RB1 and neoplasm: For example, interfering with KDM5A expression or inhibiting its demethylase activity reduced tumor initiation and growth in RB-deficient mice, significantly expanding life span (Lin et al., 2011; McBrayer et al., 2018), and decreased cellular heterogeneity in a small cell lung cancer (SCLC) cell line (Varaljai et al., 2015).