Hypoxia-Inducible Factor-1α-Activated Protein Switch Based on Allosteric Self-Splicing Reduces Nonspecific Cytotoxicity of Pharmaceutical Drugs.

Protein-based therapeutic agents currently used for targeted tumor therapy exhibit limited penetrability, nonspecific toxicity, and a short circulation half-life. Although targeting cell surface receptors improves cancer selectivity, the receptors are also slightly expressed in normal cells; consequently, the nonspecific toxicity of recombinant protein-based therapeutic agents has not been eliminated. In this study, an allosteric-regulated protein switch was designed that achieved cytoplasmic reorganization of engineered immunotoxins in tumor cells via interactions between allosteric self-splicing elements and cancer markers. It can target the accumulated HIF-1α in hypoxic cancer cells and undergo allosteric activation, and the splicing products were present in hypoxic cancer cells but were absent in normoxic cells, selectively killing tumor cells and reducing nonspecific toxicity to normal cells. The engineered pro-protein provides a platform for targeted therapy of tumors while offering a novel universal strategy for combining the activation of therapeutic functions with specific cancer markers. The allosteric self-splicing element is a powerful tool that significantly reduces the nonspecific cytotoxicity of therapeutic proteins.