Hydroxyapatite Nanostructures Modulate Macrophage Polarization in Gastric Cancer Models with Associated Changes in SEMA3A and STXBP6

Abstract

Nano-hydroxyapatite (nHA) has emerged as a promising immunomodulatory nanomaterial for cancer therapy, yet how variation in its physicochemical characteristics influences antitumor efficacy and macrophage-associated responses remains incompletely understood. Here, we evaluated five nHA formulations with hydroxyapatite as the predominant crystalline phase but differing in nanostructural and interfacial physicochemical characteristics. Among these formulations, nHA-1 showed the most consistent overall antitumor activity in gastric cancer models. At the mechanistic level, nHA-1 was associated with macrophage polarization-related changes, including increased M1-associated markers and reduced M2-associated features, together with reduced PI3K/AKT-related signaling. Molecular and transcriptomic analyses revealed coordinated STXBP6 upregulation and reduced SEMA3A expression. siRNA-mediated perturbation in HGC-27 cells and THP-1-derived macrophages supported distinct contributions of SEMA3A and STXBP6 to tumor-cell transcriptional responses and macrophage polarization-associated transcriptional responses, without establishing a linear regulatory relationship between the two genes. These molecular changes were accompanied by autophagy-related transcriptional remodeling, the presence of morphologically identified foreign body giant cells (FBGCs), and increased CD11b⁺ myeloid-cell infiltration. Collectively, these findings associate nHA-1 treatment with tumor-intrinsic, macrophage-associated, and PI3K/AKT-linked responses and provide a formulation-oriented framework for further investigation of nHA-based therapeutic strategies in gastric cancer.