Transcriptome Analysis Identifies Novel Prognostic Genes in Osteosarcoma

Systematic analysis of RNA-binding proteins identifies targetable therapeutic vulnerabilities in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor with a strong tendency to metastasize, limiting the prognosis of affected patients. Genomic, epigenomic and transcriptomic analyses have demonstrated the exquisite molecular complexity of this tumor, but have not sufficiently defined the underlying mechanisms or identified promising therapeutic targets. To systematically explore RNA-protein interactions relevant to OS, we define the RNA interactomes together with the full proteome and the transcriptome of cells from five malignant bone tumors (four osteosarcomata and one malignant giant cell tumor of the bone) and from normal mesenchymal stem cells and osteoblasts. These analyses uncover both systematic changes of the RNA-binding activities of defined RNA-binding proteins common to all osteosarcomata and individual alterations that are observed in only a subset of tumors. Functional analyses reveal a particular vulnerability of these tumors to translation inhibition and a positive feedback loop involving the RBP IGF2BP3 and the transcription factor Myc which affects cellular translation and OS cell viability. Our results thus provide insight into potentially clinically relevant RNA-binding protein-dependent mechanisms of osteosarcoma.

The role of CD180 in hematological malignancies and inflammatory disorders

Toll-like receptors play a significant role in the innate immune system and are also involved in the pathophysiology of many different diseases. Over the past 35 years, there have been a growing number of publications exploring the role of the orphan toll-like receptor, CD180. We therefore set out to provide a narrative review of the current evidence surrounding CD180 in both health and disease. We first explore the evidence surrounding the role of CD180 in physiology including its expression, function and signaling in antigen presenting cells (APCs) (dendritic cells, monocytes, and B cells). We particularly focus on the role of CD180 as a modulator of other TLRs including TLR2, TLR4, and TLR9. We then discuss the role of CD180 in inflammatory and autoimmune diseases, as well as in hematological malignancies of B cell origin, including chronic lymphocytic leukemia (CLL). Based on this evidence we produce a current model for CD180 in disease and explore the potential role for CD180 as both a prognostic biomarker and therapeutic target. Throughout, we highlight specific areas of research which should be addressed to further the understanding of CD180 biology and the translational potential of research into CD180 in various diseases.

The mitotic regulator polo-like kinase 1 as a potential therapeutic target for c-Myc-overexpressing canine osteosarcomas

Osteosarcoma is the most common primary malignant bone tumour in dogs, characterized by a locally aggressive and highly metastatic behaviour. Despite the current standards of care, most dogs succumb to the disease, indicating the need for novel treatment strategies. Polo-like kinase 1 (PLK1) is dysregulated in a variety of human cancer types, including osteosarcoma, and induces c-Myc accumulation. The crosstalk between the two molecules coordinates cell proliferation, differentiation, self-renewal and apoptosis. Therefore, PLK1 has recently emerged as a potential therapeutic target, mainly in tumours overexpressing c-Myc. BI 2536 is a selective PLK1 inhibitor promoting mitotic arrest and apoptosis in a variety of cancer cells. This research aimed at evaluating PLK1 and c-Myc protein expression in 53 appendicular canine osteosarcoma (cOSA) samples and the in vitro effects of BI 2536 on a c-Myc and PLK1-overexpressing cOSA cell line (D17). PLK1 and c-Myc expression in cOSA samples showed no correlation with clinicopathological data. However, c-Myc overexpression was associated with a significantly reduced overall survival (p = .003). Western Blot and RT-qPCR assays revealed that D17 expressed high protein and transcript levels of both PLK1 and MYC. When treated with BI 2536 (range 2.5-15 nM) for 24 h, D17 showed a substantial decrease in cell growth, inducing apoptosis and G₂ /M cell cycle arrest. Interestingly, under BI 2536 treatment, D17 showed decreased c-Myc protein levels. Consistent with human OSA, these preliminary data outline the prognostic value of c-Myc expression in cOSA and highlight the potential role of PLK1 as an antiproliferative therapeutic target for tumours overexpressing c-Myc.

PROSER2 is a poor prognostic biomarker for patients with osteosarcoma and promotes proliferation, migration and invasion of osteosarcoma cells

Proline- and serine-rich 2 (PROSER2) is encoded by the 47th open reading frame on human chromosome 10. Bioinformatic analysis has shown PROSER2 was significantly correlated with prognostic outcome of osteosarcoma patients. Its role in the progression and metastasis of human osteosarcoma has not been elucidated until now. Bioinformatics analysis was performed on 101 patients with osteosarcoma from The Cancer Genome Atlas database. High levels of PROSER2 were associated with a poor prognosis in patients with osteosarcoma. PROSER2 expression was significantly upregulated in clinical specimens from patients with osteosarcoma and osteosarcoma cell lines. MTT assay was performed to test the cell viability and Transwell assay was used to test the migration and invasion of MG63 cells. PROSER2 knockdown inhibited the viability, migration and invasion of MG63 cells. Gene Set Enrichment Analysis and Gene Ontology/Kyoto Encyclopedia of Genes and Genomes analysis showed that the differentially expressed genes were primarily involved in 'calcium signaling pathway' and 'Wnt signaling' in patients with osteosarcoma and high PROSER2 expression. Western blotting analysis revealed that PROSER2 regulated migration and invasion of osteosarcoma via the Wnt/nuclear factor of activated T-cells (NFAT)c1 signaling pathway. In conclusion, PROSER2 promoted the proliferation, migration and invasion of osteosarcoma cells via the Wnt/Ca²⁺/NFATc1 signaling pathway by increasing nuclear localization of NFATc1.

Identification of a 3-gene signature based on differentially expressed invasion genes related to cancer molecular subtypes to predict the prognosis of osteosarcoma patients

Invasion is a critical pathway leading to tumor metastasis. This study constructed an invasion-related polygenic signature to predict osteosarcoma prognosis. We initially determined two molecular subtypes of osteosarcoma, Cluster1 (C1) and Cluster2 (C2).. A 3 invasive-gene signature was established by univariate Cox analysis and least absolute shrinkage and selection operator (LASSO) Cox regression analysis of the differentially expressed genes (DEGs) between the two subtypes, and was validated in internal and two external data sets (GSE21257 and GSE39058). Patients were divided into high- and low-risk groups by their signature, and the prognosis of osteosarcoma patients in the high-risk group was poor. Based on the time-independent receiver operating characteristic (ROC) curve, the area under the curve (AUC) for 1-year and 2-year OS were higher than 0.75 in internal and external cohorts. This signature also showed a high accuracy and independence in predicting osteosarcoma prognosis and a higher AUC in predicting 1-year osteosarcoma survival than other four existing models. In a word, a 3 invasive gene-based signature was developed, showing a high performance in predicting osteosarcoma prognosis. This signature could facilitate clinical prognostic analysis of osteosarcoma.

The Potential Role of RP105 in Regulation of Inflammation and Osteoclastogenesis During Inflammatory Diseases

Inflammatory diseases have a negative impact on bone homeostasis via exacerbated local and systemic inflammation. Bone resorbing osteoclasts are mainly derived from hematopoietic precursors and bone marrow monocytes. Induced osteoclastogenesis during inflammation, autoimmunity, metabolic diseases, and cancers is associated with bone loss and osteoporosis. Proinflammatory cytokines, pathogen-associated molecular patterns, or endogenous pathogenic factors induce osteoclastogenic differentiation by binding to the Toll-like receptor (TLR) family expressed on surface of osteoclast precursors. As a non-canonical member of the TLRs, radioprotective 105 kDa (RP105 or CD180) and its ligand, myeloid differentiation protein 1 (MD1), are involved in several bone metabolic disorders. Reports from literature had demonstrated RP105 as an important activator of B cells, bone marrow monocytes, and macrophages, which regulates inflammatory cytokines release from immune cells. Reports from literature had shown the association between RP105 and other TLRs, and the downstream signaling mechanisms of RP105 with different “signaling-competent” partners in immune cells during different disease conditions. This review is focused to summarize: (1) the role of RP105 on immune cells’ function and inflammation regulation (2) the potential regulatory roles of RP105 in different disease-mediated osteoclast activation and the underlying mechanisms, and (3) the different “signaling-competent” partners of RP105 that regulates osteoclastogenesis.