Understanding micrometastatic disease and Anoikis resistance in ewing family of tumors and osteosarcoma

Osteosarcoma cells exhibit functional interactions with stromal cells, fostering a lung microenvironment conducive to the establishment of metastatic tumor cells

BACKGROUND

Osteosarcoma (OS) stands out as the most common bone tumor, with approximately 20% of the patients receiving a diagnosis of metastatic OS at their initial assessment. A significant challenge lies in the frequent existence of undetected metastases during the initial diagnosis. Mesenchymal stem cells (MSCs) possess unique abilities that facilitate tumor growth, and their interaction with OS cells is crucial for metastatic spread.

METHODS AND RESULTS

We demonstrated that, in vitro, MSCs exhibited a heightened migration response toward the secretome of non-metastatic OS cells. When challenged to a secretome derived from lungs preloaded with OS cells, MSCs exhibited greater migration toward lungs colonized with metastatic OS cells. Moreover, in vivo, MSCs displayed preferential migratory and homing behavior toward lungs colonized by metastatic OS cells. Metastatic OS cells, in turn, demonstrated an increased migratory response to the MSCs' secretome. This behavior was associated with heightened cathepsin D (CTSD) expression and the release of active metalloproteinase 2 (MMP2) by metastatic OS cells.

CONCLUSIONS

Our assessment focused on two complementary tumor capabilities crucial to metastatic spread, emphasizing the significance of inherent cell features. The findings underscore the pivotal role of signaling integration within the niche, with a complex interplay of migratory responses among established OS cells in the lungs, prometastatic OS cells in the primary tumor, and circulating MSCs. Pulmonary metastases continue to be a significant factor contributing to OS mortality. Understanding these mechanisms and identifying differentially expressed genes is essential for pinpointing markers and targets to manage metastatic spread and improve outcomes for patients with OS.

The Prognosis of Cancer Depends on the Interplay of Autophagy, Apoptosis, and Anoikis within the Tumor Microenvironment

Within the tumor microenvironment, the fight between the immune system and cancer influences tumor transformation. Metastasis formation is an important stage in the progression of cancer. This process is aided by cellular detachment and resistance to anoikis, which are achieved by altering intercellular signaling. Autophagy, specifically pro-survival autophagy, aids cancer cells in developing treatment resistance. Numerous studies have shown that autophagy promotes tumor growth and resistance to anoikis. To regulate protective autophagy, cancer-related genes phosphorylate both pro- and anti-apoptotic proteins. Apoptosis, a type of controlled cell death, eliminates damaged or unwanted cells. Anoikis is a type of programmed cell death in which cells lose contact with the extracellular matrix. The dysregulation of these cellular pathways promotes tumor growth and spread. Apoptosis, anoikis, and autophagy interact meticulously and differently depending on the cellular circumstances. For instance, autophagy can protect cancer cells from apoptosis by removing cellular components that are damaged and might otherwise trigger apoptotic pathways. Similarly, anoikis dysregulation can trigger autophagy by causing cellular harm and metabolic stress. In order to prevent or treat metastatic disease, specifically, targeting these cellular mechanisms may present a promising prospect for cancer therapy. This review discourses the state of our understanding of the molecular and cellular mechanisms underlying tumor transformation and the establishment of metastatic tumors. To enhance the prognosis for cancer, we highlight and discuss potential therapeutic approaches that target these processes and genes involved in them.

Single-cell and bulk RNA sequencing reveals Anoikis related genes to guide prognosis and immunotherapy in osteosarcoma

Anoikis resistance, a notable factor in osteosarcoma, plays a significant role in tumor invasion and metastasis. This study seeks to identify a distinct gene signature that is specifically associated with the anoikis subcluster in osteosarcoma. Clinical, single-cell, and transcriptional data from TARGET and GEO datasets were used to develop a gene signature for osteosarcoma based on the anoikis subcluster. Univariate Cox and LASSO regression analyses were employed. The signature's predictive value was evaluated using time-dependent ROC and Kaplan-Meier analyses. Functional enrichment analyses and drug sensitivity analyses were conducted. Validation of three modular genes was performed using RT-qPCR and Western blotting. Signature (ZNF583, CGNL1, CXCL13) was developed to predict overall survival in osteosarcoma patients, targeting the anoikis subcluster. The signature demonstrated good performance in external validation. Stratification based on the signature revealed significantly different prognoses. The signature was an independent prognostic factor. The low-risk group showed enhanced immune cell infiltration and improved immune function. Drug sensitivity analysis indicated efficacy of chemotherapy agents. Prognostic nomograms incorporating the signature provided greater predictive accuracy and clinical utility. Signatures related to the anoikis subcluster play a significant role in osteosarcoma progression. Incorporating these findings into clinical decision-making can improve osteosarcoma treatment and patient outcomes.

A novel stratification framework based on anoikis-related genes for predicting the prognosis in patients with osteosarcoma

Background

Anoikis resistance is a prerequisite for the successful development of osteosarcoma (OS) metastases, whether the expression of anoikis-related genes (ARGs) correlates with OS prognosis remains unclear. This study aimed to investigate the feasibility of using ARGs as prognostic tools for the risk stratification of OS.

Methods

The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases provided transcriptome information relevant to OS. The GeneCards database was used to identify ARGs. Differentially expressed ARGs (DEARGs) were identified by overlapping ARGs with common differentially expressed genes (DEGs) between OS and normal samples from the GSE16088, GSE19276, and GSE99671 datasets. Anoikis-related clusters of patients were obtained by consistent clustering, and gene set variation analysis (GSVA) of the different clusters was completed. Next, a risk model was created using Cox regression analyses. Risk scores and clinical features were assessed for independent prognostic values, and a nomogram model was constructed. Subsequently, a functional enrichment analysis of the high- and low-risk groups was performed. In addition, the immunological characteristics of OS samples were compared between the high- and low-risk groups, and their sensitivity to therapeutic agents was explored.

Results

Seven DEARGs between OS and normal samples were obtained by intersecting 501 ARGs with 68 common DEGs. BNIP3 and CXCL12 were significantly differentially expressed between both clusters (P<0.05) and were identified as prognosis-related genes. The risk model showed that the risk score and tumor metastasis were independent prognostic factors of patients with OS. A nomogram combining risk score and tumor metastasis effectively predicted the prognosis. In addition, patients in the high-risk group had low immune scores and high tumor purity. The levels of immune cell infiltration, expression of human leukocyte antigen (HLA) genes, immune response gene sets, and immune checkpoints were lower in the high-risk group than those in the low-risk group. The low-risk group was sensitive to the immune checkpoint PD-1 inhibitor, and the high-risk group exhibited lower inhibitory concentration values by 50% for 24 drugs, including AG.014699, AMG.706, and AZD6482.

Conclusion

The prognostic stratification framework of patients with OS based on ARGs, such as BNIP3 and CXCL12, may lead to more efficient clinical management.

Targeting tumor-associated MUC1 overcomes anoikis-resistance in pancreatic cancer

The third leading cause of cancer-related deaths in the United States is pancreatic cancer, more than 95% of which is pancreatic ductal adenocarcinoma (PDA). The incidence rate of PDA nearly matches its mortality rate and the best treatment till date is surgical resection for which only 25% are eligible. Tumor recurrence and metastasis are the main causes of cancer-related mortality. MUC1 is a transmembrane glycoprotein expressed on most epithelial cells. It is overexpressed and aberrantly glycosylated in cancer and is known as tumor-associated MUC1 (tMUC1). More than 80% of PDAs express tMUC1. A monoclonal antibody called TAB004 has been developed specifically against human tMUC1 extracellular domain. We report that treatment with TAB004 significantly reduced the colony forming potential of multiple PDA cell lines while sparing normal pancreatic epithelial cell line. Binding of TAB004 to tMUC1 compromised desmosomal integrity, induced ER stress and anoikis in PDA cells. The mechanisms underlying TAB004's antitumor effects were found to be reduced activation of the EGFR-PI3K signaling pathway, and degradation of tMUC1, thereby reducing expression of its transcriptional targets, c-Src and c-Myc. This reduction in oncogenic signaling triggered anoikis as indicated by reduced expression of antiapoptotic proteins, PTRH2 and BCL2. TAB004 treatment slowed the growth of PDA xenograft compared to IgG control and enhanced survival of mice when combined with 5-FU. Since TAB004 significantly reduced colony forming potential and triggered anoikis in the PDA cells, we suggest that it could be used as a potential prophylactic agent to curb tumor relapse after surgery, prevent metastasis and help increase the efficacy of chemotherapeutic agents.

Identification of an Iron Metabolism-Related lncRNA Signature for Predicting Osteosarcoma Survival and Immune Landscape

Background: Long noncoding RNAs (lncRNAs) act as epigenetic regulators in the process of ferroptosis and iron metabolism. This study aimed to identify an iron metabolism-related lncRNA signature to predict osteosarcoma (OS) survival and the immune landscape.

Methods: RNA-sequencing data and clinical information were obtained from the TARGET dataset. Univariate Cox regression and LASSO Cox analysis were used to develop an iron metabolism-related lncRNA signature. Consensus clustering analysis was applied to identify subtype-based prognosis-related lncRNAs. CIBERSORT was used to analyze the difference in immune infiltration and the immune microenvironment in the two clusters.

Results: We identified 302 iron metabolism-related lncRNAs based on 515 iron metabolism-related genes. The results of consensus clustering showed the differences in immune infiltration and the immune microenvironment in the two clusters. Through univariate Cox regression and LASSO Cox regression analysis, we constructed an iron metabolism-related lncRNA signature that included seven iron metabolism-related lncRNAs. The signature was verified to have good performance in predicting the overall survival, immune-related functions, and immunotherapy response of OS patients between the high- and low-risk groups.

Conclusion: We identified an iron metabolism-related lncRNA signature that had good performance in predicting survival outcomes and showing the immune landscape for OS patients. Furthermore, our study will provide valuable information to further develop immunotherapies of OS.

FASN Knockdown Inhibited Anoikis Resistance of Gastric Cancer Cells via P-ERK1/2/Bcl-xL Pathway

Anoikis resistance (AR) is a crucial step in tumor metastasis. The overexpression of fatty acid synthase (FASN) is not only related to the AR of osteosarcoma cells, but also evidenced on gastric cancer (GC). This study investigated the role of FASN in the AR of GC cells. Plates coated with poly-HEMA were used for the culture of cells with AR. Small interfering RNA targeting FASN (siFASN) was transfected into MNK-45 and AGS cells. The number and apoptosis of cells were assessed by a hemacytometer and Annexin-V-FITC/PI assay, respectively. Aggregated cells and colony numbers were manually counted under a microscope. The migration and invasion rates were measured via wound healing and Transwell invasion assays, respectively. The levels of FASN, phosphorylated (p)-ERK1/2, ERK1/2 and Bcl-xL were detected through western blot or quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The results showed that the cell numbers of MNK-45 and AGS were increased while that of GES-1 cell was decreased during the culture in suspension. A higher apoptosis rate and a smaller number of aggregated cells were observed in GES-1 cells in comparison with MNK-45 and AGS cells. A larger colony number, greater migration and invasion rates, and higher mRNA and protein expressions of FASN were presented in the AR group compared with the control group. Cells transfected with siFASN possessed lower migration and invasion rates, reduced expressions of FASN mRNA and protein, p-ERK1/2 and Bcl-xL, and induced a significantly declined ratio of p-ERK1/2 to ERK1/2. These findings suggest that down-regulation of FASN suppresses the AR of GC cells, which may be related to the inhibition of p-ERK1/2/Bcl-xL pathway.

Cell death as a result of calcium signaling modulation: A cancer-centric prospective

Calcium ions (Ca²⁺) and the complex regulatory system governed by Ca²⁺ signaling have been described to be of crucial importance in numerous aspects related to cell life and death decisions, especially in recent years. The growing attention given to this second messenger is justified by the pleiotropic nature of Ca²⁺-binding proteins and transporters and their consequent involvement in cell fate decisions. A growing number of works highlight that deregulation of Ca²⁺ signaling and homoeostasis is often deleterious and drives pathological conditions; in particular, a disruption of the main Ca²⁺-mediated death mechanisms may lead to uncontrolled cell growth that results in cancer. In this work, we review the latest useful evidence to better understand the complex network of pathways by which Ca²⁺ regulates cell life and death decisions.

Prognostic Signatures of Metabolic Genes and Metabolism-Related Long Non-coding RNAs Accurately Predict Overall Survival for Osteosarcoma Patients

In this study, we identified eight survival-related metabolic genes in differentially expressed metabolic genes by univariate Cox regression analysis based on the therapeutically applicable research to generate effective treatments (n = 84) data set and genotype tissue expression data set (n = 396). We also constructed a six metabolic gene signature to predict the overall survival of osteosarcoma (OS) patients using least absolute shrinkage and selection operator (Lasso) Cox regression analysis. Our results show that the six metabolic gene signature showed good performance in predicting survival of OS patients and was also an independent prognostic factor. Stratified correlation analysis showed that the metabolic gene signature accurately predicted survival outcomes in high-risk and low-risk OS patients. The six metabolic gene signature was also verified to perform well in predicting survival of OS patients in an independent cohort (GSE21257). Then, using univariate Cox regression and Lasso Cox regression analyses, we identified an eight metabolism-related long noncoding RNA (lncRNA) signature that accurately predicts overall survival of OS patients. Gene set variation analysis showed that the apical surface and bile acid metabolism, epithelial mesenchymal transition, and P53 pathway were activated in the high-risk group based on the eight metabolism-related lncRNA signature. Furthermore, we constructed a competing endogenous RNA (ceRNA) network and conducted immunization score analysis based on the eight metabolism-related lncRNA signature. These results showed that the six metabolic gene signature and eight metabolism-related lncRNA signature have good performance in predicting the survival outcomes of OS patients.

Risk Factors, Prognostic Factors, and Nomograms for Distant Metastasis in Patients With Newly Diagnosed Osteosarcoma: A Population-Based Study

BACKGROUND

Osteosarcoma is the most common bone cancer, mainly occurring in children and adolescents, among which distant metastasis (DM) still leads to a poor prognosis. Although nomogram has recently been used in tumor areas, there are no studies focused on diagnostic and prognostic evaluation of DM in primary osteosarcoma patients.

METHODS

The data of osteosarcoma patients diagnosed between 2004 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Univariate and multivariate logistic regression analyses were used to identify independent risk factors for DM in osteosarcoma patients, and univariate and multivariate Cox proportional hazards regression analyses were used to determine independent prognostic factors of osteosarcoma patients with DM. We then established two novel nomograms and the results were evaluated by receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA).

RESULT

A total of 1,657 patients with osteosarcoma were included, and 267 patients (16.11%) had DM at the time of diagnosis. The independent risk factors for DM in patients with osteosarcoma include age, grade, T stage, and N stage. The independent prognostic factors for osteosarcoma patients with DM are age, chemotherapy and surgery. The results of ROC curves, calibration, DCA, and Kaplan-Meier (K-M) survival curves in the training, validation, and expanded testing sets, confirmed that two nomograms can precisely predict occurrence and prognosis of DM in osteosarcoma patients.

CONCLUSION

Two nomograms are expected to be effective tools for predicting the risk of DM for osteosarcoma patients and personalized prognosis prediction for patients with DM, which may benefit clinical decision-making.

Retrospective Analysis of Adoptive TIL Therapy plus Anti-PD1 Therapy in Patients with Chemotherapy-Resistant Metastatic Osteosarcoma

Background

The pathological subtype of osteosarcoma is one of the most common malignant bone tumors. Notably, chemotherapy-resistant metastatic osteosarcoma has been reported to cause significant mortality and shows poor prognosis with the currently available multidisciplinary treatments. This study investigated whether combined adoptive TIL and anti-PD1 therapy improves the prognosis of patients with chemotherapy-resistant metastatic osteosarcoma.

Methods

A total of 60 patients with chemotherapy-resistant metastatic osteosarcoma between June 2016 and March 2018 were enrolled. The primary endpoint was to evaluate the safety and adverse effects (AEs) of infusions of TIL and anti-PD1 therapy in the patients. Besides, secondary endpoints included assessing the objective response rate (ORR), progression-free survival time (PFS), and overall survival time (OS).

Results

We reported that combined TIL therapy and anti-PD1 therapy is safe and all treatment-related AEs were reversible or manageable. The ORR of all the patients is 36.67%, and patients with more infusions of TIL and CD8⁺TIL, less infusions of CD8⁺PD1⁺TIL, and less infusion of CD4⁺FoxP3⁺TIL exhibited increased PFS and OS.

Conclusion

This study determined that combined TIL and anti-PD1 therapy is safe and effective in metastatic osteosarcoma patients with chemotherapy resistance.

15-hydroxy-6α,12-epoxy-7β,10αH,11βH-spiroax-4-ene-12-one exerts anti-tumor effects against osteosarcoma through apoptosis induction

Osteosarcoma is the most common type of malignant bone tumor, which has an overall survival rate of only 15-30%. The present study aimed to investigate the effects of 15-hydroxy-6α,12-epoxy-7β,10αH,11βH-spiroax-4-ene-12-one (HESEO), a compound extracted from the endophytic fungus Penicillium sp. FJ-1 isolated from Avicennia marina, on the proliferation of osteosarcoma cells and to explore its underlying mechanisms of action. Cell number was counted to measure the cell proliferation. JC-1 reagent was used to measure mitochondrial membrane potential. ELISA was used to measure the cytochrome c level and caspase activities. Apoptosis was detected by Annexin V-Propidium Iodide staining. Gene and protein expression were measured by reverse-transcription-PCR and western blot analysis, respectively. Additionally, the anti-tumor effects of HESEO were explored within a syngeneic osteosarcoma tumor model. The results suggested that HESEO significantly inhibited the proliferation of osteosarcoma cells and induced apoptosis of MG-63 cells, evidenced by their decreased mitochondrial membrane potential, and increased cytochrome c release, caspase activities and percentage of apoptotic cells. In addition, HESEO increased the expression of pro-apoptotic genes and proteins compared with control cells. The results indicated that HESEO may act through increasing p53 upregulated modulator of apoptosis expression. Furthermore, HESEO treatment significantly increased the survival time and decreased the tumor burden of osteosarcoma tumor-bearing mice compared with vehicle treatment. Furthermore, combined treatment with HESEO enhanced the effects of the chemotherapeutic agent methotrexate on a lung metastasis osteosarcoma model. These data suggested that HESEO could be developed as a potential anti-tumor agent against osteosarcoma.

(3R)-5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one inhibited osteosarcoma growth by inducing apoptosis

As one of the leading causes of cancer-associated mortalities worldwide, the overall survival rate of osteosarcoma has stably remained at 15–30% for several decades. (3R)- 5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one (TIM), isolated from the whole plant of Selaginella moellendorffii Hieron., has been reported to have pharmacological activities. In the present study, the anti-proliferative effects of TIM against osteosarcoma were evaluated, and the underlying molecular mechanisms were explored. The results demonstrated that TIM inhibited proliferation and induced apoptosis in U2OS cells. Furthermore, the expression of the pro-apoptotic protein NOXA in the intrinsic apoptosis pathway was upregulated by TIM, while the expression of myeloid cell leukemia 1, an anti-apoptotic protein, was downregulated. In addition, TIM increased the protein expression of the endoplasmic reticulum stress markers inositol-requiring enzyme 1, activating transcription factor 6 and glucose-regulated protein 78. These results suggested that TIM induced ER stress response while activating intrinsic apoptosis. Furthermore, treating osteosarcoma tumor-bearing mice with TIM significantly inhibited the tumor growth in the xenograft animal model. Overall, the study results suggested that TIM may serve as a potential antitumor agent against osteosarcoma.

Local release of gemcitabine via in situ UV-crosslinked lipid-strengthened hydrogel for inhibiting osteosarcoma

Osteosarcoma is among the most common malignant bone tumors in human skeletal system. The conventional treatment of osteosarcoma mainly consists of combining neoadjuvant chemotherapy with surgical approach. However, it is crucial to design an artificial implant that possesses excellent biomechanical properties and is capable of sustaining local release of chemotherapeutics. In this study, we envision that the highly efficient combination of gemcitabine (GEM) hydrochloride loaded liposomes with gelatin methacryloyl (GelMA) of in situ photocrosslinkable hydrogel will lead to a multifunctional implant with unique antitumor, mechanical, and biodegradable properties. A sustained controlled release was observed; more specifically, the release of GEM in vitro lasted for 4 days long. Furthermore, its capability in killing MG63 cells was further explored by using the lixivium of GEM-Lip@Gel and GEM-GelMA hydrogel in vitro (composite hydrogel by GEM loaded liposomes blending with GelMA, short for GEM-Lip@Gel), which agreed with the drug release outcome. In addition, these hydrogel showed excellent ability in inhibiting osteosarcoma in vivo by Balb/c mice bearing MG63 cells. Therefore, GEM-loaded lipo-hydrogel certainly has presented itself as a promising strategy for the development of implant in the field of osteosarcoma treatment.

High expression of ID1 facilitates metastasis in human osteosarcoma by regulating the sensitivity of anoikis via PI3K/AKT depended suppression of the intrinsic apoptotic signaling pathway

A lack of understanding of the molecular basis underlying the regulation of metastatic disease and its effective therapy are the primary causes of high mortality in osteosarcoma. Thus, new insights into metastases and novel effective targets for metastatic osteosarcoma are urgently required. Anoikis resistance is considered a hallmark of cancer cells with metastatic ability. However, the molecular mechanism of anoikis is poorly understood in osteosarcoma. We applied immunohistochemistry to investigate the correlation between inhibitor of differentiation or DNA binding 1 (ID1) and clinicopathological features, and investigated the correlation between ID1 and the metastatic behavior of osteosarcoma cells, in vitro and in vivo. The results revealed that ID1 is overexpressed in human osteosarcoma tissues, is positively associated with lung metastases, and is a potential biomarker of poor prognosis. Overexpression of ID1 could increase anoikis insensitivity of osteosarcoma cells to facilitate metastasis through the PI3K/AKT-dependent mitochondrial apoptosis pathway. Knockdown of ID1 partly reversed the high potential of metastasis in anoikis-resistant osteosarcoma cells. Our findings revealed, that ID1 is a candidate molecular target for metastatic potential osteosarcoma by highlighting the role of anoikis resistance. In addition ID1 might be a potential predictor of poor prognosis in patients with osteosarcoma.

Anoikis resistant mediated by FASN promoted growth and metastasis of osteosarcoma

The pulmonary metastasis of osteosarcoma (OS) occurs commonly, which resulted from anoikis resistant (AR) of tumor cells as reported by previous studies, but the exact roles of AR in osteosarcoma were not fully studied. Our previous investigations showed fatty acid synthase (FASN) was relating to clinical features of patients with OS. In this study, we aim to explore the functions of FASN in the AR OS cells in vitro and in vivo and study the downstream effectors of FASN. In the present study, we used our established cell model to study the AR. We revealed that AR promoted cell proliferation and migration as determined by colony formation assay and transwell assay. In addition, AR assisted tumor growth in vivo. In the AR cells, the expression of FASN was higher. Thus, we constructed lentiviruses to silence or overexpress FASN in four cell lines to study functions of FASN. Silence of FASN reduced cell colonies and migration while overexpression of FASN increased colonies and migration in suspended cells. Loss of functions of FASN induced cell apoptosis in suspended OS cells while gain of function of FASN suppressed apoptosis as determined by flow cytometry. We found the levels of p-ERK1/2 and Bcl-xL declined when FASN was silenced while they increased when FASN was overexpressed. In addition, results showed that the levels of FASN and its potential related molecules (p-ERK1/2 and Bcl-xL) increased in 143B-AR and MG-63-AR cells. In vivo study showed that inhibition of FASN decreased pulmonary metastasis of OS. In conclusion, we showed that anoikis resistant and FASN as two interactional factors facilitated the progress of osteosarcoma.

Tissue engineered models of healthy and malignant human bone marrow

Tissue engineering is becoming increasingly successful in providing in vitro models of human tissues that can be used for ex vivo recapitulation of functional tissues as well as predictive testing of drug efficacy and safety. From simple tissue models to microphysiological platforms comprising multiple tissue types connected by vascular perfusion, these "tissues on a chip" are emerging as a fast track application for tissue engineering, with great potential for modeling diseases and supporting the development of new drugs and therapeutic targets. We focus here on tissue engineering of the hematopoietic stem and progenitor cell compartment and the malignancies that can develop in the human bone marrow. Our overall goal is to demonstrate the utility and interconnectedness of improvements in bioengineering methods developed in one area of bone marrow studies for the remaining, seemingly disparate, bone marrow fields.

Effects of FHIT gene on proliferation and apoptosis of osteosarcoma cells

Regulatory effects of fragile histidine triad (FHIT) gene on proliferation and apoptosis of osteosarcoma cells were studied. The hFOB1.19 and Saos2 cells were routinely cultured, pcDNA3.1-FHIT overexpression vectors carrying FHIT gene fragments and blank pcDNA3.1 vectors were transfected into Saos2 cells, respectively, and the cells were divided into hFOB, Saos2, transfection and no-load transfection groups. After transfection for 48 h, the cells were collected and analyzed. The expression of FHIT messenger ribonucleic acid (mRNA) was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The expression of FHIT protein was detected by western blot analysis. Cell Counting Kit 8 (CCK8) was used to detect cell proliferation, and flow cytometry was used to detect apoptosis. The expression of FHIT mRNA was significantly decreased in Saos2 group compared with that in hFOB group, and the difference was statistically significant (P<0.05). The expression of FHIT mRNA was significantly increased in transfection group compared with that in Saos2 group, and the difference was statistically significant (P<0.05). The expression of FHIT protein was obviously decreased in Saos2 group compared with that in hFOB group, and there was a statistically significant difference (P<0.05). The expression of FHIT protein was obviously increased in transfection group compared with that in Saos2 group, and the difference was statistically significant (P<0.05). Compared with that in the hFOB group, the cell proliferation rate was remarkably increased in Saos2 group, while the apoptosis rate was remarkably decreased, showing statistically significant differences (P<0.05). Compared with those in Saos2 group, the cell proliferation rate was significantly decreased in transfection group, while the apoptosis rate was significantly increased, and the differences were statistically significant (P<0.05). In conclusion, FHIT gene regulates the proliferation and apoptosis of Saos2 osteosarcoma cells, inhibits the proliferation and promotes apoptosis of Saos2 osteosarcoma cells.

Anoikis‑resistant human osteosarcoma cells display significant angiogenesis by activating the Src kinase‑mediated MAPK pathway

Tumor cells must resist anoikis to metastasize. There is a key role of angiogenesis in the growth and metastasis of tumors. However, the relationship between anoikis resistance and angiogenesis has not been well explored in human osteosarcoma. In the present study, we reported the higher expression of vascular endothelial growth factor-A (VEGF-A) in osteosarcoma cells that were resistant to anoikis than in parental osteosarcoma cells, promoting the proliferation, tube formation, and migration of human umbilical vein endothelial cells (HUVECs). Src, JNK (Jun amino-terminal kinase) and ERK (extracellular signal-regulated kinase) signaling pathway phosphorylation was activated in anoikis-resistant cells; Src inhibitor reduced the expression of VEGF-A and angiogenesis and inhibited JNK and ERK pathway activity. Overexpression of phosphorylated (p)-Src and VEGF-A was positively correlated to the metastatic potential in human osteosarcoma tissues, as quantified by immunohistochemistry. In addition, p-Src expression was directly correlated with VEGF-A expression and microvessel density in vivo. Our findings revealed that anoikis resistance in osteosarcoma cells increased the expression of VEGF-A and angiogenesis through the Src/JNK/ERK signaling pathways. Thus, Src may be a potential therapeutic alternative in osteosarcoma angiogenesis and metastasis.

Age dependency of primary tumor sites and metastases in patients with Ewing sarcoma

BACKGROUND

The median age of patients with Ewing sarcoma (EwS) at diagnosis is around 14-15 years. Older age is associated with a worse outcome. The correlation of age at diagnosis on sites of disease has not been fully described.

OBJECTIVE

The goal of this study was to evaluate the differences in sites of primary tumor and metastatic tumor involvement according to age groups.

DESIGN/METHOD

EwS data from the Gesellschaft für Pädiatrische Onkologie und Hämatology (GPOH) database of the Cooperative Ewing Sarcoma Study (CESS) 81/86 and the European Intergroup Cooperative Ewing's Sarcoma Study EICESS 92 and the EUROpean Ewing tumor Working Initiative of National Groups-99-Protocol (EURO-E.W.I.N.G.-99) study were analyzed. Patient and tumor characteristics were evaluated statistically using chi square tests.

RESULTS

The study population included 2,635 patients with bone EwS. Sites of primary and metastatic tumors differed according to the age groups of young children (0-9 years), early adolescence (10-14 years), late adolescence (15-19 years), young adults (20-24 years), and adults (more than 24 years). Young children demonstrated the most striking differences in site of disease with a lower proportion of pelvic primary and axial tumors. They presented less often with metastatic disease at diagnosis.

CONCLUSIONS

Site of primary and metastatic tumor involvement in EwS differs according to patient age. The biological and developmental etiology for these differences requires further investigations.

MiR-378 promotes the cell proliferation of osteosarcoma through down-regulating the expression of Kruppel-like factor 9

MicroRNAs (miRNAs) are small non-coding RNAs that play important roles in a variety of biological processes. Dysregulation of miRNAs is tightly associated with the malignancy of cancers. Aberrant expression of miR-378 has been observed in human cancers; however, the function of miR-378 in osteosarcoma (OS) remains largely unknown. Here, we showed that miR-378 was highly expressed in human OS tissues and cell lines. Overexpression of miR-378 significantly promoted the cell proliferation of OS cells. Molecular studies identified Kruppel-like factor-9 (KLF9) as a functional downstream target of miR-378. MiR-378 directly bound to the mRNA 3'-UTR region of KLF9 and suppressed the expression of KLF9. Highly expressed KLF9 reversed the promoting effect of miR-378 on the proliferation of OS cells. The expression level of miR-378 was negatively correlated with that of KLF9 in OS tissues. Collectively, our results demonstrated the molecular interaction between miR-378 and KLF9, indicating the therapeutic potential of miR-378 for OS.

Sarcoma Spheroids and Organoids-Promising Tools in the Era of Personalized Medicine

Cancer treatment is rapidly evolving toward personalized medicine, which takes into account the individual molecular and genetic variability of tumors. Sophisticated new in vitro disease models, such as three-dimensional cell cultures, may provide a tool for genetic, epigenetic, biomedical, and pharmacological research, and help determine the most promising individual treatment. Sarcomas, malignant neoplasms originating from mesenchymal cells, may have a multitude of genomic aberrations that give rise to more than 70 different histopathological subtypes. Their low incidence and high level of histopathological heterogeneity have greatly limited progress in their treatment, and trials of clinical sarcoma are less frequent than trials of other carcinomas. The main advantage of 3D cultures from tumor cells or biopsy is that they provide patient-specific models of solid tumors, and they overcome some limitations of traditional 2D monolayer cultures by reflecting cell heterogeneity, native histologic architectures, and cell-extracellular matrix interactions. Recent advances promise that these models can help bridge the gap between preclinical and clinical research by providing a relevant in vitro model of human cancer useful for drug testing and studying metastatic and dormancy mechanisms. However, additional improvements of 3D models are expected in the future, specifically the inclusion of tumor vasculature and the immune system, to enhance their full ability to capture the biological features of native tumors in high-throughput screening. Here, we summarize recent advances and future perspectives of spheroid and organoid in vitro models of rare sarcomas that can be used to investigate individual molecular biology and predict clinical responses. We also highlight how spheroid and organoid culture models could facilitate the personalization of sarcoma treatment, provide specific clinical scenarios, and discuss the relative strengths and limitations of these models.

CD99 triggering induces methuosis of Ewing sarcoma cells through IGF-1R/RAS/Rac1 signaling

CD99 is a cell surface molecule that has emerged as a novel target for Ewing sarcoma (EWS), an aggressive pediatric bone cancer. This report provides the first evidence of methuosis in EWS, a non-apoptotic form of cell death induced by an antibody directed against the CD99 molecule. Upon mAb triggering, CD99 induces an IGF-1R/RAS/Rac1 complex, which is internalized into RAB5-positive endocytic vacuoles. This complex is then dissociated, with the IGF-1R recycling to the cell membrane while CD99 and RAS/Rac1 are sorted into immature LAMP-1-positive vacuoles, whose excessive accumulation provokes methuosis. This process, which is not detected in CD99-expressing normal mesenchymal cells, is inhibited by disruption of the IGF-1R signaling, whereas enhanced by IGF-1 stimulation. Induction of IGF-1R/RAS/Rac1 was also observed in the EWS xenografts that respond to anti-CD99 mAb, further supporting the role of the IGF/RAS/Rac1 axis in the hyperstimulation of macropinocytosis and selective death of EWS cells. Thus, we describe a vulnerability of EWS cells, including those resistant to standard chemotherapy, to a treatment with anti-CD99 mAb, which requires IGF-1R/RAS signaling but bypasses the need for their direct targeting. Overall, we propose CD99 targeting as new opportunity to treat EWS patients resistant to canonical apoptosis-inducing agents.

Inhibition of IL-18-mediated myeloid derived suppressor cell accumulation enhances anti-PD1 efficacy against osteosarcoma cancer

Myeloid derived suppressor cells (MDSC) are very important in tumor immune evasion and they dramatically increased in peripheral blood of patients with osteosarcoma cancer. The association between MDSC and various cytokines has been studied in the peripheral blood. However, little is known about the mechanism drawing MDSC into tumor parenchyma. This study was to analyze the correlation between MDSC subsets and interleukin 18 (IL-18) level in osteosarcoma tumor model and its effect on the immunotherapy. MDSC were isolated from the blood and parenchyma and analyzed in the osteosarcoma tumor model. IL-18 levels were detected by enzyme-linked immunosorbent assay (ELISA) assay, real-time PCR, western blot and flow cytometry. Moreover, combination treatment with IL-18 inhibition and anti-PD1 was conducted to assess the therapeutic effects of IL-18 blockade. Results showed MDSC levels had a positive correlation with IL-18, suggesting IL-18 may attract MDSC into the parenchyma. IL-18 gene and protein expression significantly increased in blood and tumor lysates of tumor-bearing mice. Anti-IL-18 treatment significantly decreased G-MDSC and M-MDSC in the peripheral blood and tumor. Furthermore, combination therapy decreased the tumor burden and increased CD4⁺ and CD8⁺ T cell infiltration, as well as the production of interferon gamma (IFNγ) and granzyme B. Our study revealed a possible correlation between MDSC subsets and IL-18 inducing MDSC migration into the tumor tissue, in addition to provide the potential target to enhance the efficacy of immunotherapy in patients with osteosarcoma.

MicroRNA-451 dictates the anoikis resistance of osteosarcoma by targeting Rab14

Cancer cells have developed anoikis resistance and thereby survive after detachment from their primary site and while traveling through the circulation. However, the mechanisms underlying resistance to anoikis in osteosarcoma (OS) remain largely unknown. MicroRNAs (miRNA) have been reported to contribute to malignant phenotypes of cancer cells. To investigate the roles of miRNAs in anoikis resistance of OS cells, the implications of 9 well-characterized miRNAs that dysregulated in OS on cell anoikis were screened. As a result, miR-451 was identified as a crucial factor involved in anoikis resistance and anchorage-independent growth of OS cell. MiR-451 was down-regulated in OS cells, re-expression of miR-451 significantly promoted cell anoikis of three OS cell lines and inhibition of miR-451 protected HOS cells from anoikis under anoikis condition. Subsequently, bioinformatics prediction and luciferase reporter assay indicated that Rab14 was a direct target of miR-451, and Rab14 could be down-regulated by miR-451 at both mRNA and protein levels. Genetic silencing of Rab14 recapitulated the role of miR-451 on anoikis resistance and restoration of Rab14 largely abrogated the tumor suppressor function of miR-451. Finally, overexpression of miR-451 remarkably suppressed the lung metastasis of OS cells. Collectively, our findings suggest that the miR-451/Rab14 axis might serve as a novel mechanism of resistance to anoikis in OS.

MicroRNA-30a suppresses autophagy-mediated anoikis resistance and metastasis in hepatocellular carcinoma

MiRNA-30a (miR-30a) was previously reported as one of metastatic hepatocellular carcinoma (HCC)-related microRNAs. However, the function of miR-30a on enhancing our biological understanding of HCC metastasis is not clear. This study demonstrated that miR-30a was significantly down-regulated in HCC tissues and cell lines, and was associated with vascular invasion, metastasis potential and recurrent disease in HCC. Functional studies confirmed that miR-30a could inhibit the metastasis of HCC in a well-established nude mouse model of lung metastasis. Moreover, miR-30a was proved to prevent anoikis inhibition of HCC cells in vivo and in vitro. Mechanically, autophagy related protein Beclin 1 and Atg5 were direct downstream targets of miR-30a, and mediated autophagy activity influence of miR-30a in HCC. Taken together, downregulated miR-30a in metastatic HCC mediates Beclin 1 and Atg5-dependent autophagy, which confers anoikis resistance in HCC cells. The molecular basis of autophagy action during this process partly contributes to the HCC metastasis, suggesting that targeting autophagy via miR-30a may have therapeutic implications for the prevention of HCC recurrence/metastasis.

High expression of TRIM29 (ATDC) contributes to poor prognosis and tumor metastasis by inducing epithelial‑mesenchymal transition in osteosarcoma

The association of TRIM29 overexpression with cancer progression and poor clinical prognosis has been reported in the context of several types of cancers. In the present study, we investigated the prognostic relevance of TRIM29 and its involvement in the progression of human osteosarcoma. To the best of our knowledge, this is the first study to demonstrate a major role of TRIM29 in osteosarcoma. Our results showed that the expression of TRIM29 in osteosarcoma tissues was much higher than that in normal bone tissues. Furthermore, TRIM29 expression was significantly correlated with tumor size, recurrence, metastasis and overall survival time. High expression of TRIM29 and presence of metastasis were independent predictors of poor prognosis in these patients. Both protein and mRNA expression of TRIM29 in osteosarcoma cell lines were significantly higher than those in osteoblast cell line, hFOB1.19. Moreover, the results indicated that TRIM29 promoted migration and invasive growth of osteosarcoma cells by inducing epithelial-mesenchymal transition. Therefore, ectopic expression of TRIM29 potentially contributes to metastasis and poor prognosis in patients with osteosarcoma. In summary, TRIM29 is a potential prognostic biomarker and a therapeutic target for patients with osteosarcoma.

High expression levels of Cyr61 and VEGF are associated with poor prognosis in osteosarcoma

Cysteine Rich Angiogenic Inducer 61 (Cyr61) and Vascular Endothelial Growth Factor (VEGF) are signaling proteins involved in the regulation of tumor angiogenesis and progression. The purpose of this study was to investigate the clinicopathological and prognostic significance of Cyr61 and VEGF expressions in osteosarcoma. Immunohistochemical staining was performed to evaluate the expression of both the proteins in 84 osteosarcoma samples. Correlation between Cyr61/VEGF expressions and clinicopathological parameters was determined using Rank sum test and Spearman's rank correlation coefficient. Prognostic factors were identified using univariate and multivariate Cox regression analysis. The expressions of Cyr61 and VEGF were weak in 26.2% and 17.9%, moderate in 26.2% and 23.8%, and strong in 47.6% and 58.3% of osteosarcoma samples, respectively. Cyr61 and VEGF expressions moderately correlated with each other in osteosarcoma, and exhibited significant association with Enneking stage and distant metastasis. In addition, the high expression of both proteins significantly correlated with short overall survival time in these patients. The key finding in this study was that both Cyr61 and VEGF expressions were independent prognostic indicators of overall survival. In summary, our results indicate that expression of Cyr61 and VEGF may serve as important prognostic predictors in patients with osteosarcoma.

3-bromopyruvate and buthionine sulfoximine effectively kill anoikis-resistant hepatocellular carcinoma cells

BACKGROUND & AIMS

Acquisition of anoikis resistance is a prerequisite for metastasis in hepatocellular carcinoma (HCC). However, little is known about how energy metabolism and antioxidant systems are altered in anoikis-resistant (AR) HCC cells. We evaluated anti-tumor effects of a combination treatment of 3-bromopyruvate (3-BP) and buthionine sulfoximine (BSO) in AR HCC cells.

METHODS

We compared glycolysis, reactive oxygen species (ROS) production, and chemoresistance among Huh-BAT, HepG2 HCC cells, and the corresponding AR cells. Expression of hexokinase II, gamma-glutamylcysteine synthetase (rGCS), and epithelial-mesenchymal transition (EMT) markers in AR cells was assessed. Anti-tumor effects of a combination treatment of 3-BP and BSO were evaluated in AR cells and an HCC xenograft mouse model.

RESULTS

AR HCC cells showed significantly higher chemoresistance, glycolysis and lower ROS production than attached cells. Expression of hexokinase II, rGCS, and EMT markers was higher in AR HCC cells than attached cells. A combination treatment of 3-BP/BSO effectively suppressed proliferation of AR HCC cells through apoptosis by blocking glycolysis and enhancing ROS levels. In xenograft mouse models, tumor growth derived from AR HCC cells was significantly suppressed in the group treated with 3-BP/BSO compared to the group treated with 3-BP or sorafenib.

CONCLUSIONS

These results demonstrated that a combination treatment of 3-BP/BSO had a synergistic anti-tumor effect in an AR HCC model. This strategy may be an effective adjuvant therapy for patients with sorafenib-resistant HCC.

Interference with Tim-3 protein expression attenuates the invasion of clear cell renal cell carcinoma and aggravates anoikis

Tumor cells resistant to anoikis are considered to be candidates for metastasis. In the present study, the role of Tim-3 in anoikis and its influence on the invasion of clear cell renal cell carcinoma (ccRCC) was investigated. Here, polyhydroxylethylmethacrylate (poly-HEMA) was applied to two ccRCC cell lines, 786-O and Caki-2, to induce detachment from the extracellular matrix (ECM). Tim-3 mRNA and protein expression levels were assayed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot, respectively. Anoikis was measured by Ho33342/PI double staining, acridine orange staining, and further determined using the CytoSelect™ 24-well Anoikis Assay kit. Apoptosis was measured using flow cytometry, E-cadherin and N-cadherin protein expression were determined using western blotting and a Chemicon cell invasion assay kit was used to quantify the invasive capacity of 786-O and Caki-2 cells. It was demonstrated that detachment from the ECM decreases transcription and the protein expression level of Tim-3 in 786-O and Caki-2 cells compared with control cells. Interference with Tim-3 expression using small interfering RNA exacerbated anoikis in 786-O and Caki-2 cells induced by poly-HEMA treatment. E-cadherin upregulation, N-cadherin downregulation, and ECM detachment-induced reduction in invasion ability were all exacerbated by knockdown of Tim-3. In conclusion, interference with Tim-3 expression may attenuate the invasion of renal cell carcinoma by aggravating anoikis, indicating Tim-3 as a potential therapeutic target for treating ccRCC.

RanBP9/TSSC3 complex cooperates to suppress anoikis resistance and metastasis via inhibiting Src-mediated Akt signaling in osteosarcoma

Suppression of anoikis is a prerequisite for tumor cell metastasis, which is correlated with chemoresistance and poor prognosis. We characterized a novel interaction between RanBP9 SPRY domain and TSSC3 PH domain by which RanBP9/TSSC3 complex exerts transcription and post-translation regulation in osteosarcoma. RanBP9/TSSC3 complex was inversely correlated with a highly anoikis-resistant phenotype in osteosarcoma cells and metastasis in human osteosarcoma. RanBP9 cooperated with TSSC3 to inhibit anchorage-independent growth and to promote anoikis in vitro and suppress lung metastasis in vivo. Moreover, RanBP9 SPRY domain was required for RanBP9/TSSC3 complex-mediated anoikis resistance. Mechanistically, RanBP9 formed a ternary complex with TSSC3 and Src to scaffold this interaction, which suppressed both Src and Src-dependent Akt pathway activations and facilitated mitochondrial-associated anoikis. Collectively, the newly identified RanBP9/TSSC3 complex cooperatively suppress metastasis via downregulation of Src-dependent Akt pathway to expedite mitochondrial-associated anoikis. This study provides a biological basis for exploring the therapeutic significance of dual targeting of RanBP9 and TSSC3 in osteosarcoma.

Overexpression of pyruvate kinase M2 predicts a poor prognosis for patients with osteosarcoma

It is stated that high expression of pyruvate kinase (PKM2) emerges as a significant player in the metabolism and progression of various human malignancies. However, the expression of PKM2 and its association with the prognosis of osteosarcoma had not yet been studied. In the present study, the expression and biological significance of PKM2 in osteosarcoma were investigated. We found that PKM2 expression was elevated in the cancerous tissues and it was more abundant than the adjacent normal tissues (60.2 vs 26.1 %, p < 0.001). Moreover, we showed that high PKM2 expression was positively correlated with Enneking stage (p = 0.006) and distant metastasis (p = 0.007) but not with the age, gender, tumor site, tumor size, histologic grade, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and local pain of the patients. Furthermore, Kaplan-Meier analysis revealed that the overall survival (OS) for patients with high PKM2 expression was significantly lower than those with low PKM2 expression (p < 0.001). Finally, multivariate analysis revealed that high PKM2 expression was an independent prognostic factor for osteosarcoma patients (p = 0.004). Collectively, these data indicated that elevated PKM2 might serve as a novel target for the treatment of osteosarcoma.

Expression of Leptin and Sirtuin-1 is associated with poor prognosis in patients with osteosarcoma

Sirtuin-1 (SIRT1) is a downstream target of Leptin, and its inhibition promotes p53-mediated apoptosis. This study aimed to evaluate the expression and prognostic significance of Leptin and SIRT1 in osteosarcoma. Leptin and SIRT1 levels in osteosarcoma samples from 89 patients were evaluated by immunohistochemical staining. The correlations between Leptin and SIRT1 expression with clinical parameters were analyzed by Spearman's test and Pearson's chi-squared test. Prognostic factors were identified by Univariate and multivariate Cox regression analysis. We found that Leptin and SIRT1 expression was low in 23.6% and 20.2%; moderate in 25.8% and 24.7%; and high in 50.5% and 55.1% of patients with osteosarcoma, respectively. Both Leptin and SIRT1 expression were significantly associated with the Enneking stage, distant metastasis and neo-adjuvant chemotherapy. Leptin expression and SIRT1 expression were significantly correlated and they were significantly associated with shorter overall survival. Among osteosarcoma patients who received neo-adjuvant chemotherapy, both Leptin and SIRT1 expression were significantly associated with overall survival of osteosarcoma patients in univariate analysis, but only SIRT1 expression was significantly associated with overall survival of osteosarcoma patients in multivariate analysis. In conclusion, Leptin and SIRT1 expressions are significantly associated with shorter overall survival of osteosarcoma patients, and SIRT1 expression is a significant independent prognostic indicator in patients with osteosarcoma.

Enhanced T-cell immunity to osteosarcoma through antibody blockade of PD-1/PD-L1 interactions

Osteosarcoma is the most common bone cancer in children and adolescents. Although 70% of patients with localized disease are cured with chemotherapy and surgical resection, patients with metastatic osteosarcoma are typically refractory to treatment. Numerous lines of evidence suggest that cytotoxic T lymphocytes (CTLs) limit the development of metastatic osteosarcoma. We have investigated the role of PD-1, an inhibitory TNFR family protein expressed on CTLs, in limiting the efficacy of immune-mediated control of metastatic osteosarcoma. We show that human metastatic, but not primary, osteosarcoma tumors express a ligand for PD-1 (PD-L1) and that tumor-infiltrating CTLs express PD-1, suggesting this pathway may limit CTLs control of metastatic osteosarcoma in patients. PD-L1 is also expressed on the K7M2 osteosarcoma tumor cell line that establishes metastases in mice, and PD-1 is expressed on tumor-infiltrating CTLs during disease progression. Blockade of PD-1/PD-L1 interactions dramatically improves the function of osteosarcoma-reactive CTLs in vitro and in vivo, and results in decreased tumor burden and increased survival in the K7M2 mouse model of metastatic osteosarcoma. Our results suggest that blockade of PD-1/PD-L1 interactions in patients with metastatic osteosarcoma should be pursued as a therapeutic strategy.

Combination immunotherapy with α-CTLA-4 and α-PD-L1 antibody blockade prevents immune escape and leads to complete control of metastatic osteosarcoma

BACKGROUND

Osteosarcoma is one of the most common bone cancers in children. Most patients with metastatic osteosarcoma die of pulmonary disease and limited curative therapeutic options exist for such patients. We have previously shown that PD-1 limits the efficacy of CTL to mediate immune control of metastatic osteosarcoma in the K7M2 mouse model of pulmonary metastatic disease and that blockade of PD-1/PD-L1 interactions can partially improve survival outcomes by enhancing the function of osteosarcoma-specific CTL. However, PD-1/PD-L1 blockade-treated mice eventually succumb to disease due to selection of PD-L1 mAb-resistant tumor cells. We investigated the mechanism of tumor cell resistance after blockade, and additional combinational therapies to combat resistance.

METHODS

We used an implantable model of metastatic osteosarcoma, and evaluated survival using a Log-rank test. Cellular analysis of the tumor was done post-mortem with flow cytometry staining, and evaluated using a T-test to compare treatment groups.

RESULTS

We show here that T cells infiltrating PD-L1 antibody-resistant tumors upregulate additional inhibitory receptors, notably CTLA-4, which impair their ability to mediate tumor rejection. Based on these results we have tested combination immunotherapy with α-CTLA-4 and α-PD-L1 antibody blockade in the K7M2 mouse model of metastatic osteosarcoma and show that this results in complete control of tumors in a majority of mice as well as immunity to further tumor inoculation.

CONCLUSIONS

Thus, combinational immunotherapy approaches to block additional inhibitory pathways in patients with metastatic osteosarcoma may provide new strategies to enhance tumor clearance and resistance to disease.

3D tissue-engineered model of Ewing's sarcoma

Despite longstanding reliance upon monolayer culture for studying cancer cells, and numerous advantages from both a practical and experimental standpoint, a growing body of evidence suggests that more complex three-dimensional (3D) models are necessary to properly mimic many of the critical hallmarks associated with the oncogenesis, maintenance and spread of Ewing's sarcoma (ES), the second most common pediatric bone tumor. And as clinicians increasingly turn to biologically-targeted therapies that exert their effects not only on the tumor cells themselves, but also on the surrounding extracellular matrix, it is especially important that preclinical models evolve in parallel to reliably measure antineoplastic effects and possible mechanisms of de novo and acquired drug resistance. Herein, we highlight a number of innovative methods used to fabricate biomimetic ES tumors, encompassing both the surrounding cellular milieu and the extracellular matrix (ECM), and suggest potential applications to advance our understanding of ES biology, preclinical drug testing, and personalized medicine.

Significance of MTA1 in the molecular characterization of osteosarcoma

Osteosarcoma is the most common malignant bone tumor in children and characterized by aggressive biologic behavior of metastatic propensity to the lung. Change of treatment paradigm brings survival benefit; however, 5-year survival rate is still low in patients having metastastatic foci at diagnosis for a few decades. Metastasis-associated protein (MTA) family is a group of ubiquitously expressed coregulators, which influences on tumor invasiveness or metastasis. MTA1 has been investigated in various cancers including osteosarcoma, and its overexpression is associated with high-risk features of cancers. In this review, we described various molecular studies of osteosarcoma, especially associated with MTA1.

Correlation between E-cadherin-regulated cell adhesion and human osteosarcoma MG-63 cell anoikis

PURPOSE

The aim of this study was to investigate the relationship between cell adhesion and anoikis evasion among human osteosarcoma cells (MG-63), and to further study the molecular mechanisms.

MATERIALS AND METHODS

Human osteosarcoma cells (MG-63) were assessed for apoptosis, and caspase-3, E-cadherin and β-catenin expression in EDTA and control non-EDTA groups.

RESULTS

MG-63 cells were predominantly aggregated when in suspension, and the suspended cells were more dispersed in the EDTA group. Following culture in suspension for 24 h, 48 h, or 72 h, the rates of apoptosis were 34.88%±3.64%, 59.3%±7.22% and 78.5%±5.21% in the experimental group and 7.34%±2.13%, 14.7%±3.69%, and 21.4%±3.60% in the control group, respectively. Caspase-3 expression progressively increased and E-cadherin and β-catenin were decreased in the experimental group, whereas there was no change in the control group.

CONCLUSIONS

MG-63 cells could avoid anoikis through cell adhesion, and E-cadherin might play a role in this process.

Zoledronic acid inhibits pulmonary metastasis dissemination in a preclinical model of Ewing's sarcoma via inhibition of cell migration

Background

Ewing’s sarcoma (ES) is the second most frequent primitive malignant bone tumor in adolescents with a very poor prognosis for high risk patients, mainly when lung metastases are detected (overall survival <15% at 5 years). Zoledronic acid (ZA) is a potent inhibitor of bone resorption which induces osteoclast apoptosis. Our previous studies showed a strong therapeutic potential of ZA as it inhibits ES cell growth in vitro and ES primary tumor growth in vivo in a mouse model developed in bone site. However, no data are available on lung metastasis. Therefore, the aim of this study was to determine the effect of ZA on ES cell invasion and metastatic properties.

Methods

Invasion assays were performed in vitro in Boyden’s chambers covered with Matrigel. Matrix Metalloproteinase (MMP) activity was analyzed by zymography in ES cell culture supernatant. In vivo, a relevant model of spontaneous lung metastases which disseminate from primary ES tumor was induced by the orthotopic injection of 10⁶ human ES cells in the tibia medullar cavity of nude mice. The effect of ZA (50 μg/kg, 3x/week) was studied over a 4-week period. Lung metastases were observed macroscopically at autopsy and analysed by histology.

Results

ZA induced a strong inhibition of ES cell invasion, probably due to down regulation of MMP-2 and −9 activities as analyzed by zymography. In vivo, ZA inhibits the dissemination of spontaneous lung metastases from a primary ES tumor but had no effect on the growth of established lung metastases.

Conclusion

These results suggest that ZA could be used early in the treatment of ES to inhibit bone tumor growth but also to prevent the early metastatic events to the lungs.

Safety considerations for transplanting cryopreserved ovarian tissue to restore fertility in female patients who have recovered from Ewing’s sarcoma

ABSTRACT Ewing’s sarcoma (EWS) is a highly malignant cancer in children, adolescents and young adults. The chemotherapy required to treat female EWS patients may cause primary ovarian insufficiency and infertility as a side effect. Cryopreservation of ovarian tissue before the start of chemotherapy can potentially preserve fertility. When the patient has been cured and primary ovarian insufficiency has developed, transplantation of frozen/thawed ovarian tissue can restore ovarian function. The tissue is usually collected before chemotherapy is initiated, and malignant cells may contaminate the stored ovarian tissue, potentially causing recrudescence of the original cancer after transplantation. The risk of EWS metastasizing to the ovary is probably low but has not been studied in great detail. This review describes the available evidence on the risk of malignant cell contamination in the ovaries of EWS patients and presents a new case of malignant cells in an ovarian biopsy from a girl with EWS.

The histone deacetylase inhibitor, MS-275 (entinostat), downregulates c-FLIP, sensitizes osteosarcoma cells to FasL, and induces the regression of osteosarcoma lung metastases

The purpose of this study was to determine the effects of the histone deacetylase inhibitor, MS-275, on the Fas signaling pathway and susceptibility of osteosarcoma (OS) to Fas ligand (FasL)-induced cell death. OS metastasizes almost exclusively to the lungs. We have shown that Fas expression in OS cells is inversely correlated with their metastatic potential. Fas(+) cells are rapidly eliminated when they enter the lungs via interaction with FasL, which is constitutively expressed in the lungs. Fas(-) OS cells escape this FasL-induced apoptosis and survive in the lung microenvironment. Moreover, upregulation of Fas in established OS lung metastases results in tumor regression. Therefore, agents that upregulate Fas expression or activate the Fas signaling pathway may have therapeutic potential. Treatment of Fas(-) metastatic OS cell lines with 2 µM MS-275 sensitized cells to FasL-induced cell death in vitro. We found that MS-275 did not alter the expression of Fas on the cell surface; rather it resulted in the downregulation of the anti-apoptotic protein, c-FLIP (cellular FLICE-inhibitory protein), by inhibiting c-FLIP mRNA. Downregulation of c- FLIP correlated with caspase activation and apoptosis induction. Treatment of nu/nu-mice with established OS lung metastases with oral MS-275 resulted in tumor regression, increased apoptosis and a significant inhibition of c-FLIP expression in tumors. Histopathological examination of mice showed no evidence of significant toxicity. Overall, these results suggest that the mechanism by which MS-275 sensitizes OS cells and lung metastases to FasL-induced cell death may be by a direct reduction in the expression of c-FLIP.

B7-H3 is overexpressed in patients suffering osteosarcoma and associated with tumor aggressiveness and metastasis

B7-H3 is a member of the B7-family of co-stimulatory molecules, which has been shown to be broadly expressed in various tumor tissues, and which plays an important role in adaptive immune responses. The role of B7-H3 in osteosarcoma, however, remains unknown. In this study we used immunohistochemistry to analyze B7-H3 expression in 61 primary osteosarcoma tissues with case-matched adjacent normal tissues, and 37 osteochondroma and 20 bone fibrous dysplasia tissues. B7-H3 expression was expressed in 91.8% (56/61) of the osteosarcoma lesions, and the intensity of B7-H3 expression in osteosarcoma was significantly increased compared with adjacent normal tissues, osteochondroma and bone fibrous dysplasia tissues (p<0.001). Patients with high tumor B7-H3 levels had a significantly shorter survival time and recurrence time than patients with low tumor B7-H3 levels (p<0.001). Moreover, tumor B7-H3 expression inversely correlated with the number of tumor-infiltrating CD8⁺ T cells (p<0.05). In vitro, increasing expression of B7-H3 promotes osteosarcoma cell invasion, at least in part by upregulating matrix metalloproteinase-2 (MMP-2). In conclusion, our study provides the first evidence of B7-H3 expression in osteosarcoma cells as a potential mechanism controlling tumor immunity and invasive malignancy, and which is correlated with patients’ survival and metastasis.

Statins, autophagy and cancer metastasis

Statins inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. They are traditionally considered to be cholesterol-lowering agents, but in recent years more and more effects of statins have been revealed, including anti-inflammation, immunomodulation, neuroprotection, improvement of bone metabolism, and antitumour effects. In the past few years, extensive studies have shown that statins can induce autophagy in tumour cells as well as in some normal cells, and autophagy may be involved in the regulation of cancer metastasis. This review is focused on summarising and discussing the relationships among statins, autophagy and cancer metastasis. Studies showed that activation of the AMPK-TOR signalling pathway may be a major mechanism of statin-induced autophagy. Depleting cellular geranylgeranyl diphosphate activates AMPK and inactivates TOR, leading to autophagic responses. Autophagy, a strategy of self-adaption, is a double-edged sword in tumour metastasis. On one hand, autophagy contributes to anti-metastasis activity by, for example, restricting tumour necrosis and inflammatory cell infiltration of tumours and promoting the release of high-mobility group box protein 1 that triggers strong antitumour immune responses. On the other hand, it also exhibits a pro-metastasis activity. In summary, we propose a working hypothesis: statins induce autophagy in cancer cells, and this constitutes, at least in part, the basis for the anti-metastatic effect of statins. The idea that autophagy is responsible for statin-induced anti-metastasis effects is probably novel, and it extends the conventional view that interference of the post-translational modification of Rho GTPases by statins prevents tumour metastasis.

Anoikis resistance: an essential prerequisite for tumor metastasis

Metastasis is a multistep process including dissociation of cancer cells from primary sites, survival in the vascular system, and proliferation in distant target organs. As a barrier to metastasis, cells normally undergo an apoptotic process known as “anoikis,” a form of cell death due to loss of contact with the extracellular matrix or neighboring cells. Cancer cells acquire anoikis resistance to survive after detachment from the primary sites and travel through the circulatory and lymphatic systems to disseminate throughout the body. Because recent technological advances enable us to detect rare circulating tumor cells, which are anoikis resistant, currently, anoikis resistance becomes a hot topic in cancer research. Detailed molecular and functional analyses of anoikis resistant cells may provide insight into the biology of cancer metastasis and identify novel therapeutic targets for prevention of cancer dissemination. This paper comprehensively describes recent investigations of the molecular and cellular mechanisms underlying anoikis and anoikis resistance in relation to intrinsic and extrinsic death signaling, epithelial-mesenchymal transition, growth factor receptors, energy metabolism, reactive oxygen species, membrane microdomains, and lipid rafts.