Bone marrow progenitor cell assays of three cell lineages, i.e., colony-forming unit megakaryocytes (CFU-Meg), burst-forming unit erythrocytes (BFU-E) and colony-forming unit granulocyte-macrophages (CFU-GM), were performed for 21 patients with myelodysplastic syndromes (MDS). Markedly reduced or absent colony formation was found in 67% of the patients for CFU-Meg and all patients except 2 with refractory anemia (RA) for BFU-E. Abnormal CFU-GM colony formation was found in only 5 of 12 patients with RA and RA with ring sideroblasts, in contrast to all of the RA patients with excess of blasts and excess of blasts in transformation. Defective colony formation of all three cell lineages was seen in 63% of the MDS patients. The colony number of CFU-Meg correlated significantly with the numbers of both BFU-E and CFU-GM. These findings indicate that hematopoiesis in MDS patients is disturbed due to a qualitative or quantitative defect at the multipotent stem cell level.

The Philadelphia (Ph1) chromosome, in which the hybrid bcr-abl gene is formed, is thought to be the initial event in chronic myelogenous leukemia (CML). The position of the breakpoint within the breakpoint cluster region (bcr) on Ph1 chromosome and the splicing pattern determine the species of the fused bcr-abl messenger RNA (mRNA). We tried to detect the two types of fused mRNAs in 57 chronic-phase cases of Ph1-positive CML using the polymerase chain reaction procedure (RT- PCR). The bcr exon 2/abl exon 2 fused mRNA (b2-a2) was detected in 17 patients, the bcr exon 3/abl exon 2 fused mRNA (b3-a2) was detected in 34 patients, and both types of mRNA were detected in six patients. The platelet counts of patients who expressed b3-a2 mRNA or both types were significantly higher than those of patients who expressed only b2-a2 (841.5 v 373.5 x 10(9)/L; P less than .015), although there was no significant difference in the white blood cell counts or hemoglobin. This finding suggests a possibility that the type of bcr-abl mRNA may affect the thrombopoietic activity in CML.

Summary:We transplanted 4.1 ؋ 10 7 unrelated umbilical cord blood cells into a 27-year-old patient suffering from transformed acute myelocytic leukemia. The thawing method was the same as described by Rubinstein et al (Proc Natl Acad Sci USA 1995; 92: 10119-10122). ANC reached over 500 ؋ 10 9 /l on day 19, and the patient was free from RBC and platelet transfusion on days 26 and 38, respectively. Cytogenetic and molecular analysis after transplant revealed complete chimerism. The CD3 + CD4 + lymphocyte count became greater than 100 ؋ 10 9 /l at 5 weeks after transplantation. The CD3 + CD8 + count became greater than 500 ؋ 10 9 /l at 7 weeks and thereafter progressively increased in spite of administration of CYA. This immunological reconstitution pattern after umbilical cord blood transplantation was different from that after bone marrow transplantation, and resistance of CD3 + CD8 + lymphocytes to CYA was the distinguishing characteristic. The rapid hematological recovery and immunological reconstitution may be attributed to the high dose of transfused nucleated cells and umbilical cord blood transplantation may become a promising method for treatment for such cases.

Autoantibody against erythrocytes has occasionally been observed in patients with de novo acute myelocytic leukemia (AML). However, it is not clear whether this autoantibody in AML patients induces frank hemolysis (autoimmune hemolytic anemia, AIHA), as seen in lymphoid neoplasms. We present two de novo AML patients who showed hemolysis due to antiglobulin test-positive and test-negative AIHA, respectively. AIHA should be considered as one cause of anemia in de novo AML patients, and blood transfusions should be given carefully in such cases to avoid harmful hemolysis.

Two new myeloid cell lines (K051 and K052) were established from a patient with multilineage CD7-positive acute leukemia. The K051 and K052 were established from the patient's bone marrow cells at diagnosis and at relapse, respectively. The K051 cell expressed myeloid- associated antigens (CD13 and CD33), a platelet-associated antigen (CD41), and an erythroid antigen (glycophorin A). The K052 cell expressed myeloid-associated antigens (CD13, CD14, and CD33), lymphoid markers (CD2, CD5, and CD7), and HLA-DR. Chromosome analysis of both cell lines showed a 17p- chromosome. Both cell lines were investigated for aberrations of the p53 gene and the N-ras gene. A p53 mutation detected in both cell lines consisted of a C-->T substitution in codon 248. An N-ras mutation detected only in the K052 cell consisted of a G-- >C substitution in codon 13. Expression of the multidrug resistance gene (MDR1) was also investigated by the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). MDR1-mRNA was more highly expressed by the K052 cell than the K051 cell, being equivalent to that in HEL cells. The functional MDR1-protein against vincristine was also observed, and its function was inhibited by verapamile and Cyclosporin A. The K052 cells were capable of phenotypic or morphologic differentiation after being incubated with granulocyte colony- stimulating factor, interleukin-2, phorbol 12-myristate 13-acetate, or 1,25-dihydroxy-vitamin D3. In contrast, the K051 cells responded phenotypically to retinoic acid. Thus, the K051 and K052 cell lines will be useful for investigating the cellular and molecular events in leukemogenesis and differentiation, and the mechanism of expression of the MDR1 gene.