Characterization of a new human cell line (CH-3573) derived from a grade II chondrosarcoma with matrix production

Establishment and Characterization of a Novel Dedifferentiated Chondrosarcoma Cell Line DDCS2

Background

The dedifferentiated variant of chondrosarcoma is highly aggressive and carries an especially grim prognosis. While chemotherapeutics has failed to benefit patients with dedifferentiated chondrosarcoma significantly, preclinical chemosensitivity studies have been limited by a scarcity of available cell lines. There is, therefore, an urgent need to expand the pool of available cell lines.

Methods

We report the establishment of a novel dedifferentiated chondrosarcoma cell line DDCS2, which we isolated from the primary tumor specimen of a 60-year-old male patient. We characterized its short tandem repeat (STR) DNA profile, growth potential, antigenic markers, chemosensitivity, and oncogenic spheroid and colony-forming capacity.

Results

DDCS2 showed a spindle to polygonal shape and an approximate 60-hour doubling time. STR DNA profiling revealed a unique genomic identity not matching any existing cancer cell lines within the ATCC, JCRB, or DSMZ databases. There was no detectable contamination with another cell type. Western blot and immunofluorescence assays were consistent with a mesenchymal origin, and our MTT assay revealed relative resistance to conventional chemotherapeutics, which is typical of a dedifferentiated chondrosarcoma. Under ex vivo three-dimensional (3D) culture conditions, the DDCS2 cells produced spheroid patterns similar to the well-established CS-1 and SW1353 chondrosarcoma cell lines.

Conclusion

Our findings confirm DDCS2 is a novel model for dedifferentiated chondrosarcoma and therefore adds to the limited pool of current cell lines urgently needed to investigate the chemoresistance within this deadly cancer.

SUMOylation Is Associated with Aggressive Behavior in Chondrosarcoma of Bone

Simple Summary

SUMO is a ubiquitin-like post-translational modification important for many cellular processes and is suggested to play a role in cancer cell cycle progression. The aim of our study is to understand the role of SUMOylation in tumor progression and aggressiveness. Chondrosarcoma of bone was employed as a model to investigate if SUMOylation contributes to its aggressiveness. We confirmed that SUMO expression levels correlate with aggressiveness of chondrosarcoma and disease outcome. Inhibition of SUMOylation showed promising effects on reduction of chondrosarcoma growth in vitro. Our study implies that SUMO expression could be used as a potential biomarker for disease outcome in chondrosarcoma.

Abstract

Multiple components of the SUMOylation machinery are deregulated in various cancers and could represent potential therapeutic targets. Understanding the role of SUMOylation in tumor progression and aggressiveness would increase our insight in the role of SUMO in cancer and clarify its potential as a therapeutic target. Here we investigate SUMO in relation to conventional chondrosarcomas, which are malignant cartilage forming tumors of the bone. Aggressiveness of chondrosarcoma increases with increasing histological grade, and a multistep progression model is assumed. High-grade chondrosarcomas have acquired an increased number of genetic alterations. Using immunohistochemistry on tissue microarrays (TMA) containing 137 chondrosarcomas, we showed that higher expression of SUMO1 and SUMO2/3 correlates with increased histological grade. In addition, high SUMO2/3 expression was associated with decreased overall survival chances (p = 0. 0312) in chondrosarcoma patients as determined by log-rank analysis and Cox regression. Various chondrosarcoma cell lines (n = 7), especially those derived from dedifferentiated chondrosarcoma, were sensitive to SUMO inhibition in vitro. Mechanistically, we found that SUMO E1 inhibition interferes with cell division and as a consequence DNA bridges are frequently formed between daughter cells. In conclusion, SUMO expression could potentially serve as a prognostic biomarker.

Beyond the Influence of IDH Mutations: Exploring Epigenetic Vulnerabilities in Chondrosarcoma

Mutations in the isocitrate dehydrogenase (IDH1 or IDH2) genes are common in enchondromas and chondrosarcomas, and lead to elevated levels of the oncometabolite D-2-hydroxyglutarate causing widespread changes in the epigenetic landscape of these tumors. With the use of a DNA methylation array, we explored whether the methylome is altered upon progression from IDH mutant enchondroma towards high-grade chondrosarcoma. High-grade tumors show an overall increase in the number of highly methylated genes, indicating that remodeling of the methylome is associated with tumor progression. Therefore, an epigenetics compound screen was performed in five chondrosarcoma cell lines to therapeutically explore these underlying epigenetic vulnerabilities. Chondrosarcomas demonstrated high sensitivity to histone deacetylase (HDAC) inhibition in both 2D and 3D in vitro models, independent of the IDH mutation status or the chondrosarcoma subtype. siRNA knockdown and RNA expression data showed that chondrosarcomas rely on the expression of multiple HDACs, especially class I subtypes. Furthermore, class I HDAC inhibition sensitized chondrosarcoma to glutaminolysis and Bcl-2 family member inhibitors, suggesting that HDACs define the metabolic state and apoptotic threshold in chondrosarcoma. Taken together, HDAC inhibition may represent a promising targeted therapeutic strategy for chondrosarcoma patients, either as monotherapy or as part of combination treatment regimens.

Inhibition of PARP Sensitizes Chondrosarcoma Cell Lines to Chemo- and Radiotherapy Irrespective of the IDH1 or IDH2 Mutation Status

Chondrosarcomas are chemo- and radiotherapy resistant and frequently harbor mutations in isocitrate dehydrogenase (IDH1 or IDH2), causing increased levels of D-2-hydroxyglutarate (D-2-HG). DNA repair defects and synthetic lethality with poly(ADP-ribose) polymerase (PARP) inhibition occur in IDH mutant glioma and leukemia models. Here we evaluated DNA repair and PARP inhibition, alone or combined with chemo- or radiotherapy, in chondrosarcoma cell lines with or without endogenous IDH mutations. Chondrosarcoma cell lines treated with the PARP inhibitor talazoparib were examined for dose–response relationships, as well as underlying cell death mechanisms and DNA repair functionality. Talazoparib was combined with chemo- or radiotherapy to evaluate potential synergy. Cell lines treated long term with an inhibitor normalizing D-2-HG levels were investigated for synthetic lethality with talazoparib. We report that talazoparib sensitivity was variable and irrespective of IDH mutation status. All cell lines expressed Ataxia Telangiectasia Mutated (ATM), but a subset was impaired in poly(ADP-ribosyl)ation (PARylation) capacity, homologous recombination, and O-6-methylguanine-DNA methyltransferase (MGMT) expression. Talazoparib synergized with temozolomide or radiation, independent of IDH1 mutant inhibition. This study suggests that talazoparib combined with temozolomide or radiation are promising therapeutic strategies for chondrosarcoma, irrespective of IDH mutation status. A subset of chondrosarcomas may be deficient in nonclassical DNA repair pathways, suggesting that PARP inhibitor sensitivity is multifactorial in chondrosarcoma.

A screening-based approach identifies cell cycle regulators AURKA, CHK1 and PLK1 as targetable regulators of chondrosarcoma cell survival

Chondrosarcomas are malignant cartilage tumors that are relatively resistant towards conventional therapeutic approaches. Kinase inhibitors have been investigated and shown successful for several different cancer types. In this study we aimed at identifying kinase inhibitors that inhibit the survival of chondrosarcoma cells and thereby serve as new potential therapeutic strategies to treat chondrosarcoma patients.

An siRNA screen targeting 779 different kinases was conducted in JJ012 chondrosarcoma cells in parallel with a compound screen consisting of 273 kinase inhibitors in JJ012, SW1353 and CH2879 chondrosarcoma cell lines. AURKA, CHK1 and PLK1 were identified as most promising targets and validated further in a more comprehensive panel of chondrosarcoma cell lines. Dose response curves were performed using tyrosine kinase inhibitors: MK-5108 (AURKA), LY2603618 (CHK1) and Volasertib (PLK1) using viability assays and cell cycle analysis. Apoptosis was measured at 24 h after treatment using a caspase 3/7 assay. Finally, chondrosarcoma patient samples (N = =34) were used to examine the correlation between AURKA, CHK1 and PLK1 RNA expression and documented patient survival.

Dose dependent decreases in viability were observed in chondrosarcoma cell lines after treatment with MK-5108, LY2603618 and volasertib, with cell lines showing highest sensitivity to PLK1 inhibition. In addition increased sensitivity to conventional chemotherapy was observed after CHK1 inhibition in a subset of the cell lines. Interestingly, whereas AURKA and CHK1 were both expressed in chondrosarcoma patient samples, PLK1 expression was found to be low compared to normal cartilage. Analysis of patient samples revealed that high CHK1 RNA expression correlated with a worse overall survival.

AURKA, CHK1 and PLK1 are identified as important survival genes in chondrosarcoma cell lines. Although further research is needed to validate these findings, inhibiting CHK1 seems to be the most promising potential therapeutic target for patients with chondrosarcoma.

New Chondrosarcoma Cell Lines with Preserved Stem Cell Properties to Study the Genomic Drift During In Vitro/In Vivo Growth

For the cancer genomics era, there is a need for clinically annotated close-to-patient cell lines suitable to investigate altered pathways and serve as high-throughput drug-screening platforms. This is particularly important for drug-resistant tumors like chondrosarcoma which has few models available. Here we established and characterized new cell lines derived from two secondary (CDS06 and CDS11) and one dedifferentiated (CDS-17) chondrosarcomas as well as another line derived from a CDS-17-generated xenograft (T-CDS17). These lines displayed cancer stem cell-related and invasive features and were able to initiate subcutaneous and/or orthotopic animal models. Different mutations in Isocitrate Dehydrogenase-1 (IDH1), Isocitrate Dehydrogenase-2 (IDH2), and Tumor Supressor P53 (TP53) and deletion of Cyclin Dependent Kinase Inhibitor 2A (CDKN2A) were detected both in cell lines and tumor samples. In addition, other mutations in TP53 and the amplification of Mouse Double Minute 2 homolog (MDM2) arose during cell culture in CDS17 cells. Whole exome sequencing analysis of CDS17, T-CDS17, and matched patient samples confirmed that cell lines kept the most relevant mutations of the tumor, uncovered new mutations and revealed structural variants that emerged during in vitro/in vivo growth. Altogether, this work expanded the panel of clinically and genetically-annotated chondrosarcoma lines amenable for in vivo studies and cancer stem cell (CSC) characterization. Moreover, it provided clues of the genetic drift of chondrosarcoma cells during the adaptation to grow conditions.

Bcl-xl as the most promising Bcl-2 family member in targeted treatment of chondrosarcoma

Chondrosarcomas are malignant cartilage tumors showing relative resistance to conventional chemo- and radiotherapy. Previous studies showed that chondrosarcoma cells could be sensitized to chemotherapy by inhibiting the Bcl-2 family members Bcl-2, Bcl-xl and Bcl-w using ABT-737. In this study we explored the specific role of Bcl-2 family members to identify the most important player in chondrosarcoma cell survival and chemo resistance. Immunohistochemistry was performed on tissue microarrays containing 137 conventional chondrosarcomas of different grades. Selective inhibition of Bcl-2 (S55746) or Bcl-xl (WEHI-539 or A-1155463) and the combination with doxorubicin or cisplatin was investigated in a panel of 8 chondrosarcoma cell lines using presto blue viability assays and caspase 3/7 glo apoptosis assays. In addition Bcl-2 and Bcl-xl inhibition was investigated in an orthotopic Swarm Rat Chondrosarcoma (SRC) model. Bcl-2 and Bcl-xl were most abundantly expressed in the primary tumors, and expression increased with increasing histological grade. A subset of chondrosarcoma cell lines was sensitive to selective inhibition of Bcl-xl, and synergy was observed with doxorubicin or cisplatin in 3 out of 8 chondrosarcoma cell lines resulting in apoptosis. Conversely, selective inhibition of Bcl-2 was not effective in chondrosarcoma cell lines and could not sensitize to chemotherapy. In vivo, selective inhibition of Bcl-xl, but not Bcl-2 resulted in a decrease in tumor growth rate, even though no sensitization to doxorubicin was observed. These results suggest that among the Bcl-2 family members, Bcl-xl is most important for chondrosarcoma survival. Further research is needed to validate whether single or combination treatment with chemotherapy will be beneficial for chondrosarcoma patients.

Targeting glutaminolysis in chondrosarcoma in context of the IDH1/2 mutation

INTRODUCTION

Chondrosarcoma is a malignant cartilage-forming bone tumour in which mutations in IDH1 and IDH2 frequently occur. Previous studies suggest an increased dependency on glutaminolysis in IDH1/2 mutant cells, which resulted in clinical trials with the drugs CB-839, metformin and chloroquine. In this study, the preclinical rationale for using these drugs as a treatment for chondrosarcoma was evaluated.

METHODS

Expression of glutaminase was determined in 120 cartilage tumours by immunohistochemistry. Ten chondrosarcoma cell lines were treated with the metabolic compounds CB-849, metformin, phenformin (lipophilic analogue of metformin) and chloroquine.

RESULTS

A difference in glutaminase expression levels between the different tumour grades (p = 0.001, one-way ANOVA) was identified, with the highest expression observed in high-grade chondrosarcomas. Treatment with CB-839, metformin, phenformin or chloroquine revealed that chondrosarcoma cell lines are sensitive to glutaminolysis inhibition. Metformin and phenformin decreased mTOR activity in chondrosarcoma cells, and metformin decreased LC3B-II levels, which is counteracted by chloroquine.

CONCLUSION

Targeting glutaminolysis with CB-839, metformin, phenformin or chloroquine is a potential therapeutic strategy for a subset of high-grade chondrosarcomas, irrespective of the presence or absence of an IDH1/2 mutation.

NAD Synthesis Pathway Interference Is a Viable Therapeutic Strategy for Chondrosarcoma

Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinic acid phosphoribosyltransferase (NAPRT) are rate-limiting enzymes in the NAD⁺ synthesis pathway. Chondrosarcoma is a malignant cartilage forming bone tumor, in which mutations altering isocitrate dehydrogenase-1 and -2 (IDH1 and IDH2) activity have been identified as potential driver mutations. Vulnerability for NAD⁺ depletion has been reported for IDH1/2-mutant cells. Here, the potency of NAMPT inhibitors as a treatment of chondrosarcoma was explored. Eleven chondrosarcoma cell lines were treated with NAMPT inhibitors, in which the effect on cell viability, colony formation, and 3D collagen invasion was assessed. The expression level of NAMPT and NAPRT transcripts in chondrosarcoma cells was determined by qRT-PCR. Methylation of the NAPRT promoter was evaluated using a previously published dataset of genome-wide methylation. In addition, a methylation dataset was used to determine methylation of the NAPRT promoter in 20 IDH1/2-mutated cartilage tumors. Chondrosarcoma cells showed a dose-dependent decrease in cell viability, 3D collagen invasion, and colony formation upon treatment with NAMPT inhibitors, in which nearly half of the cell lines demonstrated absolute IC₅₀s in the low nanomolar range. Increasing IC₅₀s correlated to increasing NAPRT expression levels and decreasing NAPRT promoter methylation. No correlation between IDH1/2 mutation status and sensitivity for NAMPT inhibitors was observed. Strikingly, higher methylation of the NAPRT promoter was observed in high-grade versus low-grade chondrosarcomas. In conclusion, this study identified NAMPT as a potential target for treatment of chondrosarcoma.Implications: Chondrosarcoma patients, especially those of high histologic grade with lower expression and hypermethylation of NAPRT, may benefit from inhibition of the NAD synthesis pathway. Mol Cancer Res; 15(12); 1714-21. ©2017 AACR.

No preclinical rationale for IGF1R directed therapy in chondrosarcoma of bone

Background

Chondrosarcoma is a malignant cartilage forming bone tumour for which no effective systemic treatment is available. Previous studies illustrate the need for a better understanding of the role of the IGF pathway in chondrosarcoma to determine if it can be a target for therapy, which was therefore explored in this study.

Methods

Expression of mediators of IGF1R signalling and phosphorylation status of IRS1 was determined in chondrosarcoma cell lines by qRT-PCR and western blot. The effect of activation and inhibition of IGF1R signalling on downstream targets was assessed by western blot. Ten chondrosarcoma cell lines were treated with OSI-906 (IGF1R and IR dual inhibitor) after which cell proliferation and migration were determined by a viability assay and the xCELLigence system, respectively. In addition, four chondrosarcoma cell lines were treated with a combination of doxorubicin and OSI-906. By immunohistochemistry, IGF1R expression levels were determined in tissue microarrays of 187 cartilage tumours and ten paraffin embedded cell lines.

Results

Mediators of IGF1R signalling are heterogeneously expressed and phosphorylated IRS1 was detected in 67 % of the tested chondrosarcoma cell lines, suggesting that IGF1R signalling is active in a subset of chondrosarcoma cell lines. In the cell lines with phosphorylated IRS1, inhibition of IGF1R signalling decreased phosphorylated Akt levels and increased IGF1R expression, but it did not influence MAPK or S6 activity. In line with these findings, treatment with IGF1R/IR inhibitors did not impact proliferation or migration in any of the chondrosarcoma cell lines, even upon stimulation with IGF1. Although synergistic effects of IGF1R/IR inhibition with doxorubicin are described for other cancers, our results demonstrate that this was not the case for chondrosarcoma. In addition, we found minimal IGF1R expression in primary tumours in contrast to the high expression detected in chondrosarcoma cell lines, even if both were derived from the same tumour, suggesting that in vitro culturing upregulates IGF1R expression.

Conclusions

The results from this study indicate that the IGF pathway is not essential for chondrosarcoma growth, migration or chemoresistance. Furthermore, IGF1R is only minimally expressed in chondrosarcoma primary tumours. Therefore, the IGF pathway is not expected to be an effective therapeutic target for chondrosarcoma of bone.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2522-8) contains supplementary material, which is available to authorized users.

Targeting survivin as a potential new treatment for chondrosarcoma of bone

Chondrosarcomas are malignant cartilage-forming bone tumors, which are intrinsically resistant to chemo- and radiotherapy, leaving surgical removal as the only curative treatment option. Therefore, our aim was to identify genes involved in chondrosarcoma cell survival that could serve as a target for therapy. siRNA screening for 51 apoptosis-related genes in JJ012 chondrosarcoma cells identified BIRC5, encoding survivin, as essential for chondrosarcoma survival. Using immunohistochemistry, nuclear as well as cytoplasmic survivin expression was analyzed in 207 chondrosarcomas of different subtypes. Nuclear survivin has been implicated in cell-cycle regulation while cytoplasmic localization is important for its anti-apoptotic function. RT-PCR was performed to determine expression of the most common survivin isoforms. Sensitivity to YM155, a survivin inhibitor currently in phase I/II clinical trial for other tumors, was examined in 10 chondrosarcoma cell lines using viability assay, apoptosis assay and cell-cycle analysis. Survivin expression was found in all chondrosarcoma patient samples. Higher expression of nuclear and cytoplasmic survivin was observed with increasing histological grade in central chondrosarcomas. Inhibition of survivin using YM155 showed that especially TP53 mutant cell lines were sensitive, but no caspase 3/7 or PARP cleavage was observed. Rather, YM155 treatment resulted in a block in S phase in two out of three chondrosarcoma cell lines, indicating that survivin is more involved in cell-cycle regulation than in apoptosis. Thus, survivin is important for chondrosarcoma survival and chondrosarcoma patients might benefit from survivin inhibition using YM155, for which TP53 mutational status can serve as a predictive biomarker.

An orthotopic mouse model for chondrosarcoma of bone provides an in vivo tool for drug testing

Chondrosarcoma is a malignant cartilaginous tumor of the bone. Recently, mutations in isocitrate dehydrogenase-1 (IDH1) and isocitrate dehydrogenase-2 (IDH2) were identified in central chondrosarcomas. As chondrosarcomas are notoriously resistant to conventional treatment modalities, the need for model systems to screen new treatment options is high. We used two chondrosarcoma cell lines (CH2879 and SW1353) to generate a bioluminescent orthotopic chondrosarcoma mouse model. Cell lines were stably transduced with a lentiviral luciferase expression vector, and after clonal selection, luciferase-expressing clones were subcutaneously and orthotopically implanted in nude mice. Mice injected with CH2879 cells were treated with doxorubicin over a period of 6 weeks. Both cell lines resulted in tumor growth. CH2879 tumors were consistently larger than SW1353 tumors. No difference in size could be observed between subcutaneous and orthotopic tumors. Tumor growth could be monitored over time through assessment of luciferase activity, without harming the mice. Using this model, we show that doxorubicin does not have a significant effect on in vivo tumor growth. We describe an orthotopic chondrosarcoma mouse model that can be used to test new treatment strategies evolving from in vitro research.

New chondrosarcoma cell lines and mouse models to study the link between chondrogenesis and chemoresistance

Chondrosarcomas are cartilage-forming, poorly vascularized tumors. They represent the second malignant primary bone tumor of adults after osteosarcoma, but in contrast to osteosarcoma they are resistant to chemotherapy and radiotherapy, surgical excision remaining the only therapeutic option. Few cell lines and animal models are available, and the mechanisms behind their chemoresistance remain largely unknown. Our goal was to establish new cell lines and animal cancer models from human chondrosarcoma biopsies to study their chemoresistance. Between 2007 and 2012, 10 chondrosarcoma biopsies were collected and used for cell culture and transplantation into nude mice. Only one transplanted biopsy and one injected cell line has engrafted successfully leading to conventional central high-grade chondrosarcoma similar to the original biopsies. In culture, two new stable cell lines were obtained, one from a dedifferentiated and one from a grade III conventional central chondrosarcoma biopsy. Their genetic characterization revealed triploid karyotypes, mutations in IDH1, IDH2, and TP53, deletion in CDKN2A and/or MDM2 amplification. These cell lines expressed mesenchymal membrane markers (CD44, 73, 90, 105) and were able to produce a hyaline cartilaginous matrix when cultured in chondrogenic three-dimensional (3D) pellets. Using a high-throughput quantitative RT-PCR approach, we observed that cell lines cultured in monolayer had lost expression of several genes implicated in cartilage development (COL2A1, COMP, ACAN) but restored their expression in 3D cultures. Chondrosarcoma cells in monolayer were sensitive to several conventional chemotherapeutic agents but became resistant to low doses of mafosfamide or doxorubicin when cultured in 3D pellets, in parallel with an altered nucleic accumulation of the drug. Our results indicate that the cartilaginous matrix produced by chondrosarcoma cells may impair diffusion of several drugs and thus contribute to chemoresistance. Therefore, 3D chondrogenic cell pellets constitute a more relevant model to study chondrosarcoma chemoresistance and may be a valuable alternative to animal experimentations.

Three new chondrosarcoma cell lines: one grade III conventional central chondrosarcoma and two dedifferentiated chondrosarcomas of bone

Background

Chondrosarcoma is the second most common primary sarcoma of bone. High-grade conventional chondrosarcoma and dedifferentiated chondrosarcoma have a poor outcome. In pre-clinical research aiming at the identification of novel treatment targets, the need for representative cell lines and model systems is high, but availability is scarce.

Methods

We developed and characterized three cell lines, derived from conventional grade III chondrosarcoma (L835), and dedifferentiated chondrosarcoma (L2975 and L3252) of bone. Proliferation and migration were studied and we used COBRA-FISH and array-CGH for karyotyping and genotyping. Immunohistochemistry for p16 and p53 was performed as well as TP53 and IDH mutation analysis. Cells were injected into nude mice to establish their tumorigenic potential.

Results

We show that the three cell lines have distinct migrative properties, L2975 had the highest migration rate and showed tumorigenic potential in mice. All cell lines showed chromosomal rearrangements with complex karyotypes and genotypic aberrations were conserved throughout late passaging of the cell lines. All cell lines showed loss of CDKN2A, while TP53 was wild type for exons 5–8. L835 has an IDH1 R132C mutation, L2975 an IDH2 R172W mutation and L3252 is IDH wild type.

Conclusions

Based on the stable culturing properties of these cell lines and their genotypic profile resembling the original tumors, these cell lines should provide useful functional models to further characterize chondrosarcoma and to evaluate new treatment strategies.