An in vitro model to study mesenchymal-epithelial transformation

PLCD1-Induced DNA Damage Inhibits the Tumor Growth via Downregulating CDKs in Chondrosarcoma

Purpose

Typical genes for the treatment and diagnosis of high-grade chondrosarcoma are still in need. Our study aimed to explore the PLCD1 function in chondrosarcoma for further treatment.

Materials and Methods

Our study collected the information of 49 patients in our department. The PLCD1 expression in our cohort was detected and was compared with the TCGA database. PLCD1 knockdown and overexpression cell lines were established stably. Cell viability assay and colony formation assay were performed for cell proliferation. Flow cytometry analysis was performed for cell cycle and apoptosis. Western blotting was performed for PLCD1-related protein expression. Animal xenografts were established to verify the effect of PLCD1 in high-grade chondrosarcoma.

Results

Compared with the TCGA database, the relation between PLCD1 expression and the malignancy of chondrosarcoma was demonstrated. A lower PLCD1 expression was detected mainly in high-grade chondrosarcoma. PLCD1 overexpression in high-grade chondrosarcoma suppressed CDKs/cyclins and induced DNA damage causing cell cycle blocking and apoptosis. Antitumor effect of PLCD1 overexpression was verified in vivo.

Conclusion

Lower PLCD1 was expressed in high-grade chondrosarcoma. Overexpressed PLCD1-induced DNA damage caused cell cycle blocking and apoptosis in vitro and in vivo. PLCD1 could be a novel target in high-grade chondrosarcoma for further drug development.

Epithelioid peritoneal mesothelioma: a hybrid phenotype within a mesenchymal-epithelial/epithelial-mesenchymal transition framework

The aim of this study was to reconsider the biological characteristics of epithelioid malignant peritoneal mesothelioma (E-MpM) in the light of new concepts about epithelial mesenchymal transition and mesenchymal epithelial reverse transition (EMT/MErT) and the role of epigenetic reprogramming in this context. To this end we profiled surgical specimens and derived cells cultures by a number of complementary approaches i.e. immunohistochemistry, immunofluorescence, in situ hybridization, biochemistry, pluripotent stem cell arrays, treatments with cytokines, growth factors and specific inhibitors.The analyses of the surgical specimens showed that i) EZH2 is expressed throughout the spectrum of MpM, ii) that E-MpM (including the high-grade undifferentiated form) are characterised by c-MYC and miRNA 17-5p expression, and iii) that progression to sarcomatoid MpM is dictated by EMT regulators. They also showed that E-MpM expressed c-MET and are enriched in E- and P-cadherins- and VEGFR2-expressing CSCs, thus strongly supporting a role for MErT reprogramming in endowing E-MpM tumour cells with stemness and plasticity, and hence with a drug resistant phenotype. The cell culture-based experiments confirmed the stemness traits and plasticity of E-MpM, and support the view that EZH2 is a druggable target in this tumor.

Inhibitory Effects of Viscum coloratum Extract on IgE/Antigen-Activated Mast Cells and Mast Cell-Derived Inflammatory Mediator-Activated Chondrocytes

The accumulation and infiltration of mast cells are found in osteoarthritic lesions in humans and rodents. Nonetheless, the roles of mast cells in osteoarthritis are almost unknown. Although Viscum coloratum has various beneficial actions, its effect on allergic and osteoarthritic responses is unknown. In this study, we established an in vitro model of mast cell-mediated osteoarthritis and investigated the effect of the ethanol extract of Viscum coloratum (VEE) on IgE/antigen (IgE/Ag)-activated mast cells and mast cell-derived inflammatory mediator (MDIM)-stimulated chondrocytes. The anti-allergic effect of VEE was evaluated by degranulation, inflammatory mediators, and the FcεRI signaling cascade in IgE/Ag-activated RBL-2H3 cells. The anti-osteoarthritic action of VEE was evaluated by cell migration, and the expression, secretion, and activity of MMPs in MDIM-stimulated SW1353 cells. VEE significantly inhibited degranulation (IC₅₀: 93.04 μg/mL), the production of IL-4 (IC₅₀: 73.28 μg/mL), TNF-α (IC₅₀: 50.59 μg/mL), PGD₂ and LTC₄, and activation of the FcεRI signaling cascade in IgE/Ag-activated RBL-2H3 cells. Moreover, VEE not only reduced cell migration but also inhibited the expression, secretion, and/or activity of MMP-1, MMP-3, or MMP-13 in MDIM-stimulated SW1353 cells. In conclusion, VEE possesses both anti-allergic and anti-osteoarthritic properties. Therefore, VEE could possibly be considered a new herbal drug for anti-allergic and anti-osteoarthritic therapy. Moreover, the in vitro model may be useful for the development of anti-osteoarthritic drugs.

Suppressed invasive and migratory behaviors of SW1353 chondrosarcoma cells through the regulation of Src, Rac1 GTPase, and MMP13

Chondrosarcoma is the second frequent type of primary bone cancer. In response to stress to the endoplasmic reticulum, activation of eIF2α-mediated signaling is reported to induce apoptosis. However, its effects on invasive and migratory behaviors of chondrosarcoma have not been understood. Focusing on potential roles of Src kinase, Rac1 GTPase, and MMP13, we investigated eIF2α-driven regulation of SW1353 chondrosarcoma cells. In particular, we employed two chemical agents (salubrinal, Sal; and guanabenz, Gu) that elevate the level of eIF2α phosphorylation. The result revealed that both Sal and Gu reduced invasion and motility of SW1353 chondrosarcoma cells in a dose dependent manner. Live imaging using a fluorescent resonance energy transfer (FRET) technique showed that Sal and Gu downregulated activities of Src kinase as well as Rac1 GTPase in an eIF2α dependent manner. RNA interference experiments supported an eIF2α-mediated regulatory network in the inhibitory role of Sal and Gu. Partial silencing of MMP13 also suppressed malignant phenotypes of SW1353 chondrosarcoma cells. However, MMP13 was not regulated via eIF2α since administration of Sal but not Gu reduced expression of MMP13. In summary, we demonstrate that eIF2α dependent and independent pathways regulate invasion and motility of SW1353 chondrosarcoma cells, and inactivation of Src, Rac1, and MMP13 by Sal could provide a potential adjuvant therapy for combating metastatic chondrosarcoma cells.

The oncogene LRF is a survival factor in chondrosarcoma and contributes to tumor malignancy and drug resistance

Chondrosarcoma is a form of malignant skeletal tumor of cartilaginous origin. The non-malignant form of the disease is termed chondroma. Correctly distinguishing between the two forms is essential for making therapeutic decisions. However, due to their similar histological appearances and the lack of a reliable diagnostic marker, it is often difficult to distinguish benign tumors from low-grade chondrosarcoma. Therefore, it is necessary to search for a potential marker that has diagnostic and prognostic values in chondrosarcoma. In this study, we demonstrated by immunohistochemistry that elevated leukemia/lymphoma-related factor (LRF) expression was associated with increased malignancy in human chondrosarcoma tissue microarrays. Moreover, siRNA depletion of LRF drastically reduced proliferation of chondrosarcoma cell lines and effectively induced senescence in these cells. This could be attributed to the observation that LRF-depleted cells were arrested at the G(1) phase, and had increased p53 and p21 expression. Moreover, LRF depletion not only drastically reduces the cellular migration and invasion potentials of chondrosarcoma cells but also sensitized these cells to the apoptosis-inducing chemotherapeutic agent doxorubicin. We conclude that LRF is a survival factor in chondrosarcomas and its expression correlates with tumor malignancy and chemoresistance. Our data implicate the potential role of LRF as both a diagnostic marker and therapeutic target for chondrosarcomas.

Epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions in the colon

Epithelial-to-mesenchymal and mesenchymal-to-epithelial transitions are well established biological events which have an important role in not just normal tissue and organ development, but in the pathogenesis of diseases. Increasing evidence has established their presence in the human colon during colorectal carcinogenesis and cancer invasion, chronic inflammation-related fibrosis and in the course of mucosal healing. A large body of evidence supports the role for transforming growth factor-β and its downstream Smad signaling, the phosphatidylinositol 3'-kinase/Akt/mTOR axis, the Ras-mitogen-activated protein kinase/Snail/Slug and FOXC2 pathway, and Hedgehog signaling and microRNAs in the development of colorectal cancers via epithelial-to-mesenchymal transition. C-met and Frizzled-7, among others, seem to be the principle effectors of mesenchymal-to-epithelial transition, hence have a role not just in mucosal regeneration but in the progression of colonic wall fibrosis. Here we discuss a role for these pathways in the initiation and development of the transition events. A better understanding of their induction and regulation may lead to the identification of pathways and factors that could be potent therapeutic targets. The inhibition of epithelial-to-mesenchymal transition using mTOR kinase inhibitors targeting the ATP binding pocket and which inhibit both mTORC1 and mTORC2, RNA aptamers or peptide mimetics, such as a Wnt5A-mimetic, may all be useful in both cancer treatment and delaying fibrosis, while the induction of mesenchymal-to-epithelial transition in induced pluripotent stem cells may enhance epithelial healing in the case of severe mucosal damage. The preliminary results of the current studies are promising, but more clinical investigations are needed to develop new and safe therapeutic strategies for diseases of the colon.

Human Chondrosarcoma Cells Acquire an Epithelial-Like Gene Expression Pattern via an Epigenetic Switch: Evidence for Mesenchymal-Epithelial Transition during Sarcomagenesis

Chondrocytes are mesenchymally derived cells that reportedly acquire some epithelial characteristics; however, whether this is a progression through a mesenchymal to epithelial transition (MET) during chondrosarcoma development is still a matter of investigation. We observed that chondrosarcoma cells acquired the expression of four epithelial markers, E-cadherin,desmocollin 3, maspin, and 14-3-3σ, all of which are governed epigenetically through cytosine methylation. Indeed, loss of cytosine methylation was tightly associated with acquired expression of both maspin and 14-3-3σ in chondrosarcomas. In contrast, chondrocyte cells were negative for maspin and 14-3-3σ and displayed nearly complete DNA methylation. Robust activation of these genes was also observed in chondrocyte cells following 5-aza-dC treatment. We also examined the transcription factor snail which has been reported to be an important mediator of epithelial to mesenchymal transitions (EMTs). In chondrosarcoma cells snail is downregulated suggesting a role for loss of snail expression in lineage maintenance. Taken together, these results document an epigenetic switch associated with an MET-like phenomenon that accompanies chondrosarcoma progression.

Direct anti-cancer effect of oncostatin M on chondrosarcoma

The cytokine Oncostatin M (OSM) is cytostatic, pro-apoptotic and induces differentiation of osteosarcoma cells into osteocytes, suggesting new adjuvant treatment for these bone-forming sarcomas. However, OSM systemic over-expression could lead to adverse side effects such as generalized inflammation, neoangiogenesis and osteolysis. We determine here the effect of OSM on chondrosarcoma, another primary bone sarcoma characterized by the production of cartilage matrix and altered bone remodelling. Chondrosarcomas are resistant to conventional chemotherapy and radiotherapy, and wide surgical excision remains the only available treatment. We found that OSM blocked the cell cycle in four of five chondrosarcoma cell lines, independently of p53 and presumably through the JAK3/STAT1 pathway. In two tested cell lines, OSM induced a hypertrophic chondrocyte differentiation, with an induced Cbfa1/SOX9 ratio and induced Coll10, matrix metalloproteinase 13 (MMP13) and RANKL expression. Adenoviral gene transfer of OSM (AdOSM) in the Swarm rat chondrosarcoma (SRC) model indicated that local intra-tumoral OSM over-expression reduces chondrosarcoma development not only with reduced tumor proliferation and enhanced apoptosis but also with enhanced RANKL expression, osteoclast formation and reduced bone volumes. Flu-like symptoms were induced by the AdOSM, but there was no effect on tumor angiogenesis. Therefore, OSM could be considered as a new adjuvant anti-cancer agent for chondrosarcomas. A local application of this cytokine is presumably needed to overcome the poor vascularization of these tumors and to limit the deleterious effect on other tissues. Its side effect on bone remodeling could be managed with anti-resorption agents, thus offering potential new lines of therapeutic interventions.

Hierarchical clustering of flow cytometry data for the study of conventional central chondrosarcoma

We have investigated the use of hierarchical clustering of flow cytometry data to classify samples of conventional central chondrosarcoma, a malignant cartilage forming tumor of uncertain cellular origin, according to similarities with surface marker profiles of several known cell types. Human primary chondrosarcoma cells, articular chondrocytes, mesenchymal stem cells, fibroblasts, and a panel of tumor cell lines from chondrocytic or epithelial origin were clustered based on the expression profile of eleven surface markers. For clustering, eight hierarchical clustering algorithms, three distance metrics, as well as several approaches for data preprocessing, including multivariate outlier detection, logarithmic transformation, and z-score normalization, were systematically evaluated. By selecting clustering approaches shown to give reproducible results for cluster recovery of known cell types, primary conventional central chondrosacoma cells could be grouped in two main clusters with distinctive marker expression signatures: one group clustering together with mesenchymal stem cells (CD49b-high/CD10-low/CD221-high) and a second group clustering close to fibroblasts (CD49b-low/CD10-high/CD221-low). Hierarchical clustering also revealed substantial differences between primary conventional central chondrosarcoma cells and established chondrosarcoma cell lines, with the latter not only segregating apart from primary tumor cells and normal tissue cells, but clustering together with cell lines from epithelial lineage. Our study provides a foundation for the use of hierarchical clustering applied to flow cytometry data as a powerful tool to classify samples according to marker expression patterns, which could lead to uncover new cancer subtypes.

Molecular characterization of commonly used cell lines for bone tumor research: a trans-European EuroBoNet effort

Usage of cancer cell lines has repeatedly generated conflicting results provoked by differences among subclones or contamination with mycoplasm or other immortal mammalian cells. To overcome these limitations, we decided within the EuroBoNeT consortium to characterize a common set of cell lines including osteosarcomas (OS), Ewing sarcomas (ES), and chondrosarcomas (CS). DNA fingerprinting was used to guarantee the identity of all of the cell lines and to distinguish subclones of osteosarcoma cell line HOS. Screening for homozygous loss of 38 tumor suppressor genes by MLPA revealed deletion of CDKN2A as the most common event (15/36), strictly associated with absence of the CDKN2A (p16) protein. Ten cell lines showed missense mutations of the TP53 gene while another set of nine cell lines showed mutations resulting in truncation of the TP53 protein. Cells harboring missense mutations expressed high levels of nuclear TP53, while cell lines with nonsense mutations showed weak/absent staining for TP53. TP53(wt) cell lines usually expressed the protein in 2-10% of the cells. However, seven TP53(wt) osteosarcomas were negative for both mRNA and protein expression. Our analyses shed light on the correlation between immunohistochemical and genetic data for CDKN2A and TP53, and confirm the importance of these signaling pathways. The characterization of a substantial number of cell lines represents an important step to supply research groups with proven models for further advanced studies on tumor biology and may help to make results from different laboratories more comparable.

HOXD13 binds DNA replication origins to promote origin licensing and is inhibited by geminin

HOX DNA-binding proteins control patterning during development by regulating processes such as cell aggregation and proliferation. Recently, a possible involvement of HOX proteins in replication origin activity was suggested by results showing that a number of HOX proteins interact with the DNA replication licensing regulator geminin and bind a characterized human origin of replication. The functional significance of these observations, however, remained unclear. We show that HOXD13, HOXD11, and HOXA13 bind in vivo all characterized human replication origins tested. We furthermore show that HOXD13 interacts with the CDC6 loading factor, promotes pre-replication complex (pre-RC) proteins assembly at origins, and stimulates DNA synthesis in an in vivo replication assay. HOXD13 expression in cultured cells accelerates DNA synthesis initiation in correlation with the earlier pre-RC recruitment onto origins during G(1) phase. Geminin, which interacts with HOXD13 as well, blocks HOXD13-mediated assembly of pre-RC proteins and inhibits HOXD13-induced DNA replication. Our results uncover a function for Hox proteins in the regulation of replication origin activity and reveal an unforeseen role for the inhibition of HOX protein activity by geminin in the context of replication origin licensing.

Central chondrosarcoma progression is associated with pRb pathway alterations: CDK4 down-regulation and p16 overexpression inhibit cell growth in vitro

Chondrosarcomas are highly resistant to conventional radiation and chemotherapy, and surgical removal is the only option for curative treatment. Consequently, there is nothing to offer patients with inoperable tumours and metastatic disease. The aim of this study is to investigate genes involved in cell cycle control: CDK4, CDKN2A/p16, cyclin D1, p21, p53, MDM2 and c-MYC, which may point towards new therapeutic strategies. The pRb pathway was targeted using CDKN2A/p16 overexpressing vectors and shRNA against CDK4 in chondrosarcoma cell lines OUMS27, SW1353, and CH2879. Cell survival and proliferation were assessed. CDK4, MDM2 and c-MYC expression levels were investigated by qPCR and immunohistochemistry (IHC) in 34 fresh frozen and 90 FFPE samples of enchondroma and chondrosarcoma patients. On a subset of 29 high-grade chondrosarcomas IHC for cyclin D1, p21 and p53 was performed. The overexpression of CDKN2A/p16 and knockdown of CDK4 by shRNA in OUMS27, SW1353 and CH2879 resulted in a significant decrease in cell viability and proliferation and a decreased ability to form colonies in vitro. Expression of CDK4 and MDM2 was associated with high-grade chondrosarcoma both at the mRNA and protein level. Combining these results with the expression of cyclin D1 and the previously shown loss of CDKN2A/p16 expression show that the majority (96%; 28/29) of high-grade chondrosarcomas contain alterations in the pRb pathway. This suggests a role for the use of CDK4 inhibitors as a treatment of metastatic or inoperable high-grade chondrosarcoma.

Hoxd13 binds in vivo and regulates the expression of genes acting in key pathways for early limb and skeletal patterning

5' HoxD genes are required for the correct formation of limb skeletal elements. Hoxd13, the most 5'-located HoxD gene, is important for patterning the most distal limb region, and its mutation causes human limb malformation syndromes. The mechanisms underlying the control of developmental processes by Hoxd13, and by Hox genes in general, are still elusive, due to the limited knowledge on their direct downstream target genes. We identified by ChIP-on-chip 248 known gene loci bound invivo by Hoxd13. Genes relevant to limb patterning and skeletogenesis were further analysed. We found that Hoxd13 binds invivo, in developing limbs, the loci of Hand2, a gene crucial to limb AP axis patterning, of Meis1 and Meis2, involved in PD patterning, of the Sfrp1, Barx1, and Fbn1 genes, involved in skeletogenesis, and of the Dach1, Bmp2, Bmp4, andEmx2 genes. We show that Hoxd13 misexpression in developing chick limbs alters the expression of the majority of these genes, supporting the conclusion that Hoxd13 directly regulates their transcription. Our results indicate that 5' Hox proteins regulate directly both key genes for early limb AP and PD axis patterning and genes involved, at later stages, in skeletal patterning.

Human mesenchymal stem cell transformation is associated with a mesenchymal-epithelial transition

Carcinomas are widely thought to derive from epithelial cells with malignant progression often associated with an epithelial-mesenchymal transition (EMT). We have characterized tumors generated by spontaneously transformed human mesenchymal cells (TMC) previously obtained in our laboratory. Immunohistopathological analyses identified these tumors as poorly differentiated carcinomas, suggesting that a mesenchymal-epithelial transition (MET) was involved in the generation of TMC. This was corroborated by microarray and protein expression analysis that showed that almost all mesenchymal-related genes were severely repressed in these TMC. Interestingly, TMC also expressed embryonic antigens and were able to integrate into developing blastocysts with no signs of tumor formation, suggesting a dedifferentiation process was associated with the mesenchymal stem cell (MSC) transformation. These findings support the hypothesis that some carcinomas are derived from mesenchymal rather than from epithelial precursors.

The Effects of Histone Deacetylase Inhibitors on the Induction of Differentiation in Chondrosarcoma Cells

PURPOSE

Histologically, chondrosarcomas represent the degree of chondrogenic differentiation, which is associated with the prognosis of the disease. Histone acetylation and deacetylation play key roles in the regulation of chondrocytic differentiation. Here, we describe the antitumor effects of histone deacetylase (HDAC) inhibitors as differentiating reagents on chondrosarcomas.

EXPERIMENTAL DESIGN

We examined the effects of a HDAC inhibitor, depsipeptide, on the growth of chondrosarcoma cell lines. We also investigated the modulation of the expression levels of extracellular matrix genes and the induction of phenotypic change in chondrosarcoma cells treated with depsipeptide. Finally, we examined the antitumor effect of depsipeptide on chondrosarcoma in vivo.

RESULTS

Depsipeptide inhibited the growth of chondrosarcoma cells by inducing cell cycle arrest and/or apoptosis. HDAC inhibitors increased the expression of the alpha1 chain of type II collagen (COL2A1) gene due to the enhanced histone acetylation in the promoter and enhancer. Depsipeptide also up-regulated the expressions of aggrecan and the alpha2 chain of type XI collagen (COL11A2) mRNA in a dose-dependent manner. Moreover, long-term treatment with a low dose of depsipeptide resulted in the induction of differentiation into hypertrophic phenotype, as shown by the increment of the alpha1 chain of type X collagen (COL10A1) expression in chondrosarcoma cells. In vivo studies and histologic analyses confirmed that depsipeptide significantly inhibited tumor growth and induced differentiation into the hypertrophic and mineralized state in chondrosarcoma cells.

CONCLUSIONS

These results strongly suggest that HDAC inhibitors may be promising reagents for use as a differentiating chemotherapy against chondrosarcomas.

Antibodies differentiate desmosome-form and nucleus-form pinin: evidence that pinin is a moonlighting protein with dual location at the desmosome and within the nucleus

Pinin is a desmosome-associated protein occurring in epithelia, cardiac muscle, and meninges. This molecule was found to be capable of enhancing cell junction formation and thought to play a key role in reorganization and stabilization of the desmosome-intermediate filament complex in epithelial cells (J. Cell Biol. (1996) 135, 1027-1042). Recently a protein, claimed to be localized exclusively in the nucleus, however, with amino acid sequence identical to pinin, was reported (E. J. Cell Biol. (1998) 75, 295-298). Here I present evidence that pinin exists simultaneously at the desmosome and within the nucleus by generating location-specific monoclonal antibodies. Although the desmosome-form (d-form) and the nucleus-form (n-form) pinin share identical amino acid sequences as demonstrated by cDNA library screening and DNA sequencing, they exhibit remarkably different biochemical properties, reflecting the apparent different multiprotein nature of their differential cellular locations. In addition, the d-form pinin is characterized by a dynamic transport process which involves the gradual diminishing of nuclear materials relative to enhanced anchoring of pinin to the desmosome upon mature cells. Finally I demonstrate that pinin exists in two forms of different gene product: pinin1 and pinin2. These data argue strongly against the statement that pinin is an exclusive nuclear protein and support the notion that pinin is a moonlighting protein with more than one function as a consequence of its dual cellular location.