Epigenetic control of the EWS‑FLI1 promoter in Ewing's sarcoma

Ewing sarcoma from molecular biology to the clinic

In Europe, with an incidence of 7.5 cases per million, Ewing sarcoma (ES) is the second most common primary malignant bone tumor in children, adolescents and young adults, after osteosarcoma. Since the 1980s, conventional treatment has been based on the use of neoadjuvant and adjuvant chemotherapeutic agents combined with surgical resection of the tumor when possible. These treatments have increased the patient survival rate to 70% for localized forms, which drops drastically to less than 30% when patients are resistant to chemotherapy or when pulmonary metastases are present at diagnosis. However, the lack of improvement in these survival rates over the last decades points to the urgent need for new therapies. Genetically, ES is characterized by a chromosomal translocation between a member of the FET family and a member of the ETS family. In 85% of cases, the chromosomal translocation found is (11; 22) (q24; q12), between the EWS RNA-binding protein and the FLI1 transcription factor, leading to the EWS-FLI1 fusion protein. This chimeric protein acts as an oncogenic factor playing a crucial role in the development of ES. This review provides a non-exhaustive overview of ES from a clinical and biological point of view, describing its main clinical, cellular and molecular aspects.

Lysine specific demethylase 1 is a molecular driver and therapeutic target in sarcoma

Sarcomas are a diverse group of tumors with numerous oncogenic drivers, and display varied clinical behaviors and prognoses. This complexity makes diagnosis and the development of new and effective treatments challenging. An incomplete understanding of both cell of origin and the biological drivers of sarcomas complicates efforts to develop clinically relevant model systems and find new molecular targets. Notably, the histone lysine specific demethylase 1 (LSD1) is overexpressed in a number of different sarcomas and is a potential therapeutic target in these malignancies. With the ability to modify histone marks, LSD1 is a key player in many protein complexes that epigenetically regulate gene expression. It is a largely context dependent enzyme, having vastly different and often opposing roles depending on the cellular environment and which interaction partners are involved. LSD1 has been implicated in the development of many different types of cancer, but its role in bone and soft tissue sarcomas remains poorly understood. In this review, we compiled what is known about the LSD1 function in various sarcomas, to determine where knowledge is lacking and to find what theme emerge to characterize how LSD1 is a key molecular driver in bone and soft tissue sarcoma. We further discuss the current clinical landscape for the development of LSD1 inhibitors and where sarcomas have been included in early clinical trials.

Gene expression profiling utilizing extremely sensitive CDNA arrays and enrichment-based network study of major bone cancer genes

Background:

The gene interaction network is a set of genes interconnected by functional interactions among the genes. The gene interaction networks are studied to determine pathways and regulatory mechanisms in model organisms. In this research, the enrichment study of bone cancer-causing genes is undertaken to identify several hub genes associated to the development of bone cancer.

Materials and Methods:

Data on bone cancer is obtained from mutated gene samples; highly mutated genes are selected for the enrichment analysis. Due to certain interactions with each other the interaction network model for the hub genes is developed and simulations are produced to determine the levels of expression. For the array analyses, a total of 100 tumor specimens are collected. Cell cultures are prepared, RNA is extracted, cDNA arrays probes are generated, and the expressions analysis of Hub genes is determined.

Results:

Out of cDNA array findings, only 7 genes: CDKN2A, AKT1, NRAS, PIK3CA, RB1, BRAF, and TP53 are differentially expressed and shown as significant in the development of bone tumors, approximately 15 pathways have been identified, including pathways for non-small cell lung cancer, prostate cancer, pancreatic cancer, chronic myeloid leukemia, and glioma, consisting of all the identified 7 genes. After clinical validations of tumor samples, the IDH1 and TP53 gene revealed significant number of mutations similar to other genes. Specimens analysis showed that RB1, P53, and NRAS are amplified in brain tumor, while BRAF, CDKN2A, and AKT1 are amplified in sarcoma. Maximum deletion mutations of the PIK3CA gene are observed in leukemia. CDKN2A gene amplifications have been observed in virtually all tumor specimens.

Conclusion:

This study points to a recognizable evidence of novel superimposed pathways mechanisms strongly linked to cancer.

Selective inhibition of HDAC6 regulates expression of the oncogenic driver EWSR1-FLI1 through the EWSR1 promoter in Ewing sarcoma

Ewing sarcoma (EWS) is an aggressive bone and soft tissue tumor of children and young adults in which the principal driver is a fusion gene, EWSR1-FLI1. Although the essential role of EWSR1-FLI1 protein in the regulation of oncogenesis, survival, and tumor progression processes has been described in-depth, little is known about the regulation of chimeric fusion-gene expression. Here, we demonstrate that the active nuclear HDAC6 in EWS modulates the acetylation status of specificity protein 1 (SP1), consequently regulating the SP1/P300 activator complex binding to EWSR1 and EWSR1-FLI1 promoters. Selective inhibition of HDAC6 impairs binding of the activator complex SP1/P300, thereby inducing EWSR1-FLI1 downregulation and significantly reducing its oncogenic functions. In addition, sensitivity of EWS cell lines to HDAC6 inhibition is higher than other tumor or non-tumor cell lines. High expression of HDAC6 in primary EWS tumor samples from patients correlates with a poor prognosis in two independent series accounting 279 patients. Notably, a combination treatment of a selective HDAC6 and doxorubicin (a DNA damage agent used as a standard therapy of EWS patients) dramatically inhibits tumor growth in two EWS murine xenograft models. These results could lead to suitable and promising therapeutic alternatives for patients with EWS.