Identification of a novel Microbacterium species and biosynthesis of gold nanoparticles: activation of apoptosis and dysregulation of ABCG transporters in gastric adenocarcinoma cells.

Abstract

Gastric cancer has high morbidity and mortality rates worldwide, often requiring new therapeutic approaches. Biosynthesis of gold nanoparticles (GNPs) offers a promising treatment due to their unique biological properties and biocompatibility. In this study, we synthesized gold nanoparticles using the cultural supernatant of Microbacterium sp. MAH-37 (MM37-S) and evaluated their anti-gastric cancer activity, focusing on apoptosis induction and regulation of the ABCG transporter pathway. The Microbacterium sp. strain MAH-37 was isolated from pumpkin garden soil, and its morphology was characterized by transmission electron microscopy (TEM). The successful biosynthesis of MM37-S-GNP was confirmed by UV-visible spectroscopy, SAED, DLS, FTIR, XRD, EDX, and FE-TEM analyses. Biological evaluations revealed that MM37-S-GNPs exhibited cytotoxicity of approximately 72% at 200 µg/mL against AGS cells and confirmed by colony formation and Live/Dead assay, whereas normal HFE-145 cells was non-toxic. Furthermore, Hoechst 33,258, propidium iodide, and Mito Tracker revealed nuclear condensation and fragmentation, membrane-compromised cells, and mitochondrial disruption, respectively, indicating cell death via apoptosis. H₂DCFDA staining demonstrated a significant increase intracellular reactive oxygen species (ROS) generation in AGS cells following MM37-S-GNP. Flow cytometric analysis revealed that treatment induced apoptosis in AGS cells, with 30.4% apoptotic cells observed at 200 µg/mL. Consistently, mRNA and protein expression levels confirmed apoptosis cell death, as evidenced by an increased Bax/Bcl-2 ratio and elevated levels of cleaved caspase-9. Additionally, Western blot analysis revealed that treatment with higher doses of MM37-S-GNPs significantly downregulated the expression of ABCG1 and ABCG2 transporters. MM37-S-GNPs selectivelyeliminated gastric cancer cells through ROS-mediated mitochondrial damage and apoptotic pathways, while effectively regulating ABCG transporter expression, highlighting their potential as a promising nanotherapeutic agent.