Finally, the microenvironment might contribute to tumour dormancy or its switch to metastatic growth because the secretions and expression of MMPs by leukocytes and macrophages can lead to the release of angiogenic factors (FGF and VEGF) [44] or anti-angiogenic factors (endostatin, restin, arrestin, the three chains of collagen IV, and macrophage elastase) [45]. Here, COL18A1 is linked to neoplasm.