Tayyaba Hasan - Academia.edu (original) (raw)

Papers by Tayyaba Hasan

Photodiagnosis and photodynamic therapy, Jan 13, 2017

Sunlight can activate photodynamic therapy (PDT), and this is a proven strategy to reduce pain ca... more Sunlight can activate photodynamic therapy (PDT), and this is a proven strategy to reduce pain caused by the conventional PDT treatment, but assessment of this and other alternative low dose rate light sources, and their efficacy, has not been studied in an objective, controlled pre-clinical setting. This study used three objective assays to assess the efficacy of different PDT treatment regimens, using PpIX fluorescence as a photophysical measure, STAT3 cross-linking as a photochemical measure, and keratinocyte damage as a photobiological measure. Nude mouse skin was used along with in vivo measures of photosensitizer fluorescence, keratinocyte damage from pathology, and STAT3 cross-linking from Western blot analysis. Light sources compared included a low fluence rate red LED panel, compact fluorescent bulbs, halogen bulbs and direct sunlight, as compared to traditional PDT delivery with conventional and fractionated high fluence rate red LED light delivery. Of the three biomarkers...

Journal of biomechanical engineering, 2017

Elevated total tissue pressure (TTP) in pancreatic adenocarcinoma is often associated with stress... more Elevated total tissue pressure (TTP) in pancreatic adenocarcinoma is often associated with stress applied by cellular proliferation and hydrated hyaluronic acid osmotic swelling; however, the causal roles of collagen in total tissue pressure have yet to be clearly measured. This study illustrates one direct correlation between total tissue pressure and increased deposition of collagen within the tissue matrix. This observation comes from a new modification to a conventional piezoelectric pressure catheter, used to independently separate and quantify total tissue pressure, solid stress (SS), and interstitial fluid pressure (IFP) within the same tumor location, thereby clarifying the relationship between these parameters. Additionally, total tissue pressure shows a direct correlation with verteporfin uptake, demonstrating the impediment of systemically delivered molecules with increased tissue hypertension.

$Research paper thumbnail of Comparing desferrioxamine and light fractionation enhancement of ALA-PpIX photodynamic therapy in skin cancer$

British journal of cancer, Sep 30, 2016

Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) provides selective uptake and conversi... more Aminolevulinic acid (ALA)-based photodynamic therapy (PDT) provides selective uptake and conversion of ALA into protoporphyrin IX (PpIX) in actinic keratosis and squamous cell carcinoma, yet large response variations in effect are common between individuals. The aim of this study was to compare pre-treatment strategies that increase the therapeutic effect, including fractionated light delivery during PDT (fPDT) and use of iron chelator desferrioxamine (DFO), separately and combined. Optical measurements of fluorescence were used to quantify PpIX produced, and the total amount of PpIX photobleached as an implicit measure of the photodynamic dose. In addition, measurements of white light reflectance were used to quantify changes in vascular physiology throughout the PDT treatment. fPDT produced both a replenishment of PpIX and vascular re-oxygenation during a 2 h dark interval between the first and second PDT light fractions. The absolute photodynamic dose was increased 57% by fPDT, D...

Progress in Biomedical Optics and Imaging, 2011

A three-compartment kinetic model for the binding of a ligand to its receptor in tumor tissue has... more A three-compartment kinetic model for the binding of a ligand to its receptor in tumor tissue has been explained and the kinetic rates of the model are currently being investigated. In order to determine the plasma excretion rates of the dyes of interest, the fluorescence extinction coefficients must be determined. The fluorescence extinction coefficients of the IRDye700DX-carboxylate (IRDye700DX-C) and IRDye800CW-conjugated

Magnetic resonance quarterly, 1994

The use of intravenous gadolinium chelates in imaging of the abdomen is helpful in the detection ... more The use of intravenous gadolinium chelates in imaging of the abdomen is helpful in the detection and characterization of disease entities. It is well recognized that magnetic resonance (MR) imaging is more sensitive to the presence or absence of gadolinium chelates than computed tomography is to iodine. By exploiting this strength of gadolinium and MR sequences that reduce artifacts, the usefulness of abdominal MR examinations can be maximized. As a nonspecific extracellular contrast agent, the enhancement of gadolinium chelates reflect blood delivery (capillary phase imaging), capillary permeability (interstitial enhancement), and venous drainage (late interstitial/washout enhancement). In general terms, MR evaluation of abdominal organs is benefited by imaging in both capillary and interstitial phases of enhancement since these separate phases reflect different physiological aspects of disease processes. In this review, optimized investigation using intravenous gadolinium chelates...

ABSTRACT Tissues with high light absorption, such as melanomas, present a significant challenge t... more ABSTRACT Tissues with high light absorption, such as melanomas, present a significant challenge to fluorescence imaging approaches that seek to estimate molecular expression in vivo, since any fluorescence originating in the tissue will suffer substantial attenuation prior to detection. This can lead to sizable underestimations in estimated fluorescent tracer concentration in these tissues using conventional fluorescence imaging. In this study, a dual-tracer fluorescence imaging approach was employed to correct for severe tissue absorption by 1) using simultaneous injection and imaging of an untargeted tracer to normalize tissue absorption effects on the targeted tracer, and 2) using kinetic modeling that capitalizes on subtle differences in the dynamics of targeted and untargeted tracer uptake to quantify targeted molecule concentrations in the high absorbing tissue. Monte Carlo simulation and kinetic models demonstrated that the effect of optical properties on the approach could be eliminated by a pixel-by-pixel normalization of the targeted and untargeted tracer uptakes prior to 5 min post-tracer injection for fluorescence planar dynamic imaging.

ABSTRACT A non-invasive fluorescence imaging approach is presented to quantify metastatic tumor b... more ABSTRACT A non-invasive fluorescence imaging approach is presented to quantify metastatic tumor burden in lymph nodes. The approach employs dual-tracer kinetic modeling to estimate concentrations of cancer-specific molecular markers

As receptor-targeted therapeutics become increasingly used in clinical oncology, the ability to q... more As receptor-targeted therapeutics become increasingly used in clinical oncology, the ability to quantify protein expression and pharmacokinetics in vivo is imperative to ensure successful individualized treatment plans. Current standards for receptor analysis are performed on extracted tissues. These measurements are static and often physiologically irrelevant; therefore, only a partial picture of available receptors for drug targeting in vivo is provided. Until recently, in vivo measurements were limited by the inability to separate delivery, binding, and retention effects, but this can be circumvented by a dual-tracer approach for referencing the detected signal. We hypothesized that in vivo receptor concentration imaging (RCI) would be superior to ex vivo immunohistochemistry (IHC). Using multiple xenograft tumor models with varying EGFR expression, we determined the EGFR concentration in each model using a novel targeted agent (anti-EGFR affibody-IRDye800CW conjugate) along with a simultaneously delivered reference agent (control affibody-IRDye680RD conjugate). The RCI-calculated in vivo receptor concentration was strongly correlated with ex vivo pathologist-scored IHC and computer-quantified ex vivo immunofluorescence. In contrast, no correlation was observed with ex vivo Western blot analysis or in vitro flow-cytometry assays. Overall, our results argue that in vivo RCI provides a robust measure of receptor expression equivalent to ex vivo immunostaining, with implications for use in noninvasive monitoring of therapy or therapeutic guidance during surgery. Cancer Res; 74(24); 7465-74. Ó2014 AACR.

Molecular differences between cancerous and healthy tissue have become key targets for novel ther... more Molecular differences between cancerous and healthy tissue have become key targets for novel therapeutics specific to tumor receptors. However, cancer cell receptor expression can vary within and amongst different tumors, making strategies that can quantify receptor concentration in vivo critical for the progression of targeted therapies. Recently a dual-tracer imaging approach capable of providing quantitative measures of receptor concentration in vivo was developed. It relies on the simultaneous injection and imaging of receptortargeted tracer and an untargeted tracer (to account for non-specific uptake of the targeted tracer). Early implementations of this approach have been structured on existing "reference tissue" imaging methods that have not been optimized for or validated in dual-tracer imaging. Using simulations and mouse tumor model experimental data, the salient findings in this study were that all widely used reference tissue kinetic models can be used for dual-tracer imaging, with the linearized simplified reference tissue model offering a good balance of accuracy and computational efficiency. Moreover, an alternate version of the full two-compartment reference tissue model can be employed accurately by assuming that the K 1 s of the targeted and untargeted tracers are similar to avoid assuming an instantaneous equilibrium between bound and free states (made by all other models). quantify neurotransmitter receptor concentrations [12]-was also demonstrated to be critical when attempting to quantify receptor concentration in tumors [13]. To date, the dual-tracer receptor concentration imaging (RCI) approaches have rather indiscriminately employed one of the two early reference tissue models, Lammertsma and Hume's "simplified reference tissue model" [14] and Logan et al.'s "graphical analysis" approach [15], for no other reason than that they were easily adaptable to the dual-tracer framework. Even though many of the assumptions made in reference tissue models hold for dual-tracer RCI, it is not necessary that these models are optimal since additional assumptions can be made with dual-tracer RCI: e.g., that the delivery rates (K 1) of both tracers are the same if the chemical properties of the tracers are similar. Using both simulated and experimental data, the current study was carried out to identify the optimal data analysis workflow for translating targeted and untargeted tracer uptake curves in tumors to receptor concentration images, with particular emphasis on noise characteristics and computational cost of kinetic model data fitting. Theory Compartment models for dual-tracer kinetic analyses Reference tissue compartment models are ideally suited for dualtracer RCI since the setup of the dual-tracer compartment model (Figure 1) is nearly identical to that of the reference tissue model [14]. Both models recognize that non-specific uptake of a targeted tracer can significantly affect the relationship between tracer uptake and tracer binding or receptor concentration. The reference tissue model accounts for binding by employing the temporal uptake of the targeted tracer in a region devoid of targeted receptor (reference

Optical Tomography and Spectroscopy of Tissue X, 2013

The presence of metastatic tumor cells in tumor-draining lymph nodes is an important indicator fo... more The presence of metastatic tumor cells in tumor-draining lymph nodes is an important indicator for cancer staging and therapy. Current clinical approaches of assessing lymph node tumor burden require invasive surgery that can be associated with nerve damage and other complications. In this study, a dual-reporter fluorescence molecular imaging approach, previously validated for quantifying targeted reporter binding in various human tumor xenographs, was assessed as a means of quantifying tumor burden in metastatic disease in mice. The utility of the dual-reporter imaging approach to measure tumor burden in sentinel lymph nodes was investigated in a bioluminescent human breast cancer xenograph model in 18 female nude mice. Once the presence of tumor in the lymph node was confirmed by bioluminescent imaging, fluorescently labeled anti-EGFR antibody and an untargeted antibody (labeled with a different fluorophore) were injected intradermally, proximal to the lymph node, and the uptake of the two reporters was imaged simultaneously with a with a flat-panel fluorescent scanner. Preliminary results demonstrated a statistically significant correlation between the dual-reporter measured tumor burden and the bioluminescent measure of tumor burden.

Reporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications VI, 2014

ABSTRACT Simultaneous dynamic fluorescent imaging of a suitable untargeted tracer in conjunction ... more ABSTRACT Simultaneous dynamic fluorescent imaging of a suitable untargeted tracer in conjunction with any molecular targeted fluorescent agent has been shown to be a powerful approach for quantifying cancer-specific cell surface receptors in vivo in the presence of non-specific uptake and tracer delivery variability. The identification of a "suitable" untargeted tracer (i.e., one having equivalent plasma and tissue delivery pharmacokinetics to the targeted tracer) for every targeted tracer, however, may not always be feasible or could require extensive testing. This work presents a "deconvolution" approach capable of correcting for plasma and tissue-delivery pharmacokinetic differences between tracers by quantifying dynamic differences in targeted and untargeted tracer uptake in a receptor-free tissue (one devoid of targeted molecular species) and correcting uptake in all other tissues accordingly. This deconvolution correction approach is evaluated in theoretical models and explored in an in vivo mouse xenograft model of human glioma. In the animal experiments, epidermal growth factor receptor (EGFR: a receptor known to be overexpressed in the investigated glioma cell line) was targeted using a fluorescent tracer with very different plasma pharmacokinetics than a second untargeted fluorescent tracer. Without correcting for these differences, the dual-tracer approach yielded substantially higher estimations of EGFR concentration in all tissues than expected; however, deconvolution correction was able to produce estimates that matched ex vivo validation.

Nature Medicine, 2014

Lymph node biopsy (LNB) is employed in many cancer surgeries to identify metastatic disease and s... more Lymph node biopsy (LNB) is employed in many cancer surgeries to identify metastatic disease and stage the cancer, yet morbidity and diagnostic delays associated with LNB could be avoided if non-invasive imaging of nodal involvement was reliable. Molecular imaging has potential in this regard; however, variable delivery and nonspecific uptake of imaging tracers has made conventional approaches ineffective clinically. A method of correcting for non-specific uptake with injection of a second untargeted tracer is presented, allowing tumor burden in lymph nodes to be quantified. The approach was confirmed in an athymic mouse model of metastatic human breast cancer targeting epidermal growth factor receptor, a cell surface receptor overexpressed by many cancers. A significant correlation was observed between in vivo (dual-tracer) and ex vivo measures of tumor burden (r = 0.97, p < 0.01), with an ultimate sensitivity of approximately 200 cells (potentially more sensitive than conventional LNB).

Academic Radiology, 2015

It was hypothesized that perfusion computed tomography (CT), blood flow (BF), blood volume (BV), ... more It was hypothesized that perfusion computed tomography (CT), blood flow (BF), blood volume (BV), and vascular permeability surface area (PS) product parameters would be predictive of therapeutic anticancer agent uptake in pancreatic cancer, facilitating image-guided interpretation of human treatments. The hypothesis was tested in an orthotopic rabbit model of pancreatic cancer, by establishing the model, imaging with endoscopic ultrasound (EUS) and contrast CT, and spatially comparing the perfusion maps to the ex vivo uptake values of the injected photosensitizer, verteporfin. Nine New Zealand white rabbits underwent direct pancreas implantation of VX2 tumors, and CT perfusion or EUS was performed 10 days postimplantation. Verteporfin was injected during CT imaging, and the tissue was removed 1 hour postinjection for frozen tissue fluorescence scanning. Region-of-interest comparisons of CT data with ex vivo fluorescence and histopathologic staining were performed. Dynamic contrast-enhanced CT showed enhanced BF, BV, and PS in the tumor rim and decreased BF, BV, and PS in the tumor core. Significant correlations were found between ex vivo verteporfin concentration and each of BF, BV, and PS. The efficacy of verteporfin delivery in tumors is estimated by perfusion CT, providing a noninvasive method of mapping photosensitizer dose.

Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy XXIII, 2014

Proceedings of the National Academy of Sciences, 2013

Nanoparticle delivery into solid tumors is affected by vessel density, interstitial fluid pressur... more Nanoparticle delivery into solid tumors is affected by vessel density, interstitial fluid pressure (IFP) and collagen, as shown in this article by contrasting the in vivo macroscopic quantitative uptake of 40 nm fluorescent beads in three tumor types.The fluorescence uptake was quantified on individual animals by normalization with the transmitted light and then normalized to normal tissue uptake in each mouse. Mean data for uptake in individual tumor lines then showed expected trends with the largest uptake in the most vascularized tumor line. Tumor lines with increased collagen were also consistent with highest interstitial fluid pressure and correlated with lowest uptake of nanoparticles. The data is consistent with a delivery model indicating that while vascular permeability is maximized by neovascular growth, it is inhibited by collagen content and the resulting interstitial pressure. Imaging of these parameters in vivo can lead to better individual noninvasive methods to assess drug penetration in situ. In this manuscript the dependence of nanoparticle delivery is addressed from the standpoint of vascular factors (the more vascularized, the better delivery) and as a function of collagen density and interstitial pressure (the higher these are, the worse the delivery).

The quantification of tumor molecular expression in vivo could have a significant impact for info... more The quantification of tumor molecular expression in vivo could have a significant impact for informing and monitoring emerging targeted therapies in oncology. Molecular imaging of targeted tracers can be used to quantify receptor expression in the form of a binding potential (BP) if the arterial input curve or a surrogate of it is also measured. However, the assumptions of the most common approaches (reference tissue models) may not be valid for use in tumors. In this study, the validity of reference tissue models is investigated for use in tumors experimentally and in simulations. Three different tumor lines were grown subcutaneously in athymic mice and the mice were injected with a mixture of an epidermal growth factor receptor-targeted fluorescent tracer and an untargeted fluorescent tracer. A one-compartment plasma input model demonstrated that the transport kinetics of both tracers was significantly different between tumors and all potential reference tissues, and using the reference tissue model resulted in a theoretical underestimation in BP of 50% ± 37%. On the other hand, the targeted and untargeted tracers demonstrated similar transport kinetics, allowing a dual-tracer approach to be employed to accurately estimate BP (with a theoretical error of 0.23% ± 9.07%). These findings highlight the potential for using a dual-tracer approach to quantify receptor expression in tumors with abnormal hemodynamics, possibly to inform the choice or progress of molecular cancer therapies.

In this study, we demonstrate a method to quantify biomarker expression that uses an exogenous du... more In this study, we demonstrate a method to quantify biomarker expression that uses an exogenous dualreporter imaging approach to improve tumor signal detection. The uptake of two fluorophores, one nonspecific and one targeted to the epidermal growth factor receptor (EGFR), were imaged at 1 h in three types of xenograft tumors spanning a range of EGFR expression levels (n ¼ 6 in each group). Using this dual-reporter imaging methodology, tumor contrast-to-noise ratio was amplified by >6 times at 1 h postinjection and >2 times at 24 h. Furthermore, by as early as 20 min postinjection, the dual-reporter imaging signal in the tumor correlated significantly with a validated marker of receptor density (P < 0.05, r ¼ 0.93). Dual-reporter imaging can improve sensitivity and specificity over conventional fluorescence imaging in applications such as fluorescence-guided surgery and directly approximates the receptor status of the tumor, a measure that could be used to inform choices of biological therapies.

Purpose-Cellular receptor targeted imaging agents present the potential to target extracellular m... more Purpose-Cellular receptor targeted imaging agents present the potential to target extracellular molecular expression in cancerous lesions; however, the image contrast in vivo does not reflect the magnitude of overexpression expected from in vitro data. Here, the in vivo delivery and binding kinetics of epidermal growth factor receptor (EGFR) was determined for normal pancreas and AsPC-1 orthotopic pancreatic tumors known to overexpress EGFR. Procedures-EGFR in orthotopic xenograft AsPC-1 tumors was targeted with epidermal growth factor (EGF) conjugated with IRDye800CW. The transfer rate constants (k e, K 12 , k 21 , k 23 , and k 32) associated with a three-compartment model describing the vascular delivery, leakage rate and binding of targeted agents were determined experimentally. The plasma excretion rate, k e , was determined from extracted blood plasma samples. K 12 , k 21 , and k 32 were determined from ex vivo tissue washing studies at time points ≥24 h. The measured in vivo uptake of IRDye800CW-EGF and a non-targeted tracer dye, IRDye700DX-carboxylate, injected simultaneously was used to determined k 23. Results-The vascular exchange of IRDye800CW-EGF in the orthotopic tumor (K 12 and k 21) was higher than in the AsPC-1 tumor as compared to normal pancreas, suggesting that more targeted agent can be taken up in tumor tissue. However, the cellular associated (binding) rate constant (k 23) was slightly lower for AsPC-1 pancreatic tumor (4.1×10 −4 s −1) than the normal pancreas (5.5×10 −4 s −1), implying that less binding is occurring. Conclusions-Higher vascular delivery but low cellular association in the AsPC-1 tumor compared to the normal pancreas may be indicative of low receptor density due to low cellular content. This attribute of the AsPC-1 tumor may indicate one contributing cause of the difficulty in treating pancreatic tumors with cellular targeted agents.

Purpose-Receptor availability represents a key component of current cancer management. However, n... more Purpose-Receptor availability represents a key component of current cancer management. However, no approaches have been adopted to do this clinically, and the current standard of care is invasive tissue biopsy. A dual-reporter methodology capable of quantifying available receptor binding potential of tumors in vivo within a clinically relevant time scale is presented. Procedures-To test the methodology, a fluorescence imaging-based adaptation was validated against ex vivo and in vitro measures of epidermal growth factor receptor (EGFR) binding potential in four tumor lines in mice, each line expected to express a different level of EGFR. Results-A strong correlation was observed between in vivo and ex vivo measures of binding potential for all tumor lines (r=0.99, p<0.01, slope=1.80±0.48, and intercept=−0.58±0.84) and between in vivo and in vitro for the three lines expressing the least amount of EGFR (r=0.99, p<0.01, slope=0.64±0.32, and intercept=0.47±0.51). Conclusions-By providing a fast and robust measure of receptor density in tumors, the presented methodology has powerful implications for improving choices in cancer intervention, evaluation, and monitoring, and can be scaled to the clinic with an imaging modality like SPECT.