Abstract
Adult T-cell leukemia (ATL) is as aggressive T-cell malignancy, which was caused by human T-cell leukemia virus type I (HTLV-I). Inverse PCR analysis of HTLV-I provirus disclosed that HTLV-I infected cells proliferated clonally in vivo, and such clones survived for at least up to seven years. During such clonal proliferation, accumulating mutations of various genes have been thought to cause leukemia in vivo. We found mutations of Fas antigen, which is the key molecule of apoptosis, in the fresh ATL cells. Mutated Fas gene was also associated with drug resistancy in vivo and in vitro.
