Arlin G. Cameron

Developing Fluorescent Hyaluronan Analogs for Hyaluronan Studies

Two kinds of fluorescent hyaluronan (HA) analogs, one serving as normal imaging agent and the other used as a biosensitive contrast agent, were developed for the investigation of HA uptake and degradation. Our approach of developing HA imaging agents depends on labeling HA with varying molar percentages of a near-infrared (NIR) dye. At low labeling ratios, the hyaluronan uptake can be directly imaged while at high labeling ratios, the fluorescent signal is quenched and signal generation occurs only after degradation. It is found that the conjugate containing 1%-2% NIR dye can be used as a normal optical imaging agent, while bioactivable imaging agents are formed at 6% to 17% dye loading. It was determined that the conjugation of dye to HA with different loading percentages does not impact HA biodegradation by hyaluronidase (Hyal). The feasibility of using these two NIR fluorescent hyaluronan analogs for HA investigation was evaluated in vivo with optical imaging. The data demonstrates that the 1% dye loaded fluorescent HA can be used to monitor the behavior of HA and its fragments, whereas bioactivatable HA imaging agent (17% dye in HA) is more suitable for detecting HA fragments.

Target-specific agents imaging ectopic and orthotopic human pancreatic cancer xenografts

Objectives: This study aimed to develop target-specific binding agents for in vitro and in vivo imaging of human pancreatic cancer. Methods: A monoclonal neutrophil gelatinase-associated lipocalin (NGAL)-specific antibody and a peptide specific for matrix metalloproteinase (MMP) were labeled with a near-infrared dye for in vitro and in vivo imaging studies. Fluorescence or confocal microscopy was used to determine antibody or peptide binding and internalization of agents into human AsPC-1, Panc-1, and MiaPaCa pancreatic cancer cell lines and in mice bearing ectopic or orthotopic pancreatic tumor transplants. Results: Both the NGAL-specific antibody and MMP peptide bound to pancreatic cancer cells with high specificity; most NGAL-specific antibody localized to the cytosol. In vivo imaging results demonstrated high signal intensity of both agents bound to the tumor. The average tumortr-to-background ratio of antibody and peptide was 1.29 and 2.86, respectively. Signal was also detectable in the liver, kidneys, and bladder. Conclusions: Both NGAL-specific antibody and MMP peptide bound to cancer cells, and the labeled antibody was internalized. These results demonstrate that both agents can be used to enhance detection of human pancreatic cancer xenografts. However, the biodistribution patterns of these agents might limit their use in research and clinical practice.

Multi-wavelength Optical Imaging of Human Tumour Xenografts

In vivo optical imaging methods have become a cornerstone of pre-clinical cancer research. Genetically modified cells with fluorescent or bioluminescent reporters allow researchers to non-invasively study tumour proliferation and biochemistry over time. Target-specific fluorescent probes may be used to reveal specific tumour properties such as growth patterns, neovasculature formation, and compartmental probe absorbance. Herein, we demonstrate the simultaneous optical imaging of these tumour properties in a human neuroblastoma model. We used luciferase-positive cancer cells, a neovasculature specific fluorescent probe, and a fluorescent tumour cell target-specific agent, in conjunction with X-ray/CT for anatomical localization. These experiments revealed a detailed map of the tumour progression and biological interactions with imaging agents within the tumour.

Abstract 4317: Developing near infrared (NIR) optical retinoid analogue for cancer imaging

Imaging technology plays an important role in early detection of cancers and improved prognoses. Among of the various imaging techniques used near infrared (NIR) optical imaging is an active and promising area for both in vitro and in vivo molecular imaging studies. However, NIR fluorophores normally only possess optical imaging properties without selectivity to diseased tissues. To address this problem, a targeting moiety can be introduced to help to deliver the imaging report to its target. It is know that retinoids, analogs of vitamin A, are assessed for multiple therapeutic uses. In practically, their potential chemopreventive and therapeutic roles in different kinds of cancers have attracted much attention. The cancer types include head and neck, lung, breast, esophagus, colon, kidney, prostate, bladder cancers and so on. Considering about important role of retinoids in cancer treatment developing retinoid derivatives as targeting imaging agents should be a useful strategy for noninvasive detection and characterization of solid tumors. Herein, we developed fluorescent retinoid derivatives for cancer imaging. Several different cancer cell lines and cancer xenograft models were used in this study. The data demonstrate that this new imaging agent can be used to imaging different kinds of cancers from cell level to whole body. Furthermore, these imaging agents have the potential to develop into special therapeutic agents that can be used for diagnosis, treatment and monitor of retinoid positive diseases. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4317.

Multi-modal and multi-wavelength imaging in xenografts bearing human tumor cells

Dynamic multi-wavelength fluorescence imaging was accomplished using a liquid crystal tunable filter (LCTF). Since several different emission wavelengths can be selected by tuning the LCTF, two wavelength dynamic fluorescence imaging was conducted in mice bearing human melanoma M21 and M21L after injection of a mixture of (i) RGD peptide conjugated with a near-infrared (NIR) dye that targeted integrin &agr;v&bgr;3 and (ii) non-specific dye, Cy5.5. Dynamic multi-wavelength imaging with LCTF can differentiate the uptake of the two different fluorescent contrast agents between tumor and normal tissue ROIs in the M21 and M21L xenograft models. Although the LCTF attenuated fluorescence signals by a factor of two when compared to holographic and bandpass filter sets used previously, Tumor to background ratio (TBR) from NIR fluorescence images with a bandpass and holographic filter were not statistically different from those acquired with the LCTF. Therefore, the benefit of spectral information as well as dynamic multi-wavelength may outweigh the impact of the lower transmission efficiencies, and could enable in vivo small animal imaging.