Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
CR 75th Anniversary Commentary Special Lecture We Are Standing on the Shoulders of Giants Anton Berns See related article by Olson, Cancer Res 1941;1:384-92. Being asked to write a commentary on an article published in the first volume of Cancer Research (1), celebrating its 75th anniversary, I said somewhat reluctantly "yes" after going over my other commitments. But after taking the effort to read the article by Carl Olson published in 1941 and trying to put it in the context of the time, it was the most rewarding span of time I have devoted to a commentary in quite some time. If I was the "God of Scientists," I would impose a new commandment next to the others that I had already implemented, such as complete honesty, making sure that the data in the article are rock solid, giving appropriate credit to both colleagues and competitors in the field, not claiming discoveries that are insufficiently substantiated or were already made by others, and imposing a maximum of 5 articles per year as a senior author. I would, in addition, demand that after every 10 articles published, one should write a commentary on an article published 40þ years ago and point out its relevance for the field. It would help to not only recognize the importance of the work done in the past, but also enhance our appreciation for the ingenuity and robustness of the work of our predecessors and therefore an incentive to maintain similar high standards in our research practices. Let us look at the article published by Carl Olson in the first volume of Cancer Research in 1941. No cloning, no PCR, no Eppendorf tubes, no restriction enzymes, but yes, a microscope, a shelf with chemicals, glassware, benches, a Bunsen burner, and cages with chickens, rats, and mice were probably the most critical armature. From the description of how they monitored their animals it is also evident that they handled their animals with great care without being under the scrutiny of animal right activists. The experiments conducted by Olson that focused on the propagation of lymphoid tumors by consecutive graft experiments were inspired by the problems encountered in chicken farms. With the increase in their scale, infectious diseases became a serious problem. Understanding the exact nature of the infectious agents, being either Rous Sarcoma virus, Leukosis virus, one of the other oncogenic retroviruses, or Marek disease virus was still far away, but the foundation that made it possible to characterize these "agents" was laid down in the first half of the 20th century. Some important milestone work preceded the work published by Carl Olson in 1941. Peyton Rous showed three decades earlier that a cell-free filtrate from chicken tumors could transmit sarcomas to chickens (2), the first demonstration that not only chemicals, such as tar, can cause cancer but also cell-free extracts from The Netherlands Cancer Institute, Amsterdam, the Netherlands. Note: Anton Berns is senior group leader and director emeritus of the Netherlands Cancer Institute in Amsterdam. Corresponding Author: Anton Berns, Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam, 1066 CX, Netherlands. Phone: 312-0512-1991; Fax: 312-05122011; E-mail: [email protected] doi: 10.1158/0008-5472.CAN-16-1870 Ó2016 American Association for Cancer Research. some tumors can do this. Interestingly, at that time, neither Peyton Rous nor Carl Olson seemed particularly excited by the observation that cell-free extracts rather than a cell suspension could transfer the disease, even though it yielded Rous the Nobel Prize 45 years later, but then I realized what could, overthinking what was known at the time, have been the "next experiment" to further identify such agent? Not so obvious. Furthermore, there was much disbelief among his peers that a cell-free extract could cause cancer. The transmission of disease itself was considered more relevant than whether this was achieved through a cellcontaining suspension or a cell-free extract. Cell culture was not yet established, except the temporary outgrowth of cells from the amphibian embryo in a culture as described by Ross Granville Harrison in the first decade of the last century. Biological activity could only be demonstrated in animals. So what about Olson? Carl Olson, born in 1910 in Sac City, IA, worked at the Department of Veterinary Science at Massachusetts State College. Later, he would join the Department of Veterinary Science at the University of Wisconsin where he continued work on papilloma viruses and sarcomatoid tumors. In the thirties, he became intrigued by leukosis that was ravaging chicken farms. This led to the research that he published in 1941 in Cancer Research. At that time, it was unclear how the disease was transmitted. Although several investigators had been able to propagate tumors in chickens, mostly by cell-containing or cell-free filtrates (the "agent"), this resulted in a range of pathologies, from tumors such as lymphocytoma, leukosis, erythroblastosis, and sarcoma to paralysis, the latter caused by Marek Herpes virus as was found out later. The tumor descriptions given by the different investigators were not unequivocal and created quite some confusion. In part, this was certainly due to the range of different viruses involved, each giving rise to distinct tumors. In the article published in Cancer Research, Olson describes in meticulous detail how he propagated a lymphoid tumor carried by a chicken brought to the laboratory. It did regard a crossbreed between a Rhode Island Red female and a Barred Plymouth Rock male purchased from a commercial hatchery. The "patient" was carefully followed by regularly measuring the blood count, temperature, and weight. Actually, the blood count numbers remained rather normal over time, with short episodes of deviating values. However, at the 205th day, the chicken was sacrificed after it became seriously ill and was unable to stand. A number of small gray nodules were found in the liver and spleen next to a large 4.5-cm tumor mass dorsal to the cloaca. Olson provided a detailed necropsy report. This tumor was the starting material for subsequent grafting experiments. Much care was given to assure aseptic handling of the tissue to prevent contamination. Cell suspensions were inoculated in the breast muscle of the recipient chicken of different ages. Thirty (!) consecutive passages were performed over several years. This finally resulted in 443 inoculated chickens, of which 300 showed tumor growth, 133 tumor regression, 116 only local growth, and 51 both local growth and metastasis. These were laborious experiments but did show trends that over time became significant thanks to the sheer numbers. Olson noted that the interval between passages decreased in subsequent passages, going from an average of approximately 25 days during the first www.aacrjournals.org Downloaded from cancerres.aacrjournals.org on June 14, 2017. © 2016 American Association for Cancer Research. 4307 CR 75th Anniversary Commentary 10 passages to 16 days during passage 20–30. Inoculation in older chickens showed a higher propensity of regression, probably relating to a more effective immune response. The local growth of the tumor and subsequent experiments conducted by Olson and published in 1944 (3) in a follow-up article in Cancer Research suggest that the transplanted tumor cells were expanding in the recipient chickens rather than the cells producing the "agent" that subsequently infected the host thereby giving rise to tumors of host origin. In the discussion, he pointed out: "the transmissible neoplasm is unlike any other transmissible tumor described in the chicken." When reading the article, it became evident how our way of writing articles has changed over time. Olson does give a very detailed account of his experiment, much more so than we are accustomed to today. He mentions the problem chicken farms have with disease outbreaks but does not use this as a reason why he did this experiment. He also does not elaborate on the significance of the rather endless propagation of the same cell line, and how to interpret the observation that a fraction of the chicken showed tumor regression after initial growth. But the experimental description warrants that anyone could repeat the experiment if provided with the same cell suspensions and recipient strains. The great care with which he conducted his experiments and the modesty in drawing conclusions are exemplary. The other aspect that is apparent is the patience to perform the graft experiments over such extended period. One realizes this even more acutely when reading the article he published in 1944 with the description of an additional 3 years of tumor propagation with gradually increasing aggressiveness of the tumor and higher take rate when transferred every 10 days rather than a longer time. What is the meaning of this work for us? Why is this important? Well, Olson's work is part of the broader effort to propagate tumors and cells in vivo and in vitro, thereby laying the groundwork for the identification of the "agents" that causes leukosis and sarcomas in chickens. Retroviruses and in particular the oncogenic retroviruses of chicken have been instrumental for the major advances that were made in the seventies and eighties in our understanding of the nature of cancer-causing genes. The efforts of investigators from these early days, Ellermann, Rous, Furth, Harrison, Claude, Murphy, Olson, and many others, made it possible that retroviruses were isolated and characterized. They did set the stage for the breakthroughs that followed: the overturn of the dogma that genetic instructions flow from DNA to RNA to protein with the discovery of reverse transcriptase by Temin and Baltimore, and the subsequent identification of viral oncogenes and the recognition that they originated from a cellular counterpart that can drive tumorigenesis when mutated or aberrantly expressed, another major revolution in our thinking thanks to the groundbreaking work of Varmus and Bishop. Both Temin and Baltimore as well as Varmus and Bishop received Nobel prizes for their discoveries, as did Rous. Without the work that provided the basis for virus propagation, isolation, and tissue culture techniques, the farreaching breakthrough discoveries in the 1970s and 1980s could not have been made. Applications that make a difference for human health often follow much later. Already in the fifties, the capacity to propagate cells in vitro made it possible to produce the polio vaccine and the research on retroviruses, receiving much support because of their suspected involvement in human cancer, allowed investigators to rather quickly identify HIV as the agent causing AIDS. It illustrates that "translational research" is not a recent invention. It also shows that worthwhile applications follow unexpected discoveries that are the result of curiositydriven research often performed in unrelated areas and mostly focused on learning how nature works rather than trying to make science immediately applicable—an important lesson we should keep in mind. With the knowledge of today, one might think that the experiments Olson did were simple in concept, being fully focused on tumor propagation without drawing major conclusions. However, if we try to imagine how little was known at that time, and how it did set the stage for what was going to come, our predecessors did pretty well and were as excited about their experiments as we are about ours. As Olson wrote in 1975 in a review (4) citing Claude Bernard: "Those who do not know the torment of the unknown cannot have the joy of discovery." What happened to Carl Olson? From Boston, he relocated to the veterinary institute at Wisconsin continuing work on avian leukosis and papillomaviruses. There, his laboratory discovered the bovine leukosis virus that subsequently served as a model for HIV. After his retirement in 1981, he remained active in research for many years. He received many awards for his work. He died on February 28, 2002 at the age of 91 years, leaving behind a career as an internationally respected veterinary pathologist and a pioneer in cancer research, one of the many giants on whose shoulders we stand. In writing this commentary, I was struck by the poor accessibility of the old scientific literature. In some cases, it takes a small fortune as some publishers exploit the fact that libraries did not retain their old journal volumes. This is a shame. Received July 8, 2016; accepted July 8, 2016; published OnlineFirst August 1, 2016. References 1. Olson C Jr. A transmissible lymphoid tumor of chicken. Cancer Res 1941; 1:384–92. 2. Rous P. A sarcoma of the fowl transmissible by an agent separable from the tumor cells. J Exp Med 1911;13:397–411. 4308 Cancer Res; 76(15) August 1, 2016 3. Olson C Jr. The serial passage of an avian lymphoid tumor of the chicken. Cancer Res 1944;4:707–12. 4. Olson C. Avian leukosis - historical perspectives. Avian Diseases 1975; 19:277–80. Cancer Research Downloaded from cancerres.aacrjournals.org on June 14, 2017. © 2016 American Association for Cancer Research. We Are Standing on the Shoulders of Giants Anton Berns Cancer Res 2016;76:4307-4308. Updated version Access the most recent version of this article at: http://cancerres.aacrjournals.org/content/76/15/4307 Cited articles This article cites 4 articles, 2 of which you can access for free at: http://cancerres.aacrjournals.org/content/76/15/4307.full#ref-list-1 E-mail alerts Sign up to receive free email-alerts related to this article or journal. Reprints and Subscriptions Permissions To order reprints of this article or to subscribe to the journal, contact the AACR Publications Department at [email protected]. To request permission to re-use all or part of this article, contact the AACR Publications Department at [email protected]. Downloaded from cancerres.aacrjournals.org on June 14, 2017. © 2016 American Association for Cancer Research.