Abstract
Purpose: This study evaluated the efficacy of a natural polyphenol resveratrol (RES) loaded into liposomes (RES-L) which are modified with transferrin (Tf) (Tf-RES-L), to specifically direct it to glioblastoma (GBM) cells. RES is known to act on both the bulk tumor cells (BTCs) as well as the highly resistant tumor-initiating cell (TIC) population within GBMs. However, low aqueous solubility, chemical instability, poor pharmacokinetics and low bioavailability severely limit its use as a free drug. We developed RES-L with an aim to counter these drawbacks and to eradicate the BTC and TIC populations in GBMs. Since both these sub-populations also over-express Tf receptors, we exploited this feature for the target-specific delivery of Tf-RES-L in GBM. We hypothesize that Tf-RES-L will show an improved efficacy versus the free drug or non-targeted liposomes and will act as an efficacious platform for delivery of RES.
Methods: The neurosphere (NS) assay was used to develop TIC models using GBM cell lines. The NS were characterized using in vitro limiting dilution assays (LDA) and expression of the surface marker CD133. RES-Ls were prepared by thin-film rehydration method and Tf was attached to the liposomes using an in-house conjugation protocol. Liposomes were characterized for their size, charge, morphology and drug-loading efficacy. Rhodamine labeled, Tf-targeted formulations were tested for their association with and internalization into cells using flow cytometry and confocal microscopy, respectively. Cytotoxicity assays, oxidative stress measurements, apoptosis assays and cell-cycle analyses were carried out for the GBM monolayers and NS cultures. In vivo tumor-inhibition studies were carried out using a mouse model of GBM.
Results: NS cultures showed the presence of TICs as determined from LDAs and CD-133 expression. RES inhibited the anchorage-independent growth of GBM NS. All RES formulations induced a time and dose-dependent cytotoxicity in cells. At low concentrations, Tf-RES-Ls were significantly more cytotoxic compared to free RES or RES-L. RES formulations arrested GBM cells in the S-phase of the cell-cycle at low concentrations and exhibited a pro-oxidant effect at higher concentrations inducing significant oxidative stress only in GBM cells but not in primary human astrocytes. Tf-RES-L induced significantly higher levels of apoptosis accompanied by activation of caspases 3/7 in GBM cells compared to the free drug and non-targeted RES-L. The Tf- targeted formulations also associated with and internalized into GBM cells significantly better than the non-targeted counterparts.
Conclusions: RES effectively eliminates both, the BTCs and TICs in glioblastoma, and its encapsulation in Tf-modified liposomes still further improves its efficacy compared to the free drug or drug in non-targeted liposomes. Tf-RES-Ls thus seem like a very promising nanomedicine candidate for further development to treat GBM.
Citation Format: Aditi Jhaveri, Vladimir Torchilin. Evaluating the efficacy of transferrin-targeted, resveratrol-loaded liposomes in treating glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3251. doi:10.1158/1538-7445.AM2017-3251
- ©2017 American Association for Cancer Research.
Volume 77, Issue 13 Supplement
