Noninvasive near-infrared fluorescent protein-based imaging of tumor progression and metastases in deep organs and intraosseous tissues

Abstract

Abstract. Whole-body imaging of experimental tumor growth is more feasible within the near-infrared (NIR) optical window because of the highest transparency of mammalian tissues within this wavelength spectrum, mainly due to improved tissue penetration and lower autofluorescence. We took advantage from the recently cloned infrared fluorescent protein (iRFP) together with a human immunodeficiency virus (HIV)-based lentiviral vector to produce virally transduced tumor cells that permanently express this protein. We then noninvasively explored metastatic spread as well as primary tumor growth in deep organs and behind bone barriers. Intrabone tumor growth was investigated through intracranial and intratibial injections of glioblastoma and osteosarcoma cells, respectively, and metastasis was assessed by tail vein injection of melanoma cells. We found that the emitted fluorescence is captured as sharp images regardless of the organ or tissue considered. Furthermore, by overlaying fluorescence spots with the white light, it was possible to afford whole-body images yet never observed before. This approach allowed us to continuously monitor the growth and dissemination of tumor cells with a small number of animals, minimal animal handling, and without the need for any additive. This iRFP-based system provides high-resolution readouts of tumorigenesis that should greatly facilitate preclinical trials with anticancer therapeutic molecules. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Near-infrared fluorescent proteins engineered from bacterial phytochromes

“…Proteins of the iRFP series enabled visualization of small tumors at early stages, monitoring tumor growth and tracking metastases [13, 31]. In particular, iRFP713 protein performed well as a fluorescent marker in tumors located in deep organs, such as liver and prostate, and intrabone tumors, such as intracranial glioblastoma and intratibial osteosarcoma (Figure 2a) [32]. Using various imaging modalities (Figure 3) iRFP713 enabled imaging progression of inflammatory breast cancer and its metastases in lymph nodes [33] and detection metastatic targets of melanoma in whole body (Figure 3b) [32].…”

“…In particular, iRFP713 protein performed well as a fluorescent marker in tumors located in deep organs, such as liver and prostate, and intrabone tumors, such as intracranial glioblastoma and intratibial osteosarcoma (Figure 2a) [32]. Using various imaging modalities (Figure 3) iRFP713 enabled imaging progression of inflammatory breast cancer and its metastases in lymph nodes [33] and detection metastatic targets of melanoma in whole body (Figure 3b) [32]. iRFP713 also allowed to monitor tumor growth and metastases in an orthotopic prostate cancer model (Figure 3f) [31, 34].…”

In Vivo Tomographic Imaging of Deep-Seated Cancer Using Fluorescence Lifetime Contrast

“…As shown in Supplementary Figure 2, lifetime multiplexing enables the detection of approximately 1400 subcutaneous MTLn3-iRFP720 cells. This should be compared to the previously reported detection threshold of 5×10 4 subcutaneous iRFP cells using continuous wave fluorescence imaging (13). …”

“…A major challenge for the application of iRFPs to whole-body imaging of small and deep seated disease is their relatively low molecular brightness, which implies that tissue AF can still remain a significant contributor to the fluorescent signal. Although whole-animal imaging of iRFP-labeled tumors has been demonstrated (9,12,13), the tumors in these studies were either subcutaneous or consisted of several million cells in deep tissue. The ability to detect smaller metastases in deep organs of whole animals is of far more significance for pre-clinical oncology studies (14), since it will allow optimization of drug treatments to control the disease in its earliest stages.…”

Practical Issues with the Use of Stem Cells for Cancer Gene Therapy

“…While use of EGFP and DsRed may be useful in in vitro studies, they may not be as attractive in fluorescence imaging of deep tumors due to limited penetration of light, tissue absorption and scattering. Recently, Jiguet-Jiglaire et al (2014), reported the use of an infrared fluorescent protein with fluorescence characteristics laying within a near IR transparency of mammalian tissues 78 . This approach helped overcome issues related to fluorescent light tissue penetration, absorption and scattering in small animals such as mice facilitating more reliable preclinical studies; however, the application of this approach in larger animals or humans has not been investigated yet.…”