Chitosan Nanoparticle Delivery of Prunus africana (Hook.f) Kalkman Attenuates TGF-β/SMAD3-Driven Epithelial–Mesenchymal Transition to Suppress Prostate Cancer Metastasis

Abstract

Background: As is well known, one of the major drivers of metastatic prostate cancer is the epithelial-mesenchymal transition (EMT), which is tightly controlled by TGF-β/SMAD3 signaling. Therefore, although Prunus africana, which contains active phytochemicals with anticancer potential, is a drug candidate with poor solubility and limited bioavailability, these limitations may hamper its efficacy in clinical use. Aim: In this study, the team assessed whether vending the extract, P. africana, with chitosan nanoparticle delivery created a hindrance to TGF-β/SMAD3-mediated EMT and metastasis in prostate cancer cells. Methods: P. africana-loaded chitosan nanoparticles were prepared by ionic gelation with sodium tripolyphosphate and were characterized for the particle size, polydispersity index, zeta potential, encapsulation efficiency, morphology, and release profile. Antimetastatic effects were analyzed using prostate cancer cells' viability, wound-healing, transwell migration/invasion, qRT-PCR, western blotting, and immunofluorescence. TGF-β-induced EMT was established at 10 ng/mL of recombinant TGF-β1. The in vivo metastasis model was used to confirm the metastatic burden and pathway modulation. Results: Average physical properties were as follows: average diameter, 168.4 ± 12.6 nm; polydispersity index, 0.23 ± 0.04; zeta potential, +31.7 ± 3.2 mV; and entrapment efficiency, 82.6 ± 4.8%. Release from the nanoparticles reached 71.3% in 72 hours. P. africana-loaded chitosan nanoparticles significantly inhibited TGF-β1-induced cell migration by 64.8% and cell invasion by 69.2% relative to the TGF-β1-treated group (p < 0.05). It also reduced the number of lung metastases by 58.7% compared with the metastatic control group (n = 6 animals per group, p < 0.05). This treatment downregulated TGF-β-induced SMAD3 phosphorylation, followed by downregulation of N-cadherin and vimentin, Snail, Slug, and Twist, and restoration of E-cadherin. In vivo studies demonstrated a significant reduction in metastatic sites and pSMAD3 expression with nanoparticles. Conclusion: Chitosan nanoparticle intervention enforced an antimetastatic effect of P. africana by dimming off TGF-β/SMAD3-mediated EMT, suggesting this as a potential nanophytotherapeutic against prostate cancer metastases.