This first-in-human dose-escalation trial evaluated the safety, tolerability, maximal-tolerated dose (MTD), dose-limiting toxicities (DLT), pharmacokinetics, pharmacodynamics, and preliminary ...clinical activity of pictilisib (GDC-0941), an oral, potent, and selective inhibitor of the class I phosphatidylinositol-3-kinases (PI3K).
Sixty patients with solid tumors received pictilisib at 14 dose levels from 15 to 450 mg once-daily, initially on days 1 to 21 every 28 days and later, using continuous dosing for selected dose levels. Pharmacodynamic studies incorporated (18)F-FDG-PET, and assessment of phosphorylated AKT and S6 ribosomal protein in platelet-rich plasma (PRP) and tumor tissue.
Pictilisib was well tolerated. The most common toxicities were grade 1-2 nausea, rash, and fatigue, whereas the DLT was grade 3 maculopapular rash (450 mg, 2 of 3 patients; 330 mg, 1 of 7 patients). The pharmacokinetic profile was dose-proportional and supported once-daily dosing. Levels of phosphorylated serine-473 AKT were suppressed >90% in PRP at 3 hours after dose at the MTD and in tumor at pictilisib doses associated with AUC >20 h·μmol/L. Significant increase in plasma insulin and glucose levels, and >25% decrease in (18)F-FDG uptake by PET in 7 of 32 evaluable patients confirmed target modulation. A patient with V600E BRAF-mutant melanoma and another with platinum-refractory epithelial ovarian cancer exhibiting PTEN loss and PIK3CA amplification demonstrated partial response by RECIST and GCIG-CA125 criteria, respectively.
Pictilisib was safely administered with a dose-proportional pharmacokinetic profile, on-target pharmacodynamic activity at dose levels ≥100 mg and signs of antitumor activity. The recommended phase II dose was continuous dosing at 330 mg once-daily.
Cells respond to DNA damage or defects in the mitotic spindle by activating checkpoints that arrest the cell cycle. Alternatively, damaged cells can undergo cell death by the process of apoptosis. ...The correct balance between these pathways is important for the maintenance of genomic integrity while preventing unnecessary cell death. Although the molecular mechanisms of the cell cycle and apoptosis have been elucidated, the links between them have not been clear. Recent work, however, indicates that common components directly link the regulation of apoptosis with cell-cycle checkpoints operating during interphase, whereas in mitosis, the control of apoptosis is directly coupled to the cell-cycle machinery. These findings shed new light on how the balance between cell-cycle progression and cell death is controlled.
The molecular chaperone heat shock protein 90 (HSP90) is required for the activity and stability of its client proteins. Pharmacologic inhibition of HSP90 leads to the ubiquitin-mediated degradation ...of clients, particularly activated or mutant oncogenic protein kinases. Client ubiquitination occurs via the action of one or more E3 ubiquitin ligases. We sought to identify the role of Cullin-RING family E3 ubiquitin ligases in the cellular response to HSP90 inhibition. Through a focused siRNA screen of 28 Cullin-RING ligase family members, we found that CUL5 and RBX2 were required for degradation of several HSP90 clients upon treatment of human cancer cells with the clinical HSP90 inhibitor 17-AAG. Surprisingly, silencing Cullin-5 (CUL5) also delayed the earlier loss of HSP90 client protein activity at the same time as delaying cochaperone dissociation from inhibited HSP90–client complexes. Expression of a dominant-negative CUL5 showed that NEDD8 conjugation of CUL5 is required for client degradation but not for loss of client activity or recruitment of clients and HSP90 to CUL5. Silencing CUL5 reduced cellular sensitivity to three distinct HSP90 inhibitors, across four cancer types driven by different protein kinases. Our results reveal the importance of CUL5 in multiple aspects of the cellular response to HSP90 inhibition.
Context Open Source Software (OSS) development is a knowledge focused activity which relies heavily on contributors who can be volunteers or paid workers and are geographically distributed. While ...working on OSS projects contributors acquire project related individualistic knowledge and gain experience and skills, which often remains unshared with others and is usually lost once contributors leave a project. All software development organisations face the problem of knowledge loss as employees leave, but this situation is exasperated in OSS projects where most contributors are volunteers with largely unpredictable engagement durations. Contributor turnover is inevitable due to the transient nature of OSS project workforces causing knowledge loss, which threatens the overall sustainability of OSS projects and impacts negatively on software quality and contributor productivity.
The objective of this work is to deeply and systematically investigate the phenomenon of knowledge loss due to contributor turnover in OSS projects as presented in the state-of-the-art literature and to synthesise the information presented on the topic. Furthermore, based on the learning arising from our investigation it is our intention to identify mechanisms to reduce the overall effects of knowledge loss in OSS projects.
We use the snowballing methodology to identify the relevant literature on knowledge loss due to contributor turnover in OSS projects. This robust methodology for a literature review includes research question, search strategy, inclusion, exclusion, quality criteria, and data synthesis. The search strategy, and inclusion, exclusions and quality criteria are applied as a part of snowballing procedure.
Snowballing is considered an efficient and reliable way to conduct a systematic literature review, providing a robust alternative to mechanically searching individual databases for given topics.
Knowledge sharing in OSS projects is abundant but there is no evidence of a formal strategy or practice to manage knowledge. Due to the dynamic and diverse nature of OSS projects, knowledge management is considered a challenging task and there is a need for a proactive mechanism to share knowledge in the OSS community for knowledge to be reused in the future by the OSS project contributors. From the collection of papers found using snowballing, we consolidated various themes on knowledge loss due to contributor turnover in OSS projects and identified 11 impacts due to knowledge loss in OSS projects, and 10 mitigations to manage with knowledge loss in OSS projects.
In this paper, we propose future research directions to investigate integration of proactive knowledge retention practices with the existing OSS practices to reduce the current knowledge loss problem. We suggest that there is insufficient attention paid to KM in general in OSS, in particular there would appear to an absence of proactive measures to reduce the potential impact of knowledge loss. We also propose the need for a KM evaluation metric in OSS projects, similar to the ones that evaluate health of online communities, which should help to inform potential consumers of the OSS of the KM status on a project, something that is not existent today.
Checkpoint kinase 1 (CHK1) is a key mediator of the DNA damage response that regulates cell-cycle progression, DNA damage repair, and DNA replication. Small-molecule CHK1 inhibitors sensitize cancer ...cells to genotoxic agents and have shown single-agent preclinical activity in cancers with high levels of replication stress. However, the underlying genetic determinants of CHK1 inhibitor sensitivity remain unclear. We used the developmental clinical drug SRA737 in an unbiased large-scale siRNA screen to identify novel mediators of CHK1 inhibitor sensitivity and uncover potential combination therapies and biomarkers for patient selection. We identified subunits of the B-family of DNA polymerases (
, and
) whose silencing sensitized the human A549 non-small cell lung cancer (NSCLC) and SW620 colorectal cancer cell lines to SRA737. B-family polymerases were validated using multiple siRNAs in a panel of NSCLC and colorectal cancer cell lines. Replication stress, DNA damage, and apoptosis were increased in human cancer cells following depletion of the B-family DNA polymerases combined with SRA737 treatment. Moreover, pharmacologic blockade of B-family DNA polymerases using aphidicolin or CD437 combined with CHK1 inhibitors led to synergistic inhibition of cancer cell proliferation. Furthermore, low levels of POLA1, POLE, and POLE2 protein expression in NSCLC and colorectal cancer cells correlated with single-agent CHK1 inhibitor sensitivity and may constitute biomarkers of this phenotype. These findings provide a potential basis for combining CHK1 and B-family polymerase inhibitors in cancer therapy. SIGNIFICANCE: These findings demonstrate how the therapeutic benefit of CHK1 inhibitors may potentially be enhanced and could have implications for patient selection and future development of new combination therapies.
Importin-α serves as an adaptor linking importin-β to proteins carrying a nuclear localization sequence (NLS). During interphase, this interaction enables nuclear protein import, while in mitosis it ...regulates spindle assembly factors (SAFs) and controls microtubule nucleation, stabilization and spindle function. Here, we show that human importin-α1 is regulated during the cell cycle and is phosphorylated at two sites (threonine 9 and serine 62) during mitosis by the major mitotic protein kinase CDK1-cyclin B. Mutational analysis indicates that the mitotic phosphorylation of importin-α1 inhibits its binding to importin-β and promotes the release of TPX2 and KIFC1, which are then targeted like importin-β to the spindle. Loss of importin-α1 or expression of a non-phosphorylated mutant of importin-α1 results in the formation of shortened spindles with reduced microtubule density and induces a prolonged metaphase, whereas phosphorylation-mimicking mutants are functional in mitosis. We propose that phosphorylation of importin-α1 is a general mechanism for the spatial and temporal control of mitotic spindle assembly by CDK1-cyclin B1 that acts through the release of SAFs such as TPX2 and KIFC1 from inhibitory complexes that restrict spindle assembly.
Highlights • Genome-based cancer therapeutics and precision oncology. • Cancer drug targets. • Kinase inhibitors. • Drug resistance. • Combinatorial therapy.
The Mediator complex-associated cyclin-dependent kinase CDK8 has been implicated in human disease, particularly in colorectal cancer where it has been reported as a putative oncogene. Here we report ...the discovery of 109 (CCT251921), a potent, selective, and orally bioavailable inhibitor of CDK8 with equipotent affinity for CDK19. We describe a structure-based design approach leading to the discovery of a 3,4,5-trisubstituted-2-aminopyridine series and present the application of physicochemical property analyses to successfully reduce in vivo metabolic clearance, minimize transporter-mediated biliary elimination while maintaining acceptable aqueous solubility. Compound 109 affords the optimal compromise of in vitro biochemical, pharmacokinetic, and physicochemical properties and is suitable for progression to animal models of cancer.
In neonatal encephalopathy, the clinical manifestations of injury can only be reliably assessed several years after an intervention, complicating early prognostication and rendering trials of ...promising neuroprotectants slow and expensive. We aimed to determine the accuracy of thalamic proton magnetic resonance (MR) spectroscopy (MRS) biomarkers as early predictors of the neurodevelopmental abnormalities observed years after neonatal encephalopathy.
We did a prospective multicentre cohort study across eight neonatal intensive care units in the UK and USA, recruiting term and near-term neonates who received therapeutic hypothermia for neonatal encephalopathy. We excluded infants with life-threatening congenital malformations, syndromic disorders, neurometabolic diseases, or any alternative diagnoses for encephalopathy that were apparent within 6 h of birth. We obtained T1-weighted, T2-weighted, and diffusion-weighted MRI and thalamic proton MRS 4–14 days after birth. Clinical neurodevelopmental tests were done 18–24 months later. The primary outcome was the association between MR biomarkers and an adverse neurodevelopmental outcome, defined as death or moderate or severe disability, measured using a multivariable prognostic model. We used receiver operating characteristic (ROC) curves to examine the prognostic accuracy of the individual biomarkers. This trial is registered with ClinicalTrials.gov, number NCT01309711.
Between Jan 29, 2013, and June 25, 2016, we recruited 223 infants who all underwent MRI and MRS at a median age of 7 days (IQR 5–10), with 190 (85%) followed up for neurological examination at a median age of 23 months (20–25). Of those followed up, 31 (16%) had moderate or severe disability, including one death. Multiple logistic regression analysis could not be done because thalamic N-acetylaspartate (NAA) concentration alone accurately predicted an adverse neurodevelopmental outcome (area under the curve AUC of 0·99 95% CI 0·94–1·00; sensitivity 100% 74–100; specificity 97% 90–100; n=82); the models would not converge when any additional variable was examined. The AUC (95% CI) of clinical examination at 6 h (n=190) and at discharge (n=167) were 0·72 (0·65–0·78) and 0·60 (0·53–0·68), respectively, and the AUC of abnormal amplitude integrated EEG at 6 h (n=169) was 0·73 (0·65–0·79). On conventional MRI (n=190), cortical injury had an AUC of 0·67 (0·60–0·73), basal ganglia or thalamic injury had an AUC of 0·81 (0·75–0·87), and abnormal signal in the posterior limb of internal capsule (PLIC) had an AUC of 0·82 (0·76–0·87). Fractional anisotropy of PLIC (n=65) had an AUC of 0·82 (0·76–0·87). MRS metabolite peak-area ratios (n=160) of NAA–creatine (<1·29) had an AUC of 0·79 (0·72–0·85), of NAA–choline had an AUC of 0·74 (0·66–0·80), and of lactate–NAA (>0·22) had an AUC of 0·94 (0·89–0·97).
Thalamic proton MRS measures acquired soon after birth in neonatal encephalopathy had the highest accuracy to predict neurdevelopment 2 years later. These methods could be applied to increase the power of neuroprotection trials while reducing their duration.
National Institute for Health Research UK.
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