Ewing’s sarcoma (ES) is a pediatric sarcoma caused by a chromosomal translocation. Unlike in most cancers, the genomes of ES patients are very stable. The translocation product of the EWS-FLI1 fusion is most often the predominant genetic driver of oncogenesis, and it is pertinent to explore the role of epigenetic alterations in the onset and progression of ES. Several types of noncoding RNAs, primarily microRNAs and long noncoding RNAs, are key epigenetic regulators that have been shown to play critical roles in various cancers. The functions of these epigenetic regulators are just beginning to be appreciated in ES. Here, we performed a comprehensive literature review to identify these noncoding RNAs. We identified clinically relevant tumor suppressor microRNAs, tumor promoter microRNAs and long noncoding RNAs. We then explored the known interplay between different classes of noncoding RNAs and described the currently unmet need for expanding the noncoding RNA repertoire of ES. We concluded the review with a discussion of epigenetic regulation of ES via regulatory noncoding RNAs. These noncoding RNAs provide new avenues of exploration to develop better therapeutics and identify novel biomarkers.

Receptor Expressed in Lymphoid Tissues (RELT), is a human TNFR superfamily member (TNFRSF19L) expressed most prominently in the hematopoietic system. Previous reports using RELT knockout mice indicate that RELT functions in part by inhibiting the proliferation and activation of T lymphocytes. RELT is an orphan receptor that has two homologous binding partners, RELL1 and RELL2, and collectively, these three proteins are referred to as RELT family members. This study sought to identify novel protein interactions with RELT family members and to compare the expression of RELT in normal and diseased human tissues. A yeast two-hybrid screen utilizing RELL1 as bait identified the cytoskeletal protein Filamin A (FLNA) as a prospective binding partner and physical interaction between FLNA and RELT family members was confirmed by in vitro co-immunoprecipitation. A truncated mutant of FLNA disrupts the ability of RELT family members to activate the p38 pathway and blocks the ability of RELT to induce death in human epithelial cells. Western blotting revealed endogenous RELT family members are most significantly upregulated in the breast cancer cell lines MDA-MB-231 and MCF-7, as well as the lung cancer cell line H358. Preliminary immunohistochemistry results reveal a higher intensity of RELT staining in both breast cancer and lung cancer human biopsies versus non-malignant tissue. Additionally, overexpression of RELT family members enhanced apoptosis in MDA-MB-231 and H358 cells as measured by X-gal morphology and luciferase assays. Collectively, these results further our understanding of signal transduction pathways associated with RELT family members and report the novel finding that RELT is upregulated in human breast and lung cancers. Supported by California Northstate University, College of Medicine, Seed Grant.