In animal cells, the anticancer function played by plant saponins involves a complex network of molecular processes that still deserves investigation and apoptosis seems to be the outstanding pathway. An intriguing aspect of the biological activity of saponins is related to their effects on genome integrity. As demonstrated by the studies carried out in white poplar (Populus alba L., cv Villafranca) cell suspension cultures, plant cells can as well be used as a model system to unravel the molecular mechanisms activated by plant saponins. These recent studies have evidenced that animal and plant cells share common features in their response to saponins, paving the way for novel opportunities for both basic and applied research. Indeed, there is a certain interest in replacing the animal models for pharmacological research, at least when preliminary large-scale cytotoxicity tests are performed on wide collections of natural extracts and/or purified compounds. The review provides an up-date of the molecular pathways (signal transduction, antioxidant response, DNA repair) associated with plant saponin bioactivity, with an emphasis on apoptosis induced by alfalfa (Medicago sativa L.) saponins. The comparison between animal and plant cells as tools for the study of saponin bioactivity is also discussed in view of the most recent literature and innovative future applications.