In addition, an increase of NGAL/MMP-9 complexes have been found associated to a higher metastatic risk in patients with breast [42], gastric [43] and endometrial cancer [44], while NGAL knockdown in prostate cancer-derived cell lines [41] or impairment of NGAL/MMP-9 complex formation in anaplastic thyroid carcinoma-derived cell lines [45], determine a strong decrease of their metastatic potential (Figure 1B). Here, MMP9 is linked to prostate cancer.