JUN and cancer: For instance, c-Jun has been shown to be overexpressed in diverse cancer types (Smith et al., 1999; Szabo et al., 1996), FOSL1 has been implicated as a regulator of cell proliferation and differentiation (Matsui et al., 1990), and mutations of polymerase delta 1 (POLD1), which functions in proofreading of DNA replication and replication-linked DNA repair (Prindle & Loeb, 2012), have been associated with a variety of cancer types (Rayner et al., 2016).