Yasuo Kuwazuru

Purification and tissue distribution of human thymidine phosphorylase; high expression in lymphocytes, reticulocytes and tumors

Thymidine phosphorylase (dThdPase) is an enzyme involved in pyrimidine nucleoside metabolism, but little is known about its physiological functions. We purified dThdPase from human placenta and used it for antibody preparation. The purified material appears as a single band at 55,000 dalton on sodium dodecylsulfate-polyacrylamide gel electrophoresis. We obtained a specific antibody raised in rabbits that detected a single polypeptide with a molecular weight of 55,000 dalton in the post nuclear homogenates of several human tissues, on immunoblotting. Using the same technique, dThdPase was highly expressed in the liver, lung, spleen, lymph nodes and peripheral lymphocytes. Immunohistochemical staining revealed that macrophage-like cells contained a much higher amount of dThdPase than parenchymal cells in the liver and lung. dThdPase was found to be highly expressed in T- and B-cell-type malignant lymphoma cells, but low in lymphoblastic and myeloblastic leukemia cells. We also found that carcinomas in the stomach, colon and ovary contained higher amounts of this enzyme than non-neoplastic regions of the tissues. These data suggest that dThdPase plays a role in proliferation and/or differentiation of leukocytes and in cancer proliferation.

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.

Expression of the multidrug transporter, P‐glycoprotein, in chronic myelogenous leukaemia cells in blast crisis

The overexpression of a cell‐surface glycoprotein termed P‐glycoprotein (P‐gp) is frequently associated with multidrug resistance (MDR) in cell lines in vitro. To evaluate the implications of P‐gp expression in clinical drug‐resistance, we examined the expression of P‐gp in fresh leukaemia cells from chronic myelogenous leukaemia (CML) patients in blast crisis. By using immunoblotting with a monoclonal antibody against P‐gp, C219, we showed that leukaemia cells from three CML patients in blast crisis were P‐gp negative at the stage when these patients were in complete remission, and that the cells showed high levels of P‐gp expression at times when the same patients had relapsed and had not responded to chemotherapy. Six out of 11 patients (nine in the refractory state) were P‐gp positive and they rarely responded to chemotherapy. These data suggest that the expression of P‐gp is closely associated with drug‐resistance in CML.

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.

Biosynthesis, processing and half-life of P-glycoprotein in a human multidrug-resistant KB cell

The biosynthesis, processing, and half-life of the drug efflux pump, P-glycoprotein, were studied in human multidrug-resistant KB (KB-C2) cells selected for resistance to colchicine. An antibody directed against a synthetic oligopeptide corresponding to the amino-acid sequence (Glu-393-Lys-408) of P-glycoprotein from human mdr1 cDNA was prepared in rabbits. With immunoblotting and immunoprecipitation, we detected a 140-170 kDa protein in KB-C2 cells but not in parental sensitive KB cells. KB-C2 cells made a 125 kDa precursor that was slowly processed (t1/2 = 45 min) to the mature form of 140-150 kDa. The processing rate of P-glycoprotein was slower than that of low-density lipoprotein receptor. We detected another 160-180 kDa smear band, which might be a completely denatured form of P-glycoprotein. With immunoblotting, a minor band of high molecular mass (greater than 500 kDa) was also detected and this form increased after the cells were treated with chemical cross-linker, 1,5-difluoro-2,4-dinitrobenzene. The half-life of P-glycoprotein was long; no significant loss of P-glycoprotein was observed within 24 h after synthesis. Cells treated with tunicamycin produced a 120 kDa form of P-glycoprotein which was no longer processed but showed stability similar to that of the mature 140-150 kDa form. Agents that reverse multidrug resistance, phorbol ester and transport substrate did not affect the stability of P-glycoprotein.

Combination chemotherapy (RCM protocol: response-oriented cyclic multidrug protocol) for the acute or lymphoma type adult T-cell leukemia.

43 patients with the acute or lymphoma type ATL were treated with the new combination chemotherapy (RCM protocol: response-oriented cyclic multidrug protocol) between January 1989 and December 1991. Complete response (CR) and partial response (PR) were achieved in 20.9% and 65.1% of all treated patients respectively. The median duration of survival was 6.0 months. The survival duration of patients with a high serum lactate dehydrogenase (LDH) value (> or = 1,000 unit) and/or a poor performance status (PS) (PS 3 or 4) were also improved but not in patients with a severe leukocytosis (> or = 35,000/microliters). Toxicity was mild (grade 1 or 2) except hematologic toxicity in 4 patients (9.3%) and alopecia in one patient (2.3%). In spite of many patients with a poor PS (PS 3 or 4), our chemotherapeutic results are equal or superior to other previous reports. It seems that response-oriented chemotherapy is suitable for the ATL patients with poor prognostic factors. These results indicate that the RCM protocol is very useful as the first choice chemotherapy for the acute or lymphoma type ATL.