Cell proliferation IC50s at Day 6 were 3.5 nM for GIST48B, 3 nM for GIST54, and 6.5 nM for GIST226, suggesting that bortezomib anti-proliferative effects are more pronounced in KIT-independent GIST cells (Figure 3A). The gene discussed is KIT; the disease is gastrointestinal stromal tumor.