Abstract
Purpose: :
Uveal melanoma is associated with a high rate of metastatic death. Metastasis has been strongly linked to loss of chromosome 3 and a distinct "class 2" gene expression signature that features down-regulation of several genes on chromosome 3 involved in melanocyte biology. Here we investigate the hypothesis that loss of expression of the master regulator of melanocyte differentiation, Mitf, which is located on chromosome 3p, may be important in uveal melanoma progression.
Methods: :
Mitf protein was depleted at least 95% in Mel202 uveal melanoma cells using targeted siRNA. Cells were then assessed for changes in morphology, growth rate, BrdU incorporation, scratch wound healing, colony formation in soft agar, and invasion through collagen.
Results: :
Knock-down of Mitf protein levels in uveal melanoma cells resulted in a shift from a more spindle-like to a more polygonal, epithelioid-like morphology, redistribution of β-catenin from the cytoplasm and nucleus to the cell membrane, and loss of pigmentation. Knockdown of Mitf also resulted in a decreased growth rate and accumulation of cells in G1 phase of the cell cycle. Finally, Mitf knockdown resulted in decreased motility, invasion and anchorage independence.
Conclusions: :
Loss of Mitf results in profound changes in the phenotype of uveal melanoma cells that may be important in tumor progression. These studies could lead to important new insights into uveal melanoma pathobiology and suggest novel therapeutic interventions.
Keywords: melanoma • transcription factors • gene/expression