Upregulated expression of various canonical FGFs (including FGF1, FGF2, and FGF 6–9) derived from tumor cells or stromal cells induces tumor progression in various cancers [3,4,5,6]; however, the effects of circulating hormone-like FGFs (such as FGF19, FGF21, and FGF23) on tumors are unclear. Here, FGF21 is linked to cancer.