SOCE is critical for melanoma metastasis. (A) Expression levels of STIM1 and Orai1 in human melanocytes and melanoma cell lines derived from primary melanoma or distant metastases. The relative levels of STIM1 and Orai1 were determined through densitometry using ImageJ software. (B) STIM1 expression was up-regulated in the highly metastatic 1205Lu subline of WM793 cells. (C) Immunohistochemistry staining showing STIM1 overexpression in malignant melanoma when compared with benign nevus. Staining intensity and percentage of positively stained lesion (in magenta) and melanoma T stages (T1–T4, in black) are indicated. (D) Proportions of benign nevi (n = 21) and malignant melanoma (n = 53) with medium to high expression of STIM1; P < 0.001 as determined by two-tailed Fisher’s exact test. (E) STIM1 knockdown had no effect on the proliferation of 1205Lu cells in vitro. Data are shown as means ± SD from triplicates. The data shown are from a single experiment out of three repeats. (F–H) Inhibition of 1205Lu cell lung metastasis by STIM1 knockdown. (F) Representative bioluminescence images showing the lung metastasis of 1205Lu cells stably expressing control shRNA or STIM1 shRNA. (G) Quantification of 1205Lu cell lung metastasis using bioluminescence imaging. Normalized photon flux showed the fold increase in bioluminescence signals (on day 8 and day 36, respectively) over day 0. Box and whiskers are 25–75th and 10–90th percentiles, respectively. *, P < 0.05; ***, P < 0.001. (H) Representative hematoxylin and eosin staining showing the presence of 1205Lu metastases in the lung of nude mice. M, melanoma metastases in the lung; H, heart; sh, shRNA.