In the same study, the authors demonstrate that minor dNTP pool alterations can dramatically increase mutation rates in combination with MMR deficiency in yeast and human cancer cells (Rentoft et al., 2016), highlighting how the potential loss of SAMHD1 dNTPase activity and MMR could both contribute to the mutator phenotype of cancer cells. This evidence concerns the gene SAMHD1 and hyperinsulinemic hypoglycemia, familial, 4.