GRP78-Targeted HPMA Copolymer-Photosensitizer Conjugate for Hyperthermia-Induced Enhanced Uptake and Cytotoxicity in MCF-7 Breast Cancer Cells.

Photodynamic therapy (PDT) is a promising cancer treatment approach. However, the photosensitizers (PS) used for PDT are often limited by their poor solubility and selectivity for tumors. The goal of this study is to improve water solubility and delivery of the photosensitizer 2-[1-hexyloxyethyl]-2-divinyl pyropheophorbide-a (HPPH) to breast cancer cells. An N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-HPPH photosensitizer conjugate is synthesized with heat shock receptor glucose-regulated protein 78 (GRP78), targeting to GRP78 receptors of MCF-7 cells, which are upregulated under mild hyperthermia. It is found that the uptake of the GRP78 targeted pep-HPMA-HPPH copolymer conjugate in MCF-7 cells is improved through heat induction. Under mild hyperthermia the targeted copolymers are more effective compared to free HPPH. These results show potential for the utility of mild hyperthermia and copolymer delivery vehicles to enhance the efficacy of photodynamic therapy.