Purpose: Transforming growth factor-β (TGF-β) induces alternative macrophage activation that favors tumor progression and immunosuppression. Meanwhile, paclitaxel (PTx) induces macrophage (Mφ) polarization towards antitumor phenotype. TGF-β also increases tumor stroma macrophage recruitment by mechanisms that include cell motility enhancement and extracellular matrix degradation. In this study, we aimed to determine whether PTx regulates macrophage migration and urokinase-type plasminogen activator (uPA) expression induced by TGF-β.
Methods: We used mouse macrophage RAW 264.7 cells treated with PTx and TGF-β combinations. Proliferation was analyzed by MTT and cell cycle assays. Immunofluorescence was performed to determine tubulin cytoskeleton and Smad3 nuclear localization. Western blot and transcriptional luciferase reporters were used to measure signal transduction activation. Migration was determined by wound healing assay. uPA activity was determined by zymography assay.
Results: PTx decreased RAW 264.7 cell proliferation by inducing G2/M cell cycle arrest and profoundly modified the tubulin cytoskeleton. Also, PTx inhibited TGF-β-induced Smad3 activation. Furthermore, PTx decreased cell migration and uPA expression stimulated by TGF-β. Remarkably, p38 MAPK mediated PTx inhibition of uPA activity induced by TGF-β but it was not implicated on cell migration inhibition.
Conclusions: PTx inhibits TGF-β induction of mouse Mφ migration and uPA expression, suggesting that PTx, as TGF-β targeting therapy, may enhance Mφ anticancer action within tumors.