Deposition of onco-histone H3.3-G34W leads to DNA repair deficiency and activates cGAS/STING-mediated immune responses

Mutations in histone H3.3-encoding genes causing mutant histone tails are associated with specific cancers such as pediatric glioblastomas (H3.3-G34R/V) and giant cell tumor of the bone (H3.3-G34W). The mechanisms by which these mutations promote malignancy are not completely understood. Here we show that cells expressing H3.3-G34W exhibit DNA double-strand breaks (DSBs) repair defects and increased cellular sensitivity to ionizing radiation (IR). Mechanistically, H3.3-G34W can be deposited to damaged chromatin, but in contrast to wild-type H3.3, does not interact with non-homologous end-joining (NHEJ) key effectors KU70/80 and XRCC4 leading to NHEJ deficiency. Together with defective cell cycle checkpoints reported previously, this DNA repair deficiency in H3.3-G34W cells led to accumulation of micronuclei and cytosolic DNA following IR, which subsequently led to activation of the cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) pathway, thereby inducing release of immune-stimulatory cytokines. These findings suggest a potential for radiotherapy for tumors expressing H3.3-G34W, which can be further improved by combination with STING agonists to induce immune-mediated therapeutic efficacy.

[Corrigendum] Dexamethasone-induced inhibition of miR-132 via methylation promotes TGF-β-driven progression of pancreatic cancer

Subsequently to the publication of the above article, an interested reader drew to the authors' attention that two pairs of the culture plate images in Fig. 4A-C on p. 60 appeared to be the same, although the images were shown in different orientations; moreover, the 'NC/0 and DEX+miR132' and 'DEX and miR132' pairings of images in the scratch-wound assay experiments shown in Fig. 4B also appeared to be overlapping, such that these were apparently derived from the same original source where the results of differently performed experiments were intended to have been portrayed. After re‑examining their original data, the authors have realized that some of the data in Fig. 4A and B were inadvertently assembled incorrectly. The revised version of Fig. 4, showing all the correct data for the culture plate images in Fig. 4A-C (specifically, the images fifth along on the right for Fig. 4B and C have been revised) and the correct images for 'NC/0' and 'DEX/0' in Fig. 4D is shown on on the next page. The authors are grateful to the Editor of International Journal of Oncology for allowing them this opportunity to publish a Corrigendum, and all the authors agree with its publication. Furthermore, the authors apologize to the readership for any inconvenience caused. [International Journal of Oncology 54: 53‑64, 2019; DOI: 10.3892/ijo.2018.4616].

Selective and caspase-independent cytotoxicity of bioactive glasses towards giant cell tumor of bone derived neoplastic stromal cells but not to bone marrow derived stromal cells

Semi-malignant giant cell tumors of bone (GCTB) are associated with large osteolytic defects and significant bone destructions. Surgical resection remains the standard therapy that is, however, associated with very high recurrence rates. Bioactive glasses (BGs) that are osteogenic but under certain conditions also cytotoxic might be suitable to achieve biological reconstruction with simultaneous reduction of tumor recurrence in GCTB. In this study, a concentration and time dependent cytotoxic effect of five different BG compositions towards neoplastic GCTB cells was identified while bone marrow derived mesenchymal stromal cells were mostly unaffected. Time course and extent of the cytotoxic effect were dependent on the BG composition and were not associated with caspases activation, indicating that apoptotic mechanisms are not involved. Rather, detection of BG-induced disruption of the cell membranes and a rapid drop of intracellular HMG1 (High Mobility Group Box 1 protein) levels suggest a necrotic cell death. Notably, the cytotoxic effects were dependent on a direct contact of cells and BGs and could not be observed using indirect cultivation settings. Our data suggest that BGs might represent promising materials for the treatment of GCTB in order to reduce tumor recurrence with simultaneous enhancement of bone regeneration.

Effect of manganese, zinc, and copper on the biological and osteogenic properties of mesoporous bioactive glass nanoparticles

Mesoporous bioactive glass nanoparticles (MBGNs) have demonstrated promising properties for the local delivery of therapeutically active ions with the aim to improve their osteogenic properties. Manganese (Mn), zinc (Zn), and copper (Cu) ions have already shown promising pro-osteogenic properties. Therefore, the concentration-dependent impact of MBGNs (composition in mol%: 70 SiO₂ , 30 CaO) and MBGNs containing 5 mol% of either Mn, Zn, or Cu (composition in mol%: 70 SiO₂ , 25 CaO, 5 MnO/ZnO/CuO) on the viability and osteogenic differentiation of human marrow-derived mesenchymal stromal cells (BMSCs) was assessed in this study. Mn-doped MBGNs (5Mn-MBGNs) showed a small "therapeutic window" with a dose-dependent negative impact on cell viability but increasing pro-osteogenic features alongside increasing Mn concentrations. Due to a constant release of Zn, 5Zn-MBGNs showed good cytocompatibility and upregulated the expression of genes encoding for relevant members of the osseous extracellular matrix during the later stages of cultivation. In contrast to all other groups, BMSC viability increased with increasing concentration of Cu-doped MBGNs (5Cu-MBGNs). Furthermore, 5Cu-MBGNs induced an increase in alkaline phosphatase activity. In conclusion, doping with Mn, Zn, or Cu can enhance the biological properties of MBGNs in different ways for their potential use in bone regeneration approaches.

Globally altered epigenetic landscape and delayed osteogenic differentiation in H3.3-G34W-mutant giant cell tumor of bone

The neoplastic stromal cells of giant cell tumor of bone (GCTB) carry a mutation in H3F3A, leading to a mutant histone variant, H3.3-G34W, as a sole recurrent genetic alteration. We show that in patient-derived stromal cells H3.3-G34W is incorporated into the chromatin and associates with massive epigenetic alterations on the DNA methylation, chromatin accessibility and histone modification level, that can be partially recapitulated in an orthogonal cell line system by the introduction of H3.3-G34W. These epigenetic alterations affect mainly heterochromatic and bivalent regions and provide possible explanations for the genomic instability, as well as the osteolytic phenotype of GCTB. The mutation occurs in differentiating mesenchymal stem cells and associates with an impaired osteogenic differentiation. We propose that the observed epigenetic alterations reflect distinct differentiation stages of H3.3 WT and H3.3 MUT stromal cells and add to H3.3-G34W-associated changes.

The histone variant mutation H3.3-G34W occurs in the majority of giant cell tumor of bone (GCTB). By profiling patient-derived GCTB tumor cells, the authors show that this mutation associates with epigenetic alterations in heterochromatic and bivalent regions that contribute to an impaired osteogenic differentiation and the osteolytic phenotype of GCTB.

Retrospective analysis of 51 intralesionally treated cases with progressed giant cell tumor of the bone: local adjuvant use of hydrogen peroxide reduces the risk for tumor recurrence

BACKGROUND

Giant cell tumor of the bone (GCT) has high local recurrence rates and the prognosis is hard to predict. We therefore retrospectively analyzed clinical outcome and recurrences of 51 GCT cases focusing on the effects of adjuvant local use of hydrogen peroxide.

METHODS

The series enclosed 51 advanced GCT cases of the upper and lower extremities (n = 27 Campanacci grade III; n = 24 grade II; n = 39 surgery at our institution, n = 12 elsewhere). Mean follow-up was 88.3 (± 62.0) months. Surgical details, histology, metastases, recurrences, and interview-based data on satisfaction and function including the Musculoskeletal Tumor Society (MSTS) score were evaluated. It was investigated whether hydrogen peroxide was additionally used or not to clean the tumor cavity after curettage as we hypothesized influence on recurrences. To analyze the underlying mechanisms, GCT-derived stromal cell lines were cultured in vitro and tested for cell viability and apoptosis after treatment with hydrogen peroxide. Statistical analysis was performed with Student's t tests, analysis of variance (ANOVA) with post hoc testing, Mann-Whitney U tests, chi-square tests, Kaplan-Meier analysis, and multivariate Cox regression analysis.

RESULTS

The whole series had 21 recurrences (41%). Eleven recurrences were found (28%) after surgery at our institution. Kaplan-Meier analysis of cumulative recurrence-free survival revealed at 2 years follow-up 69% (72%, only our institution) and at 10 years follow-up 54% (68%, only our institution). Intralesional resection was performed by vigorous curettage, burring, and defect filling with either polymethylmethacrylate bone cement (n = 45) or cancellous bone from the iliac crest (n = 6). Univariate chi-square analysis showed significantly lower recurrence rate after bone cement filling (2.3-fold, p = 0.024). Cleaning of the lesion cavity with hydrogen peroxide significantly reduced recurrence rate (whole collective 2.9-fold, p = 0.004; our institution 2.8-fold, p = 0.04) and significantly increased cumulative recurrence-free survival rate (whole collective at 10 years follow-up 74% versus 31%, p = 0.002; our institution 79% versus 48%, p = 0.02) compared to cases without hydrogen peroxide treatment. In multivariate analysis, significant risk factors for recurrence were pathological fracture (hazard ratio 3.7; p = 0.04), high mitosis rate (hazard ratio 15.6; p = 0.01), and lack of hydrogen peroxide use (hazard ratio 6.0; p = 0.02). In vitro cell culture analyses found apoptotic nature of hydrogen peroxide induced GCT cell death.

CONCLUSIONS

The present series proved for the first time that additional cleaning of the tumor cavity with hydrogen peroxide before defect filling significantly reduced recurrence rate and significantly increased recurrence-free survival in advanced but intralesionally treated GCT cases.

Dexamethasone-induced inhibition of miR-132 via methylation promotes TGF-β-driven progression of pancreatic cancer

Glucocorticoids (GCs) such as dexamethasone (DEX) are administered as cancer co-treatment for palliative purposes due to their pro-apoptotic effects in lymphoid cancer and limited side effects associated with cancer growth and chemotherapy. However, there is emerging evidence that GCs induce therapy resistance in most epithelial tumors. Our recent data reveal that DEX promotes the progression of pancreatic ductal adenocarcinoma (PDA). In the present study, we examined 1 primary and 2 established PDA cell lines, and 35 PDA tissues from patients who had received (n=14) or not received (n=21) GCs prior to surgery. Through microRNA microarray analysis, in silico, and RT-qPCR analyses, we identified 268 microRNAs differentially expressed between DEX-treated and untreated cells. With a focus on cancer progression, we selected miR-132 and its target gene, transforming growth factor-β2 (TGF-β2), as top candidates. miR-132 mimics directly bound to the 3′ untranslated region (3′UTR) of a TGF-β2 luciferase construct and enhanced expression, as shown by increased luciferase activity. By contrast, DEX inhibited miR-132 expression via promoter methylation. miR-132 mimics also reduced DEX-induced clonogenicity, migration and expression of vimentin and E-cadherin in vitro and in tumor xenografts. In patients, GC intake prior to surgery enhanced global hypermethylation and expression of TGF-β2 in tissues; expression of miR-132 was detected but could not be quantified. Our results demonstrate that DEX-mediated inhibition of miR-132 is a key mediator in the progression of pancreatic cancer, and the findings provide a foundation for miRNA-based therapies.

The histone variant H3.3 G34W substitution in giant cell tumor of the bone link chromatin and RNA processing

While transcription as regulated by histones and their post-translational modifications has been well described, the function of histone variants in this process remains poorly characterized. Potentially important insight into this process pertain to the frequently occurring mutations of H3.3, leading to G34 substitutions in childhood glioblastoma and giant cell tumor of the bone (GCTB). In this study, we have established primary cell lines from GCTB patients and used them to uncover the influence of H3.3 G34W substitutions on cellular growth behavior, gene expression, and chromatin compaction. Primary cell lines with H3.3 G34W showed increased colony formation, infiltration and proliferation, known hallmarks of tumor development. Isogenic cell lines with H3.3 G34W recapitulated the increased proliferation observed in primary cells. Transcriptomic analysis of primary cells and tumor biopsies revealed slightly more downregulated gene expression, perhaps by increased chromatin compaction. We identified components related to splicing, most prominently hnRNPs, by immunoprecipitation and mass spectrometry that specifically interact with H3.3 G34W in the isogenic cell lines. RNA-sequencing analysis and hybridization-based validations further enforced splicing aberrations. Our data uncover a role for H3.3 in RNA processing and chromatin modulation that is blocked by the G34W substitution, potentially driving the tumorigenic process in GCTB.

MiR-127 and miR-376a act as tumor suppressors by in vivo targeting of COA1 and PDIA6 in giant cell tumor of bone

Giant cell tumors of bone (GCTB) are generally benign bone tumors associated with expansive osteolytic defects, a high rate of recurrence and potential malignant transformation. We recently observed silencing of miR-127-3p and miR-376a-3p in GCTB and identified COA1 and PDIA6 as their target genes. Here, we investigate the impact of these microRNAs and their target genes on tumor engraftment and progression of giant cell tumor stromal cells (GCTSC) in vivo by xenotransplantation on the chorioallantoic membrane of chicken eggs. Prior to transplantation, the neoplastic GCTSCs were transfected with miRNA mimics or siRNAs directed against their target genes. Restoration of miR-127-3p and miR-376a-3p reduced the tumor take rate to 17% and 47% compared to 95% in the controls. The tumor volumes were significantly reduced to 29% by both miRNAs. Silencing of COA1 and PDIA6 significantly decreased the tumor volumes to 37.7% and 42.7%, while the tumor take rates remained stable. Our results indicate that re-expression of miR-127-3p and miR-376a-3p induces a strong tumor suppressor effect in GCTSC, which is partially mediated via COA1 and PDIA6.

A novel model for the investigation of orthotopically growing primary and secondary bone tumours using intravital microscopy

Here is reported the development of an experimental model using intravital microscopy as a tool to orthotopically investigate malignant bone tumours. Although up to 85% of the most frequently occurring malignant solid tumours, such as lung and prostate carcinomas, metastasize into the bone, and despite the knowledge that a tumour's course may be altered by its surrounding tissue, there is no adequate experimental model available enabling the investigation of orthotopically grown bone tumours in vivo. Intravital microscopy is an internationally accepted experimental method, used in various acute and chronic animal models, that enables qualitative and quantitative analysis of the angiogenesis, microcirculation, growth behaviour, etc. of various benign and malignant tissues. Non-invasive investigations of up to several weeks are possible. Additionally, tissue samples can be taken after termination of the in vivo experiments for further ex vivo investigation (histology, immunohistochemistry, molecular biology, etc.), elucidating the mechanisms that underlie the in vivo observations. Severe combined immunodeficient mice were fitted with a cranial window preparation where the calvaria served as the site for orthotopic implantation of the solid human tumours Saos-2 osteosarcoma (primary) and A 549 lung carcinoma and PC-3 prostate carcinoma (secondary). In all preparations, the take rate was 100%. Histological assessment confirmed the data obtained in vivo, showing typical tumour growth with infiltration of the surrounding osseous and soft tissues. This novel model serves as a valuable tool in understanding the biology of primary and secondary bone tumours in physiological and pathophysiological situations, with implications for the most areas of tumour therapy such as chemotherapy, radiation and antiangiogenesis.

Elevated ratio of MMP2/MMP9 activity is associated with poor response to chemotherapy in osteosarcoma

Background

Matrix metalloproteinases (MMPs) are crucially involved in the regulation of multiple stages of cancer progression. Elevated MMP levels have been associated with the development of metastases and poor prognosis in several types of cancer. However, the role of MMPs in osteosarcoma and their prognostic value is still unclear. Available data are conflicting, most likely due to different technical approaches. We hypothesized that in contrast to total mRNA or protein levels frequently analyzed in previous studies the enzymatic activities of MMPs and their inhibitors the tissue inhibitors of matrix metalloproteinases (TIMPs) are closer related to their biological functions. We therefore aimed to evaluate the reliability of different zymography techniques for the quantification of MMP and TIMP activities in osteosarcoma biopsies in order to investigate their distribution, possible regulation and prognostic value.

Methods

All analyses were done using cryo-conserved osteosarcoma pretreatment biopsies (n = 18). Gene and protein expression of MMPs and TIMPs were analyzed by RT-qPCR and western blot analysis, respectively. Overall MMP activity was analyzed by in situ zymography, individual MMP activities were analyzed by gelatin zymography. Reverse zymography was used to detect and quantify TIMP activities.

Results

Strong overall MMP activities could be detected in osteosarcoma pretreatment biopsies with MMP2 and MMP9 as predominant active MMPs. In contrast to total RNA or protein expression MMP2 and MMP9 activities showed significant quantitative differences between good and poor responders. While MMP9 activity was high in the good responder group and significantly decreased in the poor responder group, MMP2 activity showed a reverse distribution. Likewise, significant differences were detected concerning the activity of TIMPs resulting in a negative correlation of TIMP1 activity with MMP2 activity (p = 0.044) and negative correlations of TIMP2 and TIMP3 with MMP9 activity (p = 0.007 and p = 0.006).

Conclusion

In contrast to mRNA or protein levels MMP and TIMP activities showed significant differences between the analyzed good and poor responder groups. A shift from MMP9 to predominant MMP2 activity is associated with poor response to chemotherapy suggesting that the ratio of MMP2/MMP9 activity might be a valuable and easily accessible marker to predict the response to chemotherapy in osteosarcoma.

Mesenchymal stroma cells trigger early attraction of M1 macrophages and endothelial cells into fibrin hydrogels, stimulating long bone healing without long-term engraftment

Implantation of mesenchymal stroma cells (MSCs) is an attractive approach to stimulate closure of large bone defects but an optimal carrier has yet to be defined. MSCs may display trophic and/or immunomodulatory features or stimulate bone healing by their osteogenic activity. The aim of this study was to unravel whether fibrin hydrogel supports early actions of implanted MSCs, such as host cell recruitment, immunomodulation and tissue regeneration, in long bone defects. Female rats received cell-free fibrin or male MSCs embedded in a fibrin carrier into plate-stabilized femoral bone defects. Removed callus was analyzed for host cell invasion (day 6), local cytokine expression (days 3 and 6) and persistence of male MSCs (days 3, 6, 14 and 28). Fibrin-MSC composites triggered fast attraction of host cells into the hydrogel while cell-free fibrin implants were not invaded. A migration front dominated by M1 macrophages and endothelial progenitor cells formed while M2 macrophages remained sparse. Only MSC-seeded fibrin hydrogel stimulated early tissue maturation and primitive vessel formation at day 6 in line with significantly higher VEGF mRNA levels recorded at day 3. Local TNF-α, IL-1β and IL-10 expression indicated a balanced immune cell activity independent of MSC implantation. Implanted MSCs persisted until day 14 but not day 28. Our results demonstrate that fibrin hydrogel is an attractive carrier for MSC implantation into long bone defects, supporting host cell attraction and pro-angiogenic activity. By this angiogenesis, implant integration and tissue maturation was stimulated in long bone healing independent of long-term engraftment of implanted MSCs.

Enrichment of c-Met+ tumorigenic stromal cells of giant cell tumor of bone and targeting by cabozantinib

Giant cell tumor of bone (GCTB) is a very rare tumor entity, which is little examined owing to the lack of established cell lines and mouse models and the restriction of available primary cell lines. The stromal cells of GCTB have been made responsible for the aggressive growth and metastasis, emphasizing the presence of a cancer stem cell population. To identify and target such tumor-initiating cells, stromal cells were isolated from eight freshly resected GCTB tissues. Tumorigenic properties were examined by colony and spheroid formation, differentiation, migration, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, immunohistochemistry, antibody protein array, Alu in situ hybridization, FACS analysis and xenotransplantation into fertilized chicken eggs and mice. A sub-population of the neoplastic stromal cells formed spheroids and colonies, differentiated to osteoblasts, migrated to wounded regions and expressed the metastasis marker CXC-chemokine receptor type 4, indicating self-renewal, invasion and differentiation potential. Compared with adherent-growing cells, markers for pluripotency, stemness and cancer progression, including the CSC surface marker c-Met, were enhanced in spheroidal cells. This c-Met-enriched sub-population formed xenograft tumors in fertilized chicken eggs and mice. Cabozantinib, an inhibitor of c-Met in phase II trials, eliminated CSC features with a higher therapeutic effect than standard chemotherapy. This study identifies a c-Met⁺ tumorigenic sub-population within stromal GCTB cells and suggests the c-Met inhibitor cabozantinib as a new therapeutic option for targeted elimination of unresectable or recurrent GCTB.

Rescue of silenced UCHL1 and IGFBP4 expression suppresses clonogenicity of giant cell tumor-derived stromal cells

Giant cell tumor (GCT) of bone is a generally benign tumor with a locally aggressive behavior. Histologically, GCTs consist of multinucleated giant cells, mononuclear histiocytes and the neoplastic fibroblast-like stromal cells (GCTSC). Growing evidence exists that GCTSCs develop from mesenchymal stem cells (MSCs), but little is known about the underlying molecular mechanisms. In previous studies we observed inactivation of the ubiquitin carboxyl-terminal hydrolase L1 (UCHL1) gene in primary GCTSC due to strong DNA hypermethylation, indicating that epigenetic silencing might be involved in neoplastic transformation of MSCs. Here we investigated further candidate genes and identified strong hypermethylation of the insulin-like growth factor binding protein 4 (IGFBP4) promoter, resulting in IGFBP4 downregulation in GCTs compared to MSCs. Overexpression of UCHL1 and IGFBP4 by stable transfection of GCTSC did not influence cell viability, proliferation, migration and chemosensitivity compared to parental cells. However, colony-formation was significantly decreased suggesting that rescue of UCHL1 and IFGBP4 suppresses clonogenicity of GCT stromal cells. The observation of reduced expression of the stem-cell-specific transcription factors OCT4 and SOX2 in these cell lines further supported our findings. Epigenetic silencing of UCHL1 and IGFBP4 in GCTs might thus be a crucial event during the malignant transformation of MSCs in the context of GCT development and represent promising targets for the development of new diagnostic and therapeutic strategies.

Expression of TRAIL and death receptor DR4 in Palmer type 2 TFCC lesions

INTRODUCTION

Degenerative articular disc perforations of the triangular fibrocartilage (TFC) of the wrist are characterized by fibrocartilage cell loss and are often associated with ulna-plus situations. Apoptosis has been found to play a crucial role in fibrocartilage cell loss, however, the molecular mechanism and mediators are still poorly understood.

AIM

The purpose of this study was to identify receptors to apoptosis in degenerative disc lesions.

PATIENTS

Included in the study were 17 patients with degenerative articular disc tears of the TFC (Palmer type 2C). Following arthroscopic debridement of the TFC, histological sections were examined to assess the presence of apoptosis. Apoptosis was determined using TRAIL and death receptor DR4 agonists for immunohistochemical analyses. The number of cells positive for apoptosis was then correlated with ulna length.

RESULTS

Cells positive for TRAIL and DR4 were found in all specimens. The number of cells positive for TRAIL was significantly increased in specimens of patients with an ulna positive variance (P = 0.040). However, DR4 was not significantly increased in ulna plus (P > 0.05). Both, TRAIL and DR4 positive cells were found to be evenly distributed throughout each specimen. There was no accumulation of any type of cells in any particular zone of the biopsies.

CONCLUSION

This is the first study that shows that TFCC cells express TRAIL and DR4, which suggests that apoptosis, as well as, mechanical trauma are involved in the development of disc perforation. The TRAIL/DR4 receptor system is a molecular mediator of apoptosis induction in TFC cells and therefore plays a role in cell loss in degenerative disc lesions.

Apoptotic pathways in degenerative disk lesions in the wrist

PURPOSE

Degenerative articular disk perforations of the triangular fibrocartilage (TFC) of the wrist could result from chronic loading of the ulnocarpal joint. Apoptosis played a crucial role in fibrocartilage cell loss, and the purpose of this study was to clarify which apoptotic pathway was involved in the development of degenerative disk lesions. We also investigated whether ulna length played an etiologic role in the occurrence of fibrocartilage cell loss.

METHODS

Included in the study were 17 patients with degenerative articular disk tears of the TFC (Palmer type 2C). After arthroscopic debridement of the TFC, histologic sections were examined to assess the presence of apoptosis. Apoptosis was determined by use of caspase 3, caspase 8, and caspase 9 immunohistochemistry. Furthermore, Fas ligand and BID (BH3 interacting domain death) agonist were applied for immunohistochemical analysis.

RESULTS

Cells positive for caspase 3, caspase 8, caspase 9, Fas ligand, and BID were found in all specimens. The number of cells positive for caspase 3 and BID was significantly increased in specimens from patients with an ulna-positive variance. In contrast, for cells positive for caspase 8, caspase 9, and Fas ligand, no significant difference was found between specimens from patients with an ulna-positive variance and those from patients with an ulna-neutral/ulna-negative variance.

CONCLUSIONS

The extrinsic and intrinsic apoptotic pathways are involved in the development of degenerative disk lesions. Fibrocartilage cell loss occurs mainly through the intrinsic apoptotic pathway. The accumulation of apoptotic cells is not significantly different between the 3 zones of the TFC. It could be verified that ulna length is correlated with fibrocartilage cell loss.

CLINICAL RELEVANCE

Ulnar shortening is a valuable treatment option for degenerative TFC lesions. Knowledge of the specific apoptotic pathway that is causing degenerative disk lesions is critical in selecting the appropriate and most beneficial therapeutic treatment to halt further cell loss and the degeneration of the TFC.

Survival of human mesenchymal stromal cells from bone marrow and adipose tissue after xenogenic transplantation in immunocompetent mice

INTRODUCTION

Mesenchymal stromal cells (MSC) represent an attractive cell population for tissue engineering purposes. As MSC are described as immunoprivileged, non-autologous applications seem possible. A basic requirement is the survival of MSC after transplantation in the host. The purpose of the current paper was to evaluate the survival of undifferentiated and osteogenically induced human MSC from different origins after transplantation in immunocompetent mice.

METHODS

Human MSC were isolated from bone marrow (BMSC) and adipose tissue (ASC). After cultivation on mineralized collagen, MSC were transplanted subcutaneously into immunocompetent mice (n=12). Undifferentiated MSC (group A) were compared with osteogenic-induced MSC (group B). Human-specific in situ hybridization and anti-vimentin staining was used to follow MSC after transplantation. Quantitative evaluation of lymphocytes and macrophages was performed as a measure of immunologic rejection. Unloaded scaffolds served as controls (group C). Specimens were harvested at 4 and 8 weeks.

RESULTS

Undifferentiated BMSC and ASC were detected in the majority of cases after xenogenic transplantation (group A, a total of 22 out of 24 cases), while osteogenic-induced MSC (group B) could be detected in only three of 24 cases. Quantification of lymphocytes and macrophages revealed significantly higher cell numbers in group B compared with group A (P<0.05).

DISCUSSION

Our results suggest that undifferentiated MSC are candidates for non-autologous cell transplantation, while osteogenic-induced MSC seem to be eliminated by the host's immune system. This observation seems independent of the origin of MSC and applies to BMSC and ASC.

Screening, identification, and functional analysis of three novel missense mutations in the TRADD gene in children with ALL and ALPS

BACKGROUND

Apoptosis is known to be a crucial process involved in embryogenesis, development and homeostasis of the immune system. Impaired apoptosis causes dysfunction of lymphocyte homeostasis, growth advantage of tumor cells as well as resistance to current treatment protocols. To investigate the role of the apoptosis adaptor molecules TRADD and FADD in the development of hematological diseases, patient samples were screened for mutations in these genes.

PROCEDURE

Genomic DNA from 51 children suffering from B-lineage-ALL (n = 17), T-lineage-ALL (n = 24), ALPS Type Ia (n = 3) and ALPS Type III (n = 7) were analyzed. Genomic DNA from 50 unrelated donors without hematological diseases served as controls. Identified mutations were cloned and their influence on cell viability and NFkappaB activation was analyzed by flow cytometry and luciferase assay, respectively.

RESULTS

In the FADD gene no genetic alteration could be detected. However, three novel missense mutations in the TRADD gene could be detected. They are located within a region of TRADD known to exert mainly anti-apoptotic effects for example through the activation of the NFkappaB pathway. Functional analysis of cells overexpressing mutant TRADD cDNA demonstrated a reduced NFkappaB activity and consequently increased cell death compared to wild-type TRADD.

CONCLUSION

Mutations in the TRADD gene may contribute to the development of different hematological diseases. The identified mutations demonstrate a putative impact on TRADD signaling and cell survival but may not mainly explain the pathology of the diseases investigated.

Consequences of telomerase inhibition by BIBR1532 on proliferation and chemosensitivity of chondrosarcoma cell lines

PURPOSE

Human chondrosarcomas are generally resistant to conventional treatments like chemotherapy and radiotherapy. We investigated the effects of BIBR1532, an inhibitor of telomerase on chondrosarcoma cells in vitro.

METHODS

Telomerase activity, telomere lengths, growth kinetics and chemosensitivity were analyzed in chondrosarcoma cell lines treated with BIBR1532.

RESULTS

BIBR1532 treatment resulted in telomerase inhibition, decrease of telomere length and reduction of growth capacity of telomerase positive chondrosarcoma cells. Although resistant to cisplatin, telomerase positive cells were sensitive to paclitaxel, which rapidly induced telomere erosion.

CONCLUSION

Targeting of telomeres might represent a valid strategy for the (re-)sensitization of chemoresistant chondrosarcomas.

Transplantation of mesenchymal stromal cells on mineralized collagen leads to ectopic matrix synthesis in vivo independently from prior in vitro differentiation

BACKGROUND

Tissue engineering using mesenchymal stromal cells (MSC) represents a promising approach for bone regeneration. Nevertheless, the optimal constructs have yet to be determined. It still remains unclear if there is a benefit of in vitro differentiation of MSC prior to transplantation or if undifferentiated MSC hold the optimal potential concerning new tissue formation.

METHODS

After isolation and in vitro expansion, MSC were seeded on mineralized collagen sponges and transplanted in a heterotopic SCID mice model (n=12). While group A contained undifferentiated MSC, in group B cells were cultivated for 14 days in vitro under osteogenic conditions prior to implantation. Results were compared with non-loaded scaffolds (group C). Animals were killed for investigation at 4 and at 8 weeks.

RESULTS

In situ hybridization demonstrated integration of MSC for up to 8 weeks in groups A and B. Histology revealed significantly more extracellular matrix synthesis in MSC-seeded scaffolds containing calcium phosphate and collagen type I at 4 and 8 weeks after transplantation compared with unloaded controls. At a biochemical level, higher levels of specific alkaline phosphatase expression were detected in MSC-loaded scaffolds (P<0.05). Scaffolds containing undifferentiated and differentiated MSC did not appear to differ in terms of matrix synthesis and protein expression, while the number of avital cells was significant higher in those probes loaded with differentiated MSC (P<0.01).

DISCUSSION

The integration of transplanted cells and MSC-associated matrix synthesis encourages the use of MSC-loaded mineralized collagen for tissue engineering of bone. Furthermore, our data suggest that in vitro differentiation of MSC does not have a positive influence in terms of improved matrix synthesis.

Ectopic bone formation associated with mesenchymal stem cells in a resorbable calcium deficient hydroxyapatite carrier

Bone substitute materials can induce bone formation in combination with mesenchymal stem cells (MSC). The aim of the current study was to examine ectopic in vivo bone formation with and without MSC on a new resorbable ceramic, called calcium deficient hydroxyapatite (CDHA). Ceramic blocks characterized by a large surface (48 m2/g) were compared with beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA) ceramics (both ca. 0.5 m2/g surface) and demineralized bone matrix (DBM). Before implantation in the back of SCID mice carriers were freshly loaded with 2x10(5) expanded human MSC or loaded with cells and kept under osteogenic conditions for two weeks in vitro. Culture conditions were kept free of xenogenic supplements. Deposits of osteoid at the margins of ceramic pores occurred independent of osteogenic pre-induction, contained human cells, and appeared in 416 MSC/CDHA composites compared to 216 MSC/beta-TCP composites. ALP activity was significantly higher in samples with MSC versus empty controls (p<0.001). Furthermore, ALP was significantly (p<0.05) higher for all ceramics when compared to the DBM matrix. Compared to previous studies, overall bone formation appeared to be reduced possibly due to the strict human protocol. Ectopic bone formation in the novel biomaterial CDHA varied considerably with the cell pool and was at least equal to beta-TCP blocks.

Evaluation of mineralized collagen and alpha-tricalcium phosphate as scaffolds for tissue engineering of bone using human mesenchymal stem cells

Owing to their plasticity and high proliferation capacity in vitro, mesenchymal stem cells (MSC) isolated from human bone marrow are promising candidates for use in tissue engineering approaches for the repair or replacement of mesenchymal tissues such as bone, cartilage or tendon. In keeping with the tissue engineering concept, these cells are cultivated on three-dimensional (3D) scaffolds to replace 3D tissue defects. Among the scaffolds tested for tissue engineering of bone, those containing phosphorus and calcium, as natural bone does, are the most promising candidates for this purpose. In this study, MSC from five patients were isolated from bone marrow. After in vitro expansion, cells were cultivated and differentiated towards the osteogenic lineage on mineralized collagen sponges and alpha-tricalcium phosphate (alpha-TCP). To analyze how appropriate these scaffolds would be for tissue engineering purposes, we established an in vitro characterization system to describe seeding efficiency, cell distribution and proliferation behavior on each scaffold. Real-time reverse transcriptase polymerase chain reaction quantification of important genes involved in osteogenic differentiation [e.g. bone sialoprotein (BSP), bone morphogenic protein 2, alkaline phosphatase and osteocalcin] was used to monitor the differentiation process of cells seeded on mineralized collagen and alpha-TCP. Using this in vitro characterization, we were able to demonstrate effective 3D growth of MSC on both scaffolds investigated. Improved osteogenic differentiation was observed on the scaffolds as compared to control monolayers. Of the two matrices, mineralized collagen was superior to alpha-TCP with regard to seeding efficacy (98 vs. 67%, p = 0.0003), increase in osteogenic marker genes (BSP expression on day 24, Pcollagen vs. TCP = 0.046) and 3D cell alignment (cell infiltration up to 500 vs. 200 microm). In conclusion, our data suggest that mineralized collagen is a promising candidate for use as a scaffold in tissue engineering of bone.

Telomere length and telomerase activity in the BCR-ABL-transformed murine Pro-B cell line BaF3 is unaffected by treatment with imatinib

OBJECTIVE

Imatinib mesylate is a novel tyrosine kinase inhibitor used for the treatment of Philadelphia chromosome positive (Ph+) leukemia and other malignancies. In previous studies, we found significant telomere shortening in Ph+ cells from patients with chronic myeloid leukemia (CML). Interestingly, imatinib treatment was found to lead to a normalization of previously shortened telomere length in CML patients. Based on recent reports demonstrating that c-ABL phosphorylates hTERT and thereby inhibits hTERT activity, a direct effect of imatinib on hTERT activity leading to telomere elongation in BCR-ABL-positive cells has been proposed by others. Such an effect could be of potential importance for telomere maintenance in Ph+ cells by facilitating clonal selection and progression of the disease to blast crisis.

METHODS

We investigated the impact of imatinib on telomere length and telomerase activity of the interleukin-3 (IL-3)-dependent murine pro-B cell line BaF3 and the BCR-ABL-positive, IL-3-independent transfectant BaF3p185 in vitro.

RESULTS

When BaF3 and BaF3p185 cells were treated with imatinib (the latter being rescued with IL-3), no effect on either telomerase activity or telomere length was observed. These findings can be explained by the cytoplasmatic localization of BCR-ABL found in BaF3p185 as compared to the nuclear localization of telomerase (and c-ABL).

CONCLUSION

As opposed to recent reports for c-ABL, we do not see evidence for a functional interaction between BCR-ABL and hTERT in this model system arguing against imatinib-mediated upregulation of hTERT as a crucial factor for clonal selection and disease progression of CML.

Occurrence and regional distribution of apoptosis in scoliotic discs

STUDY DESIGN

Seventy surgically obtained intervertebral discs from 9 patients with idiopathic and 7 patients with neuromuscular scoliosis were analyzed for the regional distribution of apoptosis.

OBJECTIVES

To investigate the role of apoptotic mechanisms in scoliotic discs.

SUMMARY OF BACKGROUND DATA

The reasons for the development of scoliosis are complex and yet not completely understood. In herniated lumbar disc tissue, increased apoptosis and a high expression of Fas and Fas ligand and caspase-3 activity have already been reported, suggesting a pivotal role of apoptotic mechanisms in intervertebral disc degeneration. In scoliotic discs, cell death was correlated with disc deformity and changes in nutrient supply and metabolic levels. The role of apoptosis in scoliotic discs, however, is still unclear.

METHODS

Apoptosis was determined by terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay and poly(ADP-ribose) polymerase (PARP) p85 immunohistochemistry. Expression of Fas and Fas-ligand was analyzed by immunohistochemistry and reverse transcription polymerase chain reaction analysis.

RESULTS

In all samples analyzed, apoptotic cells could be detected in the nucleus, anulus, and endplate. The number of apoptotic cells was significantly higher in the nucleus compared to the other areas and in the apex versus the nonapex discs. There was no difference between the discs of idiopathic and neuromuscular scoliosis and between the 2 age groups studied (10-17 years and 17-48 years, respectively). A strong expression of Fas and Fas-ligand could be detected in all samples.

CONCLUSION

Increased numbers of apoptotic cells in the nucleus of scoliotic discs and the apex disc suppose a pivotal role of programmed cell death for the progression of this common disorder. The simultaneous increase of Fas and Fas-ligand expression in areas with increased cell death point to an activation of the apoptotic process via the Fas/Fas-L system.

Mutation analysis of the apoptotic "death-receptors" and the adaptors TRADD and FADD/MORT-1 in osteosarcoma tumor samples and osteosarcoma cell lines

Apoptosis is a key mechanism of the organism that regulates embryogenesis and development, maintains homeostasis of the immune system and removes potentially hazardous cells. A dysregulation of apoptosis signaling may thus disturb the balance of cell survival and cell death, leading to the development of several diseases including cancer. In order to determine whether osteosarcomas display an increased frequency of genetic alterations that affect apoptosis signaling, we analyzed the death domains of the death receptor genes CD95/Fas/Apo1, TNFR1, DR3/Apo3/WSL-1/LARD/TRAMP, DR5/TRAIL-R2/TRICK2/KILLER, DR6 and the complete coding sequences of the death receptor gene DR4/TRAIL-R1 and the genes of the adaptors TRADD and FADD/MORT-1. The investigation included 15 osteosarcoma tumor samples, 3 osteosarcoma cell lines (SAOS-2, HOS and MG63) and peripheral blood from 20 donors as controls. We were able to identify 4 different sequence variations within the DR4 gene located on exons 3, 4, 5 and 10 (death-domain). No alterations have been detected in the other genes or exons investigated. Except the sequence variant affecting exon 4, the alterations were homozygous in 15% of the tumor samples and cell lines, whereas the same alterations found in the control group were heterozygous or even not detectable. Three out of 4 alterations are located in the receptor's extracellular cysteine rich domain, which contains the ligand binding area and 1 on exon 10 coding for the death-domain. They may thus exert influence on ligand-receptor interactions and subsequent apoptosis induction. Our findings suggest that homozygous genetic alterations within the DR4 gene may be implicated in the formation of osteosarcoma.

Mesenchymale Stammzellen zum Tissue Engineering von Knochen: Dreidimensionale osteogene Differenzierung auf mineralisiertem Kollagen

AIM

Due to their plasticity and high proliferation capacity in vitro, human mesenchymal stem cells (MSC) are promising candidates for substitution of mesenchymal tissues, such as bone. According to the tissue engineering concept, combinations of cells and three dimensional scaffolds are used to replace damaged tissue. Although various attempts have been made, the optimal combination of cells and artificial scaffold has not been found so far.

METHODS

In this work, human MSC were isolated from bone marrow aspirates according to standard protocols and cultivated on mineralized collagen. Osteogenic differentiation was induced by medium containing dexamethasone, ascorbic acid and beta-glycerophosphate. Cell proliferation on the scaffold (WST-1 vitality assay, total protein measurement) and osteogenic differentiation (quantitative Real-Time-RT-PCR) were monitored for 24 days.

RESULTS

Viable cells were found within the matrix throughout the cultivation period using histological and histochemical methods. Effective osteogenic differentiation could be demonstrated by the increase of expression of osteogenic marker genes (such as alkaline phosphatase) on a molecular level.

CONCLUSION

Our results make the cell/matrix construct investigated in this work a promising candidate for tissue engineering of bone using mesenchymal stem cells. This has to be tested further by in vivo analysis.

Telomere length and telomerase activity during expansion and differentiation of human mesenchymal stem cells and chondrocytes

Chondrocyte ex vivo expansion currently performed to replace damaged articular surfaces is associated with a loss of telomeric repeats similar to decades of aging in vivo. This might affect the incidence or time of onset of age-related disorders within transplanted cells or tissues. This study examined whether more immature progenitor cells, such as mesenchymal stem cells (MSC), which can be expanded and subsequently differentiated into chondrocytes is advantageous regarding telomere-length related limitations of expansion protocols. Primary chondrocytes and bone-marrow-derived MSC were isolated from 12 donors, expanded separately to 4 x 10(6) cells, and (re-)differentiated as three-dimensional chondrogenic spheroids. Cells were collected during expansion, after three-dimensional culturing and chondrogenic differentiation, and sequential analyses of telomere length and telomerase activity were performed. Surprisingly, telomeres of expanded MSC were significantly shorter than those from expanded chondrocytes from the same donor (11.4+/-2.5 vs. 13.4+/-2.2 kb) and tended to remain shorter after differentiation in chondrogenic spheroids (11.9+/-1.8 vs. 13.0+/- kb). While telomere lengths in native chondrocytes and MSC were not related to the age of the donor, significant negative correlations with age were observed in expanded (136 bp/year), three-dimensionally reconstituted (188 bp/year), and redifferentiated (229 bp/year) chondrocytes. Low levels of telomerase activity were found in MSC and chondrocytes during expansion and after (re-)differentiation to chondrogenic spheroids. In terms of replicative potential, as determined by telomere length, ex vivo expansion followed by chondrogenic differentiation of MSC did not provide a benefit compared to the expansion of adult chondrocytes. However, accelerated telomere shortening with age during expansion and redifferentiation argues for an "age phenotype" in chondrocytes as opposed to MSC and suggests an advantage for the use of MSC especially in older individuals and protocols requiring extensive expansion

Identification of drug-regulated genes in osteosarcoma cells

The introduction of systemic chemotherapy improved significantly the prognosis of osteosarcoma. Despite this success, approximately 30-40% of patients will relapse. Cytotoxic drugs have been shown to induce apoptosis in the target cells independent of their primary effects. The underlying molecular mechanisms and the intracellular mediators, however, are still largely unknown. Therefore, the purpose of our study was to identify drug-regulated genes in osteosarcoma cells useful as prognostic factors and for the development of new therapeutic strategies. Using suppressive subtractive hybridization (SSH) the gene expression pattern of untreated Saos-2 cells was compared to cells treated with cisplatin, methotrexate and doxorubicin, respectively. We identified 8 genes that are regulated >2-fold in drug-treated osteosarcoma cell lines. Expression of ferritin light chain, rhoA, inosine monophosphatdgehydrogenase II, ribonucleotide reductase M2, pro2000 and pro1859 were increased after drug treatment, whereas prohibitin and alpha-actinin expressions were significantly downregulated. Differential expression of the identified genes was verified by Northern blot analysis of 3 different osteosarcoma cell lines. In addition, the effects on chemosensitivity of 4 selected genes was analyzed by overexpression of recombinant constructs in Saos-2 cells and subsequent quantification of drug-induced apoptosis. Overexpression of prohibitin and rhoA reduced significantly drug sensitivity to approximately 52% and 59% indicating a crucial role in the modulation of drug-induced cell death.

Replicative aging of human articular chondrocytes during ex vivo expansion

OBJECTIVE

To investigate the contribution of clinical ex vivo expansion protocols to replicative aging of human chondrocytes.

METHODS

Primary human chondrocytes were cultured as monolayers after isolation from 7 articular cartilage specimens. Cells were passaged corresponding to 12-19 cell population doublings (cpd). Aliquots of the cells were collected from each passage and analyzed for telomere length and telomerase activity.

RESULTS

The rate of telomere shortening was heterogeneous, ranging from 147 to 431 bp/cpd (mean +/- SD 305 +/- 122). Telomerase activity was detected at various time points during passaging in 5 of 7 primary chondrocytes analyzed, but not in native human articular cartilage specimens. According to our data, an 8-10-fold ( approximately 3 cpd) ex vivo expansion of articular chondrocytes, as typically performed for transplantation procedures, leads to telomere erosion in the range of 900 bp. This is comparable with 30 years of aging based on the in vivo rate of telomere shortening of 30 bp/year recently found in chondrocytes.

CONCLUSION

If telomere shortening is an important determinant of aging in human articular cartilage, an additional telomere loss due to ex vivo expansion might affect the incidence or time of onset of age-related cartilage disorders. However, given the limited extent of expansion performed in the clinical setting to date, a significant telomere-mediated increase in the risk of malignant transformation or replicative exhaustion of the transplanted cells seems unlikely.

Drug-induced apoptosis in osteosarcoma cell lines is mediated by caspase activation independent of CD95-receptor/ligand interaction

Osteosarcoma is one of the most common primary malignant tumors of bone. Treatment of this tumor with systemic chemotherapy dramatically improves the prognosis, although the molecular mechanisms involved in the drug action are poorly understood. In chemosensitive leukaemic T cells and certain solid tumors, cytotoxic drugs mediate the induction of apoptosis by activation of the CD95/APO-1/Fas system. Triggering of the corresponding signaling pathway may involve CD95-receptor/ligand interaction, activation of caspases, or alterations in mitochondrial function. The purpose of our study was to determine if similar mechanisms are involved in the chemosensitivity of osteosarcomas. We found that cytotoxic drugs induce characteristic biochemical and morphological alterations related to apoptosis in osteosarcoma cell lines, including activation of caspases and disturbance of mitochondrial function. However, drug treatment did not result in activation of CD95-receptor or CD95-ligand mRNA. In addition, drug-induced apoptosis was blocked by caspase inhibitors but not by inhibition of CD95-ligand action, indicating a CD95-receptor/ligand-independent mechanism in osteosarcoma cell lines.

Modulation of resistance to anti-APO-1-induced apoptosis in osteosarcoma cells by cytokines

The CD95/APO-1 Fas receptor/ligand system plays a crucial role in growth control by mediating apoptosis in lymphoid and non-lymphoid cells. To investigate the role of CD95-mediated apoptosis in osteosarcoma, we studied 3 human osteosarcoma cell lines (HOS/TE 85, MG 63 and Saos-2) and osteoblasts derived from bone biopsies. In contrast to osteoblast-like cells, all cell lines were resistant to anti-APO-1-induced apoptosis despite constitutive CD95 expression at intermediate levels. Blocking of macromolecular synthesis by cycloheximide or actinomycin D or modulation of CD95 expression by cytokines (TNF-alpha and/or gamma-interferon) restored sensitivity to anti-APO-1-induced cell death. PCR analysis of the CD95 transcripts revealed the production of a truncated splice variant that codes for a soluble form of the CD95 receptor. Synthesis and secretion of soluble CD95 protein into the culture supernatant was demonstrated by Western blot analysis. Treatment with sensitizing cytokines led to up-regulation of full-length CD95 transcripts and the encoded membrane-bound CD95 protein but not the truncated mRNA splice variant and the corresponding soluble receptor, as shown by PCR and Western blot analysis. The biological activity of soluble CD95 secreted by osteosarcoma cells was demonstrated by the ability of osteosarcoma supernatants to protect the sensitive T-cell line Jurkat from anti-APO-1-mediated apoptosis. Our results suggest that the production of soluble CD95 by osteosarcoma cell lines that may block physiological death signals and the production of membrane-bound CD95 are differently regulated by cytokines via modulation of RNA splicing.