CEM-TK(+)

CEM-TK(+) denotes thymidine-kinase-proficient CEM T-lymphoblastoid leukemia cells used as a comparator for thymidine-kinase-deficient CEM derivatives, rather than a uniquely accessioned clone; PubMed-indexed studies compare CEM-TK-positive and CEM/TK-negative cells to examine activation and cytotoxicity of nucleoside analogues or nucleotide prodrugs^[1][2]. The notation therefore describes an enzymatic phenotype within the CCRF-CEM system, but the exact parental stock, donor provenance, and clone remain unspecified in the input. For database use, retain the phenotype and research application while marking identity partial; add a repository accession or source laboratory before assigning detailed molecular characteristics or treating CEM-TK(+) as a standardized independent line.