Anti-sense RNA therapeutics offer tremendous potential in their capacity to suppress genes encoding proteins that are “undruggable” by classical small molecules, using a technology that is quick in both drug design and synthesis. All RNA-therapies approved to date (and almost all therapies undergoing clinical trial) utilise single RNAs designed to target one specific gene. Many diseases however, particularly cancer, are multifactorial and it is often combinatorial strategies (in which multiple genes are co-targeted) that are the most effective.
Here, we utilise combinations of optimised siRNAs to cross-target all 10 core kinases within the RAS/RAF/MAPK pathway which commonly drives cancer survival and proliferation. We find that by combining therapeutic siRNAs, we can selectively reduce the viability of RAS-dependent cancer cells (derived from melanoma, liver cancer and breast cancer) at greatly reduced dosage than is required with single siRNAs, and that the same combinatorial RNAs are able to kill cancer cells irrespective of the specific RAS hyperactivating mutation. Importantly, RAS-independent cells are unaffected by RNA treatment. Further, the cross-targeting RNA cocktail is still effective, even after cells have acquired resistance to a standard front-line anti-RAS therapy (vemurafenib). Lastly, we present transcriptomic analyses to demonstrate the reduced RNA dosage is associated with greater on-target and lower off-target effects than is seen with more traditional single-target approaches that necessitate the use of more RNA. Collectively, this work demonstrates the advantages of a combinatorial RNA approach to therapy as a means to reduce dosage, decrease off-target toxicity and provide broad-effectiveness through pathway-level targeting.