RNA binding protein RBM3 increases β-catenin signaling to increase stem cell characteristics in colorectal cancer cells.
Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States. It arises from loss of intestinal epithelial homeostasis and hyperproliferation of the crypt epithelium. In order to further understand the pathogenesis of CRC it is important to further understand the factors regulating intestinal epithelial proliferation and more specifically, regulation of the intestinal epithelial stem cell compartment. Here, we investigated the role of the RNA binding protein RBM3 in stem cell homeostasis in colorectal cancers. Using a doxycycline (Dox) inducible RBM3 overexpressing cell lines HCT 116 and DLD-1, we measured changes in side population (SP) cells that have high xenobiotic efflux capacity and increased capacity for self-renewal. In both cell lines, RBM3 induction showed significant increases in the percentage of side population cells. Additionally, we observed increases in spheroid formation and in cells expressing DCLK1, LGR5 and CD44Hi. As the Wnt/β-catenin signaling pathway is important for both physiologic and cancer stem cells, we next investigated the effects of RBM3 overexpression on β-catenin activity. RBM3 overexpression increased levels of nuclear β-catenin as well as TCF/LEF transcriptional activity. In addition, there was inactivation of GSK3β leading to decreased β-catenin phosphorylation. Pharmacologic inhibition of GSK3β using (2'Z,3'E)-6-Bromoindirubin-3'-oxime (BIO) also recapitulates the RBM3 induced β-catenin activity. In conclusion, we see that RNA binding protein RBM3 induces stemness in colorectal cancer cells through a mechanism involving suppression of GSK3β activity thereby enhancing β-catenin signaling. © 2015 Wiley Periodicals, Inc.
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas.
Anand
A
Venugopal
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas.
Dharmalingam
D
Subramaniam
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas.
Julia
J
Balmaceda
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas.
Badal
B
Roy
Department of Cancer Biology, The University of Kansas Medical Center, Kansas City, Kansas.
Dan A
DA
Dixon
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas.
Shahid
S
Umar
Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas.
Scott J
SJ
Weir
Department of Molecular and Integrative Physiology, The University of Kansas Medical Center, Kansas City, Kansas. sanant@kumc.edu.
Shrikant
S
Anant
D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D004318:Doxycycline / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism; D045325:HCT116 Cells; D006801:Humans; D014411:Neoplastic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D051153:Wnt Proteins / Q000378:metabolism; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism*
C495270:CTNNB1 protein, human; C099506:RBM3 protein, human; D016601:RNA-Binding Proteins; D051153:Wnt Proteins; D051176:beta Catenin; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D004318:Doxycycline
CD44; DCLK1; GSK3β; LGR5; Wnt signaling; cancer stem cells