Surgical Advances in Osteosarcoma

Skin and Muscle Closure Techniques Following Large-Scale Osteosarcoma Removal: A Comparative Analysis

Osteosarcoma (OS), the most prevalent form of bone cancer, typically arises in osteoblast cells responsible for generating new bone. The bone produced by these cancer cells is weaker compared to healthy bone. OS is an aggressive bone cancer that often requires extensive resection, leaving behind substantial soft tissue defects. Successful closure after tumor excision is critical for wound healing and postoperative recovery. However, the optimal approach varies depending on factors like defect size and location. After extensive resection of OS, restoring the integrity of the affected area demands careful closure of both the skin and underlying muscle. The appropriate closure technique depends on the size and location of the soft tissue defect. The main objective of this systematic review is to evaluate and compare different surgical techniques for closing skin and muscle layers following large-scale OS removal. Through a systematic review methodology, we conducted an extensive analysis of the existing body of literature on this topic, drawing from relevant research papers published over the past two decades. This allowed us to collectively evaluate and synthesize available data on the subject. This review found that negative pressure wound therapy (NPWT) and flap reconstruction are the main surgical approaches used to close skin and muscle following extensive OS resection, which commonly results in large soft tissue defects due to the nature of tumor removal. Furthermore, NPWT was the most widely used method for closing soft tissue defects after major OS removal, while flap reconstruction was also common when NPWT was not appropriate or the defect was too large. An integrated approach combining vacuum therapy, skin stretching, and occasional flaps seeks to primarily close large defects after OS resection through optimized healing and tension reduction to achieve the best postoperative results.

Antitumoral-Embedded Biopolymeric Spheres for Implantable Devices

The bioactive surface modification of implantable devices paves the way towards the personalized healthcare practice by providing a versatile and tunable approach that increase the patient outcome, facilitate the medical procedure, and reduce the indirect or secondary effects. The purpose of our study was to assess the performance of composite coatings based on biopolymeric spheres of poly(lactide-co-glycolide) embedded with hydroxyapatite (HA) and methotrexate (MTX). Bio-simulated tests performed for up to one week evidenced the gradual release of the antitumor drug and the biomineralization potential of PLGA/HA-MTX sphere coatings. The composite materials proved superior biocompatibility and promoted enhanced cell adhesion and proliferation with respect to human preosteoblast and osteosarcoma cell lines when compared to pristine titanium.

Bifunctional mesoporous glasses for bone tissue engineering: Biological effects of doping with cerium and polyphenols in 2D and 3D in vitro models

This study evaluates the cytocompatibility of cerium-doped mesoporous bioactive glasses (Ce-MBGs) loaded with polyphenols (Ce-MBGs-Poly) for possible application in bone tissue engineering after tumour resection. We tested MBGs powders and pellets on 2D and 3D in vitro models using human bone marrow-derived mesenchymal stem cells (hMSCs), osteosarcoma cells (U2OS), and endothelial cells (EA.hy926). Promisingly, at a low concentration in culture medium, Poly-loaded MBGs powders containing 1.2 mol% of cerium inhibited U2OS metabolic activity, preserved hMSCs viability, and had no adverse effects on EA.hy926 migration. Moreover, the study discussed the possible interaction between cerium and Poly, influencing anti-cancer effects. In summary, this research provides insights into the complex interactions between Ce-MBGs, Poly, and various cell types in distinct 2D and 3D in vitro models, highlighting the potential of loaded Ce-MBGs for post-resection bone tissue engineering with a balance between pro-regenerative and anti-tumorigenic activities.

[Delayed diagnosis of osteosarcoma in adults: a prognostic factor to be considered]

INTRODUCTION

different variables have been associated with a worse prognosis of patients with osteosarcoma (OS), highlighting tumor size, location in the axial skeleton and the presence of metastases. The objective of this study is to analyze the prognostic impact of diagnostic delay in osteosarcoma in adults in the Mexican population in a center specialized in sarcomas.

MATERIAL AND METHODS

retrospective cohort study from January 1, 2005, to December 31, 2016, 96 patients over 21 years of age with a diagnosis of osteosarcoma were analyzed.

RESULTS

the median time to diagnosis from the onset of symptoms was six months (range: 2-36). This variable was dichotomized by applying the operator-dependent curve (ROC) analysis and we determined a cut-off value greater than five months, with an area under the curve (AUC) = 0.93 [95% CI 0.86-0.97], sensitivity 93.2% and specificity 94.6%.

CONCLUSION

time until diagnosis is a critical factor in the survival of adult patients with osteosarcoma, highlighting its influence on disease progression and the appearance of metastasis. The correlation between diagnostic delay and an unfavorable prognosis reinforces the need for rapid and efficient evaluation in suspected cases of osteosarcoma.

Biomechanical Aspects in Bone Tumor Engineering

In the past decades, anticancer drug development brought the field of tumor engineering to a new level by the need of robust test systems. Simulating tumor microenvironment in vitro remains a challenge, and osteosarcoma-the most common primary bone cancer-is no exception. The growing evidence points to the inevitable connection between biomechanical stimuli and tumor chemosensitivity and aggressiveness, thus making this component of the microenvironment a mandatory requirement to the developed models. In this review, we addressed the question: is the "in vivo - in vitro" gap in osteosarcoma engineering bridged from the perspective of biomechanical stimuli? The most notable biomechanical cues in the tumor cell microenvironment are observed and compared in the contexts of in vivo conditions and engineered three-dimensional in vitro models. Impact statement The importance of biomechanical stimuli in three-dimensional in vitro models for drug testing is becoming more pronounced nowadays. This review might assist in understanding the key players of the biophysical environment of primary bone cancer and the current state of bone tumor engineering from this perspective.

Exploring the molecular mechanism of linagliptin in osteosarcoma cell lines for anti-cancer activity

BACKGROUND

Finding new applications for widely used current drugs is a fast and effective technique for discovering new anticancer chemicals. Osteosarcoma (OS), the most prevalent form of bone cancer, has several side effects that significantly lower patients' quality of life. This study aims to systematically examine the anti-cancer activity of linagliptin (LG) in the osteosarcoma cell line Saos-2.

METHODS

MTT assays and flow cytometry were used to assess cell viability and apoptosis, respectively. qPCR array experiments were carried out to determine target gene expressions and explain the molecular mechanism of LG's action.

RESULTS

Linagliptin treatment significantly decreased the viability of Saos-2 cells and hFOB1.19 cells (p < 0.001). The treatment also induced increased apoptotic effects in both Saos-2 cells (p < 0.001) and hFOB1.19 cells (p < 0.05). qPCR assays were conducted to assess cancer pathway analysis after applying specific quantities of LG to Saos-2 and hFOB1.19 cells.

CONCLUSION

The findings of this study demonstrate that LG inhibits the proliferation of Saos-2 cells and induces cell death. LG supports cell death by suppressing the expression of specific genes involved in cancer pathways.

Tibial Bushing Wear at 28 Years of Follow-up After Rotating-Hinge Distal Femoral Replacement: A Case Report

CASE

A 58-year-old woman presented with swelling, stiffness, and pain of the right knee 28 years after rotating-hinge distal femoral replacement after osteosarcoma resection. She underwent revision. There was wear through the entire thickness of the polyethylene tibial sleeve bushing, and the implant was well-fixed. The knee was reassembled with new bushings, sleeves, yoke, axle, poly, and a locking pin.

CONCLUSION

This is the first described case of tibial sleeve bushing wear. It highlights the importance of early detection of potential complications and implant surveillance because it can enable surgeons to intervene with minor procedures, avoiding eventual catastrophic failure.

Chemotherapy Regimens for Non-Metastatic Conventional Appendicular Osteosarcoma: A Literature Review Based on the Outcomes

Osteosarcoma is a rare condition with a complex treatment. Most protocols include neoadjuvant chemotherapy, surgery, and consolidation chemotherapy as the standard of treatment. However, the use of neoadjuvant chemotherapy lacks scientific evidence proving superiority in opposition to the use of isolated chemotherapy in an adjuvant regimen after surgery. We conducted a review for studies published in English between 1980 and 2020, using the MEDLINE/PubMed and Scopus electronic databases, to evaluate the outcomes when using neoadjuvant chemotherapy or adjuvant chemotherapy strategies in the treatment of non-metastatic appendicular osteosarcoma, as well as the toxicity associated with different chemotherapeutic regimens. Patients were divided into a neoadjuvant chemotherapy group (NAC) and adjuvant chemotherapy group (ACT), depending on the chemotherapy regimen used in association with surgery. A total of 1254 articles in English were screened by title and abstract, and 146 were pre-selected for full reading and analysis. A total of 24 assays matching the inclusion criteria were selected: 10 prospective and 14 retrospective studies. This review points to an absence of significative differences in outcomes, namely overall survival, disease-free survival/event-free survival rates, or toxicity, regarding neoadjuvant or single adjuvant chemotherapy strategies used in the treatment of appendicular non-metastatic osteosarcomas. However, there is a significative difference in population dimensions between the NAC and the ACT groups. Additionally, clinical presentation, tumor localization, tumor volume, or histological type were not considered, with these variables presenting the potential to influence these results. Despite these limitations, our findings should allow a re-thinking of our current practice and promote new opportunities to optimize treatment, always looking towards better survival and lower complications rates.

Osteosarcoma: Current Concepts and Evolutions in Management Principles

Osteosarcoma is a rare malignancy arising from mesenchymal tissue, and represents the most common bone sarcoma. The management of osteosarcoma is challenging, and requires a multidisciplinary approach. In daily clinical practice, surgery, radiotherapy, and conventional chemotherapy constitute the therapeutic armamentarium against the disease. However, a significant number of patients with initially localized osteosarcoma will experience local or distant recurrence, and the prognosis for metastatic disease remains dismal. There is a pressing need to identify novel therapeutic strategies to better manage osteosarcoma and improve survival outcomes. In this study, we present recent advances in the therapeutic management of osteosarcoma, including surgical and medical advances. The role of immunotherapy (immune checkpoint inhibitors, adoptive cellular therapy, cancer vaccines) and other targeted therapies including tyrosine kinase inhibitors is discussed; however, additional studies are required to delineate their roles in clinical practice.

Spinal tumours: recommendations of the Polish Society of Spine Surgery, the Polish Society of Oncology, the Polish Society of Neurosurgeons, the Polish Society of Oncologic Surgery, the Polish Society of Oncologic Radiotherapy, and the Polish Society of Orthopaedics and Traumatology

PURPOSE

The purpose of these recommendations is to spread the available evidence for evaluating and managing spinal tumours among clinicians who encounter such entities.

METHODS

The recommendations were developed by members of the Development Recommendations Group representing seven stakeholder scientific societies and organizations of specialists involved in various forms of care for patients with spinal tumours in Poland. The recommendations are based on data yielded from systematic reviews of the literature identified through electronic database searches. The strength of the recommendations was graded according to the North American Spine Society's grades of recommendation for summaries or reviews of studies.

RESULTS

The recommendation group developed 89 level A-C recommendations and a supplementary list of institutions able to manage primary malignant spinal tumours, namely, spinal sarcomas, at the expert level. This list, further called an appendix, helps clinicians who encounter spinal tumours refer patients with suspected spinal sarcoma or chordoma for pathological diagnosis, surgery and radiosurgery. The list constitutes a basis of the network of expertise for the management of primary malignant spinal tumours and should be understood as a communication network of specialists involved in the care of primary spinal malignancies.

CONCLUSION

The developed recommendations together with the national network of expertise should optimize the management of patients with spinal tumours, especially rare malignancies, and optimize their referral and allocation within the Polish national health service system.

FANCD2 inhibits ferroptosis by regulating the JAK2/STAT3 pathway in osteosarcoma

BACKGROUND

This research aimed to investigate the roles of fanconi anemia complementation group D2 (FANCD2) on the regulation of ferroptosis in osteosarcoma progression.

METHODS

The function of FANCD2 on cell viability, invasion, migration, and tumor growth were explored. FANCD2 and pathway-related genes were determined by western blot. Ferroptosis-associated markers were determined, including lipid peroxidation, labile iron pool (LIP), ferrous iron (Fe²⁺), and ferroptosis-related genes.

RESULTS

FANCD2 expression was increased in osteosarcoma cells. FANCD2 knockdown reduced cell viability, invasion, and migration of osteosarcoma cells. FANCD2 knockdown regulated ferroptosis-related gene expression, and distinctly increased the levels of LIP, Fe²⁺, and lipid peroxidation, and these effects were reversed by a ferroptosis inhibitor Fer-1. In addition, JAK2 and STAT3 expression were reduced by silencing of FANCD2, and STAT3 activator (colivelin) distinctly reversed tumor suppressor effects of FANCD2 silencing on osteosarcoma development.

CONCLUSION

These findings suggested that FANCD2 silencing could suppress osteosarcoma cell viability, migration, invasion, and tumor growth, and induced ferroptosis by regulating the JAK2/STAT3 axis. These findings may provide novel therapeutic ideas for clinical treatment of osteosarcoma.

Activation of Dynamin-Related Protein 1 and Induction of Mitochondrial Apoptosis by Exosome-Rifampicin Nanoparticles Exerts Anti-Osteosarcoma Effect

PURPOSE

To investigate induction of cell death in Osteosarcoma (OS) using the anti-tuberculosis drug, rifampicin, loaded into exosomes.

PATIENTS AND METHODS

BMSC-exosomes were isolated by ultracentrifugation and loaded ultrasonically with rifampicin. Nanoparticle exosome-rifampicin (EXO-RIF) was added to the OS cell-lines, 143B and MG63, in vitro, to observe the growth inhibitory effect. In vivo experiments were conducted by injecting fluorescently labeled EXO-RIF through the tail vein of 143B cell xenograft nude mice and tracking distribution. Therapeutic and toxic side-effects were analyzed systemically.

RESULTS

Sonication resulted in encapsulation of rifampicin into exosomes. Exosome treatment accelerated the entry of rifampicin into OS cells and enhanced the actions of rifampicin in inhibiting OS proliferation, migration and invasion. Cell cycle arrest at the G2/M phase was observed. Dynamin-related protein 1 (Drp1) was activated by EXO-RIF and caused mitochondrial lysis and apoptosis. Exosome treatment targeted rifampicin to the site of OS, causing OS apoptosis and improving mouse survival in vivo.

CONCLUSION

The potent Drp1 agonist, rifampicin, induced OS apoptosis and exosome loading, improving OS targeting and mouse survival rates. EXO-RIF is a promising strategy for the treatment of diverse malignancies.

Hsa_circ_0097271 Knockdown Attenuates Osteosarcoma Progression via Regulating miR-640/MCAM Pathway

Background. The dysregulation of circular RNAs (circRNAs) participates in the malignant progression of multiple cancers, including osteosarcoma (OS). However, the role of circ_0097271 in OS development remains unclear. We thus aimed at unveiling the functional role and mechanism of circ_0097271 in OS. Methods. The expressions of circ_0097271, miR-640, and MCAM in OS were analyzed by qPCR. Cell proliferation and migration were inspected by CCK-8 assay, colony formation assay, and Transwell assay. Circ_0097271’s role in vivo was assayed by establishing animal models. The predicted binding relationship between miR-640 and circ_0097271 or MCAM was verified by dual-luciferase reporter or RIP assay. Results. Circ_0097271’s expression was enhanced in OS samples and cells. The knockdown of circ_0097271 restrained OS cell growth and migration, and its downregulation also blocked solid tumor growth in vivo. Circ_0097271 targeted miR-640 and negatively modulated miR-640 expression. MiR-640 was poorly expressed in OS, and its depletion recovered OS cell growth and migration that were repressed by circ_0097271 knockdown. MiR-640 bound to MCAM 3’UTR and thus suppressed MCAM expression. MCAM knockdown repressed OS cell growth and migration, while additional miR-640 depletion partially abolished the anticancer effects of MCAM knockdown in OS cells. Conclusion. Circ_0097271 is an oncogenic driver and contributes to OS development via targeting the miR-640/MCAM pathway, which provides a potential opinion for OS treatment.

Theaflavin-3,3 ′ -Digallate Plays a ROS-Mediated Dual Role in Ferroptosis and Apoptosis via the MAPK Pathway in Human Osteosarcoma Cell Lines and Xenografts

Globally, osteosarcoma (OS) is the most prevalent form of primary bone cancer in children and adolescents. Traditional neoadjuvant chemotherapy regimens have reached a bottleneck; thus, OS survivors have unsatisfactory outcomes. Theaflavin-3,3′-digallate (TF3) exhibits potent anticancer properties against many human cancers. Nevertheless, the biological effects and the underlying molecular mechanism of TF3 in human OS remain unclear. The objective of this study was to investigate the effects of TF3 on human OS cell lines and mouse xenograft models. The results showed that TF3 reduced cell viability, suppressed cell proliferation, and caused G0/G1 cell cycle arrest in both MG63 and HOS cell lines in a concentration-dependent manner. TF3 also altered the homeostatic mechanisms for iron storage in the examined cell lines, resulting in an excess of labile iron. Unsurprisingly, TF3 caused oxidative stress through reduced glutathione (GSH) exhaustion, reactive oxygen species (ROS) accumulation, and the Fenton reaction, which triggered ferroptosis and apoptosis in the cells. TF3 also induced MAPK signalling pathways, including the ERK, JNK, and p38 MAPK pathways. Furthermore, oxidative stress was shown to be the primary reason for TF3-induced proliferation inhibition, programmed cell death, and MAPK pathway activation in vitro. Moreover, TF3 exhibited markedly strong antitumour efficacy in vivo in mouse models. In summary, this study demonstrates that TF3 concomitantly plays dual roles in apoptotic and ferroptotic cell death by triggering the ROS and MAPK signalling pathways in both in vitro and in vivo models.

Latest Advances in the Management of Pediatric Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumor is the most common mesenchymal neoplasm of the gastrointestinal tract, usually found in elderly adults. It is infrequent among pediatric patients and usually differs biologically from adult-type diseases presenting mutations of KIT and PDGFR genes. In this population, more frequent is the wild-type GIST possessing SDH, TRK, RAS, NF1 mutations, among others. Both tumor types require individualized treatment with kinase inhibitors that are still being tested in the pediatric population due to the different neoplasm biology. We review the latest updates to the management of pediatric gastrointestinal tumors with a particular focus on the advances in molecular biology of the disease that enables the definition of possible resistance. Emerging treatment with kinase inhibitors that could serve as targeted therapy is discussed, especially with multikinase inhibitors of higher generation, the effectiveness of which has already been confirmed in the adult population.

Extracellular vesicles: A new diagnostic biomarker and targeted drug in osteosarcoma

Osteosarcoma (OS) is a primary bone cancer that is highly prevalent among adolescents and adults below the age of 20 years. The prognostic outcome of metastatic OS or relapse is extremely poor; thus, developing new diagnostic and therapeutic strategies for treating OS is necessary. Extracellular vesicles (EVs) ranging from 30–150 nm in diameter are commonly produced in different cells and are found in various types of body fluids. EVs are rich in biologically active components like proteins, lipids, and nucleic acids. They also strongly affect pathophysiological processes by modulating the intercellular signaling pathways and the exchange of biomolecules. Many studies have found that EVs influence the occurrence, development, and metastasis of osteosarcoma. The regulation of inflammatory communication pathways by EVs affects OS and other bone-related pathological conditions, such as osteoarthritis and rheumatoid arthritis. In this study, we reviewed the latest findings related to diagnosis, prognosis prediction, and the development of treatment strategies for OS from the perspective of EVs.

Risk stratification system and web-based nomogram constructed for predicting the overall survival of primary osteosarcoma patients after surgical resection

Background

Previous prediction models of osteosarcoma have not focused on survival in patients undergoing surgery, nor have they distinguished and compared prognostic differences among amputation, radical and local resection. This study aimed to establish and validate the first reliable prognostic nomogram to accurately predict overall survival (OS) after surgical resection in patients with osteosarcoma. On this basis, we constructed a risk stratification system and a web-based nomogram.

Methods

We enrolled all patients with primary osteosarcoma who underwent surgery between 2004 and 2015 in the Surveillance, Epidemiology, and End Results (SEER) database. In patients with primary osteosarcoma after surgical resection, univariate and multivariate cox proportional hazards regression analyses were utilized to identify independent prognostic factors and construct a novel nomogram for the 1-, 3-, and 5-year OS. Then the nomogram's predictive performance and clinical utility were evaluated by the concordance index (C-index), receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA).

Result

This study recruited 1,396 patients in all, with 837 serving as the training set (60%) and 559 as the validation set (40%). After COX regression analysis, we identified seven independent prognostic factors to develop the nomogram, including age, primary site, histological type, disease stage, AJCC stage, tumor size, and surgical method. The C-index indicated that this nomogram is considerably more accurate than the AJCC stage in predicting OS [Training set (HR: 0.741, 95% CI: 0.726–0.755) vs. (HR: 0.632, 95% CI: 0.619–0.645); Validation set (HR: 0.735, 95% CI: 0.718–0.753) vs. (HR: 0.635, 95% CI: 0.619–0.652)]. Moreover, the area under ROC curves, the calibration curves, and DCA demonstrated that this nomogram was significantly superior to the AJCC stage, with better predictive performance and more net clinical benefits.

Conclusion

This study highlighted that radical surgery was the first choice for patients with primary osteosarcoma since it provided the best survival prognosis. We have established and validated a novel nomogram that could objectively predict the overall survival of patients with primary osteosarcoma after surgical resection. Furthermore, a risk stratification system and a web-based nomogram could be applied in clinical practice to assist in therapeutic decision-making.

Spinal giant cell-rich osteosarcoma-diagnostic dilemma and treatment strategy: A case report

BACKGROUND

Giant cell-rich osteosarcoma (GCRO) is a rare histological variant of osteosarcoma. Spinal GCROs are extremely rare, with challenging diagnosis and management. Herein, we present a case of spinal GCRO at T2, which was not diagnosed in initial biopsy but after T2 corpectomy. We detailed the clinical course, management strategy, and outcome after a 4-year follow-up.

CASE SUMMARY

A 17-year-old female patient presented with back pain followed by ascending paresthesia. Spinal computed tomography (CT) and magnetic resonance imaging (MRI) revealed a collapsed T2 vertebra with an enhancing osteolytic mass. CT-guided biopsy showed inconclusive morphology. Pathology from T2 corpectomy revealed GCRO. The patient subsequently received neoadjuvant chemotherapy followed by salvage operation of T2 costotransversectomy with grossly-total resection adjuvant chemoradiation. Upon treatment completion, she had complete GCRO remission. The 4-year follow-up spinal MRI showed no tumor recurrence.

CONCLUSION

Spinal GCRO poses unique challenges in obtaining sufficient tissue diagnosis and complete surgical removal. However, long-term local control of spinal GCRO is possible following complete resection and adjuvant chemoradiation

Augmented Reality in Surgery: A Scoping Review

Augmented reality (AR) is an innovative system that enhances the real world by superimposing virtual objects on reality. The aim of this study was to analyze the application of AR in medicine and which of its technical solutions are the most used. We carried out a scoping review of the articles published between 2019 and February 2022. The initial search yielded a total of 2649 articles. After applying filters, removing duplicates and screening, we included 34 articles in our analysis. The analysis of the articles highlighted that AR has been traditionally and mainly used in orthopedics in addition to maxillofacial surgery and oncology. Regarding the display application in AR, the Microsoft HoloLens Optical Viewer is the most used method. Moreover, for the tracking and registration phases, the marker-based method with a rigid registration remains the most used system. Overall, the results of this study suggested that AR is an innovative technology with numerous advantages, finding applications in several new surgery domains. Considering the available data, it is not possible to clearly identify all the fields of application and the best technologies regarding AR.

YAP knockdown in combination with ferroptosis induction increases the sensitivity of HOS human osteosarcoma cells to Pyropheophorbide-α methyl ester-mediated photodynamic therapy

BACKGROUND AND AIMS

This study was designed to explore the effects of Yes-associated protein (YAP) knockdown on human osteosarcoma (HOS) cell sensitivity to Pyropheophorbide-α methyl ester-mediated photodynamic therapy (MPPa-PDT), and to assess how YAP silencing in combination with treatment with the ferroptosis inducer Erastin improves HOS cell sensitivity to MPPa-PDT in an effort to better clarify the molecular mechanisms underlying these phenotypes.

METHODS

At 12 h post-MPPa-PDT, Hoechst staining and flow cytometry were conducted to evaluate the apoptotic death of HOS cells. The expression of YAP in these cells at 12 h post-MPPa-PDT treatment was assessed via Western blotting and immunofluorescent staining. BODIPY^581/591-C11 was used to evaluate lipid peroxidation. Following shYAP lentiviral transduction, Western blotting was conducted to assess the expression of proteins associated with proliferation, apoptosis, and ferroptosis. EdU assays and clonogenic assays were performed to analyze cellular proliferation. Erastin-treated HOS cells were used to establish a ferroptosis model. Western blotting was used to measure ferroptosis-associated protein levels following shYAP and erastin treatment, while changes in proliferation and MDA levels in each group were examined using an MDA kit.

RESULTS

At 12 h post-MPPa-PDT, HOS cells exhibited apoptotic characteristics including nuclear fragmentation and pyknosis, with concomitant increases in apoptosis-associated proteins as detected via Western blotting and apoptotic induction as measured via flow cytometry. Phosphorylated YAP levels fell and non-phosphorylated YAP levels rose following such treatment. Transfection with shYAP was successful as a means of generating stable HOS cell lines, and Western blotting analyses of these cells revealed reductions in proteins associated with cellular proliferation together with the upregulation of apoptosis-related proteins.  MDA assays indicated that erastin combined with YAP knockdown enhanced the sensitivity of HOS cells to MPPa-PDT treatment.

CONCLUSIONS

These data indicate that ferroptosis and YAP knockdown can enhance osteosarcoma cell sensitivity to MPPa-PDT therapy.

Rho-GEF Trio regulates osteosarcoma progression and osteogenic differentiation through Rac1 and RhoA

Osteosarcoma (OS) is the most common primary bone tumor. Its high mortality rate and metastasis rate seriously threaten human health. Currently, the treatment has reached a plateau, hence we urgently need to explore new therapeutic directions. In this paper, we found that Trio was highly expressed in osteosarcoma than normal tissues and promoted the proliferation, migration, and invasion of osteosarcoma cells. Furthermore, Trio inhibited osteosarcoma cells' osteogenic differentiation in vitro and accelerated the growth of osteosarcoma in vivo. Given Trio contains two GEF domains, which have been reported as the regulators of RhoGTPases, we further discovered that Trio could regulate osteosarcoma progression and osteogenic differentiation through activating RhoGTPases. In summary, all our preliminary results showed that Trio could be a potential target and prognostic marker of osteosarcoma.

Bavachin Induces Ferroptosis through the STAT3/P53/SLC7A11 Axis in Osteosarcoma Cells

Ferroptosis is a new form of regulated cell death, which is mediated by intracellular iron. Although it is reported that bavachin has antitumour effects on several tumour cells and prompts the reactive oxygen species (ROS) generation, it is unclear whether ferroptosis can be induced by bavachin in osteosarcoma (OS) cells. In this study, we found that bavachin inhibits the viability of MG63 and HOS OS cell lines along with an increase in the ferrous iron level, ROS accumulation, malondialdehyde overexpression, and glutathione depletion. Moreover, iron chelators (deferoxamine), antioxidants (Vit E), and ferroptosis inhibitors (ferrostatin-1 and liproxstatin-1) reverse bavachin-induced cell death. Bavachin also altered the mitochondrial morphology of OS cells, leading to smaller mitochondria, higher density of the mitochondrial membrane, and reduced mitochondrial cristae. Further investigation showed that bavachin upregulated the expression of transferrin receptor, divalent metal transporter-1, and P53, along with downregulating the expression of ferritin light chain, ferritin heavy chain, p-STAT3 (705), SLC7A11, and glutathione peroxidase-4 in OS cells. More importantly, STAT3 overexpression, SLC7A11 overexpression, and pretreatment with pifithrin-α (P53 inhibitor) rescued OS cell ferroptosis induced by bavachin. The results show that bavachin induces ferroptosis via the STAT3/P53/SLC7A11 axis in OS cells.

RhoA enhances osteosarcoma resistance to MPPa-PDT via the Hippo/YAP signaling pathway

Background

Osteosarcoma (OS) is the most prevalent primary bone malignancy affecting adolescents, yet the emergence of chemoradiotherapeutic resistance has limited efforts to cure affected patients to date. Pyropheophorbide-α methyl ester-mediated photodynamic therapy (MPPa-PDT) is a recently developed, minimally invasive treatment for OS that is similarly constrained by such therapeutic resistance. This study sought to explore the mechanistic basis for RhoA-activated YAP1 (YAP)-mediated resistance in OS.

Methods

The relationship between YAP expression levels and patient prognosis was analyzed, and YAP levels in OS cell lines were quantified. Immunofluorescent staining was used to assess YAP nuclear translocation. OS cell lines (HOS and MG63) in which RhoA and YAP were knocked down or overexpressed were generated using lentiviral vectors. CCK-8 assays were used to examine OS cell viability, while the apoptotic death of these cells was monitored via Hoechst staining, Western blotting, and flow cytometry. Tumor-bearing nude mice were additionally used to assess the relationship between lentivirus-mediated alterations in RhoA expression and MPPa-PDT treatment outcomes. TUNEL and immunohistochemical staining approaches were leveraged to assess apoptotic cell death in tissue samples.

Results

OS patients exhibited higher levels of YAP expression, and these were correlated with a poor prognosis. MPPa-PDT induced apoptosis in OS cells, and such MPPa-PDT-induced apoptosis was enhanced following YAP knockdown whereas it was suppressed by YAP overexpression. RhoA and YAP expression levels were positively correlated in OS patients, and both active and total RhoA protein levels rose in OS cells following MPPa-PDT treatment. When RhoA was knocked down, levels of unphosphorylated YAP and downstream target genes were significantly reduced, while RhoA/ROCK2/LIMK2 pathway phosphorylation was suppressed, whereas RhoA overexpression resulted in the opposite phenotype. MPPa-PDT treatment was linked to an increase in HMGCR protein levels, and the inhibition of RhoA or HMGCR was sufficient to suppress RhoA activity and to decrease the protein levels of YAP and its downstream targets. Mevalonate administration partially reversed these reductions in the expression of YAP and YAP target genes. RhoA knockdown significantly enhanced the apoptotic death of OS cells in vitro and in vivo following MPPa-PDT treatment, whereas RhoA overexpression had the opposite effect.

Conclusions

These results suggest that the mevalonate pathway activates RhoA, which in turn activates YAP and promotes OS cell resistance to MPPa-PDT therapy. Targeting the RhoA/ROCK2/LIMK2/YAP pathway can significantly improve the efficacy of MPPa-PDT treatment for OS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00690-6.

LncRNA KASRT Serves as a Potential Treatment Target by Regulating SRSF1-Related KLF6 Alternative Splicing and the P21/CCND1 Pathway in Osteosarcoma: An In Vitro and In Vivo Study

Purpose

Long non-coding RNA KLF6 alternative splicing regulating transcript (lnc-KASRT) locates within the intronic region of SRSF1, possessing the potential to regulate KLF6 alternative splicing to promote carcinogenicity. Then, the current in vitro and in vivo study aimed to investigate the effect of lnc-KASRT on regulating tumor malignant behaviors, and the implication of its interaction with KLF6 alternative splicing in osteosarcoma.

Methods

Lnc-KASRT overexpression or knockdown plasmid was transfected into U-2OS and Saos-2 cells. Then, KLF6-SV1 knockdown plasmid with or without lnc-KASRT overexpression plasmid was transfected into these cells for compensative experiments. In vivo, lnc-KASRT overexpression or knockdown Saos-2 cells were injected in mice for tumor xenograft construction.

Results

Lnc-KASRT expression was increased in most osteosarcoma cell lines compared to control cell line. Lnc-KASRT overexpression promoted cell viability, mobility, and anti-apoptotic marker expression, while reducing apoptosis rate and pro-apoptotic marker expression; meanwhile, it regulated SRSF1, KLF6 alternative splicing (increased KLF6-splice variant 1 (KLF6-SV1), decreased KLF6-wild type (KLF6-WT)), and followed P21/CCND1 pathway in U-2OS/Saos-2 cells. The lnc-KASRT knockdown exhibited opposite trends. Subsequent compensative experiments disclosed that KLF6-SV1 knockdown attenuated most of the tumor-promoting effects of lnc-KASRT overexpression in U-2OS/Saos-2 cells. In vivo experiments further validated that lnc-KASRT enhanced tumor growth and reduced tumor apoptosis; meanwhile, it also increased tumor KLF6-SV1, MMP-1, and MMP-9 expressions but decreased tumor SRSF1 and KLF6-WT expressions in xenograft mice.

Conclusion

Lnc-KASRT serves as a potential treatment target via regulating SRSF1-related KLF6 alternative splicing and following P21/CCND1 pathway in osteosarcoma.