PTGDR and hepatocellular carcinoma: This interaction enhances the transcriptional activity of HIF-1α by stabilizing the PLAGL2 protein, thereby forming a MAPKAPK5-AS1/PLAGL2/HIF-1α signaling loop that promotes the malignant phenotype of hepatocellular carcinoma cells, including proliferation, EMT, and metastasis (Wang L. et al., 2021).