Down regulation of Wnt signaling mitigates hypoxia-induced chemoresistance in human osteosarcoma cells

Wnt/β-catenin signaling pathway: an attractive potential therapeutic target in osteosarcoma

Osteosarcoma (OS) is the most common bone malignancy in children and adolescents, and although current neoadjuvant chemotherapy has shown efficacy against OS, the long-term survival rate for patients with OS remains low, highlighting the need to find more effective treatments. In cancer cells, abnormal activation of signaling pathways can widely affect cell activity from growth and proliferation to apoptosis, invasion and metastasis. Wnt/β-catenin is a complex and unique signaling pathway that is considered to be one of the most important carcinogenic pathways in human cancer. Research have confirmed that the Wnt/β-catenin signaling pathway is an important driving factor for the occurrence and development of osteosarcoma, and abnormal activation of this pathway can promote the pathological processes of cell proliferation, invasion, migration, tumor angiogenesis and chemical resistance of osteosarcoma. However, inhibition of Wnt/β-catenin signaling pathway can effectively inhibit or reverse the above pathological processes. Therefore, manipulating the expression or function of the Wnt/β-catenin pathway may be a potential targeted pathway for the treatment of OS. In this review, we describe the characteristics of the Wnt/β-catenin signaling pathway and summarize the role and mechanism of this pathway in OS. This paper discusses the therapeutic significance of inhibiting or targeting Wnt/β-catenin pathway in OS and the shortcomings of current studies on this pathway in OS and the problems to be solved. This review helps us to understand the role of Wnt/β-catenin on OS, and provides a theoretical basis and new ideas for targeting Wnt/β-catenin pathway as a therapeutic target for OS.

Exosomes in Bone Cancer: Unveiling their Vital Role in Diagnosis, Prognosis, and Therapeutic Advancements

Bone cancer among adolescents and children exhibits varying survival outcomes based on disease state. While localized bone cancer cases have a survival rate exceeding 70%, metastatic, refractory, and recurrent forms are associated with significantly poorer prognoses. Initially believed to be mere vehicles for cellular waste disposal, exosomes are now recognized as extracellular vesicles facilitating intercellular communication. These vesicles influence cellular behaviors by transporting various biomolecules, such as proteins, DNA, RNA, and lipids, among cells. The role of exosomes in regulating the progression of bone cancer is increasingly evident, impacting critical processes like tumorigenesis, proliferation, metastasis, angiogenesis, immune evasion, and drug resistance. Current research underscores the substantial potential of exosomes in promoting the progression and development of bone cancer. This review delves into the complex process of exosome biogenesis, the variety of cell-derived exosome sources, and their applications in drug delivery and therapeutics. It also examines ongoing clinical trials focused on exosome cargo levels and discusses the challenges and future directions in exosome research. Unlike costly and invasive traditional diagnostic methods, exosomal biomarkers offer a non-invasive, cost-effective, and readily accessible routine screening through simple fluid collection that aims to inspire researchers to investigate the potential of exosomes for cancer theragnostic. Through comprehensive exploration of these areas, the review seeks to enhance understanding and foster innovative solutions to cancer biology in the near future.

Hypoxia differently regulates the proportion of ALDHhi cells in lung squamous carcinoma H520 and adenocarcinoma A549 cells via the Wnt/β-catenin pathway

BACKGROUND

Cancer stem cells (CSCs) are a specific subpopulation of cancer cells with the ability of self-renewal, infinite proliferation, multidifferentiation and tumorigenicity, and play critical roles in cancer progression and treatment resistance. CSCs are tightly regulated by the tumor microenvironment, such as hypoxia; however, how hypoxia regulates CSCs in non-small cell lung cancer (NSCLC) remains unclear.

METHODS

The proportion of ALDHhi cells was examined using the Aldefluor assay. Tankyrase inhibitor XAV939 and siRNA were used to inhibit β-catenin while pcDNA3-β-catenin (S33Y) plasmid enhanced the expression of β-catenin. Western blot was administered for protein detection. The mRNA expression was measured by quantitative real-time PCR.

RESULTS

We found that hypoxia led to an increase in the proportion of ALDHhi cells in lung squamous carcinoma (LUSC) H520 cells, while causing a decrease in the ALDHhi cell proportion in lung adenocarcinoma (LUAD) A549 cells. Similarly, β-catenin expression was upregulated in H520 cells but downregulated in A549 cells upon exposure to hypoxia. Mechanically, the proportion of ALDHhi cells in both cell lines was decreased by β-catenin inhibitor or siRNA knockdown, whereas increased after β-catenin overexpression. Furthermore, hypoxia treatment suppressed E-cadherin expression in H520 cells and enhanced N-cadherin and β-catenin expression, while this effect was completely opposite in A549 cells.

CONCLUSION

The hypoxia-EMT-β-catenin axis functions as an important regulator for the proportion of CSCs in NSCLC and could potentially be explored as therapeutic targets in the future.

P53‑microRNA interactions regulate the response of colorectal tumor cells to oxaliplatin under normoxic and hypoxic conditions

Oxaliplatin (OXA)‑containing regimens are used as first‑line chemotherapy in colorectal cancer (CRC). However, OXA resistance remains a major challenge in CRC treatment. CRC cells that adapt to hypoxia can potentially develop OXA resistance, and the underlying molecular mechanisms still need to be further investigated. In the current study, the OXA drug sensitivity of two CRC cell lines, HCT116 (TP53WT) and HT29 (TP53MT), was compared under both normoxic and hypoxic conditions. It was found that under normoxic condition, HCT116 cells showed significantly higher OXA sensitivity than HT29 cells. However, both cell lines showed remarkable OXA resistance under hypoxic conditions. It was also revealed that P53 levels were increased after OXA and hypoxia treatment in HCT116 cells but not in HT29 cells. Notably, knocking down P53WT decreased normoxic but increased hypoxic OXA sensitivity in HCT116 cells, which did not exist in HT29 cells. Molecular analysis indicated that P53WT activated microRNA (miR)‑26a and miR‑34a in OXA treatment and activated miR‑23a in hypoxia treatment. Cell proliferation experiments indicated that a high level of miR‑23a decreased OXA sensitivity and that a high level of miR‑26a or miR‑34a increased OXA sensitivity in HCT116 cells. Additionally, it was demonstrated that miR‑26a, miR‑34a and miR‑23a affect cell apoptosis through regulation of MCL‑1, EZH2, BCL‑2, SMAD 4 and STAT3. Taken together, the present findings revealed the dual function of P53 in regulating cellular chemo‑sensitivity and highlighted the role of P53‑miR interactions in the response of CRC cells to OXA chemotherapy under normoxic and hypoxic conditions.

Mitochondrial leak metabolism induces the Spemann-Mangold Organizer via Hif-1α in Xenopus

An instructive role for metabolism in embryonic patterning is emerging, although a role for mitochondria is poorly defined. We demonstrate that mitochondrial oxidative metabolism establishes the embryonic patterning center, the Spemann-Mangold Organizer, via hypoxia-inducible factor 1α (Hif-1α) in Xenopus. Hypoxia or decoupling ATP production from oxygen consumption expands the Organizer by activating Hif-1α. In addition, oxygen consumption is 20% higher in the Organizer than in the ventral mesoderm, indicating an elevation in mitochondrial respiration. To reconcile increased mitochondrial respiration with activation of Hif-1α, we discovered that the "free" c-subunit ring of the F1Fo ATP synthase creates an inner mitochondrial membrane leak, which decouples ATP production from respiration at the Organizer, driving Hif-1α activation there. Overexpression of either the c-subunit or Hif-1α is sufficient to induce Organizer cell fates even when β-catenin is inhibited. We propose that mitochondrial leak metabolism could be a general mechanism for activating Hif-1α and Wnt signaling.

Effects of microenvironment in osteosarcoma on chemoresistance and the promise of immunotherapy as an osteosarcoma therapeutic modality

Osteosarcoma (OS) is one of the most common primary malignant tumors originating in bones. Its high malignancy typically manifests in lung metastasis leading to high mortality. Although remarkable advances in surgical resection and neoadjuvant chemotherapy have lengthened life expectancy and greatly improved the survival rate among OS patients, no further breakthroughs have been achieved. It is challenging to treat patients with chemoresistant tumors and distant metastases. Recent studies have identified a compelling set of links between hypoxia and chemotherapy failure. Here, we review the evidence supporting the positive effects of hypoxia in the tumor microenvironment (TME). In addition, certain anticancer effects of immune checkpoint inhibitors have been demonstrated in OS preclinical models. Continued long-term observation in clinical trials is required. In the present review, we discuss the mutualistic effects of the TME in OS treatment and summarize the mechanisms of immunotherapy and their interaction with TME when used to treat OS. We also suggest that immunotherapy, a new comprehensive and potential antitumor approach that stimulates an immune response to eliminate tumor cells, may represent an innovative approach for the development of a novel treatment regimen for OS patients.

HIF-1α stimulates the progression of oesophageal squamous cell carcinoma by activating the Wnt/β-catenin signalling pathway

BACKGROUND

This study aimed to clarify the significance of the crosstalk between hypoxia-inducible factor-1α (HIF-1α) and the Wnt/β-catenin pathway in oesophageal squamous cell carcinoma (ESCC).

METHODS

The oncogenic role of HIF-1α in ESCC was investigated using in vitro and in vivo assays. The clinicopathological significance of HIF-1α, β-catenin and TCF4/TCF7L2 in ESCC were evaluated using quantitative real-time PCR and immunohistochemistry.

RESULTS

The expression level of HIF-1α, β-catenin, and TCF4/TCF7L2 in T.Tn and TE1 cell lines were elevated under hypoxia in vitro. HIF-1α knockdown suppressed proliferation, migration/invasion and epithelial-mesenchymal transition (EMT) progression, induced G0/G1 cell cycle arrest, promoted apoptosis and inhibited 5-fluorouracil chemoresistance in vitro. In vivo assays showed that HIF-1α is essential in maintaining tumour growth, angiogenesis, and 5-fluorouracil chemoresistance. Mechanically, we identified the complex between HIF-1α and β-catenin, HIF-1α can directly bind to the promoter region of TCF4/TCF7L2. The mRNA level of HIF-1α, β-catenin and TCF4/TCF7L2 were increased in ESCC tumour tissues compared to the corresponding non-tumour tissues. High levels of HIF-1α and TCF4/TCF7L2 expression were correlated with aggressive phenotypes and poor prognosis in ESCC patients.

CONCLUSIONS

HIF-1α serves as an oncogenic transcriptional factor in ESCC, probably by directly targeting TCF4/TCF7L2 and activating the Wnt/β-catenin pathway.

Plateau Adaptation Gene Analyses Reveal Transcriptomic, Proteomic, and Dual Omics Expression in the Lung Tissues of Tibetan and Yorkshire Pigs

Elevated environments such as plateaus are often classified as low oxygen environments. The hypoxic adaptation mechanisms utilized by organisms in these conditions are not well understood. To address this, the differentially expressed genes (DEGs) involved in hypoxia adaptation were assessed using two pig breeds (Tibetan pig [TP] and Yorkshire sow [YY]). Genes related to lung tissue responses to hypoxia were assessed using transcriptomic (using RNA-seq) and proteomic (using iTRAQ) analysis. A total of 1021 DEGs were screened out. In the iTRAQ omics data, a total of 22,100 peptides were obtained and 4518 proteins were found after filtering. A total of 271 differentially expressed proteins [DEPs] were screened using the conditions of p < 0.05; FC ≤ 0.833; and FC ≥ 1.2. A total of 14 DEGs at the mRNA and protein levels were identified and found to be associated with regulation of the inflammatory response; blood particles; and MAPK cascade response regulation. Among the DEGs, six were associated with hypoxia adaptation function (mitochondria and glycolysis) in pigs. The results of this study identify novel candidate genes involved in porcine hypoxia adaptation mechanisms.

Cancer Stem Cells as a Source of Drug Resistance in Bone Sarcomas

Bone sarcomas are commonly characterized by a high degree of intra-tumor heterogeneity, which in part is due to the presence of subpopulations of tumor cells presenting stem cell properties. Similar to normal stem cells, these cancer stem cells (CSCs) display a drug resistant phenotype and therefore are responsible for relapses and tumor dissemination. Drug resistance in bone sarcomas could be enhanced/modulated during tumor evolution though the acquisition of (epi)-genetic alterations and the adaptation to changing microenvironments, including drug treatments. Here we summarize findings supporting the involvement of pro-stemness signaling in the development of drug resistance in bone sarcomas. This include the activation of well-known pro-stemness pathways (Wnt/β-Cat, NOTCH or JAT/STAT pathways), changes in the metabolic and autophagic activities, the alteration of epigenetic pathways, the upregulation of specific non-coding RNAs and the crosstalk with different microenvironmental factors. This altered signaling is expected to be translated to the clinic in the form of biomarkers of response and new therapies able to overcome drug resistance.

High expression of ABCG2 is associated with chemotherapy resistance of osteosarcoma

Objectives

Previous studies showed overexpression of ABCG2 in a variety of tumor tissues, which could potentially indicate the probability of chemotherapy resistance. This study aimed to reveal the role of ABCG2 in the development of chemotherapy resistance and the prognosis of osteosarcoma (OS).

Methods

Sixty-eight OS patients were included in this study. Tumor tissues were collected for each patient during surgery. DOX-resistant OS cell lines were induced by consecutive exposure of gradually increasing concentration of DOX to the parental cell lines. Lentivirus was used for the knockdown of ABCG2 in OS cells. Cells were treated with the gradient concentration of DOX, and the viability was assessed by CCK8 assay. Total RNA was isolated from the tumor tissues or tumor cells, and the expression of ABCG2 was analyzed by qPCR. The relationship between ABCG2 expression and clinicopathological characteristics of the patients was analyzed using Student’s t test or the Chi-square test. The overall survival time was calculated by the Kaplan-Meier method and analyzed by the log-rank test. p < 0.05 was considered statistically significant.

Results

DOX-resistant OS cells were successfully established through continuous exposure to DOX. Forty-eight hours after DOX exposure, the IC 50 value of DOX-resistant HOS cells and DOX-resistant U2OS was 3.5 μM and 3.25 μM, respectively. By contrast, those of the untreated HOS and U2OS cells were 1.15 μM and 0.93 μM, respectively (p < 0.01). The mRNA expression level of ABCG2 was significantly increased in DOX-resistant cell lines. The CCK-8 assay showed that the DOX-resistant HOS cells and DOX-resistant U2OS cells transfected with ShABCG2 were more sensitive to the DOX treatment than those transfected with ShCtrl. Analysis of gene expression in OS tissues showed remarkably higher expression of ABCG2 as compared with adjacent normal tissues (p < 0.01). Patients with high expression level of ABCG2 had obviously decreased overall survival time than the patients with normal expression (p < 0.01).

Conclusions

ABCG2 expression level was significantly associated with the resistance to chemotherapy and the overall survival of OS patients. ABCG2 may be a promising therapeutic target for OS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02204-z.

Recent Insights into Therapy Resistance in Osteosarcoma

Osteosarcoma, the most common bone malignancy of childhood, has been a challenge to treat and cure. Standard chemotherapy regimens work well for many patients, but there remain minimal options for patients with progressive or resistant disease, as clinical trials over recent decades have failed to significantly improve survival. A better understanding of therapy resistance is necessary to improve current treatments and design new strategies for future treatment options. In this review, we discuss known mechanisms and recent scientific advancements regarding osteosarcoma and its patterns of resistance against chemotherapy, radiation, and other newly-introduced therapeutics.

Sarcoma treatment in the era of molecular medicine

Sarcomas are heterogeneous and clinically challenging soft tissue and bone cancers. Although constituting only 1% of all human malignancies, sarcomas represent the second most common type of solid tumors in children and adolescents and comprise an important group of secondary malignancies. More than 100 histological subtypes have been characterized to date, and many more are being discovered due to molecular profiling. Owing to their mostly aggressive biological behavior, relative rarity, and occurrence at virtually every anatomical site, many sarcoma subtypes are in particular difficult-to-treat categories. Current multimodal treatment concepts combine surgery, polychemotherapy (with/without local hyperthermia), irradiation, immunotherapy, and/or targeted therapeutics. Recent scientific advancements have enabled a more precise molecular characterization of sarcoma subtypes and revealed novel therapeutic targets and prognostic/predictive biomarkers. This review aims at providing a comprehensive overview of the latest advances in the molecular biology of sarcomas and their effects on clinical oncology; it is meant for a broad readership ranging from novices to experts in the field of sarcoma.

The role of circular RNAs in therapy resistance of patients with solid tumors

Circular RNAs (circRNAs) are a type of single-stranded RNA molecules forming a covalently closed, continuous structure, lacking 5'-3' polarity and polyadenylated tails. Recent advances in high-throughput sequencing technologies have revealed that these molecules are abundant, resistant to degradation and often expressed in a tissue- or developmental stage-specific manner. circRNAs are produced by back-splicing circularization of primary transcripts and exhibit a variety of functions, including regulation of transcription, translation and cellular localization. This review focuses on differentially expressed circRNAs conferring therapy resistance or sensitivity of solid tumors, such as carcinomas, sarcomas and lymphomas. Deregulated circRNAs can participate in the development of resistance to treatment by modulating regulatory pathways and cellular processes, including the mitogen-activated protein kinase pathway, epithelial-mesenchymal transition, apoptosis and autophagy.

Focus on Hypoxia-Related Pathways in Pediatric Osteosarcomas and Their Druggability

Osteosarcoma is the most frequent primary bone tumor diagnosed during adolescence and young adulthood. It is associated with the worst outcomes in the case of poor response to chemotherapy and in metastatic disease. While no molecular biomarkers are clearly and currently associated with those worse situations, the study of pathways involved in the high level of tumor necrosis and in the immune/metabolic intra-tumor environment seems to be a way to understand these resistant and progressive osteosarcomas. In this review, we provide an updated overview of the role of hypoxia in osteosarcoma oncogenesis, progression and during treatment. We describe the role of normoxic/hypoxic environment in normal tissues, bones and osteosarcomas to understand their role and to estimate their druggability. We focus particularly on the role of intra-tumor hypoxia in osteosarcoma cell resistance to treatments and its impact in its endogenous immune component. Together, these previously published observations conduct us to present potential perspectives on the use of therapies targeting hypoxia pathways. These therapies could afford new treatment approaches in this bone cancer. Nevertheless, to study the osteosarcoma cell druggability, we now need specific in vitro models closely mimicking the tumor, its intra-tumor hypoxia and the immune microenvironment to more accurately predict treatment efficacy and be complementary to mouse models.

ROS Dependent Wnt/β-Catenin Pathway and Its Regulation on Defined Micro-Pillars-A Combined In Vitro and In Silico Study

The physico-chemical surface design of implants influences the surrounding cells. Osteoblasts on sharp-edged micro-topographies revealed an impaired cell phenotype, function and Ca2+ mobilization. The influence of edges and ridges on the Wnt/β-catenin pathway in combination with the cells' stress response has not been clear. Therefore, MG-63 osteoblasts were studied on defined titanium-coated micro-pillars (5 × 5 × 5 µm) in vitro and in silico. MG-63s on micro-pillars indicated an activated state of the Wnt/β-catenin pathway. The β-catenin protein accumulated in the cytosol and translocated into the nucleus. Gene profiling indicated an antagonism mechanism of the transcriptional activity of β-catenin due to an increased expression of inhibitors like ICAT (inhibitor of β-catenin and transcription factor-4). Cells on pillars produced a significant reactive oxygen species (ROS) amount after 1 and 24 h. In silico analyses provided a detailed view on how transcriptional activity of Wnt signaling is coordinated in response to the oxidative stress induced by the micro-topography. Based on a coordinated expression of regulatory elements of the Wnt/β-catenin pathway, MG-63s are able to cope with an increased accumulation of β-catenin on micro-pillars and suppress an unintended target gene expression. Further, β-catenin may be diverted into other signaling pathways to support defense mechanisms against ROS.

Osteomimetic matrix components alter cell migration and drug response in a 3D tumour-engineered osteosarcoma model

Osteosarcoma management continues to lack the appropriate prognostic tools to assign personalised treatment. This leaves non-responders to standard care vulnerable to recurring disease and pulmonary metastases. Developing 3D in vitro disease models to serve as a test bed for personalised treatment is a promising approach to address this issue. This study describes the generation of 3D osteosarcoma models termed "tumouroids", which are geometrically compartmentalised to reproduce the bone cancer mass and its surrounding. Although the tumour microenvironment impacts osteosarcoma in many ways, this model focussed on interrogating the influence of a biomimetic matrix on tumour cell behaviour. The 3D matrix was supplemented with the bone-marrow proteins laminin, fibronectin and NuOss® bone granules. This led to increased invasion of osteosarcoma cell aggregates from within the bone-like matrix into the surrounding acellular bone marrow-like ECM. The presence of bone granules also yielded an atypical molecular profile of osteosarcoma cells, suggesting malignant metabolic reprogramming. Changes include decreased MMP-9 (p < 0.05) and increased PTEN (p < 0.05), MCP-1 (p < 0.01) and MCT-4 (p < 0.05) gene expression. This complex 3D biomimetic composition also changed cellular responses to doxorubicin, a common chemotherapeutic agent used to treat osteosarcoma, and reproduced key issues of in vivo treatment like drug penetrance and doxorubicin-induced bone toxicity. This work highlights the importance of a biomimetic matrix in 3D osteosarcoma models for both basic and translational research. STATEMENT OF SIGNIFICANCE: This study describes the generation of 3D osteosarcoma models termed "tumouroids", which are geometrically compartmentalised to reproduce the bone cancer mass and its environment. Utilising this novel model, specific parameters of osteosarcoma growth and invasion were investigated. Osteosarcoma cell lines proliferate at a slower rate, exhibit malignant metabolic reprogramming, and respond to drug intervention at lower concentrations of doxorubicin hydrochloride in matrix-complex compared to basic tumouroids. As such, this study provides evidence that the tumour microenvironment impacts osteosarcoma in many ways. The osteosarcoma tumouroid described herein may form the basis of a personalised-medicine strategy, which will allow the testing of drug effectiveness similar to that used for antibiotic selection for pathogenic bacteria.

New Insights about the Wnt/β-Catenin Signaling Pathway in Primary Bone Tumors and Their Microenvironment: A Promising Target to Develop Therapeutic Strategies?

Osteosarcoma and Ewing sarcoma are the most common malignant primary bone tumors mainly occurring in children, adolescents and young adults. Current standard therapy includes multidrug chemotherapy and/or radiation specifically for Ewing sarcoma, associated with tumor resection. However, patient survival has not evolved for the past decade and remains closely related to the response of tumor cells to chemotherapy, reaching around 75% at 5 years for patients with localized forms of osteosarcoma or Ewing sarcoma but less than 30% in metastatic diseases and patients resistant to initial chemotherapy. Despite Ewing sarcoma being characterized by specific EWSR1-ETS gene fusions resulting in oncogenic transcription factors, currently, no targeted therapy could be implemented. It seems even more difficult to develop a targeted therapeutic strategy in osteosarcoma which is characterized by high complexity and heterogeneity in genomic alterations. Nevertheless, the common point between these different bone tumors is their ability to deregulate bone homeostasis and remodeling and divert them to their benefit. Therefore, targeting different actors of the bone tumor microenvironment has been hypothesized to develop new therapeutic strategies. In this context, it is well known that the Wnt/β-catenin signaling pathway plays a key role in cancer development, including osteosarcoma and Ewing sarcoma as well as in bone remodeling. Moreover, recent studies highlight the implication of the Wnt/β-catenin pathway in angiogenesis and immuno-surveillance, two key mechanisms involved in metastatic dissemination. This review focuses on the role played by this signaling pathway in the development of primary bone tumors and the modulation of their specific microenvironment.

microRNA-758 inhibits the malignant phenotype of osteosarcoma cells by directly targeting HMGA1 and deactivating the Wnt/β-catenin pathway

microRNAs (miRNAs) are frequently aberrantly expressed in osteosarcoma (OS) and are implicated in its development. Dysregulation of miR-758 has been reported in various human malignancies. However, whether miR-758 is involved in the oncogenesis and progression of OS remains unclear. In this study, reverse transcription-quantitative polymerase chain reaction was performed to detect miR-758 expression in OS tissues and cell lines. A series of functional experiments were employed to explore the regulatory effects of miR-758 on the malignant behaviors of OS cells both in vitro and in vivo. The molecular mechanisms underlying the activity of miR-758 in OS cells were also investigated. miR-758 was significantly downregulated in OS tissues and cell lines, and a low miR-758 level was correlated with tumor size, clinical stage, and distant metastasis of patients with OS. OS patients with low miR-758 level exhibited poorer overall survival and worse disease-free survival rates compared to patients with high miR-758 level. In addition, functional assays revealed that miR-758 overexpression led to a significant decrease in OS cell growth and metastasis in vitro, whereas miR-758 inhibition had the opposite effect on OS cells. miR-758 reduced the tumorous growth of OS cells in vivo. Furthermore, high mobility group AT-hook 1 (HMGA1) was identified as a direct target of miR-758 in OS cells. HMGA1 was highly expressed in OS tissues, and its expression was inversely correlated with miR-758 expression. HMGA1 silencing exerted an effect similar to that induced by miR-758 upregulation in OS cells. Restored HMGA1 expression abolished the effects of miR-758 on the malignant phenotypes of OS cells. Moreover, miR-758 regulated the Wnt/β-catenin pathway in OS cells in vitro and in vivo. To the best of our knowledge, this is the first study to demonstrate that miR-758 may inhibit the aggressive behavior of OS cells in vitro and in vivo by directly targeting HMGA1 and regulating the Wnt/β-catenin pathway. These results will aid in elucidating the roles of miR-758 and suggest that the miR-758/HMGA1/Wnt/β-catenin pathway represents a potential therapeutic target in OS.

Expression of circ_001569 is upregulated in osteosarcoma and promotes cell proliferation and cisplatin resistance by activating the Wnt/β-catenin signaling pathway

Circular RNAs (circRNAs), a type of non-coding RNAs derived from back-splicing, have been reported to function as gene expression regulators involved in tumor development of multiple human tumors. However, the clinical significance and underlying molecular mechanisms of circ_001569 in osteosarcoma still be unknown. In the study, we found that circ_001569 expression was significantly overexpressed in osteosarcoma tissues compared with adjacent noncancerous bone tissues. Higher circ_001569 expression significantly correlated with distant metastasis and advanced tumor stage of osteosarcoma patients. Gain-function and loss-function assays showed that circ_001569 knockdown significantly inhibited osteosarcoma cell proliferation and cell colon formation capacities. Moreover, upregulation of circ_001569 significantly promoted osteosarcoma cell resistance to cisplatin by activating Wnt/β-catenin signaling pathway. Thus, these results indicated that circ_001569 represented a novel potentially therapeutic target of osteosarcoma.

Inhibition of WNT/β-catenin signaling under serum starvation and hypoxia induces adipocytic transdifferentiation in human leiomyoma cells

Fatty metamorphosis is an uncommon alteration in uterine leiomyoma (i.e., lipoleiomyoma), and the pathogenetic mechanisms underlying this phenomenon remain poorly understood. Because a conditional deletion of β-catenin, a major transducer of the canonical Wingless/integrated (WNT) pathway, in the developing mouse uterus can induce adipogenesis in the myometrium, it is hypothesized that inhibition of the WNT/β-catenin signaling may be also involved in the development of fat cells within uterine leiomyoma. In the current study, which was performed to address this point, intracytoplasmic lipid droplets were detectable in cultured human leiomyoma cells by treatment with a potent tankyrase inhibitor, XAV939, which antagonizes β-catenin, in a serum-starved culture medium without additional adipogenesis-inducing agents or supplements, and showed increasing accumulation in a time-dependent manner. In addition, the induction of fat cells was greatly enhanced under hypoxic conditions (i.e., 2.5% O₂)-recapitulating the local in vivo situation of uterine leiomyoma-in comparison to that under normoxic conditions (i.e., 21% O₂). The marker genes of differentiated fat cells such as ADIPOQ and PLIN were highly expressed in leiomyoma cells that were treated with XAV939 under hypoxia and serum starvation, whereas the immunohistochemical expression of desmin-a cytoskeletal protein representing smooth muscle differentiation-was downregulated, which appears in line with the switch in differentiation. The results of our study suggest that the inhibition of canonical WNT/β-catenin signaling under the stress due to hypoxia and serum starvation can initiate adipocytic transdifferentiation or metaplasia in human uterine leiomyoma cells, which is potentially related to the development of lipoleiomyoma.

Hypoxia-Induced Signaling Promotes Prostate Cancer Progression: Exosomes Role as Messenger of Hypoxic Response in Tumor Microenvironment

Prostate cancer (PCA) is the leading malignancy in men and the second leading cause of cancer-related deaths. Hypoxia (low O2 condition) is considered an early event in prostate carcinogenesis associated with an aggressive phenotype. In fact, clinically, hypoxia and hypoxia-related biomarkers are associated with treatment failure and disease progression. Hypoxia-inducible factor 1 (HIF-1) is the key factor that is activated under hypoxia, and mediates adaptation of cells to hypoxic conditions through regulating the expression of genes associated with angiogenesis, epithelial-to-mesenchymal transition (EMT), metastasis, survival, proliferation, metabolism, sternness, hormone-refractory progression, and therapeutic resistance. Besides HIF-1, several other signaling pathways including PI3K/Akt/mTOR, NADPH oxidase (NOX), Wnt/b-catenin, and Hedgehog are activated in cancer cells under hypoxic conditions, and also contribute in hypoxia-induced biological effects in HIF-1-dependent and -independent manners. Hypoxic cancer cells cause extensive changes in the tumor microenvironment both local and distant, and recent studies have provided ample evidence supporting the crucial role of nanosized vesicles "exosomes" in mediating hypoxia-induced tumor microenvironment remodeling. Exosomes' role has been reported in hypoxia-induced angiogenesis, sternness, activation of cancer-associated fibroblasts (CAFs), and EMT. Together, existing literature suggests that hypoxia plays a predominant role in PCA growth and progression, and PCA could be effectively prevented and treated via targeting hypoxia/hypoxia-related signaling pathways.

Wnt Signaling in Ewing Sarcoma, Osteosarcoma, and Malignant Peripheral Nerve Sheath Tumors

PURPOSE OF REVIEW

Wnt signaling plays a central role in development and homeostasis, and its dysregulation is a common event in many types of human cancer. Here we explore in detail the contributions of Wnt signaling to the initiation and maintenance of three types of saroma: Ewing sarcoma, osteosarcoma, and malignant peripheral nerve sheath tumors. This review provides an overview of the Wnt signaling pathway and explores in detail the current knowledge about its role in the initiation or maintenance of three tumor types: Ewing sarcoma, osteosarcoma, and malignant peripheral nerve sheath tumors.

RECENT FINDINGS

Recent work has assessed the role(s) of Wnt signaling within these cell types. This review provides an overview of the mechanistic insights that have been gained from a number of recent studies to set the foundation for potential therapeutic applications. Wnt signaling has emerged as a potentially critical pathway in maintaining the growth of these types of tumors. Given the fact that many new inhibitors of the pathway have recently or will soon enter Phase 1 clinical trials, it is likely that assessment of their activity in these tumor types will occur in human patients.

Apoptosis induction of poly-S-nitrosated human serum albumin in resistant solid tumor under hypoxia can be restored by phosphodiesterase 5 inhibition

Poly-S-nitrosated human serum albumin (Poly-SNO-HSA) delivered and accumulated nitric oxide (NO) in tumors and induces apoptosis. Tumor hypoxia is strongly associated with malignant progression and tumor resistance to therapy. In this study, we examined the cytotoxic effect of Poly-SNO-HSA under hypoxia on the murine colon 26 adenocarcinoma (C26) cells in vitro and in vivo. Under hypoxia, at about 4 times LD₅₀ dose of Poly-SNO-HSA in vitro, the reactive oxygen species production was hindered but apoptotic cells were induced via cGMP pathway as the effect was suppressed by a soluble guanylate cyclase inhibitor, NS2028. The apoptosis induction effect of low dose Poly-SNO-HSA on C26 cells in vitro under hypoxia can be restored by a phosphodiesterase 5 (PDE5) inhibitor, vardenafil. In C26-bearing mice, Poly-SNO-HSA/vardenafil combination treatment significantly suppressed the tumor volume compared with Poly-SNO-HSA or vardenafil treatment alone. Furthermore, the core tumor tissues showed increased expression of caspase-3 than the non-core tissue. The expression of caspase-3 appeared to overlap with the hypoxic zone of tumor tissues. Similar results were also obtained when the experiments were repeated using Epimedium extract, a natural herbal supplement with PDE5 inhibition activity. In conclusion, Poly-SNO-HSA/PDE5 inhibitors combination therapy is a promising approach for enhancing the anticancer therapeutic effects of Poly-SNO-HSA against not only anti-cancer drug resistance but also hypoxic stress related solid tumor resistance.

Wnt agonist stimulates liver regeneration after small-for-size liver transplantation in rats

AIM

Liver regeneration is inhibited in small-for-size grafts, which plays a role in the failure of partial liver grafts after transplantation. The Wnt/β-catenin signaling pathway plays a critical role in liver development, regeneration and homeostasis. In this study, we investigated whether pharmacological activation of Wnt signaling improves liver regeneration after small-for-size liver transplantation.

METHODS

The livers of male Sprague-Dawley rats were reduced to approximately 50% and 30% of their original sizes and transplanted. A Wnt agonist (2-amino-4-[3,4-[methylenedioxy]benzylamino]-6-[3-methoxyphenyl] pyrimidine], 5 mg/kg bodyweight) or an equal volume of vehicle was administrated i.p. into the donor 1 h before the transplantation. Tissue and blood samples were collected at various times after transplantation, and a survival study was performed.

RESULTS

Hepatic expression of active β-catenin and its downstream target gene Axin2 were decreased in 30% of liver grafts after transplantation while the Wnt agonist increased their expression similar to the 50% liver grafts. The Wnt agonist reversed inhibition of cyclin D1 expression and adenosine triphosphate production in the 30% liver grafts compared with the 50% grafts. The Wnt agonist also attenuated hepatocellular injury and increased the hepatocyte proliferation response, liver regeneration rate and survival after transplantation of the 30% liver graft.

CONCLUSION

Activation of Wnt/β-catenin signaling in liver grafts by pharmacological pretreatment can accelerate regeneration in a partial liver transplant model.

miR-146b-5p promotes invasion and metastasis contributing to chemoresistance in osteosarcoma by targeting zinc and ring finger 3

Osteosarcoma is the most common human primary malignant bone tumor and recurrences are common due to the development of chemoresistance. However, the underlying molecular mechanism for chemoresistance remains unclear. Recent studies demonstrated that miR-146b-5p, an important regulator in tumorigenesis, was involved in chemoresistance in thyroid cancer, lymphoma. Thus, to confirm the role of miR‑146b-5p in osteosarcoma, the study was divided into three steps: first, miR-146b-5p in paired samples were assessed using a quantitative real-time PCR (qRT-PCR) assay from osteosarcoma patients. Second, to confirm the role of miR-146b-5p, we applied lentivirus system to overexpression and knockdown of miR-146b-5p, respectively, in MG-63 osteosarcoma cell line. Third, luciferase assays were performed to determine whether Wnt/β-catenin pathway participated in the role of miR-146b-5p on chemoresistance. As a result, miR-146b-5p was highly expressed in human osteosarcoma tissues and an elevated expression of miR-146b-5p was observed in human osteosarcoma tissues after chemotherapy. Furthermore, it was shown that miR-146b-5p overexpression promoted migration and invasiveness. miR-146b-5p overexpression also increased resistance to chemotherapy. Moreover, knockdown of miR-146b-5p substantially inhibited migration and invasion of osteosarcoma cells as well as rendered them significantly more sensitive to chemotherapy. Results of western blot assay indicated that miR-146b-5p increased MMP-16 protein expression and showed a decrease of ZNRF3 protein. Whereas, IWR-1-endo, an inhibitor of Wnt/β-catenin, suppressed the decrease in apoptosis of osteosarcoma cells caused by miR-146b-5p overexpression. These results indicated that miR-146b-5p promoted proliferation, migration and invasiveness. It also increased resistance to chemotherapy through the regulation of ZNRF3, and suggested novel potential therapeutic targets for the treatment of osteosarcoma.

Bone microenvironment signals in osteosarcoma development

The bone is a complex connective tissue composed of many different cell types such as osteoblasts, osteoclasts, chondrocytes, mesenchymal stem/progenitor cells, hematopoietic cells and endothelial cells, among others. The interaction between them is finely balanced through the processes of bone formation and bone remodeling, which regulates the production and biological activity of many soluble factors and extracellular matrix components needed to maintain the bone homeostasis in terms of cell proliferation, differentiation and apoptosis. Osteosarcoma (OS) emerges in this complex environment as a result of poorly defined oncogenic events arising in osteogenic lineage precursors. Increasing evidence supports that similar to normal development, the bone microenvironment (BME) underlies OS initiation and progression. Here, we recapitulate the physiological processes that regulate bone homeostasis and review the current knowledge about how OS cells and BME communicate and interact, describing how these interactions affect OS cell growth, metastasis, cancer stem cell fate and therapy outcome.

Aplasia Ras homologue member Ⅰ overexpression inhibits tumor growth and induces apoptosis through inhibition of PI3K/Akt survival pathways in human osteosarcoma MG-63 cells in culture

Aplasia Ras homologue member Ⅰ (ARHI), an imprinted tumor-suppressor gene, is downregulated in various types of cancer. However, the expression, function and specific mechanisms of ARHI in human osteosarcoma (OS) cells remain unclear. The aim of the present study was to assess the effect of ARHI on OS cell proliferation and apoptosis and its associated mechanism. In the study, ARHI mRNA and protein levels were markedly downregulated in OS cells compared with the human osteoblast precursor cell line hFOB1.19. By generating stable transfectants, ARHI was overexpressed in OS cells that had low levels of ARHI. Overexpression of ARHI inhibited cell viability and proliferation and induced apoptosis. However, caspase‑3 activity was not changed by ARHI overexpression. In addition, phosphorylated Akt protein expression decreased in the ARHI overexpression group compared to that in the control vector group. The knockdown of ARHI also resulted in the promotion of cell proliferation and the attenuation of apoptosis in MG‑63 cells. Additionally, ARHI silencing increased the level of p‑Akt. The present results indicate that ARHI inhibits OS cell proliferation and may have a key role in the development of OS.

Anoikis-resistant subpopulations of human osteosarcoma display significant chemoresistance and are sensitive to targeted epigenetic therapies predicted by expression profiling

Background

Osteosarcoma (OS) is the most common type of solid bone cancer, with latent metastasis being a typical mode of disease progression and a major contributor to poor prognosis. For this to occur, cells must resist anoikis and be able to recapitulate tumorigenesis in a foreign microenvironment. Finding novel approaches to treat osteosarcoma and target those cell subpopulations that possess the ability to resist anoikis and contribute to metastatic disease is imperative. Here we investigate anchorage-independent (AI) cell growth as a model to better characterize anoikis resistance in human osteosarcoma while using an expression profiling approach to identify and test targetable signaling pathways.

Methods

Established human OS cell lines and patient-derived human OS cell isolates were subjected to growth in either adherent or AI conditions using Ultra-Low Attachment plates in identical media conditions. Growth rate was assessed using cell doubling times and chemoresistance was assessed by determining cell viability in response to a serial dilution of either doxorubicin or cisplatin. Gene expression differences were examined using quantitative reverse-transcription PCR and microarray with principal component and pathway analysis. In-vivo OS xenografts were generated by either subcutaneous or intratibial injection of adherent or AI human OS cells into athymic nude mice. Statistical significance was determined using student’s t-tests with significance set at α = 0.05.

Results

We show that AI growth results in a global gene expression profile change accompanied by significant chemoresistance (up to 75 fold, p < 0.05). AI cells demonstrate alteration of key mediators of mesenchymal differentiation (β-catenin, Runx2), stemness (Sox2), proliferation (c-myc, Akt), and epigenetic regulation (HDAC class 1). AI cells were equally tumorigenic as their adherent counterparts, but showed a significantly decreased rate of growth in-vitro and in-vivo (p < 0.05). Treatment with the pan-histone deacetylase inhibitor vorinostat and the DNA methyltransferase inhibitor 5-azacytidine mitigated AI growth, while 5-azacytidine sensitized anoikis-resistant cells to doxorubicin (p < 0.05).

Conclusions

These data demonstrate remarkable plasticity in anoikis-resistant human osteosarcoma subpopulations accompanied by a rapid development of chemoresistance and altered growth rates mirroring the early stages of latent metastasis. Targeting epigenetic regulation of this process may be a viable therapeutic strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0466-4) contains supplementary material, which is available to authorized users.

WITHDRAWN: Hypoxia-induced STAT3 contributes to chemoresistance and epithelial-mesenchymal transition in prostate cancer cells

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Hypoxia promotes 786-O cells invasiveness and resistance to sorafenib via HIF-2α/COX-2

Accumulating evidences indicated that hypoxia-induced factors and COX-2 play a important role in tumorigenesis in various human cancer. Yet, the relationship between HIFs and COX-2 in human renal cancer remains unclear. The present study was to examine the role of HIFs and COX-2 in the invasiveness and the resistance to target agent in renal cancer cell line (786-O). In 786-O cells, hypoxia induced the increase in the protein expression of HIF1 and HIF2. We also demonstrate that hypoxia up-regulated the protein expression of COX-2 and Snail, but down-regulation of E-cadherin expression in 786-O cells promoted the invasiveness of 786-O cells and enhanced the resistance of 786-O cells to sorafenib. siRNA target to HIF1α, HIF2α and NS398, a selective inhibitor of COX-2, were used in this study. Only siRNA-HIF2α significantly suppressed the protein expression of HIF2 and COX-2, then decreased the invasive ability and resistance of 786-O cells to sorafenib under hypoxia. NS398 attenuated the increase in invasive cells number and the IC50 value of sorafenib induced by hypoxia. In conclusion, our results demonstrated that hypoxia promoted the invasiveness and resistance of 786-O cells to sorafenib via HIF2 and COX-2 and induced the activation of Snail/E-cadherin, suggesting that a signalling mechanism involving HIF2/COX2 modulates invasiveness and resistance to sorafenib in 786-O cells under hypoxia.