MMP2 and nasopharyngeal carcinoma: Because MMP2 plays an important role in the EMT state transition of CTCs, we conducted 62 CTC sample tests to explore the relationship between MMP2 protein expression in CTCs and various clinical indicators of NPC, mainly analyzing the relationship between the number of MMP2 + CTCs, the number of MMP2 + mesenchymal CTCs, and the clinical characteristics previously described.