Identification of antimycin A as a c-Myc degradation accelerator via high-throughput screening

c-Myc is a critical regulator of cell proliferation and growth. Elevated levels of c-Myc cause transcriptional amplification, leading to various types of cancers. Small molecules that specifically inhibit c-Myc-dependent regulation are potentially invaluable for anticancer therapy. Because c-Myc does not have enzymatic activity or targetable pockets, researchers have attempted to obtain small molecules that inhibit c-Myc cofactors, activate c-Myc repressors, or target epigenetic modifications to regulate the chromatin of c-Myc-addicted cancer without any clinical success. In this study, we screened for c-Myc inhibitors using a cell-dependent assay system in which the expression of c-Myc and its transcriptional activity can be inferred from monomeric Keima and enhanced GFP fluorescence, respectively. We identified one mitochondrial inhibitor, antimycin A, as a hit compound. The compound enhanced the c-Myc phosphorylation of threonine-58, consequently increasing the proteasome-mediated c-Myc degradation. The mechanistic analysis of antimycin A revealed that it enhanced the degradation of c-Myc protein through the activation of glycogen synthetic kinase 3 by reactive oxygen species (ROS) from damaged mitochondria. Furthermore, we found that the inhibition of cell growth by antimycin A was caused by both ROS-dependent and ROS-independent pathways. Interestingly, ROS-dependent growth inhibition occurred only in the presence of c-Myc, which may reflect the representative features of cancer cells. Consistently, the antimycin A sensitivity of cells was correlated to the endogenous c-Myc levels in various cancer cells. Overall, our study provides an effective strategy for identifying c-Myc inhibitors and proposes a novel concept for utilizing ROS inducers for cancer therapy.

Allantopyrone A interferes with the degradation of hypoxia-inducible factor 1α protein by reducing proteasome activity in human fibrosarcoma HT-1080 cells

Allantopyrone A is an α-pyrone metabolite that was originally isolated from the endophytic fungus Allantophomopsis lycopodina KS-97. We previously demonstrated that allantopyrone A exhibits anti-cancer, anti-inflammatory, and neuroprotective activities. In the present study, we showed that allantopyrone A up-regulated the protein expression of hypoxia-inducible factor (HIF)-1α in human fibrosarcoma HT-1080 cells. It also up-regulated the mRNA expression of BNIP3 and ENO1, but not other HIF target genes or HIF1A. Allantopyrone A did not inhibit the prolyl hydroxylation of HIF-1α, but enhanced the ubiquitination of cellular proteins. Consistent with this result, chymotrypsin-like and trypsin-like proteasome activities were reduced, but not completely inactivated by allantopyrone A. Allantopyrone A decreased the amount of proteasome catalytic subunits. Therefore, the present results showed that allantopyrone A interfered with the degradation of HIF-1α protein by reducing proteasome activity in human fibrosarcoma HT-1080 cells.

Registration of Alfvén resonances in TCABR tokamak by the scanning reflectometer at sideband frequencies

A frequency scanning O-mode reflectometer was used for studies of plasma density oscillations during local Alfvén wave (LAW) excitation in the Tokamak Chauffage Alfvén Brésilien (TCABR) at the frequency f(A) = 5 MHz. It was found that the spectrum of the reflectometer output signal, which consists mainly of the "beat" frequency f(B), is modified by the LAW excitation, and two additional frequency peaks appear, which are symmetrical in relation to the LAW excitation frequency f = f(A) ± f(B). This result opens the possibility to improve the efficiency of studying the LAW induced density oscillations. The symmetry of these frequency peaks yields the possibility of finding the microwave frequency at which the reflectometer cutoff layer coincides with radial position of the LAW resonance zone in the TCABR tokamak.

Analysis of the core region of HCV genome isolated from patients with chronic hepatitis C during intervals of normal ALT concentration

We determined the core region nucleotide and amino acid sequences in specimens from two patients with chronic hepatitis C during intervals of normal and elevated alanine aminotransferase (ALT) concentrations. When the ALT concentrations remained normal, the serum HCR-RNA concentration exceeded that before therapy and most of the clones that could be sequenced had a deletion or an amber mutation. The clones isolated from a HLA B44-positive patient had a mutation at amino acid 91. These results suggest that expression of the wild-type HCV core region genome may be associated with liver cell damage.

Fulminant hepatitis caused by a hepatitis B virus core region variant strain

We studied the viral genome of a hepatitis B viral strain isolated from a patient with fulminant hepatitis. The patient was followed from prior to the rise in transaminases until she recovered. The precore and core regions of the viral strains were sequenced before and after the illness via the polymerase chain reaction and subcloning methods. Prior to her clinical illness, a strain with precore wild-type sequence and core mutations corresponding to amino acid residues 77 and 113 was noted in large quantities. With the onset of hepatitis, this core variant completely disappeared. Very low titers of precore and core wild or partial core deletion strains remained 1 month later. The core variants described may have contributed to the severe host immune reaction, fulminant hepatitis and immune-mediated viral clearance. Such variants appeared to have been eliminated, and wild and core-deleted virus that lacked the peculiar mutations remained.

Human cardiovascular and vestibular responses in long minutes and low +Gz loading by short arm centrifuge

1.4 G, 1.7 G, and 2.0 G of +Gz and 60 minutes centrifugation was adopted to 20 healthy male subjects using 1.8 m radius centrifuge equipped to Nihon University School of Medicine. G was applied from lower G, considering G training effect for the subjects. Effects on performance decline and side effects of such a short-arm centrifugation were especially observed in the experiments, because this size of centrifuge could be used in space station in future for a strong countermeasure of cardiovascular deconditioning, demineralization from bone, etc. G training effect was observed same as higher and rapid G acceleration in fighter pilot. Subjects suffered from many types of discomfort; such as sensation of heaviness of diaphragm, cold sweat, nausea, irritable feeling, arrhythmia, tachycardia, rapid decrease of blood pressure, which sometimes caused interruption of G load. As 2.0 G and 60 minutes centrifugation seemed very tough load to the subjects, there should be necessary some G suit or other countermeasure, if we apply a higher G and/or longer G duration. Performance decline due to the load commonly continued for 1 hour or so. Side effects were observed in relation to neuro-vestibular, cardio-vascular, and autonomic nervous system.

Desmoplastic malignant melanoma of the gingiva

A case of desmoplastic melanoma in a 58-year-old man is reported. This rare malignancy occurred in the maxillary alveolus, appearing as an epulis. Histologically, the tumor was flanked by melanocytic proliferation in the adjacent mucosae. At the time of local recurrence after partial maxillectomy, the tumor showed a polypoid growth, with an increase in cellularity and mitotic rate resembling spindle cell carcinoma. The value of immunostaining for diagnosis is stressed.

Synergistic antiproliferative effect of the combination of natural human tumor necrosis factor-alpha and natural murine interferon-alpha/beta against colon-26 adenocarcinoma hepatic metastases in a murine model

To prevent the development of hepatic metastases after surgery for colorectal cancer, it is important to inhibit the growth of any micrometastases which occur during the operation. We used a hepatic metastasis model in mice to investigate the effects of combination therapy with natural human tumor necrosis factor-alpha (nHuTNF-alpha) and natural murine interferon-alpha/beta (nMuIFN-alpha/beta). Decreased formation of hepatic metastases by murine colon-26 carcinoma was recognized following a single injection of nHuTNF-alpha, nMuIFN-alpha/beta, or both. These inhibitory effects were synergistic. NK activity was also measured, because notaral lerller cells not only have an anti-tumor effect but are also a representative of the host immune system. Both nHuTNF-alpha and nMuIFN-alpha/beta were able to activate NK cells, and the combination of the cytokines more significantly augmented NK activity. The in vivo elevation of NK activity induced by nHuTNF-alpha, nMuIFN-alpha/beta, or their combination may be one of the mechanisms of their antiproliferative effect on experimental hepatic metastases of murine colon-26 carcinoma.

Postoperative starch granuloma revealed as femoral herniation. A case report

A rare case of postoperative starch granuloma in a 55-year-old woman, revealed as femoral herniation, is reported. A small, finger-tip-sized tumor showing femoral herniation was noticed 3 weeks after cholecystectomy for cholelithiasis, and no content in the hernia sac was noticed. Histologically, the granuloma situated in the wall of the hernia sac was diagnosed as a starch granuloma consisting of starch granules, which were clearly revealed by polarized light microscopy. These granules were detected in the cytoplasm of macrophages including multinucleated types, some showing a positive immune reaction with antibodies to the alpha-subunit of S-100 protein, vimentin and lysozyme. Starch granules from surgical gloves showed identical features by polarized light microscopy, thus proving the histogenesis of this granuloma. This is the first reported case in the Japanese literature of starch granuloma manifested as femoral herniation.

[Favorable response of advanced hepatocellular carcinoma to proper hepatic arterial administration of cytokines and the significance of the administration]

The objectives in administering anti-cancer therapeutics to the feeding artery of the tumor are to allow the agent to come in direct contact with the tumor cells, to lower the concentration of the agent in body circulation, to lessen the severity of side effects, and to augment efficacy of the agent. A remarkable partial regression was observed in two patients with advanced hepatocellular carcinoma, both at the stage in which surgical excision was diagnosed impossible; one was given successive and daily bolus administration of OH-1, a anti-tumor agent consisting of natural human tumor necrosis factor-alpha (nHuTNF-alpha) and natural human interferon (nHulFN-alpha), and the other a successive and daily combined bolus administration of OH-1 and 5-FU. On investigating the role of the anti-cancer activity of OH-1 by analyzing the NK activity of rat liver large granular lymphocytes, we found that the NK activity was suppressed dose-dependently by nHuTNF-alpha, but not significantly. Thus, an increase in TNF dose in hepatic artery therapy seems undesirable from the standpoint of NK activity. The authors are presently carrying out investigations to elucidate the effector mechanism of the anticancer activity of OH-1.