DLL3 and breast cancer: DLL3 has been described to exhibit pro-carcinogenic action in small cell lung cancer (Sabari et al., 2017; Vitorino et al., 2021), breast cancer (Ayyanan et al., 2006; Yuan et al., 2021), pituitary tumor (Wang et al., 2017) and acute myeloid leukaemia (Yan et al., 2010), but an anti-cancer effect in hepatocellular carcinoma (Maemura et al., 2013), and glioma (Turchi et al., 2013; Jungk et al., 2016).