Attribute Analytics Performance Metrics from the MAM Consortium Interlaboratory Study

The multi-attribute method (MAM) was conceived as a single assay to potentially replace multiple single-attribute assays that have long been used in process development and quality control (QC) for protein therapeutics. MAM is rooted in traditional peptide mapping methods; it leverages mass spectrometry (MS) detection for confident identification and quantitation of many types of protein attributes that may be targeted for monitoring. While MAM has been widely explored across the industry, it has yet to gain a strong foothold within QC laboratories as a replacement method for established orthogonal platforms. Members of the MAM consortium recently undertook an interlaboratory study to evaluate the industry-wide status of MAM. Here we present the results of this study as they pertain to the targeted attribute analytics component of MAM, including investigation into the sources of variability between laboratories and comparison of MAM data to orthogonal methods. These results are made available with an eye toward aiding the community in further optimizing the method to enable its more frequent use in the QC environment.

New Peak Detection Performance Metrics from the MAM Consortium Interlaboratory Study

The Multi-Attribute Method (MAM) Consortium was initially formed as a venue to harmonize best practices, share experiences, and generate innovative methodologies to facilitate widespread integration of the MAM platform, which is an emerging ultra-high-performance liquid chromatography-mass spectrometry application. Successful implementation of MAM as a purity-indicating assay requires new peak detection (NPD) of potential process- and/or product-related impurities. The NPD interlaboratory study described herein was carried out by the MAM Consortium to report on the industry-wide performance of NPD using predigested samples of the NISTmAb Reference Material 8671. Results from 28 participating laboratories show that the NPD parameters being utilized across the industry are representative of high-resolution MS performance capabilities. Certain elements of NPD, including common sources of variability in the number of new peaks detected, that are critical to the performance of the purity function of MAM were identified in this study and are reported here as a means to further refine the methodology and accelerate adoption into manufacturer-specific protein therapeutic product life cycles.

Improved protection of outdoor workers from solar ultraviolet radiation: position statement

The vast majority of non-melanoma skin cancer (NMSC) is attributable to excessive exposure to ultraviolet radiation (UVR). Outdoor workers are exposed to an UVR dose at least 2 to 3 times higher than indoor workers and often to daily UVR doses 5 times above internationally recommended limits. The risk of UVR workplace exposure is vastly neglected, and the evident future challenges presented in this statement are contrasted with the current situation regarding legal recognition, patient care and compensation. While prevention is crucial to reduce cancer risks for outdoor workers, it is as much of relevance to better protect them through legally binding rules and regulations. Specific actions are outlined in five recommendations based on a Call to Action (table 1). The role of health professionals, including dermatologists, in this context is crucial.

Cancer league actions against sunbed use for skin cancer prevention

The incidence of non-melanoma and melanoma skin cancer has been rising in Europe. Although the World Health Organization's International Agency for Research on Cancer has since 2009 classified sunbeds as a Group 1 carcinogen, sunbed use, especially by those under the age of 18, continues to be a concern. As the only platform for cancer leagues in Europe, the Association of European Cancer Leagues decided to explore interest and actions by its member leagues at the national level against sunbed use, to share experiences and to provide background information on possible future collective actions at the EU level.

Abstract LB-208: Open air fluorescence imaging of tumors using a new, hands-free translational imaging system

Intraoperative tumor resection currently relies on the ability of a surgeon to visually detect and/or palpate the tumor and tumor margins. Small tumor nodules can be missed or tumor margins may be inadequately removed, resulting in the need for secondary treatment. Intraoperative fluorescence imaging can help improve the initial resection and, therefore, both improve outcomes and reduce cost. Unconjugated fluorescent dyes have been previously used for this type of study to identify tumors in first-in-human studies. However, dyes conjugated to a targeting moiety have better specificity for the tumor itself and provide better guidance for the surgeon to locate the tumor and remove margins.

The new Solaris imaging system is an open air fluorescence imaging instrument designed specifically for intraoperative imaging in small to large animals. The system supports 4 different fluorescence channels to image common dyes (e.g. indocyanine green [ICG] and Fluorescein isothiocyanate [FITC]) and more unique near-infrared (NIR) fluorescent dyes. All of these can be imaged in ambient light to achieve sensitivities of 10 nM for single, long exposures and 10-100 nM for videos. The imaging head is attached to an adjustable arm so that it be can be positioned 75 cm above the object plane, far enough to be considered outside of the sterile field. The imaging head also has two cameras for simultaneous fluorescence and bright field (color) imaging; these images can be overlaid in the software. Single, long exposure images acquired from 2 different wavelengths can be overlaid to enable multiplexing and improve tumor identification; previously published studies have shown this to be useful for sentinel lymph node detection. For FITC, a custom liquid crystal tunable filter (LCTF) is included in the system in tandem with spectral unmixing software to separate tissue autofluorescence from fluorescence emitted by the dye.

Although this system is designed for larger animals, proof of concept intraoperative tumor resection has been performed in rodents. Subcutaneous tumors have been resected while imaging mice injected with either the targeted agent IntegriSense™ 680 or the activatable agent ProSense® 750. To investigate a more challenging model, tumor cell lines have also been implanted intrasplenically in rats. After injection with either the targeted agent BombesinRSense™ 680 or the activatable agent MMPSense® 750, deep tissue tumors can be identified intraoperatively and removed. Both the residual tumor bed (in vivo) and the resected tumors (ex vivo) can be imaged to confirm complete resection. In addition, although there are depth limitations due to the absorption and scattering of light in tissue, images acquired using a rat osteoarthritis model also provides insight into the ability to detect targeted fluorescence agents non-invasively. These results suggest that intraoperative resection of tumors detected with both targeted and activatable fluorescent agents is feasible using the new Solaris imaging system.

Citation Format: Jeffrey A. Meganck, Kristine Vasquez, Jeffrey Peterson, Chris Condron, Ali Behrooz, Josh Kempner, Alexandra de Lille, Yiyong Tan, Pete Harvey, Hongyan Gu, Paul Kennedy, Mathew Roxo, Ilias Faqir, Yan Zhang, Leo Mirkin, Peter Miller, Wael Yared. Open air fluorescence imaging of tumors using a new, hands-free translational imaging system. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-208. doi:10.1158/1538-7445.AM2015-LB-208

Abstract 4939: Detection and quantification of enzymatically active tissue prostate-specific antigen in vivo

Prostate-Specific Antigen (PSA) is a 237 amino acid, 33 kDa, extracellular serine protease expressed in prostate epithelial tissue. In the normal prostate, high concentrations of PSA are stored in the prostatic ductal network. However, cancer leads to the disruption of normal tissue architecture and subsequent leakage of PSA into the tissue interstitium and circulation. Enzymatically active PSA is only present in prostate tissue and at other sites of prostate cancer growth. In circulation, active PSA immediately forms complexes with the serum protease inhibitor alpha-1-antichymotrypsin (ACT), while the inactive forms remains “free”. Traditional assays relied on testing for the presence of total PSA (mostly inactive and complexed) and do not provide information regarding the amount of enzymatically active PSA, a more biologically relevant tumor biomarker. To fill this gap, we developed a novel near infrared (NIR) fluorescent agent, designed to detect active PSA with no detection of inactive or complexed PSA. This agent, PSA750 FAST, contains a PSA-cleavable peptide sequence labeled with NIR fluorophores (ex/em 750/770 nm) and coupled to a pharmacokinetic modifier designed to improve its plasma availability. In its native state, the agent is nearly completely optically quenched (> 95%); and only becomes fluorescent upon enzymatic cleavage with active PSA, yielding a 300-1800 fold increase in signal as compared to the signal obtained using inactive or complexed PSA. Proteolytic cleavage was also selective for PSA over a large panel of enzymes, including Kallikrein 1, Cathepsin B, MMP-9, MMP-12, MMP-13, uPA, chymotrypsin and thrombin. We hypothesized that the enzymatic activity of PSA could be non-invasively and quantitatively monitored in 3D using Fluorescence Molecular Tomography (FMT), a powerful near-infrared imaging modality that enables 3D quantitative determination of fluorochrome distribution in tissues of live small animals. LNCaP (PSA positive) and PC3 (PSA negative) cells were implanted in the chest area of male nude mice. Real time imaging was performed after systemic administration of PSA750 FAST when tumors reached the desired size. Our results demonstrated a significantly higher fluorescent signal in LNCaP tumors as compared the adjoining muscle (34.1 +/- 3.8 nM versus 7.2 +/- 0.6 nM, p=0.0043). Likewise, fluorescence concentration in tumors was significantly higher in LNCaP as compared to PC3 tumors (34.1 +/- 3.8 nM vs 17.14 +/- 3.48 nM, p=0.0191; 12.99 +/- 3.7 vs 2.8 +/- 0.8 pmoles, p=0.0233). This is the first report that demonstrates the feasibility of non-invasive, real-time, molecular imaging of active PSA in vivo in a relevant tumor model. These findings demonstrate the effectiveness of this agent in conjunction with optical imaging as a functional platform for molecular imaging in the field of prostate cancer.

Citation Format: Jeffrey D. Peterson, Guojie Ho, Jeffrey Morin, Jeannine Delaney, Wael Yared, Milind Rajopadhye, Sylvie C. Kossodo. Detection and quantification of enzymatically active tissue prostate-specific antigen in vivo. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4939. doi:10.1158/1538-7445.AM2014-4939

Abstract 4934: Imaging and quantification of bombesin receptor expression in vivo using a NIR-labeled bombesin peptide

Gastrin-releasing peptide (GRP) is one of the mammalian analogs of bombesin-like peptides that function as growth factors in normal and neoplastic tissues upon binding to a family of bombesin-binding G protein-coupled receptors. Bombesin receptors are overexpressed in a variety of cancers, particularly prostate, breast, and gastrointestinal stromal tumors, and as such have been used to develop radiolabeled imaging tracers. As a pre-clinical alternative to using radiolabeled ligands, we developed a novel near infrared (NIR) fluorescent agent, BombesinRSense 680 (BRS680), designed to target and quantify bombesin receptors in vivo. BRS680 was produced from a modified 7 amino-acid GRP analog peptide labeled with a NIR fluorophore (ex/em 660/680 nm) and a pharmacokinetic modifier designed to improve its plasma availability (plasma t1/2 = 1.5 hours). In vitro labeling of human colonic adenocarcinoma HT-29 cells, which express GRP receptors, and blocking the signal by addition of unlabeled native bombesin, demonstrated the specificity of the agent by both fluorescence microscopy and flow cytometry. In vivo receptor expression was quantified by fluorescence tomography after BRS680 (2 nmol/mouse) was injected intravenously into nude mice bearing HT-29 tumor xenografts. HT-29 tumors showed a high level of receptor expression with approximately 30 pmol (1.5% injected dose) of BRS680 quantified in the tumors at 24 hours, and lower fluorescence in other tissues except for pancreas, a tissue known for high receptor expression, and kidneys, indicating renal clearance. In contrast to the fast clearance from circulation, the tumor tissue half-life of BRS680 was shown to be approximately 42 hours. In vivo targeting specificity was confirmed by collecting tumor tissue from injected mice and co-localizing BRS680 fluorescent signal with an anti-GRP receptor antibody on frozen sections. More importantly, treatment of HT-29 tumor-bearing mice with a tumor growth-arresting chemotherapy regime decreased in vivo BRS680 signal. Six days after beginning treatment with 5-fluorouracil and oxaliplatin in mice with established tumors, BRS680 fluorescent signal was significantly decreased in treated mice as compared to control mice (21.55 + 4.89 versus 34.10 + 2.90 pmoles, p=0.043) paralleling the inhibition of tumor growth (74.25 + 7.65 versus 141 + 19.39 mm3, p=0.003). Interestingly, chemotherapy did not consistently affect the fluorescent signal associated with ProSense 750 FAST, an agent that is specifically activated by the cathepsin family of inflammatory proteases, co-injected in the same animals (6.99 +1.68 versus 10.91 + 1.73 pmoles, p=0.104). These studies demonstrate the utility of BRS680 in tracking in vivo expression of bombesin receptors and underscores its potential to serve as an in vivo real-time indicator of anti-tumor treatment efficacy.

Citation Format: Jeffrey D. Peterson, Nara Narayanan, Jeannine Delaney, Jeffrey Morin, Milind Rajopadhye, Wael Yared, Sylvie Kossodo. Imaging and quantification of bombesin receptor expression in vivo using a NIR-labeled bombesin peptide. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4934. doi:10.1158/1538-7445.AM2014-4934

Detection and quantification of enzymatically active prostate-specific antigen in vivo

Assays for blood levels of prostate-specific antigen (PSA), performed in prostate cancer detection, measure mostly inactive/complexed PSA and do not provide information regarding enzymatically active PSA, which is biologically more relevant. Thus, we designed and synthesized an enzymatically cleavable peptide sequence labeled with near-infrared (NIR) fluorophores (ex/em 740/770  nm) and coupled it to a pharmacokinetic modifier designed to improve its plasma kinetics. In its native state, the agent, PSA750 FAST™ (PSA750), is optically quenched (>95%) and only becomes fluorescent upon cleavage by active PSA, yielding a significant increase in signal. This activation is highly selective for PSA relative to a large panel of disease-relevant enzymes. Active PSA was detected in tumor frozen sections using PSA750 and this activity was abolished in the presence of the inhibitor, alpha-1 anti-chymotrypsin. In vivo imaging of tumor-bearing mice using fluorescence molecular tomography demonstrated a significantly higher fluorescent signal in PSA+ LNCaP tumors as compared to PSA- prostate cancer 3 tumors (13.0±3.7 versus 2.8±0.8  pmol, p=0.023). Ex vivo imaging of tumor sections confirms PSA750-derived NIR signal localization in nonvascular tissue. This is the first report that demonstrates the feasibility and effectiveness of noninvasive, real time, fluorescence molecular imaging of PSA enzymatic activity in prostate cancer.

In vivo imaging and quantification of carbonic anhydrase IX expression as an endogenous biomarker of tumor hypoxia

Carbonic anhydrase IX (CA IX) is a transmembrane protein that has been shown to be greatly upregulated under conditions of hypoxia in many tumor cell lines. Tumor hypoxia is associated with impaired efficacy of cancer therapies making CA IX a valuable target for preclinical and diagnostic imaging. We have developed a quantitative in vivo optical imaging method for detection of CA IX as a marker of tumor hypoxia based on a near-infrared (NIR) fluorescent derivative of the CA IX inhibitor acetazolamide (AZ). The agent (HS680) showed single digit nanomolar inhibition of CA IX as well as selectivity over other CA isoforms and demonstrated up to 25-fold upregulation of fluorescent CA IX signal in hypoxic versus normoxic cells, which could be blocked by 60%-70% with unlabeled AZ. CA IX negative cell lines (HCT-116 and MDA-MB-231), as well as a non-binding control agent on CA IX positive cells, showed low fluorescent signal under both conditions. In vivo FMT imaging showed tumor accumulation and excellent tumor definition from 6-24 hours. In vivo selectivity was confirmed by pretreatment of the mice with unlabeled AZ resulting in >65% signal inhibition. HS680 tumor signal was further upregulated >2X in tumors by maintaining tumor-bearing mice in a low oxygen (8%) atmosphere. Importantly, intravenously injected HS680 signal was co-localized specifically with both CA IX antibody and pimonidazole (Pimo), and was located away from non-hypoxic regions indicated by a Hoechst stain. Thus, we have established a spatial correlation of fluorescence signal obtained by non-invasive, tomographic imaging of HS680 with regions of hypoxia and CA IX expression. These results illustrate the potential of HS680 and combined with FMT imaging to non-invasively quantify CA IX expression as a hypoxia biomarker, crucial to the study of the underlying biology of hypoxic tumors and the development and monitoring of novel anti-cancer therapies.

A fluorogenic near-infrared imaging agent for quantifying plasma and local tissue renin activity in vivo and ex vivo

The renin-angiotensin system (RAS) is well studied for its regulation of blood pressure and fluid homeostasis, as well as for increased activity associated with a variety of diseases and conditions, including cardiovascular disease, diabetes, and kidney disease. The enzyme renin cleaves angiotensinogen to form angiotensin I (ANG I), which is further cleaved by angiotensin-converting enzyme to produce ANG II. Although ANG II is the main effector molecule of the RAS, renin is the rate-limiting enzyme, thus playing a pivotal role in regulating RAS activity in hypertension and organ injury processes. Our objective was to develop a near-infrared fluorescent (NIRF) renin-imaging agent for noninvasive in vivo detection of renin activity as a measure of tissue RAS and in vitro plasma renin activity. We synthesized a renin-activatable agent, ReninSense 680 FAST (ReninSense), using a NIRF-quenched substrate derived from angiotensinogen that is cleaved specifically by purified mouse and rat renin enzymes to generate a fluorescent signal. This agent was assessed in vitro, in vivo, and ex vivo to detect and quantify increases in plasma and kidney renin activity in sodium-sensitive inbred C57BL/6 mice maintained on a low dietary sodium and diuretic regimen. Noninvasive in vivo fluorescence molecular tomographic imaging of the ReninSense signal in the kidney detected increased renin activity in the kidneys of hyperreninemic C57BL/6 mice. The agent also effectively detected renin activity in ex vivo kidneys, kidney tissue sections, and plasma samples. This approach could provide a new tool for assessing disorders linked to altered tissue and plasma renin activity and to monitor the efficacy of therapeutic treatments.

Abstract 2444: Non-invasive FMT quantification of folate receptor expression in mouse tumor xenografts with a new near-infrared fluorescent folate agent

Folate receptors (FR) are overexpressed on the surface of many different human tumor cells, including ovarian, breast, cervical, renal, colorectal and nasopharyngeal cancer cells, with little expression in normal tissues. As such, folic acid has been successfully exploited as a cancer specific targeting moiety for the efficient delivery of chemotherapeutic agents, drug carriers, photosensitizers and diagnostic reporters. Critical to the success of such agents is the determination of the level of FR expression for a given tumor, since weak FR-expressing cancers will not respond well to folate-targeted therapies. There is therefore a need for specific and quantitative imaging agents and methods for the determination of FR expression in vivo. Optical imaging in the near-infrared (NIR) range allows efficient penetration of photons through living tissue and minimizes interference from tissue autofluorescence. Combined with quantitative fluorescence molecular tomography (FMT), NIR fluorescent agents have emerged as invaluable tools for quantitative, deep tissue imaging across a range of important areas of disease research including oncology. We have developed a new, near-infrared fluorescent folate targeted agent, VM3244, and used it to noninvasively quantify FR expression in vivo by FMT of mouse tumor xenografts. Two cell types, KB and HeLa with different degrees of FR expression were employed in the present study. In vitro, FR expression levels of each cell type were visualized with anti-FR antibody by microscopy, showing high FR expression in KB cells and lower expression in HeLa cells. The binding of VM3244 to FR was quantified by flow cytometry, confirming high and low FR expression in KB and HeLa cells, with good agreement between VM3244 and the antibody. Specificity of the agent was demonstrated by blocking of the signal by addition of an excess of unlabeled folic acid. In vivo quantification was performed by injection of 2 nmol of VM3244 into nude mice mice bearing KB or HeLa tumor xenografts and imaging by FMT at 4 to 24 h post injection. KB tumors showed a high level of FR expression with approximately 200 pmol (10% injected dose) quantified in the tumors, with little fluorescence in other tissues except the kidneys at 4 h post injection biodistribution study. Consistent with the in vitro profile, HeLa tumors had less tumor fluorescence, with about 75 pmol (3.8% injected dose) quantified in the tumors. Both tumor cell lines showed significant (∼80%) knockdown of signal by co-injection of the mice with unlabeled folic acid and ex vivo colocalization with FR antibody on tumor slices, confirming the in vivo specificity of the agent. Thus, we have demonstrated the ability of VM3244 to quantify FR expression both in vitro and in vivo and, combined with FMT, to noninvasively distinguish between high and lower FR expressing tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2444. doi:1538-7445.AM2012-2444

Abstract LB-511: In vivo imaging of tumor vasculature with a novel near infra-red lectin agent

Tumors induce significant blood vessel development in order to support their aggressive growth and progression, and the extensive and disordered nature of tumor vasculature impairs drug delivery and efficacy. Destroying the tumor vasculature and/or inhibiting neo-vascularization, alone or in combination with traditional chemotherapies, has become a well-accepted and proven cancer treatment strategy. A well-known tool for studying tumor angiogenesis and measuring microvessel density is tomato (Lycopersicon esculentum) lectin, a single polypeptide glycoprotein that readily binds to sugar-containing proteins present on the endothelium. Our objective was to develop a near infra-red (NIR) tomato lectin agent in order to non-invasively assess tumor vasculature in vivo. A NIR fluorophore, VivoTag 680 XL (ε=210,000 M/cm; abs/em max 665/688 nm), was conjugated to tomato lectin to produce an imaging agent, tLectin 680. The conjugation was carried out by addition of the fluorophore in a DMSO solution to lectin in aqueous sodium bicarbonate. Yields of greater than 95% were achieved, based on absorbance with an average loading of 2 dyes per lectin. In vitro, tLectin 680 preferentially labeled primary endothelial cells from human umbilical veins. Specificity of binding was confirmed by control experiments using free dye and competitive blockade with unlabeled excess tomato lectin. In vivo, we used tLectin 680, in combination with Fluorescence Molecular Tomography (FMT), for non-invasive imaging and quantification of tumor neo-vasculature in Lewis Lung Carcinoma tumors implanted in nude mice. FMT imaging quantified a statistically significant difference between the concentrations of localized tLectin 680 in tumors implanted in the flank of nude mice versus in control (non-tumor) contra-lateral flanks (50.96 +12 versus 2.32 +1 pmol), as early as 6 hours after intravenous delivery. Specific localization of the agent to the tumor vasculature was confirmed by fluorescence microscopy of frozen tumor sections and by comparison to FITC-labeled CD31. In addition vessel counts performed ex vivo in frozen sections of different tumor cell lines by fluorescence microscopy, showed a good correlation (R2= 0.99) between CD31 and tLectin 680 signal: Lewis Lung Carcinomas (27.7 vessels/sample tLectin vs. 32 vessels/sample CD-31), HT-29 (13.4 vessels/sample vs. 15.4 vessels/sample), and matrigel plugs (5.5 vessels/sample vs. 7 vessels/sample). In vivo tLectin 680 signal was also shown to correlate with ex vivo microscopy (R2= 0.90) in these tumors (Lewis Lung Carcinomas 177.6 + 15 nM, 27.7 vessel/sample, HT-29 118.1 + 6 nM, 13.4 vessel/sample), and matrigel plugs 73.6 + 9 nM, 5.5 vessel/sample). These results underscore the potential of tLectin 680 combined with FMT imaging in assessing vascularity in vivo and in real time, improving the early detection and monitoring of anti-angiogenic treatments in cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-511. doi:1538-7445.AM2012-LB-511

Abstract 3949: In vivo imaging of tumor hypoxia by a new near-infrared fluorescent carbonic anhydrase IX-targeted agent

Carbonic anhydrase IX (CA IX), a cell surface enzyme involved in tumor cell acidification, is induced during tumor hypoxia (lack of oxygen) in many different types of tumors. CA IX expression is correlated to tumor cell proliferation and metastasis, poor prognosis, and resistance to therapeutic intervention, making CA IX an important biomarker in the study of hypoxia, tumor cell proliferation, and therapy. Therefore, determination of CAIX expression and identification of hypoxic tumors in vivo are critical for cancer research and treatments. We have designed and synthesized a near-infrared (NIR) fluorescent agent (VM3219) for in vivo detection and quantification of a cell surface biomarker of hypoxia, CA IX based on a well-known CA IX inhibitor, acetazolamide. VM3219 was characterized extensively in HeLa cells and in mouse HeLa tumor xenografts. Preliminary chemical and biochemical characterization of VM3219 showed excellent CA IX selectivity and affinity. In vitro, VM3219 detected 4-7-fold up-regulation of CA IX in live hypoxic HeLa cells as visualized by fluorescence microscopy and quantified by flow cytometry. VM3219 fluorescence signals were blocked by 80% when cells were pre-incubated with unlabeled acetazolamide. Fluorescent signal of VM3219 was low in normoxic HeLa cells and was comparable to the signal that were detected by using a non-binding control agent (VM3182) incubated with normoxic or hypoxic cells. In vivo imaging by fluorescence molecular tomography (FMTTM) showed that approximately 5% of the injected dose (2 nmol VM3219) was retained in the tumor tissues after 24 h (100 -120 pmol), 10-20-fold more than measured with a non-binding control agent. Tumor fluorescence was blocked >65% by prophylactic acetazolamide treatment. Maintenance of tumor-bearing mice on low oxygen (8%), as compared to normally housed tumor bearing mice (20% oxygen), induced a >2X (∼250 pmol) increase in VM3219 tumor fluorescence signal suggesting that CAIX expression was up-regulated within tumors by low oxygen. In tissue sections, VM3219 signal was shown to be specifically co-localized in the tumor hypoxic regions with CA IX antibody and Hypoxyprobe (pimonidazole), and the signal was away from non-hypoxic regions as determined by Hoechst stain. In conclusion, VM3219 is a new non-invasive tumor hypoxia imaging agent that offers a tool for specific imaging of a biologically important hypoxia biomarker, CA IX.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3949. doi:1538-7445.AM2012-3949

Abstract 2448: Development of a red fluorescent labeled agent for assessing HER2 expression in vitro and in vivo

Upregulation of tumor HER2 occurs in approximately 25% women with breast cancer and is often associated with poor prognosis. We developed a red fluorescent imaging agent to non-invasively image and quantify tumor-associated HER2 expression in vivo. A red fluorescent dye (VivoTag 645; α=210,000 μ/cm; abs/em max 643/660 nm) was used to label trastuzumab, which is currently used to treat breast and stomach cancer. The red-labeled trastuzumab (VM4003) preferentially labeled HER2+ SKOV-3 human ovarian adenocarcinoma cells over HER2− human colorectal adenocarcinoma Colo-205 cells (10 fold), and the specificity of binding was confirmed by control experiments using free dye, labeled non-specific IgG, and competitive blockade with unlabeled excess trastuzumab. Fluorescence microscopy confirmed the expected membrane localization of fluorescence. In vivo and ex vivo imaging by fluorescence molecular tomography (FMT), showed significantly higher signal within the tumors, peaking at 6-72 hours following intravenous injection of 2 mg/kg VM4003, decreasing thereafter with a tissue half-life of 3 days. In vivo quantification of tumor signal in nude mice showed significantly higher tumor signal in HER2+ than in HER2− tumors (14.36 + 4 versus 2.39+ 0.74 pmol, at 6h imaging time, p=0.007; 18.77 + 4.45 versus 3.50+ 0.98 pmol, at 24h, p=0.001). Specificity of targeting was confirmed by competition with excess intravenous unlabeled trastuzumab, which achieved 70% signal inhibition in the tumors (tumor signal 16.12 + 3.03 versus 4.72 + 1.96 pmol, p=0.022 at 24h). Tumor volumes, as determined by direct measurements of tumor size, were comparable between both groups of mice (p=0.193). Fluorescence microscopy of ex vivo frozen tissue sections confirmed tumor fluorescence and signal localization associated to cell membranes and cytoplasm. In summary, red fluorescent-labeled trastuzumab selectively targets αER2, allowing both imaging in vitro and the non-invasive real-time tomographic imaging and quantification in vivo of HER-2 expression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2448. doi:1538-7445.AM2012-2448

Compensation of optical heterogeneity-induced artifacts in fluorescence molecular tomography: theory and in vivo validation

We present a method for reduction of image artifacts induced by the optical heterogeneities of tissue in fluorescence molecular tomography (FMT) through identification and compensation of image regions that evidence propagation of emission light through thin or low-absorption tunnels in tissue. The light tunneled as such contributes to the emission image as spurious components that might substantially overwhelm the desirable fluorescence emanating from the targeted lesions. The proposed method makes use of the strong spatial correlation between the emission and excitation images to estimate the tunneled components and yield a residual image that mainly consists of the signal due to the desirable fluorescence. This residual image is further refined using a coincidence mask constructed for each excitation-emission image pair. The coincidence mask is essentially a map of the "hot spots" that occur in both excitation and emission images, as such areas are often associated with tunneled emission. In vivo studies are performed on a human colon adenocarcinoma xenograft tumor model with subcutaneous tumors and a murine breast adenocarcinoma model with aggressive tumor cell metastasis and growth in the lungs. Results demonstrate significant improvements in the reconstructions achieved by the proposed method.

Fluorescence molecular tomography enables in vivo visualization and quantification of nonunion fracture repair induced by genetically engineered mesenchymal stem cells

Fluorescence molecular tomography (FMT) is a novel tomographic near-infrared (NIR) imaging modality that enables 3D quantitative determination of fluorochrome distribution in tissues of live small animals at any depth. This study demonstrates a noninvasive, quantitative method of monitoring engineered bone remodeling via FMT. Murine mesenchymal stem cells overexpressing the osteogenic gene BMP2 (mMSCs-BMP2) were implanted into the thigh muscle and into a radial nonunion bone defect model in C3H/HeN mice. Real-time imaging of bone formation was performed following systemic administration of the fluorescent bisphosphonate imaging agent OsteoSense, an hydroxyapatite-directed bone-imaging probe. The mice underwent imaging on days 7, 14, and 21 postimplantation. New bone formation at the implantation sites was quantified using micro-computed tomography (micro-CT) imaging. A higher fluorescent signal occurred at the site of the mMSC-BMP2 implants than that found in controls. Micro-CT imaging revealed a mass of mature bone formed in the implantation sites on day 21, a finding also confirmed by histology. These findings highlight the effectiveness of FMT as a functional platform for molecular imaging in the field of bone regeneration and tissue engineering.