INSIG1 and colorectal carcinoma: circINSIG1 encodes a novel protein, circINSIG1-121, which interacts with the CUL5-ASB6 complex and promotes the ubiquitination of the key cholesterol metabolism regulator INSIG1 (insulin induced gene 1) at lysine residues 156 and 158 of K48, thereby facilitating cholesterol biosynthesis and contributing to CRC proliferation and metastasis.56