Preclinical In Vivo Imaging is a technique that allows scientists to observe biological processes at the cellular level in real time. Preclinical In Vivo Imaging has been especially useful for imaging the tumor microenvironment (TME) and tracking the complex interactions between tumor cells and immune system cells that can result in tumor growth and development or tumor regression. Preclinical In Vivo Imaging is a noninvasive technique that relies on visualization of specific cells that emit light through bioluminescent reactions that can be detected within living animal models with highly sensitive cameras. Here we provide an overview of bioluminescence-based Preclinical In Vivo Imaging methods that are being used in preclinical oncology research.

Bioluminescence imaging (BLI) is a highly sensitive non-invasive molecular imaging technique that has been used across biological research areas for insights into how tissues and organs function in real-time under normal physiological conditions or different disease states. BLI was developed using transgenic mice that expressed the luciferase enzyme as a reporter in specific cells. These cells can be visualized in the presence of oxidated luciferin substrate, which generates bioluminescent light (photons) that can be detected using microscope-based or portable photon detectors[1]. This method can detect biologically active tumor cells and can monitor changes in the growth or clearance these cells because bioluminescence is an ATP-dependent process in living animals[2], [3]. More recently, functional BLI probes have been developed that use caged luciferin substrates that must be cleaved through a specific biological process for luminescence[4]. These functional probes have been useful in monitoring metabolism and enzyme activity, and such read-outs can be used to understand basic tumor biology or identify mechanisms of action for anti-tumor drugs.