Cyclooxygenase-2 (Cox-2) is a biomarker for tumor progression and inflammatory diseases. It is known that normal tissues express minimal amounts of Cox-2 proteins while inflammatory and malignant tumor cells express high levels. Thus, inhibition of Cox-2 is a strategy in the treatment of tumor progression and inflammatory diseases. Recently, many different kinds of molecular imaging reagents for Cox-2 have been developed. Among them, an indomethacin-based Cox-2 probe, fluorocoxib, has been shown to bind to Cox-2 in vitro and in vivo. The binding specificity to Cox-2 was shown using cell culture and tumor xenograph models. In our present study, in order to optimize fluorocoxib imaging conditions, we utilized HCT116 and HT29 cells as low and high Cox-2 expressers, respectively. First, cultured cells were grown overnight on cover slips. Cells were then fixed with paraformaldehyde and incubated with fluorocoxib probe. Multispectral images were taken using a camera equipped with liquid crystal tunable filters. Spectral unmixing was applied to these images to enhance fluorocoxib signals. Our results indicate that HCT116 cells express fair amounts of Cox-2 protein. We also transplanted HCT116 and HT29 cells into the flank regions of nu/nu mice subcutaneously. After tumors grew to sufficient size (∼100 mm3) we injected fluorocoxib intravenously and monitored probe binding to the tumors. Whole animal in vivo imaging indicated that fluorocoxib binds to HT29 tumors after 3 hours. All the probes were eliminated from the animals by 24 hours. On the other hand, HCT116 tumors did not show strong binding of fluorocoxib as expected. However, HCT116 tumors did show some weak binding at the 3 and 6 hr time points. Once there was no longer any probe detected in vivo, we dissected the primary tumors from the HCT116 and HT29 implantations. Tissue sections were made with paraffin embedded tumors. After deparaffinization, tissue sections were incubated with fluorocoxib and fluorescent images were taken using multispectral imaging technology. Spectral unmixing data confirmed that HCT116 tumor sections showed fair amounts of Cox-2 probe expression. The amount of binding was also quantitated using a corresponding software package. Our results demonstrated that fluorescent biomarker probes can be imaged in vitro and in vivo non-invasively. Furthermore, we showed that the expression level can be quantitated using spectral unmixing imaging technology.

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 4292. doi:1538-7445.AM2012-4292