SUMMARY REPORTS OF EXCHANGE SCIENTISTS
(1) Katsuhiro Inoue, M.D.
Division of Clinical Chemotherapy
Cancer Chemotherapy Center
Japanese Foundation for Cancer Research
Kami-Ikebukuro 1-37-1, Toshima-ku, Tokyo
Sponsor and Host Institutions:
Dr. F. Ozols
National Cancer Institute
National Institutes of Health
Dates of Visit: October 8, 1985-October 7, 1986
Summary of Activities:
The antitumor activity of cisplatin (cis-DDP) is related to its covalent interaction with DNA where a major binding product is an intrastrand N7-bidentate adduct on adjacent deoxyguanosines. A novel immunoassay was used to quantitate this adduct in buffy coat DNA from A2780, an ovarian cell line which is sensitive to cis-DDP and 2780cp, an ovarian cell line which is 8-fold resistant to cis-DDP. Aliquots of cells were exposed to cis-DDP for 2 hours, incubated without drug for 2 hours, harvested and used for DNA isolation by CsCl gradient centrifugation and samples were analyzed for cis-DDP adducts by ELISA (Enzyme Linked Immunosorbent Assay). The quantity of measurable adducts clearly increased as the dose of cis-DDP increased. This result was observed in both cell lines, A2780 and 2780CP but there was no significant difference of adduct formation between two sublines. The data are as follows: A2780 cis-DDP 10 M (140 atom/ g DNA), 30 M (208), 100 M (1407), and 2780CP cis-DDP 10 M (202), 30 M (281), 100 M (1590). This result demonstrates that the acquired resistance to cis-DDP is due to another mechanism after adduct formation; for example, increased activity of the DNA repair system.
Glutathione (GSH) levels are elevated in resistant cell lines of ovarian cancer (2780cp 2780ME et al.) as compared to a sensitive ovarian cell line (A2780). Buthionine sulfoximine (BSO), a specific inhibitor of GSH synthesis, significantly increases the chemo- and radiosensitivity. The level of cis-DDP DNA adduct formation in 2780cp treated by cis-DDP with BSO is higher (129) than that of a resistant subline treated by cis-DDP without BSO (49). This result suggests that resistance reversal by BSO is due to increased adduct formation by cis-DDP.
Measurement of cis-DDP DNA adducts is a useful procedure for detection and quantitation of DNA adducts which caused a cytocidal effect of cis-DDP in human samples. Therefore, I will apply this procedure to predict the effect of cis-DDP and to monitor the removal of adduct in patients receiving cis-DDP chemotherapy.
The treatment for cancer patients should be geared to the individual, so a chemosensitivity test is needed to improve chemotherapeutic efficacy. Until now I have used the nude mouse-human tumor xenograft system and human tumor clonogenic assay as the chemosensitivity test. The objective of my study in NCI, NIH is to develop the chemosensitivity test based on the measurement of DNA replication damage after drug exposure. In the program on U.S.-Japan cooperative cancer research, I have studied cis-DDP DNA adduct assay, and I will apply this method to predict the effect of cis-DDP and to monitor the removal of adduct in patients receiving cis-DDP chemotherapy. We plan to continue our collaboration in the clinical field in addition to the field of research.
(2) Taisuke Ohnoshi
Department of Medicine
Okayama University Medical School
Okayama 700, Japan
Sponsor and Host Institution:
Dr. James F. Holland
Department of Neoplastic Diseases
Mount Sinai School of Medicine
New York, NY 10029
Dates of Visit: March 9-29, 1987
Summary of Activities:
The objective of my visiting the United States was to exchange information on recent results of clinical and experimental studies in the field of cancer chemotherapy. My special interest was to collect information on the current status of chemotherapy for some curable malignancies such as small cell lung cancer (SCLC) and non-Hodgkin’s lymphoma (NHL), and also to debate on the theoretical basis for drug combinations, drug resistance and drug screening tests.
During my stay in the Department of Neoplastic Diseases, Mount Sinai School of Medicine, I talked with Dr. Holland, Dr. Ohnuma and their co-workers about curative-intent chemotherapy for SCLC and NHL, including autologous bone marrow transplantation (ABMT), and about new findings of laboratory studies on drug resistance, cellular pharmacology in drug combinations and drug sensitivity tests. I had an opportunity to give a talk about our laboratory studies on drug resistance in the department seminar.
In the NCI-Branch, Naval Hospital, Dr. Ihde and I discussed recent advances in the treatment of SCLC. He and his co-workers showed me how they processed tumor specimens from patients with SCLC to establish cell lines and to test drug sensitivity.
In M.D. Anderson Hospital System Cancer Center, I saw Dr. Dicke, Dr. Spitzer and their fellows. We discussed the current status of ABMT in the treatment of SCLC and NHL. They showed me how they harvested bone marrow from patients and how they processed it for storage. They also showed me a new method of in vitro drug sensitivity testing which recently had been developed in their laboratory.
New information obtained through discussion and inspection in the United States will be helpful to promote our chemotherapy for SCLC and NHL, and also useful to project our laboratory studies in the field of cancer chemotherapy and pharmacology of anticancer agents.
(3) Yukihiko Naruki
First Department of Internal Medicine
Toho University, School of Medicine
6-11-1 Omori-Nishi, Ota-Ku, Tokyo. Japan 143
Sponsor and Host Institution:
Dr. S.M. Larson
Chief of Nuclear Medicine Department
Clinical Center, National Institutes of Health
Building 10, Room 1C401
Bethesda, Maryland 20892
Dates of Visit: April 1-September 30, 1986
Summary of Activities:
I had been involved in research with T101 monoclonal antibody (MoAb) in collaboration with Dr. Carrasquillo. This MoAb is directed against a pan T-cell antigen (CD5) expressed in T-cell malignancies, normal T-lymphocytes and chronic lymphocytic leukemia. Radiolabeled T101 is being investigated intensively at NIH as an imaging agent and is being developed for therapeutic purposes using Y-90. The preparations that I was dealing with were labeled with I-125, I-131, In-111, Y-90, Y-88, Bi-212 or Bi-206.
1. Stability of radiolabel on chelated antibodies.
The stability of In-111 and Y-90 on T101 in serum has been examined to determine the translocation to transferrin. In studying the “conventional chelate” prepared by a modification of the mixed anhydride, we saw an increase in translocation to transferrin with time and we identified chelates that showed improved retention of the radiolabel.
2. In vitro differences in metabolism of In-111, Y-90 and I-125 labeled T101 MoAb.
While In-111 T101 results in excellent tumor targeting in patients with cutaneous T-cell lymphoma, I-131 T101 rapidly clears resulting in minimal tumor uptake. To determine the biologic basis for these differences, we studied the retention of In-111and Y-90 labeled by a bifunctional chelate and I-125 T101 labeled with chloramine T in cell culture. There was consistently greater cellular retention of radioactivity for In-111 and Y-90 T101 than 1-125 T101. The cellular release of I-125 was reduced by low temperature or by addition of inhibitors of metabolism. (This study was presented at the 34th Annual Meeting of the Society of Nuclear Medicine.)
3. Selective cytotoxicity of Y-90 Iabeled T101 MoAb on human malignant T-cell lines.
As a preliminary step to clinical trials, we investigated the in vitro cytotoxicity of Y-90 labeled T101 against HUT102 and MOLT-4 human T-cell lines. T101 was labeled with Y-90, a pure beta emitter, by a bifunctional chelate. T-cell lines and a control B-cell line were cultured with Y-90 T101, and cytotoxicity was determined by measuring DNA synthesis by tritiated thymidine uptake. T-cell lines showed specific cytotoxicity when incubated with Y-90 T101 which was blocked by addition of excess unlabeled T101. (This study was presented at the 34th Annual Meeting of the Society of Nuclear Medicine.)