Cell-cycle checkpoints are stringent quality control mechanisms that regulate cell-cycle progression and division. Cancer cells often develop a dependency on the G2-M cell-cycle checkpoint to facilitate DNA repair and resolve intrinsic or therapy-induced DNA damage. This dependency leads to therapy resistance, continuous cell division, and disease progression. Targeting G2-M checkpoints has been heavily pursued over the past two decades and has progressed into clinical studies. Recent genome-scale functional genomic studies have revealed that protein kinase, membrane-associated tyrosine/threonine 1, an essential but previously overlooked molecule for the G2-M checkpoint, is a promising target for multiple types of cancers. In this work, we summarize the latest discoveries in molecular targeting of protein kinase, membrane-associated tyrosine/threonine 1, and discuss the challenges and limitations in expanding its clinical application.