Bioluminescence correlates with Tax expression. (A) Coregistration of photograph, BLI, and X-ray images on tail tumors with differing bioluminescent properties. (B) Comparison of bioluminescence and TAX expression on tumors arising in 2 different BNX animals injected with homogenate from a single bioluminescent primary TAX-LUC tumor. Yellow arrows indicate correspondence between tumor BLI and TAX IHC. Color scale ×104 photons/s/cm2/sr.