Destabilisation of dimeric 14-3-3 proteins as a novel approach to anti-cancer therapeutics.

// Joanna M. Woodcock 1 , Carl Coolen 1 , Katy L. Goodwin 1 , Dong Jae Baek 2 , Robert Bittman 2,** , Michael S. Samuel 1,3 , Stuart M. Pitson 1,3,* and Angel F. Lopez 1,3,* 1 Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA, Australia 2 Department of Chemistry and Biochemistry, Queens College of the City University of New York, Flushing, NY, USA 3 School of Medicine, Faculty of Health Sciences, University of Adelaide, Adelaide, SA, Australia * These authors have contributed Equally to this work ** Deceased Correspondence to: Joanna M. Woodcock, email: // Keywords : biochemistry, signal transduction, sphingosine, apoptosis, small molecules Received : March 24, 2015 Accepted : April 11, 2015 Published : May 04, 2015 Abstract 14-3-3 proteins play a pivotal role in controlling cell proliferation and survival, two commonly dysregulated hallmarks of cancers. 14-3-3 protein expression is enhanced in many human cancers and correlates with more aggressive tumors and poor prognosis, suggesting a role for 14-3-3 proteins in tumorigenesis and/or progression. We showed previously that the dimeric state of 14-3-3 proteins is regulated by the lipid sphingosine, a physiological inducer of apoptosis. As the functions of 14-3-3 proteins are dependent on their dimeric state, this sphingosine-mediated 14-3-3 regulation provides a possible means to target dimeric 14-3-3 for therapeutic effect. However, sphingosine mimics are needed that are not susceptible to sphingolipid metabolism. We show here the identification and optimization of sphingosine mimetics that render dimeric 14-3-3 susceptible to phosphorylation at a site buried in the dimer interface and induce mitochondrial-mediated apoptosis. Two such compounds, RB-011 and RB-012, disrupt 14-3-3 dimers at low micromolar concentrations and induce rapid down-regulation of Raf-MAPK and PI3K-Akt signaling in Jurkat cells. Importantly, both RB-011 and RB-012 induce apoptosis of human A549 lung cancer cells and RB-012, through disruption of MAPK signaling, reduces xenograft growth in mice. Thus, these compounds provide proof-of-principle for this novel 14-3-3-targeting approach for anti-cancer drug discovery.