Multi-scale modelling of biological systems in process algebra

There is a growing interest in combining different levels of detail of biological phenomena into unique multi-scale models that represent both biochemical details and higher order structures such as cells, tissues or organs. The state of the art of multi-scale models presents a variety of approaches often tailored around specific problems and composed of a combination of mathematical techniques. As a result, these models are difficult to build, compose, compare and analyse. In this thesis we identify process algebra as an ideal formalism to multi-scale modelling of biological systems. Building on an investigation of existing process algebras, we define process algebra with hooks (PAH), designed to be a middle-out approach to multi-scale modelling. The distinctive features of PAH are: the presence of two synchronisation operators, distinguishing interactions within and between scales, and composed actions, representing events that occur at multiple scales. A stochastic semantics is provided, based on functional rates derived from kinetic laws. A parametric version of the algebra ensures that a model description is compact. This new formalism allows for: unambiguous definition of scales as processes and interactions within and between scales as actions, compositionality between scales using a novel vertical cooperation operator and compositionality within scales using a traditional cooperation operator, and relating models and their behaviour using equivalence relations that can focus on specified scales. Finally, we apply PAH to define, compose and relate models of pattern formation and tissue growth, highlighting the benefits of the approach

Some investigations concerning the CTMC and the ODE model derived from Bio-PEPA

<p>Bio-PEPA is a recently defined language for the modelling and analysis of biochemical networks. It supports an abstract style of modelling, in which discrete levels of concentration within a species are considered instead of individual molecules. A finer granularity for the system corresponds to a smaller concentration step size and therefore to a greater number of concentration levels. This style of model is amenable to a variety of different analysis techniques, including numerical analysis based on a CMTC with states reflecting the levels of concentration.</p> <p>In this paper we present a formal definition of the CTMC with levels derived from a Bio-PEPA system. Furthermore we investigate the relationship between this CTMC and the system of ordinary differential equations (ODEs) derived from the same model. Using Kurtz's theorem, we show that the set of ODEs derived from the Bio-PEPA model is able to capture the limiting behaviour of the CTMC obtained from the same system. Finally, we define an empirical methodology to find the granularity of the Bio-PEPA system for which the ODE and the CTMC with levels are in a good agreement. The proposed definition is based on a notion of distance between the two models. We demonstrate our approach on a model of the Repressilator, a simple biochemical network with oscillating behaviour.</p&gt

The perioperative period of liver transplantation from unconventional extended criteria donors: data from two high-volume centres

Background: As literature largely focuses on long-term outcomes, this study aimed at elucidating the perioperative outcomes of liver transplant patients receiving a graft from two groups of unconventional expanded criteria donors: brain dead aged > 80 years and cardiac dead.Methods: Data of 247 cirrhotic patients transplanted at two high volume liver transplant centers were analysed. Confounders were balanced using a stabilized inverse probability therapy weighting and a propensity score for each patient on the original population was generated. The score was created using a multivariate logistic regression model considering a Comprehensive Complication Index & GE; 42 (no versus yes) as the dependent variable and 11 possible clinically relevant confounders as covariate.Results: Forty-four patients received the graft from a cardiac-dead donor and 203 from a brain-dead donor aged > 80 years. Intraoperatively, cardiac-dead donors liver transplant cases required more fresh frozen plasma units (P < 0.0001) with similar reduced need of fibrinogen to old brain-dead donors cases. The incidence of reperfusion syndrome was similar (P = 0.80). In the Intensive Care Unit, both the groups presented a comparable low need for blood transfusions, renal replacement therapy and inotropes. Cardiac-dead donors liver transplantations required more time to tracheal extubation (P < 0.0001) and scored higher Comprehensive Complication Index (P < 0.0001) however the incidence of a severe complication status (Comprehensive Complication Index & GE; 42) was similar (P = 0.52). ICU stay (P = 0.97), total hospital stay (P = 0.57), in hospital (P = 1.00) and 6 months (P = 1.00) death were similar.Conclusion: Selected octogenarian and cardiac-dead donors can be used safely for liver transplantation

A living biobank of canine mammary tumor organoids as a comparative model for human breast cancer.

Mammary tumors in dogs hold great potential as naturally occurring breast cancer models in translational oncology, as they share the same environmental risk factors, key histological features, hormone receptor expression patterns, prognostic factors, and genetic characteristics as their human counterparts. We aimed to develop in vitro tools that allow functional analysis of canine mammary tumors (CMT), as we have a poor understanding of the underlying biology that drives the growth of these heterogeneous tumors. We established the long-term culture of 24 organoid lines from 16 dogs, including organoids derived from normal mammary epithelium or benign lesions. CMT organoids recapitulated key morphological and immunohistological features of the primary tissue from which they were derived, including hormone receptor status. Furthermore, genetic characteristics (driver gene mutations, DNA copy number variations, and single-nucleotide variants) were conserved within tumor-organoid pairs. We show how CMT organoids are a suitable model for in vitro drug assays and can be used to investigate whether specific mutations predict therapy outcomes. Specifically, certain CMT subtypes, such as PIK3CA mutated, estrogen receptor-positive simple carcinomas, can be valuable in setting up a preclinical model highly relevant to human breast cancer research. In addition, we could genetically modify the CMT organoids and use them to perform pooled CRISPR/Cas9 screening, where library representation was accurately maintained. In summary, we present a robust 3D in vitro preclinical model that can be used in translational research, where organoids from normal, benign as well as malignant mammary tissues can be propagated from the same animal to study tumorigenesis

Author Correction: A practical guide for mutational signature analysis in hematological malignancies.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Report from the 4th European Bone Sarcoma Networking meeting: focus on osteosarcoma

Abstract This report summarizes the proceedings of the 4th European Bone Sarcoma Networking Meeting, held in London, England, on 21 June 2017. The meeting brought together scientific and clinical researchers and representatives from sarcoma charities from 19 countries representing five networks across Europe, to present and discuss new developments on bone sarcoma. In view of the challenges is poses, the meeting focussed primarily on osteosarcoma with presentations on developments in our understanding of osteosarcoma genetics and immunology as well as results from preclinical investigations and discussion of recent and ongoing clinical trials. These include studies examining the efficacy of multi-targeted tyrosine kinase inhibitors and checkpoint inhibitors, as well as those with molecular profiling to stratify patients for specific therapies. Discussion was centred on generation of new hypotheses for collaborative biological and clinical investigations, the ultimate goal being to improve therapy and outcome in patients with bone sarcomas

Dramatic response of metastatic cutaneous angiosarcoma to an immune checkpoint inhibitor in a patient with xeroderma pigmentosum: whole-genome sequencing aids treatment decision in end-stage disease.

"Mutational signatures" are patterns of mutations that report DNA damage and subsequent repair processes that have occurred. Whole-genome sequencing (WGS) can provide additional information to standard diagnostic techniques and can identify therapeutic targets. A 32-yr-old male with xeroderma pigmentosum developed metastatic angiosarcoma that was unresponsive to three lines of conventional sarcoma therapies. WGS was performed on his primary cancer revealing a hypermutated tumor, including clonal ultraviolet radiation-induced mutational patterns (Signature 7) and subclonal signatures of mutated DNA polymerase epsilon (POLE) (Signature 10). These signatures are associated with response to immune checkpoint blockade. Immunohistochemistry confirmed high PD-L1 expression in metastatic deposits. The anti-PD-1 monoclonal antibody pembrolizumab was commenced off-label given the POLE mutation and high mutational load. After four cycles, there was a significant reduction in his disease with almost complete resolution of the metastatic deposits. This case highlights the importance of WGS in the analysis, interpretation, and treatment of cancers. We anticipate that as WGS becomes integral to the cancer diagnostic pathway, treatments will be stratified to the individual based on their unique genomic and/or transcriptomic profile, enhancing classical approaches of histologically driven treatment decisions

A systematic CRISPR screen defines mutational mechanisms underpinning signatures caused by replication errors and endogenous DNA damage.

Mutational signatures are imprints of pathophysiological processes arising through tumorigenesis. We generated isogenic CRISPR-Cas9 knockouts (Δ) of 43 genes in human induced pluripotent stem cells, cultured them in the absence of added DNA damage, and performed whole-genome sequencing of 173 subclones. ΔOGG1, ΔUNG, ΔEXO1, ΔRNF168, ΔMLH1, ΔMSH2, ΔMSH6, ΔPMS1, and ΔPMS2 produced marked mutational signatures indicative of being critical mitigators of endogenous DNA modifications. Detailed analyses revealed mutational mechanistic insights, including how 8-oxo-dG elimination is sequence-context-specific while uracil clearance is sequence-context-independent. Mismatch repair (MMR) deficiency signatures are engendered by oxidative damage (C>A transversions), differential misincorporation by replicative polymerases (T>C and C>T transitions), and we propose a 'reverse template slippage' model for T>A transversions. ΔMLH1, ΔMSH6, and ΔMSH2 signatures were similar to each other but distinct from ΔPMS2. Finally, we developed a classifier, MMRDetect, where application to 7,695 WGS cancers showed enhanced detection of MMR-deficient tumors, with implications for responsiveness to immunotherapies

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Process evaluation of the Bridging the Age Gap in Breast Cancer decision support intervention cluster randomized trial [abstract only]

Aims/Objectives: Shared decision making on the choice of treatment for older women with breast cancer involves many factors. Comprehensive geriatric assessment (CGA) is recognised to have a role in older patients with cancer, but how this should be utilised is still debatable. A pilot study involving older women newly diagnosed with early operable primary breast cancer was conducted aiming to explore the potential value of CGA. Methods: Decision of primary treatment followed consultation with the clinical team and was not guided by any aspect of this study. CGA, using a validated cancer-specific tool from our collaborator, A Hurria, was conducted within 6 weeks after diagnosis, regardless of date of surgery/first treatment. A total of 178 female patients aged ≥70 years with a new diagnosis of early (stage 1 or 2; cT0-2, N0-1, M0) operable primary breast cancer proven histologically, were thus far recruited from three UK centres. Results: Among these 178 patients, 149 underwent primary surgery and 29 received non-surgical treatment (primary endocrine therapy (N=28) or radiotherapy (N=1)). CGA determined that increasing age (p=0.006), reduced independence with activities of daily living (ADLs) (p=0.001) and independent activities of daily living (IADLS) (p=0.001), increased number and severity of comorbidity (p=0.043), reduced Karnofsky performance status when rated both by the patient (p=0.001) and physician (p=0.003), were significantly related to non-surgical treatment within 6 weeks after diagnosis. Other CGA parameters measured which were not significant include number of daily medications, level of social support, level of social activity, cognition, number of falls, 'Timed up and go' score. Conclusions: The pilot study has confirmed that CGA may have value in assessing this cohort of patients. Generally, it appears that patients receiving non-surgical treatment are more frail than their counterparts undergoing surgery. The study is ongoing and has expanded to include an international centre