Ala Lisok - Academia.edu (original) (raw)
Papers by Ala Lisok
Bioconjugate Chemistry, 2016
The programmed death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) pair is a major immun... more The programmed death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) pair is a major immune checkpoint pathway exploited by cancer cells to develop and maintain immune tolerance. With recent approvals of anti-PD-1 and anti-PD-L1 therapeutic antibodies, there is an urgent need for noninvasive detection methods to quantify dynamic PD-L1 expression in tumors and to evaluate the tumor response to immune modulation therapies. To address this need, we assessed [(64)Cu]atezolizumab for the detection of PD-L1 expression in tumors. Atezolizumab (MPDL3208A) is a humanized, human and mouse cross-reactive, therapeutic PD-L1 antibody that is being investigated in several cancers. Atezolizumab was conjugated with DOTAGA and radiolabeled with copper-64. The resulting [(64)Cu]atezolizumab was assessed for in vitro and in vivo specificity in multiple cell lines and tumors of variable PD-L1 expression. We performed PET-CT imaging, biodistribution, and blocking studies in NSG mice bearing tumors with constitutive PD-L1 expression (CHO-hPD-L1) and in controls (CHO). Specificity of [(64)Cu]atezolizumab was further confirmed in orthotopic tumor models of human breast cancer (MDAMB231 and SUM149) and in a syngeneic mouse mammary carcinoma model (4T1). We observed specific binding of [(64)Cu]atezolizumab to tumor cells in vitro, correlating with PD-L1 expression levels. Specific accumulation of [(64)Cu]atezolizumab was also observed in tumors with high PD-L1 expression (CHO-hPD-L1 and MDAMB231) compared to tumors with low PD-L1 expression (CHO, SUM149). Collectively, these studies demonstrate the feasibility of using [(64)Cu]atezolizumab for the detection of PD-L1 expression in different tumor types.
Oncotarget, Dec 1, 2011
We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of ... more We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of the prostate-specific membrane antigen (PSMA) for imaging and therapy of prostate cancer (PCa). Our system contains a lysine-based (µ-, e-) dialkyne residue for incorporating a PSMA binding Lys-Glu urea motif exploiting click chemistry and a second lysine residue for subsequent modification with an imaging or therapeutic moiety. The utility of the multivalent scaffold was examined by synthesizing bivalent compounds 2 and 3 and comparing them with the monovalent analog 1. Determination of inhibition constants (Ki) revealed that bivalent 2 (0.2 nM) and 3 (0.08 nM) are significantly more potent (~ 5 fold and ~ 11 fold, respectively) inhibitors of PSMA than monovalent 1 (0.9 nM). A single photon emission computed tomography (SPECT)-CT imaging study of [111In]3 demonstrated high and specific uptake in PSMA+ PC-3 PIP tumor until at least 48 h post-injection, with rapid clearance from non-target tissues, including kidney. A biodistribution study revealed that [111In]3 demonstrated 34.0 ± 7.5 percent injected dose per gram of tissue in PSMA+ tumor at 24 h post-injection and was capable of generating target-to-non-target ratios of ~ 379 in PSMA+ PC-3 PIP tumors vs. isogenic PSMA-negative PC3-flu tumors in vivo. The click chemistry approach affords a convenient strategy toward multivalent PSMA inhibitors of enhanced affinity and superior pharmacokinetics for imaging.
Bioconjugate chemistry, Jan 24, 2016
Prostate-specific membrane antigen (PSMA) is overexpressed in the epithelium of prostate cancer a... more Prostate-specific membrane antigen (PSMA) is overexpressed in the epithelium of prostate cancer and nonprostate solid tumor neovasculature. PSMA is increasingly utilized as a target for cancer imaging and therapy. Here, we report the synthesis and in vivo biodistribution of a low-molecular-weight PSMA-based imaging agent, 2-[3-(1-carboxy-5-{3-[1-(2-[(18)F]fluoroethyl)-1H-1,2,3-triazol-yl]propanamido}pentyl)ureido]pentanedioic acid ([(18)F]YC-88), containing an [(18)F]fluoroethyl triazole moiety. [(18)F]YC-88 was synthesized from 2-[(18)F]fluoroethyl azide and the corresponding alkyne precursor in two steps using either a one- or two-pot procedure. Biodistribution and positron emission tomography (PET) imaging were performed in immunocompromised mice using isogenic PSMA(+) PC3 PIP and PSMA(-) PC3 flu xenografts. YC-88 exhibited high affinity for PSMA as evidenced by a Ki value of 12.9 nM. The non-decay corrected radiochemical yields of [(18)F]YC-88 averaged 14 ± 1% (n = 5). Specific ...
Society of Nuclear Medicine Annual Meeting Abstracts, May 1, 2012
Molecular Pharmaceutics, Jan 15, 2015
The CXCR4 chemokine receptor is integral to several biological functions and plays a pivotal role... more The CXCR4 chemokine receptor is integral to several biological functions and plays a pivotal role in the pathophysiology of many diseases. As such, CXCR4 is an enticing target for the development of imaging and therapeutic agents. Here we report the evaluation of the POL3026 peptidomimetic template for the development of imaging agents that target CXCR4. Structural and conformational analyses of POL3026 and two of its conjugates, DOTA (POL-D) and PEG12-DOTA (POL-PD), by circular dichroism, two-dimensional NMR spectroscopy and molecular dynamics calculations are reported. In silico observations were experimentally verified with in vitro affinity assays and rationalized using crystal structure-based molecular modeling studies. [(111)In]-labeled DOTA conjugates were assessed in vivo for target specificity in CXCR4 expressing subcutaneous U87 tumors (U87-stb-CXCR4) through single photon emission computed tomography (SPECT/CT) imaging and biodistribution studies. In silico and in vitro studies show that POL3026 and its conjugates demonstrate similar interactions with different micelles that mimic cellular membrane and that the ε-NH2 of lysine(7) is critical to maintain high affinity to CXCR4. Modification of this group with DOTA or PEG12-DOTA led to the decrease of IC50 value from 0.087 nM for POL3026 to 0.47 nM and 1.42 nM for POL-D and POL-PD, respectively. In spite of the decreased affinity toward CXCR4, [(111)In]POL-D and [(111)In]POL-PD demonstrated high and significant uptake in U87-stb-CXCR4 tumors compared to the control U87 tumors at 90 min and 24 h post injection. Uptake in U87-stb-CXCR4 tumors could be blocked by unlabeled POL3026, indicating specificity of the agents in vivo. These results suggest POL3026 as a promising template to develop new imaging agents that target CXCR4.
Bioconjugate chemistry, Jan 14, 2016
68Ga-Labeled, low-molecular-weight imaging agents that target the prostate-specific membrane anti... more 68Ga-Labeled, low-molecular-weight imaging agents that target the prostate-specific membrane antigen (PSMA) are increasingly used clinically to detect prostate and other cancers with positron emission tomography (PET). The goal of this study was to compare the pharmacokinetics of three PSMA-targeted radiotracers: 68Ga-1, using DOTA-monoamide as the chelating agent; 68Ga-2, containing the macrocyclic chelating agent p-SCN-Bn-NOTA, and 68Ga-DKFZ-PSMA-11, currently in clinical trials, which uses the acyclic chelating agent, HBED-CC. The PSMA-targeting scaffold for all three agents utilized a similar Glu-Lys-urea-linker construct. Each radiotracer enabled visualization of PSMA+ PC3 PIP tumor, kidney, and urinary bladder as early as 15 min post-injection using small animal PET/computed tomography (PET/CT). 68Ga-2 demonstrated the fastest rate of clearance from all tissues in this series and displayed higher uptake in PSMA+ PC3 PIP tumor compared to 68Ga-1 at 1 h post-injection. There was...
Oncotarget, 2016
For physiologically important cancer therapeutic targets, use of non-invasive imaging for therape... more For physiologically important cancer therapeutic targets, use of non-invasive imaging for therapeutic guidance and monitoring may improve outcomes for treated patients. The CXC chemokine receptor 4 (CXCR4) is overexpressed in many cancers including non-small cell lung cancer (NSCLC) and triple negative breast cancer (TNBC). CXCR4 overexpression contributes to tumor growth, progression and metastasis. There are several CXCR4-targeted therapeutic agents currently in clinical trials. Since CXCR4 is also crucial for normal biological functions, its prolonged inhibition could lead to unwanted toxicities. While CXCR4-targeted imaging agents and inhibitors have been reported and evaluated independently, there are currently no studies demonstrating CXCR4-targeted imaging for therapeutic guidance.Monoclonal antibodies (mAbs) are commonly used for cancer therapy and imaging. Here, an 89Zr-labeled human CXCR4-mAb (89Zr-CXCR4-mAb) was evaluated for detection of CXCR4 expression with positron em...
Oncotarget, Jan 2, 2016
Antibodies targeting the PD-1/PD-L1 immune checkpoint lead to tumor regression and improved survi... more Antibodies targeting the PD-1/PD-L1 immune checkpoint lead to tumor regression and improved survival in several cancers. PD-L1 expression in tumors may be predictive of response to checkpoint blockade therapy. Because tissue samples might not always be available to guide therapy, we developed and evaluated a humanized antibody for non-invasive imaging of PD-L1 expression in tumors. Radiolabeled [111In]PD-L1-mAb and near-infrared dye conjugated NIR-PD-L1-mAb imaging agents were developed using the mouse and human cross-reactive PD-L1 antibody MPDL3280A. We tested specificity of [111In]PD-L1-mAb and NIR-PD-L1-mAb in cell lines and in tumors with varying levels of PD-L1 expression. We performed SPECT/CT imaging, biodistribution and blocking studies in NSG mice bearing tumors with constitutive PD-L1 expression (CHO-PDL1) and in controls (CHO). Results were confirmed in triple negative breast cancer (TNBC) (MDAMB231 and SUM149) and non-small cell lung cancer (NSCLC) (H2444 and H1155) xen...
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, Jan 23, 2016
The atypical chemokine receptor ACKR3 (formerly CXCR7), overexpressed in various cancers compared... more The atypical chemokine receptor ACKR3 (formerly CXCR7), overexpressed in various cancers compared to normal tissues, plays a pivotal role in adhesion, angiogenesis, tumorigenesis, metastasis and tumor cell survival. ACKR3 modulates the tumor microenvironment and regulates tumor growth. The therapeutic potential of ACKR3 has also been demonstrated in various murine models of human cancer. Literature findings underscore the importance of ACKR3 in disease progression and suggest it as an important diagnostic maker for non-invasive imaging of ACKR3 overexpressing malignancies. There are currently no reports on direct receptor-specific detection of ACKR3 expression. Here we report the evaluation of a radiolabeled ACKR3-targeted monoclonal antibody (ACKR3-mAb) for the non-invasive in vivo nuclear imaging of ACKR3 expression in human breast, lung and esophageal squamous cell carcinoma cancer xenografts. ACKR3 transcripts were extracted from Cancer Cell Line Encyclopedia (CCLE), The Cancer ...
Journal of medicinal chemistry, Jan 2, 2015
Radiolabeled urea-based low-molecular weight inhibitors of the prostate-specific membrane antigen... more Radiolabeled urea-based low-molecular weight inhibitors of the prostate-specific membrane antigen (PSMA) are under intense investigation as imaging and therapeutic agents for prostate and other cancers. In an effort to provide agents with less non-target organ uptake than the ureas, we synthesized four 18F-labeled inhibitors of PSMA based on carbamate scaffolds. 4-Bromo-2-[18F]fluorobenzoyl-lysine-oxy-pentanedioic acid (OPA) carbamate [18F]23 and 4-iodo-2-[18F]fluorobenzoyl-lysine OPA carbamate [18F]24 in particular exhibited high target-selective uptake in PSMA+ PC3 PIP tumor xenografts, with tumor-to-kidney ratios > 1 by 4 h post-injection, an important benchmark. Because of its high tumor uptake (90% injected dose per gram of tissue at 2 h post-injection) and high tumor-to-organ ratios, [18F]23 is promising for clinical translation. Prolonged tumor-specific uptake demonstrated by [18F]24, which did not reach equilibrium during the 4 h study period, suggests carbamates as alter...
Oncotarget, 2011
We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of ... more We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of the prostate-specific membrane antigen (PSMA) for imaging and therapy of prostate cancer (PCa). Our system contains a lysine-based (µ-, e-) dialkyne residue for incorporating a PSMA binding Lys-Glu urea motif exploiting click chemistry and a second lysine residue for subsequent modification with an imaging or therapeutic moiety. The utility of the multivalent scaffold was examined by synthesizing bivalent compounds 2 and 3 and comparing them with the monovalent analog 1. Determination of inhibition constants (Ki) revealed that bivalent 2 (0.2 nM) and 3 (0.08 nM) are significantly more potent (~ 5 fold and ~ 11 fold, respectively) inhibitors of PSMA than monovalent 1 (0.9 nM). A single photon emission computed tomography (SPECT)-CT imaging study of [111In]3 demonstrated high and specific uptake in PSMA+ PC-3 PIP tumor until at least 48 h post-injection, with rapid clearance from non-targe...
Oncogene, 2012
The role of estrogen receptor alpha (ER) in breast cancer development and as a primary clinical m... more The role of estrogen receptor alpha (ER) in breast cancer development and as a primary clinical marker for breast cancer prognosis is well documented. In this study, we identified the oncogenic protein TWIST1 (Twist), which is over-expressed in high-grade breast cancers, as a potential negative regulator of ER expression. Functional characterization of ER regulation by Twist was carried out using Twist low (MCF-7, T-47D) and Twist high (Hs 578T, MDA-MB-231, MCF-7/ Twist) expressing cell lines. All Twist high cell lines exhibited low ER transcript and protein levels. By chromatin immunoprecipitation and promoter assays, we demonstrated that Twist could directly bind to E-boxes in the ER promoter and significantly down-regulate ER promoter activity in vitro. Functionally, Twist over-expression caused estrogen independent proliferation of breast
Colloids and Surfaces B: Biointerfaces, 2011
Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been exte... more Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been extensively studied to improve effect and selectivity. Retinyl palmitate (RP) is widely used in pharmaceutical and cosmetics products to improve the skin elasticity. The aim of this study was the development, characterization and the in vivo effectiveness of RP in non-ionic LCS structures. LCS containing polyether functional siloxane as oil phase, silicon glycol copolymer as surfactant and water in the ratio 30:10:60, with and without RP were studied. The results of the polarized light microscopy, small-angle X-ray scattering and rheology analysis indicated the presence of typical LCS structures with lamellar arrangement. Regardless of the presence of RP, the rheological studies showed the pseudo plastic behavior of the systems. However, highest hysteresis area was verified when comparing the system in the presence and in the absence of RP. Stability study SAXS monitored, carried out up to 30 days in various storage temperature conditions (25 ± 2 • C, 37 ± 2 • C and 5 ± 2 • C) demonstrated the great structural stability of the LCS systems. The in vivo effectiveness analysis suggests that the RP-loaded LCS provided a significant reduction of the orbicular wrinkles in human volunteers (P = 0.048).
Bioconjugate Chemistry, 2014
Differential expression of surface proteins on normal vs malignant cells provides the rationale f... more Differential expression of surface proteins on normal vs malignant cells provides the rationale for the development of receptor-, antigen-, and transporter-based, cancer-selective imaging and therapeutic agents. However, tumors are heterogeneous, and do not always express what can be considered reliable, tumor-selective markers. That suggests development of more flexible targeting platforms that incorporate multiple moieties enabling concurrent targeting to a variety of putative markers. We report the synthesis, biochemical, in vitro, and preliminary in vivo evaluation of a new heterobivalent (HtBv) imaging agent targeting both the prostate-specific membrane antigen (PSMA) and integrin-αvβ3 surface markers, each of which can be overexpressed in certain tumor epithelium and/or neovasculature. The HtBv agent was functionalized with either 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or the commercially available IRDye800CW. DOTA-conjugated HtBv probe 9 bound to PSMA or αvβ3 with affinities similar to those of monovalent (Mnv) compounds designed to bind to their targets independently. In situ energy minimization experiments support a model describing the conformations adapted by 9 that enable it to bind both targets. IRDye800-conjugated HtBv probe 10 demonstrated target-specific binding to either PSMA or integrin-αvβ3 overexpressing xenografts. HtBv agents 9 and 10 may enable dual-targeted imaging of malignant cells and tissues in an effort to address heterogeneity that confounds many cancer-targeted imaging agents.
Thecancerstemcellparadigmpostulatesthatdysregulatedtissue-specificstemcellsorprogenitorcellsarepr... more Thecancerstemcellparadigmpostulatesthatdysregulatedtissue-specificstemcellsorprogenitorcellsareprecursors for cancer biogenesis. Consequently, identifying cancer stem cells is crucial to our understanding of cancer progres- sion and for the development of novel therapeutic agents. In this study, we demonstrate that the overexpression of Twist in breast cells can promote the generation of a breast cancer stem cell phenotype characterized by the high expression of CD44, little or no
Angewandte Chemie International Edition, 2015
Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functi... more Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate-specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR-based molecular imaging. We have synthesized three new high-affinity, low-molecular-weight Gd(III) -based PSMA-targeted contrast agents containing one to three Gd(III) chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA-based MR molecular imaging.
Biochemical and biophysical research communications, Jan 10, 2014
The receptor tyrosine kinase Axl is overexpressed in and leads to patient morbidity and mortality... more The receptor tyrosine kinase Axl is overexpressed in and leads to patient morbidity and mortality in a variety of cancers. Axl-Gas6 interactions are critical for tumor growth, angiogenesis and metastasis. The goal of this study was to investigate the feasibility of imaging graded levels of Axl expression in tumors using a radiolabeled antibody. We radiolabeled anti-human Axl (Axl mAb) and control IgG1 antibodies with (125)I with high specific radioactivity and radiochemical purity, resulting in an immunoreactive fraction suitable for in vivo studies. Radiolabeled antibodies were investigated in severe combined immunodeficient mice harboring subcutaneous CFPAC (Axl(high)) and Panc1 (Axl(low)) pancreatic cancer xenografts by ex vivo biodistribution and imaging. Based on these results, the specificity of [(125)I]Axl mAb was also validated in mice harboring orthotopic Panc1 or CFPAC tumors and in mice harboring subcutaneous 22Rv1 (Axl(low)) or DU145 (Axl(high)) prostate tumors by ex viv...
Neoplasia, 2009
The cancer stem cell paradigm postulates that dysregulated tissue-specific stem cells or progenit... more The cancer stem cell paradigm postulates that dysregulated tissue-specific stem cells or progenitor cells are precursors for cancer biogenesis. Consequently, identifying cancer stem cells is crucial to our understanding of cancer progression and for the development of novel therapeutic agents. In this study, we demonstrate that the overexpression of Twist in breast cells can promote the generation of a breast cancer stem cell phenotype characterized by the high expression of CD44, little or no expression of CD24, and increased aldehyde dehydrogenase 1 activity, independent of the epithelial-mesenchymal transition. In addition, Twist-overexpressing cells exhibit high efflux of Hoechst 33342 and Rhodamine 123 as a result of increased expression of ABCC1 (MRP1) transporters, a property of cancer stem cells. Moreover, we show that transient expression of Twist can induce the stem cell phenotype in multiple breast cell lines and that decreasing Twist expression by short hairpin RNA in Twist-overexpressing transgenic cell lines MCF-10A/Twist and MCF-7/Twist as well as in MDA-MB-231 partially reverses the stem cell molecular signature. Importantly, we show that inoculums of only 20 cells of the Twist-overexpressing CD44 + /CD24 -/low subpopulation are capable of forming tumors in the mammary fat pad of severe combined immunodeficient mice. Finally, with respect to mechanism, we provide data to indicate that Twist transcriptionally regulates CD24 expression in breast cancer cells. Taken together, our data demonstrate the direct involvement of Twist in generating a breast cancer stem cell phenotype through down-regulation of CD24 expression and independent of an epithelial-mesenchymal transition.
Bioconjugate Chemistry, 2016
The programmed death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) pair is a major immun... more The programmed death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) pair is a major immune checkpoint pathway exploited by cancer cells to develop and maintain immune tolerance. With recent approvals of anti-PD-1 and anti-PD-L1 therapeutic antibodies, there is an urgent need for noninvasive detection methods to quantify dynamic PD-L1 expression in tumors and to evaluate the tumor response to immune modulation therapies. To address this need, we assessed [(64)Cu]atezolizumab for the detection of PD-L1 expression in tumors. Atezolizumab (MPDL3208A) is a humanized, human and mouse cross-reactive, therapeutic PD-L1 antibody that is being investigated in several cancers. Atezolizumab was conjugated with DOTAGA and radiolabeled with copper-64. The resulting [(64)Cu]atezolizumab was assessed for in vitro and in vivo specificity in multiple cell lines and tumors of variable PD-L1 expression. We performed PET-CT imaging, biodistribution, and blocking studies in NSG mice bearing tumors with constitutive PD-L1 expression (CHO-hPD-L1) and in controls (CHO). Specificity of [(64)Cu]atezolizumab was further confirmed in orthotopic tumor models of human breast cancer (MDAMB231 and SUM149) and in a syngeneic mouse mammary carcinoma model (4T1). We observed specific binding of [(64)Cu]atezolizumab to tumor cells in vitro, correlating with PD-L1 expression levels. Specific accumulation of [(64)Cu]atezolizumab was also observed in tumors with high PD-L1 expression (CHO-hPD-L1 and MDAMB231) compared to tumors with low PD-L1 expression (CHO, SUM149). Collectively, these studies demonstrate the feasibility of using [(64)Cu]atezolizumab for the detection of PD-L1 expression in different tumor types.
Oncotarget, Dec 1, 2011
We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of ... more We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of the prostate-specific membrane antigen (PSMA) for imaging and therapy of prostate cancer (PCa). Our system contains a lysine-based (µ-, e-) dialkyne residue for incorporating a PSMA binding Lys-Glu urea motif exploiting click chemistry and a second lysine residue for subsequent modification with an imaging or therapeutic moiety. The utility of the multivalent scaffold was examined by synthesizing bivalent compounds 2 and 3 and comparing them with the monovalent analog 1. Determination of inhibition constants (Ki) revealed that bivalent 2 (0.2 nM) and 3 (0.08 nM) are significantly more potent (~ 5 fold and ~ 11 fold, respectively) inhibitors of PSMA than monovalent 1 (0.9 nM). A single photon emission computed tomography (SPECT)-CT imaging study of [111In]3 demonstrated high and specific uptake in PSMA+ PC-3 PIP tumor until at least 48 h post-injection, with rapid clearance from non-target tissues, including kidney. A biodistribution study revealed that [111In]3 demonstrated 34.0 ± 7.5 percent injected dose per gram of tissue in PSMA+ tumor at 24 h post-injection and was capable of generating target-to-non-target ratios of ~ 379 in PSMA+ PC-3 PIP tumors vs. isogenic PSMA-negative PC3-flu tumors in vivo. The click chemistry approach affords a convenient strategy toward multivalent PSMA inhibitors of enhanced affinity and superior pharmacokinetics for imaging.
Bioconjugate chemistry, Jan 24, 2016
Prostate-specific membrane antigen (PSMA) is overexpressed in the epithelium of prostate cancer a... more Prostate-specific membrane antigen (PSMA) is overexpressed in the epithelium of prostate cancer and nonprostate solid tumor neovasculature. PSMA is increasingly utilized as a target for cancer imaging and therapy. Here, we report the synthesis and in vivo biodistribution of a low-molecular-weight PSMA-based imaging agent, 2-[3-(1-carboxy-5-{3-[1-(2-[(18)F]fluoroethyl)-1H-1,2,3-triazol-yl]propanamido}pentyl)ureido]pentanedioic acid ([(18)F]YC-88), containing an [(18)F]fluoroethyl triazole moiety. [(18)F]YC-88 was synthesized from 2-[(18)F]fluoroethyl azide and the corresponding alkyne precursor in two steps using either a one- or two-pot procedure. Biodistribution and positron emission tomography (PET) imaging were performed in immunocompromised mice using isogenic PSMA(+) PC3 PIP and PSMA(-) PC3 flu xenografts. YC-88 exhibited high affinity for PSMA as evidenced by a Ki value of 12.9 nM. The non-decay corrected radiochemical yields of [(18)F]YC-88 averaged 14 ± 1% (n = 5). Specific ...
Society of Nuclear Medicine Annual Meeting Abstracts, May 1, 2012
Molecular Pharmaceutics, Jan 15, 2015
The CXCR4 chemokine receptor is integral to several biological functions and plays a pivotal role... more The CXCR4 chemokine receptor is integral to several biological functions and plays a pivotal role in the pathophysiology of many diseases. As such, CXCR4 is an enticing target for the development of imaging and therapeutic agents. Here we report the evaluation of the POL3026 peptidomimetic template for the development of imaging agents that target CXCR4. Structural and conformational analyses of POL3026 and two of its conjugates, DOTA (POL-D) and PEG12-DOTA (POL-PD), by circular dichroism, two-dimensional NMR spectroscopy and molecular dynamics calculations are reported. In silico observations were experimentally verified with in vitro affinity assays and rationalized using crystal structure-based molecular modeling studies. [(111)In]-labeled DOTA conjugates were assessed in vivo for target specificity in CXCR4 expressing subcutaneous U87 tumors (U87-stb-CXCR4) through single photon emission computed tomography (SPECT/CT) imaging and biodistribution studies. In silico and in vitro studies show that POL3026 and its conjugates demonstrate similar interactions with different micelles that mimic cellular membrane and that the ε-NH2 of lysine(7) is critical to maintain high affinity to CXCR4. Modification of this group with DOTA or PEG12-DOTA led to the decrease of IC50 value from 0.087 nM for POL3026 to 0.47 nM and 1.42 nM for POL-D and POL-PD, respectively. In spite of the decreased affinity toward CXCR4, [(111)In]POL-D and [(111)In]POL-PD demonstrated high and significant uptake in U87-stb-CXCR4 tumors compared to the control U87 tumors at 90 min and 24 h post injection. Uptake in U87-stb-CXCR4 tumors could be blocked by unlabeled POL3026, indicating specificity of the agents in vivo. These results suggest POL3026 as a promising template to develop new imaging agents that target CXCR4.
Bioconjugate chemistry, Jan 14, 2016
68Ga-Labeled, low-molecular-weight imaging agents that target the prostate-specific membrane anti... more 68Ga-Labeled, low-molecular-weight imaging agents that target the prostate-specific membrane antigen (PSMA) are increasingly used clinically to detect prostate and other cancers with positron emission tomography (PET). The goal of this study was to compare the pharmacokinetics of three PSMA-targeted radiotracers: 68Ga-1, using DOTA-monoamide as the chelating agent; 68Ga-2, containing the macrocyclic chelating agent p-SCN-Bn-NOTA, and 68Ga-DKFZ-PSMA-11, currently in clinical trials, which uses the acyclic chelating agent, HBED-CC. The PSMA-targeting scaffold for all three agents utilized a similar Glu-Lys-urea-linker construct. Each radiotracer enabled visualization of PSMA+ PC3 PIP tumor, kidney, and urinary bladder as early as 15 min post-injection using small animal PET/computed tomography (PET/CT). 68Ga-2 demonstrated the fastest rate of clearance from all tissues in this series and displayed higher uptake in PSMA+ PC3 PIP tumor compared to 68Ga-1 at 1 h post-injection. There was...
Oncotarget, 2016
For physiologically important cancer therapeutic targets, use of non-invasive imaging for therape... more For physiologically important cancer therapeutic targets, use of non-invasive imaging for therapeutic guidance and monitoring may improve outcomes for treated patients. The CXC chemokine receptor 4 (CXCR4) is overexpressed in many cancers including non-small cell lung cancer (NSCLC) and triple negative breast cancer (TNBC). CXCR4 overexpression contributes to tumor growth, progression and metastasis. There are several CXCR4-targeted therapeutic agents currently in clinical trials. Since CXCR4 is also crucial for normal biological functions, its prolonged inhibition could lead to unwanted toxicities. While CXCR4-targeted imaging agents and inhibitors have been reported and evaluated independently, there are currently no studies demonstrating CXCR4-targeted imaging for therapeutic guidance.Monoclonal antibodies (mAbs) are commonly used for cancer therapy and imaging. Here, an 89Zr-labeled human CXCR4-mAb (89Zr-CXCR4-mAb) was evaluated for detection of CXCR4 expression with positron em...
Oncotarget, Jan 2, 2016
Antibodies targeting the PD-1/PD-L1 immune checkpoint lead to tumor regression and improved survi... more Antibodies targeting the PD-1/PD-L1 immune checkpoint lead to tumor regression and improved survival in several cancers. PD-L1 expression in tumors may be predictive of response to checkpoint blockade therapy. Because tissue samples might not always be available to guide therapy, we developed and evaluated a humanized antibody for non-invasive imaging of PD-L1 expression in tumors. Radiolabeled [111In]PD-L1-mAb and near-infrared dye conjugated NIR-PD-L1-mAb imaging agents were developed using the mouse and human cross-reactive PD-L1 antibody MPDL3280A. We tested specificity of [111In]PD-L1-mAb and NIR-PD-L1-mAb in cell lines and in tumors with varying levels of PD-L1 expression. We performed SPECT/CT imaging, biodistribution and blocking studies in NSG mice bearing tumors with constitutive PD-L1 expression (CHO-PDL1) and in controls (CHO). Results were confirmed in triple negative breast cancer (TNBC) (MDAMB231 and SUM149) and non-small cell lung cancer (NSCLC) (H2444 and H1155) xen...
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, Jan 23, 2016
The atypical chemokine receptor ACKR3 (formerly CXCR7), overexpressed in various cancers compared... more The atypical chemokine receptor ACKR3 (formerly CXCR7), overexpressed in various cancers compared to normal tissues, plays a pivotal role in adhesion, angiogenesis, tumorigenesis, metastasis and tumor cell survival. ACKR3 modulates the tumor microenvironment and regulates tumor growth. The therapeutic potential of ACKR3 has also been demonstrated in various murine models of human cancer. Literature findings underscore the importance of ACKR3 in disease progression and suggest it as an important diagnostic maker for non-invasive imaging of ACKR3 overexpressing malignancies. There are currently no reports on direct receptor-specific detection of ACKR3 expression. Here we report the evaluation of a radiolabeled ACKR3-targeted monoclonal antibody (ACKR3-mAb) for the non-invasive in vivo nuclear imaging of ACKR3 expression in human breast, lung and esophageal squamous cell carcinoma cancer xenografts. ACKR3 transcripts were extracted from Cancer Cell Line Encyclopedia (CCLE), The Cancer ...
Journal of medicinal chemistry, Jan 2, 2015
Radiolabeled urea-based low-molecular weight inhibitors of the prostate-specific membrane antigen... more Radiolabeled urea-based low-molecular weight inhibitors of the prostate-specific membrane antigen (PSMA) are under intense investigation as imaging and therapeutic agents for prostate and other cancers. In an effort to provide agents with less non-target organ uptake than the ureas, we synthesized four 18F-labeled inhibitors of PSMA based on carbamate scaffolds. 4-Bromo-2-[18F]fluorobenzoyl-lysine-oxy-pentanedioic acid (OPA) carbamate [18F]23 and 4-iodo-2-[18F]fluorobenzoyl-lysine OPA carbamate [18F]24 in particular exhibited high target-selective uptake in PSMA+ PC3 PIP tumor xenografts, with tumor-to-kidney ratios > 1 by 4 h post-injection, an important benchmark. Because of its high tumor uptake (90% injected dose per gram of tissue at 2 h post-injection) and high tumor-to-organ ratios, [18F]23 is promising for clinical translation. Prolonged tumor-specific uptake demonstrated by [18F]24, which did not reach equilibrium during the 4 h study period, suggests carbamates as alter...
Oncotarget, 2011
We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of ... more We have developed a modular scaffold for preparing high-affinity, homo-multivalent inhibitors of the prostate-specific membrane antigen (PSMA) for imaging and therapy of prostate cancer (PCa). Our system contains a lysine-based (µ-, e-) dialkyne residue for incorporating a PSMA binding Lys-Glu urea motif exploiting click chemistry and a second lysine residue for subsequent modification with an imaging or therapeutic moiety. The utility of the multivalent scaffold was examined by synthesizing bivalent compounds 2 and 3 and comparing them with the monovalent analog 1. Determination of inhibition constants (Ki) revealed that bivalent 2 (0.2 nM) and 3 (0.08 nM) are significantly more potent (~ 5 fold and ~ 11 fold, respectively) inhibitors of PSMA than monovalent 1 (0.9 nM). A single photon emission computed tomography (SPECT)-CT imaging study of [111In]3 demonstrated high and specific uptake in PSMA+ PC-3 PIP tumor until at least 48 h post-injection, with rapid clearance from non-targe...
Oncogene, 2012
The role of estrogen receptor alpha (ER) in breast cancer development and as a primary clinical m... more The role of estrogen receptor alpha (ER) in breast cancer development and as a primary clinical marker for breast cancer prognosis is well documented. In this study, we identified the oncogenic protein TWIST1 (Twist), which is over-expressed in high-grade breast cancers, as a potential negative regulator of ER expression. Functional characterization of ER regulation by Twist was carried out using Twist low (MCF-7, T-47D) and Twist high (Hs 578T, MDA-MB-231, MCF-7/ Twist) expressing cell lines. All Twist high cell lines exhibited low ER transcript and protein levels. By chromatin immunoprecipitation and promoter assays, we demonstrated that Twist could directly bind to E-boxes in the ER promoter and significantly down-regulate ER promoter activity in vitro. Functionally, Twist over-expression caused estrogen independent proliferation of breast
Colloids and Surfaces B: Biointerfaces, 2011
Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been exte... more Carrier systems for lipophilic drugs, such as the liquid crystalline systems (LCS) have been extensively studied to improve effect and selectivity. Retinyl palmitate (RP) is widely used in pharmaceutical and cosmetics products to improve the skin elasticity. The aim of this study was the development, characterization and the in vivo effectiveness of RP in non-ionic LCS structures. LCS containing polyether functional siloxane as oil phase, silicon glycol copolymer as surfactant and water in the ratio 30:10:60, with and without RP were studied. The results of the polarized light microscopy, small-angle X-ray scattering and rheology analysis indicated the presence of typical LCS structures with lamellar arrangement. Regardless of the presence of RP, the rheological studies showed the pseudo plastic behavior of the systems. However, highest hysteresis area was verified when comparing the system in the presence and in the absence of RP. Stability study SAXS monitored, carried out up to 30 days in various storage temperature conditions (25 ± 2 • C, 37 ± 2 • C and 5 ± 2 • C) demonstrated the great structural stability of the LCS systems. The in vivo effectiveness analysis suggests that the RP-loaded LCS provided a significant reduction of the orbicular wrinkles in human volunteers (P = 0.048).
Bioconjugate Chemistry, 2014
Differential expression of surface proteins on normal vs malignant cells provides the rationale f... more Differential expression of surface proteins on normal vs malignant cells provides the rationale for the development of receptor-, antigen-, and transporter-based, cancer-selective imaging and therapeutic agents. However, tumors are heterogeneous, and do not always express what can be considered reliable, tumor-selective markers. That suggests development of more flexible targeting platforms that incorporate multiple moieties enabling concurrent targeting to a variety of putative markers. We report the synthesis, biochemical, in vitro, and preliminary in vivo evaluation of a new heterobivalent (HtBv) imaging agent targeting both the prostate-specific membrane antigen (PSMA) and integrin-αvβ3 surface markers, each of which can be overexpressed in certain tumor epithelium and/or neovasculature. The HtBv agent was functionalized with either 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or the commercially available IRDye800CW. DOTA-conjugated HtBv probe 9 bound to PSMA or αvβ3 with affinities similar to those of monovalent (Mnv) compounds designed to bind to their targets independently. In situ energy minimization experiments support a model describing the conformations adapted by 9 that enable it to bind both targets. IRDye800-conjugated HtBv probe 10 demonstrated target-specific binding to either PSMA or integrin-αvβ3 overexpressing xenografts. HtBv agents 9 and 10 may enable dual-targeted imaging of malignant cells and tissues in an effort to address heterogeneity that confounds many cancer-targeted imaging agents.
Thecancerstemcellparadigmpostulatesthatdysregulatedtissue-specificstemcellsorprogenitorcellsarepr... more Thecancerstemcellparadigmpostulatesthatdysregulatedtissue-specificstemcellsorprogenitorcellsareprecursors for cancer biogenesis. Consequently, identifying cancer stem cells is crucial to our understanding of cancer progres- sion and for the development of novel therapeutic agents. In this study, we demonstrate that the overexpression of Twist in breast cells can promote the generation of a breast cancer stem cell phenotype characterized by the high expression of CD44, little or no
Angewandte Chemie International Edition, 2015
Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functi... more Magnetic resonance (MR) imaging is advantageous because it concurrently provides anatomic, functional, and molecular information. MR molecular imaging can combine the high spatial resolution of this established clinical modality with molecular profiling in vivo. However, as a result of the intrinsically low sensitivity of MR imaging, high local concentrations of biological targets are required to generate discernable MR contrast. We hypothesize that the prostate-specific membrane antigen (PSMA), an attractive target for imaging and therapy of prostate cancer, could serve as a suitable biomarker for MR-based molecular imaging. We have synthesized three new high-affinity, low-molecular-weight Gd(III) -based PSMA-targeted contrast agents containing one to three Gd(III) chelates per molecule. We evaluated the relaxometric properties of these agents in solution, in prostate cancer cells, and in an in vivo experimental model to demonstrate the feasibility of PSMA-based MR molecular imaging.
Biochemical and biophysical research communications, Jan 10, 2014
The receptor tyrosine kinase Axl is overexpressed in and leads to patient morbidity and mortality... more The receptor tyrosine kinase Axl is overexpressed in and leads to patient morbidity and mortality in a variety of cancers. Axl-Gas6 interactions are critical for tumor growth, angiogenesis and metastasis. The goal of this study was to investigate the feasibility of imaging graded levels of Axl expression in tumors using a radiolabeled antibody. We radiolabeled anti-human Axl (Axl mAb) and control IgG1 antibodies with (125)I with high specific radioactivity and radiochemical purity, resulting in an immunoreactive fraction suitable for in vivo studies. Radiolabeled antibodies were investigated in severe combined immunodeficient mice harboring subcutaneous CFPAC (Axl(high)) and Panc1 (Axl(low)) pancreatic cancer xenografts by ex vivo biodistribution and imaging. Based on these results, the specificity of [(125)I]Axl mAb was also validated in mice harboring orthotopic Panc1 or CFPAC tumors and in mice harboring subcutaneous 22Rv1 (Axl(low)) or DU145 (Axl(high)) prostate tumors by ex viv...
Neoplasia, 2009
The cancer stem cell paradigm postulates that dysregulated tissue-specific stem cells or progenit... more The cancer stem cell paradigm postulates that dysregulated tissue-specific stem cells or progenitor cells are precursors for cancer biogenesis. Consequently, identifying cancer stem cells is crucial to our understanding of cancer progression and for the development of novel therapeutic agents. In this study, we demonstrate that the overexpression of Twist in breast cells can promote the generation of a breast cancer stem cell phenotype characterized by the high expression of CD44, little or no expression of CD24, and increased aldehyde dehydrogenase 1 activity, independent of the epithelial-mesenchymal transition. In addition, Twist-overexpressing cells exhibit high efflux of Hoechst 33342 and Rhodamine 123 as a result of increased expression of ABCC1 (MRP1) transporters, a property of cancer stem cells. Moreover, we show that transient expression of Twist can induce the stem cell phenotype in multiple breast cell lines and that decreasing Twist expression by short hairpin RNA in Twist-overexpressing transgenic cell lines MCF-10A/Twist and MCF-7/Twist as well as in MDA-MB-231 partially reverses the stem cell molecular signature. Importantly, we show that inoculums of only 20 cells of the Twist-overexpressing CD44 + /CD24 -/low subpopulation are capable of forming tumors in the mammary fat pad of severe combined immunodeficient mice. Finally, with respect to mechanism, we provide data to indicate that Twist transcriptionally regulates CD24 expression in breast cancer cells. Taken together, our data demonstrate the direct involvement of Twist in generating a breast cancer stem cell phenotype through down-regulation of CD24 expression and independent of an epithelial-mesenchymal transition.