| Co-Investigator(Kenkyū-buntansha) |
MAEKAWA Masato Hamamatsu Univ.Sch.Med., Faculty of Med, Professor, 医学部宇, 教授 (20190291)
NAITO Kensuke Hamamatsu Univ.Sch.Med., Faculty of Med, Assistant Professor, 医学部, 助手 (40334990)
OHNISHI Kazunori Hamamatsu Univ.Sch.Med., Faculty of Med, Associate Professor, 医学部, 助教授 (80252170)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2003: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2002: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
Gemtuzumab ozogamicin (GO), a calicheamicin-conjugated humanized anti-CD33 mouse monoclonal antibody, has recently been introduced clinically as a promising drug for the treatment of patients with acute myeloid leukemia (AML), more than 90 % of which express CD33 antigen. However, our recent study suggested that GO was excreted by a multidrug-resistance (MDR) mechanism in P-glycoprotein (P-gp)-expressing leukemia cell lines. We analyzed the in vitro effects of GO on leukemia cells from 27 AML patients in relation to the amount of P-gp, MDR-associated protein 1 (MRP1), CD33 and CD34, using a multi-laser-equipped flow cytometer. The cytocidal effect of GO, estimated by the amount of hypodiploid portion on cell cycle, was inversely related to the amount of P-gp estimated by MRK16 monoclonal antibody (p=0.004), and to the P-gp function assessed by intracellular rhodamine-123 accumulation in the presence of PSC833 or MS209 as a MDR-modifier (p=0.0004 and p=0.002, respectively). In addition,
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these MDR-modifiers reversed GO resistance in P-gp-expressing CD33+ leukemia cells (p=0.001 with PSC833 and p=0.0007 with MS209). In CD33+ AML cells from 13 patients, GO was less effective on CD33+CD34+ than CD33+CD34-cells (p=0.002). PSC833 partially restored the effect of CMA-676 in CD33+CD34+ cells. These results suggest that the combination use of GO and a MDR-modifier will be more effective on CD33+ AML with P-gp-related MDR.
Acute promyelocytic leukemia (APL) cells express a considerable level of CD33, which is a target of GO, and a significantly lower level of P-gp. In this study, we examined whether GO was effective on all-traps retinoic acid (ATRA)-or arsenic trioxide (ATO)-resistant APL cells. Cells used were an APL cell line in which P-gp was undetectable (NB4), ATRA-resistant NB4 (NB4/RA), NB4 and NB4/RA that had been transfected with MDR-1 cDNA (NB4/MDR and NB4/RA/MDR, respectively), ATO-resistant NB4 (NB4/As) and blast cells from 8 patients with clinically ATRA-resistant APL including 2 patients with ATRA-and-ATO-resistant APL. The efficacy of GO was analyzed by ^3H-thymidine incorporation, the dye exclusion test and cell cycle distribution. GO suppressed the growth of NB4, NB4/RA and NB4/As cells in a dose-dependent manner. GO increased the percentage of hypodiploid cells significantly in NB4, NB4/RA and NB4/As cells, and by a limited degree in NB4/MDR and MB4/RA/MDR cells. Similar results were obtained using blast cells from the patients with APL. GO is effective against ATRA-or ATO-resistant APL cells that do not express P-gp, and the mechanism of resistance to GO is not related to the mechanism of resistance to ATRA or ATO in APL cells. Less
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