Azulitox—A Pseudomonas aeruginosa P28-Derived Cancer-Cell-Specific Protein Photosensitizer

Abstract

Azulitox as a new cancer cell specific and phototoxic fusion polypeptide was generated and is composed of a photosensitizer domain and the cell-penetrating peptide P28. The photosensitizer domain (EcFbFP) was derived from a bacterial blue light receptor, which belongs to the family of light-oxygen-voltage-proteins and produces reactive oxygen species (ROS) upon excitation. P28 is derived from the cupredoxin protein azurin that is known to specifically penetrate cancer cells and bind to tumor suppressor protein p53. We show that the P28 domain specifically directs and translocates the fused photosensitizer into cancer cells. Under blue-light illumination, Azulitox significantly induced cytotoxicity. Compared to the extracellular application of EcFbFP, Azulitox caused death of about 90 % of cells as monitored by flow cytometry, which also directly correlated with the amount of ROS produced in the cells. Azulitox may pave new avenues towards targeted polypeptide-photosensitizer based photodynamic therapies with reduced systemic toxicity compared to conventional photosensitizers.

Cell-Penetrating Peptides (CPPs) as Therapeutic and Diagnostic Agents for Cancer

“…A CPP, p28, has been found to have an ability of cancer preferential entry [ 59 , 60 , 61 , 62 , 63 , 64 , 76 , 77 , 78 ]. p28 is an anionic peptide made up of 28 amino acid residues (LSTAADMQGWTDGMASGLDKDYLKPDD) [ 65 , 66 , 79 , 80 , 81 , 82 ]. Specifically, the residues between Leu 50 -Asp 77 within a protein known as azurin that are secreted by an opportunistic pathogen, Pseudomonas aeruginosa [ 67 , 68 , 83 ].…”