DT-6 efficiently degraded intracellular TGF-β1 via the proteasomal pathway in several cancer cells (THP1, BV2 leukemia, A549, MCF-7, U87 and HepG2) and slightly downregulated IKZF3 (the neosubstrate) in M2 macrophages. Here, TGFB1 is linked to cancer.