How reproducible is bioluminescent imaging of tumor cell growth? Single time point versus the dynamic measurement approach

To determine the most robust and reproducible parameters for noninvasively estimating tumor cell burden in a murine model, we used real-time in vivo bioluminescent imaging to assess the growth kinetics and dissemination of luciferase-transfected Raji B-cell lymphoma. Bioluminescent signals were acquired every minute for 40 minutes after luciferin injection every other day post-tumor injection. The total 40-minute area under the curve (AUC) of photon intensity (photons/second) was calculated and compared with simplified fixed time point observations (every 5 minutes from 5 to 40 minutes after substrate injection). There was substantial variability in the shape of the time signal intensity curves at different stages of tumor growth in both the intravenous and subcutaneous models. The coefficient of variance in the AUC was 0.27 (intravenous) and 0.36 (subcutaneous) as values determined by fitting the curve, whereas the 20-minute time point measurement varied at 0.29 (intravenous) and 0.37 (subcutaneous). In both the subcutaneous and intravenous models, single time point measurements at 20 minutes had the highest correlation value with AUC. This simplified single time point measurement appears appropriate to estimate the total tumor burden in this model, but the substantial variance at each measurement must be considered in experimental designs.