# Inhibition of CXCR4 suppresses bone invasion in a murine model of oral squamous cell carcinoma

## TL;DR

Blocking CXCR4 reduces bone destruction in oral cancer by inhibiting osteoclasts and cancer cell invasion in mice.

## Contribution

Demonstrates that CXCR4 inhibition suppresses bone invasion through dual mechanisms in an OSCC murine model.

## Key findings

- AMD3100 treatment significantly increased BMD and BV/TV while decreasing BS/BV in bone micro-CT analysis.
- CXCR4 inhibition reduced TRAP-positive osteoclasts by 80% and downregulated MMP9, Snail, and Vimentin expression.
- Blocking CXCR4 suppressed both osteoclast activation and epithelial-mesenchymal transition in cancer cells.

## Abstract

C-X-C chemokine receptor type 4 (CXCR4) plays a significant role in the tumor microenvironment of oral squamous cell carcinoma (OSCC), but its specific function in bone invasion remains poorly understood.

Bioinformatic analysis of the GSE30784 dataset and Gene Ontology enrichment were performed. The role of CXCR4 was investigated using an in vivo model where poorly differentiated HSC-3 cells were inoculated into the heads of T cell-deficient female BALB/c nude mice (6 weeks old). Mice were treated systemically with the CXCR4 inhibitor AMD3100 (100 µl per dose, every other day for one week) or a PBS control (n = 3 per group). Bone invasion was defined as radiographically and histologically confirmed osteolysis of the bone. It was quantified by micro-computed tomography (micro-CT) analysis of parameters including Bone Mineral Density (BMD) and Bone Volume/Tissue Volume (BV/TV). Osteoclast activation and the expression of CXCR4 and epithelial-mesenchymal transition (EMT) markers were assessed by histochemical and immunohistochemical staining.

CXCR4 was upregulated in OSCC tissues and associated with biological processes critical for bone invasion, including cell motility and migration. In the murine model, AMD3100 treatment significantly suppressed mandibular bone destruction. Micro-CT analysis revealed a significant increase in BMD and BV/TV, and a decrease in Bone Surface/Bone Volume (BS/BV) in the treated group compared to controls (all p < 0.05). Histological evaluation showed that AMD3100 reduced bone resorption and decreased the number of TRAP-positive osteoclasts by approximately 80% (p < 0.01). Furthermore, immunohistochemical staining demonstrated that AMD3100 not only inhibited CXCR4 but also significantly downregulated the expression of the pro-invasive marker MMP9 and the EMT regulators Snail and Vimentin, with IHC scores reduced by 30–50% (p < 0.05).

Our findings demonstrate that inhibition of CXCR4 suppresses bone invasion by OSCC through dual mechanisms: inhibiting osteoclast activation and impairing the EMT process in cancer cells. These results suggest that targeting CXCR4 represents a promising therapeutic strategy to prevent bone destruction in patients with OSCC.