ITGB7 silencing reduces in vivo MM-cell extravasation and homing to the BM and decreases xenografted tumors vessel density. (A) ITGB7 silencing significantly reduced in vivo MM-cell homing after BALB/c mice tail vein injection, as detected by in vivo flow cytometry and monitoring the number of circulating calcein-AM–labeled ITGB7^silenced (●) and ITGB7^positive (○) MM1S and H929 cells over time. (B) Direct homing of CD138⁺ITGB7^silenced (bottom) and ITGB7^positive (top) MM1S cells to the BM was detected by IF staining with anti–human CD138-Cy3 labeled Ab and DAPI in mice femoral BM sections, as described in “Methods.” Shown in the inset is the mean ± SD of the percentage of human-CD138⁺ cells (red: Cy-3) in 500 BM cells counted in bilateral femoral sections from killed SCID mice (n = 3 per condition) (10×). (C) Effect of ITGB7 silencing on microvessel density measured by CD31 staining (Cy-3: red) in ITGB7^silenced (right) and ITGB7^positive (left) MM1S xenografted tumors (40×). Shown in the inset is the MVD (%) = CD31⁺ target area/total area examined as described in “Methods.” Images were aquired with an epifluorescence Olympus BX5 microscope and multispectral camera (Nuance Fx; CRi). Automated scaling of fluoresence was performed with the inForm™ analysis software (CRi).