The leukemia onset in Sca1-ETV6-RUNX1 + Kdm5cf/wt + Sca1-Cre mice housed in SPF conditions was similar to the one arising in Sca1-ETV6-RUNX1 mice exposed to infection (Rodriguez-Hernandez et al., 2017a), indicating that loss of Kdm5c may be involved in the leukemogenesis of ETV6-RUNX1+ ALL but is not the main second hit critical for disease development. This evidence concerns the gene RUNX1 and infection.