Abstract LB297: Toll-like receptor 8 in tumor associated macrophages regulates miR-192-5p expression and drug resistance in neuroblastoma

Abstract MicroRNAs (miRs) are small non-coding RNAs (ncRNAs) with gene expression regulatory functions. MiRs are frequently dys-regulated in human cancers and orchestrate the biology of the disease, and its resistance to chemotherapy. Increasing evidence supports a role of the tumor microenvironment (TME) in promoting cancer growth and resistance to treatments. Tumor Associated Macrophages (TAMs) are a predominant cellular component of the TME of several types of cancers, including neuroblastoma (NB), the most frequent pediatric extra-cranial solid tumor. NB cells secrete miRs within small extracellular vesicles called exosomes, and these miR are shuttled to surrounding TAMs. Our lab was the first to show that cancer-derived exosomal miRs bind to Toll-like receptor 8 (TLR8) in TAMs, triggering an NF-κB-dependent production of TAM-derived miRs, that are then shuttled back to NB cells. Following up on that discovery, we identified a signature of miRs that are up/down-regulated in NB cells when co-cultured with TAMs expressing TLR8 or in which the TLR8 had been deleted with CRISPR/Cas9 engineering. We identified miR-192-5p as significantly down-regulated in NB cells when co-cultured with wild-type TAMs, however miR-192-5p expression was significantly increased in NB cells when co-cultured with TLR8-knock out TAMs, supporting a TLR8-mediated modulation of miR-192-5p in the NB TME. Additionally, we found that over-expression of miR-192-5p in NB cells increased sensitivity of NB cells to temozolomide and cisplatin, two commonly used drugs in the treatment of this malignancy. Overall, these findings support the use of TLR8 inhibitors to up-regulate miR-192-5p and increase sensitivity of NB cells to chemotherapy. Citation Format: Nicolo Toldo, Verena Martinez Rodriguez, Muller Fabbri. Toll-like receptor 8 in tumor associated macrophages regulates miR-192-5p expression and drug resistance in neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB297.