Histone deacetylase inhibition prevents the growth of primary and metastatic osteosarcoma

Advancements in Osteosarcoma Therapy: Overcoming Chemotherapy Resistance and Exploring Novel Pharmacological Strategies

Osteosarcoma is recognized as the most prevalent primary bone malignancy, primarily affecting children and adolescents. It is characterized by its aggressive behavior and high metastatic potential, which often leads to poor patient outcomes. Despite advancements in surgical techniques and chemotherapy regimens, the prognosis for patients with osteosarcoma remains unsatisfactory, with survival rates plateauing over the past few decades. A significant barrier to effective treatment is the development of chemotherapy resistance, which complicates the management of the disease and contributes to high rates of recurrence. This review article aims to provide a comprehensive overview of recent advancements in osteosarcoma therapy, particularly in overcoming chemotherapy resistance. We begin by discussing the current standard treatment modalities, including surgical resection and conventional chemotherapy agents such as methotrexate, doxorubicin, and cisplatin. While these approaches have been foundational in managing osteosarcoma, they are often limited by adverse effects and variability in efficacy among patients. To address these challenges, we explore novel pharmacological strategies that aim to enhance treatment outcomes. This includes targeted therapies focusing on specific molecular alterations in osteosarcoma cells and immunotherapeutic approaches designed to harness the body's immune system against tumors. Additionally, we review innovative drug delivery systems that aim to improve the bioavailability and efficacy of existing treatments while minimizing toxicity. The review also assesses the mechanisms underlying chemotherapy resistance, such as drug efflux mechanisms, altered metabolism, and enhanced DNA repair pathways. By synthesizing current research findings, we aim to highlight the potential of new therapeutic agents and strategies for overcoming these resistance mechanisms. Ultimately, this article seeks to inform future research directions and clinical practices, underscoring the need for continued innovation in treating osteosarcoma to improve patient outcomes and survival rates.

Whole-Exome Analysis and Osteosarcoma: A Game Still Open

Osteosarcoma (OS) is the most prevalent malignant bone tumor in adolescents and young adults. OS cells grow in a permissive local microenvironment which modulates their behavior and facilitates all steps in tumor development (e.g., proliferation/quiescence, invasion/migration, and drug resistance) and contributes to their intrinsic heterogeneity. The lung parenchyma is the most common metastatic site in OS, and metastatic foci are frequently associated with a poor clinical outcome. Although multiple factors may be responsible for the disease, including genetic mutations (e.g., Rb and p53), the molecular mechanism of development of OS remains unclear, and the conventional treatment for OS is still based on a sequential approach that combines chemotherapy and surgery. Also, despite the increase in clinical trials, the survival rates for OS have not improved. Non-specific targeting therapies thus show poor therapeutic effects, along with side effects at high doses. For these reasons, many efforts have been made to characterize the complex genome of OS thanks to the whole-exome analysis, with the aim of identifying predictive biomarkers to give these patients a better therapeutic option. This review aims to summarize and discuss the main recent advances in OS molecular research for precision medicine.

Histone deacetylase upregulation of neuropilin-1 in osteosarcoma is essential for pulmonary metastasis

The lungs represent the most common site of metastasis for osteosarcoma (OS). Despite our advances in developing targeted therapies for treating solid malignancies, broad acting chemotherapies remain the first line treatment for OS. In assaying the efficacy of approved therapeutics for non-OS malignancies, we previously identified the histone deacetylase 1 and 2 (HDAC1 and 2) inhibitor, romidepsin, as effective for the treatment of established lung metastatic OS. Yet, romidepsin has noted toxicities in humans and so here we aimed to define the primary mechanisms through which HDAC1/2 mediate OS progression to identify more selective druggable targets/pathways. Microarray and proteomics analyses of romidepsin treated OS cells revealed a significant suppression of neuropilin-1 (NRP1), a known regulator of cancer cell migration and invasion. Silencing of NRP1 significantly reduced OS proliferation, migration, invasion and adhesion in vitro. More strikingly, in vivo, reduced NRP1 expression significantly mitigated the lung metastatic potential of OS in two independent models (K7M2 and SAOS-LM7). Mechanistically, our data point to NRP1 mediating this effect via the down regulation of migration machinery, namely SRC, FAK and ROCK1 expression/activity, that is in part, related to NRP1 interaction with integrin beta 1 (ITGB1). In summary, our data indicate that romidepsin down regulation of NRP1 significantly mitigates the ability of OS cells to seed the lung and establish metastases, and that targeting NRP1 or its effectors with selective inhibitors may be a viable means with which to prevent this deadly aspect of the disease.

Acquired NF2 mutation confers resistance to TRK inhibition in an ex vivo LMNA::NTRK1-rearranged soft-tissue sarcoma cell model

Genomic rearrangements of the neurotrophic receptor tyrosine kinase genes (NTRK1, NTRK2, and NTRK3) are the most common mechanism of oncogenic activation for this family of receptors, resulting in sustained cancer cell proliferation. Several targeted therapies have been approved for tumours harbouring NTRK fusions and a new generation of TRK inhibitors has already been developed due to acquired resistance. We established a patient-derived LMNA::NTRK1-rearranged soft-tissue sarcoma cell model ex vivo with an acquired resistance to targeted TRK inhibition. Molecular profiling of the resistant clones revealed an acquired NF2 loss of function mutation that was absent in the parental cell model. Parental cells showed continuous sensitivity to TRK-targeted treatment, whereas the resistant clones were insensitive. Furthermore, resistant clones showed upregulation of the MAPK and mTOR/AKT pathways in the gene expression based on RNA sequencing data and increased sensitivity to MEK and mTOR inhibitor therapy. Drug synergy was seen using trametinib and rapamycin in combination with entrectinib. Medium-throughput drug screening further identified small compounds as potential drug candidates to overcome resistance as monotherapy or in combination with entrectinib. In summary, we developed a comprehensive model of drug resistance in an LMNA::NTRK1-rearranged soft-tissue sarcoma and have broadened the understanding of acquired drug resistance to targeted TRK therapy. Furthermore, we identified drug combinations and small compounds to overcome acquired drug resistance and potentially guide patient care in a functional precision oncology setting. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Establishment and functional testing of a novel ex vivo extraskeletal osteosarcoma cell model (USZ20-ESOS1)

Extraskeletal osteosarcoma (ESOS) is a rare malignant mesenchymal tumor that originates in the soft tissue. ESOS accounts for less than 1% of all soft tissue sarcomas and exhibits an aggressive behavior with a high propensity for local recurrence and distant metastasis. Despite advances in treatment, the prognosis for ESOS remains poor, with a five-year survival rate of less than 50% and 27% for metastatic patients. Ex vivo models derived from patient samples are critical tools for studying rare diseases with poor prognoses, such as ESOS, and identifying potential new treatment strategies. In this work, we established a novel ESOS ex vivo sarco-sphere model from a metastatic lesion to the dermis for research and functional testing purposes. The ex vivo cell model accurately recapitulated the native tumor, as evidenced by histomorphology and molecular profiles. Through a functional screening approach, we were able to identify novel individual anti-cancer drug sensitivities for different drugs such as romidepsin, miverbresib and to multiple kinase inhibitors. Overall, our new ESOS ex vivo cell model represents a valuable tool for investigating disease mechanisms and answering basic and translational research questions.

ERRα contributes to HDAC6-induced chemoresistance of osteosarcoma cells

Chemotherapy resistance is an important problem for clinical therapy of osteosarcoma (OS). The potential effects of histone deacetylases (HDACs) on OS chemoresistance are studied. The expression of HDACs in OS cells resistance to doxorubicin (Dox) and cisplatin (CDDP) is checked. Among 11 members of HDACs, levels of HDAC6 are significantly upregulated in OS cells resistance to Dox and CDDP. Inhibition of HDAC6 via its specific inhibitor ACY1215 restores chemosensitivity of OS-resistant cells. Further, HDAC6 directly binds with estrogen-related receptors alpha (ERRα) to regulate its acetylation and protein stability. Inhibition of ERRα further strengthens ACY1215-increased chemosensitivity of OS-resistant cells. Mechanistically, K129 acetylation is the key residue for HDAC6-regulated protein levels of ERRα. Collectively, we find that ERRα contributes to HDAC6-induced chemoresistance of OS cells. Inhibition of HDAC6/ERRα axis might be a potential approach to overcome chemoresistance and improve therapy efficiency for OS treatment. 1. HDAC6 was significantly upregulated in Dox and CDDP resistant OS cells; 2. Inhibition of HDAC6 can restore chemosensitivity of OS cells; 3. HDAC6 binds with ERRα at K129 to decrease its acetylation and increase protein stability; 4. ERRα contributes to HDAC6-induced chemoresistance of OS cells.

The epigenetic factor CHD4 contributes to metastasis by regulating the EZH2/β-catenin axis and acts as a therapeutic target in ovarian cancer

BACKGROUND

The overall survival rate of patients with advanced ovarian cancer (OC) has remained static for several decades. Advanced ovarian cancer is known for its poor prognosis due to extensive metastasis. Epigenetic alterations contribute to tumour progression and therefore are of interest for potential therapeutic strategies.

METHODS

Following our previous study, we identified that CHD4, a chromatin remodelling factor, plays a strong role in ovarian cancer cell metastasis. We investigated the clinical significance of CHD4 through TCGA and GEO database analyses and explored the effect of CHD4 expression modulation and romidepsin treatment on the biological behaviour of ovarian cancer through CCK-8 and transwell assays. Bioluminescence imaging of tumours in xenografted mice was applied to determine the therapeutic effect of romidepsin. GSEA and western blotting were used to screen the regulatory mechanism of CHD4.

RESULTS

In ovarian cancer patient specimens, high CHD4 expression was associated with a poor prognosis. Loss of function of CHD4 in ovarian cancer cells induced suppression of migration and invasion. Mechanistically, CHD4 knockdown suppressed the expression of EZH2 and the nuclear accumulation of β-catenin. CHD4 also suppressed the metastasis of ovarian cancer cells and prevented disease progression in a mouse model. To inhibit the functions of CHD4 that are mediated by histone deacetylase, we evaluated the effect of the HDAC1/2 selective inhibitor romidepsin. Our findings indicated that treatment with romidepsin suppressed the progression of metastases in vitro and in vivo.

CONCLUSIONS

Collectively, our results uncovered an oncogenic function of CHD4 in ovarian cancer and provide a rationale for clinical trials of romidepsin in ovarian cancer patients.

DPY30 promotes the growth and survival of osteosarcoma cell by regulating the PI3K/AKT signal pathway

Osteosarcoma (OS) is characterized by aggressive features including invasiveness and high incidence of metastasis. OS patients with metastases are difficult to treat and suffer from a poor prognosis. DPY30 (protein dpy-30 homolog) is a key component of SET1/MLL family of H3K4 methyltransferases, which is implicated in the progression of multiple cancers. However, the potential functional engagement of DPY30 in OS remains to be unveiled. The objective of this study is to investigate the potential roles of DPY30 in the regulation of malignant phenotypes of OS cells. We examined DPY30 expression from a published dataset (GSE28424) as well as in OS tissues and adjacent normal tissues from OS patients. The association of DPY30 expression level and clinicopathologic parameters was assessed by Chi-square test. The role of DPY30 in regulating the malignant phenotype of OS cells and tumorigenesis was examined by in vitro functional assays and xenograft mouse model. We reported an upregulation of DPY30 in OS tumor tissues in both published dataset and clinical samples. A high level of DPY30 expression was associated with larger tumor size and more metastasis in OS patients, as well as poor overall survival. DPY30 knockdown in OS cells significantly impairs proliferation, migration and invasion, but induced cellular apoptosis. We further demonstrated that the agonist of PI3K/AKT pathway can rescue the inhibitory effects of DPY30 knockdown in OS cells. Together, our data indicate that DPY30 functions as an oncogene to promote the malignancy of OS cells possibly through PI3K/AKT pathway. The dependency of OS cells on DPY30 overexpression is a targetable vulnerability in OS cells.

Proteasome Inhibitors and Their Potential Applicability in Osteosarcoma Treatment

Simple Summary

Bone cancer has seen minimal benefits in therapeutic options in the past 30 years. Proteasome inhibitors present a new avenue of research for the treatment of bone cancer. Proteasome inhibitors impair the function of the proteasome, a structure within the cell that removes unwanted and misfolded proteins. Bone cancer cells heavily rely on the proteasome to properly function and survive. Impairing the proteasome function can have detrimental consequences and lead to cell death. This review provides a thorough summary of the in vitro, in vivo, and clinical research that has explored proteasome inhibitors for the treatment of bone cancer.

Abstract

Osteosarcoma (OS) is the most common type of bone cancer, with ~30% of patients developing secondary/metastatic tumors. The molecular complexity of tumor metastasis and the lack of effective therapies for OS has cultivated interest in exploiting the proteasome as a molecular target for anti-cancer therapy. As our understanding towards the behavior of malignant cells expands, it is evident that cancerous cells display a greater reliance on the proteasome to maintain homeostasis and sustain efficient biological activities. This led to the development and approval of first- and second-generation proteasome inhibitors (PIs), which have improved outcomes for patients with multiple myeloma and mantle cell lymphoma. Researchers have since postulated the therapeutic potential of PIs for the treatment of OS. As such, this review aims to summarize the biological effects and latest findings from clinical trials investigating PI-based treatments for OS. Integrating PIs into current treatment regimens may better outcomes for patients diagnosed with OS.

Recent and Ongoing Research into Metastatic Osteosarcoma Treatments

The survival rate for metastatic osteosarcoma has not improved for several decades, since the introduction and refinement of chemotherapy as a treatment in addition to surgery. Over two thirds of metastatic osteosarcoma patients, many of whom are children or adolescents, fail to exhibit durable responses and succumb to their disease. Concerted efforts have been made to increase survival rates through identification of candidate therapies via animal studies and early phase trials of novel treatments, but unfortunately, this work has produced negligible improvements to the survival rate for metastatic osteosarcoma patients. This review summarizes data from clinical trials of metastatic osteosarcoma therapies as well as pre-clinical studies that report efficacy of novel drugs against metastatic osteosarcoma in vivo. Considerations regarding the design of animal studies and clinical trials to improve survival outcomes for metastatic osteosarcoma patients are also discussed.

Proteomic Assessment of Extracellular Vesicles from Canine Tissue Explants as a Pipeline to Identify Molecular Targets in Osteosarcoma: PSMD14/Rpn11 as a Proof of Principle

Osteosarcoma (OS) is a highly malignant bone tumour that has seen little improvement in treatment modalities in the past 30 years. Understanding what molecules contribute to OS biology could aid in the discovery of novel therapies. Extracellular vesicles (EVs) serve as a mode of cell-to-cell communication and have the potential to uncover novel protein signatures. In our research, we developed a novel pipeline to isolate, characterize, and profile EVs from normal bone and osteosarcoma tissue explants from canine OS patients. Proteomic analysis of vesicle preparations revealed a protein signature related to protein metabolism. One molecule of interest, PSMD14/Rpn11, was explored further given its prognostic potential in human and canine OS, and its targetability with the drug capzimin. In vitro experiments demonstrated that capzimin induces apoptosis and reduces clonogenic survival, proliferation, and migration in two metastatic canine OS cell lines. Capzimin also reduces the viability of metastatic human OS cells cultured under 3D conditions that mimic the growth of OS cells at secondary sites. This unique pipeline can improve our understanding of OS biology and identify new prognostic markers and molecular targets for both canine and human OS patients.

miRNA ‐34c suppresses osteosarcoma progression in vivo by targeting Notch and E2F

The expression of microRNAs (miRNAs) is dysregulated in many types of cancers including osteosarcoma (OS) due to genetic and epigenetic alterations. Among these, miR‐34c, an effector of tumor suppressor P53 and an upstream negative regulator of Notch signaling in osteoblast differentiation, is dysregulated in OS. Here, we demonstrated a tumor suppressive role of miR‐34c in OS progression using in vitro assays and in vivo genetic mouse models. We found that miR‐34c inhibits the proliferation and the invasion of metastatic OS cells, which resulted in reduction of the tumor burden and increased overall survival in an orthotopic xenograft model. Moreover, the osteoblast‐specific overexpression of miR‐34c increased survival in the osteoblast specific p53 mutant OS mouse model. We found that miR‐34c regulates the transcription of several genes in Notch signaling (NOTCH1, JAG1, and HEY2) and in p53‐mediated cell cycle and apoptosis (CCNE2, E2F5, E2F2, and HDAC1). More interestingly, we found that the metastatic‐free survival probability was increased among a patient cohort from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) OS, which has lower expression of direct targets of miR‐34c that was identified in our transcriptome analysis, such as E2F5 and NOTCH1. In conclusion, we demonstrate that miR‐34c is a tumor suppressive miRNA in OS progression in vivo. In addition, we highlight the therapeutic potential of targeting miR‐34c in OS. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Combining histone deacetylase inhibitors (HDACis) with other therapies for cancer therapy

Histone deacetylases (HDACs) play an important role in regulating the expression of genes involved in tumorigenesis and tumor maintenance, and hence they have been considered as key targets in cancer therapy. As a novel category of antitumor agents, histone deacetylase inhibitors (HDACis) can induce cell cycle arrest, apoptosis, and differentiation in cancer cells, ultimately combating cancer. Although in the United States, the use of HDACis for the treatment of certain cancers has been approved, the therapeutic efficacy of HDACis as a single therapeutic agent in solid tumorshas been unsatisfactory and drug resistance may yet occur. To enhance therapeutic efficacy and limit drug resistance, numerous combination therapies involving HDACis in synergy with other antitumor therapies have been studied. In this review, we describe the classification of HDACs. Moreover, we summarize the antitumor mechanism of the HDACis for targeting key cellular processes of cancers (cell cycle, apoptosis, angiogenesis, DNA repair, and immune response). In addition, we outline the major developments of other antitumor therapies in combination with HDACis, including chemotherapy, radiotherapy, phototherapy, targeted therapy, and immunotherapy. Finally, we discuss the current state and challenges of HDACis-drugs combinations in future clinical studies, with the aim of optimizing the antitumor effect of such combinations.

Osteosarcoma mechanobiology and therapeutic targets

Osteosarcoma (OS) is the one of the most common primary tumors of bone with less than a 20% 5-year survival rate after the development of metastases. OS is highly predisposed in Paget's disease (PD) of bone, and both have common characteristic skeletal features due to rapid bone remodeling. OS prognosis is location dependent which further emphasizes the likely contribution of the bone microenvironment in its pathogenesis. Mechanobiology is the phenomenon when mechanical cues from the changing physical microenvironment of bone are transduced to biological pathways through mechanosensitive cellular components. Mechanobiology-driven therapies have been used for curbing tumor progression by direct alteration of the physical microenvironment or inhibition of metastasis-associated mechanosensitive proteins. This review emphasizes the contribution of mechanobiology to OS progression, and sheds light on current mechanobiology-based therapies and potential new targets for improving disease management. Additionally, the variety of 3D models currently used to study OS mechanobiology are summarized.

Charting a path for prioritization of novel agents for clinical trials in osteosarcoma: A report from the Children's Oncology Group New Agents for Osteosarcoma Task Force

Osteosarcoma is the most common bone tumor in children and young adults. Metastatic and relapsed disease confer poor prognosis, and there have been no improvements in outcomes for several decades. The disease's biological complexity, lack of drugs developed specifically for osteosarcoma, imperfect preclinical models, and limits of existing clinical trial designs have contributed to lack of progress. The Children's Oncology Group Bone Tumor Committee established the New Agents for Osteosarcoma Task Force to identify and prioritize agents for inclusion in clinical trials. The group identified multitargeted tyrosine kinase inhibitors, immunotherapies targeting B7-H3, CD47-SIRPα inhibitors, telaglenastat, and epigenetic modifiers as the top agents of interest. Only multitargeted tyrosine kinase inhibitors met all criteria for frontline evaluation and have already been incorporated into an upcoming phase III study concept. The task force will continue to reassess identified agents of interest as new data become available and evaluate novel agents using this method.

Selective Targeting of Class I Histone Deacetylases in a Model of Human Osteosarcoma

Dysregulation of histone deacetylases (HDACs) is associated with the pathogenesis of human osteosarcoma, which may present an epigenetic vulnerability as well as a therapeutic target. Domatinostat (4SC-202) is a next-generation class I HDAC inhibitor that is currently being used in clinical research for certain cancers, but its impact on human osteosarcoma has yet to be explored. In this study, we report that 4SC-202 inhibits osteosarcoma cell growth in vitro and in vivo. By analyzing cell function in vitro, we show that the anti-tumor effect of 4SC-202 involves the combined induction of cell-cycle arrest at the G2/M phase and apoptotic program, as well as a reduction in cell invasion and migration capabilities. We also found that 4SC-202 has little capacity to promote osteogenic differentiation. Remarkably, 4SC-202 revised the global transcriptome and induced distinct signatures of gene expression in vitro. Moreover, 4SC-202 decreased tumor growth of established human tumor xenografts in immunodeficient mice in vivo. We further reveal key targets regulated by 4SC-202 that contribute to tumor cell growth and survival, and canonical signaling pathways associated with progression and metastasis of osteosarcoma. Our study suggests that 4SC-202 may be exploited as a valuable drug to promote more effective treatment of patients with osteosarcoma and provide molecular insights into the mechanism of action of class I HDAC inhibitors.

Targeted and immuno-based therapies in sarcoma: mechanisms and advances in clinical trials

Sarcomas represent a distinct group of rare malignant tumors with high heterogeneity. Limited options with clinical efficacy for the metastatic or local advanced sarcoma existed despite standard therapy. Recently, targeted therapy according to the molecular and genetic phenotype of individual sarcoma is a promising option. Among these drugs, anti-angiogenesis therapy achieved favorable efficacy in sarcomas. Inhibitors targeting cyclin-dependent kinase 4/6, poly-ADP-ribose polymerase, insulin-like growth factor-1 receptor, mTOR, NTRK, metabolisms, and epigenetic drugs are under clinical evaluation for sarcomas bearing the corresponding signals. Immunotherapy represents a promising and favorable method in advanced solid tumors. However, most sarcomas are immune "cold" tumors, with only alveolar soft part sarcoma and undifferentiated pleomorphic sarcoma respond to immune checkpoint inhibitors. Cellular therapies with TCR-engineered T cells, chimeric antigen receptor T cells, tumor infiltrating lymphocytes, and nature killer cells transfer show therapeutic potential. Identifying tumor-specific antigens and exploring immune modulation factors arguing the efficacy of these immunotherapies are the current challenges. This review focuses on the mechanisms, advances, and potential strategies of targeted and immune-based therapies in sarcomas.

Targeting Histone Modifications in Bone and Lung Metastatic Cancers

PURPOSE OF REVIEW

Breast cancer frequently metastasizes to the bone and lung, but the ability to treat metastatic tumor cells remains a pressing clinical challenge. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) have emerged as promising targets since these enzymes are aberrantly expressed in numerous cancers and regulate the expression of genes that drive tumorigenesis and metastasis. This review focuses on the abnormal expression of histone-modifying enzymes in cancers that have a high tropism for the bone and lung and explores the clinical use of histone deacetylase inhibitors for the treatment and prevention of metastasis to these sites.

RECENT FINDINGS

Preclinical studies have demonstrated that the role for HDACs is highly dependent on tumor type and stage of disease progression. HDAC inhibitors can induce apoptosis, senescence, cell differentiation, and tumor dormancy genes and inhibit angiogenesis, making these promising therapeutics for the treatment of metastatic disease. HDAC inhibitors are already FDA approved for hematologic malignancies and are in clinical trials with standard-of-care chemotherapies and targeted agents for several solid tumors, including cases of metastatic disease. However, these drugs can negatively impact bone homeostasis. Although HDAC inhibitors are not currently administered for the treatment of bone and lung metastatic disease, preclinical studies have shown that these drugs can reduce distant metastasis by targeting molecular factors and signaling pathways that drive tumor cell dissemination to these sites. Thus, HDAC inhibitors in combination with bone protective therapies may be beneficial in the treatment of bone metastatic cancers.

Melittin inhibits lung metastasis of human osteosarcoma: Evidence of wnt/β-catenin signaling pathway participation

Melittin is a major active peptide component of bee venom that has been demonstrated to show anti-tumor effects. Osteosarcoma is a type of bone tumor with a high degree of malignancy, and metastasis is the main challenge of osteosarcoma therapy. This study aimed to investigate the role of melittin in the lung metastasis of osteosarcoma. 143 B cells were treated with different concentrations of melittin in vitro. Wound-healing and transwell assays were performed to determine the cell migration and invasion potential. Quantitative real-time PCR and Western blot experiments were performed to evaluate the expression levels of Wnt/β-catenin signaling pathway-related factors after treatment with melittin. The orthotopic implantation model and hematoxylin-eosin staining were used to investigate the effect of melittin treatment on tumor formation and lung metastasis. Immunohistochemical staining and Western blot experiments were performed to indicate the melittin-mediated expression changes in Wnt/β-catenin signaling pathway-related factors. The cell migration and invasion potential were observed to be inhibited in a dose-dependent manner upon treatment with melittin. Treatment with medium and high concentrations of melittin attenuated the mRNA and protein expression of LRP5, β-catenin, MMP-2, cyclin D, c-Myc, survivin, MMP-9, and VEGF genes in vitro. Melittin significantly inhibited the growth of tibia xenografts in nude mice and decreased the number of lung metastatic nodules. Consistent with the results observed in vitro, treatment with melittin at medium and high concentrations attenuated the expression of Wnt/β-catenin signaling pathway-related factors in vivo. In vitro, Wnt/β-catenin signaling pathway was involved in Melittin-mediated -migration and invasion potential of 143 B cells. Similarly, as observed in the in vivo experiments, Wnt/β-catenin signaling pathway was also associated with the role of melittin on lung metastasis of osteosarcomas.

Patient Derived Xenografts for Genome-Driven Therapy of Osteosarcoma

Osteosarcoma (OS) is a rare malignant primary tumor of mesenchymal origin affecting bone. It is characterized by a complex genotype, mainly due to the high frequency of chromothripsis, which leads to multiple somatic copy number alterations and structural rearrangements. Any effort to design genome-driven therapies must therefore consider such high inter- and intra-tumor heterogeneity. Therefore, many laboratories and international networks are developing and sharing OS patient-derived xenografts (OS PDX) to broaden the availability of models that reproduce OS complex clinical heterogeneity. OS PDXs, and new cell lines derived from PDXs, faithfully preserve tumor heterogeneity, genetic, and epigenetic features and are thus valuable tools for predicting drug responses. Here, we review recent achievements concerning OS PDXs, summarizing the methods used to obtain ectopic and orthotopic xenografts and to fully characterize these models. The availability of OS PDXs across the many international PDX platforms and their possible use in PDX clinical trials are also described. We recommend the coupling of next-generation sequencing (NGS) data analysis with functional studies in OS PDXs, as well as the setup of OS PDX clinical trials and co-clinical trials, to enhance the predictive power of experimental evidence and to accelerate the clinical translation of effective genome-guided therapies for this aggressive disease.