The Jahre Lectures 2026

Heidi M. Haikala
Finish Institute of Molecular Medicine, University of Helsinki, Finland

Cancer therapies can produce remarkable initial responses, yet treatment resistance remains one of the major obstacles to durable cancer control. Resistance is often considered a property of the cancer cell itself, but tumors are complex and dynamic ecosystems in which cancer cells continuously interact with immune cells, stromal cells and their surrounding tissue environment.

Our work aims to understand how these interactions shape treatment response and how they change under therapeutic pressure. Using lung cancer as a main model, we have studied how tumor heterogeneity and cellular plasticity allow cancer cells to survive targeted therapies, and how treatment reshapes the tumor immune microenvironment (TIME). More recently, we have combined patient samples with single-cell and spatial profiling to identify cellular states and multicellular interactions associated with response and resistance to immunotherapy.

A central challenge is to move from describing resistant tumors to experimentally testing what drives resistance and how it can be overcome. To address this, we develop patient-derived models, including organoids, intact tumor tissue cultures and tumor-on-chip systems, that preserve key components of the human tumor microenvironment and allow treatment responses to be studied functionally.

By connecting molecular and spatial observations from patients with experimentally tractable models, our goal is to identify vulnerabilities that emerge as tumors adapt to therapy and ultimately develop strategies for more durable treatment responses.

Chloé B. Steen
Department of Medical Genetics, Oslo University Hospital, Norway

A tumor can be thought of as a disrupted ecosystem; like invasive weeds in an otherwise healthy garden; where certain cells spread aggressively and take over surrounding tissues. In my work, I study these distorted cellular “ecosystems” in cancer: how different cell types interact, how rare but dangerous cell states emerge, and how specific niches support them.

To do this, I use large-scale data from individual cells and their surroundings, and develop computational methods to piece together which cells are present, what they are doing, and how they influence one another. This allows us to move beyond viewing a tumor as a single mass and instead see it as a complex community with many different “roles”, including cells that suppress the immune system, cells that help the tumor grow, and cells that may be especially important for resistance to therapy.

By mapping and decoding these ecosystems in detail, we can begin to understand which combinations of cells and signals are most harmful, and which might represent weak points in the disease. Ultimately, the goal is to translate this knowledge into more precise and effective treatments; for example, by identifying specific cell states or ecosystems that can be targeted to slow tumor growth, prevent relapse, or make existing therapies work better.

Ole Kiehn
Department of Neuroscience, University of Copenhagen, Denmark

Movement is part of most behaviors. Among movements, locomotion is one of the most fundamental motor acts and is universal to animals and humans. The motor act is organized at many levels of the nervous system, from spinal networks to brainstem pathways and higher brain areas. Yet how this organization is achieved has remained a major challenge in neuroscience. Using genetic, physiological, imaging, and circuit-intervention approaches in mice, we have been able to identify distinct neuronal populations in the spinal cord that generate the rhythm and pattern of locomotion, as well as dedicated brainstem circuits that regulate key components of locomotor behavior, including initiation, speed, turning, and arrest. The brainstem pathways are dynamically modulated and embedded within brain-wide motor networks where they act as gateways for selection of context-dependent expression of locomotion. Through the brainstem pathway we link complex brain functions that use locomotion as output in different motivational and behavioral context. Understanding such circuits in the intact nervous system provides a framework for investigating how motor control is disrupted in neurological diseases, such as Parkinson’s disease or following injury. Together these studies uncover general principles by which neuronal circuits across scales leads to coordinated movement and identify pathways that may ultimately be targeted to restore motor function.