It is with sadness and pride that we remember the scientific accomplishments of Dennis Leeper. Dennis attended the University of Iowa where he received a Bachelor’s degree in Zoology in 1964. He went on to receive a PhD in Radiation Biology from the same University, under the mentorship of Titus Evans, a pioneer in radiobiology. Following completion of his thesis in 1969, Dennis went to Colorado State University for his post-doctoral fellowship, under the mentorship of William C. Dewey. Dr. Dewey has been widely recognized for his scientific leadership and mentoring in the fields of radiation biology and hyperthermia. So, it was under Dr. Dewey that Dennis developed interests and passion for studies in basic and translational aspects of hyperthermia as well as in mentoring.
Upon completion of his postdoctoral position, Dennis was recruited to Thomas Jefferson University, where he rose in the Academic ranks from an Assistant Professor in 1970 to Full Professor and Division Director of Experimental Radiation Oncology in 1975. By 2009, Dennis built the Division from his single laboratory to a total of 8 full faculty members. Along the way, Dennis became quite involved with the RTOG, serving for many years on the Human Subjects Committee. Dr. Leeper’s Department Chair, Simon Kramer, was the RTOG founding director.
Dennis published well over 170 peer reviewed publications, which have been cited nearly 5000 times. The majority of these publications focused on aspects of thermal biology. The subject that Dennis was most passionate about was developing methods to enhance thermal sensitivity of cancer cells by reducing their pH. His most highly cited paper was a clinical study showing that tumors with low pH are more sensitive than tumors with a higher pH to the combination of heat and radiation. Dennis received several R01 grants and a long-standing P01 grant that focused on methods to achieve pH reduction. His most recent collaboration, which Dennis pursued until his own cancer diagnosis, was conducted in collaboration with Dr. Glickson at the University of Pennsylvania. They investigated the idea of using lonidamine, a novel inhibitor of mitochondrial complex II and lactate transporters as a means to reduce pH. They had clear ambitions to carry this drug forward into human clinical trials. It is hoped that this work will continue, to complete Dennis’ and Dr. Glickson’s ambition. Importantly, enhanced local tumor control using this approach could improve treatment outcomes for many cancer patients.
Dennis was passionate about mentoring. This is reflected by his long-term leadership of an NIH T32 training grant and his participation in NIH training grant study sections. Dennis’ first graduate student, Kurt Henle, joined the faculty at the University of Arkansas, where he rose to Full Professor. Andrew Milligan joined the faculty at the University of Toledo, but then went into medical device development. This culminated in the long-term success of Bionix™, a medical device corporation. Several of Dennis’ post-doctoral fellows have had long term success in academics and industry, including Bruce Kimler (University of Kansas), Roy Rowley (University of Utah), Michael O’Hara (FDA), Kayihan Engin, MD (Medicana Bursa, Radiation Oncologist, Turkey), and Randy Burd (Arizona State University). In many ways, one’s legacy as a mentor is the most important thing that we can do as academics. Dennis was a master mentor.
Having said all of these positive things about Dennis, what else is there to say? Historically, Dennis was the driving force underlying the foundation of the Society for Thermal Medicine (previously the North American Hyperthermia Group). Dennis served as the organizer of the Hyperthermia working group within the Radiation Research Society. Largely because of his vision and leadership, those involved in this burgeoning field recognized the need to break away from RRS and form an independent society. Dennis drove this process over 5 years, by organizing the thought leaders and creating a pathway for becoming independent. Without Dennis’ vision and drive, it is likely that STM would not have been founded. Dennis also recognized the importance of international cooperation. He organized an important scientific conference with leaders in China in 1988. This meeting served as a catalyst for cooperation between many participants. In recognition of his scientific accomplishments and his impact on the field, Dennis was given the Eugene Robinson and the BSD Awards by the STM and the European Society for Hyperthermic Oncology.
Dennis’ passion was to make sure that the history of the Society was documented. As such, Dennis served as the Chair of the History Committee for 35 years. I am proud to say that we were able to transfer his entire archive to the STM administration this past summer.
In conclusion, Dennis was a scientist with extraordinary vision, creativity and enthusiasm. He never lost this, even during his fight with cancer. I am sure that the momentum that he started in STM will continue for many years to come.
Dennis is survived by his wife, Mardys, seven children, 11 grandchildren and 3 great grandchildren. Details of his personal obituary can be found at the following website, where tributes and donations in his memory can be made:
Correction Statement
This article was originally published with errors, which have now been corrected in the online version. Please see Correction (http://dx.doi.org/10.1080/02656736.2024.2307677).