  In here presented in silico study we suggest a way how to implement the
evolutionary principles into anti-cancer therapy design. We hypothesize that
instead of its ongoing supervised adaptation, the therapy may be constructed as
a self-sustaining evolutionary process in a dynamic fitness landscape
established implicitly by evolving cancer cells, microenvironment and the
therapy itself. For these purposes, we replace a unified therapy with the
`therapy species', which is a population of heterogeneous elementary therapies,
and propose a way how to turn the toxicity of the elementary therapy into its
fitness in a way conforming to evolutionary causation. As a result, not only
the therapies govern the evolution of different cell phenotypes, but the cells'
resistances govern the evolution of the therapies as well. We illustrate the
approach by the minimalistic ad hoc evolutionary model. Its results indicate
that the resistant cells could bias the evolution towards more toxic elementary
therapies by inhibiting the less toxic ones. As the evolutionary causation of
cancer drug resistance has been intensively studied for a few decades, we refer
to cancer as a special case to illustrate purely theoretical analysis.
