Photodynamic intracellular acidification therapy induces cancer cell death

Recently, this lab has developed a technique of uncaging hydrogen ions from 2-nitrobenzaldehyde (NBA) by photoactivation with 405 nm wavelength light. Photo uncaging hydrogen ions intracellularly causes accurate, controllable shifts in intracellular pH (pHi). Previous studies in this lab revealed this technique is capable of causing significant cell death in 85% of PC12 cells and 98% of MCF-7 cells in vitro over 2 hours. It is important to determine if the increased ability to shuttle hydrogen ions via NHE1 in the aggressive triple negative breast cancer cell line, MDA-MB-231, impacts the effectiveness of photo uncaging intracellular pH manipulation. In this study, a calibration curve was created to correlate pHi to fluorescence values of the ratiometric pH-sensitive dye, (5-(and-6)-Carboxy-2',7'-Dichlorofluorescein Diacetate) (DCFDA) to make accurate measurements of pHi in MDA-MB-231 cells. Measurements of decreases in pHi were made with DCFDA before and after intracellular acidification, and significant cell death was quantified in vitro . An in vivo xenograft tumor model using MDA-MB-231 cells in nude mice was created. With a single treatment of our intracellular acidification photodynamic therapy, significant reduction in tumor volume was accomplished followed by an inhibition of tumor growth, and a doubling of survival. The aims of this project represent the next logical steps toward investigating the clinical and commercial relevance of the patented photodynamic intracellular acidosis technique, previously studied by this lab.