First, philosophy offers conceptual clarification. Conceptual clarifications not only improve the precision and utility of scientific terms but also lead to novel experimental investigations because the choice of a given conceptual framework strongly constrains how experiments are conceived.
The definition of stem cells is a prime example. Philosophy has a long tradition of investigating properties, and the tools in use in this tradition have recently been applied to describe “stemness,” the property that defines stem cells. One of us has shown that four different kinds of properties exist under the guise of stemness in current scientific knowledge (1). Depending on the type of tissue, stemness can be a categorical property (an intrinsic property of the stem cell, independent of its environment), a dispositional property (an intrinsic property of the stem cell that is controlled by the microenvironment), a relational property (an extrinsic property that can be conferred to non–stem cells by the microenvironment), or a systemic property (a property that is maintained and controlled at the level of the entire cell population).
Stem cell and cancer biology researcher Hans Clevers notes that this philosophical analysis highlights important semantic and conceptual problems in oncology and stem cell biology; he also suggests this analysis is readily applicable to experimentation (2). Indeed, beyond conceptual clarification, this philosophical work has real-world applications as illustrated by the case of cancer stem cells in oncology.
Research aimed at developing drugs targeting either the cancer stem cells or their microenvironment actually rely on different kinds of stemness and are thus likely to have different rates of success depending on cancer type (1). Moreover, they might not cover all cancer types because current therapeutic strategies do not take into account the systemic definition of stemness. Determining the kind of stemness found in each tissue and cancer is thus useful to direct the development and choice of anticancer therapies. In practice, this framework has led to the investigation of cancer therapies that combine the targeting of intrinsic cancer stem cell properties, their microenvironment, and immune checkpoints to cover all possible kinds of stemness (3).
Furthermore, this philosophical framework recently has been applied to another field, the study of organoids. In a systemic review of experimental data on organoids from various sources, Picollet-D’hahan et al. (4) characterized the ability to form organoids as a dispositional property. They could then argue that to increase the efficiency and reproducibility of organoid production, a major current challenge in the field, researchers need a better understanding of the intrinsic part of the dispositional property that is influenced by the microenvironment. To discriminate the intrinsic features of cells that have such a disposition, this group is now developing high-throughput functional genomic methods, enabling an investigation of the role of virtually every human gene in organoid formation.