Transport of 14C-deferiprone in normal, thalassaemic and sickle red blood cells.

The transport of deferiprone (L1) in normal (N), sickle (S) and thalassaemic (T) red blood cells (RBC) was determined by incubation with 14C-L1 at 37 degrees C. Following incubation with 0.5 mM 14C-L1 for 4 h, the intracellular concentration of L1 in T RBC was 3 times higher than was found extracellularly. In contrast, no concentration gradient across N and S RBC membranes was detected. Efflux studies showed that T RBC released only 17 +/- 2% of 14C-L1 into the extracellular space. We hypothesize that L1 accumulation in T RBC results from their high content of chelatable iron and formation of large, hydrophilic L1-Fe(III) complexes trapped within the cytosol.

Lack of clonal BCRA2 gene deletion on chromosome 13 in chronic lymphocytic leukaemia.

Chromosome 13q deletion is among the most common cytogenetic abnormalities in chronic lymphocytic leukaemia (CLL). We investigated the 13q14.3 deletion in 44 CLL patients by Southern blotting following purification of clonal B CLL cells to >90%. Two sets of probes were used to investigate the site of clonal deletion, the D13S25 and D13S319 markers (at 13q14.3) and probes for exons 11 and 26-27 of the BRCA2 gene (at 13q12). Homozygous and heterozygous deletion at the 13q14.3 region was found in five and 17 patients, respectively. Despite the recent report of the BRCA2 gene involvement in >80% of CLL patients, we failed to detect a single case of homozygous or heterozygous deletion involving the 13q12 region. Our data support previous findings that the 13q14.3, and not the 13q12 region, is the major site of candidate tumour suppressor gene(s) in CLL.

Regulation of bcl-2 and fas expression in primary activation of human peripheral lymphocytes is not sensitive to dexamethasone or cyclosporin-A.

The regulation of bcl-2 and fas (Apo-1/CD95) gene product expression plays a significant role in lymphocytes proliferation, survival, and apoptosis. Dexamethasone (Dex) and the immunosuppressive agent cyclosporin-A (CsA) inhibit primary activation of lymphocytes by distinct, though overlapping mechanisms that trigger undefined signals and can induce or prevent apoptosis in lymphoid cells in vitro. Here we demonstrate that Dex and CsA, at concentrations that markedly inhibit phytohemagglutinin (PHA)-induced proliferation of normal human peripheral blood lymphocytes, suppress the activation-dependent expression of interleukin 2 (IL-2) and the alpha-chain IL-2 receptor in a dose-dependent fashion without affecting the inducible accumulation and kinetics of either bcl-2 or fas mRNAs. Similar results were obtained when PHA-stimulated lymphocytes were cultured in the presence of the CsA analogue FK-506 or rapamycin. Moreover, the inducible maximal expression of either bcl-2 or fas protein levels on 48-h PHA-activated lymphocytes was not changed in the presence of either Dex or CsA. These findings show that the cell activation-induced biosynthesis of bcl-2 and fas proteins is not affected by immunosuppressive agents, suggesting that the expression of IL-2 and both bcl-2 and fas genes is regulated through independent mechanisms.

Relapse of acute promyelocytic leukemia follows serial negative RT-PCR assays: a cautionary tale.

Six patients with acute promyelocytic leukaemia (APL) and t(15;17) were investigated by cytogenetics and by reverse transcriptase polymerase chain reaction (RT-PCR) for the fusion transcript PML-RARA. The clone was detected in remission following all-trans retinoic acid and chemotherapy by cytogenetics and/or by RT-PCR up to 2 months from diagnosis. Thereafter the PML-RARA transcript was not seen in 20/21 first remission samples in five cases studied. Remission was maintained in two patients, one following bone marrow transplantation (BMT). Despite serial negative RT-PCR results, PML-RARA reemerged at or prior to relapse following BMT in the remaining three cases. Frequent molecular monitoring and caution in the interpretation of negative RT-PCR results are indicated in APL.

The use of IgH fingerprinting and ASO-dependent PCR for the investigation of residual disease (MRD) in ALL.

In acute lymphoblastic leukaemia (ALL), investigation of minimal residual disease by conventional morphology and immunology fails to detect levels of residual disease of < 1 leukaemic in 10-100 normal cells. The use of polymerase chain reaction (PCR) to exploit the diversity of the complementarity determining region (CDR) and immunoglobulin variable heavy chain (VH) family specific usage has greatly improved the sensitivity up to one leukaemic cell in 10(5)-10(6) normal bone marrow cells. Here we report on a prospective study of 14 patients with ALL of B-cell lineage by using a combined PCR approach which estimates levels of disease between 1:10(3) and 1:10(5). The sequential use of allele-specific oligoprimer (ASO) independent tests (using framework 1. FR1 and 3, FR3 primers with a JH consensus primer, sensitivity up to 1:5 x 10(3)) and ASO-dependent PCR (sensitivity up to 1:10(5)) assays were applied to 64 bone marrow (BM) follow-up samples in a sequential array of tests. Results presented in this study indicate high concordance of MRD among different tests for samples with level of residual disease > 1:5 x 10(3). Consequently, samples positive by the FR1 and FR3 fingerprinting tests were confirmed by the more sensitive ASO-dependent tests, as expected. However, the ASO-dependent assays revealed levels of disease undetected by the FR1 and FR3 test. Although a higher level of sensitivity is provided by the ASO-dependent tests, the FR1 and FR3 fingerprinting tests allow MRD investigation in patients with oligoclonal B cell proliferations, CDR3 region of size < 15 bp or with ASO primers unsuitable for PCR investigation on technical grounds (i.e. background signal). If a sequential order of investigation from less (e.g. FR1 and FR3 fingerprinting) to more sensitive tests (ASO-dependent) is applied, an indirect estimate of MRD is obtained for patients with level of disease < 1:10(3).

JM, a Thy-ALL cell line produces both inhibitory and stimulatory lymphokines for bone marrow progenitor cells.

Normal and malignant T cells as well as T-cell hybridomas have frequently been reported to produce factors which stimulate the growth of committed hemopoietic progenitors. One previous report described a lymphokine produced by a T-cell clone which inhibited hemopoietic progenitor cell proliferation. We now describe the simultaneous production of two activities by a Thy-ALL cell line (JM), a sub-line of Jurkat. Two sets of culture conditions were used: the Fauser & Messner and Iscove's assays. We have been able to separate both inhibitory and stimulatory factors for the growth of multipotent and committed bone marrow progenitors (CFU-GEMM, BFU-E, CFU-E and CFU-GM). The stimulatory factor has an apparent mol. wt of less than 30,000 and the inhibitor an apparent mol. wt of 65-80,000. The growth promoting activity for BFU-E and CFU-GEMM could replace that of phytohemagglutinin stimulated leucocyte conditioned medium (PHA-LCM). We do not know if the production of both activities is due to the malignant phenotype or if there is a normal counterpart to JM that could produce both inhibitory and stimulatory factors.