ROBO3 and Burkitt lymphoma: To examine an involvement of IL-6 in ROBO3-mediated STAT3 activation, we treated BL subtype cells exogenously with IL-6, which induced coexpression of p-STAT3 and ROBO3 in immunocytochemistry staining, as well as nuclear localization of p-STAT3 (Figure 5B and Supplemental Figure 4A).