STAT3 and hepatocellular carcinoma: Adaptor C21orf58 formed a ternary complex with signal transducer and activator of transcription 3 (STAT3) and Janus kinase 2 (JAK2) to activate wild‐type and constitutively mutated STAT3, enhancing the capacities of malignant growth and sorafenib resistance to hepatocellular carcinoma (HCC) cells.