SUMMARY REPORTS OF EXCHANGE SCIENTISTS

(1) TAHARA, Eiichi
Home Institution:
1st Department of Pathology, Hiroshima University School of Medicine (Professor and Chairman)

Sponsor and Host Institution:
1) Dr. M. Ryoji,
Research Institute of Scripps Clinic
2) Dr. J. Schlom,
Laboratory of Tumor Immunology and Biology, NCI, NIH
Dates of Visit:
from November 1st, 1987 till November 24th, 1987.
Nov.01: Tokyo (DEP)
Nov.02: Research Institute of Scripps Clinic (Dr. Ryoji), Seminar
Nov.03: Salk Institute and La Jolla Cancer Research Center
Nov.05: Beckmann Research Institute of the City of Hope (Dr. Ohno), Seminar
Nov.06,7: Research Institute of Scripps Clinic
Nov.09-11: Attendance to Second Conference on Immunity to Cancer In Williamsburg
Nov.12-18: National Cancer Institute, NIH
Nov.20: UCLA (Dr. Walsh), Seminar
No.21-23: Research Institute of Scripps Clinic
Nov.24: Los Angeles (DEP)
Nov.25: Tokyo (ARR)

Summary of Activities:
I had lectures and discussions about interaction between growth factors and oncogenes in progression of human gastric cancers in Research Institute of Scripps Clinic, Beckmann Research Institute of the City of Hope, NIH and UCLA which I visited in U.S.A. In the consequence of those, we have decided to do cooperative works in the future concerning four projects as follows; 1) Expression of 5S ribosomal RNA in human gastrointestinal cancers, 2) PCNA (proliferating cell nuclear antigen) in biological malignancy of human gastric cancers, 3) Effect of site-selective cyclic AMP analogs on cell growth of human gastric cancer cell lines, and 4) Alteration of tropomyosin in human gastric cancer by growth factors. Out of these four projects, 1) and 2) will be studied with Dr. Ryoji and Dr. Tan in Research Institute of Scripps Clinic and 3) and 4) will be done with Dr. Cho-Chung and Dr. Bassin in NIH. In addition to the above-mentioned activities, I attended the Second Conference on Immunity to Cancer in Williamsburg, in which I discussed basic and clinical significance of monoclonal antibodies against human cancers for cancer theraphy.



(2) Katsuhiro Fukuda
Home Institution:
Kurume University, School of Medicine

Sponsor and Host Institution:
Sponsor; NCI and JSPS
Host Institutions; NCI, USC and UH
Dates of Visit: from July 13 to August 11, 1987

Summary of Activities:
(Include objectives of study, achievements, and how study relates to future work. List any publications resulting from this study.)
The present visit was intended to exchange findings, difficulties and opinions for future study with US epidemiologists in the field of nasal sinus and pancreatic cancer.
With regard to the nasal sinus cancer, there have been noticed fairly consistent findings with risk factors for this site of cancer but substantial discrepancies with histological findings between the US studies and the Japanese studies. It has been pointed out that a US-Japan cooperative study for histological validation would be quite meaningful for better understanding of the etiology.
As to the pancreatic cancer, we have come to the same understandings that although there are many epidemiological difficulties, we should continue our effort to examine the past findings and to discover new theory in the etiology of pancreatic cancer.

Please specify:
1. Has the Program assisted you in achieving your research objectives? Explain. Yes, this program gave me an opportunity to have fruitful discussions with US epidemiologists.
2. How can progress in your research effort be enhanced through this Program? Do you plan to continue your collaboration?
It has encouraged me to continue the epidemiologic study in this field and we have an actual plan for collaboration.
3. Please provide Information indicating how your efforts have contributed to the progress of the NCI-Japan Cancer Program.
The present visit made me possible to plan a US-Japan cooperative study.
You may submit additional information if related to the exchange program. In covering letter provide any additional comments or suggestions for the program.



(3) Mituru Takanami
Home Institution:
Institute for Chemical Research, Kyoto University

Sponsor & Host Institution:
Dr. Poul H. Silverman
Lawrence Berkeley Laboratory
University of California, Berkeley
Dr. Walter Gilbert
Biological Laboratories
Harvard University
Dr. George Church
Harvard Medical School
Dr. Joachim Messing
Waksman Institute
Rutgers University
Dr. Peter Model
The Rockefeller University
Dates of Visit: January 26, 27: University of California, Berkeley
January 28: Harvard University
January 29, 30: Harvard Medical School
February 1: Headquarters of NIH & NSF
February 2: Headquarters of Depart. Energy & NSF
February 3, 4: Rutgers University
February 5, 6: Rockefeller University

Summary of Activities
The main subject of this visit was the feasibility study of human gene analysis Investigation was particularly focussed on how to ovecome the technical barriers for long distance-DNA sequencing which is a key step to start the genome-sequencing project of higher organisms, including the human genome For this purpose, I visited the following scientists to learn about their activities.
At Lawrence Berkeley Laboratory, University of California, I met Dr. P. Silverman (Director, Donner Lab.) and Dr. J. Bartley (Deputy Head, Human Genome Center), and learned that their group has started cloning of human chromosome No. 19, by using the YAC-vector system. This vector has capacity to clone the largest DNA fragments among the known vectors. However, a problem is its low transformation efficiency. This was also their problem. We discussed about the possibility how to increase the efficiency. Another their problem was unstability of some cosmid clones. I believe, this is an important barrier to overcome and this can be solved by analysing the mechanism Involved in recA-independent delection event in the EK system.
In Boston, I visited Dr. Gilbert’s laboratory at Harvard and Dr. Church’s laboratory at Harvard Medical School, and I was deeply impressed by Dr. Church’s new sequencing technology, named “Multiplex DNA Sequencing”. The principle of the method is based on that of genomic sequencing Dr. Church semi-automated the procedure, so that they now have capacity to read nearly one million bp/month. According to their procedure, however, DNA fragments obtained by shot-gun cloning have been used for sequencing. A question is whether or not any DNA segments can be cloned at random by “shot-gun cloning”.
At Rutgers University, I stayed Dr. Messing’s laboratory and we spent many hours to discuss about how to solve possible technical barriers for long distance-DNA sequencing.
At Rockefeller University, I visited Dr. Zinder’s laboratory, and discussed with Drs Model and Horiuchi about how to construct a host system, which can stably maintain cosmid clones as well as M13 clones, and possible mechanisms involved in recA-independent deletion.

Comments
Through the discussions with leading scientists in this field in U.S.A., I led to a conclusion that at least the following barriers should be solved for sequencing of such long DNA as the human chromosomes.
1) Collection of new restriction enzymes which recognize eight to ten base-pairs is required for construction of physical maps. So far two eight base-cutters, NotI and SfiI, are available but not enough.
2) Establishment of bost-vector systems which can clone must larger DNA segments at high frequencies will greatly help the efficient construction of genomic libraries. So far a yeast vector, named YAC, is available, but its transformation efficiency is very low.
3) Cosmid clones carrying large inserts are known to receive deletions at high frequencies, so that it is absolutely required to find appropriate host cells which do not introduce such deletions.
4) Starting from a single chromosome of higher organisms, the quantity of DNA manipulatable will be very small. Development of micro-cloning systems is required.
5) Improvement of a sequence-gel system is required to increase the number of bases readable in one run. In the dideoxy-sequencing system, reading errors are mostly caused by ambiguous positioning of bands, and this is mainly due to gel compression and low-processivity of DNA polymerase. If a sequencing-gel system which gives uniform and evenly spaced bands are developed, number of bases which can read in one run will be strikingly improved. This is especially important to automatic DNA sequencers which use the optical system for band detection.
I believe that US-Japan collaboration about these technical barriers will be important as well as that for the sequencing project.