Tetsuaki Sekikawa

Interferon modulates the messenger RNA of G1-controlling genes to suppress the G1-to-S transition in Daudi cells

Interferon (IFN) is one of the potent antiproliferative cytokines and is used to treat some selected cancers. IFN arrests the growth of Burkitt Iymphoma derived cell line Daudi cells in the G1 phase. G1-to-S progression is controlled by positive and negative regulatory genes. Therefore, we investigated the effects of IFN on G1-controlling genes. Expression of cyclin-dependent kinases (Cdks 2, 3, 4, 5, 6), MO 15/Cdk7, and cyclins E and H was studied to assess positive regulators, while p15Ink4B, p16Ink4, p18, p21CipI, and p27Kip1 were assessed as negative regulators. Cdks 2, 4, 6 and cyclin E were markedly down-regulated. MO15/Cdk7 expression showed little change, but its regulatory subunit (cyclin H) was down-regulated like cyclin E. Expression of p15Ink4B and p16Ink4 was not observed. p18 was induced until 48 h and its expression returned to the initial level at 72 h. In contrast, p21Cip1 mRNA expression remained at the baseline level throughout IFN treatment, while the expression of p27Kip1 increased at 48 and 72 h. Taken together, these data indicate that IFN changes the messenger RNA of G1-controlling genes towards the suppression of G1-to-S transition.

Both NUP98/TOP1 and TOP1/NUP98 transcripts are detected in a de novo AML with t(11;20)(p15;q11).

The NUP98 gene is involved in several chromosomal abnormalities associated with acute leukemia. The recurrent t(11;20)(p15;q11) chromosomal translocation results in generation of the NUP98/TOP1 chimeric gene. This abnormality has been observed primarily in therapy‐related leukemias, and TOP1/NUP98 transcripts have not been demonstrated. We describe a case of de novo acute myeloid leukemia with t(11;20)(p15;q11), with no known history of exposure to chemicals. The translocation occurred in intron 13 of NUP98 and intron 7 of TOP1, as in the three previously reported cases. The breakpoint in NUP98 was exactly the same as that found in a previously reported case. In addition, a reciprocal TOP1/NUP98 transcript was detected for the first time in our patient.

Band 3 Tokyo: Thr837-->Ala837 Substitution in Erythrocyte Band 3 Protein Associated with Spherocytic Hemolysis

We report a case of spherocytosis associated with erythrocyte band 3 deficiency. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of erythrocyte membrane proteins showed that the patient’s band 3 was reduced to about 80% of the control level. Molecular analysis revealed that this quantitative alteration was accompanied by a novel base change at codon 837 (ACG→GCG) of the AE1 gene, resulting in substitution of alanine for threonine. In bone marrow mononuclear cells, both mutant and wild-type mRNA were comparably detected, suggesting that this mutation interfered with band 3 processing or assembly, leading to impaired accumulation of mutant band 3 in the plasma membrane.

Diffuse large B‐cell lymphoma arising independently to lymphoplasmacytic lymphoma: a case of two lymphomas

Richters syndrome occurs in 5–10% of patients with chronic lymphocytic leukemia, either by transformation of the primary neoplastic lymphocyte, or as a distinct B‐cell neoplasm. We report a Japanese patient with lymphoplasmacytic lymphoma in whom a diffuse large B‐cell lymphoma developed after treatment with rituximab. Molecular examination on immunoglobulin VH genes revealed that the lymphomas had arisen in two separate clones. We reviewed clinical case reports in literature, and found 30–40% of cases with Richters syndrome and composite lymphoma had a second B‐cell lymphoma of a different origin.

Biological effects of a relatively low concentration of 1-beta-D-arabinofuranosylcytosine in K562 cells: alterations of the cell cycle, erythroid-differentiation, and apoptosis.

Therapeutic strategies for leukemia are directed to induction of differentiation and apoptosis as well as growth inhibition. One of the key antileukemic agents, 1-β-D-arabinofuranosylcytosine (ara C), is clinically applied according to these therapeutic aims. However, the molecular effects of 0.1 μg/ml of ara C, a concentration that corresponds to the serum level in leukemic patients on a conventional dose of ara C, have not been well disclosed. Here, we addressed these issues using K562 cells which derived from a blastic crisis of chronic myeloid leukemia. DNA synthesis of treated cells was suppressed from 1-6 h. But, it recovered at 12 h and no further inhibition was observed. The number of cells was not decreased but DNA fragmentation was observed at 72 h. The number of erythroid-differentiated cells also increased to 30% at 72 h. Along with treatment, no marked alteration of mRNAs for cell cycle-regulating genes was found and the retinoblastoma gene product remained hyperphosphorylated throughout treatment. The expression of mRNAs for apoptosis-regulating genes also remained unchanged, except for slight down-regulation of Bax. c-myc protein was not found later than 48 h, and Max mRNA was downregulated. c-jun was immediately induced, followed by the fluctuated expression level along with treatment. These findings suggest that the 0.1 μg/ml ara C changed the proliferation, differentiation and death of K562 cells in a biphasic manner. In the early phase, DNA synthesis was inhibited without altering the expression of cell cycle regulating-genes. In the latter phase, cell death and erythroid- differentiation occurred in accordance with the down-regulation of c-myc.

No V H Somatic Hypermutation Was Detected in B-Cells of a Patient with Macroglobulinemia Due to Splenic Marginal Zone Lymphoma

B-cell diseases are classified on the basis of the normal differentiation stages. We report here a case of a patient with a long history of leukocytosis, splenomegaly without lymphadenopathy, and hyperviscosity symptoms. Clinically, the patient’s diagnosis was leukemic Waldenström macroglobulinemia. Chromosomal analysis revealed translocation t(2;7)(p11;q22) along with disease progression. Death occurred from pulmonary infection at 46 months after the initial presentation. At autopsy, malignant lymphocytes were found in the marginal areas of the spleen with spreading to the bone marrow and the liver. The histologic findings were consistent with splenic marginal zone lymphoma. We examined the sequences of the immunoglobulin VH gene in cells from the initial peripheral blood and from the spleen at autopsy and found that the sequences were identical and had no somatic hypermutation. Macroglobulinemia can occur in various B-cell disorders, including splenic marginal zone lymphoma, even with the transformation of unmutated B-lymphocytes. Int J Hematol. 2002;76:453-459.