Effect of Acridine Orange and Zoledronic Acid on Bone Metastasis in Renal Cell Carcinoma

The increasing incidence of renal cell carcinoma (RCC) and its associated bone metastasis pose challenges in surgical interventions, warranting the exploration of novel therapeutic approaches. Therefore, this study aimed to assess the impact of hematogenously administering acridine orange (AO) alone and in combination with zoledronic acid (ZA) on bone metastasis in RCC.

RENCA cells (1.0×10⁶ cells/10 μl) were directly injected into the right femur of male BALB/c mice. The mice were categorized into four groups based on the applied therapeutic intervention and were euthanized after five weeks. Micro-computed tomography was performed to quantify the extent of periosteal reaction, indicative of bone metastasis, along the entire length of the femur. Tumor weight and volume were measured at euthanization. Hematoxylin and eosin staining was used to examine the extent of tumor development in the bone. Apoptotic cell, osteoclast, and vascular endothelial growth factor (VEGF)-positive cell counts were assessed using TdT-mediated dUTP-biotin nick end labeling, tartrate-resistant acid phosphatase staining, and VEGF staining, respectively.

The periosteal reaction was significantly reduced in the intervention groups compared to the control group (p<0.05). The apoptotic cell numbers in the intervention groups surpassed that in the control group (p<0.05), whereas those of osteoclasts and VEGF-positive cells in the intervention groups were lower than those in the control group (p<0.05).

AO hinders bone metastasis progression in RCC, and combination therapy with ZA may be more effective than AO administration alone.