We report on an observed regularity in the overall response of cell proteome under influence of different doses of a peroxisome proliferator. Our analysis for the first time demonstrates presence of hormesis at the cellular level. It is shown that despite the fact that the response of individual proteins remains unpredictable, the perturbation of proteome as a whole (measured as the average departure of protein abundances from the corresponding values of the control group) shows regularity: It initially decreases, reaches a minimum, and then increases as the concentration of the used proliferator continue to increase. The work is based on the available data of Anderson at al. on the effects of peroxisome proliferator LY171883 on protein abundances in mouse liver when administrated at different concentrations.