Discovery of Selective Inhibitors for Oncoprotein Kinases

Protein kinases is an important regulator in cellular signal transduction pathways. Overexpression of protein kinases are associated with many types of cancers. Therefore, designing cancer drugs that target protein kinases may hold great therapeutic benefits. A number of protein kinase drugs have been approved by the FDA since 2011. However, a majority of the protein kinase drugs approved are tyrosine kinase inhibitors and a small number are serine/threonine inhibitors. Hence, many oncoprotein kinases inhibitors have yet to be identified. Additionally, current protein kinase drugs are unselective and cancer cells have been shown to develop resistance to treatment. Thus, there is still a crucial need for selective protein kinase drugs for clinical use. The aims for this project are: (1) to identify and analyze oncoprotein kinases using data from public databases (2) to develop novel kinase inhibitors that inhibit multiple proteins within a single disease to increase efficiency and reduce the incidence of side effects, (3) and to validate identified inhibitors using enzymatic and cell-based assays. Our extensive experience in drug design and bioinformatics will allow us to achieve our goal of identifying novel inhibitors that inhibit multiple kinases in the same disease. Such inhibitors can potentially increase the therapeutic effect, reduce the probability of drug resistance and increase selectivity of inhibitors. Our method will include (1) comparing the expression levels of protein kinases in each cancer tissue to the corresponding normal tissue and identifying potential oncoprotein kinases, (2) using the molecular screening program iGEMDOCK to identify selective inhibitors that target multiple kinases within a single disease, (3) selecting top-ranked compounds for enzymatic and cell-based assays to demonstrate compound potency. Enzyme activity will be optimized by establishing a site-moiety map for candidate inhibitors. In addition, the development of protein kinase inhibitors will be conducted in collaboration with Dr. Shiow-Lin Pan (潘秀玲) of Taipei Medical University. In our preliminary results, we have identified six oncoprotein kinases. At least one of these are highly expressed in 14 types of cancer tissues. We identified 14 potential inhibitors for the six kinases using virtual screening. Cell-based assays revealed the inhibitors with an IC50<10μM, with three being on the nanomolar scale. Among the 14 inhibitors identified, NSC126466 and NSC13626 were selected for an enzymatic activity assay of 90 protein kinases. The results showed that NSC13626 can inhibit PAK2 and JAK2 in gastric cancer, making it a potential inhibitor for multi-target inhibition of protein kinases in gastric cancer. NSC126466 was shown to be highly specific and inhibited its target DYRK1B. Overexpression of DYRK1B is associated with bladder cancer. We will continue to screen for drug kinases and specific cancers. We believe that our skills in combining computational drugs and biomedical experiments will lead to identification of multi-target oncoprotein kinase drugs for cancer patients.