Background Natural killer (NK) cells are key effectors in antitumor immunity, yet their function is markedly suppressed by transforming growth factor-β (TGF-β) in the tumor microenvironment. SMAD7 is an established intracellular antagonist of TGF-β signaling, but its specific role within NK cells remains poorly defined. Methods The clinical relevance of SMAD7 in tumor-infiltrating NK cells was evaluated via integrative analyses of public single-cell and bulk transcriptomic datasets. Functional studies included loss-of-function experiments using NK cell-conditional Smad7 knockout mice in syngeneic tumor models and gain-of-function experiments using a SMAD7-overexpressing human NK-92MI cell line. NK cell antitumor function was assessed through cytotoxicity assays and by measuring the expression of selected effector and exhaustion markers. SMAD7-mediated transcriptional targets were identified by integrating RNA sequencing, chromatin immunoprecipitation followed by quantitative PCR, and luciferase reporter assays. The potential role of SMAD7 in NK cell-based therapy was evaluated in adoptive transfer tumor models. Results High SMAD7 expression in tumor-infiltrating NK cells was associated with a favorable patient prognosis across multiple cancer types. Conditional deletion of SMAD7 in NK cells markedly impaired their antitumor cytotoxicity, leading to accelerated tumor progression in mouse models of both pancreatic and liver cancers. In contrast, SMAD7 overexpression enhanced NK cell cytotoxicity and alleviated functional exhaustion, partly by counteracting TGF-β-mediated suppression. Notably, we uncovered a previously unrecognized nuclear function of SMAD7 in NK cells. SMAD7 directly binds to the STAT5A promoter and promotes its transcription, thereby strengthening STAT5A signaling in NK cells. Disruption of STAT5A largely abolished the enhanced cytotoxicity conferred by wild-type SMAD7 and completely abrogated the effect of a SMAD7 mutant, which was defective in TGF-β receptor binding. In in vivo therapeutic studies, adoptive transfer of SMAD7-overexpressing NK cells showed superior antitumor efficacy against both pancreatic and liver cancers, and SMAD7 modification also significantly improved tumor control and prolonged survival in a chimeric antigen receptor (CAR)-NK cell therapeutic model for liver cancer. Conclusions Our findings identify SMAD7 as a key enhancer of NK-cell antitumor activity through canonical inhibition of TGF-β signaling and non-canonical activation of STAT5A transcription. Modulating SMAD7 offers a promising approach to improve NK cell-based immunotherapy.

Caloric restriction (CR) induces tumor resistance in mammals, but its mechanisms remain poorly understood. Here, we found that CR altered the proportions and gene expression profiles of tumor-infiltrating neutrophils (TINs). Depletion of neutrophils largely abrogated CR-induced tumor inhibition across multiple murine cancer models, underscoring their critical role in CR's broad anti-tumor effect. CR-induced gene expression changes in TINs were associated primarily with lipid-related processes, notably downregulating hypoxia-inducible lipid droplet-associated (HILPDA). This downregulation reduced lipid accumulation in TINs, limiting tumor growth and enhancing anti-tumor immunity by decreasing lipid transfer to tumor and immune effector cells. Upstream, CR reduced hypoxia-inducible factor 1 (HIF-1α) mRNA expression in circulating neutrophils by decreasing insulin-like growth factor 1 (IGF-1), thereby limiting HILPDA expression in TINs. Patients with lung cancer who had low baseline neutrophil HIF-1α mRNA exhibited improved responses to combined immunotherapy. These findings identify a novel neutrophil- and lipid-centered mechanism for CR-induced tumor inhibition, suggesting the IGF-1/HIF-1α/HILPDA axis as a therapeutic target.

OBJECTIVES:Phosphatase and tensin homolog (PTEN) is an essential regulator of tumor proliferation, apoptosis, and migration. However, the mechanisms by which PTEN regulates immune escape and its implications in immune checkpoint inhibitor combination therapy in oral squamous cell carcinoma (OSCC) remain unclear. METHODS:We analyzed the expression of PTEN and PD-L1 in OSCC tissues and cell lines, and their associations with clinicopathological characteristics. The role of PTEN in modulating PD-L1 expression and facilitating tumor immune evasion was investigated using western blotting and T-cell cytotoxicity assays. PTEN regulation efficacy, alone or with immune checkpoint inhibitors, was evaluated in humanized xenograft mice. RESULTS:Reduced PTEN and increased PD-L1 were strongly correlated with high clinical stage, positive lymph node metastasis, and lower CD8+ T-cell infiltration. Patients with lower PTEN, higher PD-L1, higher clinical stage, and positive lymph node metastasis experienced shorter overall survival. PTEN overexpression suppressed PD-L1 levels and promoted cytotoxic T-cell activity in OSCC cells by inhibiting PI3K/AKT signaling in vitro. Upregulating PTEN alone or combined with anti-PD-1 treatment effectively inhibited OSCC tumor progression and promoted CD8+ T-cell infiltration in tumors in vivo. CONCLUSIONS:PTEN upregulation enhances the antitumor immune response of CD8+ T-cells, suggesting a potential OSCC immunotherapy strategy.

Salivary adenoid cystic carcinoma (SACC) is a prevalent malignant tumor of the salivary glands, characterized by invasive growth and perineural invasion, resulting in high rates of local recurrence, distant metastasis and poor long-term survival. Thus, elucidating the molecular mechanisms underlying SACC invasion and identifying effective therapeutic targets are of clinical importance. Functional cellular assays including proliferation, migration, and flow cytometry, and molecular experiments, such as western blot, were conducted in vitro to explore the effects of integrin-linked kinase (ILK) knockdown on the biological behavior of SACC cells and the expression of epithelial-mesenchymal transition (EMT) markers. Transcriptome sequencing identified S100 calcium-binding protein A4 (S100A4) as a key downstream effector regulated by ILK. Additionally, 52 clinical SACC specimens were analyzed to evaluate the correlation between S100A4 expression and clinicopathological features, as well as ILK expression. Rescue experiments validated the role of S100A4 in mediating the effects of ILK. ILK knockdown significantly suppressed the malignant behavior of SACC cells, including migration and invasion, and reversed EMT phenotypes. S100A4 expression was significantly associated with clinical features such as clinical stage and perineural invasion, along with ILK expression. Overexpression of S100A4 restored Snail expression, promoted the EMT process and rescued the impaired migration and invasion capabilities of SACC cells caused by ILK knockdown. ILK may facilitate EMT-mediated invasion in SACC cells via the Glycogen synthase kinase-3 β) signaling pathway by modulating the transcription factor Snail. S100A4 may contribute to this mechanism by modulating Snail protein. These findings imply that simultaneously targeting both ILK and S100A4 represents a novel and promising therapeutic strategy to suppress SACC progression.

BACKGROUND:Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with few well-established risk factors. Emerging epidemiological evidence suggests a link between hepatitis B virus (HBV) infection and PDAC. However, the underlying mechanisms remain unclear. METHODS:High-throughput sequencing-based approach was employed to identify HBV integrations in tumour and para-tumour tissues of PDAC. The biological functions of KMT2B were evaluated in PDAC cell lines as well as in subcutaneous and orthotopic mouse models of PDAC. Chromatin immunoprecipitation sequencing and RNA sequencing were used to identify the pathway involved in PDAC development. RESULTS:HBV integration was detected in approximately one-third of HBV DNA-positive PDAC and adjacent para-tumour tissues. A total of 425 viral‒host junctions were identified, with the majority located in intergenic regions (51.29%), followed by introns (43.29%) and exons (2.35%) of the human genome. Lysine methyltransferase 2B (KMT2B, also known as MLL4), a gene frequently targeted by HBV integration in hepatocellular carcinoma, was also found to be interrupted by HBV in PDAC. KMT2B was significantly upregulated in PDAC and promoted malignant behaviours both in vitro and in vivo. Mechanistically, KMT2B exerts its oncogenic effects by regulating the downstream target gene FYN through histone H3K4 trimethylation, leading to the activation of the PI3K/Akt signalling pathway. CONCLUSION:HBV integration is a common event in HBV-related PDAC and KMT2B has been identified as a novel PDAC-related gene. KEY POINTS:Hepatitis B virus (HBV) integrates in both tumour and adjacent para-tumour tissues of pancreatic ductal adenocarcinoma (PDAC). KMT2B, a target gene of HBV integration, promotes PDAC proliferation and metastasis in vivo and in vitro experiments. KMT2B exerts its oncogenic effects by regulating the downstream target gene FYN via histone H3K4 trimethylation, activating the PI3K/Akt signalling pathway.

BACKGROUND: Lymphoid-specific helicase (HELLS), a SNF2-like chromatin-remodeling enzyme, plays a key role in tumor progression via its DNA methylation function. However, the effects of HELLS on immune infiltration and prognosis in liver hepatocellular carcinoma (LIHC) remain uncertain. METHODS: The Tumor Immune Estimation Resource (TIMER) database was employed to explore the pan-cancer mRNA expression of HELLS and its correlation with immunity. GEPIA2 was used to verify the correlation between HELLS expression and survival. The role of HELLS in cancer was explored via gene set enrichment analysis (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes) and the construction of gene-gene and protein-protein interaction networks (PPI). Additionally, correlations between DNA methylation, HELLS expression, and immune-related genes were explored in LIHC. HELLS expression in LIHC clinical samples was determined using qRT-PCR and western blotting. The effects of downregulated HELLS expression in hepatocellular carcinoma cells was explored via transfection experiments in vitro. RESULTS: High HELLS mRNA expression was identified in several cancers and was significantly associated with poorer prognosis in LIHC. Furthermore, HELLS expression was positively correlated with tumor-infiltrating lymphocytes and immune checkpoint genes in LIHC. Bioinformatics analysis suggested that DNA methylation of HELLS may be associated with the immune response. Results from the TCGA-LIHC dataset, clinical samples, and functional analysis indicated that HELLS contributed to tumor progression in LIHC. CONCLUSION: The study findings demonstrate that HELLS is an important factor in promoting LIHC malignancy and might serve as a potential biomarker for LIHC.

Pancreatic cancer (PC) is one of the most lethal malignancies characterized by a highly immunosuppressive tumor microenvironment (TME). Previously, we have reported that ubiquinol-cytochrome c reductase core protein I (UQCRC1), a key component of mitochondrial complex III, is generally upregulated in PC and produces extracellular ATP (eATP) to promote PC progression. Here, we sought to investigate whether the oncogenic property of UQCRC1 is generated through its effects on natural killer (NK) cells in the TME. We found that UQCRC1 overexpression in PC cells inhibited cytotoxicity of NK cells, as well as the infiltration of NK cells toward PC, whereas knockdown of UQCRC1 enhanced the cytotoxicity and chemotaxis of NK cells. Adoptive NK cell therapy in the subcutaneous mouse model and CIBERSORTx analysis with human PC specimens confirmed UQCRC1 elicited immunosuppressive effects on NK cells. Such UQCRC1-induced impairment of NK cells was mediated by eATP and its metabolite adenosine via P2Y11R and A2AR, respectively. Mechanistically, we found the UQCRC1/eATP axis reduced the expression of chemokine CCL5 in cancer cells and altered the balance of activating receptor DNAM-1 and inhibitory receptor CD96 on NK-92MI cells, resulting in decreased chemotaxis and exhausted phenotype of NK-92MI cells. Taken together, our study provides the evidence to support a novel mechanism by which energy metabolism change in cancer cells remodels the TME and impedes NK cell surveillance. It also suggests that targeting UQCRC1 may be a potential combined strategy for PC immunotherapy.

Background The relationship between dietary and drinking water habits and oral health are still unclear. We aimed at evaluating the association of dietary and drinking water habits with number of teeth in the elderly adults. Methods We conducted a longitudinal study based on the Chinese Longitudinal Healthy Longevity Survey from 1998 to 2018. The data of dietary and drinking water habits at baseline were collected using a questionnaire. The number of teeth at baseline and follow-up was collected for each subject. We used the linear mixed-effect model to analyze the associations of dietary habits and drinking water sources with tooth number. Results Among 19,896 participants at baseline, the mean age of the participants was 83.87 years, with the average number of natural teeth of 9.37, 8.26, 8.38, 8.68, 4.05, 1.92, 1.12, 2.20 for the first to eighth waves of survey. Compared with subjects drinking tap water, 1.036 ( 95 % CI : -1.206, -0.865), 0.880 ( 95 % CI : -1.122, -0.637) and 1.331 ( 95 % CI : -1.715, -0.947) fewer natural teeth were reported for those drinking well, surface water and spring at baseline survey. Compared with participants with rice intake as the staple food, those with wheat intake ( β = -0.684; 95 % CI : -0.865, -0.503) tended to have fewer natural teeth. Compared with participants with fresh fruit intake almost every day, those with quite often intake of fresh fruit tended to have fewer teeth with a significant dose-response trend ( P trend <0.001). Similar decreased trend for number of teeth was also indicated for increased frequency of vegetable intake ( P trend <0.001). Fewer number of teeth was found for subjects with less frequency of meat and fish intakes. Conclusions The study suggested that drinking well, surface water, and spring, intakes of wheat as staple food, as well as less frequency of fresh fruit, vegetable, meat and fish intakes were associated with significantly fewer number of teeth in the Chinese elderly population.

Evidence has indicated that lysine methyltransferase 2B (KMT2B), a major H3K4 tri-methyltransferase (H3K4me3), contributes to the development of various cancers; however, its role in cervical cancer (CC) is unclear. In this study, increased KMT2B expression was observed in human CC specimens and significantly associated with poor prognosis. The condition medium of KMT2B-overexpressing cells facilitated angiogenesis in vitro. In the subcutaneous model of human CC, KMT2B overexpression significantly promoted tumor growth and increased tumor vascular density. Meanwhile, KMT2B enhanced the migration and invasion of CC cells and promoted their metastasis to bone in a tail-vein-metastasis model. Mechanistically, the genes upregulated by KMT2B were significantly enriched in PI3K-AKT pathway. Using H3K4me3 ChIP-seq analysis, we found increased H3K4me3 level at EGF promoter region in KMT2B-overexpressing HeLa cells. ChIP-qPCR experiments not only confirmed the increased H3K4me3 level of EGF promoter but also determined that in KMT2B-overexpressing HeLa cells, KMT2B increased binding with the EGF promoter. Blocking EGFR diminished the KMT2B-induced PI3K-AKT signaling activation and CC cell migration and invasion. Moreover, EGFR inhibitors abolished the KMT2B-drived tube formation capacity of HUVECs. In conclusion, KMT2B facilitates CC metastasis and angiogenesis by upregulating EGF expression, and may serve as a new therapeutic target for CC.

Background The mechanistic basis for relapsed hepatocellular carcinoma (HCC) remains poorly understood. Recent research has highlighted the important roles of long non-coding RNAs (lncRNAs) in HCC. However, there are only a few studies on the association between lncRNAs and HCC relapse. Methods Differentially expressed lncRNAs and mRNAs between a primary HCC group and relapsed HCC group were identified using the edge R package to analyze the GSE101432 dataset. The differentially expressed lncRNAs and mRNAs were used to construct a lncRNA–mRNA co-expression network. Weighted gene co-expression network analysis followed by Gene Ontology (GO) enrichment analyses were conducted on the database. Furthermore, correlation and survival analyses were performed using The Cancer Genome Atlas database, and expression in the clinical samples was verified by qRT-PCR. Thereafter, we inputted the genes from the two groups into the HCC TNM stage and tumor grade database from TCGA. Finally, we performed Kaplan–Meier survival analysis on the lncRNAs related to relapsed HCC. Results In this study, lncRNAs and mRNAs associated with HCC relapse were identified. Two gene modules were found to be closely linked to this. The GO terms in the yellow and black modules were related to cell proliferation, differentiation, and survival, as well as some transcription-related biological processes. Through qRT-PCR, we found that the expression levels of LINC00941 and LINC00668 in relapsed HCC were higher than those in primary HCC. Further, mRNA levels of LOX, OTX1, MICB, NDUFA4L2, BAIAP2L2, and KCTD17 were changed in relapsed HCC compared to levels in primary HCC. In addition, we verified that these genes could predict the overall survival and recurrence-free survival of HCC. Moreover, we found that LINC00668 and LINC00941 could affect tumor grade and TNM stages. In total, we identified and validated two lncRNAs (LINC00941 and LINC00668) and six mRNAs (LOX, MICB, OTX1, BAIAP2L2, KCTD17, NDUFA4L2) associated with HCC relapse. Conclusion In summary, we identified the key gene modules and central genes associated with relapsed HCC and constructed lncRNA–mRNA networks related to this. These genes are likely to have potential prognostic value for relapsed HCC and might shed new light on novel biomarkers or diagnostic targets for relapsed HCC.

The ubiquitin-proteasome system (UPS) is a regulated mechanism of intracellular protein degradation and turnover, and its dysfunction is associated with various diseases including cancer. UBR5, an E3 ubiquitin ligase, is emerging as an important regulator of the UPS in cancers, but its role in pancreatic cancer is poorly understood. Here, we show that UBR5 is significantly upregulated in pancreatic cancer tissues. High UBR5 expression is correlated with increased lymph node metastasis and poor survival of patients. The loss-of-function and gain-of-function studies demonstrated that UBR5 substantially enhanced the in vitro migratory and invasive ability of pancreatic cancer cells. UBR5 knockdown also markedly inhibited in vivo cancer metastasis in the liver metastatic model of pancreatic cancer in nude mice, suggesting UBR5 as a potent metastatic promoter in pancreatic cancer. Furthermore, using co-immunoprecipitation combined with mass spectrometry analyses, CAPZA1, a member of F-actin capping protein α subunit family, was identified as a novel substrate of UBR5. UBR5 overexpression could promote the degradation of CAPZA1 via the UPS and induce the accumulation of F-actin, which has been described as an essential molecular event during the process of CAPZA1 deficiency-induced cancer cells migration and invasion. UBR5 knockdown significantly increased the intracellular level of CAPZA1 and CAPZA1 downregulation largely reversed the UBR5 knockdown-induced suppression of cell migration and invasion in pancreatic cancer cells. Collectively, our findings unveil UBR5 as a novel and critical regulator of pancreatic cancer metastasis and highlight the potential for UBR5-CAPZA1 axis as a therapeutic target for preventing metastasis in pancreatic cancer patients, especially in those with increased UBR5 expression.

[This corrects the article DOI: 10.3389/fonc.2021.634167.].

In our previous studies, programmed cell death (PCD) was induced in human periodontal ligament (PDL) cells, through activation of caspase-3 and upregulation of CASP5 gene (encoding caspase-5 protein), in response to mechanical stretch loading. The aim of this study is to explore the relationship between the inflammatory caspase, caspase-5, and the apoptotic executioner protein, caspase-3, in human PDL cells. Here, we found that cyclic stretching upregulated the activity and the protein expression level of caspase-3 and -5 and the addition of the caspase-3 inhibitor or caspase-5 inhibitor significantly inhibited the stretch-induced PCD. Meanwhile, the inhibition of caspase-5 inhibited the activation of caspase-3 and vice versa. The result of coimmunoprecipitation also demonstrated that the expression of caspase-3 was immunoprecipitated with caspase-5. Thus, our study revealed that the in vitro application of cyclic stretching induced PCD by activation of caspase-3 and -5 in human PDL cells, and these two caspases could interact with each other after mechanical stretch loading. The study may facilitate further studies on the mechanism of stretch-induced PCD and help us understand the force-related periodontal homeostasis and remodeling better.

It has been shown that cyclic stretch could induce inflammatory response such as pyroptosis and the release of IL-1β in human periodontal ligament cells, through activating inflammasome and related caspases. Though gasdermin-d (GSDMD) has been reported to be present in some inflammatory diseases and function as a crucial executioner of pyroptosis, the role of GSDMD in the stretch-induced inflammatory response in human periodontal ligament cells (HPDLCs) has not been well clarified. In this study, it was found that GSDMD was activated by cyclic stretch, and its activation affected the pyroptotic rate in HPDLCs, leading to the maturation and secretion of IL-1β and IL-18 ultimately. In addition, GSDMD was found to be regulated by caspase-1 directly. Nevertheless, the exact relationship between inflammasomes and GSDMD in the stretch-induced inflammatory response still needs to be further elucidated.

Purpose: The purpose of this meta-analysis was to evaluate the failure risk and marginal bone loss of dental implants inserted by flapless or flapped procedure. Materials and Methods: Studies were identified by searching PubMed, Web of Knowledge, and the Cochrane Library within 10 years, along with a hand search of the reference lists of the retrieved articles. Results: A total of 2717 articles were filtered after the searching strategy, and 31 studies were finally selected. Failure rate of dental implants was statistically affected by different insertion procedures (flapless or flapped) with a risk ratio (RR) of 1.70 (95% confidence interval [CI]: 1.13-2.55; P = 0.01; heterogeneity: I-2 = 0.0%; P (heterogeneity) = 0.97). Subgroup analysis indicated that in the situation of immediate/early loading, the flapless procedure showed a higher risk of implant failure comparing with flapped procedure (RR = 2.24; 95% CI: 1.05-4.78; P = 0.04; heterogeneity: I-2 = 0.0%; P (heterogeneity) = 0.91). Mean difference of marginal bone loss between the flapless group and the flapped group was -0.10 mm (95% CI: -0.18 to -0.02; P = 0.02; heterogeneity: I-2 = 82%; P (heterogeneity) = 0.00). Conclusions: This meta-analysis revealed that flapless procedure may increase the failure risk of the dental implants, especially in the situation of immediate/early loading. Nevertheless, flapless procedure showed a superiority in preserving bone tissues.

Objective To study the expression of caspases in stretch-induced apoptosis in human periodontal ligament cells (HPDLCs).Methods HPDLCs in vitro were subjected to mechanical stretch with 20％ strain for 6 h or 24 h.The apoptotic rates were analyzed by flow cytometry.The protein expression of caspase-3,-5,-7,-8 and -9 was detected by Western blotting,and the activity of caspase-3,-5,-8 and-9 was measured using colorimetric assay.Results Mechanical stretches with 20％ strain for 6 h and 24 h could induce apoptosis in HPDLCs.Compared with non-stretching control group,the protein expression level and activity of caspase-3,as well as the protein expression level of caspase-7 were up-regulated by 24 h-stretch.The protein expression level and activity of caspase-5,-8,-9 were up-regulated after stretches for 6 h and 24 h.Conclusions Mechanical stretch with 20％ strain can induce apoptosis in HPDLCs in vitro,with the activation of caspase-3,-5,-7,-8 and-9.

Objective: This study aimed to explore the mechanism of the stretch-induced cell realignment and cytoskeletal rearrangement by identifying several mechanoresponsive genes related to cytoskeletal regulators in human PDL cells.Material and methods: After the cells were stretched by 1, 10 and 20% strains for 0.5, 1, 2, 4, 6, 12 or 24 h, the changes of the morphology and content of microfilaments were recorded and calculated. Meanwhile, the expression of 84 key genes encoding cytoskeletal regulators after 6 and 24 h stretches with 20% strain was detected by using real-time PCR array. Western blot was applied to identify the protein expression level of several cytoskeletal regulators encoded by these differentially expressed genes.Results: The confocal fluorescent staining results confirmed that stretch-induced realignment of cells and rearrangement of microfilaments. Among the 84 genes screened, one gene was up-regulated while two genes were down-regulated after 6 h stretch. Meanwhile, three genes were up-regulated while two genes were down-regulated after 24 h stretch. These genes displaying differential expression included genes regulating polymerization/depolymerization of microfilaments (CDC42EP2, FNBP1L, NCK2, PIKFYVE, WASL), polymerization/depolymerization of microtubules (STMN1), interacting between microfilaments and microtubules (MACF1), as well as a phosphatase (PPP1R12B). Among the proteins encoded by these genes, the protein expression level of Cdc42 effector protein-2 (encoded by CDC42EP2) and Stathmin-1 (encoded by STMN1) was down-regulated, while the protein expression level of N-WASP (encoded by WASL) was up-regulated.Conclusion: The present study confirmed the cyclic stretch-induced cellular realignment and rearrangement of microfilaments in the human PDL cells and indicated several force-sensitive genes with regard to cytoskeletal regulators.

The aim of the study was to evaluate the effect of modifying polymethyl methacrylate (PMMA) denture base material with polyimide (PI) on its flexural property and biocompatibility. Low molecular weight (1,500 g/mol) PI was synthesized and small amount of PI (0.4, 0.6, 0.8 and 1 wt%) was dispersed into the PMMA matrix. Three-point bending tests, scanning electron microscopy and thermal cycling were used to measure the mechanical properties, while MTT assay was used to evaluate the biocompatibility of the denture base material. The results showed that 0.6% addition of PI significantly increased flexural strength of PMMA denture base material by 13.5%, compared with the control group (p<0.05). Even after 5,000 hydrothermal cycling the reinforce effect still existed. However, when the PI content further increased, flexural strength of the denture base material decreased due to particle agglomeration. The MTT assay confirmed that the addition of PI did not change the biocompatibility of the PMMA denture base material. The present study suggested that blending polyimide in the proper proportion can be a potential method to strengthen the PMMA-based denture base material.

Background and objective: As caspase-5 plays a role in apoptosis, the present study aimed to identify the expression and activation of caspase-5 in human periodontal ligament cells in response to cyclic stretch and the role of caspase-5 in stretch-induced apoptosis.Methods: Human PDL cells were exposed to 10% or 20% stretch strain for 6 or 24 h, and the mRNA and protein expressions of caspase-5 were analyzed with real-time PCR and Western blot, respectively. The caspase-5 activation was detected by colorimetric assay. Then the influence of the inhibition of caspase-5 on the stretch-induced apoptosis and caspase-3 activation were analyzed with flow cytometry and colorimetric assay, respectively.Results: Both 6 and 24 h stretches increased mRNA, protein expression and activation of caspase-5 in human PDL cells. Inhibition of caspase-5 inhibited the stretch-induced apoptosis and caspase-3 activation in human PDL cells.Conclusion: This study for the first time identified the expression and activation of caspase-5 in cyclic stretched human PDL cells and found that the stretch-induced apoptosis and caspase-3 activation were caspase-5 dependent. (C) 2016 Elsevier Ltd. All rights reserved.

BACKGROUND:Human periodontal ligament (PDL) cells underwent apoptosis after mechanical stretch loading. However, the exact signalling pathway remains unknown. This study aimed to elucidate how the apoptotic caspases functioned in the cyclic stretch-induced apoptosis in human PDL cells.MATERIALS AND METHODS:In the present study, 20% cyclic stretch was selected to load the cells for 6 or 24 h. The following parameters were analyzed: apoptotic rates, the protein levels of caspase-3, -7, -8 and -9 and the activities of caspase-8 and -9. Subsequently, the influences of caspase-8 and caspase-9 inhibitors on the apoptotic rate and the protein level of the activated caspase-3 were assessed as well.RESULTS:The apoptotic rates increased in response to cyclic stretch, but the cells entered different apoptotic stages after 6 and 24 h stretches. Caspase-3, -7, -8 and -9 were all activated after stretch loading. The stretch-induced apoptosis and the protein level of the activated caspase-3 were inhibited after inhibiting both caspase-8 and caspase-9 in both 6 and 24 h stretched cells and after inhibiting caspase-9 in 24 h stretched cells.CONCLUSION:Caspase-8 and -9 functioned differently at different apoptotic stages in human PDL cells after cyclic stretch.