Living Instruments and Theoretical Terms: Xenografts as Measurements in Cancer Research

Abstract

I discuss the relationship between theoretical terms and measuring devices using a very peculiar example from biomedical research: cancer transplantation models. I do so through two complementary comparisons. I first show how a historical case study can shed light on a similar case from contemporary biomedical research. But I also compare both to a paradigmatic case of measurement in the physical sciences -thermometrywhich reveals some of the most relevant epistemological issues. The comparison offers arguments for the recent debate on the operational definition of Cancer Stem Cells, and thereby suggests the relevance of a comparative approach in the history and philosophy of science.As I argue in the first part of this paper, so-called xenograft "models" of cancer are often used not as models in the traditional, analogical sense, but as measuring devices. This prompts the question of what it is that they measure, and of the relationship they entertain with it. To investigate these issues, I compare two cases of xenograft as measurements with the prototypical example of a measuring device: the thermometer. I rely on the work by Hasok Chang on the history and epistemology of thermometry (Chang, 2004). Behind the apparent simplicity of thermometers lies a daunting epistemological problem, which he labels "the problem of nomic measurement": in a nutshell, there are a variety of thermometers giving inconsistent (not linearly correlated) readings, and we would need to know already what temperature is in order to know which one gives the right reading. I highlight some relevant similarities between his history of thermometry and the examples I will present from cancer research. In both cases, instruments and theories have a reciprocal stabilizing role: the instruments are at the same time means subordinated to theoretical understanding, and theoretical terms are means of bridging different instrumental and operational contexts. Finally, the comparison sheds some light on a contemporary debate in cancer research.In the first part of this paper, I present the instrumental role that organisms sometimes play in biomedical research (section 1.1), and apply this concept to early xenograft models of cancer