Abstract 2087: A novel Btk tyrosine kinase inhibitor, CTN06, as a potential candidate agent for breast cancer treatment.
Authors: Su Chih-Ming , Chuang Chin-Nien , Wu Alexander , Wang Liang-Shun , Lee Wei-Hwa , Wu Chih-Hsiung , Lam Kit , Kung Hsing-Jien , Yeh Chi-Tai 
Published: August 2014

Backgrounds: Btk family kinases are non-receptor tyrosine kinases which are involved in the regulation of diverse cellular processes such as growth, survival and migration. Btk up-regulation has been shown to contribute to oncogenesis of myeloid malignacies. However its functions in solid tumors have not been explored due to its prominent expression in B cells. In this study, we present the first evidence that Btk overexpression contributes to breast carcinogenesis.

Material and Methods: CTN06-treated and BTK silenced cells were subjected to an Affimetrix human Genome U133A 2.0 microarray analysis for a global examination of Btk's functions in epithelial carcinogenesis. Signaling cascades which were altered by CTN06 treatment include STAT3, mTOR, S6K and Wnt/β-catenin. In vitro proliferation, migration/invasion assays were employed to demonstrate CTN06-mediated anti-cancer effects. RNA interference experiments were performed to show Btk's contribution to breast carcinogenesis and metastasis. Finally, xenograft mouse model was used to demonstrate the effects of CTN06 and the down-regulation of Btk on breast tumorigenesis.

Results: Our preliminary data indicates that Btk is aberrantly expressed in various breast cancer cell lines and tissues but particularly in cells of invasive phenotype. These findings prompted us to further explore the role of Btk in breast cancer carcinogenesis. Using available structural models, our team has developed a collection of small molecule inhibitors for Btk and shown that one of them, CTN06, prominently inhibited the growth and migration of different breast cancer cell lines. Interestingly, CTN06 also appeared to be a potent autophagy inducer in the highly invasive and triple-negative MDA-MB-231 cells. Based on these premises and Btk's participation in several signaling cascades such as Src, PI3K, PLCγ and PLC, we hypothesize that Btk overexpression confers a growth and/or survival advantage for breast cancer cells; Btk inhibitors (CTN06) should effectively suppress breast cancer development by negatively modulating Btk-related networks and be evaluated for clinical use. We have obtained promising results not only in vitro cell line models but also in vivo animal xenograft experiments to demonstrate its efficacy and safety profile.

Conclusions: We demonstrated for the first time that Btk overexpression is detected in breast cancer cells particularly in metastatic MDA-MB-231 cells and Btk-specific inhibitor CTN06 effectively suppressed both tumor growth and metastasis via negatively modulating the aforementioned signaling cascades in vitro and in vivo.

Citation Format: Chih-Ming Su, Chin-Nien Chuang, Alexander Wu, Liang-Shun Wang, Wei-Hwa Lee, Chih-Hsiung Wu, Kit Lam, Hsing-Jien Kung, Chi-Tai Yeh. A novel Btk tyrosine kinase inhibitor, CTN06, as a potential candidate agent for breast cancer treatment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2087. doi:10.1158/1538-7445.AM2013-2087