Dual targeting of folate receptor-expressing glioma tumor-associated macrophages and epithelial cells in the brain using a carbon nanosphere–cationic folate nanoconjugate

Glioblastoma multiforme (GBM), the highly invasive form of glioma exhibits highest mortality in patients of brain malignancies. Increasing glioma patients' survivability is challenging, as targeting to only tumor-associated malignant cells would not reduce the overall aggressiveness of tumor mass. This is due to inadequacy in countering pro-proliferative, invasive and metastatic factors released by tumor-mass associated macrophages (TAM). Hence, strategically, dual targeting of both tumor cells and TAM is necessary for effective glioma treatment and increased survivability. Conventional FR-targeting systems can easily target cancer cells that overtly express folate receptors (FR). However, FR is expressed only moderately in both glioma cells and in TAMs. Hence, it is more challenging to coordinate dual targeting of glioma cells and TAMs with lower levels of FR expression. A recently developed carbon nanosphere (CSP) with effective blood brain barrier (BBB) penetrability was modified with a new folic acid-cationic lipid conjugate (F8) as targeting ligand. The uniqueness of the cationic lipid-folate conjugate is that it stably associates with negatively charged CSP surface at about >22 mole % surface concentration, a concentration at least 5-fold higher than what is achieved for conventional FR-targeting delivery systems. This conferred dual uptake of CSP on TAM and tumor cells via FR. Doxorubicin-associated FR-targeted formulation (CFD), in an orthotopic glioma model and in glioma subcutaneous model, induced maximum anticancer effect with enhanced average mice survivability twice to that of untreated mice and without any systemic liver toxicity. Additionally, we observed significant decrease of TAM-released pro-aggressive factors, TGF-β, STAT3, invasion and migration related sICAM-1, and other cytokines indicating anti-TAM activity of CFD. Taken together, we principally devised, to our knowledge, the first FR-targeting nano-delivery system for targeting brain-associated TAM and tumor cells as an efficient glioma therapeutic.