Comment on: A validated mathematical model of cell-mediated immune response to tumor growth.

In ref. (1), ‘‘A validated mathematical model of cell-mediated immune response to tumor growth’’, de Pillis et al. present a mathematical model describing the interactions between the immune cells, CD8 T-lymphocytes and natural killer (NK) cells. Differential equations are used to describe tumor-immune growth, response, and interaction rates. The parameters reflect general biological quantities: most values were provided by biology literature, whereas some of them were estimated using a least-squares method and validated on mice and human real data. The authors use the results of their simulations to conclude that tumor regression is more influenced by CD8 T cell activity than by NK cells. We tried to reproduce the results in ref. (1) with the same constants, but obtained different results. We explain this by the choice of initial conditions of the model. We use, as initial conditions, the healthy steady state (i.e., absence of tumor). In contrast, we could reproduce the results in ref. (1) only by taking initial conditions that were not biologically plausible. This changes the conclusion about the efficacy of NK cells.