Project description:To identify the mechanistic underpinning of the anti-tumor activity of PRMT5 inhibition in MCL, we explored transcriptomic profiles of PDX-AA cells treated in vivo for 2 weeks with PRT-382, ibrutinib, or vehicle control (n=3/group).
Project description:Mantle cell lymphoma (MCL) is an incurable B-cell non-Hodgkin lymphoma, and patients who relapse on targeted therapies have poor prognosis. Protein arginine methyltransferase 5 (PRMT5), an enzyme essential for B-cell transformation, drives multiple oncogenic pathways and is overexpressed in MCL. Despite the antitumor activity of PRMT5 inhibition (PRT-382/PRT-808), drug resistance was observed in a patient-derived xenograft (PDX) MCL model. Decreased survival of mice engrafted with these PRMT5 inhibitor-resistant cells vs treatment-naive cells was observed (P = .005). MCL cell lines showed variable sensitivity to PRMT5 inhibition. Using PRT-382, cell lines were classified as sensitive (n = 4; 50% inhibitory concentration [IC50], 20-140 nM) or primary resistant (n = 4; 340-1650 nM). Prolonged culture of sensitive MCL lines with drug escalation produced PRMT5 inhibitor-resistant cell lines (n = 4; 200-500 nM). This resistant phenotype persisted after prolonged culture in the absence of drug and was observed with PRT-808. In the resistant PDX and cell line models, symmetric dimethylarginine reduction was achieved at the original PRMT5 inhibitor IC50, suggesting activation of alternative resistance pathways. Bulk RNA sequencing of resistant cell lines and PDX relative to sensitive or short-term-treated cells, respectively, highlighted shared upregulation of multiple pathways including mechanistic target of rapamycin kinase [mTOR] signaling (P < 10-5 and z score > 0.3 or < 0.3). Single-cell RNA sequencing analysis demonstrated a strong shift in global gene expression, with upregulation of mTOR signaling in resistant PDX MCL samples. Targeted blockade of mTORC1 with temsirolimus overcame the PRMT5 inhibitor-resistant phenotype, displayed therapeutic synergy in resistant MCL cell lines, and improved survival of a resistant PDX.
Project description:MCL cell lines were treated with DMSO or 5uM AFN700 for 20hrs This experiment is designed to see if NFKB-target genes are downregulated by inhibition of IKKB in MCL cell lines that are insensitive to ibrutinib (BTK inhibitor) or sotrastaurin (PKC inhibitor) MCL cells were seeded in 6well dishes and treated for 20hrs with DMSO or 5uM AFN700
Project description:Aberrant protein arginine methylation has been observed in multiple cancer types, making it an attractive drug target. Proteins can undergo asymmetric arginine methylation by type I protein arginine methyltransferases (PRMTs), predominately by PRMT1 and to a lesser extent PRMT4, or symmetric arginine methylation by type II PRMTs, predominately PRMT5. Here, we performed targeted proteomics following inhibition of PRMT1, PRMT4, and PRMT5 across cancer cell lines. We found that inhibition of both type I and type II PRMTs suppressed levels of total and phosphorylated ATR protein in cancer cell lines, and down-regulated expression of the ATR gene. Loss of ATR from PRMT inhibition resulted in defective DNA replication stress response activation in following exogenous replication stress. Since PARP inhibitors are known to induce replication stress, we next combined PRMT inhibition with PARP inhibition and found inhibition of PRMT1 or PRMT5 greatly exacerbated PARP inhibitor induced DNA damage. Based on this observation, we assessed the combination of PARP and PRMT inhibition in a panel of cell lines. While inhibition of both type I and type II PRMTs were synergistic with PARP inhibition in both cells with intact and deficient homologous recombination, type I PRMT inhibition resulted in higher toxicity in non-malignant cells. Therefore, we validated the synergy of combined PARP/PRMT5 inhibition in primary patient-derived organoids. Finally, we demonstrate that the combination of PARP and PRMT5 inhibition improves overall survival in both BRCA-mutant and wild-type patient-derived xenograft models without any detectable hematological toxicities typically associated with PARPi combination therapies. Taken together, these results demonstrate that PRMT5 inhibition may be a well-tolerated approach to improve tumor sensitivity to PARP inhibition. .
Project description: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.