Osteosarcoma (OS), a malignant bone tumor with limited treatment options, exhibits low sensitivity to immune checkpoint therapy (ICT). Through genomics and transcriptomics analyses, we identify a subgroup of OS with methylthioadenosine phosphorylase (MTAP) deletion, which contributes to ICT resistance, leading to a "cold" tumor microenvironment. MTAP-deleted OS relies on methionine metabolism and is sensitive to methionine intervention, achieved through either dietary restriction or inhibition of methionine adenosyltransferase 2a (MAT2A), a key enzyme in methionine metabolism. We further demonstrate that methionine intervention triggers programmed death-ligand 1 (PD-L1) transcription factor IKAROS family zinc finger 1 (IKZF1) and enhances PD-L1 expression in MTAP-deleted OS cells. Methionine intervention also activates the immune-related signaling pathways in MTAP-deleted OS cells and attracts CD8⁺ T cells, thereby enhancing the efficacy of ICT. Combining methionine intervention with ICT provides a significant survival benefit in MTAP-deleted OS murine models, suggesting a rationale for combination regimens in OS ICT.

Targeted drug delivery using micro-nano robots (MNRs) is a rapidly advancing and promising field in biomedical research. MNRs enable precise delivery of drugs, addressing a wide range of healthcare needs. However, the application of MNRs in vivo is limited by power issues and specificity in different scenarios. Additionally, the controllability and biological safety of MNRs must be considered. To overcome these challenges, researchers have developed bio-hybrid micro-nano motors that offer improved accuracy, effectiveness, and safety for targeted therapies. These bio-hybrid micro-nano motors/robots (BMNRs) use a variety of biological carriers, blending the benefits of artificial materials with the unique features of different biological carriers to create tailored functions for specific needs. This review aims to give an overview of the current progress and application of MNRs with various biocarriers, while exploring the characteristics, advantages, and potential hurdles for future development of these bio-carrier MNRs.

Introduction: Osteosarcoma, characterized by high mortality and disability rates, poses a significant challenge due to its complex genetic background and the absence of specific membrane receptors, which hinder effective targeted therapy. Active targeting has emerged as a promising approach to address this issue.Methods: In this study, magnetically driven hydrogel robots (MMHR) were utilized to load and deliver drugs precisely to target sites. The drugs included SCR1481B16, a specific MET inhibitor proven to inhibit MET-driven tumor growth, and Anlotinib. The microrobots were designed to navigate under magnetic guidance, enhancing drug efficacy while minimizing damage to normal tissues.Results: The study explored the potential of MMHR loaded with SCR1481B16 and Anlotinib in the treatment of Anlotinib-resistant osteosarcoma. The microrobots were successfully designed and produced, demonstrating the ability to deliver drugs precisely to tumor sites. Evaluation of the microrobots showed an enhanced sensitivity of tumors to Anlotinib, providing new insights into the treatment of drug-resistant osteosarcoma.Discussion: Tumors overexpressing MET often develop resistance to VEGFR-targeted drugs. The use of SCR1481B16 as a MET inhibitor in combination with Anlotinib, delivered by magnetically driven hydrogel microrobots, offers a novel strategy to overcome this resistance. However, further in-depth research and validation are required before the clinical application of this method can be considered.Conclusion: In conclusion, magnetically driven hydrogel microrobots loaded with SCR1481B16 provide a promising new strategy for enhancing the sensitivity of Anlotinib-resistant osteosarcoma, bringing hope for future clinical applications in the treatment of this challenging disease.

Osteosarcoma is the most common primary bone tumor, with a poor prognosis owing to the lack of efficient molecular-based targeted therapies. Previous studies have suggested an association between CD151 and distinct consequences in osteosarcoma tumorigenicity. However, the potential of CD151 as a therapeutic target has not yet been sufficiently explored. Here, we performed integrated transcriptomic and metabolomic analyses of osteosarcoma and identified sphingolipid metabolism as the top CD151-regulated pathway. CD151 regulates sphingolipid metabolism primarily through SPTCL1, the first rate-limiting enzyme in sphingolipid biosynthesis. Mechanistically, depletion of CD151 enhanced c-myc polyubiquitination and subsequent degradation. c-myc is vital for the transcriptional activation of SPTLC1. Functionally, sphingolipid synthesis and the SPTLC1 inhibitor, myriocin, significantly suppressed the clonogenic growth of CD151-overexpression cells. Importantly, myriocin selectively restrained CD151-high expression tumor growth in preclinical patient-derived xenograft models. Collectively, these data establish that CD151 is a key mediator of sphingolipid metabolism and provide a new approach to developing novel CD151-based targeted therapies for osteosarcoma.

Background: Osteosarcoma patients with high propensity for metastasis and recurrence generally encounter a poor prognosis. Despite the extensive exploration of immunotherapy, particularly the anti-programmed cell death protein 1 (anti-PD-1) antibody, in clinical trials, the efficacy remains unsatisfactory. A more profound comprehension of the resistance mechanisms and the development of innovative therapeutic strategies is imperative. Methods: A screening was performed for drugs capable of upregulating major histocompatibility class I (MHC I) expression among clinically common drugs. The effects of the drug on both T cells and tumor cells, as well as its combination efficacy with anti-PD-1 antibody, were studied in vitro and in vivo osteosarcoma models. The molecular mechanisms underlying these biological processes were explored via RNA sequencing analysis. Results: Etoposide was shown to upregulate the MHC I expression in osteosarcoma cells, thereby enhancing the cytotoxicity of CD8 ⁺ T cells. Interleukin-33 (IL-33) played a dominant role in etoposide-activated anti-tumor immune response. Etoposide promoted the secretion of IL-33 and augmented the expression of IL-33 binding suppression of tumorigenicity 2 (ST2) receptor, which activated the nuclear factor kappa-B signaling pathway and resulted in MHC I upregulation. Furthermore, etoposide was demonstrated to improve the therapeutic efficacy of anti-PD-1 antibody. Conclusions: This study revealed the molecular mechanism underlying etoposide-activated CD8 ⁺ T cell anti-tumor immunity. The combination of Etoposide and anti-PD-1 antibody has the potential to benefit patients with advanced osteosarcoma.