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Genome Giants – Tak Mak, Senior Scientist, Princess Margaret Cancer Centre

Tak Mak is a world leader in the genetics of immunology and cancer. He is currently a Senior Scientist at the Princess Margaret Cancer Centre as well as a Full Professor at the Universities of Toronto and Hong Kong. He is widely known for his cloning of the human T cell receptor beta chain gene in 1984, and his team’s discovery of the function of the immune checkpoint protein CTLA-4 in 1995. Dr. Mak is also the co-founder of Agios Pharmaceuticals, which specialises in developing innovative anti-cancer agents. Dr. Mak’s contributions to important research in biochemistry, immunology and cancer make him truly a Genome Giant.

Please note the transcript has been edited for brevity and clarity.

FLG: Hello everyone and welcome to the latest Genome Giants interview. Today, we are joined by Tak Mak, who is a pioneer in the genetics of immunology and cancer. So, before we go back and take a look at your career, Tak, can you just introduce yourself and tell everyone a little bit about what you do?

Tak: My name is Tak Wah Mak. I was born in China and raised in Hong Kong. My family and I moved to the USA when I was a teenager. I enrolled at the University of Wisconsin in Madison to study engineering but discovered that I didn’t really like it that much. Instead, I completed my B.Sc. and M.Sc. in biochemistry. For my postdoctoral training, I went off to the Princess Margaret Cancer Centre in Toronto to work with Ernest McCulloch, who discovered haemopoietic stem cells. Eventually, I returned to Wisconsin to Howard Temin’s lab and learned techniques in molecular biology. Once back in Toronto, I started my own lab but at first wasn’t quite sure what to do. I took a shot at working on a particular type of leukaemia and rather serendipitously and against a stack of odds, managed to clone the gene encoding the human T cell receptor (TCR). That’s how my career got started.

FLG: If we take apart what you just said. Let’s start off with the fact that you were raised in Hong Kong. What are some of your fondest memories growing up?

Tak: Some of my fondest memories include playing soccer and table tennis as a youngster as well as serving mass in a Catholic church. I was a devoted Catholic back then. In fact, I attended the seminary for a few summers to test the idea that I would one day become a priest. I found that my Jesuit education was an enlightening experience filled with faith. The Jesuit creed reinforced my family’s teachings and taught me the importance of benevolence, fairness, and sticking to one’s principles. After I entered university, I lost that deep spiritual conviction. I found myself in an environment that was not very conducive to dwelling in a religious realm. So, of necessity, I became someone who spent more time out of the church than in it.

FLG: You said you were educated at a religious school growing up. What impact did that have on your education?

Tak: A major impact was that I was able to learn English early on because the school was staffed with Irish Jesuits. I also feel that these priests influenced my personality, my outlook on life, and my dealings with and empathy for other individuals in a positive way, although it’s difficult for me to describe a precise event or effect. Nevertheless, I’m sure my Jesuit education greatly affected how I see the world, how I treat other people, and how I see us all fitting into one society.

FLG: You mentioned that you thought you would one day become a priest, but did you ever have an interest in science growing up or did that develop later?

Tak: No, as was true for every kid in Hong Kong, our parents wanted us to go into business or become either doctors or lawyers. To enter any other profession was to fail. It was only when I went to the Midwest of the USA for university, and was pretty much on my own, that I was able to take control of my own life. Even when I was 35 years old and had already cloned the TCR and was a full professor, my mother still asked me, ‘When are you going back to medical school?’. There was certainly a lot of pressure in that direction for an extended time. It was not until later, after I was recognised internationally, that she finally acknowledged that I had not failed the family. 

FLG: What were you like growing up as a child? How have you changed as you’ve gotten older?

Tak: I was a very shy person with only a few close friends. I spent a lot of time at the church and participating in related activities. As childhood hobbies, I played soccer and marbles. I didn’t read a lot of fiction books and did not excel in reading and writing Chinese. I regret that now because I would like to know more about Chinese literature and history. I feel I should be able to explore those subjects as part of my genetic heritage and also the environment of my upbringing.

FLG: As you mentioned, you moved to the United States in the mid-1960s. What was this transition like for you?

Tak: I had no problem with this change, and, in fact, I really enjoyed it. Originally, I was supposed to attend the University of California at Berkeley, but my mother said, ‘Don’t go there, there will be a lot of anti-war (Vietnam War) activities’. I had also been accepted to the University of Wisconsin, and it had the added draw that it charged relatively cheap tuition fees, so off I went to Madison. The irony, of course, was that the students in Berkeley only threatened to bomb university buildings during their anti-war activities; the Wisconsin students, sadly, actually did it!

That being said, my own experience in Wisconsin was peaceful and very enjoyable. Madison at that time was a smaller town that exemplified the Midwest mentality. The people there treated me very well, and I felt welcome right from the start. I was never made to feel like I didn’t fit in because I was from Hong Kong.

FLG: That’s really nice! Why did you select chemical engineering specifically and then why did you then later switch your major to biochemistry?

Tak: Every year for the last few decades, the International University Mathematics Competition has been won by students from Hong Kong University. For some reason, the culture in Hong Kong makes it natural for many students to excel in mathematics and physics. Now, I’m not one of those bright lights, but several of my high school classmates were. Caltech in the USA takes in very few students, but three of my high school classmates were accepted into Caltech in one year. That says something about how Hong Kong orients itself in the spheres of mathematics and physics. In any case, I liked chemistry and my math was not too bad, so I decided to study chemical engineering at the University of Wisconsin. I was soon shocked at how poor a match this was!

In the impatience of my youth, I felt that my professors did not want to teach me what I wanted to learn. Of course, I later saw that they were obliged to drill in me facts and figures. Once, I was given a set of problems involving a lot of formulas that required me to plug in a set of 100 numbers. As was usual for me at that time, I went to the bar and played bridge before turning to assignments, only to discover that I’d run out of time to crunch all 100 numbers. I did the first three and wrote on the side of my paper, ‘If these first three are right, I do not understand why I have to do the rest of the 97’. I handed in my assignment as required and waited to see what the professor would say. The next thing I knew, I was in the Dean’s office and was told, ‘Well, Mr. Mak, we have a feeling that engineering is not your forte. Perhaps you should consider a different major, or transfer to another university’. I didn’t relish the thought of being kicked out after only a few months, so I transferred to the biochemistry department and soon was much happier.

FLG: What was your time like after that?

Tak: In the beginning, I was faced with a dilemma. My family didn’t have a lot of money and I was only given enough funds to cover my tuition for one semester. I then had to either make the money to cover my next semester, or I had to win a scholarship. Having left the engineering faculty somewhat under a cloud, a scholarship was not on the horizon. So, I first tried my hand at construction but that didn’t go very well because I weighed only 100 pounds and wasn’t very strong. I turned next to working as a gardener and also washing glassware in research facilities. One of these facilities was the laboratory of Professor Roland Rueckert, who paid me $1.25 per hour for cleaning flasks. Sadly, these stints were for only a few hours per day and didn’t generate nearly enough income for my purposes. I approached Professor Rueckert, who was a young academic born and raised in Wisconsin but educated at Berkeley, and I asked for more work. He said, ‘I have no more glassware for you to wash, but I’ll pay you $1.50 an hour to do experiments for me. And when you finish, you can wash the dishes that you make dirty for $1.25’. I said, ‘We have a deal! Let’s do experiments’, and that’s how I got started in research. Professor Rueckert was of German heritage and demanded that everything going on in his lab be very precise. I enjoyed this meticulous approach and started thinking, ‘Ah, this is how science works’.

FLG: How do you feel your time at Wisconsin shaped the rest of your career?

Tak: Obviously, leaving engineering to take up biochemistry was a major inflection point. It was Professor Rueckert who shaped my development and made sure that I started thinking in a scientific way. Roland is still alive, by the way. He retired from the university and bought himself a farm in Northern Wisconsin where’s he’s gone back to nature. Back then, the University of Wisconsin had some really prominent scientists as teaching professors, including Oliver Smithies, Hector DeLuca and Howard Temin. Just listening to these experts talking about their findings, as well as their theories and how to test them, made me more and more interested in the process of scientific inquiry. Even today, what makes me really happy is when someone makes a brand-new connection between two established concepts and generates a whole new theme of discovery.

I’ll give you an example. I was in Washington, DC recently and met with Doug Lowy, who is the Deputy Director of the National Cancer Institute in the USA. He is the researcher who was a major promoter of human papilloma virus (HPV) vaccination first for young girls and then young boys, a strategy that has greatly reduced the incidence of HPV-related cancers. At any rate, as we chatted, he told me how the E6 and E7 viral proteins from distinct variants of HPV differ between cervical cancers and oropharyngeal cancers, which are both caused by HPV infection. This is important because cervical cancers occur in women, but oropharyngeal cancers occur mostly in men, for some unknown reason. Does this mean there is a sex hormone component to HPV infection? Or are different HPV strains responsible for different cancers? Just listening to what Doug Lowy said for 10 minutes made my whole trip to Washington well worth it. The cancer research field is so broad. People have different specialities, and we have to constantly learn from each other.

FLG: You moved to Canada and did your doctorate at the University of Alberta. What was that transition like to Canada? How did your experience at this university compare?

Tak: I moved to the University of Alberta in Canada to do my PhD in the Department of Biochemistry. At that time, I was ready to start thinking on my own. My supervisor was the Chair of the department and a very busy guy. He was content to leave me to my independent notions and we made a deal. He said, ‘If you get three papers accepted by the journal Virology, then I’ll give you a PhD.’ It was my good fortune to be taken under the wings of Dennis O’Callaghan, an American postdoc from Mississippi, and Doug Scraba, a young Assistant Professor in the department. The three of us collaborated to crank out six papers in two years, and I got my Ph.D.

FLG: What was it then like being able to set up your own lab? What challenges did you face during that time?

Tak: Well, first I went to the Princess Margaret Cancer Centre in Toronto to work with Ernest McCulloch as a post-doctoral fellow,and he really influenced me as a researcher. Although McCulloch was thoroughly Canadian, he was of British heritage and relentlessly capitalised on that fact. We would get into a scientific discussion and, all of a sudden, he would answer me with a quote from Wordsworth, Shakespeare or Shelley. He was trained as a medical doctor, specialising in leukaemia, and had a philosophical approach to research. Back in the 1970s, leukaemia treatment was pretty dismal, being basically limited to chemotherapy with cytarabine (AraC). We spent many hours speculating on how the work in the lab might someday expand therapy options for this awful disease. I just loved the way Ernest was able to think so widely, what is now termed “outside of the box”.  I offer a quote from Allen Curnow, a famous New Zealand poet, who said, ‘Simply by sailing in a new direction, you could enlarge the world’. I like to think of myself on a constant sailing journey, trying every day to expand knowledge.

Following the completion of my fellowship in Toronto, I returned to Wisconsin for a short time in Howard Temin’s lab to learn the intricacies of molecular biology. There, I found that not only did I have to “think widely” but I also had to be very rigorous in terms of experimental proof. I came back to the Princess Margaret Cancer Centre in Toronto with the intention of setting up my own lab and joining the leukaemia programme. My immediate boss, Dr. McCulloch, was studying myeloid leukaemia, and the very prominent scientist Arthur Axelrad was concentrating on erythroleukemia. Other scientists at the Hospital for Sick Children a few blocks away were focussed on B cell leukaemia. There was only one leukaemia that nobody was studying – T cell leukaemia. McCulloch said to me, ‘If you want to join the leukaemia programme, you study T cell leukaemia’. And so, I studied T cell leukaemia.

FLG: What was the journey like to discovering the T cell receptor and what was it like finally realising you had found it?

Tak: I have to say, there is no doubt that both luck and serendipity were involved. I gave my first talk as an independent principal investigator at Harvard University in December of 1983. I was told by the department head that more than a dozen Harvard labs were already trying to clone TCR genes. Who was I, just over 30 years old and a very newly minted PI, to even dream of doing it? Mark Davis, who was even younger, was more committed to finding the mouse TCR gene, and his journey was more planned and deliberate than mine. What we two had in common was an approach that very few other people considered, and those who had it were not applying it to the same problems. I’m talking about the technique of subtractive molecular hybridisation.

This approach was originally used by virologists Stehelin, Varmus, Bishop and Vogt to discover the first oncogene, a milestone described in their Nature paper of 1976 (Stehelin et al. 1976). These virologists compared the Rous sarcoma virus (RSV), which causes sarcoma cancers, to the avian leukosis virus (ALV), which does not cause sarcomas. RSV has four genes – gag, pol, env and src, whereas ALV has three genes – gag, pol and env. Clearly, the virus that caused sarcomas had an extra gene. You must remember that, in those days, there was no cloning, so these researchers took the four genes of RSV and used molecular hybridisation to subtract the three genes of ALV. They ended up with the DNA sequence of src, the first oncogene.This discovery was part of the work that won Varmus and Bishop the Nobel Prize for Physiology or Medicine in 1989. For myself, I had employed molecular hybridisation techniques studying the Friend Leukaemia virus, but I wasn’t thinking about immunology at the time.

Once I had established my own lab at the Princess Margaret Cancer Centre, the first thing I wanted to do was to determine which genes guided T cells in their differentiation and functions. But how do you find those particular genes among the over 20,000 genes in the human genome? I figured that, because T cells and B cells are close cousins, I could subtract all the common genes, leaving only the much smaller number of genes specific to T cells. Of course, it was not as simple as that. In fact, our grant proposal on the subject was flatly rejected at the time. Some reviewers said, ‘This is not a project for Canada’. I thought, ‘Sorry, I’m in the wrong country’. Another said, ‘Canadians should not be looking for the TCR. Moreover, your technology may work for viruses, but it will not work for cells because the RNA would be degraded in this hybridisation over five days’. Actually, you can add phenol and preserve the hybridisation for a week, but I didn’t get the chance to argue this point. Luckily, McCulloch believed in me and my project. He went to the Hospital for Sick Children and asked Erwin Gelfand, who was the Head of the Immunology Department at the time, ‘Can you find Tak Mak some money?’. Gelfand said, ‘Who is Tak Mak?!’. McCulloch and Gelfand persuaded the Hospital for Sick Children Foundation to fund my subtraction experiments and there they were, the TCR genes as well as many other T cell-related genes, like LCK. And so, all of a sudden, the world was looking at this young man who had serendipitously cloned a human TCR gene. Meanwhile, Mark Davis had learned about subtractive hybridisation from Eric Davidson at Caltech, and he was thinking about immunology. Just as my team isolated our human gene, his group did the same for the mouse TCR beta chain gene. The two of us published back-to-back papers in 1984 on our discoveries (Hedrick et al. 1984; Yanagi et al. 1984), and folks began to say that the Holy Grail of immunology had been grasped, and that “the Hunting of the Snark” was over. The late Alan Williams wrote a News and Views article (Williams 1984) entitled ‘The T cell receptor elusive no more’ that captured the spirit of the day. It was quite something to have two near-30-year-olds, who had just secured their academic positions, making such decisive findings. It was far-fetched!

FLG: You proved them all wrong.

Tak: I couldn’t believe it all myself for a long time.

FLG: After that, institutions around the world were trying to make you offers. But why did you feel that you wanted to stay where you were in Canada?

Tak: My personal philosophy is that I should always remember to thank those who aid me and never forget their generosity. Canada is the place where my career took off, thanks to Canadian Ernest McCulloch, the Princess Margaret Hospital, and Toronto’s Hospital for Sick Children. That $30,000 provided to me for my subtraction experiments meant everything to me, and I have a strong sense of loyalty to those who truly go out of their way to help me.

FLG: No, that’s really good. I think that’s really important. You then received support from Amgen to develop the Amgen Research Institute in Toronto. This resulted in your lab pioneering the use of knockout mice. What was this journey? How did that differ to your previous T cell journey?

Tak: Amgen represents a very different world. The person who scientifically made “the Amgen years” happen was Amgen Executive Vice President of Research, Larry Souza. I still play golf with Larry when I can make it to California. Larry was educated at Berkeley and UCLA and was among the first 10 people hired by Amgen. For a period, Amgen was the world’s most successful biotech company. You have likely heard of Amgen’s first two drugs, called Epogen and Neupogen, which boost the production of red blood cells and white blood cells, respectively. These two drugs alone have generated billions of dollars in sales for Amgen. I personally believe that two people contributed prominently to Amgen’s success: the CEO and business genius George Rathmann, and the science genius Larry Souza. Larry doesn’t talk a lot, but when he does, it’s usually to tell you what you need to do next. Larry wanted me to work for Amgen and offered me carrots, but I kept procrastinating on the decision. Eventually, Larry came to Toronto with several other Amgen executives and made a deal with my late boss, Ron Buick. Amgen said it would build a research institute in Toronto if I would go on loan to California once a month for 10 years. This massive support from Amgen changed everything, such that we were able to build a cottage industry of talented scientists and churn out strain after strain of knockout mouse. All at once, we had the funding, we had the team, and we had Larry’s vision. Larry’s idea was to apply genetically engineered mouse techniques to drug development, and he had the influence and the firepower to make it work. Denosumab, Amgen’s third blockbuster drug, was a result of such mouse genetic approach.

FLG: Knockout mice have had such a big impact on the field, and they’ve led to several major breakthroughs in immunology and also in cancer. Looking back now and seeing that impact, what are your thoughts on it now? How does that compare to at the time as well?

Tak: Well, a specific area in science always has a window. When that window closes, another window opens. At the time that Amgen came to me, the window for rapid gene sequencing and knockout mouse generation was wide open. But now, almost every gene of importance has been knocked out, and the entire mouse genome has been sequenced. You move on. Mind you, these knockout mice have paved the way to new therapies that remain highly useful. For example, checkpoint blockade immunotherapy involves the administration of antibodies against CTLA-4 and PD-1, which, as we showed for CTLA-4 (Waterhouse et al. 1995), are negative regulators of T cell functions. These anti-CTLA-4 or anti-PD-1 antibodies cause some anti-tumour T cells to unleash themselves and start attacking cancer cells. Checkpoint blockade is an indescribably powerful approach that has now become the fourth pillar of cancer treatment, thanks to the hard work of my good friends Jim Allison and Tasuku Honjo. Nevertheless, there are two major issues to be resolved. First, there are still lots of cancers that don’t respond at all to this type of treatment, including pancreatic cancers, brain tumours, leukaemias and lymphomas (except Hodgkin lymphoma). Secondly, we don’t know what targets these anti-tumour T cells are attacking. The casual answer is neoantigens that are based on mutated peptides, but that is not the whole story. Right now, we don’t know exactly what these T cells are recognising as they kill. If we did, we could tailor-make for you a TCR that would allow large numbers of your T cells to focus solely on attacking your cancer.

Where we can currently refine T cell attack is in the treatment of leukaemias and lymphomas with T cells bearing chimeric antigen receptors (CAR-T cells). These T cells express a hybrid of antibody and TCR directed against a known cancer-related antigen expressed on the tumour cell surface. However, there are only so many known exterior cancer-related antigens. To target interior cancer-related antigens, you have to move on to TCR-T cell therapy.

In this approach, you have to have prior knowledge of the cancer-related intracellular proteins. Then, you have to identify TCRs that recognise known peptide/HLA combinations. To explain this last term, a TCR on a T cell only binds to a specific combination of antigenic peptides held in the binding cleft of a particular HLA molecule, and this HLA molecule has to be expressed on the surface of an antigen-presenting cell (APC). These HLA molecules vary widely in sequence and prevalence across the world’s ethnic groups, and different HLA molecules will bind different peptides from the same antigenic protein. This means that finding the exact TCR that recognises a particular peptide from a cancer-related antigen bound to a specific HLA molecule can be a tricky process. Nevertheless, it can be done and can generate powerful clinical results.

For example, as I alluded to above, almost 100% of cervical cancers are caused by HPV infection, and a key player in the infection is the viral E7 protein. Christian Hinrichs’ team recently treated 12 patients with terminal cervical or oropharyngeal carcinoma with engineered T cells expressing a single TCR targeting a particular E7 peptide bound to the HLA-A2 molecule. Amazingly, this application of TCR-T cell therapy yielded 11 clinical responses (Nagarsheth et al. 2021). Many groups are now working on similar TCR-T approaches targeting known oncogenic proteins in the context of known HLA backgrounds.

FLG: The field is evolving so rapidly! What are your current lines of cancer research?

Tak: A key thrust right now is helping Dr. Naoto Hirano, a brilliant Japanese professor who came to our institute in Toronto from Harvard, to continue his work on refining TCR-T therapies. Whereas an antibody recognises and binds to an antigen with very high affinity, the TCR’s interaction with its combined peptide-HLA antigen is shorter than a casual kiss. The few TCRs currently used in the clinic are restricted to recognising antigenic peptide bound to HLA-A2, a subtype of HLA molecule found mainly in people of European background. For TCR-T therapies that can cover a wider swath of the world’s patient population, you need to be able to isolate TCRs from T cells responding to other antigenic peptides bound to other subtypes of HLA molecules. Naoto Hirano’s lab has developed a set of artificial APCs expressing 51 different HLA molecules that will cover approximately 90% of the world’s population in the Americas, Asia and Europe. Using these artificial APCs presenting known tumour peptides on known HLA molecules, we are working on pulling out T cells expressing TCRs that recognise these structures, which are likely to be present on tumour cell surfaces. These T cells will then be grown up in culture in huge quantities and infused into the appropriate patients to shrink their cancers. This strategy has the potential to generate reagents that can be used to treat a broad range of patients.

What about oncogenes, you ask? Therapies targeting specific oncogenes have been very helpful but there appear to be few new oncogenes to be discovered. Instead, we, along with Lew Cantley and Craig Thompson, have been looking at mutations that allow cancer cells to adapt their metabolism to survive in an anti-tumour environment. We established Agios Pharmaceuticals to make a drug that inhibits the mutant forms of isocitrate dehydrogenase (IDH) that drive certain leukaemias. This drug, called ivosidenib, has now been approved for the treatment of acute myeloid leukaemia (FDA 2018). It may soon be approved for cholangiocarcinoma because the Phase III trials have been positive thus far. Although IDH mutations also occur in gliomas, it will take a while longer to figure out how to apply the same approach in these cases.

Another current focus of our group is the study of cancer cells that still manage to proliferate despite the fact that they cannot repair defects in their DNA in the usual way and so are genomically unstable. If you can find the proteins that help these cancer cells circumvent their genomic instability, and treat these cells with inhibitors blocking these proteins, you can theoretically stop these cancer cells in their tracks. We have collaborated with a group of very clever medicinal chemists to generate two such inhibitors that are now being tested in the cancer clinic, with promising results to date.

But back to your original question, which was essentially in which direction shall I sail next in the hopes of enlarging the world’s knowledge? What has piqued my scientific interest recently is the growing evidence that the brain talks to the immune system. As an illustration of this interaction, let’s consider songbirds. There are male songbirds and female songbirds of hundreds of species. However, in general, if you suppress the immune system of a young male songbird, he is limited in his singing repertoire and cannot sing songs well enough to attract a female bird when he grows up. This finding came from a UK study last year with the intriguing title: ‘Male songbirds can’t survive on good looks alone’ (Durrant 2020). Interestingly, if the immune system of a young female bird is suppressed in the same way, she is still able to grow up normally and sing her full song repertoire. We don’t yet know the cause of this difference, but the speculation is that the immune system and the brain are communicating in a fundamental fashion.

This is actually not a new idea. In 1849, a German anatomist by the name of Rudolf Wagner stimulated the peripheral nerve of a dog and found something moving in the dog’s mid-section: it was the spleen (Schaefer and Moore 1896). A couple of years later, another German anatomist by the name of Jacob Henle tried the same thing using a decapitated human. Now, the paper did not describe how he obtained the decapitated human, but he observed the same phenomenon as Wagner; that is, stimulation of the vagal nerve, which is part of the parasympathetic system, caused the spleen to react (Schaefer and Moore 1896). What is in the spleen? Large collections of various immune cells. However, if you look carefully at the spleen, thymus, and lymph nodes, you will see that they all contain nerve fibres.Why would nerve fibres need to be situated amongst immune cells?

The answer was found about 10 years ago by Kevin Tracey, a brilliant neurosurgeon in the Feinstein Institute in New York, who collaborated with us to test a counter-intuitive theory. It turns out that some subsets of T cells and B cells are able to pump out acetylcholine (Ach), which is the prototypical neurotransmitter between neurons (Rosas-Ballina et al. 2011; Reardon et al. 2013). We hypothesised that, when a nerve detects an infection in a tissue, it tells some T cells and B cells to upregulate their expression of acetylcholine transferase (ChAT), the enzyme that synthesises Ach. Cells in various organs then receive this Ach signal and take effector actions to kill the pathogen. Some folks might say this scenario is outlandish, but we showed that it isn’t.

Maureen Cox, originally from California and educated at the University of Alabama, joined my lab as a post-doctoral fellow several years ago. She came as a result of a talk I gave to her and her colleagues on potential connections between the immune system and the nervous system. To investigate our hypothesis, she deleted the gene encoding ChAT specifically in the T cells of mice, rendering these cells unable to make Ach. When she infected these mutant animals with a virus causing a chronic infection, the mice could not clear the pathogen, showing that Ach is essential for the anti-viral immune response (Cox et al. 2019). It turned out that T cell-produced Ach is necessary for the successful migration of anti-viral T cells through the endothelial cell layer into an infected tissue. This work in particular demonstrates the power of genetics. When we sent in our paper describing these results, the reviewers acknowledged that we had provided the first genetic proof that Ach is an important part of T cell function. So, by sailing in this new direction, powered by amazing collaborators and colleagues in the lab, we have enlarged our world of knowledge of the components of an effective immune response—and we had fun doing it!

FLG: That sounds really exciting! You have made several major breakthroughs in the field, I haven’t been able to list them all, but what has it been like for you experiencing such massive peaks in your career? And how do you deal with situations in your career that don’t go so well?

Tak: Being a scientist quickly accustoms you to failure. It’s part of the game. We are figuratively turning over rocks hiding secrets, but we are not going to find diamonds or gold or even iron under every stone. But once in a while, when you turn over that rock, what you find is invaluable. It may stand on its own, or it may remind you of something you noticed somewhere else, and suddenly you’ve made a novel connection between the two that may shed light on an unsolved problem. That’s worth all the time spent, and that’s what scientists were made to do.

I have a short story to illustrate the value of the observant and open mind. In 1983, the J. Paul Getty Museum in Los Angeles had just been opened. The setting of this museum is beautiful, being perched on a cliff. The museum staff wanted a key attraction that would be as spectacular as the setting. They came across a Swiss dealer selling a “kouros”, which is a statue of a naked Greek soldier from about the sixth century. The staff loved the look of this statue, so they sent an army of archaeologists, geologists, chemists and lawyers to make sure it was authentic. The statue was tested with isotopic analysis and quantification of dolomite as well as other mineral contents and certified as dating back many centuries and likely from the Thassos Acropolis region. The Getty Museum bought this kouros for just under $10 million and proudly displayed it to the public.

However, every now and then, an art expert would walk in and say to the Museum Board, ‘I looked at this kouros and was repulsed’. Another would say, ‘It looks too fresh’, and another, ‘The finger joints should look like this, not that’ or ‘the hair looks modified’. These comments, based on the observations and intuition of experts, started a whole new investigation. It turned out that the letter of support from a noted German archaeologist was faked, and that the statue had been artificially aged. The statue was removed in 2018, all thanks to the rock-turning of art experts. Scientific instinct is the same and immensely important. Perhaps you remember what the famous physicist Richard Feynman said, ‘If you are going nowhere with an old technology, having a fast technology only gets you nowhere faster’. I think that, to some extent, the same thing can happen today with data acquisition driven purely by artificial intelligence. You can give reams of data to a bioinformatics expert and he or she will give you an answer. But is that the answer which actually addresses your original question? Instinct and intuition need to play a role here.

FLG: This is true. I think intuition is so important.

Tak: Howard Temin had the most piercing intuition of any scientist I’ve had the pleasure to know. He postulated the existence of reverse transcriptase based on the results of giving actinomycin D to a cell growing RSV. Somehow, he looked at the raw data and said, against the dogma of the day, ‘There is an enzyme that takes RNA back to DNA’!

FLG: It’s a truly different way of thinking.

Tak: Often, one of my students will come to me with a list of genes determined by a bioinformatics investigation, and I will say, ‘Rank these genes in order of those we should investigate first’. The student goes off and ruminates for a while and returns with the top 25 genes and the bottom 25 genes and says, ‘I’ll study these ones’. But I say, ‘No, hold on a minute. I want you to take the first 100 and the bottom 100 and go away for a month. Read all you can about all these genes, and then come back and tell me which ones may be the most interesting biologically’.

FLG: You’re mentoring them in a good way!

Tak: Only because I have made so many mistakes myself.

FLG: How have you maintained such a passion for science? Were there any occasions where you thought about doing something else?

Tak: I was told by a friend that Chinese folks are born with guilt, and that Catholics learn it at school. I’m a Chinese Catholic so I live on guilt. My guilt drives me to try to do more. Some of my loved ones have suffered from dreadful diseases and died of cancer, and I have cursed the fact that all the research at the time couldn’t save them. The other thing that drives me is a passion for the scientific process. As the saying goes, if you are doing something you like, you don’t have to work another day in your life. How privileged we scientists are to be paid to enjoy ourselves! Of course, this life also entails failures and frustrations, but at the end of it all, it is what I want to do every single day.

FLG: If you could turn your life or your career into a book or a film, what would be the title?

Tak: “Two Swallows” 

FLG: I like that. Why would you pick that?

Tak: There was a very famous contemporary Chinese painter called Wu Guanzhong who passed away about 10 years ago at age 90. He trained at the Beaux-Arts de Paris in Paris but was Chinese to his core and so returned to China to paint its beauties. One of his best-known works is a painting of a village with a house, a tree and a river – all very simple. The painting is called ‘Two Swallows’. And you look at it and say, ‘Where are the two swallows?’. When you examine the painting more carefully, you find the swallows tucked away in a corner, almost as an afterthought. I always wanted to meet Wu Guanzhong and ask him exactly why he gave this painting the title ‘Two Swallows’ when the birds appeared to be such a minor part of the story, but I missed my chance. I’ve decided for myself that the message of this painting and its title is that, sometimes in life, small facts matter a lot, and that noticing these small facts can make a large difference in an outcome, in this case, the title of the painting.

Howard Temin noticed that RSV could not replicate in the presence of a high actinomycin D concentration that would prevent a DNA virus from replicating (Temin 1963). Since RSV is an RNA virus, where had the DNA come from? Temin concluded [as he stated in his 1975 Nobel Lecture (Temin 1975)], ‘Well, there must be an enzyme that takes RNA to DNA’. Many scientists at the time thought the theory was totally outrageous because Crick’s central dogma was that DNA went to RNA, and RNA went to protein. Temin was ridiculed and the textbooks maintained the established dogma for years. It took until 1970 for his lab and that of David Baltimore to prove the existence of reverse transcriptase. Can you imagine how you would clone a gene if you did not have reverse transcriptase? And all of this stemmed from an astute observation of a replicating virus.

FLG:  It’s so interesting how Temin discovered something so vital and yet everyone thought for years that he was wrong. When I was studying, reverse transcriptase was just a fact. I don’t know any different.

Thank you so much for joining me today, Tak. Your stories are incredible and your contributions to the field are incredible as well. So, thank you for sharing.

Tak: It’s a pleasure. I’m just so lucky to be on a small boat, trying to sail in new directions and every now and then, with the help of my colleagues, somewhat enlarge the world.

FLG: I love that. Thank you so much.


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