Colorectal cancer cells display chaperone dependency for the unconventional prefoldin URI1

// Kamil Andrzej Lipinski *, 1 , Christian Britschgi *, 1 , Karen Schrader *, 1 , Yann Christinat 1 , Lukas Frischknecht 1 , Wilhelm Krek 1 1 Institute of Molecular Health Sciences, ETH Zurich, 8093 Zurich, Switzerland * These authors have contributed equally to this work Correspondence to: Wilhelm Krek, e-mail: wilhelm.krek@biol.ethz.ch Keywords: URI1, prefoldin, p53, chaperone dependency, colorectal cancer Received: October 24, 2015     Accepted: March 28, 2016     Published: April 18, 2016 ABSTRACT Chaperone dependency of cancer cells is an emerging trait that relates to the need of transformed cells to cope with the various stresses associated with the malignant state. URI1 (unconventional prefoldin RPB5 interactor 1) encodes a member of the prefoldin (PFD) family of molecular chaperones that acts as part of a heterohexameric PFD complex, the URI1 complex (URI1 C ), to promote assembly of multiprotein complexes involved in cell signaling and transcription processes. Here, we report that human colorectal cancer (CRCs) cell lines demonstrate differential dependency on URI1 and on the URI1 partner PFD STAP1 for survival, suggesting that this differential vulnerability of CRC cells is directly linked to URI1 C chaperone function. Interestingly, in URI1-dependent CRC cells, URI1 deficiency is associated with non-genotoxic p53 activation and p53-dependent apoptosis. URI1-independent CRC cells do not exhibit such effects even in the context of wildtype p53. Lastly, in tumor xenografts, the conditional depletion of URI1 in URI1-dependent CRC cells was, after tumor establishment, associated with severe inhibition of subsequent tumor growth and activation of p53 target genes. Thus, a subset of CRC cells has acquired a dependency on the URI1 chaperone system for survival, providing an example of ‘non-oncogene addiction’ and vulnerability for therapeutic targeting.