The value of slow-burning science: an interview with Peter Friedl and Bettina Weigelin

The value of slow-burning science: an interview with Peter Friedl and Bettina Weigelin

Peter Friedl has uncovered intricate dynamics in immune cell interactions that have had immense impact on our understanding of tumour progression and cancer therapy, with his background as a clinical dermatologist driving this research towards preclinical application and, eventually, the clinic. His laboratory is based at Radboud University Medical Centre, Nijmegen, the Netherlands, where he is also chair for the Microscopical Imaging Centre. His pioneering work with advanced microscopy gained him the European Molecular Imaging Award in twenty sixteen, and he has also received the German Cancer Award in two thousand eight and the Award of the Advancement of Molecular Science in twenty fourteen, among others.

Bettina Weigelin harnesses advanced microscopy techniques to investigate the mechanisms of immunotherapy, as well as cancer resistance to this therapy. She completed her PhD and postdoctoral training in Peter Friedl's group before setting up her independent laboratory at the Werner Siemens Imaging Center, part of the Department for Preclinical Imaging and Radiopharmacy, University of Tuebingen, Germany. Her impressive research trajectory has led her to receiving the New Investigator Travel Award from the Society for Thermal Medicine and being nominated for the 'VIVA four hundred' Women in Science in twenty seventeen.

While working in Peter's laboratory, Bettina discovered an unexpected phenomenon in the interactions between cytotoxic T lymphocytes and tumour cells. They observed, in a three-dimensional cell model and in a mouse model, that when these T cells interacted with solid tumour cells, the tumour cells often survived and multiple sublethal interactions with T cells would be required for tumour cell death. This phenomenon went against scientific dogma of a mandatory one-to-one pairing between cytotoxic T cells and tumour cells and required advanced developments in microscopy techniques to unequivocally prove. Therefore, this project necessitated patience and persistence, which can be challenging in an increasingly fast-paced and pressurised academic environment. Here, Peter and Bettina provide their perspectives on this research project and how this kind of valuable research can be supported in academia in the future.

How did the project start?

Peter: The project originated from an immunity paper, which we published in two thousand, where we described that T cells engaged with dendritic cells to become activated. This work implied that T cells would acquire information from multiple dendritic cells until a certain threshold of activation was achieved. Four years later, this basic concept was also shown in vivo by the von Andrian group at Harvard, who showed that a certain type of T cell activation in the lymph node would be induced by multiple engagements with dendritic cells, followed by a more stable interaction. At that point, we thought that, because we now had the tools to visualise T cell-dendritic cell interactions, we should also look at T cell interactions with tumour cells and see how the killing process happens in a three-dimensional environment.

The first researcher to work on this in my lab was Annemiek den Boer. She generated a three-dimensional model that would allow us to visualise the killing of individual antigenic melanoma cells by T cells that carry the specific transgenic receptor for these tumour cells. We saw quite efficient killing every once in a while but, typically, we couldn't follow T cells long enough because it was a three-dimensional model, and they would move out of sight before killing the tumour cells. At some point, we modified the protocol and put the tumour cells on the bottom of the dish and collagen on top, so that the T cells would have to move through the collagen to get to the tumour cells. Using this technique, everything would happen in focus and we could monitor it by time-lapse microscopy, one cell-cell interaction to the next, to the next, to the next. We saw that the T cells sometimes killed reliably, but sometimes they didn't kill, and it would take multiple T cell interactions for the tumour cell to die. This is where Bettina's project started, more than fifteen years ago.

Bettina: Indeed, I started with the task of taking over from Annemiek, who was a postdoc in the lab. She taught me in two weeks all the models and protocols, and at the time, she mostly worked with fibroblast cell lines, which were easy to kill through T cell interactions. She also gave me the antigenic melanoma cells, but there were not very many data with that model yet. It was when we used these real tumour cells that the project started to slow down,

because we didn't see reliable killing of the tumour cells, like we did with the fibroblasts. For a very long time, I tried to understand why, by optimising the experimental conditions. That was until we started to accept that that was just the way it was, and that these sublethal interactions occur a lot more often than we expected.

Peter: So, we should put this into the context of where the field was at that time. It was known that T cells can kill B lymphoma cells, serially and effectively within minutes, but B cells are very antigenic and the immune synapses are very stable. However, in solid tumours, there were several studies published between two thousand six and two thousand eight where there was no reliable killing seen in the antigenic mouse models, even in models of B cell lymphoma. So, there was a dichotomy between in vitro concepts that were already in textbooks and the in vivo reality. Our in vitro data were much closer to the in vivo data that didn't fit with the textbooks. At this moment, we were already in trouble, because we had to do a very solid job to turn around the perception.

I don't want to say it was easy, or there weren't phases when it was frustrating, but there was always an interesting result from the experiments that kept me going