In this article we provide an introduction to Pierre’s contributions in some topics, including discrete population dynamics, integrated semigroup theory and abstract Cauchy problems with nondense domain, traveling waves in biological systems, uniform persistence and global attractors, cell-to-cell P-glycoprotein transfer in breast cancers, transfer problems in population dynamics and economics, and modeling of various epidemic problems, in particular his recent and extensive work on modeling COVID-19. The gene discussed is ABCB1; the disease is breast carcinoma.