Use of Adult T-Cell Leukemia/Lymphoma Cell Lines in a Novel Proteomic Approach for Clarifying the Function of Human Proteins of Unknown Function

Clarifying the function of approximately 20,000 proteins encoded by the human genome is a key challenge in the fields of medicine and biology. However, many proteins remain uncharacterized. In this review, we introduce a challenge that uses adult T-cell leukemia/lymphoma (ATL) and proteomics to study human proteins of unknown function (PUFs). The characteristic properties of ATL cells are as follows: ATL cells (1) are infected with virus, (2) are derived from CD4+ T cells, (3) are generated via multi-stage carcinogenesis, (4) have flower-like nuclei, and (5) are highly infiltrative in the aggressive type. Given that ATL cells have contributed to impressive basic research, such as the discovery of HTLV-1 as a human cancer virus and interleukin-2 (IL-2) receptor α chain (IL-2Rα)/CD25, which is used for identifying regulatory T (Treg) cells, ATL cell lines could still be considered an attractive research tool. Furthermore, the “Unknome database” is useful for examining function-unknown degrees of proteins of interest using known scores based on Gene Ontology (GO) annotations and protein analysis through evolutionary relationships (PANTHER). Combining ATL proteomic data obtained by us with the “Unknome database” is expected to contribute not only to investigating the pathogenetic mechanism of ATL but also to clarifying the functions of PUFs.