SOX21 and hepatocellular carcinoma: The long non-coding RNA (lncRNA) SOX21 antisense RNA1 (SOX21-AS1), which is overexpressed in several cancers including HCC, colorectal cancers, and lung adenocarcinoma [149,150,151], acts as a positive co-regulator to promote TSPAN8 transcription by the transcription factor GATA6, therefore increasing the migration and invasion of cancer cells [152].