Nanoencapsulation of natural triterpenoid celastrol for prostate cancer treatment

Vanna Sanna,^1,2 Jean Christopher Chamcheu,³ Nicolino Pala,¹ Hasan Mukhtar,³ Mario Sechi,^1,2 Imtiaz Ahmad Siddiqui<sup>3

1</sup>Department of Chemistry and Pharmacy, University of Sassari, Sassari, Italy; ²Laboratory of Nanomedicine, University of Sassari, Sassari, Italy; ³Department of Dermatology, University of Wisconsin, Madison, WI, USA

Abstract: Celastrol (CL), a triterpenoid extracted from the Chinese herb Tripterygium wilfordii, has recently attracted interest for its potential antitumor effects. However, unfavorable physicochemical and pharmacokinetics properties such as low solubility, poor bioavailability, and systemic toxicity, are limiting its therapeutic application. In this context, the development of innovative nanocarriers can be useful to overcome these issues, and nanoencapsulation would represent a powerful strategy. In this study, we developed novel CL-loaded poly(ε-caprolactone) nanoparticles (NPs), and investigated their antiproliferative efficacy on prostate cancer cells. CL-NPs were prepared using a nanoprecipitation method and fully characterized by physicochemical techniques. The antiproliferative effects on LNCaP, DU-145, and PC3 cell lines of CL-NPs, compared to those of free CL at different concentrations (0.5, 1.0, and 2.0 µM), were investigated. Moreover, fluorescence microscopy was utilized to examine the cellular uptake of the nanosystems. Furthermore, to elucidate impact of nanoencapsulation on the mechanism of action, Western analyses were conducted to explore apoptosis, migration, proliferation, and angiogenesis alteration of prostate cancer cells. The results confirmed that CL-NPs inhibit proliferation dose dependently in all prostate cancer cells, with inhibitory concentration₅₀ less than 2 µM. In particular, the NPs significantly increased cytotoxicity at lower/medium dose (0.5 and 1.0 µM) on DU145 and PC3 cell lines with respect to free CL, with modulation of apoptotic and cell cycle machinery proteins. To date, this represents the first report on the development of biocompatible polymeric NPs encapsulating CL. Our findings offer new perspectives for the exploitation of developed CL-NPs as suitable prototypes for prostate cancer treatment.

Keywords: celastrol, tripterine, nanoparticles, poly(ε-caprolactone), prostate cancer