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P1.05 - Poster Session 1 - Preclinical Models of Therapeutics/Imaging (ID 156)
- Event: WCLC 2013
- Type: Poster Session
- Track: Biology
- Presentations: 1
- Coordinates: 10/28/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P1.05-006 - Targeted delivery of RRM1-specific siRNA leads to tumour growth inhibition in malignant pleural mesothelioma (ID 1508)
09:30 - 16:30 | Author(s): N. Mugridge
Malignant pleural mesothelioma (MPM) is an asbestos-related malignancy with poor prognosis. MPM is typically recalcitrant to treatment and new therapies are urgently needed. Multiple genes involved in proliferation and metabolic activity are upregulated in MPM and these represent attractive targets for an siRNA-based therapeutic intervention.
We carried out an RNAi-based screen of 40 target genes previously shown to be upregulated in MPM to identify candidate genes with roles in cell growth and survival in MPM cell lines. Effects of target gene silencing were measured using standard in vitro proliferation assays. Lead candidates were further assessed with siRNA dose response experiments. The specificity of siRNA-mediated growth inhibition was confirmed by assessing gene knockdown by real-time qPCR and Western blotting. The effects of the most potent siRNAs on xenograft tumour growth were assessed in vivo by delivery using EGFR-targeted, siRNA-loaded, minicells.
All 40 genes were effectively silenced, and for 6 genes (PLK1, CDK1, NDC80, RRM1, RRM2 and BIRC5) knockdown with 2 independent siRNAs resulted in significant growth inhibition over time in multiple cell lines. Dose response experiments revealed that siRNAs specific for RRM1 and RRM2 were the most effective at inhibiting growth with IC50 values in the low nanomolar range. Intravenous administration of RRM1 siRNA packaged in minicells targeted with EGFR-specific antibodies (2x10 minicells per dose, 4 times per week for 3 weeks) led to consistent and dose-dependent inhibition of MPM tumor growth compared with treatment with an inactive siRNA. Reducing the dose and number of administrations did not reduce growth inhibition; as little as 1x10 minicells administered once a week were sufficient to completely inhibit MPM tumour growth.
RRM1 is an attractive target for siRNA-based inhibition, and siRNA delivery with EGFR-targeted minicells represents a novel therapeutic approach for MPM.