MELK and cancer: In vitro anti-proliferative assay using A549 (lung), T47D (breast), DU4475 (breast), and 22Rv1 (prostate) cancer cells, in which MELK was highly expressed, revealed IC50 values of 6.7, 4.3, 2.3, and 6.0 nM, respectively (Fig 2A-D).