Abstract 367: Nano-immunotherapy in TNBC: Aptamer-based nanoparticles for PD-L1 siRNA delivery to cancer cells

Abstract

Abstract Triple-negative breast cancer (TNBC) is a heterogeneous and aggressive group of breast cancers. The lack of specific actionable targets makes chemotherapy the main treatment for TNBC patients. However, chemotherapy has limited success due to scarce bioavailability, severe systemic side effects and drug resistance. Polymeric nanoparticles (PNPs) may efficiently deliver in vivo therapeutics to tumors when conjugated to specific targeting agents. Potential agents for targeting tumor cells are aptamers: short, single-stranded oligonucleotides that interact at high affinity with their targets. Here, we report the characterization of new multifunctional nanovectors consisting of safe and biodegradable PNPs, highly specific TNBC aptamers as delivery agents and artificial small interfering RNA (siRNA) as drug payload, designed to suppress programmed cell death-ligand 1 (PD-L1) expression, a major feature of immune evasion in cancer cells. We efficiently entrapped siRNA-PD-L1 into PNPs. To enable active targeting, siPD-L1-PNPs were functionalized with TN145-aptamer, which we previously generated by cell-SELEX and shown to bind with nanomolar affinity to TNBC cells distinguishing them from both normal breast cells and non-TNBC breast cancer cells. TN145 aptamer actively internalizes into target cells, thus representing a good candidate to deliver a therapeutic payload. We show that the aptamer-decorated nanovectors efficiently deliver fluorescein-labeled siRNA into TNBC MDA-MB-231 and BT-549 cells, as assessed by confocal microscopy. Unconjugated nanovectors or conjugated with scrambled aptamers were used as controls. Non-TNBC BT-474 and MCF7 breast cancer cells, were used to exclude unspecific binding. Importantly, a 30-min incubation of TN145-conjugated nanovectors on target cells, at a siPD-L1 concentration of 1 nM, results in stronger PD-L1 silencing than that achieved by siPD-L1 delivered via a commercial transfection reagent. Furthermore, TN145-PNPs loaded with both siPD-L1 and cisplatin were generated and the efficacy of combined treatment was tested on tumor cells and tumor and immune cell co-cultures. Chemotherapy, including cisplatin, has been reported to induce PD-L1 enrichment in TNBC cells, hence an aptamer-targeted nanosystem enabling the synergistic effect of siRNA that directly knocks down PD-L1 expression on tumor cells with a powerful chemotherapeutic drug could be the future way to eradicate TNBC cells. Citation Format: Lisa Agnello, Simona Camorani, Silvia Tortorella, Annachiara d’Argenio, Roberto Nilo, Monica Fedele, Antonella Zannetti, Mauro Comes Franchini, Laura Cerchia. Nano-immunotherapy in TNBC: Aptamer-based nanoparticles for PD-L1 siRNA delivery to cancer cells [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 367.