Molecular Pathogenesis Of Osteosarcoma Research Articles

Clinicopathological significance of SOX9 and β-catenin expression in pre-neoadjuvant chemotherapy cases of osteosarcoma: molecular and immunohistochemical study

ABSTRACT The molecular pathogenesis of osteosarcoma (OS), the most frequent primary malignant bone tumor of all age groups, is still obscure. Since multidrug chemotherapeutic regimens were introduced in the 1970s, survival rates have been stationary. The Wnt-β-catenin signaling cascade and SOX9 have a significant contribution to skeletal growth, development, and tumorigenesis. In the present work, an attempt was made to examine the role and clinicopathological significance of β-catenin and SOX9 in 46 cases of pre-neoadjuvant chemotherapy OS tissues compared to 10 cases of non-neoplastic bone. The mRNA levels of both markers were assessed by qRT-PCR, and protein levels of β-catenin were analyzed by immunohistochemistry. The results were correlated with different clinicopathological parameters. SOX9 mRNA levels were significantly elevated in OS compared to non-neoplastic bone, and higher levels were significantly associated with the occurrence of fluid-fluid levels (indicating blood-containing cystic spaces) and osteolytic radiological pattern. Although β-catenin mRNA and protein levels were higher in OS compared to non-neoplastic bone, only the protein levels reached statistical significance. Higher β-catenin mRNA levels were significantly associated with tumor size, while higher protein levels were significantly associated with the histologic subtype, mitotic count, and radiological pattern. No significant association was noted with any of the other evaluated parameters. OS showing higher SOX9 mRNA expression and lower β-catenin mRNA and protein expression exhibited longer estimated overall survival times approaching statistical significance. To conclude, while high expression of β-catenin and SOX9 suggests their possible involvement in OS development, their prognostic role may need further research.

Development and characterization of the novel human osteosarcoma cell line COS-33 with sustained activation of the mTOR pathway

Outcomes have not improved for metastatic osteosarcoma for several decades. In part, this failure to develop better therapies stems from a lack of understanding of osteosarcoma biology, given the rarity of the disease and the high genetic heterogeneity at the time of diagnosis. We report here the successful establishment of a new human osteosarcoma cell line, COS-33, from a patient-derived xenograft and demonstrate retention of the biological features of the original tumor. We found high mTOR signaling activity in the cultured cells, which were sensitive to a small molecule inhibitor, rapamycin, a suppressor of the mTOR pathway. Suppressed mTOR signaling after treatment with rapamycin was confirmed by decreased phosphorylation of the S6 ribosomal protein. Increasing concentrations of rapamycin progressively inhibited cell proliferation in vitro. We observed significant inhibitory effects of the drug on cell migration, invasion, and colony formation in the cultured cells. Furthermore, we found that only a strong osteogenic inducer, bone morphogenetic protein-2, promoted the cells to differentiate into mature mineralizing osteoblasts, indicating that the COS-33 cell line may have impaired osteoblast differentiation. Grafted COS-33 cells exhibited features typical of osteosarcoma, such as production of osteoid and tumorigenicity in vivo. In addition, we revealed that the COS-33 cell line retained a complex karyotype, a homozygous deletion of the TP53 gene, and typical histological features from its original tumor. Our novel cellular model may provide a valuable platform for studying the etiology and molecular pathogenesis of osteosarcoma as well as for testing novel drugs for future genome-informed targeted therapy.

ARID3A-mediated modulation of TP73 and TP73-AS1 in osteosarcoma cells

Osteosarcoma is the most common primary malignancy arising from bone. Increasing mass of indications suggest that long non-coding RNAs (lncRNAs) play crucial roles in the development of progressions of human cancers including osteosarcoma. Although several lncRNAs have shown to be involved in the molecular pathogenesis of osteosarcoma, identification of novel lncRNAs involved in the osteosarcoma pathobiology remained muchly elusive. Besides, ARID3A is a member of ARID family of DNA binding proteins. ARID3A was also implicated in osteosarcoma pathogenesis. Accordingly, in the present study, we mechanistically investigated the effect of ARID3A on the expression of TP73 and TP73-AS1 in osteosarcoma cells and to determine the relationship between them. For the overexpression of ARID3A in U2-OS cells, pER_xpress_ARID3A expression vector and for the silencing of ARID3A, ARID3A-spesific siRNA was used. Expression levels of ARID3A, TP73 and TP73-AS1 genes were determined by qPCR method. As a result, expression levels of TP73-AS1 were well-correlated with the ARID3A expression levels whereas TP73 expression levels were not well-correlated with ARID3A. In conclusion, our results indicate that ARID3A might be involved in the regulation of TP73-AS1 in osteosarcoma. To our knowledge, this is the first study revealing the role of ARID3A in the regulation of TP73 and TP73-AS1 genes.

Abstract 82: Transforming of human osteoblasts with the combination of hTERT (T), SV40Tag (S) and c-Myc: Changes in phenotype and tumorigenesis capability

Abstract The etiology of osteosarcoma (OS), the most common primary malignant bone cancer in pediatric patients, still remains unknown. It is not clear where tat which point he osteosarcoma is originated from the osteogenic lineagein the osteogenic osteosarcoma arises., some consider Potential candidates in the literature include the human mesenchymal cells (hMSC) as the cell of origin in OS, whereas others believe theand osteoblast (OB) to be the most likely cell of origin. To understand the origin and molecular pathogenesis of osteosarcoma, we have transformed hMSCs and OBs differentiated from the same MSC with oncogenes hTERT (T), SV40Tag (S) and H-RAS (R) in series to check evaluate for spindle cell tumor formation in mice. Transformed MSC did not form osteoid, whereas OB-TSR tumor showed only scant production of osteoid, suggesting MSC may not be the origin of OS and the hTERT, SV40Tag and h-Ras may not be sufficient for osteoblast to form OS. C-Myc is one of the genes that play a major role in oncogenic transformation of normal cells. It has been shown that c-Myc is overexpressed in OS cells and more than 10% OS patients carry c-Myc amplification mutations. We further decide to look intoThis served as the basis to examine the role of c-Myc in OS formation in the background of cells transformed by hTERT and SV40. OB transformed with hTERT and SV40Tag cells were further transfected with a retrovirus containing human c-Myc to obtain stable cell lines. Quantitative PCR and western blots assays detected both gene and protein expression patterns of c-Myc, respectively, in the transformed cell lines. Transformed cell lines were analyzed for proliferation, invasion, migration, and spheroid formation to determine the tumorigenic capacity capability. TThe tumorigenesis capability is found to be correlated with the level of c-Myc expression level based onby RT-PCR data. Furthermore, we used RNA-seq to analyze gene expression profiles of the transformed cell lines, compared with those forin comparison to primary OS cell lines and patient derived xenografts (PDXs). In -vivo tumorigenic assays, histological examination for osteoid production and chromosome analysis are still under way. Our study using an osteosarcoma model with transformed human cells may provide new insights on the cell origin of OS. Citation Format: Zhongting Zhang, Yifei Wang, Wendong Zhang, Michael Roth, Jonathan Benjamin Gill, Zhaohui Xu, Xiangjun Tian, Jing Wang, Richard Gorlick. Transforming of human osteoblasts with the combination of hTERT (T), SV40Tag (S) and c-Myc: Changes in phenotype and tumorigenesis capability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 82.

Hypoxia promotes osteosarcoma cell proliferation and migration through enhancing platelet-derived growth factor-BB/platelet-derived growth factor receptor-β axis

Osteosarcoma is a primary malignant bone tumor, characterized by high therapeutic resistance and poor outcomes, due to unclear pathological mechanisms. It has been shown recently that the platelet-derived growth factor (PDGF)/platelet-derived growth factor receptor (PDGFR) pathway is closely associated with the pathogenesis of osteosarcoma. Hypoxia is a critical hallmark of tumor microenvironment that promotes the malignant phenotype in many solid tumors and a fundamental impediment to effective tumor therapy. In this study, we confirmed that hypoxia is an important feature of osteosarcoma, validated by the positive immunohistochemistry staining of hypoxia marker hypoxia-inducible factor-1α (HIF-1α) and carbonic anhydrase IX (CAIX) in osteosarcoma tissue samples. More importantly, we discovered that hypoxia could transcriptionally upregulate the expression of both PDGF-BB and PDGFR-β in osteosarcoma cells in vitro. Likewise, we also established that hypoxia-induced PDGF-BB is strongly related to the enhanced cell proliferation and migration, by activating AKT, ERK1/2, and STAT3 signaling pathways. Notably, when using an antibody to block the autocrine of PDGF-BB, cell proliferation and migration were partially aborted in hypoxia. Collectively, we demonstrated that the hypoxia-activated PDGF-BB/PDGFR-β axis plays essential roles in osteosarcoma progression. These findings may shed light on the molecular pathogenesis of osteosarcoma, and provide a novel strategy for osteosarcoma treatment by combinational targeting hypoxia and PDGF-BB/PDGFR signaling.

Overexpression of microRNA-495 suppresses the proliferation and invasion and induces the apoptosis of osteosarcoma cells by targeting high-mobility group nucleosome-binding domain 5.

It has been suggested that microRNAs (miRNAs) act as critical regulators in tumorigenesis. MicroRNA-495 (miR-495) has been suggested as a cancer-associated miRNA in various types of cancers; however, the role of miR-495 in osteosarcoma is unknown. The aim of the present study was to determine whether miR-495 is involved in osteosarcoma, and to investigate the potential molecular mechanism of its involvement. We found that miR-495 was significantly downregulated in osteosarcoma tissues and cell lines, as detected by real-time quantitative polymerase chain reaction (RT-qPCR). Overexpression of miR-495 inhibited osteosarcoma cell proliferation in 3-(4,5-dimethylthiazol-2-yl)- ,5-diphenyltetrazolium bromide, colony formation and cell cycle assays. Overexpression of miR-495 induced osteosarcoma cell apoptosis. Moreover, miR-495 overexpression also inhibited osteosarcoma cell invasion. Bioinformatics and luciferase reporter assays demonstrated that miR-495 targets the 3'-untranslated region of high-mobility group nucleosome‑binding domain5 (HMGN5), a potential oncogene in various types of cancers. Overexpression of miR-495 inhibited the expression of HMGN5, cyclinB1, Bcl-2 and matrix metalloproteinase9. In addition, restoration of HMGN5 protein expression abrogated the miR-495-induced effects. Taken together, the present study indicated that miR-495 suppresses the proliferation and invasion and induces the apoptosis of osteosarcoma cells by targeting HMGN5, providing a novel insight into the molecular pathogenesis of osteosarcoma and suggesting a potential molecular target for the development of an miRNA-targeted therapeutic strategy for osteosarcoma.

NKD2, a negative regulator of Wnt signaling, suppresses tumor growth and metastasis in osteosarcoma.

Osteosarcoma (OS) is the most frequent pediatric malignant bone tumor that has a high propensity for metastases. Through osteoblast-specific alteration of p53 status, we developed a genetically engineered mouse model of localized and metastatic OS to gain an understanding into the molecular pathogenesis of OS. Microarray analysis of both localized tumors and metastatic tumors identified the downregulation of the naked cuticle homolog 2 (NKD2) gene, a negative regulator of Wnt signaling. Overexpression of NKD2 in metastatic human and mouse OS cells significantly decreases cell proliferation, migration and invasion ability in vitro and drastically diminishes OS tumor growth and metastasis in vivo, whereas downregulation enhances migratory and invasive potential. Evaluation of NKD2-overexpressing tumors revealed upregulation of tumor-suppressor genes and downregulation of molecules involved in blood vessel formation and cell migration. Furthermore, assessment of primary human OS revealed downregulation of NKD2 in metastatic and recurrent OS. Finally, we provide biological evidence that use of small-molecule inhibitors targeting the Wnt pathway can have therapeutic efficacy in decreasing metastatic properties in OS. Our studies provide compelling evidence that downregulation of NKD2 expression and alterations in associated regulated pathways have a significant role in driving OS tumor growth and metastasis.

Targeting BMP9-Promoted Human Osteosarcoma Growth by Inactivation of Notch Signaling

Osteosarcoma (OS) is the most common primary malignancy of bone and is usually associated with poor prognosis due to its high incidence of metastasis and chemoresistance. Molecular pathogenesis of OS is poorly understood. We previously showed that OS cells are refractory to BMP9-induced osteogenesis and respond favorably to proliferation and tumor growth. Here we investigate if Notch signaling mediates the BMP9-promoted cell proliferation and tumor growth of human osteosarcoma (OS). We find that the expression of Notch1, Notch2, Notch3, DLL1, JAG1 and JAG2 is readily detected in most of the tested OS cell lines. BMP9-promoted OS cell proliferation, migration, and cell cycle S/G2 progression are effectively inhibited by a dominant-negative mutant of Notch1 (dnNotch1) or the γ-secretase inhibitor Compound E (ComE). Furthermore, BMP9-promoted tumor growth and osteolytic lesions in vivo are significantly inhibited by dnNotch1. BMP9 up-regulates the expression of Notch1, Notch3, DLL1, and JAG1 in OS cells. Accordingly, BMP9 stimulation induces a nuclear accumulation of NICD, which is blocked by ComE. Our results demonstrate that BMP9-promoted OS proliferation and tumor growth is at least in part mediated by Notch signaling, suggesting that osteogenic BMPs may function as upstream regulators of Notch signaling in OS tumorigenesis. Thus, pharmacologic intervention of Notch signaling may be explored as a new therapeutic strategy for human OS tumors.

At-risk populations for osteosarcoma: the syndromes and beyond.

Osteosarcoma is the most common primary malignancy of bone. Most cases are sporadic without a known genetic or environmental cause. Heritable genetic predisposition syndromes are associated with a small percentage of osteosarcomas. Study of these rare disorders has provided insight into the molecular pathogenesis of osteosarcoma. Screening of at-risk families and surveillance of affected individuals for these syndromes may permit earlier diagnosis and more effective treatment of osteosarcoma in these populations. This paper reviews the genetic and clinical features of the known osteosarcoma predisposition syndromes.

Highly frequent allelic loss of chromosome 6q16-23 in osteosarcoma: Involvement of cyclin C in osteosarcoma

The molecular pathogenesis of osteosarcoma is very complicated and associated with chaotic abnormalities on many chromosomal arms. We analyzed 12 cases of osteosarcomas with comparative genomic hybridization (CGH) to identify chromosomal imbalances, and detected highly frequent chromosomal alterations in chromosome 6q, 8p, 10p and 10q. To define the narrow rearranged region on chromosome 6 with higher resolution, loss of heterozygosity (LOH) analysis was performed with 21 microsatellite markers. Out of 31 cases, 23 cases (74%) showed allelic loss at least with one marker on chromosome 6q. We identified two distinct commonly deleted regions on chromosome 6 using markers D6S1565 located at 6q16 and 6q23MS1 at 6q23. The expression analysis of genes located at the deleted region was performed, and the decreased mRNA expression of the CCNC gene, one of the regulators of cell cycle, was detected. Growth of osteosarcoma cell line was significantly suppressed after the CCNC cDNA transfection. Fine mapping of the deleted region containing a possible tumor suppressor gene and the transfection assay suggest that the CCNC is a candidate tumor suppressor gene.