A NIR-responsive indocyanine green-genistein nanoformulation to control the polycomb epigenetic machinery for the efficient combinatorial photo/chemotherapy of glioblastoma

Abstract

Combinatorial photodynamics and chemotherapy have drawn enormous attention as therapeutic modalities via precise stimuli-responsive drug delivery for glioblastoma, which can overcome the limitations associated with conventional therapies. Herein, we have prepared an indocyanine green tagged, genistein encapsulated casein nanoformulation (ICG-Gen@CasNPs) that exhibits the near infra-red region responsive controlled release of genistein and enhanced cellular uptake in the human glioblastoma monolayer and a three-dimensional raft culture model via the enhanced retention effect. ICG-Gen@CasNPs, with the integrated photosensitizer indocyanine green within the nanoformulation, triggered oxidative stress, activating the apoptosis cascade, promoting cell cycle arrest and damaging the mitochondrial membrane potential, collectively directing glioblastoma cell death. The suppression of the polycomb group of proteins in the glioblastoma upon ICG-Gen@CasNPs/NIR exposure revealed the involvement of the epigenetic repression complex machinery in the regulation. Furthermore, ICG-Gen@CasNPs/PDT/PTT directed ubiquitination and proteasomal degradation of EZH2 and BMI1 indicates the implication of the polycomb in conferring glioblastoma survival. The increased activation of the apoptotic pathways and the generation of cellular reactive oxygen species upon inhibiting the expression of EZH2 and BMI1 strengthen our observations. It is worth noting that ICG-Gen@CasNPs robustly accumulated in the brain after crossing the blood–brain barrier, which represents the eminent biocompatibility and means that the system is devoid of any nonspecific toxicity in vivo. Moreover, a superior anti-tumor effect was demonstrated on a three-dimensional glioma spheroid model. Thus, this combinatorial chemo/photodynamic therapy revealed that ICG-Gen@CasNPs mediated epigenetic regulation, which is a crucial molecular mechanism of GBM suppression.