All-trans retinoic acid potentiates the inhibitory effects of interferon alpha on chronic myeloid leukemia progenitors in vitro.

All-trans retinoic acid (ATRA) has recently been shown to synergize with the inhibitory effect of interferon alpha (IFN alpha) on the growth of malignant cells isolated from solid tumors. We investigated whether ATRA could potentiate the inhibitory effects of IFN alpha on the proliferation of leukemic progenitors in chronic myeloid leukemia (CML). CD34+ cells from chronic phase, newly diagnosed patients, were incubated in short-term liquid culture with ATRA, IFN alpha or a combination of both molecules and then plated on semi-solid cultures for colony-forming cell assay. IFN alpha was found to inhibit preferentially the generation of late progenitors. ATRA at a concentration of 10(-8) M was found strongly to inhibit CFU-M colonies. Addition of ATRA to IFN alpha dramatically potentiated the inhibitory effects of INF alpha on CFU-GM growth. In the presence of both molecules the inhibition of day 14 CFU-GM from CD34+ cells was lowered to 27 +/- 4% of control. CFU-M colonies were completely inhibited. RT-PCR analysis of the colonies resulting from the action of the combination IFN alpha plus ATRA showed the presence of an increased number of BCR-ABL-negative colonies relatively to what was observed with IFN alpha alone. FISH analysis showed a higher percentage of Ph-negative cells in the ATRA plus IFN alpha-treated samples, confirming PCR experiments. These results indicate that, in vitro, the combination of IFN alpha and ATRA effectively inhibits CFU-GM colony formation in CML and suggest that it has a potential interest for the treatment of CML.

5-Fluorouracil-resistant CD34+ cell population from peripheral blood of CML patients contains BCR-ABL-negative progenitor cells.

Despite the marked expansion of leukemic cells observed in the hematopoietic system of chronic myeloid leukemia (CML) patients, there is clinical and experimental evidence that normal nonclonal cells persist in the bone marrow (BM) and peripheral blood (PB) of patients in the early chronic phase. In this study, we attempt to select the benign progenitor-enriched population from the PB of CML patients. The CD34+ cells isolated from the PB of 12 CML patients in the chronic phase were treated with low doses (5 or 10 micrograms/mL) of 5-fluorouracil (5-FU). We expanded these cells for 7 days in liquid cytokine-mediated cultures. This expansion in the presence of interleukin-1 (IL-1) plus stem cell factor (SCF) plus IL-3 or leukemia inhibitory factor (LIF) plus SCF plus IL-3 seemed at least to preserve the initial clonogenic potential of CD34+ and 5-FU-resistant CD34+ cells. For the presence of BCR-ABL, mRNA from each of the 12 patients was studied by reverse-transcriptase-polymerase chain reaction (RT-PCR) on 10-15 pooled CFU-GM colonies plucked from methylcellulose cultures of starting and expanded populations. Although all PCR results were positive for colonies harvested before liquid culture, we were able to identify BCR-ABL-negative colonies from an expanded CD34+ population cultured in the presence of recombinant cytokines in 11 of 12 patients studied. 5-FU pretreatment of CML CD34+ cells markedly reduced their clonogenic potential and growth factor-mediated cell proliferation but favored higher frequency of BCR-ABL-free colonies. In conclusion, these data show that 5-FU-resistant CD34+ cells from the PB of CML patients contain normal progenitor cells, which can be selected and expanded in short-term cytokine-mediated cultures.

Inhibition of chronic myelogenous leukemia cells harboring a BCR-ABL B3A2 junction by antisense oligonucleotides targeted at the B2A2 junction.

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder characterized by the BCR-ABL hybrid gene. Two types of hybrid BCR-ABL mRNA have been found, B2A2 and B3A2. As the BCR-ABL rearrangement is specific to leukemic cells, selective inhibition of leukemic cell growth by BCR-ABL antisense oligonucleotides (ASO) has been reported in vitro for CML patients and cell lines. However, controversial results have been obtained from preclinical studies using anti-BCR-ABL ASO, as nonspecific inhibition of leukemic cell growth was evidenced in some cases. B3 exon secondary structure was deduced from its sequence and found to be a loop. According to this predictive structure of exon B3, a 56-mer antisense oligonucleotide targeting the polypurine bases from the B2A2 junction was devised which would inhibit proliferation (MTT assay) of B3A2 junction cell lines (K562 and a murine cell line Ba/F3 transfected with the B3A2 junctional sequence). This ASO had a hairpin-like secondary structure and was found to be much more resistant to the action of nucleases than control 18-mer standard oligonucleotides. Hybridization to its target mRNA occurs via formation of a triplex structure. A concentration of 5 microM of specific 56-mer B2A2 ASO was necessary to demonstrate 50% optical density (OD) reduction for K562 cell line and Ba/F3 transformed by B3A2 cDNA. Sense and non-sense 56-mer sequence or 18-mer linear ASO showed no effect for these concentrations. Western blot showed a partial inhibition of P210 protein; expression of P145abl remains unchanged. The 56-mer ASO also inhibited the proliferation of B2A2 junction cell line BV173 at the same concentration and showed no effect on the HL60 cell line used as control.

A Macintosh program for result analysis in HLA genotyping by the modified PCR-RFLP method.

We describe in this report a computer program for easy interpretation of polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) patterns generated during HLA Class II typing by the modified PCR-RFLP method. HLA-DQA1, HLA-DQB1, HLA-DRB1 and HLA-DPB1 typing result analysis are thus greatly simplified. The program also allows video capture and image storage, which are becoming a new standard in molecular biology laboratories.

Effect of antisense oligonucleotides on CD34+ cells from chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder characterized by a specific hybrid gene BCR-ABL (formed as a result of t(9;22)). This leads to two possible mRNA usually present in leukemic cells, either B2A2 or B3A2. Targeting these mRNA by antisense oligonucleotides (AS) might offer the opportunity to decrease leukemic growth. We have tested the ability of AS to inhibit the in vitro proliferation of CD34 positive (CD34+) blood cells from 16 patients with newly diagnosed CML. CD34+ cells were isolated by an immunomagnetic technique and incubated for 16 to 18 hours with an 18 mer AS (0.25 mM). Sense oligonucleotides served as controls. The effects of AS were evaluated by clonogenic test (production of CFU-GM). Moreover, colonies were picked out and studied by RT-PCR to analyse the presence of BCR-ABL transcript. For nine patients with B3A2 transcript, the median inhibition of CFU-GM formation at day 14 was 64.0 +/- 11.2% (68.0 +/- 11.4% at day 21) and for the seven patients with a B2A2 transcript: 59.0 +/- 11.4% (72.5 +/- 12.0% at day 21). AS showed no effect on CD34+ cells from three normal volunteer donor cells. However, for every patient studied, colonies picked out remained BCR-ABL positive with the RT-PCR technique.

Studies on the HLA Class-II Antigens of a Patient Presenting a Double Alloimmunization Following Posttransfusion Purpura.

In the Caucasian population, platelet incompatibility within the HPA-1 (Pl(A1/A2)) and HPA-5 (Br(a/b)) alloantigen systems are the two most likely causes of post-transfusion purpura (PTP) and neonatal alloimmune thrombocytopenia. However, the way in which HLA (class-II) antigens participate in alloantibody formation is unclear. The patient (M-J.G.) is a middle aged woman with two children who developed a severe PTP (< 2000 platelets/µ1) 8 days after receiving red cell concentrates during coronary bypass surgery. During treatment with intravenous gamma-globulin and corticosteroids, her platelet count peaked, fell again, and returned to normal over a period of several months. Western blotting and/or the monoclonal antibody specific-immobilization of platelet antigens (MAIPA) assay performed with serum prepared at the height of her initial thrombocytopenia revealed antibodies to both the Pl(A1) and the Br(a) alloantigens. This rare combination prompted us to study the expression of specific HLA class II antigens in the patient. HLA-DR and DQ typing was performed from genomic DNA by the recently developed polymerase chain reaction-restriction fragment length polymorphism procedure (PCR-RFLP). The patient was found to express the DRB1*1302/1303 and DRB3*0101/0301 alleles (serological specificities: HLA-DR6 and DR52a/c respectively). She also expressed the DQA1*0102/0501, DQB1*0601 and DQB1*0301 alleles. Thus, this case provides further evidence linking an immune response to Pl(A1) and Br(a) antigens with HLA-DR52a/c and DR6.