Simultaneous tumor tracking and mitigation of immune responses to xenogeneic reporter proteins

Reporter proteins such as green fluorescent protein (GFP) and luciferase (Luc) are indispensable tools for non-invasive optical monitoring of tumors and metastases in vivo. However, as xenogeneic proteins, they can elicit T cell-mediated immune responses in immunocompetent hosts, potentially altering tumor progression and introducing bias into related studies. To overcome this limitation, we developed a doxycycline (Dox)-inducible system for controlling Luc-GFP expression. This system enables efficient, real-time monitoring of orthotopic tumor growth and metastasis in immunocompetent mouse models. Crucially, transient Dox induction produces sufficient reporter expression for detection while avoiding significant immune activation. This prevents the tumor growth inhibition and metastasis suppression observed with constitutive Luc-GFP expression or continuous induction. This inducible system provides a flexible solution for unbiased tumor tracking in immunocompetent hosts, improving the accuracy of preclinical cancer research. A doxycycline (Dox)-inducible Luc-GFP expression system that allows real-time, noninvasive monitoring of tumor progression while mitigating immune responses triggered by constitutive reporter expression.