Enhancing radiosensitivity of osteosarcoma by ITGB3 knockdown: a mechanism linked to enhanced osteogenic differentiation status through JNK/c-JUN/RUNX2 pathway activation.

BACKGROUND: The prognosis of osteosarcoma has improved little over the past few decades, with radioresistance being a contributing factor. Effective radiosensitizing targets and novel mechanisms for treating osteosarcoma are urgently needed. Research on the impact of regulating differentiation levels on the radiosensitivity of malignant tumors is limited. This study aimed to explore the efficacy of ITGB3 as a novel radiosensitizing target in osteosarcoma and to explore whether the modulation of osteogenic differentiation plays a role in mediating the radiosensitizing effect. METHODS: RNA sequencing was utilized to screen for potential targets that affect the radiosensitivity of osteosarcoma. In vitro assays examining cell viability, apoptosis, proliferation, migration, and invasion were conducted to verify the radiosensitizing effect of ITGB3-knockdown (KD). Furthermore, in vivo validation was performed by constructing mouse models with subcutaneous and orthotopic tibial tumors. Rescue experiments involving siRNAs and molecular inhibitors were performed to explore and validate the mechanisms through which ITGB3-KD exerts a radiosensitizing effect in vitro and in vivo. Additionally, osteogenic differentiation cultures of osteosarcoma cells were conducted as auxiliary validation for the radiosensitizing mechanism. RESULTS: ITGB3-KD had a radiosensitizing effect on osteosarcoma in vitro by inhibiting cell viability, proliferation, migration, and invasion and promoting apoptosis. ITGB3-KD radiosensitized osteosarcoma in vivo in subcutaneous and orthotopic tibial tumor models. ITGB3-KD upregulated the JNK/c-JUN pathway, and rescue experiments with a JNK inhibitor revealed that the activation of this pathway was crucial for the upregulation of osteogenic markers such as RUNX2, OCN, and OPN, as well as for promoting apoptotic pathways. siRNA-based rescue experiments indicated that the upregulation of RUNX2 mediated the proapoptotic radiosensitizing effects of ITGB3-KD. Culture in osteogenic differentiation medium promoted osteosarcoma radiosensitization by enhancing the osteogenic differentiation status, working synergistically with ITGB3-KD. CONCLUSIONS: Our findings indicate that ITGB3-KD enhances radiosensitivity in osteosarcoma by promoting osteogenic differentiation and apoptosis through activation of the JNK/c-JUN/RUNX2 pathway, identifying ITGB3 as a candidate therapeutic target and implicating JNK/c-JUN/RUNX2 signaling as a modulatory axis for improving the response to radiation of osteosarcoma.