Abstract 301: Repurposing engineered thymoquinone nanoparticles to inhibit drug-resistant prostate cancer

Abstract Despite advanced treatment strategies and therapeutics for prostate cancer (PCa), the metastatic castration-resistant prostate cancer (mCRPC) mechanism remains obscure. Although docetaxel (DTX) and other anti-mitotic chemotherapeutic drug are considered the first line drugs for PCa patients; the resulting side effects and drug resistance increase the demand for an alternative such as natural compounds for effective treatment. However, the natural compounds that achieved remarkable height to overcome drug resistance, their bioavailability and targeted delivery during treatment has become a new challenge. As prostate-specific membrane antigen (PSMA) receptors are expressed on the surface of most PCa cells, we anticipated that these receptors may provide the potential target for effective therapy. Considering these, we employed the natural compound, thymoquinone (TQ)-encapsulated planetary ball-milled nanoparticles (PBM-NPs) formulated with starch (FDA approved, natural polysaccharides) inner core and biocompatible and biodegradable co-polymers poly (ε-caprolactone)/poly (ethylene glycol), functionalized with a PSMA aptamer (A10), which can selectively recognize and bind to PSMA membrane. The functionalities of this strategy were analyzed by targeting A10-TQ-PBM-NP in DTX-resistant cells (C4-2B-R and LNCaP-R), which overexpresses PSMA protein and multidrug resistance (MDR) gene ABCB1, and validated through flow cytometry, immunofluorescence, qRT-PCR, and western blot techniques. The results showed that the aptamer-based nano delivery of a TQ can modulate the cellular and molecular pathways responsible for DTX resistance in PCa cells through the EGFR and ZEB1 dependent mechanism. The A10-TQ-PBM-NPs counteract ATP-binding cassette (ABC)-transporter-mediated chemoresistance in PCa cells. In both cell lines, these NPs rapidly internalized and induced significant cell death at five times lower concentrations than non-conjugated PBM-TQ-NP. Further, A10-TQ-PBM-NPs have high selectivity to the PSMA receptor and downregulated the EGFR dependent pathway, Akt-1, ERK1/2, NF-kB, STAT3, and epithelial-mesenchymal transition (EMT) markers in both C4-2B-R and LNCaP-R cells, thus constraining cell survival, proliferation, and migration. The A10-TQ-PBM-NP bioconjugates also reveal remarkable efficacy and reduced toxicity as measured by body weight loss in the LNCaP-R cells xenograft mice. Altogether, our findings demonstrate that targeting PCa cells with PBM-NPs may reverse the MDR and could be used as potential therapeutic options for patients. Citation Format: Santosh Kumar Singh, Manoj Kumar Mishra, Rajesh Singh. Repurposing engineered thymoquinone nanoparticles to inhibit drug-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 301.