Abstract
<title>Abstract</title> <p>Osteosarcoma is the most frequent bone malignancy in children and adolescents. Unfortunately, despite advances in treatment, chemoresistance and tumour recurrence remain major challenging obstacles. Increasing evidence suggests that surviving malignant cells can undergo adaptive reprogramming following chemotherapy, attaining cancer stem cell (CSC)-associated characteristics and other cellular phenotypes that aggravate the treatment outcomes. Herein, the influences of doxorubicin exposure on osteosarcoma cell responses were investigated, with particular emphasis on stemness, plasticity, and inflammatory signalling. Doxorubicin exposure promoted the acquisition of stemness and epithelial-mesenchymal transition (EMT), accompanied by enhanced migratory behaviour and reduced drug responsiveness. Prolonged activation of interleukin-1 beta (IL-1β)/cyclooxygenase-2 (COX-2) inflammatory axis was also discovered and persisted beyond the treatment period. A self-amplifying inflammatory circuit was identified, and inflammatory responses were intensified in recipient cells following treatment with conditioned medium and extracellular vesicles derived from doxorubicin-treated cells, implying the dissemination of adaptive inflammatory signals between the cell population. Additionally, migration capability was suppressed, and doxorubicin sensitivity was improved following COX-2 inhibition in chemo-resistant cells. These findings suggest that chemotherapy may inadvertently induce osteosarcoma adaptation through coordination of CSC- and EMT-associated plasticity and inflammatory responses, thereby providing insight into mechanisms underlying chemoresistance and potential opportunities for therapeutic intervention in osteosarcoma patients.</p>