Tax induces IL-6 expression in tumor cells. (A-B) Real-time RT-PCR of IL-6 and RANKL normalized to GAPDH from 7 CD16/CD32-fractionated Tax tumors from 7 mice. RANKL was expressed in normal lymphocytes/stromal cells, whereas IL-6 was expressed in Tax tumor cells. All data are depicted as the mean ± SEM. (C) The preosteoblast cell line ST-2 was transduced with MSCV-Tax-GFP or MSCV-GFP. Controls were nontreated ST-2 cells and ST-2 cells treated with vitamin D for 3 days. Left panel pictures were taken under phase contrast microscopy; right panel pictures were taken under FITC channel of conventional fluorescent microscopy. (D) MSCV-Tax transduction in ST-2 cells induces IL-6 and TNFα expression but not RANKL. RT-PCR of selected osteoclast-activating factors was performed on cDNAs from transduced ST-2 cells, vitamin D–treated ST-2 cells, and nontreated ST-2 cells. (E) Serum was obtained retroorbitally, and IL-6 levels were determined by ELISA. Results for Tax⁺ (n = 17) and wild-type (n = 19) mice are shown as picogram per milliliter. Tax⁺ mice have increased serum IL-6 levels (P < .05). Values are depicted as the mean ± SEM.