Protein engineering is an emerging area that has expanded the understanding in the art of protein folding and laid the groundwork for the creation of unprecedented structures with unique functions. The first native-like pore-forming protein, small globular protein (SGP), has previously been designed. It has now been discovered that this artificially engineered protein, and analogs and homologs thereof, have membrane-disrupting properties and anti-tumor activity in several cancer animal models. A mechanism for the selectivity of SGP toward cell membranes in tumors is proposed and validated herein, thereby confirming the proposed mechanism of action. Thus, SGP is established herein as the prototype for a new class of artificial proteins designed for therapeutic applications.