CLDN4 and head and neck squamous cell carcinoma: For example, the circRNAs in a triad hsa_circ_0131624| TUBB2A–hsa-miR-338-5p—PKM in HNSCC, hsa_circ_0080517| CLDN4–hsa-miR-145—SERPINE1 in gastric cancer, and hsa_circ_0000228| ZEB1–hsa-miR-526b—MMP1 and hsa_circ_0009022| PPP4R1–hsa-miR-526b—MMP1 in liver cancer, where both the miRNAs and mRNAs from the triad play a significant role in survival, might be important in the prognosis of these cancers.