To further analyze the role of Timp1 along the progression of melanoma, shRNA technology was used for silencing Timp1 in cell lines representing different stages of melanoma progression: pre-malignant melanocytes (4C), non-metastatic melanoma cells (4C11−), and metastatic melanoma cells (4C11+) (Figure 1A,B). Here, TIMP1 is linked to metastatic melanoma.