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Obituary: Nobel Laureate Harald zur Hausen (1936–2023) - Who dedicated his life to unraveling the role of infectious agents in the pathogenesis of human cancers

2024; Elsevier BV; Volume: 202; Linguagem: Inglês

10.1016/j.ejca.2024.113586

1879-0852

Michaël Baumann, Magnus von Knebel Doeberitz,

Herpesvirus Infections and Treatments

Harald zur Hausen was born in 1936 in Gelsenkirchen as the fourth child of Manfred and Melanie zur Hausen. At an early age, he developed a deep interest in birds and other living animals and decided to become a natural scientist later in life. In 1955, he finished school and began studying medicine and biology at the universities of Bonn, Hamburg, and finally Düsseldorf. In his biology classes, he learned about lysogenic bacteriophages and their ability to reprogram the genetic information of their host bacteria. Fascinated by this principle, he developed the idea that similar mechanisms mediated by infectious agents might contribute to human disease and, in particular, cancer. This idea became the central theme of his later scientific life. After completing his medical studies, Harald zur Hausen accepted a position as a research assistant at the Institute of Medical Microbiology at the University of Düsseldorf. Harald zur Hausen remembered his period in Düsseldorf at the Institute of Microbiology as being not particularly stimulating. By chance, he learned about a job offer from Walter and Gertrud Henle in Philadelphia. The Henle's were two highly respected German virologists who had to leave Germany in 1936 because of their Jewish origin. In the mid-1960s they were looking for a young scientist willing to join their laboratory in Philadelphia. Using electron microscopy, they revealed herpes virus-like particles in cultured Burkitt's lymphoma (BL) cells that they had recently acquired from Tony Epstein [[1]zur Hausen H. Cancers in humans: a lifelong search for contributions of infectious agents, autobiographic notes.Annu Rev Virol. 2019; 6: 1-28Crossref PubMed Scopus (11) Google Scholar,[2]Epstein M.A. Henle G. Achong B.G. Barr Y.M. Morphological and biological studies on a virus in cultured lymphoblasts from Burkitt's lymphoma.J. Exp. Med. 1965; 121: 761-770Crossref PubMed Scopus (170) Google Scholar]. This finding raised Harald zur Hausen's interest in learning more about the role of this new virus in human cancer cells and he joined the Henle lab in January 1966. Upon his arrival in Philadelphia, his first interest was to foster his practical knowledge about basic molecular virology techniques. He began to work with adenovirus type 12 and its role in altering the chromosome structure of its host cell [[3]zur Hausen H. Chromosomal aberrations and cloning efficiency in adenovirus type 12-infected hamster cells.J. Virol. 1968; 2: 915-917Crossref PubMed Google Scholar]. He learned to purify viral particles by ultra-high speed density centrifugation and to label the respective nucleic acids of purified viruses as hybridization probes. In the summer of 1968, the German virologist Eberhard Wecker visited the Henle lab in Philadelphia and offered Harald zur Hausen a position as senior assistant at the newly founded Institute of Virology at the University of Würzburg in Germany. The Henle's urged Harald zur Hausen to continue with his molecular virology studies on BL cells. However, the offer from Würzburg was the chance to become a full professor in Germany. Harald zur Hausen gratefully accepted, left Philadelphia, and moved to Würzburg in 1969. While setting up his own research team in Würzburg, Harald zur Hausen began to isolate Epstein-Barr virus (EBV) particles from BL cell lines. Using the methods he had learned in Philadelphia, he labeled purified EBV-DNA and used it as a hybridization probe to search for EBV genomes in BL cell lines, which did not replicate EBV in primary BL and nasopharyngeal carcinoma tumor tissue samples [[4]zur Hausen H. Schulte-Holthausen H. Klein G. Henle W. Henle G. Clifford P. Santesson L. EBV DNA in biopsies of Burkitt tumours and anaplastic carcinomas of the nasopharynx.Nature. 1970; 228: 1056-1058Crossref PubMed Scopus (885) Google Scholar]. This work revealed the presence of persisting EBV genomes in human cancer cells for the first time, very much in analogy to the lysogenic bacteriophages that had fascinated Harald zur Hausen since his medical studies. This first major scientific success was rewarded with many high-impact publications, invitations to give important lectures, and, finally, in 1975 the Robert Koch Award, one of the most prestigious science awards in Germany. His scientific success made him well known in the German scientific community and so Harald zur Hausen was offered the chair of the Institute of Clinical Virology in Erlangen, which he happily accepted in 1972. In the late 1960s and early 1970s, a number of serological datasets suggested that herpes simplex virus type 2 (HSV-2) was a likely candidate for cervical carcinogenesis [[5]Rawls W.E. Tompkins W.A. Figueroa M.E. Melnick J.L. Herpesvirus type 2: association with carcinoma of the cervix.Science. 1968; 161: 1255-1256Crossref PubMed Scopus (182) Google Scholar,[6]Nahmias A.J. Josey W.E. Naib Z.M. Luce C.F. Guest B.A. Antibodies to Herpesvirus hominis types 1 and 2 in humans. II. Women with cervical cancer.Am. J. Epidemiol. 1970; 91: 547-552Crossref PubMed Scopus (185) Google Scholar]. Thus, Harald zur Hausen and his colleagues attempted to detect the HSV-2 DNA in cervical carcinoma biopsies using the described hybridization techniques, but they consistently failed [[7]zur Hausen H. Schulte-Holthausen H. Wolf H. Dorries K. Egger H. Attempts to detect virus-specific DNA in human tumors. II. Nucleic acid hybridizations with complementary RNA of human herpes group viruses.Int. J. Cancer. 1974; 13: 657-664Crossref PubMed Scopus (80) Google Scholar]. While still in Philadelphia, Harald zur Hausen became aware of a review article with a focus on human genital warts which rarely transform into squamous cell carcinomas [[1]zur Hausen H. Cancers in humans: a lifelong search for contributions of infectious agents, autobiographic notes.Annu Rev Virol. 2019; 6: 1-28Crossref PubMed Scopus (11) Google Scholar]. At that time, the human wart virus was not at all the focus of scientific attention, but Harald zur Hausen recalled the observation by Domenico Rigoni-Stern, an early Italian pathologist, that cervical cancer was linked to the number of sexual contacts, suggesting a transmissible infectious cause. Moreover, Harald zur Hausen was aware that Francis Peyton Rous had previously observed that skin cancer in rabbits could be caused by distinct rabbit papillomaviruses. Taken together, these reports led Harald zur Hausen to believe that persistent hidden papillomavirus infections might play a major role in the pathogenesis of cervical cancer [[8]zur Hausen H. Condylomata acuminata and human genital cancer.Cancer Res. 1976; 36: 794PubMed Google Scholar]. His new position as head of the Institute of Clinical Virology in Erlangen provided him the ideal opportunity to start unraveling this scientific mystery. He began to collect surgically removed wart tissue and started to purify papillomavirus particles using cesium gradient density ultra-centrifugation [[9]Gissmann L. Pfister H. Zur Hausen H. Human papilloma viruses (HPV): characterization of four different isolates.Virology. 1977; 76: 569-580Crossref PubMed Scopus (193) Google Scholar]. DNA extracted from these virus particles was then used as hybridization probes to detect related nucleic acids in plantar wart samples. However, the attempt to detect these viruses in cervical cancer or genital wart samples consistently failed. Nevertheless, in genital warts, a few viral particles resembling papillomaviruses were detectable by electron microscopy. This finding suggested the existence of several distinct types of papilloma viruses which might be related but were still so different that their nucleic acids did not hybridize, at least not under the stringency conditions used. Together with Georg Bornkamm, who had joined Harald zur Hausen's group in Erlangen, they prepared radioactively labeled complementary RNA copies (cRNAs) of the isolated wart virus DNA [[10]zur Hausen H. Meinhof W. Scheiber W. Bornkamm G.W. Attempts to detect virus-secific DNA in human tumors. I. Nucleic acid hybridizations with complementary RNA of human wart virus.Int. J. Cancer. 1974; 13: 650-656Crossref PubMed Scopus (192) Google Scholar]. These probes hybridized to samples derived from wart viruses and a few cutaneous warts. However, genital warts and many of the cutaneous warts remained completely negative, supporting the idea that apparently heterogeneous wart virus types must exist. That same year, Harald zur Hausen was offered a professorship for virology at the Faculty of Medicine in Freiburg along with more space and more positions to expand his group. He accepted. Georg Bornkamm, Herbert Pfister, Lutz Gissmann, and others joined him. In Freiburg, Lutz Gissmann finally succeeded to isolate viral DNA from a genital wart that differed from other wart virus genomes isolated previously. In 1980, biologist Ethel-Michele de Villiers, who later became Harald zur Hausen's wife and lifelong scientific companion, joined the group. As zur Hausen wrote in Annual Review of Virology, she influenced and inspired his life like no other person [[1]zur Hausen H. Cancers in humans: a lifelong search for contributions of infectious agents, autobiographic notes.Annu Rev Virol. 2019; 6: 1-28Crossref PubMed Scopus (11) Google Scholar]. Ethel-Michele de Villiers and Lutz Gissmann successfully cloned the viral genome isolated from a genital wart, finally referred to as human papillomavirus (HPV) type 6 [[11]de Villiers E.M. Gissmann L. zur Hausen H. Molecular cloning of viral DNA from human genital warts.J. Virol. 1981; 40: 932-935Crossref PubMed Scopus (248) Google Scholar]. Further research using this viral genome as a molecular hybridization probe revealed related sequences in laryngeal papillomas as well [[12]Gissmann L. Diehl V. Schultz-Coulon H.J. zur Hausen H. Molecular cloning and characterization of human papilloma virus DNA derived from a laryngeal papilloma.J. Virol. 1982; 44: 393-400Crossref PubMed Scopus (0) Google Scholar]. However, much to the great disappointment of the group, it was not found in cervical cancer biopsies. The new laryngeal papilloma virus was classified as HPV type 11. In further experiments, the group now used HPV 11 as a hybridization probe and discovered very faint bands in some DNA samples isolated from cervical cancer biopsies. In 1980, Matthias Dürst and Michael Boshart, two doctoral students at this time, succeeded in cloning these sequences together with Lutz Gissmann, which were assigned as HPV 16 and HPV 18 [[13]Durst M. Gissmann L. Ikenberg H. zur Hausen H. A papillomavirus DNA from a cervical carcinoma and its prevalence in cancer biopsy samples from different geographic regions.Proc. Natl. Acad. Sci. U.S.A. 1983; 80: 3812-3815Crossref PubMed Scopus (1719) Google Scholar,[14]Boshart M. Gissmann L. Ikenberg H. Kleinheinz A. Scheurlen W. zur Hausen H. A new type of papillomavirus DNA, its presence in genital cancer biopsies and in cell lines derived from cervical cancer.EMBO J. 1984; 3: 1151-1157Crossref PubMed Scopus (1065) Google Scholar]. This was the great breakthrough of the zur Hausen group as it rapidly became clear that these viral sequences can be found in the majority of cervical and other anogenital cancers. The growing scientific reputation of Harald zur Hausen made him eligible for the position of the Scientific Director of the German Cancer Research Center (DKFZ) in Heidelberg. The DKFZ was founded in 1964 by the famous surgeon Karl-Heinrich Bauer to concentrate scientific research on cancer in one large center. Fifteen years after its foundation, the DKFZ was suffering under sub-optimal structures and inter-organizational disputes. The center urgently needed a new scientific leader with a high international reputation and a clear vision of how to restructure the organization. Harald zur Hausen was exactly the right person to take on this responsibility. Over the next 20 years he guided the DKFZ into one of the world's top renowned scientific research institutions. In 1983, Harald zur Hausen moved to Heidelberg with several members of his Freiburg team, including Ethel-Michele de Villiers, Lutz Gissmann, Matthias Dürst and Elisabeth Schwarz. They continued with their active research tasks initiated in Freiburg and Harald zur Hausen spent at least 1 h in the lab every morning at 8 am. to discuss the ongoing projects and experimental results with his team. Elisabeth Schwarz, together with Lutz Gissmann and other colleagues, showed that the HPV 16 and 18 genomes were integrated into the host cell chromosomes of most cervical cancer cells. Only two small HPV-encoded genes, E6 and E7, were regularly expressed in cancer cells, while the rest of the HPV genomes were either deleted or functionally inactivated by the integration process [[15]Schwarz E. Freese U.K. Gissmann L. Mayer W. Roggenbuck B. Stremlau A. zur Hausen H. Structure and transcription of human papillomavirus sequences in cervical carcinoma cells.Nature. 1985; 314: 111-114Crossref PubMed Scopus (1214) Google Scholar]. Thus, these two tiny viral genes appeared to be the main driver genes for initiating and maintaining cervical cancer growth. This hypothesis was rapidly validated by further experiments showing that normal human foreskin epithelial cells could be immortalized by the expression of the E6-E7 genes [[16]Durst M. Dzarlieva-Petrusevska R.T. Boukamp P. Fusenig N.E. Gissmann L. Molecular and cytogenetic analysis of immortalized human primary keratinocytes obtained after transfection with human papillomavirus type 16 DNA.Oncogene. 1987; 1: 251-256PubMed Google Scholar]. Furthermore, the expression of antisense mRNA molecules specifically suppressed their translation resulting in cell growth arrest of cervical carcinoma cells [[17]von Knebel Doeberitz M. Oltersdorf T. Schwarz E. Gissmann L. Correlation of modified human papilloma virus early gene expression with altered growth properties in C4-1 cervical carcinoma cells.Cancer Res. 1988; 48: 3780-3786PubMed Google Scholar]. With these findings by Harald zur Hausen's group, it became clear that: (1) HPV genomes are regularly present in cervical cancer cells, (2) only two genes of the HPV genomes are regularly expressed in the cancer cells, (3) that these have transforming activities to immortalize primary epithelial cells, and (4) that the inhibition of their expression results in the loss of the neoplastic growth properties of the respective tumor cells. Thus, HPVs act as major human carcinogens. Harald zur Hausen's initial suspicion during his early medical studies that latent virus infections may substantially contribute to human carcinogenesis thus turned out to be true (reviewed by himself in [[18]zur Hausen H. Papillomaviruses and cancer: from basic studies to clinical application.Nat. Rev. Cancer. 2002; 2: 342-350Crossref PubMed Scopus (3237) Google Scholar]). The best way to prevent cancer caused by a virus infection is to prevent the primary infection with a vaccine. Based on the fundamental work of Harald zur Hausen's group in Heidelberg, this concept stimulated various scientists to think about designing vaccines against the cancer-causing HPV types. In Heidelberg, it was again Lutz Gissmann who pushed this concept forward in the early 1990s (reviewed in [[19]Muller M. Gissmann L. A long way: history of the prophylactic papillomavirus vaccine.Dis. Markers. 2007; 23: 331-336Crossref PubMed Scopus (19) Google Scholar]). Harald zur Hausen's group expressed the viral L1 gene encoding the major HPV capsid proteins in pro- and eukaryotic expression systems and observed the formation of "viral-like particles" (VLPs) that self-assembled into capsid structures resembling the full viral capsids of HPVs. This early work by key scientists in Harald zur Hausen's group finally became the basis for the HPV-vaccines. Many scientists around the world joined this field and contributed substantially in successfully developing this field of virology. Finally, this research allowed the development of vaccines that are now available globally to prevent cervical- and other HPV-associated cancers. Thanks to Harald zur Hausen's visionary concepts, these vaccines could prevent approximately 700,000 HPV-associated cancers that occur each year worldwide [[20]de Martel C. Georges D. Bray F. Ferlay J. Clifford G.M. Global burden of cancer attributable to infections in 2018: a worldwide incidence analysis.Lancet Global Health. 2020; 8: e180-e190Abstract Full Text Full Text PDF PubMed Scopus (997) Google Scholar]. The World Health Organization (WHO) has thus called for the eradication of cervical cancer worldwide through population-wide HPV vaccination. In 2008, Harald zur Hausen was awarded one half of the Nobel Prize in Physiology or Medicine for these outstanding achievements – the other half went to the French virologists Luc Montagnier and Françoise Barré-Sinoussi, who discovered the HI virus. Zur Hausen also received almost 40 honorary doctorates and numerous honorary professorships, as well as the Grand Cross of Merit with Star of the Order of Merit of the Federal Republic of Germany. Among the numerous other awards zur Hausen received during his lifetime, the Robert Koch Prize, the Charles S. Mott Prize of the General Motors Cancer Foundation, the Federation of the European Cancer Society's Clinical Research Prize, the Paul Ehrlich and Ludwig Darmstädter Prize, the Prince Mahidol Award, the Raymond Bourgine Award, the Coley Award, the Life Science Achievement Award of the American Association for Cancer Research, and the German Cancer Aid Prize are mentioned here as examples. Zur Hausen was a member of numerous national and international scholarly societies and boards of research institutions. These include the German Academy of Sciences Leopoldina – National Academy of Sciences, the American Philosophical Society, the National Academy of Sciences (USA), the National Science Transfer and Development Agency (Thailand), the Polish Academy of Sciences, the National Academy of Medicine of Venezuela, the Institute of Medicine of the National Academy of Sciences (USA), the Ludwig Institute for Cancer Research (USA), the Human Genome Organization (HUGO), and the European Molecular Biology Organization (EMBO). After Harald zur Hausen was awarded with the Nobel Prize, together with his wife Ethel-Michele de Villiers, he dedicated most of his life as Professor emeritus to the identification and characterization of so-called Bovine-Meat and Milk Factors (BMMFs), small plasmid-like DNA molecules suspected of indirectly triggering colon and other cancers (reviewed in [[21]de Villiers E.M. Zur Hausen H. Bovine Meat and Milk Factors (BMMFs): Their Proposed Role in Common Human Cancers and Type 2 Diabetes Mellitus.Cancers. 2021; 13Crossref Scopus (9) Google Scholar]). He was convinced that these newly discovered agents might play a tremendous role in even more diseases beyond cancer. Unfortunately, he was unable to complete this project. Harald zur Hausen passed away in Heidelberg on May 29, 2023, at the age of 87. It is fascinating that Harald zur Hausen's early idea that human cancers might be caused by "parasitic genes" introduced by infectious pathogens into normal human cells turned out to be true. His lifelong persistence to follow this idea finally made it possible that vaccines against this major global cause of cervical and other HPV-caused cancers are now available. He summarized his personal reflections about his scientific career in 2019 [[1]zur Hausen H. Cancers in humans: a lifelong search for contributions of infectious agents, autobiographic notes.Annu Rev Virol. 2019; 6: 1-28Crossref PubMed Scopus (11) Google Scholar]. Harald zur Hausen's mindset was characterized by an extremely rational logic. He wanted to fully understand a problem first before coming to a conclusion. This mindset was the reason he became the exceptional scientist that he was, and which has helped save the lives of millions of people around the world. With this attitude and with his strong management skills during his long years as Chairman of the Management Board and Scientific Director, Harald zur Hausen led the DKFZ from a troubled beginning to the globally recognized research institute that it is today. He was never loud or disruptive, but rather exuded a strong, natural authority. Harald zur Hausen will forever remain in our memories as a great role model due to his outstanding intellect, his natural authority, and his enormous scientific creativity and rigor.