Figure 3

BTK is indispensable for MM cell metastasis to a new BM niche. (a) Primary bones of SCID-rab mice (five representative mice in each group, two bones contralaterally implanted in each mouse) were engrafted with luciferase-expressing INA6 MM cells infected with BTK-KD or scrambled control (CONT) shRNA. Ten weeks after engraftment, ex vivo bioluminescence of secondary implanted bones was analyzed. Secondary bones were each cut into eight pieces, placed in six-well plates and then immediately subjected to bioluminescence analysis. (b) Quantification of bioluminescence intensity in secondary bones from the BTK-KD (n=13) and CONT (n=12) groups (P<0.002). (c) Micrographs showing hematoxylin and eosin staining of sections of secondary bones, demonstrating high infiltration of MM cells (clusters of darkly stained cells) in the CONT group but not in the BTK-KD group. Numbers above the images indicate original magnifications.