Osteosarcoma (OS) is a mesenchymal-origin tumor that constitutes the most common primary malignant bone tumor. The survival rate of the patients has significantly improved since the introduction of neoadjuvant chemotherapy and extensive resection, but it has stagnated in recent 40 years. Tyrosine kinase inhibitors (TKIs) have played a key part in the treatment of malignant tumors. In advanced OS, TKIs including anlotinib, apatinib, sorafenib, etc. have significantly improved the progression-free survival of patients, while the overall survival remains unchanged. The main reason is the rapid and inevitable progress of acquired drug resistance of OS. However, as the application of TKIs in OS and other tumors is still in the exploratory phase, its drug resistance mechanism and corresponding solutions are rarely reported. Hence, in this review, we summarize knowledge of the applications of TKIs, the mechanism of TKIs resistance, and the attempts to overcome TKIs resistance in OS, which are the three potentially novel insights of TKIs in OS. Because most evidence is derived from studies using animal and cell models, we also reviewed clinical trials and related bioinformatics data available in public databases, which partially improved our understanding of TKIs applications.

Because of the modest response rate after surgery and chemotherapy, treatment of osteosarcoma (OS) remains challenging due to tumor recurrence and metastasis. miR-135a has been reported to act as an anticarcinogenic regulator of several cancers. However, its expression and function in osteosarcoma remain largely unknown. Here, we reported that abridged miR-135a expression in OS cells and tissues, and its expression is inversely correlated with the expression of BMI1 and KLF4, which are described as oncogenes in several cancers. Ectopic expression of miR-135a inhibited cell invasion and expression of BMI1 and KLF4 in OS cells. In vivo investigation confirmed that miR-135a acts as a tumor suppressor in OS to inhibit tumor growth and lung metastasis in xenograft nude mice. BMI1 and KLF4 were revealed to be direct targets of miR-135a, and miR-135a had a similar effect as the combination of si-BMI1 and si-KLF4 on inhibiting tumor progression and the expression of BMI1 and KLF4 in vivo. Altogether, our results demonstrate that the targeting of BMI1/KLF4 with miR-135a may provide an applicable strategy for exploring novel therapeutic approaches for OS.

Despite recent developments worldwide in the therapeutic care of osteosarcoma (OS), the ongoing challenges in overcoming limitations and side effects of chemotherapy drugs warrant new strategies to improve overall patient survival. Spurred by rapid progress in biomedicine, nanobiotechnology, and materials chemistry, chemotherapeutic drug delivery in treatment of OS has become possible in recent years. Here, we review recent advances in the design of drug delivery system, especially for chemotherapeutic drugs in OS, and discuss the relative merits in trials along with future therapeutic options. These advances may pave the way for novel therapies requisite for patients with OS.

Sonodynamic therapy (SDT) is an emerging modality for cancer treatment that induces immunogenic cell death (ICD) through reactive oxygen species (ROS) generation, thereby triggering potent antitumor immunity. However, the hypoxic and glutathione (GSH)-rich tumor microenvironment restricts ROS production, while dense extracellular matrix (ECM) formed by cancer-associated fibroblasts (CAFs) further impedes immune cell infiltration. Here, we developed a hydrogel-based localized delivery platform co-encapsulating the nano-sonosensitizer PCN-224@MnO₂@HA (PMH), and SIS3, a SMAD3 inhibitor. Upon hydrogel-mediated local administration, MnO₂ catalyzes O₂ generation from endogenous hydrogen peroxide while depleting intracellular GSH, thereby amplifying ROS production during SDT. Concurrently, SIS3 reprograms CAFs by blocking TGF-β/SMAD3 signaling, reducing collagen deposition and promoting immune cell infiltration. In an osteosarcoma mouse model, the combination of PMH-mediated SDT with SIS3-induced CAF reprogramming reduced collagen deposition by approximately 50 % and triggered robust antitumor immune responses, which collectively contributed to a 76 % inhibition of tumor growth. Collectively, this study demonstrates a novel CAF-targeted SDT strategy integrating ECM remodeling, ROS enhancement, and localized delivery, offering a promising therapeutic paradigm for solid tumor treatment.