Targeted CRISPR screening identifies PRMT5 as synthetic lethality combinatorial target with gemcitabine in pancreatic cancer cells

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most challenging cancer to treat. Due to the asymptomatic nature of the disease and ineffective drug treatment modalities, the survival rate of PDAC patients remains one of the lowest. The recurrent genetic alterations in PDAC are yet to be targeted; therefore, identifying effective therapeutic combinations is desperately needed. Here, we performed an in vivo CRISPR screening in a clinically relevant patient-derived xenograft (PDX) model system to identify synergistic drug combinations for PDAC treatment. Our approach revealed protein arginine methyltransferase gene 5 (PRMT5) as a promising druggable candidate whose inhibition creates synergistic vulnerability of PDAC cells to gemcitabine. Genetic and pharmacological inhibition results indicate that of PRMT5 depletion results in synergistic cytotoxicity with Gem due to depleted replication protein A (RPA) levels and an impaired non-homology end joining (NHEJ) DNA repair.Thus, the novel combination creates conditional lethality through the accumulation of excessive DNA damage and cell death, both in vitro and in vivo. The findings demonstrate that unbiased genetic screenings combined with a clinically relevant model system is an effective approach in identifying synthetic lethal drug combinations for cancer treatment. STATEMENT of SIGNIFICANCEIdentify synergistic drug combinations for PDAC is a significant unmet need. Through CRISPR screening, we discovered and validated that PRMT5 depletion creates synergistic vulnerability of PDAC cells to gemcitabine. Mechanistically, the combination impairs DNA repair, synergistic accumulation of DNA damage and cell death in vitro and in vivo.

Epigenetic drug screening defines a PRMT5 inhibitor–sensitive pancreatic cancer subtype

“…JNJ-64619178 distinctly reduced the symmetrical dimethylation of histone H4R3 (Supplemental Figure 5A). Recent data demonstrated that PRMT5 blockade induces a DNA damage response in PDAC cells (27). Therefore, we investigated phosphorylation of H2AX as a surrogate for the DNA damage response.…”

“…PRMT5 is a type II protein arginine methyltransferase catalyzing symmetrical dimethylation of arginines in histones and other proteins (24). High PRMT5 expression was recently linked to worse survival of patients with PDAC (25)(26)(27). To underpin the connection of MYC to PRMT5, we analyzed curated mRNA expression data sets (20,28).…”

Systematic Evaluation Meta-Analysis of the Efficacy of Recombinant Human Endostatin Combined with Gemcitabine and Cisplatin in Non-Small-Cell Lung Cancer

“…e results of this analysis fully confirm that gemcitabine plus platinum combined regimen can significantly prolong the total and progression-free survival of patients with advanced NSCLC compared with other platinum-containing schemes. In 2007, Grossi et al's metaanalysis compared the activity of gemcitabine with three other third-generation platinum-containing chemotherapy programs [15]. e meta-analysis included 48 studies, with 6,671 patients.…”

Functional genomics approaches to improve pre‐clinical drug screening and biomarker discovery

“…In another example, Wei and colleagues used a targeted CRISPR screening approach on a PDTX model established from poorly differentiated metastatic pancreatic ductal adenocarcinoma, known to contain KRAS, p53 and SMAD4 mutations. They identified PRMT5 as a therapeutic target for cells co-treated with Gemcitabine chemotherapy (Wei et al, 2020).…”