Kazuaki Ishibashi

Expression of the multidrug transporter, P-glycoprotein, in acute leukemia cells and correlation to clinical drug resistance

The overexpression of a cell‐surface glycoprotein termed P‐glycoprotein (P‐gp) is frequently associated with multi‐drug resistance (MDR) in cell lines in vitro. To evaluate the implications of P‐gp expression in clinical drug resistance, the authors examined the expression of P‐gp in leukemia cells from patients with acute myelogenous leukemia (AML) and those with acute lymphoblastic leukemia (ALL) at initial presentation and relapse, using immunoblotting with a monoclonal antibody against P‐gp, C219. Nine of 17 patients with AML and four of 11 patients with ALL had P‐gp‐positive results at the initial presentation, and most P‐gp‐positive patients did not respond to chemotherapy. Four of seven patients at the relapsed stage and all three patients with preceding myelodysplastic syndrome had P‐gp‐positive results. The expression of P‐gp and clinical refractoriness to chemotherapy were highly correlated. These data indicate that the expression of P‐gp is closely related to clinical drug resistance in acute leukemia.

Inhibition by arsenic trioxide of human hepatoma cell growth

Arsenic trioxide (As(2)O(3)) has been shown to be effective for treatment of patients with refractory or relapsed acute promyelocytic leukemia and a variety of other malignant hematopoetic disorders. We studied the effect of this agent on proliferation of human hepatoma-derived cell lines (SK-Hep-1, HepG2, and HuH7). In HuH7 cells, As(2)O(3) reduced proliferation time- and dose-dependently at 1 and 2 microM, while in SK-Hep-1 and HepG2 cells, As(2)O(3) inhibited proliferation at 2 and 4 microM respectively. Cell cycle analysis by flow cytometry showed that As(2)O(3) induced apoptosis in these hepatoma-derived cells as confirmed by appearance of sub-G(1) cells. Sensitivity of hepatoma-derived cells to As(2)O(3) was inversely related to their intracellular glutathione (GSH) and intensity of GSH synthesis. Arsenic sensitivity was restored to relatively resistant cell lines when GSH was depleted by L-buthionine sulfoximine (BSO). These results indicate that As(2)O(3) may have therapeutic potential for treatment of hepatocellular carcinoma.

The prevalence of human T-cell leukemia virus type I infection in patients with hematologic and nonhematologic diseases in an adult T-cell leukemia-endemic area of Japan

In order to clarify the prevalence of human T‐cell leukemia virus type I (HTLV‐I) infection in the Kagoshima district, Japan, a highly endemic area for HTLV‐I, antibodies for HTLV‐I (anti‐HTLV‐I) were examined in the sera of 6167 from healthy residents and patients with various hematologic and nonhematologic diseases. In healthy residents, including blood donors, the prevalence of anti‐HTLV‐I was 11.9% (562/4741 persons). The prevalence increased with age, and was significantly higher in females than in males (P < 0.01). The prevalence of anti‐HTLV‐I in blood donors was 8.5%. In hematologic diseases, the prevalence of anti‐HTLV‐I was 98.3% in ATL, 28.9% in lymphoproliferative disorders except ATL, and 10.6% in myeloproliferative disorders. In nonhematologic diseases, the prevalence of anti‐HTLV‐I was shown to be 29.5% in pulmonary tuberculosis, 25.8% in leprosy, 33.8% in chronic renal failure (CRF), 21.9% in autoimmune diseases, and 47.8% in strongyloidiasis. The various diseases except myeloproliferative disorders had significantly higher prevalence of anti‐HTLV‐I than healthy residents (P < 0.01 or 0.05). For autoimmune diseases, the prevalence of anti‐HTLV‐I in patients with blood transfusion (55.6%) was higher than in those without blood transfusion (8.7%), and healthy residents. In hemodialysis patients with CRF who had received blood transfusions the prevalence of anti‐HTLV‐I increased with the number of blood transfusions. Therefore, HTLV‐I transmission via blood transfusion would partially explain these high prevalence of anti‐HTLV‐I. However, the prevalence of anti‐HTLV‐I in hemodialysis patients with CRF was statistically higher than that in healthy residents, regardless of blood transfusion (P < 0.01). Furthermore, hemodialysis patients showed significantly higher prevalence of anti‐HTLV‐I than healthy residents, even at a younger age. Patients with pulmonary tuberculosis and leprosy showed the same results as hemodialysis patients. These results suggest the possibility that HTLV‐I infection has some relation not only to ATL but also to other diseases. Therefore, it seems very important to halt the spread of HTLV‐I transmission as soon as possible.

Tumor Necrosis Factor-β and Hypercalcemia

Hypercalcemia in hematological malignancy is frequently encountered in lymphoid malignancies such as adult T-cell leukemia (ATL) and multiple myeloma and is difficult to manage. As a causative agent of hypercalcemia in ATL, tumor necrosis factor-β (TNF-β), previously known as lymphotoxin, has been carefully studied and reviewed here. Bone resorption studies showed the presence of activity in culture supernatants of HTLV-I infected cells. Enzyme linked immunosorbent assays (ELISA) for TNF-β detected elevated TNF-β in the sera of ATL patients with hypercalcemia. Immunostaining by monoclonal anti-TNF-β antibody demonstrated the presence of TNF-β in both HTLV-I infected cell lines and freshly isolated ATL cells. Furthermore biological TNF-β activity assay including inhibition of anti-TNF-β antibody confirmed the conventional documentation of TNF-β activity in the sera and culture supernatants of HTLV-I infected cell lines. These studies showed that the TNF-β secreted from ATL cells might be one of the factors...

An enzyme-linked immunosorbent assay for immune complex of HTLV-I

A sandwich enzyme-linked immunosorbent assay (ELISA) for immune complexes of human T cell leukemia virus type I (HTLV-I) was developed using monoclonal antibody (MoAb) 3G1 which recognizes a different epitope on HTLV-I to that with which natural human anti-HTLV-I antibody binds. The assay was capable of titrating artificial immune complexes not only at antigen-antibody equivalence but also at antibody excess. Although the antigen-antibody ratios could not be determined in the individual sera from patients with overt ATL, the level of immune complexes in three out of four sera was estimated to be 250 +/- 36 ng/ml. Immune complexes of HTLV-I could not be identified in sera obtained from one patient with overt ATL, three healthy HTLV-I carriers and three normal human controls.

Aspirin induces hepatoma-derived cell apoptosis via a hydrogen peroxide-dependent pathway

Here we studied whether aspirin (ASA) has any influence on viability of human hepatoma-derived SKHep-1 cells and whether hydrogen peroxide (H(2)O(2)) has any relation with this effect. ASA inhibited SKHep-1 cell proliferation dose- and time-dependently. Intracellular H(2)O(2) increased as early as 15 min after ASA supplementation. Cellular apoptosis correlated with an increase in intracellular H(2)O(2) level. Moreover, in the presence of a catalase inhibitor-aminotriazol, ASA showed more apoptotic effect on SKHep-1 cells with increasing intracellular H(2)O(2) level. In conclusion, the present results shows that ASA induced SKHep-1 cell apoptosis has a relation with an early increase in intracellular H(2)O(2) level and catalase inhibitor synergizes to induce this process.