(a,b) 6AN did not interfere with the ability of regional PDAC samples to form tumors in 3D Matrigel assays (a) or in 3D suspension tumorsphere assays (b). n = 2–4 technical replicates; error bars, s.d. (c) In contrast, 6AN strongly blocked the ability of distant metastatic subclones to form tumors in 3D suspension tumorsphere assays. n = 4 technical replicates; error bars, s.d. *P < 0.003, two-tailed t test. Scale bars, 400 μm.