Targeting the ERG oncogene with splice-switching oligonucleotides as a novel therapeutic strategy in prostate cancer

Abstract

BACKGROUND: The ERG oncogene is activated in 50% of prostate cancers. We have designed morpholino-based oligonucleotides that target the ERG oncogene by inducing skipping of exon 4. METHODS: We designed antisense splice-switching morpholino oligonucleotides (SSOs) that target exon 4. We tested their efficacy in ERG-positive VCaP prostate cancer and MG63 osteosarcoma cell lines. We measured their effect on ERG expression, cell proliferation, migration and apoptosis in cell lines, xenografts and a radical prostatectomy sample. RESULTS: SSOs induced exon 4 skipping, reducing ERG levels up to 96 hours following transfection. SSO-induced ERG reduction decreased cell proliferation, cell migration and increased apoptosis. We observed a reduction in cyclin D1, c-Myc, β-catenin and a marker of activated Wnt signalling, p-LRP6. SSOs reduced the growth of MG63 xenografts in mice. We also demonstrated that the SSOs cause a reduction in ERG expression in a patient-derived radical prostatectomy sample ex vivo. CONCLUSIONS: We have successfully tested morpholino-based SSOs that cause a marked reduction in ERG expression, resulting in decreased cell proliferation, a reduced migratory phenotype and increased apoptosis. Our initial tests on mouse xenografts and a human prostate cancer radical prostatectomy specimen indicate that SSOs can be effective for ERG oncogene targeting in vivo.

Antisense Oligonucleotide-Mediated Exon-skipping Therapies: Precision Medicine Spreading from Duchenne Muscular Dystrophy

“…An ASO designed to induce the skipping of exon 41 of LRRK2 , which encodes part of the kinase domain, was developed to reduce LRRK2 kinase function in patients with genetic and sporadic Parkinson’s disease (48) . Interestingly, an ASO designed to induce the skipping of the out-of-frame exon 4 of the fusion gene ERG was developed to suppress its function in prostate cancer cells and markedly reduced ERG protein levels, resulting in decreased cell proliferation (49) .…”

Splice‐switch oligonucleotide‐based combinatorial platform prioritizes synthetic lethal targets CHK1 and BRD4 against MYC‐driven hepatocellular carcinoma

“…Prior studies have also exhibited the value of SSOs as candidate therapeutic agents in cancer. 38 , 45 , 46 , 47 , 88 It may therefore be of value to further develop and optimize ssCHK1 and ssBRD4 as potential therapeutic agents against MYC‐driven HCC in a situation where no viable pharmacological agents are available for clinical use. Further chemical modifications to ssCHK1 and ssBRD4 such as the use of a morpholino‐based backbone can render them resistant to enzymatic degradation in biologic fluids and suitable for subsequent clinical applications, as demonstrated in the FDA‐approved SSOs.…”

“… 39 , 40 , 41 , 42 , 43 , 44 Recent advances in SSO technologies have also demonstrated the value of SSOs as candidate RNA therapeutics with significant anticancer properties in in vivo models of HCC, melanoma, prostate, and lung cancer. 38 , 45 , 46 , 47 Additionally, prior applications of SSOs have exhibited dose‐dependent splice‐switch events and is therefore suitable for use in conjunction with QPOP for target prioritization, where the dosages of the therapeutics are considered. 48 …”

“…[39][40][41][42][43][44] Recent advances in SSO technologies have also demonstrated the value of SSOs as candidate RNA therapeutics with significant anticancer properties in in vivo models of HCC, melanoma, prostate, and lung cancer. 38,[45][46][47] Additionally, prior applications of SSOs have exhibited dose-dependent splice-switch events and is therefore suitable for use in conjunction with QPOP for target prioritization, where the dosages of the therapeutics are considered. 48 Here, we report the development and the use of SSO-QPOP that exhibits a novel function in the target prioritization stage of the drug development pipeline by leveraging on genetic modulators.…”

Targeting signaling pathways in prostate cancer: mechanisms and clinical trials

“… 539 Interestingly, a novel oligonucleotide-based agent that targets ERG by inducing skipping of its constitutive exon 4 resulted in a reduction in ERG protein levels and tumor growth in mice. 540 Although these agents have not entered clinical practice yet, splicing events are a plausible mechanism for treating PCa, and further research is warranted.…”