TRIM33 is essential for osteoblast proliferation and differentiation via BMP pathway

The Roles of Forkhead Box O3a (FOXO3a) in Bone and Cartilage Diseases - A Narrative Review

Bone and cartilage diseases are significantly associated with musculoskeletal disability. However, no effective drugs are available to cure them. FOXO3a, a member of the FOXO family, has been implicated in cell proliferation, ROS detoxification, autophagy, and apoptosis. The biological functions of FOXO3a can be modulated by post-translational modifications (PTMs), such as phosphorylation and acetylation. Several signaling pathways, such as MAPK, NF-κB, PI3K/AKT, and AMPK/Sirt1 pathways, have been implicated in the development of bone and cartilage diseases by mediating the expression of FOXO3a. In particular, FOXO3a acts as a transcriptional factor in mediating the expression of various genes, such as MnSOD, CAT, BIM, BBC3, and CDK6. FOXO3a plays a critical role in the metabolism of bone and cartilage. In this article, we mainly discussed the biological functions of FOXO3a in bone and cartilage diseases, such as osteoporosis (OP), osteoarthritis (OA), rheumatoid arthritis (RA), ankylosing spondylitis (AS), and intervertebral disc degeneration (IDD). FOXO3a can promote osteogenic differentiation, induce osteoblast proliferation, inhibit osteoclast activity, suppress chondrocyte apoptosis, and reduce inflammatory responses. Collectively, up-regulation of FOXO3a expression shows beneficial effects, and FOXO3a has become a potential target for bone and cartilage diseases.

Developmental dysplasia of the hip caused by homozygous TRIM33 pathogenic variant affecting downstream BMP pathway

BACKGROUND

Developmental dysplasia of the hip (DDH), formerly termed congenital dislocation of the hip, is the most common congenital disease of the musculoskeletal system in newborns. While familial predilection to DDH has been well documented, the molecular genetics/pathways of this common disorder are poorly understood.

METHODS

Linkage analysis and whole exome sequencing; real-time PCR studies of skin fibroblasts.

RESULTS

Consanguineous Bedouin kindred presented with DDH with apparent autosomal recessive heredity. Linkage analysis and whole exome sequencing delineated a single 3.2 Mbp disease-associated chromosome 1 locus (maximal multipoint Logarithm of the Odds score 2.3), containing a single homozygous variant with a relevant expression pattern: addition of threonine in TRIM33 (NM_015906.4); c.1648_1650dup. TRIM33 encodes a protein that acts both in the TGF-β and the BMP pathways; however, it has been mostly studied regarding its function in the TGF-β pathway. Since BMPs are known to act in bone formation, we focused on the BMP pathway, in which TRIM33 functions as a transcription factor, both an activator and repressor. Skin fibroblasts of two affected girls and a heterozygous TRIM33 variant carrier were assayed through reverse-transcription PCR for expression of genes known to be downstream of TRIM33 in the BMP pathway: fibroblasts of affected individuals showed significantly reduced expression of DLX5, significantly increased expression of BGLAP, increased expression of ALPL and no change in expression of RUNX2 or of TRIM33 itself.

CONCLUSIONS

DDH can be caused by a biallelic variant in TRIM33, affecting the BMP pathway.

TRIM33 enhances the ubiquitination of TFRC to enhance the susceptibility of liver cancer cells to ferroptosis

BACKGROUND

Hepatocellular carcinoma (HCC) is a common malignancy, and ferroptosis is a novel form of cell death driven by excessive lipid peroxidation. In recent years, ferroptosis has been widely utilized in cancer treatment, and the ubiquitination modification system has been recognized to play a crucial role in tumorigenesis and metastasis. Increasing evidence suggests that ubiquitin regulates ferroptosis-related substrates involved in this process. However, the precise mechanism of utilizing ubiquitination modification to regulate ferroptosis for HCC treatment remains unclear.

METHODS

In this study, we detected the expression of TRIM33 in HCC using immunohistochemistry and western blotting techniques. The functional role of TRIM33 was verified through both in vitro and in vivo experiments. To evaluate the level of ferroptosis, mitochondrial superoxide levels, MDA levels, Fe2+ levels, and cell viability were assessed. Downstream substrates of TRIM33 were screened and confirmed via immunoprecipitation, immunofluorescence staining, and ubiquitination modification experiments.

RESULTS

Our findings demonstrate that TRIM33 inhibits the growth and metastasis of HCC cells both in vitro and in vivo while promoting their susceptibility to ferroptosis. Mechanistically speaking, TRIM33 induces cellular ferroptosis through E3 ligase-dependent degradation of TFRC-a known inhibitor of this process-thus elucidating the specific type and site at which TFRC undergoes modification by TRIM33.

CONCLUSION

In summary, our study reveals an important role for TRIM33 in HCC treatment while providing mechanistic support for its function. Additionally highlighted is the significance of ubiquitination modification leading to TFRC degradation-an insight that may prove valuable for future targeted therapies.

Asymmetric and parallel subgenome selection co-shape common carp domestication

BACKGROUND

The common carp (Cyprinus carpio) might best represent the domesticated allopolyploid animals. Although subgenome divergence which is well-known to be a key to allopolyploid domestication has been comprehensively characterized in common carps, the link between genetic architecture underlying agronomic traits and subgenome divergence is unknown in the selective breeding of common carps globally.

RESULTS

We utilized a comprehensive SNP dataset in 13 representative common carp strains worldwide to detect genome-wide genetic variations associated with scale reduction, vibrant skin color, and high growth rate in common carp domestication. We identified numerous novel candidate genes underlie the three agronomically most desirable traits in domesticated common carps, providing potential molecular targets for future genetic improvement in the selective breeding of common carps. We found that independently selective breeding of the same agronomic trait (e.g., fast growing) in common carp domestication could result from completely different genetic variations, indicating the potential advantage of allopolyploid in domestication. We observed that candidate genes associated with scale reduction, vibrant skin color, and/or high growth rate are repeatedly enriched in the immune system, suggesting that domestication of common carps was often accompanied by the disease resistance improvement.

CONCLUSIONS

In common carp domestication, asymmetric subgenome selection is prevalent, while parallel subgenome selection occurs in selective breeding of common carps. This observation is not due to asymmetric gene retention/loss between subgenomes but might be better explained by reduced pleiotropy through transposable element-mediated expression divergence between ohnologs. Our results demonstrate that domestication benefits from polyploidy not only in plants but also in animals.

Trim21 depletion alleviates bone loss in osteoporosis via activation of YAP1/β-catenin signaling

Despite the diverse roles of tripartite motif (Trim)-containing proteins in the regulation of autophagy, the innate immune response, and cell differentiation, their roles in skeletal diseases are largely unknown. We recently demonstrated that Trim21 plays a crucial role in regulating osteoblast (OB) differentiation in osteosarcoma. However, how Trim21 contributes to skeletal degenerative disorders, including osteoporosis, remains unknown. First, human and mouse bone specimens were evaluated, and the results showed that Trim21 expression was significantly elevated in bone tissues obtained from osteoporosis patients. Next, we found that global knockout of the Trim21 gene (KO, Trim21-/-) resulted in higher bone mass compared to that of the control littermates. We further demonstrated that loss of Trim21 promoted bone formation by enhancing the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and elevating the activity of OBs; moreover, Trim21 depletion suppressed osteoclast (OC) formation of RAW264.7 cells. In addition, the differentiation of OCs from bone marrow-derived macrophages (BMMs) isolated from Trim21-/- and Ctsk-cre; Trim21f/f mice was largely compromised compared to that of the littermate control mice. Mechanistically, YAP1/β-catenin signaling was identified and demonstrated to be required for the Trim21-mediated osteogenic differentiation of BMSCs. More importantly, the loss of Trim21 prevented ovariectomy (OVX)- and lipopolysaccharide (LPS)-induced bone loss in vivo by orchestrating the coupling of OBs and OCs through YAP1 signaling. Our current study demonstrated that Trim21 is crucial for regulating OB-mediated bone formation and OC-mediated bone resorption, thereby providing a basis for exploring Trim21 as a novel dual-targeting approach for treating osteoporosis and pathological bone loss.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

KLF9 positively regulates TRIM33 to inhibit abnormal synovial fibroblast proliferation, migration as well as inflammation in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) can cause irreversible joint injury and serious disability. This study aimed to investigate how TRIM33 regulated by KLF9 affects the aggressive behaviors of synovial fibroblasts induced by tumor necrosis factor-α (TNF-α).

MATERIALS AND METHODS

TNF-α-induced MH7A cells were used to simulate the in vitro model of RA. TRIM33 and KLF9 expression in TNF-α-challenged MH7A cells and transfection efficiency were analyzed via real-time reverse transcription polymerase chain reaction together with western blot. The viability, proliferation, invasion, and migration of TNF-α-induced MH7A cells after transfection was respectively detected by CCK-8, EdU staining, transwell, and wound-healing assays. The expression of invasion and migration-related proteins and inflammation-related proteins was determined by western blot and the levels of inflammatory factors were detected by enzyme-linked immunosorbent assay. The combination between TRIM33 and KLF9 was substantiated through dual-luciferase reporter assay and chromatin immunoprecipitation.

RESULTS

TRIM33 and KLF9 expression in TNF-α-challenged MH7A cells was downregulated. TRIM33 elevation inhibited TNF-α-elicited proliferation, metastasis as well as inflammation of MH7A cells. Moreover, KLF9 was combined with TRIM33 and KLF9 promoted transcription of TRIM33. The inhibitory effect of TRIM33 overexpression on proliferation, invasion and migration and inflammation of MH7A cells induced by TNF-α was alleviated by the downregulation of KLF9.

CONCLUSION

KLF9 positively regulates TRIM33 to suppress the abnormal MH7A cell proliferation, migration, and reduce inflammation upon exposure to TNF-α, which was reversed by inhibiting KLF9.

E3 Ubiquitin Ligases: Potential Therapeutic Targets for Skeletal Pathology and Degeneration

The ubiquitination-proteasome system (UPS) is crucial in regulating a variety of cellular processes including proliferation, differentiation, and survival. Ubiquitin protein ligase E3 is the most critical molecule in the UPS system. Dysregulation of the UPS system is associated with many conditions. Over the past few decades, there have been an increasing number of studies focusing on the UPS system and how it affects bone metabolism. Multiple E3 ubiquitin ligases have been found to mediate osteogenesis or osteolysis through a variety of pathways. In this review, we describe the mechanisms of UPS, especially E3 ubiquitin ligases on bone metabolism. To date, many E3 ubiquitin ligases have been found to regulate osteogenesis or osteoclast differentiation. We review the classification of these E3 enzymes and the mechanisms that influence upstream and downstream molecules and transduction pathways. Finally, this paper reviews the discovery of the relevant UPS inhibitors, drug molecules, and noncoding RNAs so far and prospects the future research and treatment.

Long Noncoding RNA Zinc Finger Antisense 1 Affects Glucocorticoid-Induced Osteonecrosis of the Femoral Head by Performing as a ceRNA for MicroRNA-124-3p and Accelerating Transforming Growth Factor Type III Receptor

In recent years, plentiful studies have uncovered the long noncoding RNA's (lncRNA's) momentous functions in osteonecrosis of the femoral head (ONFH), but the specific mechanism has not been fully illustrated. The study was to figure out lncRNA Zinc finger antisense 1 (LncZFAS1)'s biological function and its latent downstream molecular mechanism in glucocorticoid- (GC-) induced ONFH. The results manifested LncZFAS1 and transforming growth factor type III receptor (TGFBR3) were elevated, while microRNA- (miR-) 124-3p was reduced in ONFH tissues and cells. Knockdown LncZFA1 reduced rat femoral cell apoptosis, perfected bone microstructure and bone density, and accelerated osteogenic proteins bone morphogenetic protein- (BMP-) 9, BMP-3, and osteocalcin. In vitro studies manifested knockdown LncZFAS1 prevented GC-induced reduction in osteoblast advancement with facilitating osteoblast calcification capacity, ALP activity, and osteogenic proteins. Elevation of LncZFAS1 further aggravated GC-induced osteoblast injury, but this effect was turned around by enhancement of miR-124-3p or knockdown of TGFBR3. Mechanistically, LncZFAS1 performed as a sponge for miR-124-3p to mediate TGFBR3 expression to motivate GC-induced ONFH. All in all, the results of this study indicate the LncZFAS1/miR-124-3p/TGFBR3 axis is supposed to be a latent therapeutic molecular target for GC-induced ONFH.

Downregulation of TRIM33 Promotes Survival and Epithelial-Mesenchymal Transition in Gastric Cancer

Among all malignancies worldwide, gastric cancer is the fifth most common cancer with the third highest mortality rate. One of the main reasons for the low survival rate is the recurrence and metastasis that occurs in many patients after surgery. Numerous studies have shown that abnormal TRIM33 expression is associated with the progression of malignant tumors. TRIM33 can function either as a tumor suppressor or tumor promoter in different cancers. Our data showed that TRIM33 was highly expressed in stomach cancer, and in human gastric cancer tissues, low expression of TRIM33 was associated with poor prognosis in patients with gastric cancer. To clarify the function of TRIM33 in survival and epithelial–mesenchymal transition in gastric cancer cells, we investigated the effect of TRIM33 knockdown in several gastric cancer cell lines. Downregulation of TRIM33 in BGC-823 and SGC-7901 cells enhanced the proliferation, colony formation, and migratory ability of these gastric cancer cells. It also promoted epithelial–mesenchymal transition; transfection of cells with siRNA targeting TRIM33 led to the upregulation of vimentin and N-Cadherin expression, and downregulation of E-Cadherin expression. Meanwhile, the transforming growth factor beta pathway was activated: levels of transforming growth factor beta were elevated and the expressions of p-Smad2, Smad2, Smad3, and Smad4 were activated. To confirm the role of TRIM33 in vivo, a xenograft model was established in nude mice. Immunohistochemical analysis identified that the protein levels of TRIM33, p-Smad2, Smad2, Smad3, Smad4, vimentin, and N-Cadherin were increased, and E-Cadherin levels were decreased, in xenograft tumors from the si-TRIM33 group. Taken together, these results suggest that TRIM33 may be a potential marker for the diagnosis and prognosis of gastric cancer. Furthermore, it may also serve as a novel target for gastric cancer treatment.

TRIM proteins in fibrosis

Fibrosis is an outcome of tissue repair after different types of injuries. The homeostasis of extracellular matrix is broken, and excessive deposition occurs, affecting the normal function of tissues and organs, which could become prostrated in serious cases.Finding a suitable target to regulate the repair process and reduce the damage caused by fibrosis is a hot research topic at present. The TRIM family is number of one of the E3 ubiquitin ligase subfamilies and participates in various biological processes including intracellular signal transduction, apoptosis, autophagy, and immunity by regulating the ubiquitination of target proteins. For the past few years, the important role of TRIM in the occurrence and development of fibrosis has been gradually revealed. In this review, we focus on the recent emerging topics on TRIM proteins in the regulation of fibrosis, fibrosis-related cytokines and pathways.

TRIM33 protects osteoblasts from oxidative stress-induced apoptosis in osteoporosis by inhibiting FOXO3a ubiquitylation and degradation

This study aimed to probe into the effect of TRIM33 on oxidative stress‐induced apoptosis of osteoblasts in osteoporosis and to probe into the underlying mechanism. The apoptosis of osteoblasts was induced by H₂O₂ treatment and tested by flow cytometry. A mouse osteoporosis model was conducted by ovariectomy (OVX). The function of TRIM33 was assessed by in vitro and in vivo experiments. The mechanism of TRIM33 was determined by immunoprecipitation, immunofluorescent staining and co‐transfection experiments. Here, we found that TRIM33 expression was lessened in the osteoblasts of patients with osteoporosis and was positively correlated with the bone mineral density of these patients. FOXO3a and TRIM33 were co‐localized in the osteoblasts nuclei. TRIM33 silence boosted FOXO3a degradation in normal osteoblasts, while TRIM33 overexpression restrained FOXO3a degradation in H₂O₂‐treated osteoblasts. The binding of TRIM33 to CBP and its overexpression restrained CBP‐mediated FOXO3a acetylation, thereby attenuating FOXO3a ubiquitylation. The H₂O₂‐induced apoptosis of osteoblasts was restrained by TRIM33 overexpression, while the FOXO3a knockdown reversed this trend. The in vivo experiments corroborated that TRIM33 overexpression attenuated the OVX‐driven impacts in mice. In general, our findings expounded that TRIM33 protected osteoblasts against oxidative stress‐induced apoptosis in osteoporosis and that the underlying mechanism was the restraint of FOXO3a ubiquitylation and degradation.

miRNA-92a-3p regulates osteoblast differentiation in patients with concomitant limb fractures and TBI via IBSP/PI3K-AKT inhibition

Patients who sustain concomitant fractures and traumatic brain injury (TBI) are known to have significantly quicker fracture-healing rates than patients with isolated fractures. The mechanisms underlying this phenomenon have yet to be identified. In the present study, we found that the upregulation of microRNA-92a-3p (miRNA-92a-3p) induced by TBI correlated with a decrease in integrin binding sialoprotein (IBSP) expression in callus formation. In vitro, overexpressing miRNA-92a-3p inhibited IBSP expression and accelerated osteoblast differentiation, whereas silencing of miRNA-92a-3p inhibited osteoblast activity. A decrease in IBSP facilitated osteoblast differentiation via the Phosphatidylinositol 3-kinase/threonine kinase 1 (PI3K/AKT) signaling pathway. Through luciferase assays, we found evidence that IBSP is a miRNA-92a-3p target gene that negatively regulates osteoblast differentiation. Moreover, the present study confirmed that pre-injection of agomiR-92a-3p leads to increased bone formation. Collectively, these results indicate that miRNA-92a-3p overexpression may be a key factor underlying the improved fracture healing observed in TBI patients. Upregulation of miRNA-92a-3p may therefore be a promising therapeutic strategy for promoting fracture healing and preventing nonunion.

Alteration of TRIM33 Expression at Transcriptional and Translational Levels is Correlated with Autism Symptoms

As a complex neurodevelopmental disorder, autism affects children in three major cognitive domains including social interactions, language learning and repetitive stereotyped behaviors. Abnormal regulation of cell proliferation in the brain during the embryonic period via the TGF-β signaling pathway and TRIM33 gene that encodes a protein with a corepressor and regulatory role in this pathway has been considered as an etiology for autism. Here, we investigated the association of a variation of TRIM33 with autism symptoms at levels of mRNA and protein expression. We used Autism Diagnostic Interview-Revised (ADI-R) and Childhood Autism Rating Scale (CARS) as behavioral diagnostic tools. Normal and autistic children were genotyped for a TRIM33 polymorphism (rs11102807), and then expression was assessed at transcriptional and translational levels. Results demonstrated that the frequency of the homozygous A allele (AA genotype of rs11102807) was significantly higher in children with autism (P < 0.001), whereas carriers of the G allele were mostly among healthy individuals. Children homozygous for the rs11102807 A allele were associated with an increase in CARS and ADI-R scores, indicating a significant correlation with autism symptoms. TRIM33 gene expression at both mRNA (P < 0.01) and protein (P < 0.001) levels was significantly higher in controls compared to autistic children. A remarkable association between higher TRIM33 gene expression at the transcriptional level and lower scores for both CARS and ADI-R was observed in non-autistic children. It seems that rs11102807 modulates the function and expression of the TRIM33 gene, implying that the A allele may increase the risk of autism in children by reducing gene expression and altering the TGF-β signaling pathway.

Anti-TIF1-γ autoantibodies: warning lights of a tumour autoantigen

Anti-transcription intermediary factor 1 (TIF1)-γ autoantibodies are robustly linked with cancer-associated DM in adults. This review aims to give an overview of the physiological context of TIF1-γ and to determine whether there is a pathophysiological link between anti-TIF1-γ autoantibodies and the occurrence of cancer. Detection of anti-TIF1-γ autoantibodies has a high sensitivity and specificity for cancer-associated DM in adults and is therefore useful for both diagnosis and cancer risk stratification. The function of the autoantigen, TIF1-γ, may provide insight into the mechanism behind this association. TIF1-γ is a ubiquitously present protein involved in various biological pathways, including TGF-β signalling. In cancer, it can act either as a tumour suppressor or promoter, depending on the cellular context and cancer stage. Evolving data provide pathophysiological insights, linking anti-TIF1-γ autoantibodies to both the anti-tumour response and to muscle and skin damage. TIF1-γ expression is increased in muscle and skin tissue of patients with DM. Mutations or loss-of-heterozygosity in TIF1-γ alleles in malignant tissue may result in the expression of tumour-specific neo-antigens stimulating autoantibody production. The newly formed autoantibodies are hypothesized to cross-react with antigens in muscle and skin, driving the development of DM. Based on the current evidence, anti-TIF1-γ autoantibodies should be considered warning lights of a potential tumour autoantigen and should alert the physician to the possibility of an underlying cancer.

Integration of IgA and IgG Autoantigens Improves Performance of Biomarker Panels for Early Diagnosis of Lung Cancer

Lung cancer (LC) remains the leading cause of mortality from malignant tumors worldwide. In our previous study, we surveyed both IgG and IgM-bound serological biomarkers and validated a panel of IgG-bound autoantigens for early LC diagnosis with 50% sensitivity at 90% specificity. To further improve the performance of these serological biomarkers, we surveyed HuProt arrays, comprised of 20,240 human proteins, for IgA-bound autoantigens because IgAs are a major immunoglobulin isotype in the lung. Integrating with IgG-bound autoantigens, we discovered and validated a combined biomarker panel using ELISA-format tests. Specifically, in Phase I, we obtained IgA-based autoimmune profiles of 69 early stage LC patients, 30 healthy subjects and 25 patients with lung benign lesions (LBL) on HuProt arrays and identified 28 proteins as candidate autoantigens that were significantly associated with early stage LC. In Phase II, we re-purified the autoantigens and converted them into an ELISA-format testing to profile an additional large cohort, comprised of 136 early stage LC patients, 58 healthy individuals, and 29 LBL patients. Integration of IgG autoimmune profiles allowed us to identify and validate a biomarker panel of three IgA autoantigens (i.e. BCL7A, and TRIM33 and MTERF4) and three IgG autoantigens (i.e. CTAG1A, DDX4 and MAGEC2) for diagnosis of early stage LC with 73.5% sensitivity at >85% specificity. In Phase III, the performance of this biomarker panel was confirmed with an independent cohort, comprised of 88 early stage LC patients, 18 LBL patients, and 36 healthy subjects. Finally, a blind test on 178 serum samples was conducted to confirm the performance of the biomarker panel. In summary, this study demonstrates for the first time that an integrated panel of IgA/IgG autoantigens can serve as valuable biomarkers to further improve the performance of early diagnosis of LC.

The Roles of TIF1γ in Cancer

Transcriptional intermediary factor 1 γ (TIF1γ), also known as TRIM33, RFG7, PTC7, or Ectodermin, is an E3 ubiquitin-ligase family member with a ring-box-coiled-coil region. It can regulate TGF-β/Smad signaling in two different ways in different cellular contexts. On one hand, TIF1γ can monoubiquitinate Smad4 to inhibit the formation of Smad2/3/4 nuclear complexes. On the other hand, TIF1γ can function as a cofactor of phosphorylated (p)-Smad2/3, competing with Smad4 to inhibit the formation of the Smad2/3/4 complex. In addition, TIF1γ has been reported to play a role in transcription elongation, cellular differentiation, embryonic development, and mitosis. As transforming growth factor-β (TGF-β) superfamily signaling plays an important role in the occurrence and development of cancer, and TIF1γ was reported to be involved in the regulation of TGF-β superfamily signaling, studies on TIF1γ during the last decade have focused on its role in the development of cancer. However, TIF1γ can function either as a tumor suppressor or promoter in different cellular contexts, yet there are few reviews focusing on the roles of TIF1γ in cancer. Hence, in this paper we systematically review and discuss the roles of TIF1γ in cancer. Firstly, we review the biological features, the regulatory mechanisms and the related signaling pathways of TIF1γ. Next, we illustrate the roles of TIF1γ in different tumors. We then provide a tentative hypothesis that explains the dual roles of TIF1 γ in cancer. Finally, we provide our viewpoint regarding the future developments of cancer research focusing on TIF1γ, especially in relation to the effects of TIF1γ on tumoral immunity.

Novel Calcium Phosphate Cement with Metformin-Loaded Chitosan for Odontogenic Differentiation of Human Dental Pulp Cells

Metformin is an old and widely accepted first-line drug for treating type 2 diabetes. Our previous studies demonstrate that metformin can stimulate the osteo/odontogenic differentiation of human-induced pluripotent stem cell-derived mesenchymal stem cells and human dental pulp cells (DPCs). Due to the rapid dilution of metformin from the defect area, the aim of this study was to develop a drug delivery system with controlled release of metformin to promote cell viability and odontogenic differentiation of DPCs favoring dentin regeneration. Calcium phosphate cement (CPC) containing chitosan and metformin as a scaffold was synthesized. DPCs were seeded onto the scaffold, and the viability and proliferation were evaluated at several time points. For osteogenic differentiation analysis, alkaline phosphatase (ALP) activity was tested, cells were stained with Alizarin Red, and the expression of odontogenic markers was evaluated by real-time polymerase chain reaction. DPCs remained viable and attached well to the CPC-chitosan composite scaffold. Moreover, the addition of metformin to the CPC-chitosan composite did not adversely affect cell proliferation, compared to that of CPC control. Our data further revealed that the novel CPC-chitosan-metformin composite enhanced the odontogenic differentiation of DPCs, as evidenced by higher ALP activity, elevated expression of odontoblastic markers, and strong mineral deposition. These results suggest that the new CPC-chitosan-metformin composite is a highly promising scaffold with the potential for tissue engineering applications including dentin regeneration.

Metformin Enhances the Differentiation of Dental Pulp Cells into Odontoblasts by Activating AMPK Signaling

INTRODUCTION

Metformin is a first-line drug for treating type 2 diabetes that regulates the differentiation of mesenchymal stem cells. Its effects on human dental pulp cells (DPCs) remain unknown. This study aimed to investigate the effects of metformin on the proliferation and differentiation of DPCs.

METHODS

A live/dead viability assay kit was used to examine the effects of metformin on the cell viability of DPCs. Cell proliferation was analyzed using a cell counting kit (CCK-8; Dojindo, Tokyo, Japan). Levels of phosphorylated and unphosphorylated adenosine 5'-monophosphate-activated protein kinase (AMPK) were quantified by Western blot analysis in response to metformin and the AMPK signaling inhibitor Compound C (EMD Chemicals, San Diego, CA). The effects of Compound C on the metformin-induced odontoblast differentiation of DPCs were determined by alkaline phosphatase activity assay and von Kossa staining, and the expression of odontoblastic markers was evaluated by reverse-transcription polymerase chain reaction analysis.

RESULTS

DPCs exhibited mesenchymal stem cell characteristics using flow cytometry. Different doses of metformin were shown to be cytocompatible with DPCs, yielding >90% cell viability. None of the concentrations of metformin up to 50 μmol/L affected cell proliferation. The Western blot assay showed that DPCs express functional organic cation transporter 1, a transmembrane protein that mediates the intracellular uptake of metformin. Metformin significantly activated the AMPK pathway in a dose-dependent manner. In addition, it stimulated alkaline phosphatase activity; enhanced mineralized nodule formation; and increased the expression of odontoblastic markers including dentin sialophosphoprotein, dentin matrix protein 1, runt-related transcription factor 2, and osteocalcin. Moreover, pretreatment with Compound C, a specific AMPK inhibitor, markedly reversed metformin-induced odontoblastic differentiation and cell mineralization.

CONCLUSIONS

This study shows that metformin can induce DPC differentiation and mineralization in an AMPK-dependent manner and that this well-tolerated antidiabetic drug has potential in regenerative endodontics as well as in other regenerative applications.

Alcohol Inhibits Odontogenic Differentiation of Human Dental Pulp Cells by Activating mTOR Signaling

Long-term heavy alcohol consumption could result in a range of health, social, and behavioral problems. People who abuse alcohol are at high risks of seriously having osteopenia, periodontal disease, and compromised oral health. However, the role of ethanol (EtOH) in the biological functions of human dental pulp cells (DPCs) is unknown. Whether EtOH affects the odontoblastic differentiation of DPCs through the mechanistic target of rapamycin (mTOR) remains unexplored. The objective of this study was to investigate the effects of EtOH on DPC differentiation and mineralization. DPCs were isolated and purified from human dental pulps. The proliferation and odontoblastic differentiation of DPCs treated with EtOH were subsequently investigated. Different doses of EtOH were shown to be cytocompatible with DPCs. EtOH significantly activated the mTOR pathway in a dose-dependent manner. In addition, EtOH downregulated the alkaline phosphatase activity, attenuated the mineralized nodule formation, and suppressed the expression of odontoblastic markers including ALP, DSPP, DMP-1, Runx2, and OCN. Moreover, the pretreatment with rapamycin, a specific mTOR inhibitor, markedly reversed the EtOH-induced odontoblastic differentiation and cell mineralization. Our findings show for the first time that EtOH can suppress DPC differentiation and mineralization in a mTOR-dependent manner, indicating that EtOH may be involved in negatively regulating the dental pulp repair.

Dermatomyositis and Immune-Mediated Necrotizing Myopathies: A Window on Autoimmunity and Cancer

Autoimmune myopathies (myositides) are strongly associated with malignancy. The link between myositis and cancer, originally noticed by Bohan and Peter in their classification in 1975 (1), has been evidenced by large population-based cohort studies and a recent meta-analysis. The numerous reports of cases in which the clinical course of myositis reflects that of cancer and the short delay between myositis and cancer onset support the notion that myositis may be an authentic paraneoplastic disorder. Thus, cancer-associated myositis raises the question of cancer as a cause rather than a consequence of autoimmunity. Among myositides, dermatomyositis and more recently, although to a lesser extent, immune-mediated necrotizing myopathies are the most documented forms associated with cancer. Interestingly, the current diagnostic approach for myositis is based on the identification of specific antibodies where each antibody determines specific clinical features and outcomes. Recent findings have shown that the autoantibodies anti-TIF1γ, anti-NXP2 and anti-HMGCR are associated with cancers in the course of myositis. Herein, we highlight the fact that the targets of these three autoantibodies involve cellular pathways that intervene in tumor promotion and we discuss the role of cancer mutations as autoimmunity triggers in adult myositis.