Recently, CD4 T stem cell memory (T<sub>SCM</sub>) Fas<sup>hi</sup> cells have been identified as the hierarchical cellular apex of ATL, but a possible link between FAS, apoptosis, proliferation and IFN response in ATL has not been studied.
To investigate this phenomenon, we explored FAS transcript levels, cell-surface FAS protein expression and susceptibility to FAS-mediated apoptosis in four CTCL lines (MyLa, HH, SZ4, and SeAx), freshly isolated leukemic cells from a patient with SS, an acute lymphoblastic leukemia T-cell line (Jurkat), and JFL (a FAS-low variant of Jurkat).
In conclusion, our results demonstrate that a functional Fas promoter polymorphism is significantly associated to susceptibility, clinical manifestation, and survival in ATL.
Adult T-cell leukemia (ATL), which is abundant with Fas (Apo-1/CD95), has the characteristic feature of high tumor burden, suggesting that ATL cells probably prolong their lives as a result of escape from apoptosis.
Several groups have searched for mutations in the FAS receptor, a well-characterized apoptotic protein carrying a death domain, and reported the existence of rare mutations in multiple myeloma, T-acute lymphoblastic leukemia (T-ALL), and adult T-cell leukemia.