A metaphor is a figure of speech that describes a subject by comparing it to another otherwise unrelated object. In addition to their use as a figure of style in speech and writing, metaphors are very useful to help us understand complex subject matters.
What does a metaphor do? Basically we try to explain something by evoking familiar images of other things; sometimes we even invent these images of simple familiar things, in order to help ourselves grasp some meaning of complex, difficult material we need to deal with. I believe that the meaning of certain diverse, and complex concepts can be grasped only with the help of metaphors.
Cancer is a set of very similar yet different complex diseases and a complex biological system. War and battle metaphors stand out when we look at cancer, the diseases. These metaphors have been extensively discussed (see here or here). On the one hand, these metaphors should help patients to confront the physical and psychological ordeals they need to go through. On the other hand, it is the aim of researchers to achieve an understanding of the system deep enough to assist them in devising strategies to cure and prevent the diseases summarised as cancer.
When researchers try to understand and describe cancer, they have to deal with a challenge of communication: instead of one description, that gives a specific understanding of cancer we end up with a collection of metaphors related to cancer. In a recent BioEssays paper, Solé et al. review the many-sided views of cancer going from ecological systems to swarms. They focus on their own perspective of a cancer cell: a molecular network operating in an optimal instability level. Molecular networks are the Ace of metaphors in describing biological complex systems; their fundamental assumption is that one can describe the biological system, i.e. the cell, in terms of its molecular components and the relationships between the components of the network. Networks show emergent properties that are correlated with the behaviour of the cell.
The genetic networks in cancer cells considered by Solé et al. are reduced version of the genetic networks in healthy cells. Cancer gets rid of many network components which keep healthy cells living and working together “giving place to minimal set of intracellular components able to operate in a robust manner under noisy conditions”. In this sense, cancer cells reduce their complexity and become individuals in competition for rapid population growth rather than parts of a team working together: “cancer cells [revert] to unicellular selfishness, as a major transition from a cohesive system to individuality”. However, this involves a loss of stability that would threaten the cancer cell’s survival. Thus ,the population of cancer cells thrive by getting close to an optimal instability level in which cell proliferation is maximised but not enough to trigger the mechanisms of cell degradation and cancer death.
What is the benefit of the idea posed by Solé et al. of a minimal cancer network devoted to self-replication? It offers several testable hypotheses that would define a robust and useful metaphor of cancer, the system. One that could guide us through the path to reduce the devastation caused by cancer, the diseases. However, it is important to keep in mind that the “minimal cancer network” is just a metaphor (although a very useful one) that do not provide a complete understanding of cancer.
Solé RV et al. Can a minimal replicating construct be identified as the embodiment of cancer? BioEssays 36: 503–12 2014 DOI: 10.1002/bies.201300098