Extracorporeal Photo-Immunotherapy for Circulating Tumor Cells

It is well established that metastasis through the circulatory system is primarily caused by circulating tumor cells (CTCs). In this preliminary effort, we report an approach to eliminate circulating tumor cells from the blood stream by flowing the blood though an extracorporeal tube and applying photodynamic therapy (PDT). Chlorin e6 (Ce6), a photosensitizer, was conjugated to CD44 antibody in order to target PC-3, a prostate cancer cell line. PC-3 cells were successfully stained by the Ce6-CD44 antibody conjugate. PDT was performed on whole blood spiked with stained PC-3 cells. As the blood circulated through a thin transparent medical tube, it was exposed to light of 660 nm wavelength generated by an LED array. An exposure of two minutes was sufficient to achieve selective cancer cell necrosis. In comparison, to PDT of cells growing inside a tissue culture, the PDT on thin tube exhibited significantly enhanced efficiency in cell killing, by minimizing light attenuation by blood. It suggests a new extracorporeal methodology of PDT for treating CTCs as well as other hematological pathogens.