Spying on cancer

Abstract

Genetically encoded imaging reporters introduced into cells and transgenic animals enable noninvasive, longitudinal studies of dynamic biological processes in vivo. The most common reporters include firefly luciferase (bioluminescence imaging), green fluorescence protein (fluorescence imaging), herpes simplex virus-1 thymidine kinase (positron emission tomography), and variants with enhanced spectral and kinetic properties. When cloned into promoter/enhancer sequences or engineered into fusion proteins, imaging reporters allow transcriptional regulation, signal transduction, protein-protein interactions, oncogenic transformation, cell trafficking, and targeted drug action to be spatiotemporally resolved in vivo. Spying on cancer with genetically encoded imaging reporters provides insight into cancer-specific molecular machinery within the context of the whole animal.

Veni, Vidi, Vici: In Vivo Molecular Imaging of Immune Response

“…Mice were then imaged after the indicated treatments. Note that bortezomib not only abrogated LPS-induced activation of IKK (degradation of IkBa-FLuc), but actually promoted reporter accumulation, consistent with inhibition of both ligand-induced degradation and basal turnover of IkBa (reprinted by permission from Macmillan Publishers Ltd: Nature Methods [Gross and Piwnica-Worms, 2005a]). transcriptional activity of the examined promoter and therefore reflect activity of the associated upstream signaling cascades.…”

“…are generally available to investigators at major research institutions. The advantages, limitations, technical challenges, and enhancements under investigation for each of the various imaging modalities are addressed in several in-depth reviews (Gross and Piwnica-Worms, 2005b;Negrin and Contag, 2006;Tsien, 2003) and are summarized in Table 1. Herein, we will briefly review examples of molecular imaging strategies, focusing on injectable probes and genetically encoded reporters in the context of immunological paradigms, with the intent to inspire future innovations to visualize and conquer open questions in immunology.…”

“…Over the last five years, several strategies have been developed for imaging PPI in vivo including (1) PPIdependent reporter gene transactivation or repression (two-hybrid systems; recruitment of signal transduction cascades), (2) energy transfer techniques such as Fö rster or bioluminescence resonance energy transfer (FRET or BRET, respectively), and (3) reporter complementation, achieved by fusing inactive reporter fragments to interacting proteins, which upon association bring the fragments in close proximity and restore reporter activity (Gross and Piwnica-Worms, 2005b). Recently, an optimized FLuc protein fragment complementation system was developed by screening incremental truncation libraries of N-and C-terminal fragments of FLuc (Luker et al, 2004).…”

Monitoring mmp-9 gene expression in stromal cells using a novel transgenic mouse model

“…Here, we used a well-characterized promoter sequence containing a 681-bp stretch of the 5 0 flanking region of the mouse mmp-9 gene. Our Tg mouse model is thus different at the molecular level from that of Mohan et al Our model is also complementary because luciferase reporter systems are ideal for continuous realtime measurement of bioluminescence signals emitted from firefly luciferase-based reporter system under the control of specific mammalian promoters using a noninvasive imaging modality and standard bioimaging equipment [35][36][37]. Our proMMP9-Luc Tg mouse model does have some limitations.…”

Image-Guided Nanosystems for Targeted Delivery in Cancer Therapy

“…Also, imaging the downstream markers or effector molecules that signal cell death or apoptosis can provide indicators of treatment response much earlier than physical changes start to appear, such as tumor shrinkage [31]. Thus, molecular imaging of cancers can afford a gamut of meaningful information that can be applied for mechanistic understanding of the disease [32] as wells as early detection [33], and for studying multiple events, such as non-invasive visualization of accumulation/localization of the nanoparticles in vivo , its biological fate, visualizing the progression/regression of the disease [25], and quantifying the effect of drug treatment in individual patients that usually vary on a case-by-case basis. Molecular imaging technology as applied to a cancer therapy is thus heralded to play a major role in the era of personalized medicine [34].…”