TGFB1 and cancer: These mechanisms enable TGF-β signaling inhibitor (SD-208)-loaded Mφ-SDNPs to inhibit cancer metastasis and remodel the immunosuppressive tumor microenvironment (or “cold” tumor) into an immunostimulatory tumor microenvironment (or “hot” tumor) by blocking M2-type macrophage differentiation (Scheme 1).