Harmine loaded Au@MSNs@PEG@Asp6 nano-composites for treatment of spinal metastasis from lung adenocarcinoma by targeting ANXA9 in vivo experiment

BACKGROUND: Annexin A9 (ANXA9) has been proved to be concerned with cancer development. However, to explore the clinical consequences of ANXA9 in lung adenocarcinoma (LUAD), especially its correlation to spinal metastasis (SM) has no in-depth study. The study was expected to elucidate the mechanism of ANXA9 in regulating SM of LUAD and create a productive nano-composites delivery system targeting this gene for treatment of SM. METHODS: Harmine (HM), a β-carboline extracted from the traditional Chinese herb Peganum harmala, loaded Au@MSNs@PEG@Asp6 (NPS) nano-composites were synthesized. Bioinformatics analysis and clinical specimens’ tests were used to verify the association between ANXA9 and prognosis of LUAD with SM. The immunohistochemistry (IHC) was employed to detect the expression levels of the ANXA9 protein in LUAD tissues with or without SM, and its significance in clinic was also explored. ANXA9‑siRNA was applied to investigate the molecular mechanism of ANXA9 in tumor behaviors. The HM release kinetics was detected by high performance liquid chromatography (HPLC) method. The cellular uptake efficiency of nanoparticles by A549 cells was observed by fluorescence microscope. Antitumor effects of nanoparticles were assessed in the nude mouse model of SM. RESULTS: The genomic amplification of ANXA9 was prevalent in LUAD tissues and closely associated with poor outcome and SM (P<0.01). The experimental result manifested that high expression of ANXA9 could lead to wretched prognosis and ANXA9 was an independent risk factor for survival (P<0.05). After impeding expression of ANXA9, the proliferation and metastatic ability of tumor cells obviously decreased, and expression of matrix metallopeptidase 2 (MMP-2) and matrix metallopeptidase 9 (MMP-9) were considerably downregulated, while the expression of associated oncogene pathway were downregulated (P<0.01) as well. The synthesized HM-loaded NPS nano-composites could target to cancer and response to reactive oxygen species (ROS) to release HM slowly. Notably, in comparison to free HM, the nano-composites showed excellent targeting and anti-tumor effects in the A549 cell-bearing mouse model. CONCLUSIONS: ANXA9 may serve as a novel biomarker for predicting poor prognosis in LUAD, and we provided an efficient and targeting drug delivery nano-composites system for precise treatment of SM from LUAD.