[Acute promyelocytic leukemia with CD59 deficiency].

CD59 is a glycosyl-phosphatidyl inositol-anchored protein with the capacity to block the formation of membrane-attack complex, and protect the cells from complement-mediated cytolysis. The study was aimed to investigate whether CD59 is deficient in acute promyelocytic leukemia (APL) blast cells. Expression of CD59 on APL blast cells was analysed by flow cytometry. Expression of CD59 on NB4 cells was determined by flow cytometry before and after treating with all trans retinoic acid (ATRA). Pig-A gene coding region was sequenced. The results showed that the deficiency of CD59 expression in 12 out of 19 APL samples was found, its incidence was significantly higher than that in other acute myeloid leukemia (AML) samples (deficiency of CD59 expression in 14 of 40 non-APL AML samples, p=0.042). The expression of CD59 became normal after the patients achieved complete remission (CR), which indicated that the deficient of CD59 expression was only found in APL blast cells, but also found in APL cell line NB4 cells. The expression of CD59 was not changed after NB4 cells were induced to differentiate by ATRA. Sequencing pig-A gene coding region of NB4 cells and one APL patient with deficiency of CD59 displayed that the mutation of pig-A gene was not observed, therefore the deficiency of CD59 expression in APL cells did not result from mutation of pig-A gene. It is concluded that the deficiency of CD59 expression exists in APL blast cells more probably.