Bone-disseminated breast cancer cells oftentimes home to the osteogenic niche, where they are exposed to glycoprotein130 (GP130) cytokines secreted by osteoblast-lineage cells. Leukemia inhibitory factor (LIF), oncostatin M (OSM) and ciliary neurotropic factor (CNTF) are GP130 cytokines that can all signal through LIF receptor (LIFR). Our lab previously showed that breast cancer cell expression of LIFR and JAK/STAT signaling promotes tumor dormancy in bone. We hypothesized that LIF, OSM, and CNTF induce pro-dormancy signaling pathways and promote tumor suppression. Treatment with recombinant LIF, OSM or CNTF (50ng/ml) robustly stimulated pSTAT3 (up to 34-fold, p<0.01-0.0001), LIF and OSM induced pERK (up to 4-fold, p<0.01-0.001), and only OSM induced pAKT (up to 9-fold, p<0.0001) in MCF7 breast cancer cells by Western blot. LIF and CNTF induced no signaling in MDA-MB-231 breast cancer cells, which have a non-functional LIFR, but OSM robustly stimulated pSTAT3 and pAKT (up to 26-fold, p<0.05-0.0001) in MDA-MB-231b cells, suggesting OSM may signal through OSM receptor (OSMR) on breast cancer cells. Reverse phase protein array (RPPA) analysis of MCF7 cells treated with recombinant LIF, OSM, and CNTF revealed several previously unknown signaling pathways and effectors to be activated, including ATM, CREB, HSP27, and N-RAS. Overexpression of OSM in MCF7 cells reduced the expression of 4/18 the pro-dormancy genes BMP7, FOXA1, IGFBP5 and TGFB2 (by 41-97.5% p<0.05-0.0001) in vitro, while treatment with recombinant cytokines or CNTF overexpression resulted in no significant changes. When orthotopically inoculated into mice (n=10/group), neither OSM nor CNTF overexpressing MCF7 cells altered the progression of tumor formation, tumor volume or weight in vivo. Together, these data suggest that the GP130 cytokines robustly stimulate multiple signaling pathways with tumor-suppressive and tumor-promoting activity, but further studies are needed to determine their effect on tumor progression and dissemination to bone.