Nonlinear dose-response of MNU in AHH-1 cells quantified through the HPRT assay (solid line). RPE was used to assess toxicity (dotted line). *p < 0.05 using two-sided Dunnett’s test with square root transformed data based on Bartlett’s test for heterogeneity of variance (p > 0.05) and Kolmogorov-Smirnov test for normality (p > 0.05).