PDX-Derived Ewing's Sarcoma Cells Retain High Viability and Disease Phenotype in Alginate Encapsulated Spheroid Cultures

Preclinical models for the study of pediatric solid tumors: focus on bone sarcomas

Sarcomas comprise between 10-15% of all pediatric malignancies. Osteosarcoma and Ewing sarcoma are the two most common pediatric bone tumors diagnosed in children and young adults. These tumors are commonly treated with surgery and/or radiation therapy and combination chemotherapy. However, there is a strong need for the development and utilization of targeted therapeutic methods to improve patient outcomes. Towards accomplishing this goal, pre-clinical models for these unique malignancies are of particular importance to design and test experimental therapeutic strategies prior to being introduced to patients due to their origination site and propensity to metastasize. Pre-clinical models offer several advantages for the study of pediatric sarcomas with unique benefits and shortcomings dependent on the type of model. This review addresses the types of pre-clinical models available for the study of pediatric solid tumors, with special attention to the bone sarcomas osteosarcoma and Ewing sarcoma.

Application of a 3D hydrogel-based model to replace use of animals for passaging patient-derived xenografts

Purpose

This 3D in vitro cancer model for propagation of patient-derived cells, using a synthetic self-assembling peptide gel, allows the formation of a fully characterised, tailorable tumour microenvironment. Unlike many existing 3D cancer models, the peptide gel is inert, apart from molecules and motifs deliberately added or produced by cells within the model.

Methods

Breast cancer patient-derived xenografts (PDXs) were disaggregated and embedded in a peptide hydrogel. Growth was monitored by microscopic examination and at intervals, cells were extracted from the gels and passaged on into fresh gels. Passaged cells were assessed by qPCR and immunostaining techniques for the retention of characteristic markers.

Results

Breast cancer PDXs were shown to be capable of expansion over four or more passages in the peptide gel. Contaminating mouse cells were found to be rapidly removed by successive passages. The resulting human cells were shown to be compatible with a range of common assays useful for assessing survival, growth and maintenance of heterogeneity.

Conclusions

Based on these findings, the hydrogel has the potential to provide an effective and practical breast cancer model for the passage of PDXs which will have the added benefits of being relatively cheap, fully-defined and free from the use of animals or animal products. Encapsulated cells will require further validation to confirm the maintenance of cell heterogeneity, genotypes and phenotypes across passage, but with further development, including the addition of bespoke cell and matrix components of the tumour microenvironment, there is clear potential to model other cancer types.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44164-023-00048-x.

Does PARP Inhibition Sensitize Chondrosarcoma Cell Lines to Chemotherapy or Radiotherapy? Results From a Three-dimensional Spheroid Cell Model

BACKGROUND

Chondrosarcomas are well known for their resistance to conventional chemotherapy and radiotherapy treatment regimens, which is particularly detrimental in patients who have unresectable tumors. Recently, inhibition of poly(ADP-ribose) polymerase (PARP) by talazoparib was shown to sensitize chondrosarcoma cell lines to chemotherapy (temozolomide) or radiotherapy, irrespective of isocitrate dehydrogenase (IDH) mutation status. Because two-dimensionally grown cell lines have limitations and may not accurately represent the clinical response to drug treatment, we aimed to use a more representative three-dimensional alginate spheroid chondrosarcoma model. It is important to test therapeutic agents in vitro before testing them in animals or humans; therefore, we aimed to determine the effectiveness of a PARP inhibitor in reducing the viability of chondrosarcoma spheroids. Using a more stringent, complex in vitro model refines future therapeutic options for further investigation in animal models, increasing efficiency, reducing unnecessary animal use, and saving time and cost.

QUESTIONS/PURPOSES

(1) Does talazoparib treatment slow or inhibit the growth of chondrosarcoma spheroids, and does an increased treatment duration change the drug's effect? (2) Does talazoparib work in synergy with temozolomide treatment to reduce the viability of chondrosarcoma spheroids? (3) Does talazoparib work in synergy with radiotherapy treatment to reduce the viability of chondrosarcoma spheroids?

METHODS

Three representative conventional chondrosarcoma cell lines (CH2879 [IDH wildtype], JJ012 [IDH1 mutant], and SW1353 [IDH2 mutant]) were cultured as alginate spheroids and treated with talazoparib (0.001 to 10 µM), temozolomide (0.01 to 100 µM), or combinations of these drugs for 3, 7, and 14 days, representing different stages of spheroid growth. The cell lines were selected to represent a variety of IDH mutation statuses and were previously validated in spheroid culturing. Temozolomide was chosen because of its previous success when combined with PARP inhibitors, dissimilar to other commonly used chemotherapies. The effect on spheroid viability was assessed using three cell viability assays. Additionally, spheroid count, morphology, proliferation, and apoptosis were assessed. The effect of talazoparib (5 to 10 nM) combined with ƴ-radiation applied using a 137 C source (0 to 6 Gy) was assessed as surviving fractions by counting the number of spheroids (three). The therapeutic synergy of low-concentration talazoparib (5 to 10 nM) with temozolomide or radiotherapy was determined by calculating Excess over Bliss scores.

RESULTS

Talazoparib treatment reduced the spheroid viability of all three cell lines after 14 days (IC 50 ± SD of CH2879: 0.1 ± 0.03 µM, fold change: 220; JJ012: 12 ± 1.4 µM, fold change: 4.8; and SW1353: 1.0 ± 0.2 µM, fold change: 154), compared with 3-day treatments of mature spheroids. After 14 days of treatment, the Excess over Bliss scores for 100 µM temozolomide and talazoparib indicated synergistic efficacy (Excess over Bliss scores: CH2879 59% [lower 95% CI 52%], JJ012 18% [lower 95% CI 8%], and SW1353 55% [lower 95% CI 25%]) of this combination treatment. A stable synergistic effect of talazoparib and radiotherapy was present only in JJ012 spheroids at a 4Gƴ radiation dose (Excess over Bliss score: 22% [lower 95% CI 6%]).

CONCLUSION

In our study, long-term PARP inhibition was more effective than short-term treatment, and only one of the three chondrosarcoma spheroid lines was sensitive to combined PARP inhibition and radiotherapy. These findings suggest subsequent animal studies should focus on long-term PARP inhibition, and temozolomide combined with talazoparib has a higher chance of success than combination with radiotherapy.

CLINICAL RELEVANCE

Combination treatment of talazoparib and temozolomide was effective in reducing the viability of chondrosarcoma spheroids and spheroid growth, regardless of IDH mutation status, providing rationale to replicate this treatment combination in an animal chondrosarcoma model.

Characterisation of a Novel Cell Line (ICR-SS-1) Established from a Patient-Derived Xenograft of Synovial Sarcoma

Synovial sarcoma is a rare translocation-driven cancer with poor survival outcomes, particularly in the advanced setting. Previous synovial sarcoma preclinical studies have relied on a small panel of cell lines which suffer from the limitation of genomic and phenotypic drift as a result of being grown in culture for decades. Patient-derived xenografts (PDX) are a valuable tool for preclinical research as they retain many histopathological features of their originating human tumour; however, this approach is expensive, slow, and resource intensive, which hinders their utility in large-scale functional genomic and drug screens. To address some of these limitations, in this study, we have established and characterised a novel synovial sarcoma cell line, ICR-SS-1, which is derived from a PDX model and is amenable to high-throughput drug screens. We show that ICR-SS-1 grows readily in culture, retains the pathognomonic SS18::SSX1 fusion gene, and recapitulates the molecular features of human synovial sarcoma tumours as shown by proteomic profiling. Comparative analysis of drug response profiles with two other established synovial sarcoma cell lines (SYO-1 and HS-SY-II) finds that ICR-SS-1 harbours intrinsic resistance to doxorubicin and is sensitive to targeted inhibition of several oncogenic pathways including the PI3K-mTOR pathway. Collectively, our studies show that the ICR-SS-1 cell line model may be a valuable preclinical tool for studying the biology of anthracycline-resistant synovial sarcoma and identifying new salvage therapies following failure of doxorubicin.

Single-cell transcriptional profiling reveals heterogeneity and developmental trajectories of Ewing sarcoma

PURPOSE

Ewing sarcoma (EwS) is an aggressive malignant neoplasm composed of small round cells. The heterogeneity and developmental trajectories of EwS are uncertain.

METHODS

Single-cell RNA sequencing was performed on 4 EwS tumor tissue samples, and 3 transcriptional atlases were generated. K-nearest neighbor algorithm was used to predict the origin of tumor cells at single-cell resolution. Monocle2 package was used to perform pseudotime trajectory analysis in tumor cells. Differentially expressed genes were compared against those in all other clusters via the FindMarkers function, and then they were subjected to GO analysis using clusterProfiler package.

RESULTS

Combined with the results of k-nearest neighbor algorithm and pseudotime trajectory analysis in tumor cells, we thought meningeal EwS originated from neural crest cells during epithelial to mesenchymal transition and simulated the process of neural crest cell lineage differentiation. But for perirenal EwS and spinal EwS, we hypothesized that after the neural crest cell lineage mutated into them, the tumor cells did not maintain the differentiation trajectory of neural crest cell lineage, and the development trajectory of tumor cells became chaotic. GO analysis results showed that interferon signaling pathway-related biological processes play an essential role in the tumorigenesis and tumor progression process of EwS, and among these biological processes genes, JAK1 gene up-regulated most significantly and highly expressed in all tumor cells. Ruxolitinib was used to explore the function of JAK1. Targeting JAK1 can promote apoptosis of EwS tumor cells, inhibit the migration and invasion of EwS tumor cells, and inhibit cell proliferation by inducing cell cycle S phase arrest.

CONCLUSION

EwS was derived from neural crest cell lineage with variable developmental timing of oncogenic conversion, and the JAK1 might be a candidate for therapeutic targets of EwS.

Patient-Derived Breast Cancer Tissue Cultures for Anti-Endocrine Drug Assays

Breast cancer is a complex and heterogeneous pathology, characterized by a variety of histological and molecular phenotypes. The majority of the breast cancers express the estrogen receptor alpha (ER), which plays a pivotal role in the pathobiology of the disease and are therefore classified as ER-positive (ER⁺). In fact, targeting of the ER signaling pathway is the main therapeutic strategy for ER⁺ breast cancer. Despite the success of endocrine therapy, intrinsic and acquired resistance are reported in 30-50% of the ER⁺ breast cancers. However, the mechanisms underlying ER heterogeneity and therapeutic resistance are far from being fully disclosed, and efficacious clinical strategies to overcome resistance are still pending. One of the hurdles in studying ER⁺ breast cancer resistance is related with the scarcity of experimental models that can recapitulate ER heterogeneity and signaling. This is the case of ER⁺ breast cancer cell models, typically based on cells derived from metastasis, which also fail to recapitulate tumor complexity. Primary cultures of patient-derived breast cancer cells are difficult to establish, and generally characterized by stromal fibroblasts overgrowth and rapid loss of phenotypic and molecular traits of the tumor cells, including ER expression. Ex vivo cultures of breast cancer tissue have been reported to retain the tissue architecture, with preservation of the tumor microenvironment (TME) and ER expression for short periods of time.Given the cumulating evidence on the role of the TME in sustaining ER⁺ tumor cells, we hypothesized that TME preservation in culture would favor the long-term retention of ER expression and signaling. We employed alginate encapsulation to provide a supporting scaffold to breast cancer tissue microstructures, coupled to dynamic culture to improve the lifespan of the culture by avoiding diffusional limitations. In this chapter, we provide a detailed description of this culture methodology, which has been previously published by our group (Cartaxo et al., J Exp Clin Cancer Res 39:161, 2020), based on electrostatically driven breast cancer tissue encapsulation in alginate, coupled to culture under agitation in a defined culture medium. We also describe challenge of the ex vivo model with an ER activator and inhibitors (anti-endocrine drugs) and a gene expression endpoint of drug response using reverse transcription PCR-based analysis of three distinct genes downstream of ER.

In vitro three-dimensional cell cultures for bone sarcomas

Bone sarcomas are rare tumour entities that arise from the mesenchyme most of which are highly heterogeneous at the cellular, genetic and epigenetic levels. The three main types are osteosarcoma, Ewing sarcoma, and chondrosarcoma. These oncological entities are characterised by high morbidity and mortality and an absence of significant therapeutic improvement in the last four decades. In the field of oncology, in vitro cultures of cancer cells have been extensively used for drug screening unfortunately with limited success. Indeed, despite the massive knowledge acquired from conventional 2D culture methods, scientific community has been challenged by the loss of efficacy of drugs when moved to clinical trials. The recent explosion of new 3D culture methods is paving the way to more relevant in vitro models mimicking the in vivo tumour environment (e.g. bone structure) with biological responses close to the in vivo context. The present review gives a brief overview of the latest advances of the 3D culture methods used for studying primary bone sarcomas.