Close correlation between the magnetic moments, lattice distortions, and hybridization in LaMnO3 and La(1-x)Sr(x)MnO3+delta: doping-dependent magnetic circular X-ray dichroism study.

The first observation of a magnetic circular x-ray dichroism (MCXD) at the Mn L2,3 core edges in antiferromagnetic LaMnO3 shows canted spin and orbital ( m(orb)) moments arising from lattice distortions. An L2,3-edge MCXD in ferromagnetic metals and insulators, La1-xSr(x)MnO3+delta, reveals that m(orb) of Mn strongly depends on x in the metallic regime but remains unchanged with the metal-to-insulator transition (x approximately 0.16). An O K-edge MCXD, which shows m(orb) of O caused by 2p-3d hybridization, is much larger in the ferromagnetic metal than insulator phases, sharply contrasting with m(orb) of Mn. Our findings indicate a close magnetism-lattice-hybridization coupling.

Direct determination of interfacial magnetic moments with a magnetic phase transition in Co nanoclusters on Au(111).

The spin, in-plane and out-of-plane orbital and magnetic dipole moments of almost purely interfacial Co atoms were directly determined for Au/2-monolayer Co nanoclusters/Au(111) by angle-dependent magnetic circular x-ray dichroism (MCXD) measurements. The field- and temperature-dependent MCXD evidences a ferromagnetic(FM)-to-superparamagnetic phase transition in single-domain clusters with decreasing size. The interfacial moments are remarkably enhanced as compared with bulk values, verifying theoretical predictions. The FM clusters show strong perpendicular magnetic anisotropy, providing promise of applications for nanoscale magnetic bits.

Good prognosis of patients with acute promyelocytic leukemia who achieved second complete remission (CR) with a new retinoid, Am80, after relapse from CR induced by all-trans-retinoic acid.

A new synthetic retinoid, Am80, is effective in treating acute promyelocytic leukemia relapsed from all-trans-retinoic acid-induced complete remission (CR). We report here the long-term clinical outcomes of patients who achieved second CR with Am80. Of 24 evaluable patients, 14 achieved a second CR by Am80 therapy. Of those patients, 4 relapsed within 6 months, despite subsequent consolidation chemotherapy. Six patients underwent sibling or unrelated HLA-matched allogeneic bone marrow transplantation (BMT), and 4 are alive without relase for more than 49 months after achieving second CR. Four of 8 patients who did not receive BMT are alive without relapse for more than 49 months. Promyelocytic leukemia-retinoic acid receptor alpha (PML-RAR alpha) fusion transcript was undetectable by reverse transcriptase-polymerase chain reaction in all living patients. Therefore, if patients achieve second CR with Am80 and HLA-matched donors are available, BMT is the treatment of choice. However, it is noteworthy that CR was maintained for more than 49 months in half of the patients who did not receive BMT.

A compact molecular-beam epitaxy apparatus for in situ soft X-ray magnetic circular dichroism experiments.

An economical and easily movable molecular-beam epitaxy (MBE) apparatus which prepares magnetic ultrathin films and superlattices with atomically well controlled interfaces has been designed and constructed. Cleaning and characterization of substrates, sample deposition in a layer-by-layer fashion, and characterization of samples both during and after growth can be carried out in a single ultrahigh vacuum (UHV) chamber. This MBE apparatus is combined with UHV high-field magneto-optical instruments for in situ soft X-ray magnetic circular dichroism experiments on two-dimensional magnetic systems.

Different T-cell receptor repertoires between lesions and peripheral blood in acute graft-versus-host disease after allogeneic bone marrow transplantation.

From the viewpoint of T-cell receptor (TCR) repertoire, we studied the role of T cells in acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (allo-BMT) from an HLA-identical sibling. By means of inverse polymerase chain reaction method and DNA sequencing, we analyzed TCR-alpha and -beta transcripts from GVHD lesions and peripheral blood (PB) in a patient with typical GVHD together with PB from donor. At the initial onset of GVHD, V alpha-7 and -19 subfamilies were oligoclonally expanded in the PB compared with those in the oral mucosal lesions. At the second onset, V alpha-2, and V beta-6 subfamilies were more frequently detected in the cutaneous lesion than in the PB. Some TCR transcripts were recurrently found either in the mucosal or cutaneous lesions (or in both) and not in the PB. Furthermore, some of recurrent TCR transcripts in the lesions shared V gene segments and common motifs of complementarity determining region-3. These findings suggested that T cells infiltrating the GVHD lesions recognized a limited kind of antigens presented by patient's tissues with GVHD, and that T-cell repertoire in the GVHD lesions was different from that in the PB.

Isoforms of PML-retinoic acid receptor alpha fused transcripts affect neither clinical features of acute promyelocytic leukemia nor prognosis after treatment with all-trans retinoic acid. The Leukemia Study Group of the Ministry of Health and Welfare (Kohseisho).

All-trans retinoic acid (ATRA) has been used as a potent differentiation drug for acute promyelocytic leukemia (APL). Although the mechanism of its effectiveness upon APL remains unclear, the PML-retinoic acid receptor alpha (RARA) chimeric protein produced by t(15;17) is assumed to underlie the sensitivity of APL cells to ATRA. There are two major isoforms of PML-RARA transcripts; short (S) and long (L), according to the breakpoints in the PML gene. We therefore compared the clinical variables, the response to ATRA and the prognosis between 28 patients with type S and 68 patients with type L. Patients were treated in multi-institutional trials with ATRA, and chemotherapy was combined when peripheral blasts and leukocyte counts increased during the therapy. The clinical features at diagnosis were similar between the two molecular subtypes, and there was no significant difference in remission induction rates; 86% for the type S group and 90% for the type L group. There was no statistical difference in overall survival and CR duration as well as disease-free survival (DFS). In newly diagnosed patients, predicted 2-year DFS was 66% for the type S group and 67% for the type L group. In refractory or relapsed patients, it was 19 and 23%, respectively. These data indicated that isoforms of PML-RARA fused transcripts affect neither the clinical features of APL nor the prognosis after treatment with ATRA.

Prognostic significance of the RT-PCR assay of PML-RARA transcripts in acute promyelocytic leukemia. The Leukemia Study Group of the Ministry of Health and Welfare (Kouseisho).

Minimal residual disease (MRD) was prospectively monitored at the 10(-5) level by the reverse transcriptase-polymerase chain reaction (RT-PCR) of PML-retinoic acid receptor alpha (RARA) transcripts from 27 acute promyelocytic leukemia (APL) patients who achieved complete remission (CR) with all-trans retinoic acid and chemotherapy (previously untreated patients, 15; refractory to chemotherapy or relapsed, 12). The RNA quality from bone marrow cells was firstly assessed by gel electrophoresis to avoid false negativity because of the fragility of the APL cells and the PML-RARA transcripts. In 12 of 15 untreated patients, RT-PCR became negative during consolidation and intensification therapy 4-16 months after the initiation of therapy, whereas it remained positive in nine of 12 refractory patients. At the end of therapy, RT-PCR was negative in 14 patients and positive in 13 patients. The former patients remained in CR at median follow-up of 9 months after the end of therapy. In the latter, however, 10 patients relapsed at a median of 5 months after the end of therapy. These results suggest that the RT-PCR assay can evaluate the quality of CR in APL and predict subsequent relapse.

Continuing immunoglobulin heavy chain gene rearrangements in chronic myeloid leukemia with recurrent B-lymphoid blast crises after bone marrow transplantation.

We sequentially analyzed the immunoglobulin heavy chain variable (IgH V) region gene of leukemia cells obtained from a chronic myeloid leukemia (CML) patient who had three episodes of B-lymphoid crisis after bone marrow transplantation. Southern blot analysis using the JH probe showed different rearranged bands at each crisis, although the same rearranged bands of the BCR gene were observed. We amplified and sequenced the IgH V region gene of the leukemia cells by reverse transcriptase polymerase chain reaction (RT-PCR) using the primers corresponding to the consensus 5'VH and mu constant regions. The dominant leukemia clone at each crisis had a unique VH-D-JH rearrangement; VH4A (V79)-DLR2-J5 (clone-1), VH4B (DP70)-DK4-J6 (clone-2) and VH4A (V79)-DN4-J6 (clone-3) at the first, second and third crises, respectively. Further analysis by PCR amplification using the consensus 5'VH and clone-specific primers revealed that clone-1 underwent VH4-->VH3 replacement at the second crisis, and that clone-3 was already in existence at the first crisis. Moreover, the DN4-J6 joining clone, in which the sequence was the same as that of clone-3, was identified at the first and third crises by PCR amplification using primers corresponding to the region upstream of the DN4 segment and DN4-J6 boundary of clone-3. These observations suggest that multiple clones were generated from the progenitor cells of blast crisis, which were transformed at a very early stage of B-lymphocyte ontogeny, by continuing rearrangement mechanisms of the IgH genes, and that the dominant clone at each crisis was undergoing change.

Analysis of the joining sequences of the t(15;17) translocation in human acute promyelocytic leukemia: sequence non-specific recombination between the PML and RARA genes within identical short stretches.

Molecular analysis of the t(15;17) translocation in 70 patients with acute promyelocytic leukemia (APL) confirmed that the breakpoints of chromosome 15 were located in two regions of the promyelocytic leukemia (PML) gene, mainly introns 3 and 6, whereas the breakpoints of chromosome 17 were consistently in intron 2 of the retinoic acid receptor alpha (RARA) gene. To study the reason for the clustering of the breakpoints and the underlying mechanism of the chromosomal translocation, we characterized the joining sequences of der(15) and der (17) by polymerase chain reaction in samples from eight patients with APL. There was no cluster of the breakpoints within the introns, and no consensus sequence-motif was found around them. One or nine extra nucleotides were inserted into two joining sites. There were identical stretches of one to seven nucleotides between the PML and RARA genes in the majority of the joining sequences. These data provide a potential model of the t(15;17) translocation: random DNA double strand cleavage, modification of DNA ends by enzymes including terminal deoxynucleotidyl transferase, and single strand base-pairing within identical short stretches. Furthermore, APL develops only when the PML and RARA genes are rearranged, within restricted genomic regions and a functional PML-RARA chimeric product is produced, and this might lead to a clustering of the breakpoints.

Characterization of immunoglobulin heavy chain gene rearrangements in chronic myeloid leukemia with recurrent B-lymphoid blast crisis following bone marrow transplantation.

We sequentially analyzed the immunoglobulin heavy chain (IgH) variable region gene of leukemia cells obtained from a chronic myeloid leukemia (CML) patient who had three episodes of B-lymphoid crisis after bone marrow transplantation. Southern blots using the JH probe showed a single rearranged band which differed at each crisis, although the rearranged bands of the BCR gene were the same at each crisis. The IgH variable region sequences of the leukemia cells at each crisis were different. These observations suggested that multiple clones were generated from the progenitor cells of the blast crisis, which were transformed at a very early stage of B-lymphocyte ontogeny.

Bernard-Soulier syndrome Kagoshima: Ser 444-->stop mutation of glycoprotein (GP) Ib alpha resulting in circulating truncated GPIb alpha and surface expression of GPIb beta and GPIX.

The platelet membrane glycoprotein (GP)Ib/IX complex is composed of three polypeptides, GPIb alpha, GPIb beta, and GPIX, and functions as a platelet receptor for von Willebrand factor. All three subunits are reported to be requisite for efficient surface expression of the complex. The absence of the GPIb/IX complex on platelet membrane is the hallmark of a congenital qualitative platelet disorder, termed the Bernard-Soulier syndrome (BSS). We describe here the molecular basis of a novel variant phenotype of BSS in a female patient, designated as BSS Kagoshima. Her platelets completely lacked the surface expression of GPIb alpha, but expressed a residual amount of GPIb beta and GPIX. Unexpectedly, her platelets and plasma contained a truncated GPIb alpha polypeptide with an apparent molecular weight of 116 kD (under nonreducing conditions). The amounts of truncated protein were 23% and 60% of the normal values in platelets and plasma, respectively. The abnormal protein contained a normal amount of sialic acid as demonstrated by digestion with neuraminidase. DNA sequencing analysis showed a homozygous single nucleotide substitution from the serine codon (TCA) to a nonsense codon (TAA) at residue 444 in the GPIb alpha gene. The mutant gene generated a truncated GPIb alpha molecule lacking the transmembrane region and cytoplasmic tail. Her parents were heterozygotes for the mutation. These findings suggest that this type of truncated GPIb alpha was produced, normally glycosylated, and subsequently secreted into the plasma. Furthermore, the truncated GPIb alpha might be associated with the process of the surface expression of incomplete GPIb/IX complex, GPIb beta and GPIX.

[New strategy for diagnosis and treatment of acute promyelocytic leukemia with t (15;17)].

All-trans retinoic acid (ATRA)-therapy against acute promyelocytic leukemia (APL) is epoch-making in the sense of the first success in both tumor-differentiation therapy and molecule-targeted therapy. Kouseishou APL-study group performed three clinical studies to refractory APL with ATRA from 1990 to 1993. Complete remission (CR) was obtained in 82%, 88% and 78% of 22, 41 and 46 patients, respectively. Molecular diagnosis of the t (15;17) translocation was possible using Southern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR).

Multi-institutional study of all-trans-retinoic acid as a differentiation therapy of refractory acute promyelocytic leukemia. Leukaemia Study Group of the Ministry of Health and Welfare.

We treated 70 acute promyelocytic leukemia (APL) patients with daily oral 45 mg/m2 all-trans-retinoic acid (ATRA) in two multi-institutional prospective studies. Of 64 evaluable patients, 21 were refractory to initial induction chemotherapy; 10 were refractory to salvage chemotherapy; 17, five, and four were in the first, second and, third relapse, respectively; and seven were previously untreated due to old age. In the first study with ATRA from China, 18 out of 22 (82%) evaluable patients achieved complete remission (CR). Initial peripheral leukemia cell counts were significantly less in the CR cases (p < 0.01); < 100/microliters in 17 out of 18 CR cases, and > or = 200/microliters in all failure cases. In the second study with ATRA from Hoffmann-La Roche, if initial leukemia cell counts were more than 200/microliters, chemotherapy was first given and then ATRA was started. Of 42 evaluable patients, 36 (86%) achieved CR. Morphological evidence of differentiation was noted in all CR cases. Patients achieving CR received standard consolidation and maintenance chemotherapies, and the 20-month predicted disease-free survival rate is 76% for cases achieving their first CR with ATRA. Toxicities attributable to ATRA were minimal and included cheilitis, xerosis, dermatitis, gastrointestinal disorders, bone pain, liver damage, and high serum triglyceridemia.

[Differentiation therapy of acute promyelocytic leukemia with all-trans retinoic acid].

We treated 70 patients with acute promyelocytic leukemia (APL) with daily oral 45 mg/m2 all-trans retinoic acid (ATRA) in 2 multi-institutional prospective studies. Of 63 evaluable patients, 21 were resistant to initial induction chemotherapy, 10 were resistant to salvage chemotherapy after relapse, 17 were in the first relapse, 4 in the second relapse, 4 in the third relapse, and 7 were previously untreated. In the first study with ATRA from China, 18 (82%) of 22 evaluable patients achieved CR within 8 to 53 days with a median of 29 days. Initial peripheral leukemia cell counts were significantly less in the CR cases (p < 0.01). They were less than 100/mm3 in 17 of 18 CR cases, and more than 200/mm3 in all failure cases. Patients achieving CR received standard consolidation and maintenance chemotherapies, and the 16-month predicted continuing CR rate is 60%. Based on the first study, in the second study with ATRA from Hoffmann-La Roche AG, if initial peripheral leukemia cell counts were more than 200/mm3, chemotherapy was first given and then ATRA was started. Of 41 evaluable patients, 36 (88%) achieved CR within 11 to 91 days with a median of 34 days. Of 3 patients who received preceding chemotherapy due to high leukemia cell counts, 2 achieved CR. Morphological evidence of differentiation was noted in all CR cases, with Auer rods in mature segmented neutrophils in 13 cases. The clinical signs of DIC decreased rapidly within a few days and disappeared in CR cases. Toxicities attributable to ATRA were minimal and included cheilitis, xerosis, dermatitis, gastrointestinal disorders, bone pain, liver damage and high serum triglyceridemia.

Clonal analysis of multiple point mutations in the N-ras gene in patients with acute myeloid leukemia.

We have screened mutations of the N-ras gene at codons 12, 13, and 61 in leukemia cells obtained from 100 patients with acute myeloid leukemia (AML), and found mutated N-ras alleles in 9 patients. We further analyzed the polyclonality of multiple N-ras gene mutations in 4 AML patients. One patient, who had the monoclonal karyotype, t(11;17), had two types of double missense mutations at codons 13 and 61 in the same allele. Each of the remaining three patients, one of whom had t(15;17) with a monoclonal rearrangement of the retinoic acid receptor alpha and PML genes, carried two missense mutations in a relatively small population of leukemia cells. We have demonstrated that multiple clonality of the N-ras gene is occasionally observed in leukemia with a monoclonal karyotype. These findings indicate that the N-ras mutations may not always be characterized simply by an accumulative process and that the activated N-ras gene alone is not sufficient to cause leukemia.

Molecular heterogeneity of the PML gene rearrangement in acute promyelocytic leukemia: prevalence and clinical significance.

We determined the breakpoints of the RAR-alpha and PML genes in acute promyelocytic leukemia (APL) cells from 40 patients using Southern blot analysis. We also analyzed the relationship between the location of breakpoints, the clinical features of APL and the response to all-trans retinoic acid (ATRA). While the breakpoints of the RAR-alpha gene were consistently within intron 2, we found two major clusters in the breakpoints of the PML gene. The two breakpoint clusters in the PML gene were separated by 10 kb; 5' breakpoints were in intron 3, and 3' breakpoints were around introns 5 and 6. Twenty percent of the patients had 5' breakpoints in the PML gene and 70% had 3' breakpoints. No rearrangement was observed in the remaining 10% of patients in spite of the presence of t(15;17) translocation. There was no relationship between the location of the PML breakpoints, the clinical features at diagnosis and the response to ATRA.