induced cell death was found to occur in in vivo hypoxic tumor microenvironment of colorectal cancer tissues. These results suggest that degradation of cancer mitochondria by Mieap-regulated non-canonical mitophagy plays a critical role in p53 tumor suppression via iron-dependent cancer cell death.

Citation Format: Yasuyuki Nakamura, Naoki Ikari, Hirofumi Arakawa. Degradation of cancer mitochondria by the mitochondria-eating protein induces iron-dependent cancer cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 697.

K1 gene transformation activities in AIDS-related and classic type Kaposi's sarcoma: Correlation with clinical presentation

Kaposi's sarcoma-associated herpesvirus (KSHV) causes both AIDS-related Kaposi's sarcoma (KS) and classic KS, but their clinical presentations are different, and respective mechanisms remain to be elucidated. The KSHV K1 gene is reportedly involved in tumorigenesis through the immunoreceptor tyrosine-based activation motif (ITAM). Since we found the sequence variations in the K1 gene of KSHV isolated from AIDS-related KS and classic KS, we hypothesized that the transformation activity of the K1 gene contributes to the different clinical presentations. To evaluate our hypothesis, we compared the transformation activities of the K1 gene between AIDS-related KS and classic KS. We also analyzed ITAM activities and the downstream AKT and NF-κB. We found that the transformation activity of AIDS-related K1 was greater than that of classic K1, and that AIDS-related K1 induced higher ITAM activity than classic K1, causing more potent Akt and NF-κB activities. K1 downregulation by siRNA in AIDS-related K1 expressing cells induced a loss of transformation properties and decreased both Akt and NF-κB activities, suggesting a correlation between the transformation activity of K1 and ITAM signaling. Our study indicates that the increased transformation activity of AIDS-related K1 is associated with its clinical aggressiveness, whereas the weak transformation activity of classic type K1 is associated with a mild clinical presentation and spontaneous regression. The mechanism of spontaneous regression of classic KS may provide new therapeutic strategy to cancer.

Abstract P3-09-04: Possible role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in human breast cancer

[Background] In sporadic breast cancers, the most important gene is p53, given that it is a tumor suppressor gene and mutated in greater than 50% of human cancers. According to previous reports, p53 is also mutated in approximately 20–40% of breast cancers. Recent data from the cancer genome atlas (TCGA) revealed that 37% of breast cancer specimens had alterations in p53-particularly, 72% in (human epidermal growth factor) HER2-rich and 80% of basal-like breast cancer cases—indicating that it is a critical driver of tumor development even in breast cancer. p53 is clinically very important not only because of its high mutation rate but also because mutation is associated with more aggressive disease and worse overall survival. Mitochondria-eating protein (Mieap) is a p53-target gene that plays an important role in mitochondrial quality control. Mieap has been reported to have a critical role in tumorsuppression of colorectal cancer. Here, we investigated the role of Mieap as a tumorsuppressor in breast cancer. [Marerial and methods] We overexpressed Mieap using the constructed adenovirus in breast cancer cell lines such as MCF-7, SK-BR-3, and MDA-MB-231 cells. The percentages of cells in different cell cycle phases (subG1, G1, S, and G2/M) were determined using FACS analysis and also caspase activities (Caspase, 3/7, 9) were measured. Cleaved PARP, which is a marker of cells undergoing apoptosis, was detected by western blot. For in vivo experiments, we examined the expression of Mieap using surgical specimens (invasive ductal carcinomas (IDCs): 75, ductal carcinoma in situ (DCIS): 27, fibroadenomas (FAs): 18) by immunohistochemistry. Next, we performed methylation-specific PCR (MSP) for Mieap, NIX, and BNIP3 promoters and p53-mutation search using 46 samples that were cryopreserved, among 75 IDC cases used for immunohistochemistry. These studies were approved by the central ethics committee of Gifu University.[Results] The enforced-expression of exogenous Mieap in breast cancer cells induced caspase-dependent apoptosis, with activation of both caspase-3/7 and caspase-9. Immunohistochemistry revealed endogenous Mieap in the cytoplasm in 24/75 (32%) invasive ductal carcinomas (IDCs), 15/27 (55.6%) cases of ductal carcinoma in situ (DCIS), and 16/18 (88.9%) fibroadenomas (FAs) (IDC vs DCIS; p = 0.0389, DCIS vs FA; p = 0.0234, IDC vs FA; p < 0.0001). In IDCs, the Mieap promoter was methylated in 6/46 (13%) cases whereas p53 was mutated in 6/46 (13%) cases. Therefore, the p53/Mieap-regulated mitochondrial quality control pathway was inactivated in 12/46 IDCs (26.1%). Interestingly, all of the tumors derived from the 12 patients with the Mieap-promoter methylation or p53 mutation pathologically exhibited more aggressive and malignant phenotype of breast cancers, resulting in significantly shorter disease-free survival (DFS) (p = 0.021). [Conclusion]These results indicate that p53/Mieap-regulated mitochondrial quality control has a critical role in tumor suppression of breast cancer, possibly in part, through mitochondrial apoptotic pathway.

Citation Format: Futamura M, Gaowa S, Arakawa H, Yoshida K. Possible role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in human breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-09-04.

Possible role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in human breast cancer

Mitochondria‐eating protein (Mieap), encoded by a p53‐target gene, plays an important role in mitochondrial quality control (MQC). Mieap has been reported to have a critical role in tumor suppression in colorectal cancer. Here, we investigated its role as a tumor suppressor in breast cancer. The enforced expression of exogenous Mieap in breast cancer cells induced caspase‐dependent apoptosis, with activation of both caspase‐3/7 and caspase‐9. Immunohistochemistry revealed endogenous Mieap in the cytoplasm in 24/75 (32%) invasive ductal carcinomas (IDC), 15/27 (55.6%) cases of ductal carcinoma in situ (DCIS) and 16/18 (88.9%) fibroadenomas (FA) (IDC vs DCIS; P = 0.0389, DCIS vs FA; P = 0.0234, IDC vs FA; P < 0.0001). In IDC, the Mieap promoter was methylated in 6/46 (13%) cases, whereas p53 was mutated in 6/46 (13%) cases. Therefore, the p53/Mieap‐regulated MQC pathway was inactivated in 12/46 IDC (26.1%). Interestingly, all tumors derived from the 12 patients with Mieap promoter methylation or p53 mutations pathologically exhibited more aggressive and malignant breast cancer phenotypes. Impairment of p53/Mieap‐regulated MQC pathway resulted in significantly shorter disease‐free survival (DFS) (P = 0.021), although p53 status is more prognostic in DFS than Mieap promoter methylation. These results indicate that p53/Mieap‐regulated MQC has a critical role in tumor suppression in breast cancer, possibly in part through mitochondrial apoptotic pathway.

INVESTIGATION OF A PRACTICAL PATIENT DOSE INDEX FOR ASSESSMENT OF PATIENT ORGAN DOSE FROM CONE-BEAM COMPUTED TOMOGRAPHY IN RADIATION THERAPY USING A MONTE CARLO SIMULATION

The purpose of this study was to investigate a practical patient dose index for assessing the patient organ dose from a cone-beam computed tomography (CBCT) scan by comparing eight dose indices, i.e. CTDI100, CTDIIEC, CTDI∞, midpoint doses f(0)PMMA for a cylindrical polymethyl methacrylate (PMMA) phantom, f(0)Ap for an anthropomorphic phantom and f(0)Pat for a prostate cancer patient, as well as the conventional size specific dose estimations (SSDEconv) and modified SSDE (SSDEmod), with organ dose for the prostate (ODprost) obtained via Monte Carlo (MC) simulation. The ODprost was the reference dose used to find the practical dose index at the center of the pelvic region of a prostate cancer patient. The smallest error rate with respect to the ODprost of 19.3 mGy (reference) among eight dose indices was 5% for f(0)Pat. The practical patient dose index was the f(0)Pat, which showed the smallest error with respect to the reference dose.

Induction of non-apoptotic programmed cell death by oncogenic RAS in human epithelial cells and its suppression by MYC overexpression

Oncogenic mutations of RAS genes, found in about 30% of human cancers, are considered to play important roles in cancer development. However, oncogenic RAS can also induce senescence in mouse and human normal fibroblasts. In some cell lines, oncogenic RAS has been reported to induce non-apoptotic programed cell death (PCD). Here, we investigated effects of oncogenic RAS expression in several types of normal human epithelial cells. Oncogenic RAS but not wild-type RAS stimulated macropinocytosis with accumulation of large-phase lucent vacuoles in the cytoplasm, subsequently leading to cell death which was indistinguishable from a recently proposed new type of PCD, methuosis. A RAC1 inhibitor suppressed accumulation of macropinosomes and overexpression of MYC attenuated oncogenic RAS-induced such accumulation, cell cycle arrest and cell death. MYC suppression or rapamycin treatment in some cancer cell lines harbouring oncogenic mutations in RAS genes induced cell death with accumulation of macropinosomes. These results suggest that this type of non-apoptotic PCD is a tumour-suppressing mechanism acting against oncogenic RAS mutations in normal human epithelial cells, which can be overcome by MYC overexpression, raising the possibility that its induction might be a novel approach to treatment of RAS-mutated human cancers.

Abstract 2329: Noncanonical mitophagy induced by Mieap and its role in tumor suppression via ferroptosis-like cell death

Parkin/Pink1-mediated mitophagy plays a critical role in mitochondrial quality control, in which the damaged mitochondria are sequestered by autophagosomes, and degraded by fusion between autophagosomes and lysosomes. Here, we report Mieap-mediated noncanonical mitophagy as a new function of tumor suppressor p53. Mieap was originally identified as a p53-target gene. Overexpression of exogenous Mieap induces large vacuoles in cancer cells. Mieap-induced vacuoles are generated from the mitochondria, and directly eat and degrade the cancer mitochondria. UVRAG regulates the Mieap-mediated noncanonical mitophagy. Surprisingly, Mieap-mediated noncanonical mitophagy induces cell death via the iron-dependent production of reactive oxygen species (ROS). Introduction of exogenous Mieap strikingly suppresses in vivo tumor growth of Mieap-deficient colorectal cancer cells. Deficiency of endogenous Mieap dramatically promotes cancer development, malignancy, and aggressiveness in colorectal and gastric cancer model mice. The cell death induced by Mieap-mediated noncanonical mitophagy occurs via the ROS production in in vivo hypoxic tumor microenvironment. These results suggest that Mieap-mediated noncanonical mitophagy plays a critical role in tumor suppression via ferroptosis-like cell death.

Citation Format: Yasuyuki Nakamura, Makoto Yamamoto, Hirofumi Arakawa. Noncanonical mitophagy induced by Mieap and its role in tumor suppression via ferroptosis-like cell death [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2329.

Survivin: A novel marker and potential therapeutic target for human angiosarcoma

Human angiosarcoma is a rare malignant vascular tumor associated with extremely poor clinical outcome and generally arising in skin of the head and neck region. However, little is known about the molecular pathogeneses and useful immunohistochemical markers of angiosarcoma. To investigate the mechanisms of angiosarcoma progression, we collected 85 cases of human angiosarcoma specimens with clinical records and analyzed ISO-HAS-B patient-derived angiosarcoma cells. As control subjects, 54 cases of hemangioma and 34 of pyogenic granuloma were collected. Remarkably, consistent with our recent observations regarding the involvement of survivin expression following Hippo pathway inactivation in the neoplastic proliferation of murine hemangioendothelioma cells and human infantile hemangioma, nuclear survivin expression was observed in all cases of angiosarcoma but not in hemangiomas and pyogenic granulomas, and the Hippo pathway was inactivated in 90.3% of yes-associated protein (YAP) -positive angiosarcoma cases. However, survivin expression modes and YAP localization (Hippo pathway activation modes) were not correlated with survival. In addition, we confirmed that survivin small interference RNA (siRNA) transfection and YM155, an anti-survivin drug, elicited decreased nuclear survivin expression and cell proliferation in ISO-HAS-B cells which expressed survivin consistently. Conclusively, these findings support the importance of survivin as a good marker and critical regulator of cellular proliferation for human angiosarcoma and YM155 as a potential therapeutic agent.

Discovery of Mieap-regulated mitochondrial quality control as a new function of tumor suppressor p53

The tumor suppressor p53 gene is frequently mutated in human cancers, and the p53 protein suppresses cancer. However, the mechanism behind the p53-mediated tumor suppression is still unclear. Recently, the mitochondria-eating protein (Mieap) was identified as a p53-inducible protein. Mieap induces the accumulation of lysosomal proteins within mitochondria (Mieap-induced accumulation of lysosome-like organelles within mitochondria, or MALM) in response to mitochondrial damage, and eliminates the oxidized mitochondrial proteins to repair unhealthy mitochondria. Furthermore, Mieap also induces vacuole-like structures (Mieap-induced vacuole, or MIV) to eat and degrade unhealthy mitochondria. Therefore, Mieap controls mitochondrial quality by repairing or eliminating unhealthy mitochondria by MALM or MIV, respectively. This mechanism is not mediated by canonical autophagy. Mieap-deficient Apc^Min/+ mice show strikingly high rates of intestinal tumor development as well as advanced-grade adenomas and adenocarcinomas. The p53/Mieap/BCL2 interacting protein 3 mitochondrial quality control pathway is frequently inactivated in human colorectal cancers. Defects in Mieap-regulated mitochondrial quality control lead to accumulation of unhealthy mitochondria in cancer cells. Cancer-specific unhealthy mitochondria could contribute to cancer development and aggressiveness through mitochondrial reactive oxygen species and altered metabolism. Mieap-regulated mitochondrial quality control is a newly discovered function of p53 that plays a critical role in tumor suppression.

Note: Optimization of magnifying a polarization angle with Littrow layout blazed gratings

Magnification of a polarization angle with Littrow layout gratings has been developed. High magnification with a factor of 7.7 using two gratings in Littrow layout was experimentally proved. The magnification range was investigated by calculation at a wavelength of 10.6 μm. The method can be applied for a high magnification factor >30. Larger groove numbers and smaller blaze angles are suitable for the large magnification. Statistical fluctuation of the diffracted polarization angle is compared with that of the incident polarization angle.

Hypermutation and unique mutational signatures of occupational cholangiocarcinoma in printing workers exposed to haloalkanes

Cholangiocarcinoma is a relatively rare cancer, but its incidence is increasing worldwide. Although several risk factors have been suggested, the etiology and pathogenesis of the majority of cholangiocarcinomas remain unclear. Recently, a high incidence of early-onset cholangiocarcinoma was reported among the workers of a printing company in Osaka, Japan. These workers underwent high exposure to organic solvents, mainly haloalkanes such as 1,2-dichloropropane (1,2-DCP) and/or dichloromethane. We performed whole-exome analysis on four cases of cholangiocarcinoma among the printing workers. An average of 44.8 somatic mutations was detected per Mb in the genome of the printing workers' cholangiocarcinoma tissues, approximately 30-fold higher than that found in control common cholangiocarcinoma tissues. Furthermore, C:G-to-T:A transitions with substantial strand bias as well as unique trinucleotide mutational changes of GpCpY to GpTpY and NpCpY to NpTpY or NpApY were predominant in all of the printing workers' cholangiocarcinoma genomes. These results were consistent with the epidemiological observation that they had been exposed to high concentrations of chemical compounds. Whole-genome analysis of Salmonella typhimurium strain TA100 exposed to 1,2-DCP revealed a partial recapitulation of the mutational signature in the printing workers' cholangiocarcinoma. Although our results provide mutational signatures unique to occupational cholangiocarcinoma, the underlying mechanisms of the disease should be further investigated by using appropriate model systems and by comparison with genomic data from other cancers.

A Concept of Cross-Ferroic Plasma Turbulence

The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux.

Abstract 318: Specific role of Mieap α in Mieap-induced vacuole generation through an interaction with UVRAG

Mieap, a p53-inducible protein, controls mitochondrial quality by repairing or eliminating unhealthy mitochondria via Mieap-induced accumulation of lysosome-like organelles within mitochondria (MALM) or Mieap-induced vacuole (MIV), respectively (1-4). BNIP3 and NIX are essential mediators of MALM. MIV generation is closely related to the endocytic pathway. However, the mechanism of MALM and MIV function and of their selection and regulation remains unclear. UVRAG was identified as a Mieap-interacting protein. UVRAG plays a role in canonical autophagy through the endocytic pathway. Interestingly, Mieap α, but not Mieap β, specifically interacts with UVRAG. Knockdown of UVRAG severely inhibited MIV generation induced by Mieap α. On the other hand, endogenous Mieap β, but not Mieap α, accumulated at and within mitochondria during the MALM process. These results, taken together, suggest that Mieap α has a specific role in MIV generation through an interaction with UVRAG by regulating the endocytic pathway. In addition, UVRAG and Mieap are inactivated in human cancers including colorectal cancer patients, suggesting that the MIV regulated by the interaction of Mieap and UVRAG may play a role in tumor suppression. In this paper, we discuss several possible mechanisms for the selection of MALM or MIV and the role of Mieap/UVRAG in tumorigenesis on the basis of our recent data.

1. Miyamoto Y et al. PLoS ONE 6: e16054, 2011

2. Kitamura N et al. PLoS ONE 6: e16060, 2011

3. Nakamura Y et al. PLoS ONE 7: e30767, 2012

4. Miyamoto T et al. Sci Rep 2: 379, 2012

Citation Format: Yasuyuki Nakamura, Hiroki Kamino, Yuri Saito, Noriaki Kitamura, Hitoya Sano, Hirofumi Arakawa. Specific role of Mieap α in Mieap-induced vacuole generation through an interaction with UVRAG. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 318. doi:10.1158/1538-7445.AM2014-318

Abstract 2465: p53-dependent and independent functions of Mieap

Mieap, a p53-inducible protein, plays a pivotal role in mitochondrial quality control (MQC) by repairing or eliminating unhealthy mitochondria1-4. To investigate physiological significance of the Mieap-regulated MQC, we generated and analyzed the Mieap-KO mice. (1) p53-dependent: Hypoxia induced Mieap expression and accumulation of lysosomal proteins within mitochondria in WT MEFs, but not Mieap-/- and p53-/- MEFs. Mieap-/- and p53-/- MEFs exhibited accumulation of oxidized mitochondrial proteins and increased ROS generation by unhealthy mitochondria under hypoxia, which enhanced cell migration and invasion. (2) p53-dependent: Mieap+/- / ApcMIN/+ mice displayed a shortening of the lifetime, compared to the ApcMIN/+ mice (average life-span: Mieap+/- / ApcMIN/+ mice vs ApcMIN/+ mice = 19.1 weeks vs 24.4 weeks), suggesting that Mieap deficiency may affect intestinal tumorigenesis. (3) p53-independent: Mieap was highly expressed in the midpiece, where the sperm mitochondria are localized, of the sperm in WT mice. This Mieap expression was independent on p53. Mieap-/- mice are fertile in vivo. However, in vitro fertilization of Mieap-/- sperm was severely impaired because of a failure of sperm motility. The oxidized proteins were dramatically accumulated in the midpiece of Mieap-/- sperm. These results, taken together, suggest that Mieap plays a crucial role in protection of the cell against oxidative stresses probably through its MQC function. This may also largely contribute to p53 tumor suppression.

1. Miyamoto Y et al. PLoS ONE 6: e16054, 2011

2. Kitamura N et al. PLoS ONE 6: e16060, 2011

3. Nakamura Y et al. PLoS ONE 7: e30767, 2012

4. Miyamoto T et al. Sci Rep 2: 379, 2012

Citation Format: Yasuyuki Nakamura, Hiroki Kamino, Yuri Saito, Hitoya Sano, Hirofumi Arakawa. p53-dependent and independent functions of Mieap. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2465. doi:10.1158/1538-7445.AM2014-2465

Note: Magnification of a polarization angle with a Littrow layout brazed grating

A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ~2.7 has been demonstrated for a 10.6 μm CO2 laser beam as expected from a calculation. The method is applicable in many polarimetry fields.

Natural course of dissecting vertebrobasilar artery aneurysms without stroke

BACKGROUND AND PURPOSE

The natural history and therapeutic management of dissecting vertebrobasilar aneurysms without ischemic or hemorrhagic stroke (nonstroke dissecting vertebrobasilar aneurysms) are not well-established. We conservatively followed patients with nonstroke dissecting vertebrobasilar aneurysms and evaluated the factors related to clinical and morphologic deterioration.

MATERIALS AND METHODS

One hundred thirteen patients were enrolled and divided by clinical presentation at diagnosis: asymptomatic (group 1, n = 52), pain only (group 2, n = 56), and mass effect (group 3, n = 5). Patients were conservatively managed without intervention and antithrombotic therapy. Clinical outcomes and morphologic changes were analyzed.

RESULTS

A total of 113 patients who were diagnosed with nonstroke dissecting vertebrobasilar aneurysm had a mean follow-up of 2.9 years (range, 27 days to 8 years). Throughout that period, 1 patient in group 1 (1.9%) and 1 patient in group 2 (1.8%) showed clinical deterioration due to mass effect, and 1 patient in group 3 (20%) developed ischemic stroke followed by subarachnoid hemorrhage. Most patients (97.3%) were clinically unchanged. Three patients who had clinical deterioration showed aneurysm enlargement (P < .001). Aneurysms remained morphologically unchanged in 91 patients (80.5%). Aneurysm enlargement was seen in 5 patients (4.4%); risk of enlargement was significantly associated with either maximum diameter (hazard ratio = 1.30; 95% CI, 1.11-11.52; P = .001) or aneurysm ≥10 mm (hazard ratio = 18.0; 95% CI, 1.95-167; P = .011).

CONCLUSIONS

The natural course of these lesions suggests that acute intervention is not always required and close follow-up without antithrombotic therapy is reasonable. Patients with symptoms due to mass effect or aneurysms of >10 mm may require treatment.

Validation and initial application of a semiautomatic aneurysm measurement software: a tool for assessing volumetric packing attenuation

BACKGROUND AND PURPOSE

Precise aneurysm measurements and volume embolization ratios are essential for long-term durability of endovascular coil embolization. We evaluated the accuracy of newly developed semiautomatic cerebral aneurysm measurement software, NeuroVision, and explored the value of volume embolization ratio in the prediction of re-treatment.

MATERIALS AND METHODS

We compared software-derived volume measurements of 4 silicone aneurysm models with those calculated with an approximation formula and ground truth values (validation study). We used NeuroVision to retrospectively evaluate outcomes of 100 unruptured aneurysms (97 patients) treated with embolization (clinical study). Aneurysm size (height, width, and neck), volume, and volume embolization ratios were calculated for 3 groups (stable, recanalization, and re-treatment) and were compared.

RESULTS

This validation study illustrated higher accuracy of NeuroVision in computing aneurysm volume compared with an approximation formula: percentage absolute errors were 4.50% ± 3.18% and 23.07% ± 17.60%, with maximal percentage absolute errors of 8.99% and 45.63%, respectively. Of 100 unruptured aneurysms, 20 recanalized and 12 were re-treated. Average volume embolization ratios of stable and re-treated aneurysms were 24.88% ± 5.91% and 20.50% ± 4.06%, respectively (P ≤ .01). The optimal volume embolization ratio cutoff point for re-treatment was < 19.15%, at which the Youden index was 0.50 (sensitivity, 58.33%; specificity, 87.50%; area under the receiver operating characteristic curve, 0.74).

CONCLUSIONS

The NeuroVision software provided accurate aneurysm volume measurements and may be a useful standardized tool to measure aneurysm size and volume, especially for multicenter clinical studies. Volume embolization ratio may be a valuable predictor of aneurysm occlusion changes.

Dependence receptor UNC5D mediates nerve growth factor depletion-induced neuroblastoma regression

Spontaneous regression of neuroblastoma (NB) resembles the developmentally regulated programmed cell death (PCD) of sympathetic neurons. Regressing tumor cells express high levels of the nerve growth factor (NGF) receptors TRKA and p75NTR and are dependent on NGF for survival; however, the underlying molecular mechanism remains elusive. Here, we show that UNC5D, a dependence receptor that is directly targeted by p53 family members, is highly expressed in favorable NBs. NGF withdrawal strongly upregulated UNC5D, E2F1, and p53 in human primary favorable NBs. The induced UNC5D was cleaved by caspases 2/3, and the released intracellular fragment translocated into the nucleus and interacted with E2F1 to selectively transactivate the proapoptotic target gene. The cleavage of UNC5D and its induction of apoptosis were strongly inhibited by addition of netrin-1. Unc5d(-/-) mice consistently exhibited a significant increase in dorsal root ganglia neurons and resistance to NGF depletion-induced apoptosis in sympathetic neurons compared with wild-type cells. Our data suggest that UNC5D forms a positive feedback loop with p53 and E2F1 to promote NGF dependence-mediated PCD during NB regression.

'I-shaped' sign in the upper mediastinum: a novel potential marker for antenatal diagnosis of d-transposition of the great arteries

OBJECTIVES

To investigate the 'I-shaped' sign as a novel echocardiographic marker for antenatal diagnosis of d-transposition of the great arteries (dTGA) in routine cardiac examination, and to compare its prevalence in fetuses with dTGA, those with other congenital heart diseases (CHDs) and those with normal structural hearts.

METHODS

This retrospective evaluation involved 1134 fetuses undergoing echocardiography to screen for CHD over a 4-year period. I-shaped sign was defined as the characteristic appearance of the aortic arch, resembling the letter 'I', from the most anterior to the most posterior point of the descending aorta visible in the three vessels and trachea view. The frequency of this sign was evaluated in cases with dTGA, those with other cardiac defects and those with normal cardiac structures.

RESULTS

CHD was diagnosed in 671 (59.1%) cases, of which 31 (4.6%) had dTGA. I-shaped sign was observed in 30/31 (96.8%) cases of dTGA, compared with 31/640 (4.8%) cases with other cardiac anomalies, which included single ventricle with pulmonary atresia or severe pulmonary stenosis, hypoplastic left heart syndrome with aortic atresia, corrected transposition of the great arteries, and double outlet right ventricle with malposition of the great arteries. I-shaped sign was detected significantly more frequently in the dTGA group compared with the normal group and with the other CHDs group (both P < 0.001) and had 96.8% sensitivity and 97.1% specificity for diagnosis of dTGA. Importantly, I-shaped sign was never observed in fetuses with structurally normal hearts.

CONCLUSIONS

Detection on echocardiography of an extremely long vessel with a marked I-shape should raise suspicion of cardiac anomaly, especially dTGA. This marker may therefore aid in the prenatal diagnosis of dTGA during routine ultrasound examination.

Abstract LB-131: Mieap, a p53-inducible protein, controls mitochondrial quality by repairing or eliminating unhealthy mitochondria

The accumulation of unhealthy mitochondria results in mitochondrial dysfunction, which has been implicated in aging, cancer, and a variety of degenerative diseases. However, the mechanism by which mitochondrial quality is regulated remains unclear. Here, we show that Mieap, a novel p53-inducible protein, plays a critical role in mitochondrial quality control. Mieap expression is directly regulated by p53 and is frequently lost in human cancer as result of DNA methylation. Mieap dramatically induces the accumulation of lysosomal proteins within mitochondria and mitochondrial acidic condition without destroying the mitochondrial structure (designated MALM, for Mieap-induced accumulation of lysosome-like organelles within mitochondria) in response to mitochondrial damage. MALM is involved in the degradation of oxidized mitochondrial proteins, leading to increased ATP synthesis and decreased reactive oxygen species generation. However, when MALM is inhibited, Mieap induces vacuole-like structures (designated as MIV for Mieap-induced vacuole), which engulf and degrade the unhealthy mitochondria by accumulating lysosomes. The inactivation of p53 severely impairs both MALM and MIV generation. These results suggest that Mieap plays a pivotal role in mitochondrial quality control by repairing or eliminating unhealthy mitochondria via MALM or MIV generation, respectively. Cancer cells might accumulate unhealthy mitochondria due to p53 mutations and/or Mieap methylation, representing a potential cause of the Warburg effect.

Citation Format: Yasuyuki Nakamura, Hiroki Kamino, Hitoya Sano, Hirofumi Arakawa. Mieap, a p53-inducible protein, controls mitochondrial quality by repairing or eliminating unhealthy mitochondria. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-131. doi:10.1158/1538-7445.AM2013-LB-131

Abstract LB-132: Frequent inactivation of the p53/Mieap/BNIP3 mitochondrial quality control pathway in gastric cancer

Recently, we discovered a novel mechanism for mitochondrial quality control (MQC), in which Mieap, a p53-inducible protein, controls MQC by repairing or eliminating unhealthy mitochondria via MALM (Mieap-induced Accumulation of Lysosome-like organelles within Mitochondria) or MIV (Mieap-Induced Vacuole) generation, respectively (1, 2). We also reported that two mitochondrial outer membrane proteins, BNIP3 and NIX, are essential mediators of the MALM (2, 3). To examine the role of Mieap-regulated MQC pathway in tumorigenesis, we analyzed the status of p53, Mieap, BNIP3, and NIX in 50 cases of primary gastric cancer. Of the 50 patients, Mieap and BNIP3 promoter methylation was observed in 2 (4%) and 29 (58%) patients, respectively. A p53 mutation was detected in 2 (10%) of the 20 patients with either Mieap or BNIP3 promoter methylation whereas it was found in 3 (15.8%) of the 19 patients with neither Mieap nor BNIP3 promoter methylation, implying that the p53/Mieap/BNIP3 MQC pathway is inactivated in at least 70% of gastric cancer cases. In a colorectal cancer cell line, hypoxia induced MALM. Knockdown of p53, Mieap, or BNIP3 in the cell line severely inhibited hypoxia-induced MALM, leading to the accumulation of unhealthy mitochondria and increased mitochondrial reactive oxygen species (mtROS) generation. Furthermore, the mtROS dramatically enhanced cancer migration and invasion in hypoxic conditions. These results suggest that the p53/Mieap/BNIP3 MQC pathway plays a tumor-suppressive role in gastric cancer.

1. Miyamoto Y et al. PLoS ONE 6: e16054, 2011

2. Kitamura N et al. PLoS ONE 6: e16060, 2011

3. Nakamura Y et al. PLoS ONE 7: e30767, 2012

Citation Format: Hitoya Sano, Hiroki Kamino, Yasuyuki Nakamura, Masaki Yoshida, Ryuya Murai, Yuri Saito, Manabu Futamura, Kazuhiro Yoshida, Hirofumi Arakawa. Frequent inactivation of the p53/Mieap/BNIP3 mitochondrial quality control pathway in gastric cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-132. doi:10.1158/1538-7445.AM2013-LB-132

Abstract 1900: Hypoxia induces accumulation of lysosomal proteins within mitochondria

Mitochondrial quality control (MQC) plays a critical role in maintaining a healthy status of mitochondria, preventing aging, cancer, and a variety of degenerative diseases. However, the mechanism largely remains unclear. Recently, we discovered a novel MQC mechanism regulated by Mieap, a p53-inducible protein, in which Mieap induces intramitochondrial lysosome-like organella that plays a critical role in the elimination of oxidized mitochondrial proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) in response to mitochondrial damage (1-4). Here, we report a physiological role of the MALM function. Hypoxia dramatically induced accumulation of lysosomal proteins within mitochondria without the destruction of mitochondrial structure in both human normal mammary epithelial cells (HMEC4s) and mouse embryonic fibroblasts cells (MEFs). In response to the hypoxic stress, the MALM was inducible in ATG5-KO, ATG7-KO, and PINK1-KO MEFs, but not in p53-KO and Mieap-KO MEFs, suggesting that the phenomenon is completely different from canonical autophagy. In the MALM-deficient cells, hypoxia caused an increase of mitochondrial reactive oxygen species (ROS) generation and accumulation of oxidized proteins within the mitochondria. Surprisingly, the MALM-deficient cells in the hypoxic condition revealed enhanced activities of cell migration and invasion. This phenotype was totally cancelled by a ROS scavenger reagent, Ebselen. These results suggest that the MALM is a universal and fundamental function in the cell (at least from mouse to human), which plays a critical role in MQC under hypoxia. Alteration of the MALM function in cancer cells could facilitate cancer invasion and metastasis via mitochondrial ROS generated by unhealthy mitochondria.

1. Miyamoto Y et al. PLoS ONE 6: e16054, 2011

2. Kitamura N et al. PLoS ONE 6: e16060, 2011

3. Nakamura Y et al. PLoS ONE 7: e30767, 2012

4. Miyamoto T et al. Sci Rep 2: 379, 2012

Citation Format: Yasuyuki Nakamura, Masaki Yoshida, Noriaki Kitamura, Hiroki Kamino, Ryuya Murai, Yuri Saito, Hitoya Sano, Hirofumi Arakawa. Hypoxia induces accumulation of lysosomal proteins within mitochondria. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1900. doi:10.1158/1538-7445.AM2013-1900

Justification of unruptured intracranial aneurysm repair: a single-center experience

BACKGROUND AND PURPOSE

Whether to treat UIAs is controversial. The aim of the study was to compare the clinical outcome of patients with UIAs who were either treated conservatively or preventively.

MATERIALS AND METHODS

Patients with UIAs referred to our institution were prospectively enrolled in the study. Data collected included baseline characteristics, aneurysmal features, and procedural and follow-up information. Preventive treatment was recommended if the aneurysm was larger than 5 mm and was considered safely treatable. Endovascular surgery was the first-line therapy if the aneurysmal shape was appropriate for coiling.

RESULTS

From January 2003 through April 2008, a total of 879 patients with 1110 UIAs were enrolled; 325 patients with 369 UIAs (mean size, 7.8 mm) were treated (treatment group), and 603 patients with 741 UIAs (mean size, 4.4 mm) were managed conservatively (observation group). Mean follow-up was 692.5 days (1405.5 person-years). In the observation group, 26 aneurysms (3.5%) had ruptured (1.8% per year; 1405.5 person-years), 10 patients died, and 7 were disabled (mRS, 3-6: 2.8%). Aneurysmal size was a significant risk factor for rupture (P = .001). The treatment group included aneurysms treated either with coiling (n=315), clipping (n=32), or a combined approach (n=9); 1 patient died, and 3 were disabled (mRS, 3-6: 1.2%). Therapeutic intervention was equal (UIAs of all sizes) or superior (UIAs > 5 mm; P = .025) to conservative management.

CONCLUSIONS

Treatment of UIAs was justified in aneurysms larger than 5 mm, and EVS can be safely applied to nearly 90% of UIAs.

Development of a novel telomerase assay using the PPDK-luciferin-luciferase detection system

Telomerase participates in malignant transformation or immortalization of cells, and has attracted attention as an anticancer drug screening and diagnostic tumor marker. We developed a novel telomerase assay called the PPDK-luciferin-luciferase system bioluminescence assay (PLLBA) using pyruvate phosphate dikinase (PPDK). In this assay, pyrophosphate produced by the telomerase reaction and polymerase chain reaction (PCR) is converted to ATP by PPDK, and ATP is detected by the firefly luciferin-luciferase reaction. In this work, telomerase substrate was obtained in accordance with the telomeric repeat amplification protocol (TRAP). Telomerase-positive (500 cells/assay), -inactive (heated for 10 min at 85 °C) and -negative (only Chaps lysis buffer) samples were used. As a result, the findings clearly showed that the signal-to-noise (S/N) ratio of the positive cells was 39.5. After the telomerase reaction and PCR, PLLBA was completed ~ 120 s later. A high level of reproducibility was obtained with - coefficient of variation (CV) of 4.1% (positive cells). The detection limit for cells using telomerase was one cell per assay. This assay for telomerase activity was also shown to be adaptable to human cancer-derived cell lines.

Identification of errors in the electron density measurements of a tangential interferometer∕polarimeter system during a tokamak discharge

A new method for the comparative verification of electron density measurements obtained with a tangential interferometer and a polarimeter during a discharge is proposed. The possible errors associated with the interferometer and polarimeter are classified by the time required for their identification. Based on the characteristics of the errors, the fringe shift error of the interferometer and the low-frequency noise of the polarimeter were identified and corrected for the JT-60U tangential interferometer∕polarimeter system.

International consensus on (ICON) pediatric asthma

Asthma is the most common chronic lower respiratory disease in childhood throughout the world. Several guidelines and/or consensus documents are available to support medical decisions on pediatric asthma. Although there is no doubt that the use of common systematic approaches for management can considerably improve outcomes, dissemination and implementation of these are still major challenges. Consequently, the International Collaboration in Asthma, Allergy and Immunology (iCAALL), recently formed by the EAACI, AAAAI, ACAAI, and WAO, has decided to propose an International Consensus on (ICON) Pediatric Asthma. The purpose of this document is to highlight the key messages that are common to many of the existing guidelines, while critically reviewing and commenting on any differences, thus providing a concise reference. The principles of pediatric asthma management are generally accepted. Overall, the treatment goal is disease control. To achieve this, patients and their parents should be educated to optimally manage the disease, in collaboration with healthcare professionals. Identification and avoidance of triggers is also of significant importance. Assessment and monitoring should be performed regularly to re-evaluate and fine-tune treatment. Pharmacotherapy is the cornerstone of treatment. The optimal use of medication can, in most cases, help patients control symptoms and reduce the risk for future morbidity. The management of exacerbations is a major consideration, independent of chronic treatment. There is a trend toward considering phenotype-specific treatment choices; however, this goal has not yet been achieved.

BNIP3 and NIX mediate Mieap-induced accumulation of lysosomal proteins within mitochondria

Mieap, a p53-inducible protein, controls mitochondrial quality by repairing unhealthy mitochondria. During repair, Mieap induces the accumulation of intramitochondrial lysosomal proteins (designated MALM for Mieap-induced accumulation of lysosome-like organelles within mitochondria) by interacting with NIX, leading to the elimination of oxidized mitochondrial proteins. Here, we report that an additional mitochondrial outer membrane protein, BNIP3, is also involved in MALM. BNIP3 interacts with Mieap in a reactive oxygen species (ROS)-dependent manner via the BH3 domain of BNIP3 and the coiled-coil domains of Mieap. The knockdown of endogenous BNIP3 expression severely inhibited MALM. Although the overexpression of either BNIP3 or NIX did not cause a remarkable change in the mitochondrial membrane potential (MMP), the co-expression of all three exogenous proteins, Mieap, BNIP3 and NIX, caused a dramatic reduction in MMP, implying that the physical interaction of Mieap, BNIP3 and NIX at the mitochondrial outer membrane may regulate the opening of a pore in the mitochondrial double membrane. This effect was not related to cell death. These results suggest that two mitochondrial outer membrane proteins, BNIP3 and NIX, mediate MALM in order to maintain mitochondrial integrity. The physical interaction of Mieap, BNIP3 and NIX at the mitochondrial outer membrane may play a critical role in the translocation of lysosomal proteins from the cytoplasm to the mitochondrial matrix.

Observation of long-distance radial correlation in toroidal plasma turbulence

This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of ∼1-3  kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n=1/1 (or 2/1), and an amplitude of ∼2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity.

Identification of NEEP21, encoding neuron-enriched endosomal protein of 21 kDa, as a transcriptional target of tumor suppressor p53

NEEP21, also designated D4S234E or NSG1, is an endosomal protein expressed in neuronal cells under normal conditions. Here, we report that NEEP21 is a direct transcriptional target gene of the tumor suppressor p53. NEEP21 expression is inducible in non-neuronal human cancer cell lines by exposure to adriamycin, hydrogen peroxide, UV and γ-ray in a p53-dependent manner. Chromatin immunoprecipitation assay indicated that a potential p53-binding site (p53BS) is located in intron 1 of the NEEP21 gene. A reporter assay confirmed that p53BS has p53-responsive activity. The heterologous luciferase gene containing p53BS is also transactivated by p73-β and p63-γ. The introduction of the NEEP21 gene into various cancer cell lines suppressed cell growth. Infection with an adenovirus vector containing NEEP21 induced apoptotic cell death via caspase-3 activation in many cancer cell lines. The expression of NEEP21 mRNA was remarkably induced by γ-ray irradiation in the spleen of p53+/+ mice but not in that of p53-/- mice. These results suggest that NEEP21 may play a critical role in apoptosis as a mediator of p53.

Possible existence of lysosome-like organella within mitochondria and its role in mitochondrial quality control

The accumulation of unhealthy mitochondria results in mitochondrial dysfunction, which has been implicated in aging, cancer, and a variety of degenerative diseases. However, the mechanism by which mitochondrial quality is regulated remains unclear. Here, we show that Mieap, a novel p53-inducible protein, induces intramitochondrial lysosome-like organella that plays a critical role in mitochondrial quality control. Mieap expression is directly regulated by p53 and is frequently lost in human cancer as result of DNA methylation. Mieap dramatically induces the accumulation of lysosomal proteins within mitochondria and mitochondrial acidic condition without destroying the mitochondrial structure (designated MALM, for Mieap-induced accumulation of lysosome-like organelles within mitochondria) in response to mitochondrial damage. MALM was not related to canonical autophagy. MALM is involved in the degradation of oxidized mitochondrial proteins, leading to increased ATP synthesis and decreased reactive oxygen species generation. These results suggest that Mieap induces intramitochondrial lysosome-like organella that plays a critical role in mitochondrial quality control by eliminating oxidized mitochondrial proteins. Cancer cells might accumulate unhealthy mitochondria due to p53 mutations and/or Mieap methylation, representing a potential cause of the Warburg effect.

Observation of quasi-two-dimensional nonlinear interactions in a drift-wave streamer

A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schrödinger equation based on the Hasegawa-Mima model.

A novel nonsecosteroidal VDR agonist (CH5036249) exhibits efficacy in a spontaneous benign prostatic hyperplasia beagle model

To date, there have been no reports showing the efficacy of nonsecosteroidal vitamin D receptor (VDR) agonists in a benign prostatic hyperplasia (BPH) animal model. To examine the efficacy of CH5036249, a novel nonsecosteroidal VDR agonist, we orally administered the compound at 0.03 microg/kg to a beagle model with spontaneous BPH. Prostate volume was checked by rectal ultrasonic probe periodically during 11 months of administration and the prostate tissues histologically examined. CH5036249 inhibited prostate growth in two out of three dogs compared with vehicle-treated dogs. In the prostate specimens, substantial atrophy of the epithelium was observed in all dogs administered CH5036249. At the dose given, serum calcium levels slightly increased in the CH5036249-treated dogs but stayed within a normal range. We next examined the cell growth inhibition of CH5036249 using human prostate stromal cells and found the cell growth inhibitory activity of CH5036249 to be comparable to that of 1alpha,25(OH)2D3. The bioavailability from oral administration in rats was 95.1% with a t1/2 of 17.6 h. Both micro-AMES and micronucleus tests were negative. Although the results are still preliminary, we consider the novel nonsecosteroidal VDR agonist CH5036249 to be a possible new drug candidate for the treatment of BPH in humans.