Antitumor effects of PRMT5 inhibition in sarcomas [RNA-seq]

Patients with advanced soft-tissue sarcomas (STSs) have few therapeutic options. Protein arginine methyltransferase 5 (PRMT5), an anticancer target, has been extensively investigated in recent years in epithelial tumors. To date, no data related to the biological role of PRMT5 inhibition and its potential effect as a treatment in STS have been reported. To investigate the therapeutic potential of PRMT5 targeting in STS, we first evaluated the prognostic value of PRMT5 expression in 2 different cohorts of patients with STS. We then used the potent and selective GSK3326595 (GSK595) compound to investigate the antitumor effect of the pharmacological inhibition of PRMT5 in vitro via MTT, apoptosis, cell cycle, clonogenicity and proliferation assays. In vivo studies were performed with two animal models to evaluate the effects of GSK595 on tumor growth. The mechanisms of action were investigated by RNA sequencing, metabolic pathway analysis, Western blotting and glucose uptake/lactate production assays. High PRMT5 gene expression levels were significantly associated with worsened metastasis-free survival of STS patients. GSK595 decreased the global symmetric dimethylarginine level, the proliferation rate and clonogenicity of STS cell lines in vitro and tumor growth in vivo. Moreover, PRMT5 inhibition regulated aerobic glycolysis through downregulation of key enzymes of glycolysis as well as glucose uptake and lactate production. The present study demonstrated that PRMT5 regulates STS cell metabolism and thus represents a potential therapeutic target for STS. Additional studies in diverse sarcoma subtypes will be essential to confirm and expand upon these findings. Overall design: To decipher the mechanism of action of PRMT5 inhibition in STS cell lines, we explored the transcriptomic changes in IB111 cells after 10 days of treatment by RNA sequencing. IB111 cells were untreated or treated with GSK595 at the IC50 every 3 days for 10 days in triplicate. RNA was then extracted and sequenced on a NovaSeq6000 S2 platform.