Although treatment of TGF-β or active PLK1 upregulates TSG6 expression, the depletion of TSG6 reduced the levels of PLK1 or TGFB1, suggesting that TSG6 and PLK1 or TGFB1 could mutually trigger their expression for cancer metastasis (Fig. 6k). This evidence concerns the gene TNFAIP6 and cancer.