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Biomedical subjects

Takahiro Yamauchi

Publications and source records attributed to Takahiro Yamauchi.

12 recordsLinked to original sources

Acute leukemia therapy at a crossroads: from conventional chemotherapy to the era of precision medicine.

Since the discovery of cytotoxic agents in the mid-20th century, acute leukemia has consistently served as a model for oncology research. As the Human Genome Project and subsequent genomic profiling elucidated the landscape of somatic mutations and cytogenetic aberrations driving leukemogenesis, the development of molecularly targeted therapies has dramatically accelerated, yielding significant improvements in patient outcomes. In acute myeloid leukemia (AML), the emergence of selective inhibitors targeting high-frequency alterations such as FLT3, NPM1, and IDH1/2 has redefined the standard of care, demonstrating superior efficacy when combined with conventional intensive chemotherapy or hypomethylating agents. Simultaneously, for acute lymphoblastic leukemia (ALL), in addition to the significant improvements achieved by tyrosine kinase inhibitors (TKIs) for BCR-ABL-positive ALL, the advent of CD19- or CD22-targeted monoclonal antibodies and CAR-T cell therapies has marked an epoch-making milestone, representing a major paradigm shift in the management of relapsed or refractory cases. Bridging these two distinct lineages, menin inhibitors have emerged as a novel class of agents targeting a common pathogenic mechanism in KMT2A-rearranged AML/ALL and NPM1-mutated AML, exhibiting promising antileukemic activity across these subtypes. In this review, we describe the evolution of leukemia therapy-highlighting historical trajectory across AML, APL, and ALL from uniform cytotoxic chemotherapy to molecularly targeted agents, antibody-based therapies, and chemo-free paradigms, while outlining future perspectives for precision hematology.

Acute lymphoblastic leukemia↗

Simple and sensitive method for quantification of fludarabine triphosphate intracellular concentration in leukemic cells using isocratic liquid chromatography.

A simple, isocratic HPLC method was newly developed for quantitating intracellular fludarabine triphosphate (F-ara-ATP). Samples (500 microl) were injected onto an anion-exchange column and eluted isocratically with phosphate-acetonitrile buffer (flow rate: 0.7 ml/min) at an ambient temperature. F-ara-ATP was quantitated according to its peak area at the absorbance of 261 nm. The standard curve was linear with minimal within-day and inter-day variability. The low and high quantification limits were 50 pmol and 20 nmol, respectively. The method was capable of measuring F-ara-ATP generated in cultured leukemic cells in vitro. Thus, our method will be useful because of its sensitivity and simplicity as well as applicability to biological materials.

Antineoplastic Agents↗

Enhanced DNA excision repair in CCRF-CEM cells resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea, quantitated using the single cell gel electrophoresis (Comet) assay.

Enhanced DNA repair activity is important for the development of cellular resistance to alkylating agents. Here, we quantitated the kinetics of DNA excision repairs initiated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in human leukemia CCRF-CEM cells. CEM cells that had been established resistant to BCNU (CEM-R) were evaluated in comparison with parental CEM cells (CEM-S). The excision repair kinetics were quantitated as the amount of DNA single strand breaks, which were generated from the incision/excision of the damaged DNA and were diminished by the rejoining of renewed DNA, using the single cell gel electrophoresis (Comet) assay. CEM-R cells were 10-fold more resistant to BCNU than CEM-S cells, and also showed cross-resistance to melphalan and cisplatin. In response to the treatment with BCNU, both CEM-S and CEM-R cells initiated an incision/excision reaction at the end of the incubation period, and completed the rejoining process within 4 hr. While CEM-S cells could not repair the damage induced by the high concentration of BCNU, CEM-R cells completed the repair process regardless of BCNU concentrations, suggesting enhanced excision repairs in CEM-R cells. The excision repair activity of CEM-R cells was increased with regard to the incision reaction and to the rate of the repair. Similar results were obtained using ultraviolet C, suggesting enhanced nucleotide excision repair in CEM-R cells. Thus, the enhanced DNA excision repairs were successfully quantitated in the resistant leukemic cell line using the Comet assay. The evaluation of the repair activity may predict the sensitivity of cancer cells to chemotherapy and provide a clue to overcome the resistance.

Antineoplastic Agents, Alkylating↗

Successful treatment of pyoderma gangrenosum that developed in a patient with myelodysplastic syndrome.

We describe the successful treatment of pyoderma gangrenosum (PG) that developed in a patient with myelodysplastic syndrome (MDS). A 63-year-old Japanese man with MDS was admitted to our hospital because of a large skin ulcer on his neck in November 2001. The initial diagnosis was infectious dermatitis, and antimicrobial therapy was performed, using imipenem/cilastatin, isepamicin, and amphotericin B. However, this therapy was not effective, and the lesion worsened. Cultures of blood, throat swab, and ulcer pus yielded no microorganisms. A biopsy of the skin lesion revealed a severe infiltration of neutrophils in the dermis, without any evidence of infection. The lesion was finally diagnosed as PG, and systemic administration of corticosteroid hormone was started in December 2001. The patient was initially pulsed with 1 g methylprednisolone daily for 3 days. The dose was immediately reduced, and the treatment was maintained with 30 mg prednisolone daily. The skin lesion responded markedly to the therapy, and C-reactive protein became negative. The patient was discharged in February 2002 because the lesion was almost cured. Prednisolone administration was tapered after 6-month maintenance therapy. No recurrence of PG was seen, although his MDS transformed into leukemia in April 2003. Only 31 cases of MDS developing PG have been reported in the past 20 years in Japan. This report describes one such rare patient who was successfully treated with the use of high-dose pulse methylprednisolone and long-term maintenance therapy.

Diagnosis, Differential↗

Pure red cell aplasia developing into myeloproliferation with myelodysplasia and subsequent leukemia after cyclosporin A therapy.

We describe a very rare case of a patient who presented with red cell aplasia that later developed into myeloproliferation with myelodysplasia and eventually leukemia. A 63-year-old man presented with anemia and reticulocytopenia in May 1997. A bone marrow examination revealed erythroid aplasia with normal production of myeloid cells and megakaryocytes with a normal karyotype. After the diagnosis of pure red cell aplasia was made, the patient was treated with prednisolone and then with cyclosporin A (CyA). Two weeks after the initiation of CyA treatment, the peripheral reticulocyte count began to increase with a regrowth of erythroid cells in the bone marrow. Meanwhile, the peripheral white blood cell and platelet counts also increased to more than 10,000/microL and 1,000,000/microL, respectively. Examination of a bone marrow aspirate in December 1997 revealed myelodysplastic changes with trisomy 8. Despite the discontinuation of CyA and the administration of 1-beta-D-arabinofuranosylcytosine stearyl monophosphate, leukemia developed in August 1998. In September 1998, the patient died of sepsis during a neutropenic period that followed remission-induction therapy. In the mechanism of pathogenesis, CyA may induce upon pure red cell aplasia a secondary myeloproliferative disorder with myelodysplasia and leukemia. An alternative possibility is that CyA reduces autoimmune-mediated suppression of the underlying stem cell disorder and that the result of this reduction is the manifestation of myeloproliferation and leukemia.

Cell Division↗

Alkylator-induced DNA excision repair in human leukemia CCRF-CEM cells in vitro, measured using the single-cell gel electrophoresis (comet) assay.

The capacity to repair DNA damage is an important factor that affects the therapeutic outcome in cancer treatment. To clarify the cellular repair response, we investigated the kinetics of DNA excision repair initiated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in human leukemia CCRF-CEM cells at an exponential growth phase in vitro. Using the alkaline single-cell gel electrophoresis (comet) assay, we quantitated the repair kinetics as the amount of DNA single-strand breaks that were generated from the incision and were diminished by the rejoining in the repair process. CEM cells could initiate DNA excision repair in response to BCNU by starting an incision reaction. However, the incision capacity came to a plateau at a concentration of 80 to 100 microM or after an incubation time of 90 to 120 minutes. When the cells were pulsed with 40 microM BCNU, the maximal incision occurred at the end of the incubation period, and the repair process was completed within 4 hours When cells were treated with 100 microM BCNU, the incised DNA was not rejoined at 4 hours, suggesting that the repair was not completed. Higher concentrations might surpass the cellular capacity for repair and would be associated with increased cell death. Evaluation of the repair process may provide a clue for therapeutic strategies to improve clinical efficacy if accelerated DNA repair is responsible for the drug resistance.

Antineoplastic Agents, Alkylating↗

An autopsy case of disseminated mucormycosis in a neutropenic patient receiving chemotherapy for the underlying solid malignancy.

Mucormycosis is a rare, opportunistic infection caused by fungi of the order Mucorales, class Zygomycetes. These fungi produce fatal opportunistic infections in immunocompromised patients, especially in those with severe neutropenia. Recently, mucormycosis has become more widespread, because potent, myelosuppressive chemotherapies are performed more often than before. Nevertheless, this infection rarely occurs in patients with solid malignancies. Here, we describe an autopsy case of disseminated mucormycosis in a neutropenic patient who was receiving chemotherapy for an underlying solid malignancy. A 31-year-old Japanese man received cytotoxic chemotherapy with etoposide for the pulmonary metastasis of a secondary malignant fibrous histiocytoma. This patient had long been treated with chemotherapeutic agents for this solid cancer and for the preceding eosinophilic granuloma, both of which were highly resistant to the therapy. During the treatment with etoposide, his neutrophil count declined to less than 100/microl. He presented with high fever and severe dyspnea. Pneumonia was highly suspected. The chemotherapy was discontinued, and granulocyte colony-stimulating factor was administered. Although the neutrophil count recovered, the pneumonia progressed. The patient experienced respiratory failure and died 17 days after the onset of this episode. An autopsy revealed dissemination of mucormycosis not only in the lungs but also in the liver, the spleen, the kidney, and in the digestive tract. The therapy-related severe neutropenia, and the probable impairment of the immune system, because of the previous chemotherapies, would have been responsible for this fatal infection.

Adult↗

1-beta-D-arabinofuranosylcytosine is cytotoxic in quiescent normal lymphocytes undergoing DNA excision repair.

We have sought to clarify the potential activity of the S-phase-specific antileukemic agent 1-beta-D-arabinofuranosylcytosine (ara-C), an inhibitor of DNA synthesis, in quiescent cells that are substantially non-sensitive to nucleoside analogues. It was hypothesized that the combination of ara-C with DNA damaging agents that initiate DNA repair will expand ara-C cytotoxicity to non-cycling cells. The repair kinetics, which included incision of damaged DNA, gap-filling by DNA synthesis and rejoining by ligation, were evaluated using the single cell gel electrophoresis (Comet) assay and the thymidine incorporation assay. When normal lymphocytes were treated with ultraviolet C or with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), the processes of DNA excision repair were promptly initiated and rapidly completed. When the cells were incubated with ara-C prior to irradiation or BCNU treatment, the steps of DNA synthesis and rejoining in the repair processes were both inhibited. The ara-C-mediated inhibition of the repair processes was concentration-dependent, with the effect peaking at 10 microM. The combination of ara-C with these DNA repair initiators exerted subsequent cytotoxicity, which was proportional to the extent of the repair inhibition in the presence of ara-C. In conclusion, ara-C was cytotoxic in quiescent cells undergoing DNA repair. This might be attributed to unrepaired DNA damage that remained in the cells, thereby inducing lethal cytotoxicity. Alternatively, ara-C might exert its own cytotoxicity by inhibiting DNA synthesis in the repair processes. Such a strategy may be effective against a dormant subpopulation in acute leukemia that survives chemotherapy.

Antimetabolites, Antineoplastic↗

Inhibition of nucleotide excision repair by fludarabine in normal lymphocytes in vitro, measured by the alkaline single cell gel electrophoresis (Comet) assay.

Alkylating agents or platinum analogues initiate several excision repair mechanisms, which involve incision of the DNA strand, excision of the damaged nucleotide, gap filling by DNA resynthesis, and rejoining by ligation. The previous study described that nucleotide excision repair permitted incorporation of fludarabine nucleoside (F-ara-A) into the repair patch, thereby inhibiting the DNA resynthesis. In the present study, to clarify the repair kinetics in view of the inhibition by F-ara-A, normal lymphocytes were stimulated to undergo nucleotide excision repair by ultraviolet C (UV) irradiation in the presence or absence of F-ara-A. The repair kinetics were determined as DNA single strand breaks resulting from the incision and the rejoining using the alkaline single cell gel electrophoresis (comet) assay. DNA resynthesis was evaluated in terms of the uptake of tritiated thymidine into DNA. The lymphocytes initiated the incision step maximally at 1 h, and completed the rejoining process within 4 h after UV exposure. UV also initiated thymidine uptake, which increased time-dependently and reached a plateau at 4 h. A 2-h pre-incubation with F-ara-A inhibited the repair in a concentration-dependent manner, with the maximal inhibition by 5 mM. This inhibitory effect was demonstrated by the reduction of the thymidine uptake and by the inhibition of the rejoining. A DNA polymerase inhibitor, aphidicolin, and a ribonucleotide reductase inhibitor, hydroxyurea, were not so inhibitory to the repair process as F-ara-A at equimolar concentrations. The present findings suggest that inhibition of nucleotide excision repair may represent a novel therapeutic strategy against cancer, especially in the context of resistant cells with an increased repair capacity.

Antineoplastic Agents↗

UCN-01 (7-hydroxystaurosporine) inhibits DNA repair and increases cytotoxicity in normal lymphocytes and chronic lymphocytic leukemia lymphocytes.

Elevated DNA repair processes represent resistance mechanisms to the treatment of malignancies with alkylating agents. Recently, the cell cycle checkpoint abrogator, UCN-01, was reported to inhibit nucleotide excision repair in cell-free systems. We hypothesized that if UCN-01 was combined with DNA-damaging agents, UCN-01 might inhibit the damage repair processes, thereby enhancing cytotoxicity in quiescent cells. Here, we investigated the effect of UCN-01 on DNA repair and viability of quiescent normal lymphocytes and chronic lymphocytic leukemia lymphocytes treated with UV or the cyclophosphamide prodrug 4-hydroperoxycyclophosphamide (4-HC). DNA damage repair kinetics were determined as DNA single strand breaks by the alkaline single cell gel electrophoresis (comet) assay and by [3H]thymidine incorporation. Pretreatment with UCN-01 inhibited DNA repair initiated by UV or 4-HC in normal lymphocytes as well as chronic lymphocytic leukemia lymphocytes in a concentration-dependent manner at clinically relevant levels (50-300 nM). This inhibition was demonstrated by the decreases in incision capability, DNA resynthesis, and in rejoining, suggesting that UCN-01 inhibits the multiple sites of the repair processes. The higher UCN-01 concentration (300 nM) maximized the inhibitory effects and enhanced the UV- or 4-HC-induced cytotoxicity, as determined by annexin V binding or Hoechst 33342 staining. This enhancement was not obtained by the lower concentrations that incompletely inhibited the repair, suggesting the close association between the inhibition of the repair and the enhancement of the cytotoxicity. Our findings suggest that UCN-01 may be a good candidate for combination strategies of cancer treatment.

Alkaloids↗

Pharmacological study of modified intermediate-dose cytarabine therapy in patients with acute myeloid leukemia.

BACKGROUND: Instead of the original intermediate dose (0.5 g/m2), a modified intermediate-dose 1-beta-D-arabinofuranosylcytosine (ara-C) therapy (1 g/m2, 1-h intravenous infusion) was pharmacologically studied in 11 leukemic patients. PATIENTS AND METHODS: The concentrations of ara-C and its inactive metabolite, 1-beta-D-arabinofuranosyluracil (ara-U) in the plasma, urine and cerebrospinal fluid were determined using high performance liquid chromatography. RESULTS: The plasma ara-C reached a peak (61.2 +/- 52.7 microM) that far surpassed the saturating level for intracellular activation of the drug. The plasma ara-U reached its peak (139.8 +/- 40.0 microM) and was maintained with a half-life of 277 +/- 76 min. About 60% of the administered drug was recovered, mainly as ara-U in urine within 12 h. In contrast to the original intermediate dose, the therapeutic ara-C levels (above 0.4 microM) persisted in the central nervous system. The therapy salvaged one relapsed leukemia patient with central nervous system involvement. CONCLUSION: Modified intermediate-dose ara-C provides a sufficient plasma ara-C level with a concomitant therapeutic concentration in the cerebrospinal fluid.

Acute Disease↗