Proinflammatory cytokines TNFα and IL-6 promote dissemination of MM. (A) Analysis of circulating tumor cells in tumor-bearing mice (4-6 weeks post tumor challenge), before (pre) and 2 hours (hr) after (post) treatment for 2 days with recombinant cytokines rTNFα or rIL-6. (B) Analysis of circulating tumor cells in tumor-bearing mice (4-6 weeks post tumor challenge) at 24 hours after treatment for 2 days with rTNFα or rIL-6. (C) Cell tracks of myeloma cells (n = 99) after time-lapse imaging in the BM focus before and 0 to 2 hours after treatment with rTNFα (1 µg) and analysis of their track speeds. (D-E) Analysis of tumor burdens in tibias and dissemination index in IL-6 and WT hosts after intratibial tumor inoculation. (F) Analysis of tumor burden in bones after intravenous (i.v.) tumor inoculation. (G-H) Comparison of tumor burdens (as in panel D) in TNFα^−/−, TNFR^−/−, and WT control mice. (I-J) Analysis of tumor burden and dissemination index in chimeric hosts, generated from lethal irradiation of recipient mice and reconstitution with donor BM cells as labeled. All experiments were independently repeated at least 2 times. Data points represent individual mice, and data from multiple experiments were pooled; comparisons were analyzed by using a Mann-Whitney t test. *P < .05; **P < .01; ***P < .001; ****P < .0001. Thick horizontal lines are means throughout; error bars are standard deviation in panels C and F and SEM in panel E.