MUC5AC and nasopharyngeal carcinoma: In addition, it was shown that CTF1/N-Cad (CTF1) is a product of extracellular metalloproteinase (MMP), which cleaves near the interface between the extracellular and transmembrane regions of N-calcine mucin, and that the extracellular and intracellular cleavages of N-calcine mucin may be involved in elevated MMP-9 expression and enhanced invasion of human nasopharyngeal carcinoma cells (21).