Fig. 2

Oncostatin M (OSM) produced by tetracycline (TET)-inducible MDA-MB-231 (MDA^TO/OSM) cell MDA^TO/OSM) tumors increase metastasis and decrease survival. a MDA^TO/OSM human breast cancer cells were treated with (+TET) or without TET (−TET), and the resultant conditioned media (CM) from the treated cells were applied to parental MDA-MB-231, MDA-MB-231-LUC, and T47D cells. Left: The activity of OSM accumulated in the CM was compared with commercially obtained recombinant human OSM (rhOSM) (25 ng/ml). There was no significant difference between OSM produced by MDA^TO/OSM versus rhOSM versus its ability to induce pSTAT3. Middle: Western blot analysis depicting that CM produced by MDA^TO/OSM cells stimulated with TET contain OSM. Right: Enzyme-linked immunosorbent assay (ELISA) analysis showed that CM from TET-treated MDA^TO/OSM cells contain 10.1 ng/ml of hOSM. b Left: Animals with MDA^TO/OSM tumors were given drinking water with or without TET, and whole blood was collected at the experimental endpoint. After allowing the blood to clot and serum was separated by centrifugation, the resultant serum OSM levels were measured by ELISA. Animals with MDA^TO/OSM tumors with drinking water containing TET had 67-fold higher serum OSM levels. Center: Platelet counts were higher in +TET MDA^TO/OSM tumor-bearing mice than in −TET mice. Right: +TET MDA^TO/OSM tumor-bearing mice had lower body weight than −TET mice. c Animals with MDA^TO/OSM tumors were given drinking water containing TET for 1 week, and their lung metastasis levels were assessed by ex vivo bioluminescence imaging. Left: Representative ex vivo bioluminescence image. Right: Average radiance analysis of the ex vivo bioluminescence imaging in photons per second per square centimeter per square radian (p/s/cm²/sr). Animals with MDA^TO/OSM tumors +TET had a fivefold higher bioluminescent radiance than −TET mice (−TET, n = 3; +TET, n = 6). Data are expressed as mean ± SEM. d Kaplan-Meier survival curve for mice with MDA^TO/OSM tumors ± TET. Mice that did not receive TET survived, on average, 11 days longer (−TET, n = 9; +TET, n = 10). ***p < 0.001 by log-rank test. Data are expressed as mean ± SEM. *p < 0.05, **p < 0.01, and ***p < 0.001 by two-tailed t test or one-way analysis of variance with Tukey’s posttest where appropriate