Axl and Gas6 expression in KS cells and KS tissue. (A) Expression of Axl and Gas6 in KS cell lines and endothelial cells infected by KSHV was analyzed by Western blot of whole-cell lysates. Cell lines 293T and HT29 were used as a negative control for Axl expression. A549 cell was used as a positive control. HUVEC/vector is a HUVEC line immortalized by telomerase, as described in “Cell culture.” (B) Axl, Mer, Tyro3, and Gas6 expression in human KS tissue was analyzed by immunostaining. Nuclei were counterstained with DAPI. The KS tumor regions are indicated by arrows. Images were taken with an Olympus AX70 fluorescence microscope (20× objective) and Spot Version 2.2.2 digital imaging system. (C) Confocal imaging of Axl and Gas6 colocalization in human KS tumor. (Bottom panel) Merged staining of Axl, Gas6, and nuclei. Enlarged view of the white-bordered insert in the lower left picture was shown on the right. Images were taken with a Carl Zeiss confocal microscope (100× objective) and LSM software.