Abstract C42: Quantitative high-throughput efficacy profiling of hedgehog/GLI pathway antagonists in inflammatory breast cancer

The primary objective of this study was to profile a panel of GLI pathway antagonists in inflammatory breast cancer (IBC) cell models for effects on cell growth and viability. Introduction: IBC, representing ∼5% of breast cancers in the USA, is a unique form of locally advanced breast cancer characterized by rapid progression and a highly invasive nature intrinsic to the tumor. IBC is not easily detected by mammograms or ultrasounds with detection typically after the cancer has spread. IBC patients have a 5 year survival rate of less than 50%, significantly less than patients with non-IBC breast cancer (85%), and IBC accounts for ∼15% of all breast cancer deaths. IBC affects young, African-American, Arab-American and American-Indian women at a higher rate than in other groups[1; 2; 3]. A recent analysis of SEER data showed an increase in IBC incidence associated with decreasing socioeconomic position[4]. Despite polychemotherapy regimens, women with IBC continue to have worse survival outcomes than non-IBC breast cancer patients and current strategies for targeting IBC are limited. The downstream transcription factor GLI1, an essential marker for hedgehog (Hh) pathway activation, has emerged as a therapeutic target for several cancers including breast cancer. We have demonstrated that siRNA downregulation of GLI1 expression in IBC reduced proliferation and migration[5]. Experimental Procedures: We employed a high throughput (HT) approach to profile a panel of GLI antagonists in an IBC model (SUM149, a basal type). To assess drug effects on proliferation we utilized an automated and validated 384-well cell-based MTT assay [6]. Compounds were screened in a secondary assay using high-content imaging of nuclear count following Hoechst staining as an alternative measure of cell proliferation. Results: A panel of Hh/GLI pathway antagonists was assembled based on literature surveys and formatted in 384-well plates. To obtain pharmacological information from the screening data, we employed a titration-based screening paradigm, quantitative HTS (qHTS) where compounds were screened at multiple concentrations. A subset of GLI antagonists were identified as having effects on IBC cell proliferation. Conclusion: Several agents showed efficacy in in vitro IBC cancer models demonstrating that GLI inhibitors may be a valid therapeutic approach for targeting GLI-dependent IBC cancers. Funded in part by DOD/CDMRP IDEA W81XWH-13-1-0141(BC121850) (KP Williams) [1] W.F. Anderson, C. Schairer, B.E. Chen, K.W. Hance, P.H. Levine, Epidemiology of inflammatory breast cancer (IBC). Breast disease 22 (2006) 9-23. [2] W.A. Woodward, M. Cristofanilli, Inflammatory breast cancer. Seminars in Radiation Oncology 19 (2009) 256-265. [3] K.A. Hirko, A.S. Soliman, M. Banerjee, J. Ruterbusch, J.B. Harford, R.M. Chamberlain, J.J. Graff, S.D. Merajver, K. Schwartz, Characterizing inflammatory breast cancer among Arab Americans in the California, Detroit and New Jersey Surveillance, Epidemiology and End Results (SEER) registries (1988–2008). SpringerPlus 2 (2013). [4] J.A. Schlichting, A.S. Soliman, C. Schairer, M. Banerjee, L. Rozek, D. Schottenfeld, J.B. Harford, S.D. Merajver, Association of Inflammatory and Non-Inflammatory Breast Cancer with Socioeconomic Characteristics in the Surveillance, Epidemiology, and End Results Database, 2000-2007. Cancer Epidemiol. Biomark. Prev. (2011) DOI:10.1158/1055-9965.EPI-1111-0853. [5] Z. Thomas, W. Gibson, J. Sexton, K. Aird, S. Ingram, A. Aldrich, H. Lyerly, G. Devi, K. Williams, Targeting GLI1 expression in human inflammatory breast cancer cells enhances apoptosis and attenuates migration. Br. J. Cancer 104 (2011) 1575-1586. [6] K.P. Williams, J.L. Allensworth, S.M. Ingram, G.R. Smith, A.J. Aldrich, J. Z Sexton, G. R Devi, Quantitative high-throughput efficacy profiling of approved oncology drugs in inflammatory breast cancer models of acquired drug resistance and re-sensitization. Cancer Lett. 337 (2013) 77-89. Citation Format: Helen Oladapo, Shalonda Ingram, Amy Stefanowicz, Gayathri Devi, Kevin Williams. Quantitative high-throughput efficacy profiling of hedgehog/GLI pathway antagonists in inflammatory breast cancer. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr C42. doi:10.1158/1538-7755.DISP13-C42