Melanoma inhibitory activity (MIA), also known as cartilage-derived retinoic acid-sensitive protein (CD-RAP), is a 12-kDa protein that is secreted from both chondrocytes and malignant melanoma cells. MIA has been reported to have effects on cell growth and adhesion, and it may play a role in melanoma metastasis and cartilage development. In the presence of MIA, we observed enhanced migratory ability of melanocytic cells, induction of melanoma-associated genes as well as inhibition of apoptosis due to anoikis.
To test the effect of MIA1 on cell apoptosis, A375 cells were seeded into triplicate wells of 96-well plates at a density of 4,000 cells/well and allowed to attach overnight, then the medium was replaced with various concentrations of recombinant mouse MIA1 diluted with 5% serum standard DMEM. After incubated for 48h, cells were observed by inverted microscope and cell viability was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10 µl of CCK-8 solution was added to each well of the plate, then the absorbance at 450 nm was measured using a microplate reader after incubating the plate for 1-4 hours at 37 ℃. Apoptosis of A375 cells after incubation with MIA1 for 48h observed by inverted microscope was shown in Figure 1. The result of cell viability assessed by CCK-8 was shown in Figure 2. It was obvious that MIA1 significantly decreased cell viability of A375 cells. The ED50 of recombinant mouse MIA1 is 5.94 ug/ml.

Figure 2. Inhibition of A375 cells proliferation after stimulated with recombinant human MIA1