Figure 1.

JAK2 expression and turnover in melanoma cells. A, the expression of JAK2 in human melanoma cell lines of different metastatic potential was examined by using immunoprecipitation with anti-JAK2 antibody. Nonspecific IgG was used as a loading control. B, turnover of JAK2 protein. A375P and A375Br cells were pulsed with [³⁵S]methionine for 30 min and chased for the times indicated. Cell protein extracts were used for immunoprecipitation with anti-JAK2 antibodies and subjected to SDS-PAGE and autoradiography. Left, [³⁵S]JAK2 signals were obtained from A375P (top) and A375Br (bottom) protein extracts indicating dynamics of degradation. Right, intensities of the bands were analyzed using the NIH Image software, and the integrated optical densities of the bands at time 0 were set as 100%. Note a time-dependent degradation of JAK2 in A375P and A375Br. C, SOCS-1 protein expression was determined by Western blotting. D, SOCS-1 expression in human primary and brain metastasis melanomas. Immunohistochemical staining with an anti–SOCS-1 antibody was done with 42 specimens of melanoma brain metastases, 40 specimens of primary melanoma, and 8 specimens of normal skin. Percentages of specimens with negatively, moderately, or strongly positive staining for SOCS-1 protein were shown for each group. *, P = 0.001 by χ² test.