A phase I/II study of recombinant interferon alpha 2a and hydroxyurea for chronic myelocytic leukemia

Nine previously untreated patients with Philadelphia chromosome-positive chronic myelocytic leukemia (CML) were treated with recombinant interferon alpha 2a (rIFN-alpha 2a) and hydroxyurea. Patients received 6 X 10(6) U rIFN-alpha 2a daily for the first week and 3 X 10(6) U rIFN-alpha 2a daily for the second week. As maintenance treatment starting on day 15, patients received 3 X 10(6) U rIFN-alpha 2a 3 times a week. Simultaneously, hydroxyurea was given, starting at a dose of 40 mg/kg on day one. The maintenance dosage was adjusted to the white blood cell count. Two patients responded with complete hematological remissions but without cytogenetic and molecular-genetic improvements. Seven patients responded with partial hematological remissions. Response to therapy was rapid; normal white blood cell counts were reached after a median of 12 days. The doses of rIFN-alpha 2a and hydroxyurea needed to keep the leucocyte count in the normal range were low (3 X 10(6) U rIFN-alpha 2a 3 times per week, 0.5-1.5 g hydroxyurea/day). Acute toxicity of the combination therapy consisted of fever (9 of 9 patients), flulike symptoms (7 of 9 patients), pruritus and/or rash (3 of 9 patients) and evidence of a tumor cell lysis syndrome (1 of 9 patients). The side effects were not dose-limiting. Combination therapy with rIFN-alpha 2a and hydroxyurea for CML is well tolerated and allows quick and effective hematological control of the disease.     

The spectrum of CFTR mutations in south-west German cystic fibrosis patients

The cystic fibrosis transmembrane conductance regulator (CFTR) gene of 110 cystic fibrosis (CF) patients from the south-west of Germany was screened for 12 different mutations. This analysis resulted in an identification of 79% of all CF mutations and a complete genotype in 66% of the families. The most common mutation found was F508 (67%). Another 5 mutations accounted for a further 12.5% (4% G542X; 3% R553X; 3% N1303K; 2% 1717-1 GA; 0.5% G551D) whereas 6 mutations (R117H, A455E, I507, S549I, S549N, and R1162X) were not found. Fifty-four (49%) patients were AF508 homozygotes and 18 (16.5%) were compound heterozygotes for F508 and one of the rarer mutations. These frequencies differ slightly from those found in the north of Germany and considerably from those reported from the south of Europe, which seems to be consistent with a north to south decline of the relative abundance of F508. Two patients, age 6 and 25 years, were compound heterozygotes for G542X and N1303K. The clinical features of the 6 year old were characterised by severe gastrointestinal and as yet only mild pulmonary complications whereas the 25 year old manifested severe pulmonary and gastrointestinal symptoms indicating that the N1303K mutation of the C-terminal CFTR nucleotide binding fold significantly impairs protein function in both the pancreas and the lungs.     

Fc receptors on mouse effector cells mediating natural cytotoxicity against tumor cells.

Mouse effector cells mediating natural cytotoxicity against tumor cells have been previously thought to be lymphocytes that lack any detectable cell surface markers. The present study presents evidence for receptors for the Fc portion of IgG on these cells. By adsorption of cytotoxic spleen cells on monolayers of sheep erythrocytes (E) plus IgG antibodies to sheep erythrocytes (EA), 50 to 96% of the total cytotoxic reactivity could be removed. Parallel adsorption of cells on E monolayers or on EA monolayers coated with protein A, to block the Fc portion of IgG, resulted in little or no depletion of cytotoxic activity. The presence of Fc receptors on the NK cells was confirmed by combining EA rosette formation with velocity sedimentation at unit gravity. Peak cytotoxicity occurred at the same sedimentation velocity as the peak of Fc-positive cells. After EA rosette formation, there was a shift to a higher sedimentation velocity in the Fc-positive cells and in the natural cytotoxic activity. The increase in sedimentation velocity of NK activity that was observed in these experiments indicated that most of the cells had only bound a small number (three or four) of antibody-coated erythrocytes. Together, these data indicate that cells with Fc receptors account for most of the total lytic activity of normal mouse spleen cells.     

Mutagen-induced sister chromatid exchange rate in Bloom syndrome remains unaltered in the presence of Bloom corrective factor

Summary Fibroblasts of a patient with Bloom syndrome (GM-1492) were cultured in the presence of either mitomycin C, ethylmethanesulfonate, or 4-nitroquinoline-1-oxide, (4-NQ1-O) and sister chromatid exchange was determined. The mutagens enhanced the sister chromatid exchange rate to different degrees, 4-NQ1-O being the most potent substance. Bloom corrective factor, which is present in normal cell-conditioned culture medium, reduced the spontaneously increased SCE in Bloom syndrome cells by about 20 SCE per metaphase but failed to reduce the additional mutagen-induced SCE increase. These findings indicate that only spontaneously, but not mutagen-indeuced, SCE in Bloom syndrome fibroblasts can be decreased by the Bloom corrective factor.     

FLT3 Mutations in Early T-Cell Precursor ALL Characterize a Stem Cell Like Leukemia and Imply the Clinical Use of Tyrosine Kinase Inhibitors

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) has been identified as high-risk subgroup of acute T-lymphoblastic leukemia (T-ALL) with a high rate of FLT3-mutations in adults. To unravel the underlying pathomechanisms and the clinical course we assessed molecular alterations and clinical characteristics in a large cohort of ETP-ALL (n = 68) in comparison to non-ETP T-ALL adult patients. Interestingly, we found a high rate of FLT3-mutations in ETP-ALL samples (n = 24, 35%). Furthermore, FLT3 mutated ETP-ALL was characterized by a specific immunophenotype (CD2+/CD5-/CD13+/CD33-), a distinct gene expression pattern (aberrant expression of IGFBP7, WT1, GATA3) and mutational status (absence of NOTCH1 mutations and a low frequency, 21%, of clonal TCR rearrangements). The observed low GATA3 expression and high WT1 expression in combination with lack of NOTCH1 mutations and a low rate of TCR rearrangements point to a leukemic transformation at the pluripotent prothymocyte stage in FLT3 mutated ETP-ALL. The clinical outcome in ETP-ALL patients was poor, but encouraging in those patients with allogeneic stem cell transplantation (3-year OS: 74%). To further explore the efficacy of targeted therapies, we demonstrate that T-ALL cell lines transfected with FLT3 expression constructs were particularly sensitive to tyrosine kinase inhibitors. In conclusion, FLT3 mutated ETP-ALL defines a molecular distinct stem cell like leukemic subtype. These data warrant clinical studies with the implementation of FLT3 inhibitors in addition to early allogeneic stem cell transplantation for this high risk subgroup.     

Identification of a novel putative Ran-binding protein and its close homologue

In the process of cloning genes at the breakpoint of t(5;14) (q34;q11), a recurring translocation in acute lymphoblastic leukemia, we isolated and characterized a novel gene at 5q34, and a close human homologue (66% amino acid identity) located at 8p11-12. The presence of an importin-beta N-terminal domain at their N-terminus, their size of approximately 110 kD, their nuclear localization and the identity of the homologue to a gene of a recently submitted RanGTP binding protein (RanBP16), suggest that its protein is a novel member of the importin-beta superfamily of nuclear transport receptors, therefore called RanBP17. Northern blot analysis of human tissues revealed a ubiquitous expression pattern of the RanBP16 gene and a very restricted expression pattern of the RanBP17 gene, showing high expression in testis and pancreas. Both genes are evolutionary conserved and show a high (99 and 94%) amino acid conservation with their murine counterparts and a striking similarity (40%) to a protein product of Caenorhabditis elegans (C35A5.8).