A report from the 2013 international symposium: the evaluation of the effects of low-dose radiation exposure in the life span study of atomic bomb survivors and other similar studies

The RERF International Low-Dose Symposium was held on 5-6 December 2013 at the RERF campus in Hiroshima, Japan, to discuss the issues facing the Life Span Study (LSS) and other low-dose studies. Topics included the current status of low-dose risk detection, strategies for low-dose epidemiological and statistical research, methods to improve communication between epidemiologists and biologists, and the current status of radiological studies and tools. Key points made by the participants included the necessity of pooling materials over multiple studies to gain greater insight where data from single studies are insufficient; generating models that reflect epidemiological, statistical, and biological principles simultaneously; understanding confounders and effect modifiers in the current data; and taking into consideration less studied factors such as the impact of dose rate. It is the hope of all participants that this symposium be used as a trigger for further studies, especially those using pooled data, in order to reach a greater understanding of the health effects of low-dose radiation.

Ion-induced gamma-ray detection of fast ions escaping from fusion plasmas

A 12 × 12 pixel detector has been developed and used in a laboratory experiment for lost fast-ion diagnostics. With gamma rays in the MeV range originating from nuclear reactions (9)Be(α, nγ)(12)C, (9)Be(d, nγ)(12)C, and (12)C(d, pγ)(13)C, a high purity germanium (HPGe) detector measured a fine-energy-resolved spectrum of gamma rays. The HPGe detector enables the survey of background-gamma rays and Doppler-shifted photo peak shapes. In the experiments, the pixel detector produces a gamma-ray image reconstructed from the energy spectrum obtained from total photon counts of irradiation passing through the detector's lead collimator. From gamma-ray image, diagnostics are able to produce an analysis of the fast ion loss onto the first wall in principle.

Synthesis of cell-permeable stapled BH3 peptide-based Mcl-1 inhibitors containing simple aryl and vinylaryl cross-linkers

We report the synthesis of a series of distance-matching aryl and vinylaryl cross-linkers for constructing stapled peptides containing cysteines at i,i+7 positions. Langevin dynamics simulation studies helped to classify these cross-linkers into two categories: the rigid cross-linkers with narrower S-S distance distribution and the flexible cross-linkers with wider S-S distance distribution. The stapled Noxa BH3 peptides with the flexible distance-matching cross-linkers gave the highest degree of helicity as well as the most potent inhibitory activity against Mcl-1. However, the stapled peptides with the highest hydrophobicity showed the most efficient cellular uptake. Together, this work illustrates the divergent nature of binding affinity and cellular uptake, and the vital importance of choosing appropriate cross-linkers in constructing stapled peptides with the drug-like properties.

Abstract 1807: Pre-clinical evaluation of Mcl-1 inhibition through maritoclax in acute myeloid leukemia

There is an urgent and unmet medical need for development of new therapeutics for acute myeloid leukemia (AML). The anti-apoptotic Bcl-2 family protein Mcl-1 plays a critical role in AML cell survival and chemoresistance. Mcl-1 is upregulated in relapsed AML and leukemic stem cells. Inhibition of Mcl-1 expression in AML cells by kinase inhibitors or gene targeting induces apoptosis and suppresses leukemogenesis. However, the impact of targeting Mcl-1 in AML therapy with selective pharmacological inhibitors remains to be assessed. Recently, we discovered a novel Mcl-1 inhibitor, maritoclax (marinopyrrole A), which antagonizes Mcl-1 by targeting Mcl-1 for proteasomal degradation. This unique mechanism of action is in contrast to BH3 mimetics that exert their inhibitory function through disruption of the interactions between pro- and anti-apoptotic Bcl-2 family proteins. In a panel of AML cell lines, the potency of maritoclax positively correlated with Mcl-1 expression and inversely correlated with Bcl-2 and Bcl-xL expression. Maritoclax was efficacious as a single agent and markedly synergized with ABT-737 to induce apoptosis in Mcl-1 overexpressing ABT-737 and multidrug resistant AML cell lines. Moreover, maritoclax was able to overcome stroma-mediated resistance to apoptosis in AML cells. Importantly, maritoclax induced Mcl-1 degradation and apoptotic cell death selectively in clinical AML specimens with high levels of Mcl-1. To evaluate the anti-tumor activity of maritoclax in vivo, we established U937 tumor xenografts in nude mice. As a single agent, maritoclax significantly inhibited the growth of established xenografts at a dose of 20 mg/kg/d intraperitoneally. At this dosing level, no significant difference in body weight change and complete blood count was observed between maritoclax and vehicle treatment groups. Collectively, our studies demonstrated that maritoclax represents a novel class of Mcl-1 inhibitors and that the selective pharmacological inhibition of Mcl-1 may be a viable approach for the treatment of AML.

Citation Format: Qiang Liu, Kenichiro Doi, Krishne Gowda, Brian M. Barth, David Claxton, Shantu Amin, Thomas P. Loughran, Hong-Gang Wang. Pre-clinical evaluation of Mcl-1 inhibition through maritoclax in acute myeloid leukemia. [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 1807. doi:10.1158/1538-7445.AM2014-1807

Abstract 1805: Characterization of pyoluteorin derivatives as Mcl-1 antagonists

The evasion of apoptosis is considered to be a hallmark of cancers and a cause of resistance to anti-cancer therapies. Consistently, aberrant overexpression of anti-apoptotic Bcl-2 family proteins (e.g., Bcl-2, Bcl-xL, Mcl-1) is associated with tumorigenesis and increased resistance to chemotherapy in multiple malignancies. To date, several small-molecule Bcl-2 inhibitors that bind the BH3-binding pocket of the protein have entered clinical trials. These BH3 mimetics are known to induce apoptosis by disrupting the interactions between pro- and anti-apoptotic Bcl-2 family proteins. The most well characterized selective agents are the Bcl-2 inhibitor ABT-737 and its orally active analog ABT-263 which inhibit Bcl-2 and Bcl-XL but not Mcl-1. Consequently, cancers with elevated Mcl-1 do not respond to these drugs. Moreover, Mcl-1 is frequently upregulated in cancer cells and compensates for the inhibition of Bcl-2 function by ABT-737, thereby mediating resistance to the drug. Thus, there is an urgent need to develop Mcl-1-specific inhibitors for the treatment of Mcl-1-dependent human cancers. We have recently identified and characterized the natural product marinopyrrole A (maritoclax) as a novel Mcl-1 inhibitor, which induces apoptosis by targeting Mcl-1 for proteasomal degradation without significant effects on mRNA levels. To determine the pharmacophore of maritoclax, we systematically altered or removed portions of the molecule to identify regions essential for inhibition of Mcl-1 and induction of apoptosis. To date, we synthesized over 40 derivatives of maritoclax and evaluated their inhibitory actions toward Mcl-1 and cytotoxicity in cell lines of human hematological malignancies. As a result, we have identified several pharmacophore sites in maritoclax that are required for biological activity and two pyoluteorin derivatives, KS04 and KS18, which bind to a similar site(s) in Mcl-1 as maritoclax, as determined by NMR titration experiments. Like maritoclax, KS04 or KS18 markedly reduced the half-life of Mcl-1 protein, induced apoptosis selectively in Mcl-1-dependent but not Bcl-2-dependent K562 cells, and acted synergistically with ABT-737 to enhance apoptosis in ABT-737 resistant HL60 cells. Moreover, the combination treatment of KS18 (10 mg/kg/d) and ABT-737 (20 mg/kg/d) significantly suppressed the growth of ABT-737-resistant HL60 xenografts in nude mice. Thus, further studies are warranted to develop pyoluteorin derivatives as a novel class of Mcl-1 inhibitors.

Citation Format: Kenichiro Doi, Krishne Gowda, Qiang Liu, Shen-Shu Sung, Jyh Ming Lin, Shantu Amin, Thomas P. Loughran, Hong-Gang Wang. Characterization of pyoluteorin derivatives as Mcl-1 antagonists. [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 1805. doi:10.1158/1538-7445.AM2014-1805

Contralateral lower trapezius transfer for restoration of shoulder external rotation in traumatic brachial plexus palsy: a preliminary report and literature review

The importance of external rotation of the shoulder is well accepted. Patients with inadequate recovery of shoulder function after nerve transfers for a brachial plexus injury have difficulty in using their reconstructed limb. The options for secondary procedures to improve shoulder function are often limited, especially if the spinal accessory nerve has been used earlier for nerve transfer or as a donor nerve for a free functioning muscle transfer. We have used the contralateral lower trapezius transfer to the infraspinatus in three cases, to restore shoulder external rotation. All patients had significant improvement in shoulder external rotation (mean 97°; range 80°-110°) and improved disability of the arm, shoulder and hand scores. The rotation occurred mainly at the glenohumeral joint, and was independent of the donor side. All patients were greatly satisfied with the outcome. Contralateral lower trapezius transfer appears to help in overall improvement of shoulder function by stabilizing the scapula. The results have remained stable after mean follow-up of 58 months (range 12-86). No donor site deficit was seen in any patient.

Modified osteotomy (Kanaya's procedure) for congenital proximal radioulnar synostosis with posterior dislocation of radial head

Outcomes of Kanaya's procedure for congenital proximal radioulnar synostosis varied depending on the type of radial head dislocation. In our series of 14 patients with 17 forearms who underwent Kanaya's original procedure, the postoperative total rotation arc of the forearm was unsatisfactory in cases with posterior radial head dislocation. We examined the outcomes with respect to the type of radial head dislocation and radial shaft curvature. Radial shafts with a posterior radial head dislocation had only one curve and the radii of the curve were statistically smaller than those in anterior dislocated or enlocated heads, which had two curves. As a result, we modified the osteotomy site for proximal radioulnar synostosis with posterior radial head dislocation and achieved improved forearm rotation and physiological rotation of the radial head in our latest two cases.

Maritoclax induces apoptosis in acute myeloid leukemia cells with elevated Mcl-1 expression

Acute myeloid leukemia (AML) is one of the deadliest leukemias for which there is an urgent and unmet need for the development of novel treatment strategies. Multiple drug resistance mechanisms mediate poor drug response and relapse in patients, and a selective Mcl-1 inhibitor has been speculated to be a promising agent in the treatment of AML. Here, we describe that maritoclax, a small molecule Mcl-1 inhibitor, induces Mcl-1 proteasomal degradation without transcriptional downregulation. Maritoclax killed AML cell lines and primary cells with elevated Mcl-1 levels through selective Mcl-1 downregulation, and synergized with ABT-737 to overcome Mcl-1-mediated ABT-737 resistance. Maritoclax was more effective than daunorubicin at inducing leukemic cell death when co-cultured with HS-5 bone marrow stroma cells, while being less toxic than daunorubicin against HS-5 stroma cells, primary mouse bone marrow cells, and hematopoietic progenitor cells. Moreover, maritoclax administration at 20 mg/kg/d intraperitoneally caused significant U937 tumor shrinkage, as well as 36% tumors remission rate in athymic nude mice, without apparent toxicity to healthy tissue or circulating blood cells. In summary, our studies suggest that maritoclax belongs to a novel class of Mcl-1 inhibitors that has the potential to be developed for the treatment of AML.

Targeted delivery of ubiquitin-conjugated BH3 peptide-based Mcl-1 inhibitors into cancer cells

BH3 peptides are key mediators of apoptosis and have served as the lead structures for the development of anticancer therapeutics. Previously, we reported the application of a simple cysteine-based side chain cross-linking chemistry to NoxaBH3 peptides that led to the generation of the cross-linked NoxaBH3 peptides with increased cell permeability and higher inhibitory activity against Mcl-1 ( Muppidi, A., Doi, K., Edwardraja, S., Drake, E. J., Gulick, A. M., Wang, H.-G., Lin, Q. ( 2012 ) J. Am. Chem. Soc. 134 , 14734 ). To deliver cross-linked NoxaBH3 peptides selectively into cancer cells for enhanced efficacy and reduced systemic toxicity, here we report the conjugation of the NoxaBH3 peptides with the extracellular ubiquitin, a recently identified endogenous ligand for CXCR4, a chemokine receptor overexpressed in cancer cells. The resulting ubiquitin-NoxaBH3 peptide conjugates showed increased inhibitory activity against Mcl-1 and selective killing of the CXCR4-expressing cancer cells. The successful delivery of the NoxaBH3 peptides by ubiquitin into cancer cells suggests that the ubiquitin/CXCR4 axis may serve as a general route for the targeted delivery of anticancer agents.

Proteasomal degradation of Mcl-1 by maritoclax induces apoptosis and enhances the efficacy of ABT-737 in melanoma cells

Background and purpose

Metastatic melanoma remains one of the most invasive and highly drug resistant cancers. The over expression of anti-apoptotic protein Mcl-1 has been associated with inferior survival, poor prognosis and chemoresistance of malignant melanoma. A BH3 mimetic, ABT-737, has demonstrated efficacy in several forms of cancers. However, the efficacy of ABT-737 depends on Mcl-1. Because the over expression of Mcl-1 is frequently observed in melanoma, specifically targeting of Mcl-1 may overcome the resistance of ABT-737. In this study, we investigated the effects of Maritoclax, a novel Mcl-1-selective inhibitor, alone and in combination with ABT-737, on the survival of human melanoma cells.

Experimental approach

For cell viability assessment we performed MTT assay. Apoptosis was determined using western blot and flow cytometric analysis.

Key results

The treatment of Maritoclax reduced the cell viability of melanoma cells with an IC₅₀ of between 2.2–5.0 µM. Further, treatment of melanoma cells with Maritoclax showed significant decrease in Mcl-1 expression. We found that Maritoclax was able to induce apoptosis in melanoma cells in a caspase-dependent manner. Moreover, Maritoclax induced Mcl-1 degradation via the proteasome system, which was associated with its pro-apoptotic activity. We also found that Maritoclax treatment increased mitochondrial translocation of Bim and Bmf. Importantly, Maritoclax markedly enhanced the efficacy of ABT-737 against melanoma cells in both two- and three-dimensional spheroids.

Conclusions and implications

Taken together, these results suggest that targeting of Mcl-1 by Maritoclax may represent a new therapeutic strategy for melanoma treatment that warrants further investigation as a single therapy or in combination with other agents such as Bcl-2 inhibitors.

Rational design of proteolytically stable, cell-permeable peptide-based selective Mcl-1 inhibitors

Direct chemical modifications provide a simple and effective means to "translate" bioactive helical peptides into potential therapeutics targeting intracellular protein-protein interactions. We previously showed that distance-matching bisaryl cross-linkers can reinforce peptide helices containing two cysteines at the i and i+7 positions and confer cell permeability to the cross-linked peptides. Here we report the first crystal structure of a biphenyl-cross-linked Noxa peptide in complex with its target Mcl-1 at 2.0 Å resolution. Guided by this structure, we remodeled the surface of this cross-linked peptide through side-chain substitution and N-methylation and obtained a pair of cross-linked peptides with substantially increased helicity, cell permeability, proteolytic stability, and cell-killing activity in Mcl-1-overexpressing U937 cells.

Synthesis and evaluation of substituted hexahydronaphthalenes as novel inhibitors of the Mcl-1/BimBH3 interaction

Mcl-1, an anti-apoptotic member of the Bcl-2 protein family, is overexpressed in a broad range of human cancers and plays a critical role in conferring resistance to chemotherapy. In the course of screening a natural product-like library of sesquiterpenoid analogs, we identified substituted hexahydronaphthalenes that showed activity against the Mcl-1/BimBH3 interaction in vitro. Here, we describe the synthesis of a small library of analogs and their biological evaluation. The most potent inhibitor in the series (19) exhibits an IC(50) of 8.3 μM by ELISA and disrupts the interaction between endogenously expressed Mcl-1 and Bim in cultured MDA-MB-468 breast cancer cells.

[Cardiac surgery for patients with ventricular dysfunction]

Coronary artery disease and aortic stenosis/regurgitation may cause irreversible myocardial damage, resulting in significant heart failure. Although the ultimate treatment of the end-stage heart failure is heart transplantation or ventricular assist devices, in most cases these patients still have some amount of functional and survival benefit by simple surgical treatment such as coronary artery bypass grafting (CABG) and valve replacement. However it is associated with significant perioperative mortality and morbidity.

Formation of NaCl-type monodeuteride LaD by the disproportionation reaction of LaD2

Previous x-ray diffraction measurements revealed the pressure-induced decomposition of an fcc LaH2.3 into H-rich and H-poor fcc phases around 11 GPa. The present neutron diffraction measurements on LaD2 confirm the formation of NaCl-type LaD as a counterpart of the D-rich LaD2+δ by disproportionation. First-principles enthalpy and lattice dynamic calculations demonstrate that the NaCl-type LaH is stabilized at high pressures and can be recovered at ambient conditions. Finding the NaCl-type LaH will pave the way for investigations on the site-dependent nature of hydrogen-metal interactions.

Discovery of marinopyrrole A (maritoclax) as a selective Mcl-1 antagonist that overcomes ABT-737 resistance by binding to and targeting Mcl-1 for proteasomal degradation

The anti-apoptotic Bcl-2 family of proteins, including Bcl-2, Bcl-X(L) and Mcl-1, are well-validated drug targets for cancer treatment. Several small molecules have been designed to interfere with Bcl-2 and its fellow pro-survival family members. While ABT-737 and its orally active analog ABT-263 are the most potent and specific inhibitors to date that bind Bcl-2 and Bcl-X(L) with high affinity but have a much lower affinity for Mcl-1, they are not very effective as single agents in certain cancer types because of elevated levels of Mcl-1. Accordingly, compounds that specifically target Mcl-1 may overcome this resistance. In this study, we identified and characterized the natural product marinopyrrole A as a novel Mcl-1-specific inhibitor and named it maritoclax. We found that maritoclax binds to Mcl-1, but not Bcl-X(L), and is able to disrupt the interaction between Bim and Mcl-1. Moreover, maritoclax induces Mcl-1 degradation via the proteasome system, which is associated with the pro-apoptotic activity of maritoclax. Importantly, maritoclax selectively kills Mcl-1-dependent, but not Bcl-2- or Bcl-X(L)-dependent, leukemia cells and markedly enhances the efficacy of ABT-737 against hematologic malignancies, including K562, Raji, and multidrug-resistant HL60/VCR, by ∼60- to 2000-fold at 1-2 μM. Taken together, these results suggest that maritoclax represents a new class of Mcl-1 inhibitors, which antagonizes Mcl-1 and overcomes ABT-737 resistance by targeting Mcl-1 for degradation.

Screening of protein-protein interaction modulators via sulfo-click kinetic target-guided synthesis

Kinetic target-guided synthesis (TGS) and in situ click chemistry are among unconventional discovery strategies having the potential to streamline the development of protein-protein interaction modulators (PPIMs). In kinetic TGS and in situ click chemistry, the target is directly involved in the assembly of its own potent, bidentate ligand from a pool of reactive fragments. Herein, we report the use and validation of kinetic TGS based on the sulfo-click reaction between thio acids and sulfonyl azides as a screening and synthesis platform for the identification of high-quality PPIMs. Starting from a randomly designed library consisting of 9 thio acids and 9 sulfonyl azides leading to 81 potential acylsulfonamides, the target protein, Bcl-X(L), selectively assembled four PPIMs, acylsulfonamides SZ4TA2, SZ7TA2, SZ9TA1, and SZ9TA5, which have been shown to modulate Bcl-X(L)/BH3 interactions. To further investigate the Bcl-X(L) templation effect, control experiments were carried out using two mutants of Bcl-X(L). In one mutant, phenylalanine Phe131 and aspartic acid Asp133, which are critical for the BH3 domain binding, were substituted by alanines, while arginine Arg139, a residue identified to play a crucial role in the binding of ABT-737, a BH3 mimetic, was replaced by an alanine in the other mutant. Incubation of these mutants with the reactive fragments and subsequent LC/MS-SIM analysis confirmed that these building block combinations yield the corresponding acylsulfonamides at the BH3 binding site, the actual "hot spot" of Bcl-X(L). These results validate kinetic TGS using the sulfo-click reaction as a valuable tool for the straightforward identification of high-quality PPIMs.

Abstract 1354: New chemical tools for disrupting the Mcl-1/BH3 protein-protein interaction

Anti-apoptotic members of the Bcl-2 protein family, such as Bcl-2, Bcl-xL and Mcl-1, are among the most effective inhibitors of apoptosis and are frequently upregulated in various types of human cancer. A number of pro-apoptotic proteins share only the BH3 domain with other members of the Bcl-2 family, so called BH3-only proteins, and appear to function essentially as transdominant inhibitors by binding to anti-apoptotic Bcl-2 family proteins and neutralizing their cell-survival activity. The development of small molecules to mimic the BH3 proteins has been an intense area of research. However, to date available Bcl-2 family proteins inhibitors are either pan-inhibitors such as (−)-gossypol (which simultaneously inhibits Bcl-xl/BH3, Bcl-2/BH3 and Mcl-1/BH3 interactions) or are selective for the Bcl-xl/BH3 and Bcl-2/BH3 interactions. Hence a selective Mcl-1/BH3 inhibitor would greatly aid investigating the role of Mcl-1 in cancer and in drug resistance. Our current study is centered on the identification and the synthesis of small molecule selective inhibitors of the Mcl-1/BH3 interaction. To this aim we interrogated the hit-list from inhibitors of the MLSCN screen of the Mcl-1-NOXA interaction [(Emory, AID 1417) TR-FRET screen for Mcl-1-NOXA inhibitors]. Selected compounds were purchased and assessed for activity in a fluorescence polarization and ELISA assay, to reveal the hit HLM050001 (FP IC50 0.8 ± 0.1 µM; ELISA IC50 19.3 ± 2.5 µM). HLM050001binding to Mcl-1 is currently being assessed via co-crystallization and other biophysical techniques. We will report the synthesis and biological evaluation of focused libraries based on the initial hit and designed by modeling and docking to Mcl-1. Structure activity relationship studies around the hit will be disclosed as well as the outcomes of further rounds of chemical design and biological assessment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1354. doi:10.1158/1538-7445.AM2011-1354