Cancer subtype specific molecular variations dramatically affect patient responses to already existing treatments. For example, the phosphorylation status of many proteins that are involved in signal transduction pathways perturbed in cancer cells is extremely important in determining whether these cells are susceptible to killing by available cancer therapeutics. Therefore, differentially phosphorylated protein isoforms can be a particularly useful prognostic biomarker of drug response in the clinic. However, accurate detection and quantitative analysis of cancer-related phosphoproteins in tumors is limited by current technologies.

Using a novel, fully automated nanocapillary electrophoresis technology (CB1000TM) designed to separate protein molecules based on their isoelectric point, we are currently developing highly sensitive assays for reliable assessment of the phosphorylation status of cancer-related phosphoproteins in tumors, before and during drug treatment. We have already developed and optimized assays measuring all AKT, ERK and MEK isoforms and their respective phosphoisoforms using a single detection reagent method. Using these assays, we were able to measure levels of activated MEK1/2, ERK1/2 and AKT1/2/3 in cancer cell lines, mouse xenografts and patient FNAs using protein extracted from as few as 125 cells. We have already measured and characterized changes in the phosphorylation states of these targets before, during and after treatment with inhibitors of the PI3K pathway in breast cancer, and based on this data we are currently developing molecular profiles that predict response to available therapeutics.

Citation Information: Clin Cancer Res 2010;16(7 Suppl):B47