The Effect of Direct and Indirect EZH2 Inhibition in Rhabdomyosarcoma Cell Lines

Abstract

Enhancer of Zeste homolog 2 (EZH2) is involved in epigenetic regulation of gene transcription by catalyzing trimethylation of histone 3 at lysine 27. In rhabdomyosarcoma (RMS), increased EZH2 protein levels are associated with poor prognosis and increased metastatic potential, suggesting EZH2 as a therapeutic target. The inhibition of EZH2 can be achieved by direct inhibition which targets only the enzyme activity or by indirect inhibition which also affects activities of other methyltransferases and reduces EZH2 protein abundance. We assessed the direct inhibition of EZH2 by EPZ005687 and the indirect inhibition by 3-deazaneplanocin (DZNep) and adenosine dialdehyde (AdOx) in the embryonal RD and the alveolar RH30 RMS cell line. EPZ005687 was more effective in reducing the cell viability and colony formation, in promoting apoptosis induction, and in arresting cells in the G1 phase of the cell cycle than the indirect inhibitors. DZNep was more effective in decreasing spheroid viability and size in both cell lines than EPZ005687 and AdOx. Both types of inhibitors reduced cell migration of RH30 cells but not of RD cells. The results show that direct and indirect inhibition of EZH2 affect cellular functions differently. The alveolar cell line RH30 is more sensitive to epigenetic intervention than the embryonal cell line RD.

Combination EZH2 inhibition and retinoic acid treatment promotes differentiation and apoptosis in rhabdomyosarcoma cells

“…In FPRMS, the pro-apoptosis phenotype appeared to be driven by ATRA potentiated by EZH2 inhibition. This pro-apoptotic phenotype in FPRMS has been observed in a number of previous studies where RH30 cells treated with EZH2i resulted in a dose-dependent increase in apoptosis rather than differentiation [13,14]. This apoptotic phenotype may be immune-related as genes of the IFN-α pathway were upregulated.…”

“…Together these results suggest a pro-differentiative effect of EZH2 inhibition in RMS [7,14,15]. However, these single agent targeting strategies did not lead to complete differentiation or apoptosis in RMS models.…”

CRISPR/Cas9‑mediated EZH2 knockout suppresses the proliferation and migration of triple‑negative breast cancer cells

“…Recent research has suggested that enhancer of zeste homolog 2 (EZH2) serves as a key component of polycomb repressive complex 2 (PRC2) (12). EZH2 serves a role in chromosomal structure formation, cell cycle regulation, senescence, cell differentiation and promotion of tumor growth and metastasis in malignant tumor models (13)(14)(15). Hussein et al (16) reported a notable correlation between high EZH2 expression and TNBC phenotype, suggesting its biological role in this aggressive disease.…”

Pediatric Cancers: Insights and Novel Therapeutic Approaches

“…ATXII was found to induce DNA double-strand breaks and cell cycle S phase accumulation without directly binding to the DNA [21]. In rhabdomyosarcoma, increased EZH2 protein levels are associated with poor prognosis and increased metastatic potential [22]. Direct and indirect targeting of EZH2 showed differential efficacy due to divergent epigenetic and cellular signaling regulations in different rhabdomyosarcoma cell subtypes [22].…”

“…In rhabdomyosarcoma, increased EZH2 protein levels are associated with poor prognosis and increased metastatic potential [22]. Direct and indirect targeting of EZH2 showed differential efficacy due to divergent epigenetic and cellular signaling regulations in different rhabdomyosarcoma cell subtypes [22]. A research study by Lavoie et al using cell surface proteomics, transcriptomics, and tissue specimens uncovers B7-H3 as a major immunoregulatory molecule expressed by rhabdomyosarcomas and not by normal human tissues [23].…”