CXCL1 expression is inversely associated with TGF-β signaling in mammary fibroblasts. A. Conditioned medium from Flox/Flox or FspKO fibroblasts were analyzed for CXCL1 secretion by ELISA. B. Flox/Flox control or FspKO fibroblasts were co-transfected with CXCL1 firefly and Renilla luciferase reporter constructs and analyzed for luciferase activity. Values are normalized to Renilla. C.-D. Conditioned medium from carcinoma associated fibroblast cell lines (41CAF, 83CAF) or normal fibroblasts (NAF) were analyzed by ELISA for CXCL1 (C) or TGF-β secretion (D). E. Fibroblasts were treated with 5 ng/ml TGF-β for 48 hours and analyzed for CXCL1 secretion by ELISA. Statistical analysis was determined by two-tailed Student t-tests. Statistical significance was determined by p <0.05. *p ≤0.001, **p <0.05. Values are expressed as Mean ± SEM. Experiments were conducted in triplicate with three replicate samples per group.