Novel celecoxib-loaded chitosan-fucoidan nanoparticles as potential immunotherapy for oral squamous cell carcinoma: Mechanistic insights

Celecoxib (CXB), a selective COX-2 inhibitor, is a component of triple-oral-metronomic-chemotherapy. However, chronic CXB utilization in high doses could bring about major cardiovascular consequences. The CXB incorpo-ration into chitosan (CS)/fucoidan (FCD) nanoparticles (NPs) could be expected to reduce drug toxicity, improve epithelial drug permeation, and enhance drug delivery to COX-2 over-expressing sites within TME. CXB-loaded CS/FCD NPs were developed and evaluated for particle size, zeta potential, entrapment efficiency, morphology, and in vitro drug release. SCC-4 cells were used to test the cytotoxic, antiproliferative, and pro-apoptotic effects by performing MTT, Ki-67, and Annexin-V assays, respectively. The selective uptake of CS/FCD NPs by labelled tumor immune cells (TICs), tumor-endothelial-cells (TECs), and myeloid-derived-suppressor-cells (MDSCs) was determined qualitatively and quantitatively. Furthermore, signaling molecules, including Jagged-1/Notch-signaling, and biomarkers of TICs, TECs, and MDSCs; such as TGF-beta, IL-6, aldehyde dehydrogenase, and arginase-1/iNOS, were analyzed in harvested SCC-4 cells pre-treated with CXB-CS/FCD-NPs, plain FCD and CXB. The best achieved CXB-CS1FCD5 NPs were spherical in shape, and possessed an optimum size (226.4 nm), promising zeta potential (-26.30 mV), high entrapment efficiency (76.78%), and allowed sustained CXB release. They showed the utmost anti-proliferative, pro-apoptotic and cell-cycle arrest in SCC-4 cells with greater accumulation within MDSCs. Neither FCD nor CXB in their plain form could affect all of the tested TME cellular biomarkers. On contrary, CXB-CS/FCD NPs had significantly affected all of the investigated biomarkers. This study highlighted the synergistic antitumor potential of CXB-CS/FCD NPs against oral cancer, at lower CXB doses, and provided some mechanistic insights that can in part explain the observed anticancer efficacy.