Search

Abstract Background Tumor angiogenesis, immunosuppression, and progression are all closely correlated with the tumor microenvironment (TME). Immune evasion is supported by both M2 phenotype tumor-associated macrophages (TAMs) and vascular aberrations in the TME. TME reprogramming is a promising therapeutic approach for treating tumors. Anti-angiogenesis has the power to control the polarization of macrophages, prevent progression, and increase drug penetration. Additionally, polyamine blocking therapy can increase CD8+ T cell infiltration and decrease immunosuppressive cells. These results led to developing a potential therapeutic regimen that targets TAMs and angiogenesis to reprogram the osteosarcoma TME. Results For the targeted biomimetic co-delivery of regorafenib and alpha-difluoromethylornithine via the mannose receptor, which is overexpressed in both TAMs and osteosarcoma cells, mannosylated poly(lactide-co-glycolide)-polyethylene glycol nanoparticles (Man-NPs) were synthesized. The superior physiological properties and intratumoral accumulation of the Man-NPs efficiently promoted TAMs polarization and inhibited angiogenesis. Macrophage repolarization further activated immune cells, which contributed to remodeling the TME. Conclusion Overall, these findings suggested that using Man-NPs as an immunotherapeutic approach to treat osteosarcoma may be promising. Graphical Abstract

Abstract 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.

Abstract Background Osteosarcoma (OS) is the most common primary bone cancer in adolescents and lung metastasis is the leading cause of death in patients with OS. However, the molecular mechanisms that promote OS growth and metastasis remain unknown. Methods We investigated the expression of myosin light chain kinase family members between metastasis and non-metastasis patients in the TARGET database and ensured that only myosin light chain kinase family member 4 (MYLK4) had higher expression in metastatic osteosarcoma patients. Then we confirmed the results by immunohistochemistry (IHC) and Western blotting (WB) of OS tissues. The effect of MYLK4 on the metastasis and proliferation of OS cells was investigated by wound healing, Transwell and colony-formation assays. Mass spectrum analysis was used to ensure the new binding protein of MYLK4. Tissue microarrays analysis was used to show the correlation between MYLK4 and pEGFR (Y1068). A series of in vivo experiments were conducted to reveal the mechanisms by which MYLK4 modulated the metastasis and proliferation of OS. Results Myosin Light Chain Kinase Family Member 4 (MYLK4) was significantly upregulated in metastatic human OS tissues. Growth and metastasis of OS could be accelerated by MYLK4 overexpression, whereas silencing MYLK4 expression resulted in decreased cell growth and metastasis. Mechanistically, mass spectrum analysis showed that MYLK4 interacted with the epidermal growth factor receptor (EGFR) in osteosarcoma cells and promoted growth and metastasis via the EGFR signaling pathway. Tissue microarrays analysis also showed that MYLK4 expression had a positive correlation with the expression of pEGFR (Y1068). Moreover, the EGFR inhibitor gefitinib could partially reverse the effect of cell proliferation and metastasis caused by MYLK4 overexpression. Importantly, the combination of MYLK4 and EGFR inhibitors had synergistic effects on growth and metastasis of OS in vitro and in vivo. Conclusion Our results indicate that MYLK4 promotes OS growth and metastasis by activating the EGFR signaling pathway and can be a novel therapeutic target for the treatment of OS patients.

Abstract Background Timolol Maleate is a non-selective beta-adrenergic blocker that is commonly used to treat open-angle glaucoma. Despite its topical administration, ophthalmic timolol enters systemic circulation and produces a systemic beta-adrenergic blockade. We report a case of long-term timolol use that uncovered and worsened an underlying cardiac conduction defect demonstrated as a third degree atrioventricular (AV) block. Case presentation A 62-year old male with a 13-year history of glaucoma was hospitalized due to shortness of breath, dizziness, and amaurosis. Electrocardiography indicated a heart rate (HR) of 29 bpm with complete atrioventricular (AV) block, and the HR was significantly increased with the treatment of isoprenaline. However, the patient experienced bradycardic episodes (− 20 Δbpm) immediately after self-administration of timolol eye drops. The AV block and bradycardia resolved 48-h after timolol cessation. The man was discharged 1 week later with an asymptomatic first-degree A-V block. However, he presented with a worsened A-V block at his one-year checkup. Conclusion We conclude that chronic topical timolol administration may aggravate a cardiac conduction defect leading to an AV block that is only temporarily resolved by timolol cessation. Patients taking timolol should be routinely monitored for cardiovascular aberrations and if any detected, immediately discontinue timolol therapy. Individuals experiencing timolol induced cardiovascular side effects should receive long term follow-up even if symptoms resolve, as they may be indicative of an underlying conduction defect.

Abstract Background Osteosarcoma (OS) is a common malignant cancer in children and adolescents and has a cure rate that has not improved in the last two decades. CYT997 (lexibulin) is a novel potent microtubule-targeting agent with various anticancer activities, such as proliferation inhibition, vascular disruption, and cell cycle arrest and apoptosis induction, in multiple cancers. However, the direct cytotoxic mechanisms of CYT997 have not yet been fully characterized. Methods We evaluated apoptosis and autophagy in human osteosarcomas after treatment with CYT997 and investigated the underlying mechanisms. To explore relationships, we used the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC), PERK inhibitor GSK2606414, ERO1 inhibitor EN460 and mitochondrial targeted protection peptide elamipretide. BALB/c-nu mice were inoculated with 143B tumor cells to investigate the in vivo effect of CYT997. Results We explored the efficacy and mechanism of CYT997 in osteosarcoma (OS) in vitro and in vivo and demonstrated that CYT997 potently suppresses cell viability and induces apoptosis and autophagy. CYT997 triggered production of ROS and exerted lethal effects via endoplasmic reticulum (ER) stress in OS cells. NAC attenuated these effects. The PERK inhibitor GSK2606414, which can block the ER stress pathway, reduced ROS production and enhanced cell viability. Moreover, activation of ERO1 in the ER stress pathway was responsible for inducing ROS production. ROS produced by the mitochondrial pathway also aggravate ER stress. Protection of mitochondria can reduce apoptosis and autophagy. Finally, CYT997 prominently reduced tumor growth in vivo. Conclusions This study suggests that CYT997 induces apoptosis and autophagy in OS cells by triggering mutually enhanced ER stress and ROS and may thus be a promising agent against OS.