TIKI2 suppresses growth of osteosarcoma by targeting Wnt/β-catenin pathway

Targeting signaling pathways in osteosarcoma: Mechanisms and clinical studies

Osteosarcoma (OS) is a highly prevalent bone malignancy among adolescents, accounting for 40% of all primary malignant bone tumors. Neoadjuvant chemotherapy combined with limb-preserving surgery has effectively reduced patient disability and mortality, but pulmonary metastases and OS cells' resistance to chemotherapeutic agents are pressing challenges in the clinical management of OS. There has been an urgent need to identify new biomarkers for OS to develop specific targeted therapies. Recently, the continued advancements in genomic analysis have contributed to the identification of clinically significant molecular biomarkers for diagnosing OS, acting as therapeutic targets, and predicting prognosis. Additionally, the contemporary molecular classifications have revealed that the signaling pathways, including Wnt/β-catenin, PI3K/AKT/mTOR, JAK/STAT3, Hippo, Notch, PD-1/PD-L1, MAPK, and NF-κB, have an integral role in OS onset, progression, metastasis, and treatment response. These molecular classifications and biological markers have created new avenues for more accurate OS diagnosis and relevant treatment. We herein present a review of the recent findings for the modulatory role of signaling pathways as possible biological markers and treatment targets for OS. This review also discusses current OS therapeutic approaches, including signaling pathway-based therapies developed over the past decade. Additionally, the review covers the signaling targets involved in the curative effects of traditional Chinese medicines in the context of expression regulation of relevant genes and proteins through the signaling pathways to inhibit OS cell growth. These findings are expected to provide directions for integrating genomic, molecular, and clinical profiles to enhance OS diagnosis and treatment.

Prognostic Significance of β-Catenin Expression in Osteosarcoma: A Meta-Analysis

Background: β-catenin plays a crucial role in the progression of osteosarcoma. However, the clinical significance of β-catenin over-expression in osteosarcoma still remains unclear. Thus, we performed a meta-analysis of studies that evaluated the impact of β-catenin on metastasis and overall survival (OS) in osteosarcoma.

Methods: We searched PubMed, The Cochrane Library, Embase, Springer, Science Direct, OVID, Weipu, Wanfang and China National Knowledge Internet (CNKI) databases from their start year up to Aug.2019. Individual hazard ratios (HRs) and 95% confidence intervals (CIs) were extracted and pooled HRs with 95% CIs or odd ratio (OR) were used to evaluate the relationships between β-catenin over-expression and metastasis and overall survival in osteosarcoma.

Results: Eight related studies involving 521 patients were qualified for this meta-analysis. Results showed that over-expression of β-catenin was significantly correlated with metastasis (OR = 3.31, 95% CI = 2.08–5.24, P < 0.001) and overall survival (HR = 2.32, 95% CI = 1.48–363, P = 0.02).

Conclusion: The meta-analysis revealed that over-expression of β-catenin might be associated with distant metastasis and overall survival in osteosarcoma, which reminds that β-catenin acts as a prognostic biomarker and it can guide the clinical therapy in osteosarcoma patients.

β-Elemonic acid inhibits the growth of human Osteosarcoma through endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP activation and Wnt/β-catenin signal suppression

BACKGROUND

Osteosarcoma (OS) is a significant threat to the lives of children and young adults. Although neoadjuvant chemotherapy is the first choice of treatment for OS, it is limited by serious side-effects and cancer metastasis. β-Elemonic acid (β-EA), an active component extracted from Boswellia carterii Birdw., has been reported to exhibit potential anti-inflammatory and anticancer activities. However, the anti-tumor effects and underlying mechanisms on OS as well as pharmacokinetic characteristics of β-EA remain unknown.

PURPOSE

This study was aimed to investigating the anti-tumor effects of β-EA on human OS, the underlying mechanisms, and the pharmacokinetic and tissue distribution characteristics.

STUDY DESIGN AND METHODS

Cell viability and colony formation assays were performed to determine the effect of β-EA cell on cell proliferation. Apoptosis rates, mitochondrial membrane potential and cell cycle features were analyzed by flow cytometry. qRT-PCR, Western blot, immunofluorescence and immunohistochemical assays were conducted to evaluate the expression levels of genes or proteins related to the pathways affected by β-EA in vitro and in vivo. Cell migration and invasion were evaluated in wound healing and Transwell chamber assays. The effects and pharmacokinetic characteristics of β-EA in vivo were evaluated by analyzing tumor suppression, pharmacokinetics and tissue distribution.

RESULTS

Explorations indicated that endoplasmic reticulum (ER) stress conditions provoked by β-EA activated the PERK/eIF2α/ATF4 branch of the unfolded protein reaction (UPR), stimulating C/EBP homologous protein (CHOP)-regulated apoptosis and inducing Ca²⁺ leakage leading to caspase-dependent apoptosis. Furthermore, β-EA induced G0/G1 cell cycle arrest and inhibited metastasis of HOS and 143B cells by attenuating Wnt/β-catenin signaling effects, which included decreased levels of p-Akt(Ser473), p-Gsk3β (Ser9), Wnt/β-catenin target genes (c-Myc and CyclinD1) along with a decline in nuclear β-catenin accumulation. The fast absorption, short elimination half-life, and linear pharmacokinetic characteristics of β-EA were also revealed. The distribution of β-EA was detected in the tumor and bone tissues.

CONCLUSIONS

Overall, both in vitro and in vivo investigations showed the potential of β-EA for the treatment of human OS. The pharmacokinetic profile and considerable distribution in the tumor and bone tissues warrant further preclinical or even clinical studies.

Membrane metalloprotease TRABD2A restricts HIV-1 progeny production in resting CD4+ T cells by degrading viral Gag polyprotein

Resting CD4⁺ T cells are highly resistant to the production of human immunodeficiency virus type 1 (HIV-1). However, the mechanism by which resting CD4⁺ T cells restrict such production in the late viral replication phase of infection has remained unclear. In this study, we found that the cell membrane metalloprotease TRAB domain-containing protein 2A (TRABD2A) inhibited this production in resting CD4⁺ T cells by degrading the virion structural precursor polyprotein Gag at the plasma membrane. Depletion or inhibition of metalloprotease activity by TRABD2A profoundly enhanced HIV-1 production in resting CD4⁺ T cells. TRABD2A expression was much higher in resting CD4⁺ T cells than in activated CD4⁺ T cells and was considerably reduced by T cell activation. Moreover, reexpressing TRABD2A reinforced the resistance of activated CD4⁺ T cells to the production of HIV-1 progeny. Collectively, these results elucidate the molecular mechanism employed by resting CD4⁺ T cells to potently restrict the assembly and production of HIV-1 progeny.

Identification of eight genetic variants as novel determinants of dyslipidemia in Japanese by exome-wide association studies

We have performed exome-wide association studies to identify single nucleotide polymorphisms that influence serum concentrations of triglycerides, high density lipoprotein (HDL)–cholesterol, or low density lipoprotein (LDL)–cholesterol or confer susceptibility to hypertriglyceridemia, hypo–HDL-cholesterolemia, or hyper–LDL-cholesterolemia in Japanese. Exome-wide association studies for serum triglycerides (13,414 subjects), HDL-cholesterol (14,119 subjects), LDL-cholesterol (13,577 subjects), hypertriglyceridemia (4742 cases, 8672 controls), hypo–HDL-cholesterolemia (2646 cases, 11,473 controls), and hyper–LDL-cholesterolemia (4489 cases, 9088 controls) were performed with HumanExome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. Twenty-four, 69, or 32 loci were significantly (P < 1.21 × 10⁻⁶) associated with serum triglycerides, HDL-cholesterol, or LDL-cholesterol, respectively, with 13, 16, or 9 of these loci having previously been associated with triglyceride-, HDL-cholesterol–, or LDL-cholesterol–related traits, respectively. Two single nucleotide polymorphisms (rs10790162, rs7350481) were significantly related to both serum triglycerides and hypertriglyceridemia; three polymorphisms (rs146515657, rs147317864, rs12229654) were significantly related to both serum HDL-cholesterol and hypo–HDL-cholesterolemia; and six polymorphisms (rs2853969, rs7771335, rs2071653, rs2269704, rs2269703, rs2269702) were significantly related to both serum LDL-cholesterol and hyper–LDL-cholesterolemia. Among polymorphisms identified in the present study, two polymorphisms (rs146515657, rs147317864) may be novel determinants of hypo–HDL-cholesterolemia, and six polymorphisms (rs2853969, rs7771335, rs2071653, rs2269704, rs2269703, rs2269702) may be new determinants of hyper–LDL-cholesterolemia. In addition, 12, 61, 23, or 3 polymorphisms may be new determinants of the serum triglyceride, HDL-cholesterol, or LDL-cholesterol concentrations or of hyper–LDL-cholesterolemia, respectively.

CXCR6 promotes tumor cell proliferation and metastasis in osteosarcoma through the Akt pathway

Chemokine (C-X-C motif) receptor 6 (CXCR6) is up-regulated in many malignancies, indicating that CXCR6 plays an important role in tumor progression. However, the expression and function of CXCR6 in osteosarcoma (OS) remains unclear. This study aimed to explore the expression levels and function of CXCR6 in OS tissues and osteosarcoma cell lines MG-63, HOS and U2OS. The protein expression levels of CXCR6 in OS patient tissues and three osteosarcoma cell lines MG-63, HOS and U2OS were assessed. CXCR6-overexpression MG-63 cell lines were established and then the proliferation, invasion and the epithelial-mesenchymal transition (EMT) in those cells were assessed. CXCR6 mRNA levels in OS tissues were significantly higher than those in normal bone tissues. Consistently, both of the mRNA and protein levels of CXCR6 in OS cell lines MG-63, HOS and U2OS were higher than those in normal bone cells hFOB1.19. CXCR6 overexpression not only promoted cell proliferation, invasion and EMT, but also enhanced the phosphorylation of Akt in MG-63 cells. After inhibition of Akt-phosphorylation by Akt inhibitor, LY2940023, CXCR6-induced cell proliferation and invasion were dramatically attenuated. In conclusion, the present study demonstrated that CXCR6 enhances OS cell proliferation and invasion through the Akt pathway.

Downregulation of microRNA-497 is associated with upregulation of synuclein γ in patients with osteosarcoma

The present study aimed to investigate the effects of microRNA (miRNA/miR)-497 expression levels on the expression levels of synuclein γ (SNCG) in serum samples, as well as osteosarcoma and lung-metastatic tissue samples, from patients with osteosarcoma. Between December 2010 and August 2013, fasting peripheral blood was collected from 36 patients with osteosarcoma for serum separation. In addition, osteosarcoma and lung metastatic tissues were resected from 15 osteosarcoma patients with lung metastasis by surgery. Bioinformatics was employed to predict the amount miRNA that binds to SNCG. Reverse transcription-quantitative polymerase chain reaction was used to determine the expression levels of SNCG and miR-497, and western blotting was performed to determine protein expression levels. It was observed that SNCG mRNA and protein expression levels were significantly upregulated in osteosarcoma tissues (P<0.01). Additionally, SNCG mRNA (P<0.01) and protein (P<0.05) expression levels were significantly upregulated in the blood of patients with osteosarcoma. SNCG mRNA and protein expression levels were also significantly upregulated in lung metastatic tissues (P<0.01). miR-497 was significantly downregulated in all three samples; therefore downregulation of miR-497 may lead to the occurrence, development and metastasis of osteosarcoma through the upregulation of SNCG mRNA. In summary, the upregulation of SNCG in blood, osteosarcoma tissue and lung metastatic tissue samples is associated with the dowregulation of miR-497, suggesting that miR-497 may be a potential marker and therapeutic target for the treatment of osteosarcoma.

TIKI2 is upregulated and plays an oncogenic role in renal cell carcinoma

TIKI2 is a negative regulator of the Wnt family. Although many Wnt antagonists play important roles in renal cell carcinoma (RCC), the molecular function of TIKI2 in human RCC has not been fully elucidated. Here, we analyzed TIKI2 mRNA level in RCC specimens, the corresponding non-tumor tissues, RCC cell lines, and human proximal tubule epithelial cell line HK-2 using qPCR. We demonstrated that TIKI2 was highly expressed in RCC tissue (P < 0.05) and most RCC cell lines. In vitro, TIKI2 knockdown significantly inhibited proliferation, invasion, and clone formation ability of 769-P cells compared with controls, while ectopic TIKI2 expression enhanced A498 cell proliferation, invasion, and clone formation ability. In vivo, the average tumor volume was significantly increased in mice injected with A498-Tiki2 cells (P < 0.05). In the 769-P cell TIKI2 knockdown group, the average tumor volume was not significantly different compared to that of the control group (P = 0.08). Moreover, Wnt/β-catenin signaling was not affected by TIKI2 knockdown or overexpression. Results of the present study indicate that TIKI2 is upregulated in RCC tissues and plays an oncogenic role in RCC.

Ribosomal protein S15A augments human osteosarcoma cell proliferation in vitro

As a highly conserved housekeeping gene, the biological implications of ribosomal protein S15A (RPS15A) during various processes, including carcinogenesis, remain elusive. Herein, the authors reported that knockdown of RPS15A expression significantly inhibited human osteosarcoma U2OS cell proliferation and colony formation in vitro by using a lentivirus-mediated RNA interference (RNAi) system. Moreover, an excess accumulation of cells in the G0/G1 phase was observed in U2OS cells transduced with lentivirus targeting RPS15A, suggesting that the growth inhibition mediated by RPS15A knockdown in osteosarcoma cells was probably due to the induction of cell cycle arrest. Taken together, this study highlights the crucial role of RPS15A in promoting osteosarcoma cell proliferation, and provides a foundation for further study into the clinical potential of inhibition of RPS15A for the treatment of osteosarcoma.

Expression and evolution of the Tiki1 and Tiki2 genes in vertebrates

Tiki1 is a Wnt protease and antagonist specifically expressed in the Spemann-Mangold Organizer and is required for head formation in Xenopus embryos. Here we report neighbor-joining phylogenetic analysis of vertebrate Tiki genes and their mRNA expression patterns in chick, mouse, and rabbit embryos. Tiki1 and Tiki2 orthologues are highly conserved, and exhibit similar but also different developmental expression patterns among the vertebrate/mammalian species analyzed. The Tiki1 gene is noticeably absent in the rodent lineage, but is present in lagomorphs and all other vertebrate/mammalian species examined. Expression in Hensen's node, the equivalent of the Xenopus Organizer, was observed for Chick Tiki2 and Rabbit Tiki1 and Tiki2. Mouse Tiki2 was detected at low levels at gastrulation and head fold stages, but not in the node. Mouse Tiki2 and chick Tiki1 display similar expression in the dorsal spinal cord. Chick Tiki1 expression was also detected in the surface ectoderm and maxillary bud, while chick Tiki2 was found in the anterior intestinal portal, head mesenchyme and primitive atrium. Our expression analyses provide evidence that Tiki1 and Tiki2 are evolutionarily conserved among vertebrate species and their expression in the Organizer and other regions suggests contributions of these Wnt inhibitors to embryonic patterning, as well as organogenesis. Our analyses further reveal mis-regulation of TIKI1 and TIKI2 in human cancer and diseases.

HMGB1 promotes cellular proliferation and invasion, suppresses cellular apoptosis in osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents. Unfortunately, treatment failures are common due to the metastasis and chemoresistance, but the underlying molecular mechanism remains unclear. Accumulating evidence indicated that the deregulation of DNA-binding protein high-mobility group box 1 (HMGB1) was associated with the development of cancer. This study aimed to explore the expression of HMGB1 in osteosarcoma tissues and its correlation to the clinical pathology of osteosarcoma and to discuss the role of HMGB1 in the development of osteosarcoma. The results from RT-PCR and Western blot showed that the expression rate of HMGB1 messenger RNA (mRNA) and the expression of HMGB1 in the osteosarcoma tissues were significantly higher than those in normal bone tissue (p < 0.05), the expression rate of HMGB1 mRNA and the expression of HMGB1 in the carcinoma tissues with positive lung metastasis were significantly higher than those without lung metastasis (p < 0.05), and with increasing Enneking stage, the expression rate of HMGB1 mRNA and the expression of HMGB1 also increased (p < 0.05). In order to explore the role of HMGB1 in osteosarcoma, the expression of HMGB1 in the human osteosarcoma MG-63 cell line was downregulated by the technique of RNA interference. Western blot results showed that the protein expression of HMGB1 was significantly decreased in the MG-63 cells from HMGB1-siRNA transfection group (p < 0.05), which suggested that HMGB1 was successfully downregulated in the MG-63 cells. Then the changes in proliferation, apoptosis, and invasion of MG-63 cells were examined by MTT test, PI staining, annexin V staining, and transwell chamber assay. Results showed that the abilities of proliferation and invasion were suppressed in HMGB1 knockdown MG-63 cells, and the abilities of apoptosis were enhanced in HMGB1 knockdown MG-63 cells. The expression of cyclin D1, MMP-9 was downregulated in HMGB1 knockdown MG-63 cells, and the expression of caspase-3 was upregulated in HMGB1 knockdown MG-63 cells. Taken together, the overexpression of HMGB1 in osteosarcoma might be related to the tumorigenesis, invasion, and metastasis of osteosarcoma, which might be a potential target for the treatment of osteosarcoma.