Developing Tools to Evaluate Structure-Function of c-Src Kinase.

Abstract

Kinase involvement in oncogenesis is generally due to overactive mutations and thus dysregulation of those signal transduction pathways. However, c-Src is unusual, it is frequently observed to be overexpressed in cancers, and yet cases of overactive c-Src mutations are rare. With the advancement of sequencing technology, additional somatic mutations of c-Src have been found in cancer tumors and human cancer cell lines. These clinical mutations have never been previously characterized. Whether or not these mutations are transformative remains to be seen. We hypothesized that these mutations could dysregulate c-Src function by disrupting its native conformational state. The work in Chapter 2 is our beginning effort in characterizing these new clinical mutations of c-Src. Chapter 3 and 4 takes on more of an application approach. Since there are studies throughout literature that implicates c-Src in cancer progression, we aimed to explore methods to make targeting c-Src more efficacious. The approach in Chapter 3 takes a selective c-Src inhibitor, designed in our lab, to look for inhibiting other protein targets which would work in synergy with c-Src inhibition. We found HDAC inhibitors to work in synergy, and with that information, we explored the design process for the first dual acting HDAC/c-Src inhibitor, compound 3.1 (c-Src Ki = 138 nM, HDAC1 Ki = 0.26 nM), which also demonstrated excellent potency against SK-BR3 breast cancer cell lines (0.2 uM) as well against 60 varying cancer cell lines in a National Cancer Institute screen (NCI-60). The goals of Chapter 4 are along the same lines except the approach was to improve the efficacy of dasatinib in triple negative breast cancer. The resulting inhibitor was a DFG-out dasatinib/imatinib hybrid, compound 4.1 which had unprecedented activity in triple negative breast cancer cell line MDA-MB-231 (GI50 = 6 nM) and low toxicity profile (HMEC GI50 = 1800 nM) compared to FDA approved c-Src inhibitor Dasatinib (MDA-MB-231, GI50 = 830 nM). This led us to find the increased in potency over dasatinib was the result of the new inhibitor acting as a dual p38/c-Src inhibitor and we describe the process of further improving this new dual acting inhibitor.