Modelling of Tirapazamine effects on solid tumour morphology

Bioreductive drugs are in clinical practice to exploit the resistance from tumour microenvironments especially in the hypoxic region of tumour. We pre-sented a tumour treatment model to capture the pharmacology of one of the most prominent bioreductive drugs, Tirapazamine (TPZ) which is in clinical trials I and II. We calculated solid tumour mass in our previous work and then integrated that model with TPZ infusion. We calculated TPZ cytotoxicity, concentration, penetra-tion with increasing distance from blood vessel and offered resistance from micro-environments for drug penetration inside the tumour while considering each cell as an individual entity. The impact of these factors on tumour morphology is also showed to see the drug behaviour inside animals/humans tumours. We maintained the heterogeneity factors in presented model as observed in real tumour mass es-pecially in terms of cells proliferation, cell movement, extracellular matrix (ECM) interaction, and the gradients of partial oxygen pressure (pO2) inside tumour cells during the whole growth and treatment activity. The results suggest that TPZ high concentration in combination with chemotherapy should be given to get maximum abnormal cell killing. This model can be a good choice for oncologists and re-searchers to explore more about TPZ action inside solid tumour

Modeling Three-dimensional Invasive Solid Tumor Growth in Heterogeneous Microenvironment under Chemotherapy

A systematic understanding of the evolution and growth dynamics of invasive solid tumors in response to different chemotherapy strategies is crucial for the development of individually optimized oncotherapy. Here, we develop a hybrid three-dimensional (3D) computational model that integrates pharmacokinetic model, continuum diffusion-reaction model and discrete cell automaton model to investigate 3D invasive solid tumor growth in heterogeneous microenvironment under chemotherapy. Specifically, we consider the effects of heterogeneous environment on drug diffusion, tumor growth, invasion and the drug-tumor interaction on individual cell level. We employ the hybrid model to investigate the evolution and growth dynamics of avascular invasive solid tumors under different chemotherapy strategies. Our simulations reproduce the well-established observation that constant dosing is generally more effective in suppressing primary tumor growth than periodic dosing, due to the resulting continuous high drug concentration. In highly heterogeneous microenvironment, the malignancy of the tumor is significantly enhanced, leading to inefficiency of chemotherapies. The effects of geometrically-confined microenvironment and non-uniform drug dosing are also investigated. Our computational model, when supplemented with sufficient clinical data, could eventually lead to the development of efficient in silico tools for prognosis and treatment strategy optimization.Comment: 41 pages, 8 figure

Rational enzyme-directed prodrug development : exploiting tumour hypoxia to target the bioactivation of cytotoxic prodrugs

Conventional cancer chemotherapy often lacks specificity and is consequently associated with significant normal tissue toxicities. Molecular chemotherapy offers the potential to target the activation of inert prodrugs by utilising tumour-specific catalytic enzymes to restrict cytotoxicity to neoplastic tissues. Appropriate expression of therapeutic enzymes can be achieved by exploiting the genetic distinctions that exist between tumour and normal tissues through the use of tissue- or disease-specific promoters. Alternatively, the unique physiological differences that arise in solid tumour masses as a consequence of the abnormal vascular architecture might also be exploited to achieve therapeutic selectivity. The most conspicuous of these differences is the presence of areas of low oxygen tension (hypoxia) arising through both diffusion and perfusion-limited oxygen availability. Hypoxia is an important cause of radioresistance and is a independent prognostic indicator for local recurrence, metastatic spread and overall survival. Evidence also implicates hypoxia in chemotherapeutic resistance and genetic instability, as well as the progression of and selection for an aggressive neoplastic phenotype. Attempts to eliminate tumour hypoxia have met with some success, but the opportunity to utilise thisphenomenonfor therapeutic gain, through the exploitation of the unique reductive tissue environment have lead to the development of hypoxic-specific cytotoxins. These bioreductive prodrugs rely. on the natural complement of tumour enzymes to catalyse their activation under low tissue oxygen tensions. Levels of these reductases are potentially heterogeneous and are often down-regulated in the neoplastic state. The artificial reintroduction of high levels of reductive enzyme expression may be of significant therapeutic value, particularly if expression is restricted to the hypoxic tissue enviroment in which the prodrugs will be activated. This might be achieved through the utilisation of the specific cisacting sequences that are responsive to hypoxia-regulated transcription factors. A diverse spectrum of genes are known to be induced as a consequence of oxygen deprivation, being involved in systemic oxygen supply, vascular tone, neovascularisation, iron homeostasis, glucose metabolism, drug detoxification and protein chaperoning. The details of the cis-acting sequences and transcription factors that mediate this oxygen-sensitive gene control are beginning to emerge. This provides the opportunity to exploit these defined sequences to regulate therapeutic genes in a hypoxia-responsive manner. This thesis describes the evaluation of three potential prodruglenzyme paradigms that may have application in this context. Further, the potential of hypoxia-response-elements to specifically regulate heterologous genes in response to low oxygen tension is described. The application of such an oxygen-regulated gene-directed enzyme/prodrug therapy to solid tumours may provide chemotherapeutic specificity aimed at a clinically important tumour subpopulation

Use of horseradish peroxidase for gene directed enzyme prodrug therapy.

Gene directed enzyme prodrug therapy (GDEPT) is a form of targeted cancer therapy, where an enzyme is used to create a cytotoxin from a prodrug specifically within the tumour. The treatment of solid tumours is often hampered by the presence of hypoxia, which can limit the effectiveness of conventional therapies. Horseradish peroxidase (HRP)-directed GDEPT has been shown to target normoxic and hypoxic cells in monolayers. This study further evaluated HRP for gene therapy of cancer. The HRP/indole-3-acetic acid (HRP/IAA) combination was shown to retain its activity under the tumour-simulated conditions seen in 3-dimensional tumour cell spheroids. In particular, the halogenated derivative of IAA, 5-Br-IAA, showed specificity against larger spheroids, which contain significant regions of hypoxia. The use of alternative prodrugs was investigated using paracetamol. The HRP/paracetamol combination was effective in monolayers, even under the severe tumour-associated condition of anoxia. Following the successful in vitro investigations in the FaDu squamous carcinoma cell line, the HRP-GDEPT system was analysed in vivo. Characterisation of solid tumours grown from stable FaDu transfectants showed that the indole prodrugs had satisfactory pharmacokinetic profiles, and millimolar concentrations could be achieved in tumour tissue at non-toxic doses. The potential for the HRP/IAA system to cause delayed growth was determined using indoles, alone, and in combination with radiation. Unfortunately the HRP/IAA combination did not appear to have any reproducible growth delay effects. The immune response to HRP was assessed by generating murine carcinoma cells expressing HRP or the green fluorescent protein (GFP). However, passaging of the syngeneic cell line in vitro was sufficient to increase immunogenicity and decrease tumourigenicity even in the absence of transgene expression. Gene delivery in vivo was attempted in order to circumvent the use of stable transfectants. Electroporation could significantly increase the expression of GFP delivered intratumourally, although expression as a percentage of tumour area remained low. The data presented demonstrates the continued promise of the HRP-GDEPT system in vitro, but more work is required to improve the in vivo efficacy

Brain tumor quantification equation: modeled on complete step response algorithm

In Image Guided neuro-Surgery (IGnS) protocol relating to tumor, the planning stage is the bottleneck where most times are spent reconstructing the slices in order to; quantify the tumor, get the tumor shape and location relative to adjacent cells, and determine best incursion route among others. This time consuming assignment is handled by a surgeon using any of the standardized IGnS software. It has been observed that the approach taken to quantify tumor in those software are simply replicating the surgeons’ experience-based brain tumor quantification technique fashionable in the pre-imaging era. The result is a quantification method that is time consuming, and at bests an approximation. What is presented here is a novel brain tumor quantification method based on step response algorithm utilizing a model which itself was based on step response model resulting in smart and rapid quantification of brain tumor volume

Phenazine 5,10-dioxide analogues as drugs against acute myeloid leukaemia. -Preclinical documentation for lead selection

Postponed access: the file will be accessible after 2021-05-22Background: Acute Myeloid Leukaemia (AML) is a form of cancer that is associated with low survival rates, and where the current treatment is impaired by low tolerance and severe side-effects. Thus, novel treatments are needed to increase the life-expectancy of AMLpatients. The phenazine 5,10-dioxide compound, iodinin, has shown promising cytotoxic effects against AML cell lines in previous research. Iodinin itself has low solubility in aqueous media, and it was necessary to develop analogues with improved drug properties, which can be tested in animal models for toxicity and efficacy. Methods: The cytotoxicity of the analogues IM 5, IM 20, IM 56 and IM 69 was investigated by performing viability assays on OCI-AML-3 and MOLM-13 AML cell lines and comparing the results to previously obtained results for the normal cell lines rat kidney epithelial (NRK) and cardiac myeloblast (H9c2). The generation of reactive oxygen species (ROS), by a fluorescent reporter (DCF), was also investigated for MOLM-13 and H9c2 cells. Furthermore, key factors in ROS signalling were investigated by western blot. The physiochemical properties were studied by a screening assay for membrane permeability and in silicoprediction of properties important for permeability and biodistribution and linked to the biological activity of the analogues. Results: The analogue IM 56 showed increased cytotoxicity towards AML cell lines compared to the parent compound IM 5. It was also less toxic towards normal cell lines compared to the most frequently used AML drug, the anthracycline Daunorubicin. The difference in biological activities of the analogues is supported by their difference in membrane permeability. The analogues increase the generation of ROS in MOLM-13 cells. Except for the analogue IM 20, no such increase could be detected in H9c2 cells. Conclusion: The analogue IM 56 was chosen for further drug development, due to its enhanced effect against AML cell lines relative to normal cell lines. It increases cell death in MOLM-13 cells, most likely due to generation of ROS. IM 56 is thus a promising candidate for in vivo pre-clinical studies.Masteroppgåve i FarmasiFARM399/05HMATF-FAR

Structural Adaptation and Heterogeneity of Normal and Tumor Microvascular Networks

Relative to normal tissues, tumor microcirculation exhibits high structural and functional heterogeneity leading to hypoxic regions and impairing treatment efficacy. Here, computational simulations of blood vessel structural adaptation are used to explore the hypothesis that abnormal adaptive responses to local hemodynamic and metabolic stimuli contribute to aberrant morphological and hemodynamic characteristics of tumor microcirculation. Topology, vascular diameter, length, and red blood cell velocity of normal mesenteric and tumor vascular networks were recorded by intravital microscopy. Computational models were used to estimate hemodynamics and oxygen distribution and to simulate vascular diameter adaptation in response to hemodynamic, metabolic and conducted stimuli. The assumed sensitivity to hemodynamic and conducted signals, the vascular growth tendency, and the random variability of vascular responses were altered to simulate ‘normal’ and ‘tumor’ adaptation modes. The heterogeneous properties of vascular networks were characterized by diameter mismatch at vascular branch points (d3var) and deficit of oxygen delivery relative to demand (O2def). In the tumor, d3var and O2def were higher (0.404 and 0.182) than in normal networks (0.278 and 0.099). Simulated remodeling of the tumor network with ‘normal’ parameters gave low values (0.288 and 0.099). Conversely, normal networks attained tumor-like characteristics (0.41 and 0.179) upon adaptation with ‘tumor’ parameters, including low conducted sensitivity, increased growth tendency, and elevated random biological variability. It is concluded that the deviant properties of tumor microcirculation may result largely from defective structural adaptation, including strongly reduced responses to conducted stimuli

An in silico model to demonstrate the effects of Maspin on cancer cell dynamics

Most cancer treatments efficacy depends on tumor metastasis suppression, where tumor suppressor genes play an important role. Maspin (Mammary Serine Protease Inhibitor), an non-inhibitory serpin has been reported as a potential tumor suppressor to influence cell migration, adhesion, proliferation and apoptosis in in vitro and in vivo experiments in last two decades. Lack of computational investigations hinders its ability to go through clinical trials. Previously, we reported first computational model for maspin effects on tumor growth using artificial neural network and cellular automata paradigm with in vitro data support. This paper extends the previous in silico model by encompassing how maspin influences cell migration and the cell–extracellular matrix interaction in subcellular level. A feedforward neural network was used to define each cell behavior (proliferation, quiescence, apoptosis) which followed a cell-cycle algorithm to show the microenvironment impacts over tumor growth. Furthermore, the model concentrates how the in silico experiments results can further confirm the fact that maspin reduces cell migration using specific in vitro data verification method. The data collected from in vitro and in silico experiments formulates an unsupervised learning problem which can be solved by using different clustering algorithms. A density based clustering technique was developed to measure the similarity between two datasets based on the number of links between instances. Our proposed clustering algorithm first finds the nearest neighbors of each instance, and then redefines the similarity between pairs of instances in terms of how many nearest neighbors share the two instances. The number of links between two instances is defined as the number of common neighbors they have. The results showed significant resemblances with in vitro experimental data. The results also offer a new insight into the dynamics of maspin and establish as a metastasis suppressor gene for further molecular research

CT-PET guided target delineation in head and neck cancer and implications for improved outcome

Aim: Fifty percent of patients with squamous cell carcinoma of the Head and Neck develop loco-regional recurrence after treatment. Factors leading to this failure are most likely altered intra-tumoural glucose metabolism and increased hypoxia. Tissue glucose utilisation and the degree of hypoxia can be visualised by CTPET imaging with 18FDG and hypoxic radio-nuclides. This thesis has investigated 18FDG CT-PET guided target volume delineation methods and attempted to validate 64Cu-ATSM as a hypoxic radio-nuclide in patients with squamous cell carcinoma of the Head and Neck. Materials and Methods: Eight patients with locally advanced disease underwent 18FDG CT-PET imaging before and during curative radiotherapy or chemo-radiotherapy. Fixed (SUV cut off and percentage threshold of the SUVmax) and adaptive thresholds were investigated. The functional volumes automatically delineated by these methods and SUVmax were compared at each point, and between thresholds. Four patients with locally advanced disease, two to seven days prior to surgery, underwent 3D dynamic CT-PET imaging immediately after injection of 64Cu- ATSM. Two patients were also imaged 18 hours after injection, and two underwent a dynamic contrast-enhanced CT to evaluate intra-tumoural perfusion. All patients received pimonidazole before surgery. The pimonidazole, GLUT1, CAIX, and HIF1a immuno-histochemical hypoxic fractions were defined. Staining was correlated with the retention pattern of 64Cu-ATSM at 3 time points. Hypoxic target volumes were delineated according to tumour to muscle, blood and background ratios. Results: 18FDG primary and lymph node target volumes significantly reduced with radiation dose by the SUV cut off method and correlated with the reduction in the SUVmax within the volume. Volume reduction was also found between thresholds by the same delineation method. The volumes delineated by the other methods were not significantly reduced (except the lymph node functional volume when defined by the adaptive threshold). 64Cu-ATSM correlated with hypoxic immuno-histochemical staining but not with blood flow. Tumour ratios increased with time after injection, which influenced the delineated hypoxic target volume. Conclusion: Dose-escalated image-guided radiotherapy strategies using these CT-PET guided functional volumes have the potential to improve loco-regional control in patients with squamous cell carcinoma of the Head and Neck. CT-PET 18FDG volume delineation is intricately linked to the method and threshold of delineation and the timing of the imaging. 64Cu-ATSM is promising as a hypoxic radio-nuclide and warrants further investigation