The effects of short-term, progressive exercise training on disease activity in smouldering multiple myeloma and monoclonal gammopathy of undetermined significance: a single-arm pilot study

BACKGROUND

High levels of physical activity are associated with reduced risk of the blood cancer multiple myeloma (MM). MM is preceded by the asymptomatic stages of monoclonal gammopathy of undetermined significance (MGUS) and smouldering multiple myeloma (SMM) which are clinically managed by watchful waiting. A case study (N = 1) of a former elite athlete aged 44 years previously indicated that a multi-modal exercise programme reversed SMM disease activity. To build from this prior case study, the present pilot study firstly examined if short-term exercise training was feasible and safe for a group of MGUS and SMM patients, and secondly investigated the effects on MGUS/SMM disease activity.

METHODS

In this single-arm pilot study, N = 20 participants diagnosed with MGUS or SMM were allocated to receive a 16-week progressive exercise programme. Primary outcome measures were feasibility and safety. Secondary outcomes were pre- to post-exercise training changes to blood biomarkers of MGUS and SMM disease activity- monoclonal (M)-protein and free light chains (FLC)- plus cardiorespiratory and functional fitness, body composition, quality of life, blood immunophenotype, and blood biomarkers of inflammation.

RESULTS

Fifteen (3 MGUS and 12 SMM) participants completed the exercise programme. Adherence was 91 ± 11%. Compliance was 75 ± 25% overall, with a notable decline in compliance at intensities > 70% V̇O2PEAK. There were no serious adverse events. There were no changes to M-protein (0.0 ± 1.0 g/L, P =.903), involved FLC (+ 1.8 ± 16.8 mg/L, P =.839), or FLC difference (+ 0.2 ± 15.6 mg/L, P =.946) from pre- to post-exercise training. There were pre- to post-exercise training improvements to diastolic blood pressure (- 3 ± 5 mmHg, P =.033), sit-to-stand test performance (+ 5 ± 5 repetitions, P =.002), and energy/fatigue scores (+ 10 ± 15%, P =.026). Other secondary outcomes were unchanged.

CONCLUSIONS

A 16-week progressive exercise programme was feasible and safe, but did not reverse MGUS/SMM disease activity, contrasting a prior case study showing that five years of exercise training reversed SMM in a 44-year-old former athlete. Longer exercise interventions should be explored in a group of MGUS/SMM patients, with measurements of disease biomarkers, along with rates of disease progression (i.e., MGUS/SMM to MM).

REGISTRATION

https://www.isrctn.com/ISRCTN65527208 (14/05/2018).

A small-molecule inhibitor of the BRCA2-RAD51 interaction modulates RAD51 assembly and potentiates DNA damage-induced cell death

BRCA2 controls RAD51 recombinase during homologous DNA recombination (HDR) through eight evolutionarily conserved BRC repeats, which individually engage RAD51 via the motif Phe-x-x-Ala. Using structure-guided molecular design, templated on a monomeric thermostable chimera between human RAD51 and archaeal RadA, we identify CAM833, a 529 Da orthosteric inhibitor of RAD51:BRC with a K_d of 366 nM. The quinoline of CAM833 occupies a hotspot, the Phe-binding pocket on RAD51 and the methyl of the substituted α-methylbenzyl group occupies the Ala-binding pocket. In cells, CAM833 diminishes formation of damage-induced RAD51 nuclear foci; inhibits RAD51 molecular clustering, suppressing extended RAD51 filament assembly; potentiates cytotoxicity by ionizing radiation, augmenting 4N cell-cycle arrest and apoptotic cell death and works with poly-ADP ribose polymerase (PARP)1 inhibitors to suppress growth in BRCA2-wildtype cells. Thus, chemical inhibition of the protein-protein interaction between BRCA2 and RAD51 disrupts HDR and potentiates DNA damage-induced cell death, with implications for cancer therapy.

Development of a Novel Cell-Permeable Protein-Protein Interaction Inhibitor for the Polo-box Domain of Polo-like Kinase 1

Polo-like kinase 1 (PLK1) is a key regulator of mitosis and a recognized drug target for cancer therapy. Inhibiting the polo-box domain of PLK1 offers potential advantages of increased selectivity and subsequently reduced toxicity compared with targeting the kinase domain. However, many if not all existing polo-box domain inhibitors have been shown to be unsuitable for further development. In this paper, we describe a novel compound series, which inhibits the protein-protein interactions of PLK1 via the polo-box domain. We combine high throughput screening with molecular modeling and computer-aided design, synthetic chemistry, and cell biology to address some of the common problems with protein-protein interaction inhibitors, such as solubility and potency. We use molecular modeling to improve the solubility of a hit series with initially poor physicochemical properties, enabling biophysical and biochemical characterization. We isolate and characterize enantiomers to improve potency and demonstrate on-target activity in both cell-free and cell-based assays, entirely consistent with the proposed binding model. The resulting compound series represents a promising starting point for further progression along the drug discovery pipeline and a new tool compound to study kinase-independent PLK functions.

A cryptic hydrophobic pocket in the polo-box domain of the polo-like kinase PLK1 regulates substrate recognition and mitotic chromosome segregation

The human polo-like kinase PLK1 coordinates mitotic chromosome segregation by phosphorylating multiple chromatin- and kinetochore-binding proteins. How PLK1 activity is directed to specific substrates via phosphopeptide recognition by its carboxyl-terminal polo-box domain (PBD) is poorly understood. Here, we combine molecular, structural and chemical biology to identify a determinant for PLK1 substrate recognition that is essential for proper chromosome segregation. We show that mutations ablating an evolutionarily conserved, Tyr-lined pocket in human PLK1 PBD trigger cellular anomalies in mitotic progression and timing. Tyr pocket mutations selectively impair PLK1 binding to the kinetochore phosphoprotein substrate PBIP1, but not to the centrosomal substrate NEDD1. Through a structure-guided approach, we develop a small-molecule inhibitor, Polotyrin, which occupies the Tyr pocket. Polotyrin recapitulates the mitotic defects caused by mutations in the Tyr pocket, further evidencing its essential function, and exemplifying a new approach for selective PLK1 inhibition. Thus, our findings support a model wherein substrate discrimination via the Tyr pocket in the human PLK1 PBD regulates mitotic chromosome segregation to preserve genome integrity.

Modulating Protein-Protein Interactions of the Mitotic Polo-like Kinases to Target Mutant KRAS

Mutations activating KRAS underlie many forms of cancer, but are refractory to therapeutic targeting. Here, we develop Poloppin, an inhibitor of protein-protein interactions via the Polo-box domain (PBD) of the mitotic Polo-like kinases (PLKs), in monotherapeutic and combination strategies to target mutant KRAS. Poloppin engages its targets in biochemical and cellular assays, triggering mitotic arrest with defective chromosome congression. Poloppin kills cells expressing mutant KRAS, selectively enhancing death in mitosis. PLK1 or PLK4 depletion recapitulates these cellular effects, as does PBD overexpression, corroborating Poloppin's mechanism of action. An optimized analog with favorable pharmacokinetics, Poloppin-II, is effective against KRAS-expressing cancer xenografts. Poloppin resistance develops less readily than to an ATP-competitive PLK1 inhibitor; moreover, cross-sensitivity persists. Poloppin sensitizes mutant KRAS-expressing cells to clinical inhibitors of c-MET, opening opportunities for combination therapy. Our findings exemplify the utility of small molecules modulating the protein-protein interactions of PLKs to therapeutically target mutant KRAS-expressing cancers.

Allosteric modulation of AURKA kinase activity by a small-molecule inhibitor of its protein-protein interaction with TPX2

The essential mitotic kinase Aurora A (AURKA) is controlled during cell cycle progression via two distinct mechanisms. Following activation loop autophosphorylation early in mitosis when it localizes to centrosomes, AURKA is allosterically activated on the mitotic spindle via binding to the microtubule-associated protein, TPX2. Here, we report the discovery of AurkinA, a novel chemical inhibitor of the AURKA-TPX2 interaction, which acts via an unexpected structural mechanism to inhibit AURKA activity and mitotic localization. In crystal structures, AurkinA binds to a hydrophobic pocket (the 'Y pocket') that normally accommodates a conserved Tyr-Ser-Tyr motif from TPX2, blocking the AURKA-TPX2 interaction. AurkinA binding to the Y- pocket induces structural changes in AURKA that inhibit catalytic activity in vitro and in cells, without affecting ATP binding to the active site, defining a novel mechanism of allosteric inhibition. Consistent with this mechanism, cells exposed to AurkinA mislocalise AURKA from mitotic spindle microtubules. Thus, our findings provide fresh insight into the catalytic mechanism of AURKA, and identify a key structural feature as the target for a new class of dual-mode AURKA inhibitors, with implications for the chemical biology and selective therapeutic targeting of structurally related kinases.

Dog Ecology and Barriers to Canine Rabies Control in the Republic of Haiti, 2014-2015

An estimated 59 000 persons die annually of infection with the rabies virus worldwide, and dog bites are responsible for 95% of these deaths. Haiti has the highest rate of animal and human rabies in the Western Hemisphere. This study describes the status of animal welfare, animal vaccination, human bite treatment, and canine morbidity and mortality in Haiti in order to identify barriers to rabies prevention and control. An epidemiologic survey was used for data collection among dog owners during government-sponsored vaccination clinics at fourteen randomly selected sites from July 2014 to April 2015. A total of 2005 surveys were collected and data were analysed using parametric methods. Over 50% of owned dogs were allowed to roam freely, a factor associated with rabies transmission. More than 80% of dog owners reported experiencing barriers to accessing rabies vaccination for their dogs. Nearly one-third of the dog population evaluated in this study died in the year preceding the survey (32%) and 18% of these deaths were clinically consistent with rabies. Dog bites were commonly reported, with more than 3% of the study population bitten within the year preceding the survey. The incidence of canine rabies in Haiti is high and is exacerbated by low access to veterinary care, free-roaming dog populations and substandard animal welfare practices. Programmes to better understand the dog ecology and development of methods to improve access to vaccines are needed. Rabies deaths are at historical lows in the Western Hemisphere, but Haiti and the remaining canine rabies endemic countries still present a significant challenge to the goal of rabies elimination in the region.

High content screening of diverse compound libraries identifies potent modulators of tubulin dynamics

Tubulin modulating agents such as the taxanes are among the most effective antimitotic cancer drugs, although resistance and toxicity present significant problems in their clinical use. However, most tubulin modulators are derived from complex natural products, which can make modification of their structure to address these problems difficult. Here, we report the discovery of new antimitotic compounds with simple structures that can be rapidly synthesized, through the phenotypic screening of a diverse compound library for the induction of mitotic arrest. We first identified a compound, which induced mitotic arrest in human cells at submicromolar concentrations. Its simple structure enabled rapid exploration of activity, defining a biphenylacetamide moiety required for activity, A family of analogues was synthesized, yielding optimized compounds that caused mitotic arrest and cell death in the low nanomolar range, comparable to clinically used antimitotic agents. These compounds can be synthesized in 1-3 steps and good yields. We show that one such compound targets tubulin, partially inhibiting colchicine but not vinblastine binding, suggesting that it acts allosterically to the known colchicine-binding site. Thus, our results exemplify the use of phenotypic screening to identify novel antimitotic compounds from diverse chemical libraries and characterize a family of biphenylacetamides (biphenabulins) that show promise for further development.

A novel cell-based, high-content assay for phosphorylation of Lats2 by Aurora A

Aurora A kinase is a key regulator of mitosis, which is upregulated in several human cancers, making it a potential target for anticancer therapeutics. Consequently, robust medium- to high-throughput cell-based assays to measure Aurora A kinase activity are critical for the development of small-molecule inhibitors. Here the authors compare measurement of the phosphorylation of two Aurora A substrates previously used in high-content screening Aurora A assays, Aurora A itself and TACC3, with a novel substrate Lats2. Using antibodies directed against phosphorylated forms of Aurora A (pThr288), P-TACC3 (pSer558), and P-Lats2 (pSer83), the authors investigate their suitability in parallel for development of a cell-based assay using several reference Aurora inhibitors: MLN8054, VX680, and AZD1152-HQPA. They validate a combined assay of target-specific phosphorylation of Lats2 at the centrosome and an increase in mitotic index as a measure of Aurora A activity. The assay is both sensitive and robust and has acceptable assay performance for high-throughput screening or potency estimation from concentration-response assays. It has the advantage that it can be carried out using a commercially available monoclonal antibody against phospho-Lats2 and the widely available Cellomics ArrayScan HCS reader and thus represents a significant addition to the tools available for the identification of Aurora A specific inhibitors.

Development and application of an ethically and epidemiologically advantageous assay for the multi-locus microsatellite analysis of Schistosoma mansoni

Non-availability of adult worms from living hosts remains a key problem in population genetic studies of schistosomes. Indirect sampling involving passage through laboratory animals presents significant ethical and practical drawbacks, and may result in sampling biases such as bottlenecking processes and/or host-induced selection pressures. The novel techniques reported here for sampling, storage and multi-locus microsatellite analysis of larval Schistosoma mansoni, allowing genotyping of up to 7 microsatellite loci from a single larva, circumvent these problems. The utility of these assays and the potential problems of laboratory passage, were evaluated using 7 S. mansoni population isolates collected from school-children in the Hoima district of Uganda, by comparing the associated field-collected miracidia with adult worms and miracidia obtained from a single generation in laboratory mice. Analyses of laboratory-passaged material erroneously indicated the presence of geographical structuring in the population, emphasizing the dangers of indirect sampling for population genetic studies. Bottlenecking and/or other sampling effects were demonstrated by reduced variability of adult worms compared to their parent field-collected larval samples. Patterns of heterozygote deficiency were apparent in the field-collected samples, which were not evident in laboratory-derived samples, potentially indicative of heterozygote advantage in establishment within laboratory hosts. Genetic distance between life-cycle stages in the majority of isolates revealed that adult worms and laboratory-passaged miracidia clustered together whilst segregating from field miracidia, thereby further highlighting the utility of this assay.

European collaboration in research into rare diseases: experience of the European Neuromuscular Centre

An understanding of the possible causes, prevention and treatment of rare, so-called 'orphan disease' requires collaboration in research between different centres with the sharing of information. In the case of neuromuscular disorders (such as muscular dystrophies or hereditary neuropathies) this has been achieved through European collaborative research encouraged and facilitated by the European Neuromuscular Centre (ENMC). The successful example of ENMC provides a model for the investigation of other rare 'orphan' disorders or even rare problems occurring in common disorders.

Analysis of deletions in DNA from patients with Becker and Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder for which the biochemical defect is as yet unknown. Recently, two cloned segments of human X-chromosome DNA have been described which detect structural alterations within or near the genetic locus responsible for the disorder. Both of these cloned segments were described as tightly linked to the locus and were capable of detecting deletions in the DNA of boys affected with DMD. In an attempt to determine more precisely the occurrence of these deletions within a large population of DMD patients and the accuracy of one of the segments, DXS164 (pERT87), in determining the inheritance of the DMD X chromosome, the subclones 1, 8 and 15 were made available to many investigators throughout the world. Here we describe the combined results of more than 20 research laboratories with respect to the occurrence of deletions at the DXS164 locus in DNA samples isolated from patients with DMD and Becker muscular dystrophy (BMD). The results indicate that the DXS164 locus apparently recombines with DMD 5% of the time, but is probably located between independent sites of mutation which yield DMD. The breakpoints of some deletions are delineated within the DXS164 locus, and it is evident that the deletions at the DMD locus are frequent and extremely large.

Proteolytic denaturation and methods of improving the stability of glucose isomerase preparations

Evidence is provided in support of proteolytic denaturation of free and immobilized preparations of glucose isomerase from a Bacillus species. A number of methods to improve the stability with respect to proteolysis have been tested and their advantages as well as shortcomings are discussed. These methods include hollow-fiber treatment, gel permeation, thermal treatment, and addition of protease inhibitors. The half-life of the free and the cellulose acetate fiber-entrapped preparations of glucose isomerase can be significantly improved. For example, the hollow-fiber treatment can improve the half-life by an order of magnitude.

Characterization of sand as a support for immobilized enzymes

The potential of sand as a support for immobilized enzymes was investigated by preparing alkylamine sand and devising methods to measure the total number of amine groups present and the fraction available for immobilization of enzymes. Alcohol dehydrogenase (alcohol: NAD oxidoreductase, EC 1.1.1.1.) and lactate dehydrogenase (L-lactate:NAD oxidoreductase, EC 1.1.1.27) were immobilized on alkylamine sand, and the stability of the immobilized protein and dehydrogenase activity was measured. Urease (urea amidohydrolase, EC 3.5.1.5) was also immobilized on sand to test the applicability of these methods to larger scale immobilizations. Results suggest that sand shows promise as a support for immobilized enzymes.