Auer bodies in acute lymphocytic leukaemia and B-cell lymphoma: evidence for a common progenitor of myeloid and lymphoid cells?

Chronic anemia progressing to Auer rod-positive and TdT-positive acute leukemia with 5q- chromosomal anomaly

The 5q- syndrome is a recently described entity characterized by partial deletion of the long arm of chromosome No. 5 and by hematologic findings of chronic anemia with reticulocytopenia, nonlobulated megakaryocytes, and megathrombocytes. We report on a patient with the hematologic features of the 5q- syndrome who progressed to acute leukemia and whose uniqueness consisted of 1) lack of additional cytogenetic abnormalities, 2) presence of blasts with Auer rods, and 3) bone marrow cells positive for terminal deoxynucleotidyl transferase. His leukemia was refractory to conventional chemotherapy.

Conversion of a stem cell leukemia from a T-lymphoid to a myeloid phenotype induced by the adenosine deaminase inhibitor 2'-deoxycoformycin

Selective failure of lymphoid development occurs in genetic deficiency of adenosine deaminase (ADA). We examined the in vivo effects of a potent inhibitor of ADA, 2'-deoxycoformycin, which was used to treat a patient with refractory acute leukemia. Unexpectedly, within 7 days of starting treatment, the leukemic phenotype underwent complete conversion from T lymphoblastic to promyelocytic, with kinetics that suggested a precursor-product relationship between the two cell populations. Pretreatment T lymphoblasts and posttreatment promyelocytes had the same abnormal karyotype. Upon culture in vitro, the former transformed spontaneously over several weeks into mature myeloid cells. We conclude that the leukemia arose from a multipotent stem cell capable of both lymphoid and myeloid differentiation. Effects of ADA inhibition on leukemia cells during treatment included expansion of the deoxyadenosine nucleotide pool and accumulation of S-adenosylhomocysteine, a potent inhibitor of S-adenosylmethionine-dependent methylation. The influence of these changes on the leukemic phenotype is discussed in terms of (i) selective cytotoxicity to T lymphoblasts, which accumulated deoxyadenosine nucleotides more efficiently than did the patient's promyelocytes during in vitro incubation with deoxycoformycin plus deoxyadenosine, and (ii) induction of an altered program of differentiation.