Identification and Characterization of Binding Target Proteins of Cancer Stem Cell Inhibitor Salinomycin in Human Neuroblastoma

• Main Author: Zhou, Shuang
• Format: Others
• Published: North Dakota State University 2015
• Online Access: http://hdl.handle.net/10365/25199

Salinomycin, a widely used anti-coccidial agent, was recently identified as a cancer stem cell (CSC) inhibitor from a library of 16,000 natural and commercial chemical compounds based on its highly selective inhibitory effect on breast CSCs, with more than 100-fold greater potency than paclitaxel. Salinomycin also exhibits cytotoxic effects on other types of cancer cells and CSCs and overcomes drug resistance. However, the exact mechanism of salinomycin, especially its direct binding target(s), and its effects on Neuroblastoma (NB) are yet not known. NB is a common solid tumor and a leading cause of mortality in children. Currently, 35% of patients with NB remain incurable. In addition, the majority survivors of NB suffer from long-term side effects of current therapies and are at risk for disease relapse or getting a second, different cancer. More effective therapies are pressingly needed. Since the existence of CSCs in human NB cell lines and NB tumors has been well documented, and has been closely associated with chemoresistance or tumor relapse, therapeutic targeting of NB CSCs may be a critical novel approach for NB therapy. Aiming to improve NB therapy, we examined the efficacy and mechanism of salinomycin in human NB cells. Our study showed that salinomycin markedly inhibits NB cell proliferation and tumorsphere formation. Treatment of salinomycin induced G2 cell cycle arrest with an up-regulation of Cyclin A and a down-regulation of p21 protein levels. We further identified Transcription intermediary factor 1-beta (TIF1β) and Nucleolin (NCL) as novel binding targets of salinomycin by using comprehensive methods, including chemical proteomics and functional genomics. We demonstrate that salinomycin induced phosphor-TIF1β mediated down-regulation of p53 and significantly suppressed the expression of CD34, a CSC marker, via disrupting the interaction of NCL with the CD34 promoter. Furthermore, by analyzing tumor samples data from a cohort of 498 NB patients, we found that elevated levels of TIF1β and NCL in NB are associated with a poor outcome. These results provide a therapeutic rationale for evaluating of both salinomycin and its binding proteins, TIF1β and NCL, in NB. === ND EPSCoR === National Institutes of Health (NIH) P20 RR020151 === NIGMS (P20 GM103505 and P30 GM103332-01) === NDSU Graduate School Doctoral Dissertation Fellowship