SP1 and colorectal carcinoma: FGF19-FGFR4 upregulated ELF4 expression by activating the ERK1/2/SP1 axis, and elevated ELF4 promoted CRC metastasis through upregulating FGFR4 and protein tyrosine kinase SRC expression, which formed the FGF19-ELF4-FGFR4 positive feedback circuit.