Noninvasive Molecular Imaging Sheds Light on the Synergy between 5-Fluorouracil and TRAIL/Apo2L for Cancer Therapy

Abstract

Purpose: In a previous report, a recombinant luciferase reporter, activated during apoptosis via caspase-3 cleavage, was developed for imaging of apoptosis using bioluminescence. The ability to noninvasively image apoptosis in vivo could dramatically benefit the preclinical development of therapeutics targeting the apoptotic pathway. In this study, we examined the use of 5-fluorouracil (5-FU) for sensitizing D54 tumors to tumor necrosis factor a^related apoptosis^inducing ligand (TRAIL) therapy by monitoring apoptotic activity in vivo using bioluminescence imaging. Experimental Design: Using our apoptosis imaging platform and diffusion magnetic resonance imaging (MRI), we monitored the antitumor effects of 5-FU,TRAIL, and 5-FU + TRAIL using D54 xenografts. Additionally, volumetric and histologic analyses were done for correlation with findings from bioluminescence imaging and diffusion MRI. Results: Bioluminescence imaging showed that therapy with TRAIL alone produced an initial 400% increase in apoptotic activity that rapidly diminished during the 10-day treatment period despite continued therapy. In contrast, concomitant 5-FU andTRAIL therapy elicited an apoptotic response that was sustained throughout the entire therapeutic course. Using diffusion MRI, an enhanced tumor response was detected when concomitant therapy was given versus TRAILalone therapy. Last, concomitant therapy resulted in a prolonged growth delay (f9 days) compared withTRAIL alone (f4 days). Conclusion: We showed that concomitant 5-FU and TRAIL therapy indeed enhanced apoptotic activity in vivo, which translated into greater tumor control. Moreover, this technique sheds light on the synergy of 5-FU and TRAIL as evidenced by differences in the temporal activation of caspase-3 resulting from the different therapeutic regimens.

The expression of TRAIL and its receptors in gastric cancer and the apoptotic effect of rh-TRAIL on SGC7901 cells

“…Pan et al (34) found combination of TRAIL-carrying adenoviral vector with cisplatin showed an apparent synergistic cytotoxicity in cancer cells, and at the same time significantly abolished the toxicity in normal cells by reducing the dosage. Concomitant 5-FU and TRAIL therapy enhanced apoptotic activity and reduced the requirement for 5-FU that ultimately results in minimizing risks for systemic side effects (35,36). Our results confirmed the previous results.…”

Noninvasive molecular imaging of apoptosis in vivo using a modified firefly luciferase substrate, Z-DEVD-aminoluciferin

“…In one example, two estrogen-regulatory domains were linked on both the amino-and carboxy-terminal end of luciferase with a DEVD cleavage site. 13,14 Similarly, a multimodality imaging reporter was also recently described to be composed of fluorescent, bioluminescent, and positron emission In vivo apoptosis imaging by Z-DEVD-aminoluciferin J Hickson et al tomography (PET) reporters, separated by DEVD linkers. 26 In both models, under apoptotic conditions, the reporter domains are liberated allowing for light production.…”

“…11,12 Several recent reports have described the development of fluorescent and/or bioluminescent reporter constructs that specifically allow monitoring of caspase activation in vivo. These molecular imaging studies have mainly focused on generating cells that express a modified reporter protein, commonly a fusion protein or a split luciferase protein complementation strategy [13][14][15] that takes advantage of the specificity of caspases to cleave exclusively after aspartic acid residues and, in particular, the DEVD (aspartic acid-glutamic acid-valine-aspartic acid) tetrapeptide sequence, which is optimal for apoptotic effector caspases-3 and -7. 16,17 In these models, light production is silenced unless the cell is undergoing apoptosis, at which time activated caspase liberates the reporter.…”

Noninvasive Bioluminescence Imaging in Small Animals

“…This reporter was then inserted in cancer cells and used as an early detector of induced apoptosis. This group has reported additional bioluminescence methods to detect apoptosis (Lee et al 2007;Rehemtulla et al 2004). Liu and colleagues (2005) have developed a luciferin substrate that was cleaved to an active form after induction of apoptosis.…”