MMP9 and melanoma: Interestingly, in our present study, LL-37 increased the protein production of MMP-9 from A375 melanoma cells, whereas LL-37 increased MMP-1 from M2 macrophages in vitro, suggesting that LL-37 might promote tumor invasion not only by the stimulation of melanoma cells but also by the stimulation of TAMs in melanoma microenvironment.