Natural product (-)-gossypol inhibits colon cancer cell growth by targeting RNA-binding protein Musashi-1.
Musashi-1 (MSI1) is an RNA-binding protein that acts as a translation activator or repressor of target mRNAs. The best-characterized MSI1 target is Numb mRNA, whose encoded protein negatively regulates Notch signaling. Additional MSI1 targets include the mRNAs for the tumor suppressor protein APC that regulates Wnt signaling and the cyclin-dependent kinase inhibitor P21(WAF-1). We hypothesized that increased expression of NUMB, P21 and APC, through inhibition of MSI1 RNA-binding activity might be an effective way to simultaneously downregulate Wnt and Notch signaling, thus blocking the growth of a broad range of cancer cells. We used a fluorescence polarization assay to screen for small molecules that disrupt the binding of MSI1 to its consensus RNA binding site. One of the top hits was (-)-gossypol (Ki = 476 ± 273 nM), a natural product from cottonseed, known to have potent anti-tumor activity and which has recently completed Phase IIb clinical trials for prostate cancer. Surface plasmon resonance and nuclear magnetic resonance studies demonstrate a direct interaction of (-)-gossypol with the RNA binding pocket of MSI1. We further showed that (-)-gossypol reduces Notch/Wnt signaling in several colon cancer cell lines having high levels of MSI1, with reduced SURVIVIN expression and increased apoptosis/autophagy. Finally, we showed that orally administered (-)-gossypol inhibits colon cancer growth in a mouse xenograft model. Our study identifies (-)-gossypol as a potential small molecule inhibitor of MSI1-RNA interaction, and suggests that inhibition of MSI1's RNA binding activity may be an effective anti-cancer strategy.
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Lan
L
Lan
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Carl
C
Appelman
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Amber R
AR
Smith
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA; School of Chemistry and Chemical Engineering, Southeast University, Nanjing, China.
Jia
J
Yu
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Sarah
S
Larsen
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Rebecca T
RT
Marquez
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Hao
H
Liu
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Xiaoqing
X
Wu
COBRE Protein Production Group, The University of Kansas, Lawrence, KS, USA.
Philip
P
Gao
High Throughput Screening Laboratory, The University of Kansas, Lawrence, KS, USA.
Anuradha
A
Roy
Bio-NMR Core Facility, The University of Kansas, Lawrence, KS, USA.
Asokan
A
Anbanandam
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA; Center for Bioinformatics, The University of Kansas, Lawrence, KS, USA.
Ragul
R
Gowthaman
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA; Center for Bioinformatics, The University of Kansas, Lawrence, KS, USA.
John
J
Karanicolas
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Roberto N
RN
De Guzman
Center of Biomedical Research Excellence, Center for Cancer Experimental Therapeutics, The University of Kansas, Lawrence, KS, USA.
Steven
S
Rogers
Center of Biomedical Research Excellence, Center for Cancer Experimental Therapeutics, The University of Kansas, Lawrence, KS, USA; Specialized Chemistry Center, The University of Kansas, Lawrence, KS, USA; Center for Chemical Methodologies and Library Development, The University of Kansas, Lawrence, KS, USA; Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS, USA.
Jeffrey
J
Aubé
School of Chemistry and Chemical Engineering, Southeast University, Nanjing, China.
Min
M
Ji
Department of Biological Sciences, Clemson University, Clemson, SC, USA.
Robert S
RS
Cohen
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA.
Kristi L
KL
Neufeld
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS, USA; Department of Radiation Oncology, The University of Kansas Cancer Center, Kansas City, KS, USA. Electronic address: xul@ku.edu.
Liang
L
Xu
D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006072:Gossypol / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009419:Nerve Tissue Proteins / Q000187:drug effects* / Q000378:metabolism; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000187:drug effects* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
C491297:MSI1 protein, human; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D006072:Gossypol
Colon cancer; Musashi-1; Notch; RNA binding protein; Wnt