Looking Back on My Life of 40 Years as an Academic Person

There are fateful encounters that may be turning points in your life. I regard my retirement as a professor to be an excellent opportunity to look back on my life. I have been blessed with encounters that would never come again, for instance, when I decided to become a physician, then a hematologist, when I was appointed a professor, and when I selected a new path after a mandatory retirement age. Although my life was chosen by myself, it is true that it went in a completely different direction I had vaguely imagined or expected in the past. However, I have no regrets at all. Looking back on my life, it is totally attributed to wonderful encounters with many people, inspiration from them, and their support in various places. Now that I have completed my 16-year-plus responsibility as a professor and reached the retirement age with no troubles, I am just grateful to all the people who supported me. There are many things I experienced as a professor, but what struck me most is “people are the treasure.” I cite here a famous word of a great commander Shingen Takeda, “The people are your castle, your stone walls, your moat. We show compassion for our allies, and vengeance for our enemies,” which shows us “the importance of people.” The word “Jin,” the motto of Juntendo University, can help us to take the first step ( “Jin” means “I live surrounded by other people” and “thoughtful consideration to others, affection for others.” )


Preface
There are fateful encounters that may be turning points in our life. I would like to look back on my life of 40 years as an academic person and describe some of the turning points in my university life.

What made me a hematologist
The hematology department is where I started my career as a trainee physician at first. Internal medicine is the field in which I was the least interested when I was a medical student. Honestly speaking, I could not understand the field because it was too difficult. However, as a primary care physician, I directly saw patients who have an intractable blood cancer, such as acute leukemia and malignant lymphoma, and endure excruciating treatment; consequently, I considered that the posture of a physician to try to understand the feelings of patients was my ideal physician image and I decided to become a hematologist. I think that the choice was not wrong.

I became addicted to basic research
Immediately after I joined the medical office, chief professor Dr. Yasusada Miura advised me to conduct basic research on megakaryocytopoiesis. I felt as if he knew my laziness well because I was not interested in basic research at all. It was the first step to elucidate the mystery of megakaryocy-topoiesis in essential thrombocythemia, my life work. After that, I had an opportunity to receive direct guidance for the research from Dr. Toshio Suda (currently a professor at National University of Singapore), but the formation of megakaryocyte colonies in humans was still considerably difficult, and it was hardly conducted in Japan. A factor that stimulates human megakaryocyte colony, thrombopoietin, was not yet identified at that time. Therefore, the culture supernatant of human lymphocytes stimulated with phytohemagglutinin (PHA) (PHA-stimulated lymphocyte conditioned medium: PHA-LCM) was used for the formation of human megakaryocyte colony, but the quality of PHA-LCM greatly affected the formation of human megakaryocyte colony. I asked approximately 20 students, doctors, or nurses to give me their blood, to collect mononuclear cells, and then prepared PHA-LCM. Then, I used the bone-marrow blood donated by healthy volunteers (medical students at Jichi Medical University), and examined the PHA-LCM prepared from whose blood was most capable of forming megakaryocyte colonies. As a result, surprisingly, the PHA-LCM made from my own peripheral blood was most capable of forming megakaryocyte colonies. It was a fortunate discovery. Since then, I've used my blood to prepare PHA-LCM when necessary without having to worry about anyone else. My paper on megakaryocyte colonization in essential thrombocythemia (ET) was published in "British Journal of Haematology" 1) that I had admired during my youth, and became my first paper to commemorate in my basic research ( Figure 1). I still clearly remember that I was in seventh heaven when I saw my printed paper. As my research was started with megakaryocytes, I wanted to stick to this research theme in the future. However, the material used for the study on megakaryocytes is human bone marrow blood that is difficult to obtain, and the number of formed megakaryocyte colonies varied between individuals and caused variability of the data; therefore, I felt the difficulty of the experiment. Not only that but also I was too impatient to wait for colony formation for two weeks. Therefore, I decided to use megakaryocytic leukemia cell lines in the experiment, which were available as a material every time I needed, and to change my direction from the conventional research where bone marrow blood was used.

Success comes from failure ─Encounter with UT-7─
The first cell line used for research was CMK, a cell line with the nature of megakaryocytes. I received it from Dr. Takeyuki Sato at Chiba University and started a new research. Stimulation of the CMK cell line with a phorbol ester (also known as TPA or PMA) resulted in differentiation into mature megakaryocytes. One day, I happened to see the culture supernatant oddly become yellowish. I do not know why (not remember), but I tried sprinkling the culture supernatant on the original CMK cells. Surprisingly, the proliferation of the CMK cells was markedly enhanced. From the beginning, I thought that its activity was similar to GM-CSF. After I asked a laboratory to examine Figure 1 My first research paper after assigned to be a physician I am satisfied with its publication in British Journal Haematology (the right photo). At that time, the acceptance was notified by a letter (the left photo). the expression of GM-CSF mRNA, I received a report that the result was negative (later I found it was a mistake). Therefore, I inflated an unconvincing dream that it might be the imaginary "thrombopoietin," a novel hematopoietic factor, at that time and wanted to purify the factor from the culture supernatant. I performed the purification under the guidance of Dr. Masayuki Okada of the Eisai Tsukuba Laboratory. I continued the purification based on the proliferative activity of CMK cells. The purification progressed after about 1 year, and the peak of its activity was observed. I examined the colony forming ability by using normal bone marrow cells, but no megakaryocyte colony was formed, and most of the colonies were granulocyte/macrophage colonies. Arguably, this should be GM-CSF. Unfortunately, my guess was right. It was the neutralizing antibody of GM-CSF, which became finally available at that time, and its activity completely disappeared. In addition, GM-CSF mRNA was detected next (the previous result seemed to have been false negative). I found that the hematopoietic factor that we had pursued over 1 year was actually an existing GM-CSF, which was the moment I felt as if the balloon filled with my dream had burst. This task was accepted by Blood 2) , which was also my long-time dream. The research was completed with this, so I could not find any future research themes or a hope. I was not happy at all. When I was wondering what research theme I should select, Dr. Hideho Wada (the current chief professor of the Department of Hematology, Kawasaki Medical School) asked me to analyze the megakaryocyte colonies by using bone marrow blood from patients with acute megakaryoblastic leukemia. He had just gone back to Kawasaki Medical School at that time after studying at Dr. Toshio Suda's laboratory in Japan. At the time, I thought I would try to establish a new cell line by culturing a part of the remaining bone marrow blood in liquid. I just concentrated on the culture for about a month. Despite repeated trials and errors, such as transferring it to a 96 well plate and sometimes returning it to a flask, I did not see the cells growing at all. In retrospect, I just continued the observation every day, without taking a day off at all, as if I had been obsessed with something. When a month passed for the observation and I almost gave up and said, "It will not become a cell line. I failed," the previous research on CMK suddenly came to my mind. I came across the idea that the cells might proliferate in response to GM-CSF. Because I had a large amount of GM-CSF purified from the culture supernatant of CMK, I tried to add purified GM-CSF to the culture solution. Surprisingly, however, a few cells that seemed to have somewhat survived returned to normal after drinking an energy drink called GM-CSF. That is the beginning of the story on development of UT-7 3) . Subsequently, I successfully developed various UT-7 family cell lines as well as the UT-7/GM cell lines which can be differentiated into erythroblasts with EPO and megakaryocytes with TPO, showing growth dependence on UT-7/EPO 4) that exhibit growth dependence on erythropoietin (EPO), UT-7/TPO 5) that exhibit growth dependence on thrombopoietin, and GM-CSF 6) (Figure 2). The UT-7/EPO is highly sensitive to EPO and is still widely used in the bioassay of EPO. The UT-7/ TPO is highly sensitive to TPO and is used for screening of many TPO receptor agonists. Using these cell lines, many researchers including our group analyzed intracellular signaling of EPO and TPO, and the name of UT-7 has spread worldwide. Through establishment of UT-7, I have learned "If we make a good use of a failure next, it is not a failure. How to apply the failure to the next step is important for life that cannot be repeated."

My life has bloomed due to transfer to Juntendo University
In October 2004, my colleagues held a great farewell party for me at a French restaurant "Seiyodo" (the head restaurant is in Mito City) located in Jichi Medical University, which had supported my career for 23 years after graduating from Niigata University (Figure 3). After that, I started to work for Yamanashi University as the first professor of Department of Hematology (Figure 4). In August 2009, when about 5 years had passed, I was appointed Chief Professor, Department of Internal Medicine, Hematology Course in Juntendo University School of Medicine. It is not an overstatement to say that my transfer to Juntendo University helped bloom my life. One opportunity is a relationship with the Japanese Society of Hematology. I served as the director of the academic society and the chairperson of the editorial board for the journal of the academic society, "Clinical Blood" for 8 years, and sponsored the "81st Annual Meeting of the Japanese Society of Hematology" in 2019 as the chairperson (Figure 5). At the 116th Annual Meeting of the Japanese Society of Internal Medicine (2019), I held an invitation lecture titled "Pathology and Treatment Strategies for Myeloproliferative Tumors." As for the studies I have conducted after transferring to Juntendo Univer-sity, I analyzed the calreticulin mutation with unknown functions that was found in some patients with myeloproliferative tumor by using UT-7/ TPO and UT-7/EPO cell lines expressing different cytokine receptors. In 2016, I became the first person in the world to detect a phenomenon of "mutant molecular chaperon causes cancer via constitutive activation of the TPO receptors," which violated the conventional common sense of tumor biology (Top 10 papers in Blood Journal,   7) . Furthermore, I revealed that mutant CALR forms homomers in the endoplasmic reticulum and binds to TPO receptors as a ligand (the Best Paper in Leukemia Journal in 2018) 8) , and that cancer develops by constitutively activating downstream signaling molecules after migration to the cell surface 9) . These achievements were highly recognized internationally, and I was awarded the second prize of the "Erwin-von-Bälz Award" in 2019 ( Figure 6) and, subsequently the "Japanese Society of Hematology Award" in 2020 (Figure 7). I am confident that I strived to do these basic and clinical researches, which made the Department of Hematology Course, Department of Internal Medicine, Faculty of Medicine, Juntendo University a Japanese representative course in the area of myeloproliferative neoplasms (MPN). Without the establishment of UT-7 and transfer to Juntendo University, no such series of results would have been produced. I believe that it should be the biggest turning point in my life.

I have learned "people are the treasure"
For the period of 16 years and 6 months, I served as a professor at University of Yamanashi and Juntendo University combined. What I learned from this precious experience is "people are the treasure." This is exactly the importance of people, which has been expressed in a famous word of the great commander, Shingen Takeda, "The people are your castle, your stone walls, your moat. We show compassion for our allies, and vengeance for our enemies." I still clearly remember that at the celebration ceremony held in November 2009 for the appointment of Juntendo University Professor, I said in the greeting speech, "I am sure to make every effort to create a new course so that everyone can think it is great to have welcomed me as a Juntendo University Professor of Hematology." With this determination always in mind, I am glad to have had sense of accomplishment of "I achieved it as a professor" and reached the retirement age. This is attributed to the support kindly given to me from the course members and the whole staff related to hematology (Figure 8 and 9). I do not have anything except for feelings of gratitude for the "encounters that would never come again" with my "treasure" (every person I have met).

Conflicts of interest:
The author declares that there are no conflicts of interest