Abstract 3910: Identification of lead organic compounds active against stem cell-like neuroblastoma cells by high throughput screening

Abstract

Cancer stem cells (CSCs) are plastic in nature, a characteristic that hampers cancer therapeutics. We previously reported the establishment of induced neuroblastoma (NB) stem cells (iCSC), which were stable stem cell-like NB cells in sphere culture. These cells recapitulated the in vivo histological phenotypes of Large-Cell NB (LCN), the most aggressive and deadly subset of NB, including vesicular nuclei and two to three prominent nucleoli (PNAS Vol. 110: 6097-102 2013). In addition to the LCN phenotype, high-level expression MYC or MYCN is the consistent feature of the iCSC xenografts grown in immune-compromised mice. The goal of this study is to identify lead organic compounds active against NB iCSCs by high throughput screening. By using MTS assays, the SKNAS iCSC and the parental monolayer cells were used to screen the Prestwick Chemical Library®, containing 1200 FDA-approved small molecules. Growth suppressive compounds were defined as they exhibited cell survival reduction of greater than 80% compared to DMSO control. There were unexplored compounds with significant antineoplastic activity among existing antibacterial, antifungal, antiprotozoal, and anthelmintic compounds. Among the compounds screened, we identified a dozen of small molecules that were preferentially growth suppressive to the SKNAS iCSC over the monolayer cells. The secondary MTS assay confirmed so far that Chlorhexidine (antiseptic), Benzethonium (antiseptic) and Digoxin (cardiac glycoside) were potential anti-NB iCSC agents: they were more effective in suppressing growth of the SKNAS iCSC than the monolayer cells. In addition, these compounds exhibited MYC destabilizing activity in the SKNAS iCSC. Notably, JQ1, the recently identified MYC destabilizer, was less effective than Chlorhexidine, Benzethonium and Digoxin in suppressing growth of SKNAS iCSC. The above three compounds also showed the MYCN destabilizing effect in another pair of MYCN-amplified SKNBE(2)C iCSCs and SKNBE(2)C monolayer cells. We are currently completing characterization of the small molecules identified with focus on their anti- iCSC growth and anti-MYC/MYCN effects. This study would reveal specific pathways that regulate biological activities of the CSCs. In addition, it is a promising approach that could lead to development of safe and effective anti-cancer therapeutics not only for NB but also other cancer types. Citation Format: Naohiko Ikegaki, Kiira Ratia, Ruth Hsiao, Mariko M. Limpar, Sarah Lomahan, Xao X. Tang. Identification of lead organic compounds active against stem cell-like neuroblastoma cells by high throughput screening. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3910. doi:10.1158/1538-7445.AM2014-3910