Hemophilia therapy innovation: development of an advanced category recombinant factor VIII by a plasma/albumin-free method. Proceedings of a Special Symposium at the XIXth Congress of the International Society on Thrombosis and Haemostasis, July 12-18, 2003, Birmingham, UK

Replacement therapy for hemophilia A has evolved from the early use of whole blood, citrated plasma, and cryoprecipitate, to purified factor VIII (FVIII) concentrates, first derived from plasma, then produced by recombinant DNA technology. Recombinant FVIII (rFVIII) concentrates have provided improved safety for patients with hemophilia A since they significantly reduce the risk of transmission of blood-borne infections. Nevertheless, human- or animal-derived plasma proteins are still included at some step in preparation of all previously licensed rFVIII, thereby introducing the potential for transmission of human or animal pathogens. Anti-hemophilic factor (recombinant), plasma/albumin-free method (rAHF-PFM), a novel advanced category rFVIII produced without the addition of human or animal plasma proteins, has been developed with the goal of providing the greatest possible margin of safety to hemophilia patients. This report, based on a symposium of the XIXth International Society on Thrombosis and Haemostasis Congress, provides an overview of the rAHF-PFM development program as well as current findings from the global clinical evaluation of rAHF-PFM in pediatric and adult previously treated patients.

Residual bone marrow leukemic progenitor cell burden after induction chemotherapy in pediatric patients with acute lymphoblastic leukemia

We used highly sensitive multiparameter flow cytometry and blast colony assays to quantify the leukemic progenitor cell (LPC) burden of postinduction chemotherapy bone marrows from newly diagnosed and relapsed pediatric patients with acute lymphoblastic leukemia (ALL). Of 890 newly diagnosed patients, 243 (27%) had detectable LPC in the postinduction bone marrow samples with an average (mean +/- SE) LPC content of 22+/-9 LPC/10(6) mononuclear cell (MNC; range, 0-7199/10(6) MNC; median, 0/10(6) MNC). By comparison, 24 of 50 (48%) patients with relapsed ALL had detectable LPC in their postinduction bone marrow specimens (P = 0.003), and their average LPC content was 202+/-139 LPC/10(6) MNC. Fewer patients with B-lineage ALL (170 of 786; 22%) than patients with T-lineage ALL (73 of 104; 70%) harbored residual LPC in their postinduction bone marrow specimens (P < 0.0001). This correlation with immunophenotype was independent of the National Cancer Institute risk classification. Similarly, 19 of 44 (43%) patients with relapsed B-lineage ALL versus 5 of 6 (83%) patients with relapsed T-lineage ALL harbored residual LPC in their postinduction bone marrow specimens (P = 0.09). Among newly diagnosed patients, those with high-risk ALL seemed to have larger numbers of residual LPC in their bone marrow after induction chemotherapy than those with standard risk ALL (53+/-26, n = 286 versus 7+/-1, n = 604, P = 0.04). LPC of patients with standard risk ALL who had a slow early marrow response at day 7 seemed to be more resistant to the three-drug induction chemotherapy than patients who had a rapid early marrow response. Overall, the order of chemosensitivity of LPC was: newly diagnosed standard risk B-lineage > newly diagnosed higher risk B-lineage > newly diagnosed standard risk T-lineage > newly diagnosed higher risk T-lineage > relapsed B-lineage > relapsed T-lineage. Notably, LPC- patients whose end-of-induction remission bone marrow specimens had zero LPC had an excellent early event-free survival outcome. Within the standard and high-risk subsets, LPC- patients had a 2.6-fold lower and 2.4-fold lower incidence of events, respectively, than LPC+ patients. At 6 months, 12 months, as well as 24 months, the ranking order for better event-free survival was: standard risk, LPC- > high risk, LPC- > standard risk, LPC+ > high risk, and LPC+.

Expression of aberrantly spliced oncogenic ikaros isoforms in childhood acute lymphoblastic leukemia

PURPOSE

We sought to determine if molecular abnormalities involving the Ikaros gene could contribute to the development of acute lymphoblastic leukemia (ALL) in children.

PATIENTS AND METHODS

We studied Ikaros gene expression in normal human bone marrow, normal thymocytes, normal fetal liver-derived immature lymphocyte precursor cell lines, eight different ALL cell lines, and leukemic cells from 69 children with ALL (T-lineage ALL, n = 18; B-lineage ALL, n = 51). Expression of Ikaros protein and its subcellular localization were examined by immunoblotting and confocal laser-scanning microscopy, respectively. Polymerase chain reaction (PCR) and nucleotide sequencing were used to identify the specific Ikaros isoforms expressed in these cells. Genomic sequencing of splice junction regions of the Ikaros gene was performed in search for mutations.

RESULTS

In each of the ALL cases, we found high-level expression of a non-DNA-binding or aberrant DNA-binding isoform of Ikaros with abnormal subcellular compartmentalization patterns. In contrast, only wild-type Ik-1 and Ik-2 isoforms with normal subcellular localization were found in normal bone marrow cells and thymus-derived or fetal liver-derived normal lymphocyte precursors. In leukemic cells expressing the aberrant Ikaros coding sequences with the 30-base-pair deletion, genomic sequence analysis of the intron-exon junctions between exons 6 and 7 yielded the wild-type sequence. We identified a single nucleotide polymorphism (SNP) affecting the third base of the triplet codon for a proline (CCC or CCA) in the highly conserved bipartite activation region (viz, A or C at position 1002 numbering from the translation start site of Ik-1) within our Ikaros clones. Bi-allelic expression of truncated and/or non-DNA-binding isoforms along with wild-type isoforms was observed in leukemic cells, which implicates trans-acting factor(s) affecting splice site recognition.

CONCLUSION

Our findings link specific molecular defects involving the Ikaros gene to childhood ALL. Posttranscriptional regulation of alternative splicing of Ikaros RNA seems to be defective in leukemic lymphocyte precursors from most children with ALL. Consequently, leukemic cells from ALL patients, in contrast to normal lymphocyte precursors, express high levels of non-DNA-binding Ikaros isoforms that are reminiscent of the non-DNA-binding Ikaros isoforms that lead to lymphoblastic leukemia in mice.

Expression of dominant-negative Ikaros isoforms in T-cell acute lymphoblastic leukemia

Ikaros, a zinc finger-containing DNA-binding protein, is required for normal lymphocyte development. Germ-line mutant mice that express only non-DNA binding dominant-negative "leukemogenic" Ikaros isoforms lacking critical NH2-terminal zinc fingers develop an aggressive form of T-cell leukemia. We studied Ikaros gene expression in leukemic cells from 18 children with T-cell acute lymphoblastic leukemia (T-ALL). In each of the 18 T-ALL cases as well as JK-E6-1 and MOLT-3 cell lines, we found high-level expression of dominant-negative isoforms of Ikaros with abnormal subcellular compartmentalization patterns. Nuclear extracts from these cells failed to bind to the IKAROS-specific binding sequence in DNA. PCR cloning and sequencing confirmed that JK-E6-1 and MOLT-3 cell lines as well as leukemic cells from 9 of 10 patients with T-ALL expressed dominant-negative Ikaros isoforms Ik-4, Ik-7, and Ik-8 that lack critical NH2-terminal zinc fingers. In 6 of 10 patients, we detected a specific mutation leading to an in-frame deletion of 10 amino acids (delta KSSMPQKFLG) upstream to the transcription activation domain and adjacent to the COOH-terminal zinc fingers of Ik-2, Ik-4, Ik-7, and Ik-8. Thus, children with T-ALL express high levels of dysfunctional dominant-negative Ikaros isoforms.

Expression of dominant-negative and mutant isoforms of the antileukemic transcription factor Ikaros in infant acute lymphoblastic leukemia

Ikaros, a zinc finger-containing DNA-binding protein, is required for normal lymphocyte development, and germline mutant mice that express only non-DNA binding dominant-negative "leukemogenic" Ikaros isoforms lacking critical N-terminal zinc fingers develop an aggressive form of lymphoblastic leukemia 3-6 months after birth. Therefore, we sought to determine whether molecular abnormalities involving the Ikaros gene could contribute to the development of acute lymphoblastic leukemia (ALL) in infants. Primary leukemic cells were freshly obtained from 12 infants (<1 year of age) with newly diagnosed ALL. In leukemic cells from each of the 12 infants with ALL, we found high level expression of dominant-negative isoforms of Ikaros with abnormal subcellular compartmentalization patterns. PCR cloning and nucleotide sequencing were used to identify the specific Ikaros isoforms and detect Ikaros gene mutations in these cells. Leukemic cells from seven of seven infants with ALL, including five of five MLL-AF4(+) infants, expressed dominant-negative Ikaros isoforms Ik-4, Ik-7, and Ik-8 that lack critical N-terminal zinc fingers. In six of seven patients, we detected a specific mutation leading to an in-frame deletion of 10 amino acids (Delta KSSMPQKFLG) upstream of the transcription activation domain adjacent to the C-terminal zinc fingers of Ik-2, Ik-4, Ik-7, and Ik-8. In contrast, only wild-type Ik-1 and Ik-2 isoforms with normal nuclear localization were found in normal infant bone marrow cells and infant thymocytes. These results implicate the expression of dominant-negative Ikaros isoforms and the disruption of normal Ikaros function in the leukemogenesis of ALL in infants.

Prognostic significance of the CD10+CD19+CD34+ B-progenitor immunophenotype in children with acute lymphoblastic leukemia: a report from the Children's Cancer Group

Leukemic cells from most patients with B-lineage acute lymphoblastic leukemia (ALL) appear to originate from normal B-lymphocyte precursors. The earliest B-cell progenitors coexpress the antigens CD10, CD19, or CD34 on their cell surfaces. In a large cohort of 2028 children with ALL, we compared treatment outcomes of a subset of B-lineage ALL patients with CD10+CD19+CD34+ immature B-progenitor leukemia (BPL) to the treatment outcomes of the remaining CD19+ B-lineage ALL patients. Pediatric B-lineage ALL cases enrolled on risk-adjusted ALL treatment protocols of the Children's Cancer Group were immunophenotypically classified as BPL or non-BPL. Patients were stratified further into age groups of > or = 1 year and <12 months. Event-free survival (EFS) outcomes were calculated by standard life table methods. BPL patients in both age groups generally had more favorable presenting characteristics than non-BPL controls. Within the age group of > or = 1 year, BPL patients had a slightly better EFS outcome than non-BPL patients, with 3-year estimates of 83.9% (SD = 1.1%) vs. 78.8% (SD = 1.8%), respectively (P = 0.10). Infants with BPL, representing one-fifth of the total infant patient population, had a significantly better EFS outcome than infants with non-BPL (three-year EFS: 82.4%, SD = 9.2% vs. 34.4%, SD = 5.9%, P = 0.006). In univariate analyses, the relative hazard rate (RHR) was 3.73 for non-BPL vs BPL and this marked difference in EFS outcome was maintained at 5 years of follow-up. The favorable prognostic influence of the BPL immunophenotype for infants remained significant in multivariate analyses with an RHR of 2.72 for non-BPL vs BPL (P = 0.05). CD10+CD19+CD34+ immature B-progenitor immunophenotype is associated with favorable characteristics for children with ALL and identifies a subset of infants who achieve favorable EFS outcomes.

Heparin decreases the degradation rate of hepatic lipase in Fu5AH rat hepatoma cells. A model for hepatic lipase efflux from hepatocytes

The mechanism for the stimulation of hepatic lipase secretion by heparin was studied in cultured Fu5AH rat hepatoma cells. Quantitative immunoprecipitation followed by electrophoresis and fluorography were used to isolate and quantitate the radioactive enzyme; hepatic lipase protein mass was quantitated by ELISA. Addition of heparin to the medium resulted in a 2-fold increase in lipase secretion rate, whereas cell-surface-associated and intracellular lipase decreased by 76 and 20%, respectively. Rates of synthesis of hepatic lipase measured by incorporation of Trans 35S-label into enzyme protein were not different in control or heparin-treated dishes. In pulse-chase studies, it was estimated that the degradation rate constants for control and heparin-treated cultures were 0.51 +/- 0.09 and 0.14 +/- 0.13 h-1 for control and heparin-treated cultures, respectively. 52% of the synthesized enzyme was degraded in control cultures; addition of heparin to the culture medium reduced this figure to 11% of the synthetic rate. Equilibrium binding data of highly purified 125I-hepatic lipase to Fu5AH cells at 4 degrees C demonstrate the presence of a class of high-affinity binding sites. At 37 degrees C, cell-surface-bound 125I-hepatic lipase is internalized and either degraded or recycled to the medium. The half-intracellular residence times of hepatic lipase were 55 and 31 min in control and heparin-treated cultures, respectively. Radioactivity incorporated in the 55.4 kDa high-mannose-containing lipase and the mature 57.6 kDa species was measured as a means of locating the enzyme in the secretory pathway before or beyond the medial Golgi. The disappearance of the 55.4 kDa species from the cell is similar in control and heparin-treated cultures with half-intracellular residence times of 29 and 25 min, respectively. In contrast, the amount of radiolabeled 57.6 kDa species in control cells remained constant from 15 min to 2 h, whereas it decreased by 79% in heparin-treated cells. The above data demonstrate that the increase in hepatic lipase secretion is due to a decreased degradation rate with no change in synthetic rate and that heparin primarily affected the residence time of hepatic lipase in the medial Golgi-plasma membrane region.