Browsing by Subject "Optical Imaging"
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Item Comparison of Bioluminescence and Fluorescence Imaging as Tools for Evaluating Growth of MCF7 and 4T1 Mammary Tumors(2017-01-17) Lin, Elisa B.; Winters, Alex; Gerberich, Jeni; Campbell, Trey; Liu, Li; O'Kelly, Devin; Mason, Ralph P.INTRODUCTION: Tumor growth can be assessed by a variety of small animal imaging modalities which are cheap, easy, and efficient. In particular, bioluminescence imaging (BLI) and fluorescence imaging (FLI) have received attention for their ability to measure tumor growth and response to treatment. Both imaging modalities are accurate and well established, however, each method has its own unique advantages and limitations. This study compared the use of BLI and FLI to characterize and monitor growth of mammary 4T1-luc and MCF7-luc-GFP-mCherry tumors in nude mice. Strong correlations were established between BLI, FLI, and tumor volume, providing evidence that each method could be used to validate the other and reduce overall error. METHODS: BLI and FLI image sequences were performed with the IVIS(r) Spectrum. BLI was used for 4T1 (n = 8) and MCF7 (n = 6) tumors. FLI was only used for MCF7 tumors. Tumor volume was measured with calipers. RESULTS: Evaluating the area under each BLI and FLI curve (the AUC method) proved to be more accurate than only evaluating at one time point or wavelength. For both BLI and FLI, the AUC method greatly simplified the imaging workflow and removed the need for perfect temporal accuracy, since all times and wavelengths were considered. BLI and FLI both showed strong correlation with tumor volume (R2 = 0.91 and 0.87, respectively). The BLI and FLI signals were also correlated (R2 = 0.79). Experimental difficulties like tumor scarring and a mid-experiment C. bovis infection compromised data quality. DISCUSSION: The strong correlations between each measurement are very reassuring. Each offers specific benefits, e.g., BLI and FLI allow detection of sub-palpable volumes and additional metastases in some cases. BLI offers particularly strong contrast to noise, but requires the administration of luciferin substrate. FLI signal is subject to background auto fluorescence; this became a particular problem when the C. bovis infection occurred. Caliper measurements are simple for subcutaneous tumors, but the optical imaging can also reveal deeper tumors. The investigations to date largely confirm growth characteristics and the utility of available imaging methods matching the extant literature. The correlations had not been examined for 4T1-luc at UTSW previously. Furthermore, these methods provide a foundation for my forthcoming medical school research activity. Notably, future plans include continued investigation of metastases and utilizing Multispectral Optoacoustic Tomography (MSOT) for integrated hypoxia studies.Item Folate Receptor Beta Targeting for In Vivo Optical Imaging of Head and Neck Squamous Cell Carcinoma(2013-01-22) Sun, Joel; Thibodeaux, Joel; Huang, Gang; Wang, Yiguang; Gao, Jinming; Low, Philip S.; Sumer, Baran D.OBJECTIVE: The folate receptor (FR) is a high-affinity folic acid binding endocytic receptor uncommonly expressed in normal tissues. The α isoform (FR-α) is overexpressed in a variety of epithelial neoplastic cells. In contrast, functional expression of the β isoform (FR-β) is limited to activated macrophages. Importantly, in many malignancies FR serves as a target for the delivery of tumor specific drugs and imaging markers. Folic acid conjugated fluorescent dyes have been used to guide tumor resection in mouse models and humans. However, their potential utility in head and neck squamous cell carcinoma (HNSCC) is unclear due an incomplete characterization of FR expression in such tumors. We hypothesized that tumor infiltrating macrophages expressing FR-β could allow fluorescent visualization of HNSCC tumors using folate conjugated dyes even when FR expression in cancer cells is low. SUBJECTS AND METHODS: Immunohistochemistry was performed on a tissue microarray (TMA) containing primary tumor tissue and matched tumor free surgical margins from 22 patients who underwent HNSCC resection. Primary tumor sites included the oral tongue, base of tongue, tonsil, supraglottic larynx, glottic larynx and hypopharynx. We evaluated the expression of FR-α, FR-β, TGF-β, CD68 and arginase-1. To examine the use of folate targeting for image guided surgery, orthotopic xenograft HNSCC tumor models were generated from nude mice. The mice received 0.8 mg/kg intravenous injections of fluorescein isothiocyanate conjugated folate (Folate-FITC) and were imaged for fluorescent emission under 495nm light two hours later. RESULTS: No FR-α expression was observed in any TMA tumor specimen. All tumor samples demonstrated positive FR-β expression. Cellular morphology and CD68 expression identified the FR-β expressing cells as tumor infiltrating macrophages. No association was observed between FR-β staining and either TGF-β or arginase-1 staining. In tumor xenograft mouse models, tumors showed strong fluorescence in vivo after folate-FITC injection. Normal salivary glands and surrounding neck muscles did not demonstrate significant fluorescence. Histologic examination of the xenografts revealed that fluorescence within the tumors was confined to areas of inflammatory cell infiltration, consistent with our TMA data. Conclusion: HNSCC tumors contain a significant population of FR-β expressing macrophages. In contrast to many other carcinomas, the HNSCC tumor cells in our TMA did not express FR-α. By targeting tumor infiltrating macrophages, the folate linked delivery of fluorescent dyes can facilitate image guided HNSCC resection even when the tumor cells themselves do not express FR.