Mechanisms that promote liberation of mitotic stress-induced death

Paclitaxel is an anti-mitotic drug that, due to its success in the clinic, has become a backbone of first-line chemotherapeutic regimens for many malignancies including non-small cell lung cancer (NSCLC). While paclitaxel-based regimens are efficacious for some NSCLC patients, response is often incomplete, rarely curative and unpredictable, indicating widespread intrinsic resistance in chemo-naive tumors. Thus, there is an unmet need for new combinatorial treatment strategies to better target paclitaxel resistant tumor cells. To study the molecular basis for this resistance, we first established a test bed of NSCLC-derived cell lines that evade cell death from high concentrations of paclitaxel due to an uncoupling of mitotic damage from cell death. We then employed a genome-wide loss-of-function cytotoxic screen to identify the molecular components that can re-engage paclitaxel-mediated cell death programs in an otherwise paclitaxel-resistant background. This screen was performed in the presence and absence of a mitotic damaging, yet sub-lethal, dose of paclitaxel. This approach revealed a cohort of proteins that support tumor cell viability in the presence of mitotic damage. From this study, we find that prolonging a mitotic delay, by inhibition of either the APC or novel mitotic regulators, CASC1 and TRIM69, collaborates with a sub-lethal dose of paclitaxel to engage cell death programs. In particular, we find that CASC1, which is frequently co-amplified with KRAS, is essential for microtubule polymerization and mitotic spindle formation. We also identified TRIM69, an E3 ubiquitin ligase, that we find is recruited to the spindle poles during mitosis to support mitotic fidelity. Importantly, stable depletion of either CASC1, or TRIM69, attenuates tumor cell growth in vivo. Finally, we demonstrate that pharmacological inhibition of the APC collaborates with an otherwise sublethal dose of paclitaxel. We hypothesize that during the course of tumor evolution, cancer cells become dependent on mechanisms that support rapid and inappropriate mitotic exit for cell viability and that these same intrinsic mechanisms are engaged to evade anti-mitotic therapeutics. Thus, therapeutic strategies that can prolong a mitotic delay may enhance patient response to paclitaxel-based therapies.Doctor of Philosoph

Influences on Decision-Making Regarding Antipsychotic Prescribing in Nursing Home Residents With Dementia: A Systematic Review and Synthesis of Qualitative Evidence.

BACKGROUND: Antipsychotic prescribing is prevalent in nursing homes for the management of behavioral and psychological symptoms of dementia (BPSD), despite the known risks and limited effectiveness. Many studies have attempted to understand this continuing phenomenon, using qualitative research methods, and have generated varied and sometimes conflicting findings. To date, the totality of this qualitative evidence has not been systematically collated and synthesized. AIMS: To synthesize the findings from individual qualitative studies on decision-making and prescribing behaviors for antipsychotics in nursing home residents with dementia, with a view to informing intervention development and quality improvement in this field. METHODS: A systematic review and synthesis of qualitative evidence was conducted (PROSPERO protocol registration CRD42015029141). Six electronic databases were searched systematically from inception through July 2016 and supplemented by citation, reference, and gray literature searching. Studies were included if they used qualitative methods for both data collection and analysis, and explored antipsychotic prescribing in nursing homes for the purpose of managing BPSD. The Critical Appraisal Skills Program assessment tool was used for quality appraisal. A meta-ethnography was conducted to synthesize included studies. The Confidence in the Evidence from Reviews of Qualitative research approach was used to assess the confidence in individual review findings. All stages were conducted by at least 2 independent reviewers. RESULTS: Of 1534 unique records identified, 18 met the inclusion criteria. Five key concepts emerged as influencing decision-making: organizational capacity; individual professional capability; communication and collaboration; attitudes; regulations and guidelines. A "line of argument" was synthesized and a conceptual model constructed, comparing this decision-making process to a dysfunctional negative feedback loop. Our synthesis indicates that when all stakeholders come together to communicate and collaborate as equal and empowered partners, this can result in a successful reduction in inappropriate antipsychotic prescribing. CONCLUSIONS: Antipsychotic prescribing in nursing home residents with dementia occurs in a complex environment involving the interplay of various stakeholders, the nursing home organization, and external influences. To improve the quality of antipsychotic prescribing in this cohort, a more holistic approach to BPSD management is required. Although we have found the issue of antipsychotic prescribing has been extensively explored using qualitative methods, there remains a need for research focusing on how best to change the prescribing behaviors identified

Differential cell responses to nanoparticle docetaxel and small molecule docetaxel at a sub-therapeutic dose range

Current preclinical evaluations of nanoparticle taxanes have focused on the effect of nanoparticle size and shape on the efficacy and toxicity. It is generally assumed that nanoparticle therapeutics have the same cellular response on tumor and normal cells as their small molecule counterparts. Here, we show that nanoparticle taxanes can mediate cellular effects distinct from that of small molecule taxanes at the sub-therapeutic dose range. Cells that are exposed to two polymeric nanoparticle formulations of docetaxel were found to undergo a different cell cycle and cell fate than that of cells that were exposed to small molecule docetaxel. Our results suggest that nanoparticle formulation of therapeutics can affect the therapeutic effect of its cargo

Mechanisms Promoting Escape from Mitotic Stress-Induced Tumor Cell Death

Non-small cell lung cancer (NSCLC) is notorious for its paltry responses to first-line therapeutic regimens. In contrast to acquired chemoresistance, little is known about the molecular underpinnings of the intrinsic resistance of chemo-naïve NSCLC. Here we report that intrinsic resistance to paclitaxel in NSCLC occurs at a cell-autonomous level due to the uncoupling of mitotic defects from apoptosis. To identify components that permit escape from mitotic stress-induced death, we employed a genome-wide RNAi-based strategy, which combines a high-throughput toxicity screen with a live-cell imaging platform to measure mitotic fate. This strategy revealed that prolonging mitotic arrest with a small molecule inhibitor of the APC/Cyclosome could sensitize otherwise paclitaxel-resistant NSCLC. We also defined novel roles for CASC1 and TRIM69 in supporting resistance to spindle poisons. CASC1, which is frequently co-amplified with KRAS in lung tumors, is essential for microtubule polymerization and satisfaction of the spindle assembly checkpoint. TRIM69, which associates with spindle poles and promotes centrosomal clustering, is essential for formation of a bipolar spindle. Notably, RNAi-mediated attenuation of CASC1 or TRIM69 was sufficient to inhibit tumor growth in vivo. On the basis of our results, we hypothesize that tumor evolution selects for a permissive mitotic checkpoint, which may promote survival despite chromosome segregation errors. Attacking this adaptation may restore the apoptotic consequences of mitotic damage to permit the therapeutic eradication of drug-resistant cancer cells

Reengineering a receptor footprint of adeno-associated virus enables selective and systemic gene transfer to muscle

Reengineering the receptor footprints of adeno-associated virus (AAV) isolates may yield variants with improved properties for clinical applications. We generated a panel of synthetic AAV2 vectors by replacing a hexapeptide sequence in a previously identified heparan sulfate receptor footprint with corresponding residues from other AAV strains. This approach yielded several chimeric capsids displaying systemic tropism after intravenous administration in mice. Of particular interest, an AAV2/AAV8 chimera designated AAV2i8 displayed an altered antigenic profile, readily traversed the blood vasculature, and selectively transduced cardiac and whole-body skeletal muscle tissues with high efficiency. Unlike other AAV serotypes, which are preferentially sequestered in the liver, AAV2i8 showed markedly reduced hepatic tropism. These features of AAV2i8 suggest that it is well suited to translational studies in gene therapy of musculoskeletal disorders

Predicting reliability through structured expert elicitation with the repliCATS (Collaborative Assessments for Trustworthy Science) process

As replications of individual studies are resource intensive, techniques for predicting the replicability are required. We introduce the repliCATS (Collaborative Assessments for Trustworthy Science) process, a new method for eliciting expert predictions about the replicability of research. This process is a structured expert elicitation approach based on a modified Delphi technique applied to the evaluation of research claims in social and behavioural sciences. The utility of processes to predict replicability is their capacity to test scientific claims without the costs of full replication. Experimental data supports the validity of this process, with a validation study producing a classification accuracy of 84% and an Area Under the Curve of 0.94, meeting or exceeding the accuracy of other techniques used to predict replicability. The repliCATS process provides other benefits. It is highly scalable, able to be deployed for both rapid assessment of small numbers of claims, and assessment of high volumes of claims over an extended period through an online elicitation platform, having been used to assess 3000 research claims over an 18 month period. It is available to be implemented in a range of ways and we describe one such implementation. An important advantage of the repliCATS process is that it collects qualitative data that has the potential to provide insight in understanding the limits of generalizability of scientific claims. The primary limitation of the repliCATS process is its reliance on human-derived predictions with consequent costs in terms of participant fatigue although careful design can minimise these costs. The repliCATS process has potential applications in alternative peer review and in the allocation of effort for replication studies