CD271 Down-Regulation Promotes Melanoma Progression and Invasion in Three-Dimensional Models and in Zebrafish

CD271 is a neurotrophin receptor variably expressed in melanoma. Although contradictory data are reported on its role as a marker of tumor-initiating cells, little is known about its function in tumor progression. CD271 expression was higher in spheroids derived from freshly isolated cells of primary melanomas and in primary WM115 and WM793-B cell lines, and it decreased during progression to advanced stages in cells isolated from metastatic melanomas and in metastatic WM266-4 and 1205Lu cell lines. Moreover, CD271 was scarcely detected in the highly invasive spheroids (SKMEL28 and 1205Lu). CD271, originally expressed in the epidermis of skin reconstructs, disappeared when melanoma started to invade the dermis. SKMEL8 CD271(-) cells showed greater proliferation and invasiveness in vitro and were associated with a higher number of metastases in zebrafish compared with CD271(+) cells. CD271 silencing in WM115 induced a more aggressive phenotype in vitro and in vivo. On the contrary, CD271 overexpression in SKMEL28 cells reduced invasion in vitro, and CD271 over-expressing 1205Lu cells was associated with a lower percentage of metastases in zebrafish. A reduced cell-cell adhesion was also observed in the absence of CD271. Taken together, these results indicate that CD271 loss is critical for melanoma progression and metastasis.