PTPRK and cancer: Indeed, some of the upregulated genes that may be involved in actively maintaining cell cycle arrest encode established and putative tumor-suppressor proteins including MXI1, TP53, FAT, transmembrane receptor PTK7, downregulated in ovarian cancer 1 (DOC1), tyrosine phosphatase receptor (PTPRK), N-myristoyltransferase 1 (NMT1), hypermethylated in cancer (HIC-1), tissue inhibitor of metalloproteinases-3 (TIMP3), and cadherin 11 (CDH11). This underscores the idea that tumorigenesis, in part, involves escape from an actively maintained nondividing state.