MMP1 and gastric cancer: Several molecular targets were previously used to detect CTCs/DTCs in patients with gastric cancer, including CEA [20], mucin 1 [21], c-Met [22], human telomerase reverse transcriptase (hTERT) [23], epithelial cell adhesion molecule (EpCAM) [24], survivin [25], and matrix metalloproteinase-1 (MMP-1) [26].