Establishment of a novel human CIC-DUX4 sarcoma cell line, Kitra-SRS, with autocrine IGF-1R activation and metastatic potential to the lungs

Molecular and therapeutic advancements in Capicua (CIC)-rearranged sarcoma

Capicua (CIC)-rearranged sarcomas are an aggressive subset of undifferentiated round cell sarcomas. CIC::DUX4, the proto-typical CIC fusion oncoprotein is associated with rapid clinical progression and chemotherapy resistance leading to poor clinical outcomes. Recent studies have identified additional CIC fusions (CIC::NUTM1, CIC::FOXO4, and CIC::LEUTX) that largely retain CIC-binding specificity but leverage C-terminal binding partners (NUTM1, FOXO4, and LEUTX) to potentially activate transcriptional programs that drive oncogenesis. Moreover, the recent development of preclinical models to study CIC::DUX4 sarcoma have advanced our understanding of the underlying biological mechanisms and uncovered key dependencies that can be translated into rational therapies. In this review, we will highlight these recent advancements in CIC-rearranged sarcoma biology with a vision for clinical translation to improve patient outcomes.

CIC-Rearranged Sarcoma

CIC-rearranged sarcoma is a rare type of small round cell sarcoma. The tumors often affect the deep soft tissues of patients in a wide age range. They are highly aggressive, respond poorly to chemotherapy, and have a worse outcome than Ewing sarcoma. CIC-rearranged sarcoma has characteristic and recognizable histology, including lobulated growth, focal myxoid changes, round to epithelioid cells, and minimal variation of nuclear size and shape. Nuclear ETV4 and WT1 expression are useful immunohistochemical findings. CIC fusion can be demonstrated using various methods; however, even next-generation sequencing suffers from imperfect sensitivity, especially for CIC::DUX4.

Studies on the effect and mechanism of CD147 on melanoma stem cells

BACKGROUND

Melanoma is the most aggressive form of skin cancer. Melanoma stem cells (MSCs) are one of the driving forces of melanoma invasion and metastasis. Therefore, it is of great significance to explore the mechanisms that maintain the stemness of MSCs. In this study, CD147-positive (CD147+) MSCs derived from A375 cell line were characterized.

METHODS

Side population (SP) and non-SP cells were sorted from A375 cells. Quantitative real-time polymerase chain reaction and Western blot analysis were conducted to determine the expression of CD147 in SP and non-SP cells. Subsequently, CD147+ and CD147-negative (CD147-) cells were isolated from SP cells. Stem cell characteristics and metastatic potential of CD147+/- antigen-presenting cells were identified by sphere-forming, wound-healing, and transwell assays. Western blot analysis was performed to evaluate the protein levels of transforming growth factor-beta1 (TGFβ1) and neurogenic locus notch homolog protein 1 (Notch1) signaling pathway. Xenograft tumor experiments were conducted to investigate the tumorigenic capacity of CD147+ cells in vivo.

RESULTS

CD147 was highly expressed in SP cells of A375 cell line. CD147+ cells have stronger abilities for sphere forming, migration, and invasion in vitro. The protein levels of TGFβ1, notch1, jagged1, and Hes1 were higher in CD147+ cells than in CD147- cells. Moreover, the CD147+ cells showed stronger tumorigenic and metastatic potential in vivo.

CONCLUSION

SP cells of A375 cell line expressed high levels of CD147, and CD147+ SP cells possessed much stronger stem-like characteristics and motility, which is linked to the activation of TGFβ and notch pathways.

Human DUX4 and mouse Dux interact with STAT1 and broadly inhibit interferon-stimulated gene induction

DUX4 activates the first wave of zygotic gene expression in the early embryo. Mis-expression of DUX4 in skeletal muscle causes facioscapulohumeral dystrophy (FSHD), whereas expression in cancers suppresses IFNγ induction of major histocompatibility complex class I (MHC class I) and contributes to immune evasion. We show that the DUX4 protein interacts with STAT1 and broadly suppresses expression of IFNγ-stimulated genes by decreasing bound STAT1 and Pol-II recruitment. Transcriptional suppression of interferon-stimulated genes (ISGs) requires conserved (L)LxxL(L) motifs in the carboxyterminal region of DUX4 and phosphorylation of STAT1 Y701 enhances interaction with DUX4. Consistent with these findings, expression of endogenous DUX4 in FSHD muscle cells and the CIC-DUX4 fusion containing the DUX4 CTD in a sarcoma cell line inhibit IFNγ induction of ISGs. Mouse Dux similarly interacted with STAT1 and suppressed IFNγ induction of ISGs. These findings identify an evolved role of the DUXC family in modulating immune signaling pathways with implications for development, cancers, and FSHD.

Small round cell sarcomas

Undifferentiated small round cell sarcomas (SRCSs) of bone and soft tissue comprise a heterogeneous group of highly aggressive tumours associated with a poor prognosis, especially in metastatic disease. SRCS entities mainly occur in the third decade of life and can exhibit striking disparities regarding preferentially affected sex and tumour localization. SRCSs comprise new entities defined by specific genetic abnormalities, namely EWSR1-non-ETS fusions, CIC-rearrangements or BCOR genetic alterations, as well as EWSR1-ETS fusions in the prototypic SRCS Ewing sarcoma. These gene fusions mainly encode aberrant oncogenic transcription factors that massively rewire the transcriptome and epigenome of the as yet unknown cell or cells of origin. Additional mutations or copy number variants are rare at diagnosis and, depending on the tumour entity, may involve TP53, CDKN2A and others. Histologically, these lesions consist of small round cells expressing variable levels of CD99 and specific marker proteins, including cyclin B3, ETV4, WT1, NKX3-1 and aggrecan, depending on the entity. Besides locoregional treatment that should follow standard protocols for sarcoma management, (neo)adjuvant treatment is as yet ill-defined but generally follows that of Ewing sarcoma and is associated with adverse effects that might compromise quality of life. Emerging studies on the molecular mechanisms of SRCSs and the development of genetically engineered animal models hold promise for improvements in early detection, disease monitoring, treatment-related toxicity, overall survival and quality of life.

CIC-DUX4 sarcomas

PURPOSE OF REVIEW

CIC-DUX4 sarcoma (CDS) is a high-grade undifferentiated round cells sarcoma that belongs to the undifferentiated round cell sarcomas family. It represents less than one percent of sarcomas, defining a rarest among rare malignancies. It affects young adults, displaying soft tissue mass. Considered very aggressive, a high proportion of cases display an advanced disease with lung metastasis at diagnosis. Here we discuss recent progress in molecular characterization of CDS, the main tracks of CDS biology and the current and future prospects of therapeutic approaches.

RECENT FINDINGS

CDS is characterized by a specific oncogenic translocation CIC::DUX4 that induce ETV4 overexpression. Patients with CDS show an aggressive clinical course and have a significantly unfavorable outcome compared to Ewing sarcoma. As of today, there is a lack of consensus on whether they should be treated with an Ewing-like approach, as currently done by most sites, or regarded as high-grade soft tissue sarcoma (STS). Anyway, when feasible, combination regimens including anthracycline and alkylating agents should be favored and patients should not benefit from a therapeutic de-escalation. Overall, registration within clinical trials and prospective registries is recommended.

SUMMARY

Overall, CDS showed a poor prognosis regardless of the patterns of treatment that warrant biological studies to better understand the disease.

Establishment of Organoids From Human Epithelioid Sarcoma With the Air-Liquid Interface Organoid Cultures

Background

Although biological resources are essential for basic and preclinical research in the oncological field, those of sarcoma are not sufficient for rapid development of the treatment. So far, some sarcoma cell lines have been established, however, the success rate was low and the established sarcoma types were frequently biased. Therefore, an efficient culture method is needed to determine the various types of sarcomas. Organoid culture is a 3-dimentional culture method that enables the recapitulation of the tumor microenvironment and the success rate reported is higher than the 2-dimentional culture. The purpose of this study was to report our newly established organoids from human epithelioid sarcoma using the air-liquid interface organoid culture method.

Methods

We treated 2 patients with epithelioid sarcoma in our institute. The remaining sarcoma specimens after surgical resection were embedded in collagen type 1 gels according to the air-liquid interface organoid culture method. After serial passages, we xenografted the organoids to NOD-scid IL2Rgnull (NSG) mice. Using the developed tumors, we performed histological and genomic analyses to compare the similarities and differences with the original epithelioid sarcoma from the patient.

Results

Organoids from the epithelioid sarcoma could be serially cultured and maintained in collagen type 1 gels for more than 3 passages. Developed orthotopic tumor xenografts were detected in the NSG mice. After the process was repeated severally, the patient derived organoid lines from the epithelioid sarcoma were established. The established organoids showed loss of integrase interactor 1 expression with polymerase chain reaction and immunohistochemical analyses. The xenografted organoids of the epithelioid sarcoma had histologically similar phenotypes with the original tumor and genetically resembled it to some degree.

Conclusions

The present study demonstrated 2 novel established organoid models of epithelioid sarcoma, and our organoid models could be used to investigate the molecular pathogenesis and develop a novel treatment.

Systemic treatments and outcomes in CIC-rearranged Sarcoma: A national multi-centre clinicopathological series and literature review

CIC‐rearranged sarcoma is a recently established, ultra‐rare, molecularly defined sarcoma subtype. We aimed to further characterise clinical features of CIC‐rearranged sarcomas and explore clinical management including systemic treatments and outcomes.

Integrated Molecular Characterization of Patient-Derived Models Reveals Therapeutic Strategies for Treating CIC-DUX4 Sarcoma

Capicua-double homeobox 4 (CIC-DUX4)-rearranged sarcomas (CDS) are extremely rare, highly aggressive primary sarcomas that represent a major therapeutic challenge. Patients are treated according to Ewing sarcoma protocols, but CDS-specific therapies are strongly needed. In this study, RNA sequencing was performed on patient samples to identify a selective signature that differentiates CDS from Ewing sarcoma and other fusion-driven sarcomas. This signature was used to validate the representativeness of newly generated CDS experimental models-patient-derived xenografts (PDX) and PDX-derived cell lines-and to identify specific therapeutic vulnerabilities. Annotation analysis of differentially expressed genes and molecular gene validation highlighted an HMGA2/IGF2BP/IGF2/IGF1R/AKT/mTOR axis that characterizes CDS and renders the tumors particularly sensitive to combined treatments with trabectedin and PI3K/mTOR inhibitors. Trabectedin inhibited IGF2BP/IGF2/IGF1R activity, but dual inhibition of the PI3K and mTOR pathways was required to completely dampen downstream signaling mediators. Proof-of-principle efficacy for the combination of the dual AKT/mTOR inhibitor NVP-BEZ235 (dactolisib) with trabectedin was obtained in vitro and in vivo using CDS PDX-derived cell lines, demonstrating a strong inhibition of local tumor growth and multiorgan metastasis. Overall, the development of representative experimental models (PDXs and PDX-derived cell lines) has helped to identify the unique sensitivity of the CDS to AKT/mTOR inhibitors and trabectedin, revealing a mechanism-based therapeutic strategy to fight this lethal cancer.

SIGNIFICANCE

This study identifies altered HMGA2/IGF2BP/IGF2 signaling in CIC-DUX4 sarcomas and provides proof of principle for combination therapy with trabectedin and AKT/mTOR dual inhibitors to specifically combat the disease.

Inactivation of the CIC-DUX4 oncogene through P300/CBP inhibition, a therapeutic approach for CIC-DUX4 sarcoma

CIC-DUX4 sarcoma (CDS) is a highly aggressive and metastatic small round type of predominantly pediatric sarcoma driven by a fusion oncoprotein comprising the transcriptional repressor Capicua (CIC) fused to the C-terminal transcriptional activation domain of DUX4. CDS rapidly develops resistance to chemotherapy, thus novel specific therapies are greatly needed. We demonstrate that CIC-DUX4 requires P300/CBP to induce histone H3 acetylation, activate its targets, and drive oncogenesis. We describe the synthetic route to a selective and highly potent P300/CBP inhibitor named iP300w and related stereoisomers, and find that iP300w efficiently suppresses CIC-DUX4 transcriptional activity and reverses CIC-DUX4 induced acetylation. iP300w is active at 100-fold lower concentrations than related stereoisomers or A-485. At low doses, iP300w shows specificity to CDS cancer cell lines, rapidly inducing cell cycle arrest and preventing growth of established CDS xenograft tumors when delivered in vivo. The effectiveness of iP300w to inactivate CIC-DUX4 highlights a promising therapeutic opportunity for CDS.

A novel BRD4-LEUTX fusion in a pediatric sarcoma with epithelioid morphology and diffuse S100 expression

Malignant epithelioid soft tissue tumors encompass a wide spectrum of lesions. Among them, Epithelioid Malignant Peripheral Nerve Sheath Tumors (MPNST) constitute a distinct subgroup, accounting for <5% of all MPNST. Epithelioid MPNST are infrequently associated with neurofibromatosis type 1, occasionally arise in a schwannoma and show diffuse S100 and CD34 expression, often combined with INI-1 loss. However, the molecular mechanisms underlying the tumorigenesis of epithelioid MPNST remain largely unknown. We describe a case of a 10-year-old girl with an epithelioid malignancy of the orbit. The tumor proved positive for S100, CD34 and SOX10, and, although INI-1 expression was maintained, the overall features suggested the possibility of an epithelioid MPNST, arising in an unusual location. NGS analysis revealed a novel in-frame BRD4-LEUTX fusion gene. LEUTX plays an important role in embryonal genome activation and its expression is mostly suppressed postnatally. We were able to detect increased levels of LEUTX transcript in the tumor, indicating that BRD4-LEUTX fusion leads to LEUTX re-activation. To our knowledge, this fusion has never been reported previously. Whether the current case represents an example of epithelioid MPNST or a distinct tumor entity remains to be determined.

Control of DUX4 Expression in Facioscapulohumeral Muscular Dystrophy and Cancer

DUX4, a gene encoding a transcription factor involved in early embryogenesis, is located within the D4Z4 subtelomeric repeat on chromosome 4q35. In most healthy somatic tissues, DUX4 is heavily repressed by multiple genetic and epigenetic mechanisms, and its aberrant expression is linked to facioscapulohumeral muscular dystrophy (FSHD) where it has been extensively studied. Recently, DUX4 expression has been implicated in oncogenesis, although this is much less explored. In this review, we discuss multiple levels of control of DUX4 expression, including enhancer-promoter interactions, DNA methylation, histone modifications, noncoding RNAs, and telomere positioning effect. We also connect disparate data on intrachromosomal contacts involving DUX4 and emphasize the feedback loops in DUX4 regulation. Finally, we bridge data on DUX4 in FSHD and cancer and discuss prospective approaches for future FSHD therapies and the potential outcomes of DUX4 inhibition in cancer.

Case Report: A Unique Case of Pediatric Central Nervous System Embryonal Tumor Harboring the CIC-LEUTX Fusion, Germline NBN Variant and Somatic TSC2 Mutation: Expanding the Spectrum of CIC-Rearranged Neoplasia

Central nervous system (CNS) embryonal tumors (WHO grade IV) are a heterogeneous group of rare, poorly differentiated neuroepithelial malignant neoplasms that commonly occur in children, and they have a poor prognosis. The 2016 WHO (World Health Organization) classification of CNS tumors created a major shift in paradigm of the classification of embryonal tumors. However, some cases were still difficult to classify. Further integrative genomic analysis is needed to improve the precise classification, diagnosis and treatment of CNS embryonal tumors. Herein, we firstly report a case of CNS embryonal tumor harboring the pathogenic CIC–LEUTX gene fusion. A 2-year-old male infant presented with a solid cystic mass in the left temporal lobe-basal ganglia and left parietal lobe (maximum diameter, 75 mm) and underwent gross tumor resection. The tumor was classified as a poorly differentiated embryonal neoplasm of neuroectodermal origin that lacked specific features and rosettes. By immunohistochemistry, the tumor cells were strongly positive for synaptophysin, and the Ki67 proliferation index was high (>50%). FISH (Fluorescence in situ hybridization) results indicated no change in the copy number at the 19q13.42 C19MC locus. Next generation sequencing showed a CIC–LEUTX gene fusion, a somatic TSC2 c.G2714A mutation, and a heterozygous germline NBN c.C127T mutation. One month after surgery, there was recurrence of the intracranial tumor (maximum diameter, 55 mm) as well as spinal cord implantation metastasis. The patient received chemotherapy (CTX+CBP+VCR/DDP+VP-16), radiotherapy, and a drug targeting the TSC2 gene (everolimus). At the time of this writing, the patient is alive without evidence of disease for 11 months. This is the first report of the CIC–LEUTX gene fusion in a case of CNS embryonal tumor.

Establishment and characterization of NCC-CDS2-C1: a novel patient-derived cell line of CIC-DUX4 sarcoma

CIC-DUX4 sarcoma (CDS), an aggressive soft tissue sarcoma, is characterized by a CIC and DUX4 rearrangement. It has a dismal clinical course and high metastatic rate and shows chemotherapy resistance; therefore, a novel therapeutic strategy is required. Patient-derived cell lines are indispensable tools for basic and preclinical research. However, only a few patient-derived CDS cell lines have been currently reported. Therefore, in this study, we aimed to establish and characterize a novel cell line of CDS. We successfully established the NCC-CDS2-C1 cell line by using surgically resected tumor tissue from a patient with CDS. The NCC-CDS2-C1 cells harbored a CIC-DUX4 fusion gene without insertion and exhibited rapid growth, spheroid formation, and invasion. We screened the antiproliferative effects of small anticancer agent compounds, which included FDA-approved anticancer drugs, on NCC-CDS2-C1 cells in comparison with those on the two previously reported patient-derived CDS cell lines, NCC-CDS1-X1-C1 and NCC-CDS1-X3-C1. The response profile of NCC-CDS2-C1 was similar to but distinct from those of the other cell lines for the small anticancer agent compounds. Therefore, we conclude that the NCC-CDS2-C1 cell line will be a useful tool for basic and preclinical studies of CDS.