MBD2 and neoplasm: Moreover, since the demethylase activity of KDM5A and B underlies their tumor-promoting roles (Vinogradova et al., 2016) and KDM5A/B inhibition is particularly promising in RB-deficient tumor cells (Oser et al., 2019), a potential mechanism of KDM5 inhibition by RB may lead the way towards novel approaches to interfere with oncogenic activities of KDM5 demethylases in defined contexts.