SMAD4 and neoplasm: HNF4A-AS1 encodes a small 51-amino acid peptide called sPEP1, which directly interacts with eukaryotic translation extension factor 1α-1 (eEF1A1) to promote its binding to SMAD family member 4 (SMAD4) and subsequently upregulates stem cell genes associated with tumor progression and promotes tumor metastasis [181].