NUPR1 and melanoma: We define the melanoma cells that are selected and grown in 90-Pa fibrin gels for 5 days as TRCs.3 Importantly, Nupr1 expression in the cells plated on 2D substrates increased by >7-fold when substrate stiffness was increased from 150-Pa to 8 kPa or rigid plastic (Figure 1b), suggesting that it is the substrate rigidity and not the substrate dimensionality that dictates Nupr1 gene expression.