MERTK and cancer: An important, newly discovered role of MERTK is as an innate immune checkpoint in cancer (Cook et al., 2013; Davra et al., 2021; Huelse et al., 2020; Lee-Sherick et al., 2020; Lin et al., 2022; Lindsay et al., 2021; Sekar et al., 2022; Su et al., 2020; Wu et al., 2018; Zhou et al., 2020).