Purification method directly influences effectiveness of an epidermal growth factor-coupled targeting agent for noninvasive tumor detection in mice

Receptor targeting is an effective method of enhancing fluorescence signal in tumors for optical imaging. We previously used epidermal growth factor (EGF) conjugated to IRDye 800CW to detect and track orthotopic prostate tumors in mice. In this study, our goal was to identify a reliable assay for targeting agent integrity in vitro that correlated with signal strength in vivo. Binding of IRDye 800CW EGF to intact A431 human epidermoid carcinoma cells was quantified in a microplate assay. Specificity was confirmed by competition with unlabeled EGF or monoclonal antibody blocking. Biological activity of intact and damaged targeting agents relative to unlabeled EGF was determined by binding and stimulation of extracellular signal-regulated kinase (ERK) phosphorylation. Both assays indicated a reduction of up to 60% of the fluorescence intensity with damaged agents. Using a research prototype imaging system optimized for IRDye 800CW detection, we compared the efficacy of intact and damaged targeting agents for imaging subcutaneous tumors in mice. In live animal images and in sections of the excised tumors, damaged targeting agents consistently yielded diminished fluorescence signals corresponding to the reduction observed in microplate assays. This is the first study to directly correlate targeting agent signal strength in whole cell binding, In-Cell Western, and in vivo near-infrared imaging

Hyaluronidase Expression Induces Prostate Tumor Metastasis in an Orthotopic Mouse Model

Molecular mechanisms of prostate cancer progression are frequently studied in mice by orthotopic injection of aggressive cell lines, which yield primary tumors that spontaneously metastasize to lymph nodes. In this report, we characterized the human prostate carcinoma cell line 22Rv1 in an orthotopic system and evaluated the functional relevance of the hyaluronidase Hyal1, a correlate of invasive human prostate cancer, to progression in this model. To provide real-time insights into these processes, we first validated use of an epidermal growth factor-conjugated fluorophore to illuminate orthotopic prostate tumors and their metastases in whole animal imaging. Animals receiving intraprostatic injections were tracked throughout a 6-week period. Tumor sizes were correlated 92% with total fluorescence intensities of 22 prostate tumors. In contrast to the highly tumorigenic and metastatic PC3M-LN4 cells, the 22Rv1 line was orthotopically tumorigenic but not metastatic, despite larger tumor sizes. Lymph node metastasis was successfully imaged in animals with PC3M-LN4 tumors on endpoint dissection. Stable transfection of 22Rv1 cells with Hyal1 did not alter growth kinetics of primary orthotopic tumors, but all animals implanted with Hyal1 transfectants exhibited tumor-positive para-aortic lymph nodes. Hyal1 is implicated as an inducer of prostate cancer metastatic progression