Ricardo Amaru

Molecular Diagnosis and Clinical Relevance of t(9;22), t(4;ll) and t(l;19) Chromosome Abnormalities in a Consecutive Group of 141 Adult Patients with Acute Lymphoblastic Leukemia

Over a time period of five years leukemic blast samples from 141 consecutive patients with adult ALL were referred to our laboratory, for molecular evaluation of chromosome abnormalities. The t(9;22), t(4;11) and t(1;19) which are most commonly found in adult ALL with a B-precursor phenotype were molecularly analyzed by similar RT-PCR based protocols. BCR-ABL transcripts generated by the t(9;22) translocation were demonstrated in 36 patients (25%) and were restricted to the 109 patients with B precursor ALL (33% of this group). Of 83 patients showing a, common phenotype (CD10+), 34 were BCR-ABL positive (41%) whereas only 2 out of 26 with Null ALL (HLADr+, CD19+, CD10) were positive. Interestingly, the percent of BCR-ABL positive CD1O+ ALL increases significantly with age being 20% in patients less than 30 years old and more than 50% in older patients. None of the T-ALL (24 patients) and B-ALL (8 patients) were positive. The majority of cases (67%) showed the p190 gene subtype. The cytogenetic diagnosis of Philadelphia chromosome was always confirmed by the molecular analysis and this approach allowed for the detection of the presence of the BCR-ABL rearrangement in 26 patients when a negative result or no metaphases were obtained. The complete remission rate was similar among BCR-ABL positive and negative patients but a shorter remission duration was observed in those showing molecular evidence of t(9;22) and this finding was significantly evident in CD1O+ ALL patients. By means of comparison, in most of the same adult ALL patients, we analyzed the yet unrecognized prevalence of the t(4;11) and t(1;19) translocations by the molecular analysis of their chromosomal breakpoints. Rearrangements of the ALL-1 gene on 11q23 band and ALL- l1AF.4 fusion transcripts specific for the t(4;11) were demonstrated in 7 out of the 21 Null ALL investigated, with no additional positive cases found among the other ALL subgroups. Overall the clinical behavior of t(4; 11) positive patients was dismal with a very short CR duration. Chimeric E2A-PBX1 transcripts generated by the t(1;19) were found in only two of the 87 B-precursor ALL analyzed. The presented results provide further evidence for the utility of RT-PCR based methods for the molecular diagnosis of chromosome translocations in ALL. The identification of such abnormalities can significantly contribute to the identification of more appropriate therapeutic options for standard and high risk ALL patients

Flow cytometry of leucocyte alkaline phosphatase in normal and pathologic leucocytes

Leucocyte alkaline phosphatase (LAP) is an enzyme expressed on the external aspect of the neutrophilic granulocyte plasma membrane, and represents a specific marker for the fully differentiated granulocyte. In this report we characterize 1B12.1, a monoclonal antibody raised against human bone alkaline phosphatase, by its ability to recognize the LAP protein. As assessed by Western blot analysis, following electrophoresis under non‐reducing conditions, the antibody specifically reacts with LAP upon forced expression of the protein in simian COS‐7 fibroblasts. In addition, the 1B12.1 antibody recognizes partially purified LAP isolated from peripheral blood granulocytes. With this antibody we developed a quantitative flow‐cytometry‐based method for the determination of LAP. Double fluorescence flow cytometry demonstrated that the LAP protein was present in relatively high amounts in neutrophilic granulocytes, but not in monocytes, natural killer cells, or B and T lymphocytes of normal individuals. The protein was completely absent in granulocytes obtained from chronic myeloid leukaemia and paroxysmal nocturnal haemoglobinuria patients. Higher than normal levels of LAP protein were evident in neutrophilic granulocytes of patients suffering from polycythaemia vera, essential thrombocythaemia and severe aplastic anaemia. However, the highest amounts of LAP protein were present in the granulocytes of normal individuals treated with G‐CSF for the isolation of peripheral blood stem cells.

Molecular characterization of a new recombination of the SIL/TAL-1 locus in a child with T-cell acute lymphoblastic leukaemia

Summary. Deletions involving the SIL‐TAL‐1 locus are seen in 15% of T‐acute lymphoblastic leukaemias (T‐ALL). To date, seven deletions have been described, spreading over 90 kb of chromosome 1, fusing SIL to the TAL‐1 gene and resulting in over expression of TAL‐1. During the diagnostic screening of the TAL‐1 deletion in 176 T‐ALL patients, we identified one case showing a new SIL rearrangement. A novel fusion transcript was identified between the SIL exon 1a and an unknown sequence (633‐cDNA). Polymerase chain reaction (PCR) screening of a human cDNA library confirmed the existence of this transcript. Using long‐distance PCR on patient DNA, we obtained a genomic fragment containing SIL exon 1b, a portion of intron 1b, an unknown sequence and the 633 sequence. Using DNA from healthy donors, a partial genomic map of 633‐DNA was found to be identical to the restriction map of the PCR fragment amplified from patient DNA. To define the chromosomal origin of 633‐DNA, a YAC human genomic library was screened. Two clones containing 633‐DNA were found, mapping to chromosomal region 1p32 and both contained SIL and TAL‐1 sequences. By searching GenBank, we identified PAC RP1‐18D14 which contains SIL, TAL‐1 and 633‐DNA, confirming this novel rearrangement as a new deletion of the SIL/TAL‐1 locus.

Unexpected remission of acute myeloid leukaemia after GM‐CSF

Summary. The administration of granulocyte‐monocyte colony‐stimulating factor (GM‐CSF) was associated with complete clinical and haematological response in an adult patient with minimally differentiated acute myeloid leukaemia who presented with pneumonia and moderate neutropenia, but no blast cells in the peripheral blood. The response lasted 9 months. At relapse, a second GM‐CSF course resulted in a very good partial remission lasting 5 months, although differences in the kinetics of haemoglobin, neutrophil and platelet recovery were noted. Subsequent recurrences were managed with chemotherapy, a complete remission being obtained twice more and lastly consolidated with myeloablative chemo‐radiotherapy supported by a peripheral blood stem cell autograft. This report suggests that GM‐CSF should be further investigated as a therapeutic agent in selected cases of AML.

The Natural History of Monoclonal Villous Lymphocytosis: A Chronic Lymphoproliferative Disorder of CD11c+ B Cells

The long-term outcome of three asymptomatic subjects with isolated persistent lymphocytosis of monoclonal villous B-cells (MVL) is reviewed. After 7.5 years, evolution to a splenic lymphoma variant (SLVL) was documented in only one patient, accompanied by a loss of interleukin-1beta autocrine production, confirming that MVL can be an early form of a malignant disorder. The clinical course was uneventful in the other two cases; a progressive lowering of lymphocyte count being noted in one. While the strict relationship of MVL to SLVL is confirmed, time to progression is unpredictable and the mechanisms by which it occurs still remain to be elucidated.