Utilizing the the natural Ubiquitin Proteasome System for targeted cancer treatment

The design of specific targeting reagents still remains the major goal in cancer treatment. A targeted cancer therapy was developed by us using cytotoxic molecules termed chimeric proteins. Chimeric proteins are composed of 2 protein moieties fused at the cDNA level. The targeting moiety is binding a specific receptor overexpressed on the target cells. Once bound, the chimeric protein is internalized into the cells, thus enabling the second moiety, the killing moiety, to exert its action. In this work we used human IL-2 as the targeting moiety, targeting activated T/B-cells. The killing moiety is Smurf2, a SMAD specific E3 ubiquitin protein ligase.

We hypothesize that upon entry of IL2-Smurf2 into cancerous cells, it will “force” degradation processes, leading to cell death. In this way the cancer cells will program their own death in a non-inflammatory path.

We designed and constructed the IL2-Smurf2 chimeric protein. A purification protocol was developed to produce an active chimeric protein. IL2-Smurf2 specifically enters target cancer cells and evoke downstream effects including degrading RNF20, a target protein of SMURF2; inducing caspase activity and eventually causing high rates of cell death via apoptosis. A control chimeric protein with a point mutation disrupting the E3 active site, has no effect on target cells, strengthening the role of Smurf2 as a novel killing moiety.

Components of the Ubiquitin Proteasome System, such as Smurf2, were as yet not utilized nor explored for targeted cancer therapy in the form of chimeric proteins, thus representing a novel approach for targeted cancer treatment.