title: Loss of AXIN1 drives acquired resistance to WNT pathway blockade in colorectal cancer cells carrying RSPO3 fusions.
abstract: In colorectal cancer (CRC), WNT pathway activation by genetic rearrangements of RSPO3 is emerging as a promising target. However, its low prevalence severely limits availability of preclinical models for in-depth characterization. Using a pipeline designed to suppress stroma-derived signal, we find that RSPO3 "outlier" expression in CRC samples highlights translocation and fusion transcript expression. Outlier search in 151 CRC cell lines identified VACO6 and SNU1411 cells as carriers of, respectively, a canonical PTPRK(e1)-RSPO3(e2) fusion and a novel PTPRK(e13)-RSPO3(e2) fusion. Both lines displayed markedin vitroandin vivosensitivity to WNT blockade by the porcupine inhibitor LGK974, associated with transcriptional and morphological evidence of WNT pathway suppression. Long-term treatment of VACO6 cells with LGK974 led to the emergence of a resistant population carrying two frameshift deletions of the WNT pathway inhibitor AXIN1, with consequent protein loss. Suppression of AXIN1 in parental VACO6 cells by RNA interference conferred marked resistance to LGK974. These results provide the first mechanism of secondary resistance to WNT pathway inhibition.
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.|Department of Oncology, University of Torino, Candiolo, Torino, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Picco
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.|Department of Oncology, University of Torino, Candiolo, Torino, Italy.
authors.forename: Consalvo
authors.initials: C
authors.lastname: Petti
authors.affiliation: Department of Oncology, University of Torino, Candiolo, Torino, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Centonze
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.|Istituto Nazionale Biostrutture e Biosistemi - Consorzio Interuniversitario, Roma, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Torchiaro
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Crisafulli
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Novara
authors.affiliation: Department of Computer and Control Engineering, Politecnico di Torino, Turin, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Acquaviva
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy.|Department of Oncology, University of Torino, Candiolo, Torino, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Bardelli
authors.affiliation: Candiolo Cancer Institute - FPO IRCCS, Candiolo, Torino, Italy enzo.medico@unito.it.|Department of Oncology, University of Torino, Candiolo, Torino, Italy.
authors.forename: Enzo
authors.identifier: 0000-0002-3917-2438
authors.initials: E
authors.lastname: Medico
mesh_terms: D060466:Axin Protein / Q000172:deficiency*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000473:pathology*; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050939:Gene Fusion; D006801:Humans; D011719:Pyrazines / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D019699:Thrombospondins / Q000235:genetics*; D051153:Wnt Proteins / Q000378:metabolism; D060449:Wnt Signaling Pathway; D000098907:R-Spondins
chemical_list: D060466:Axin Protein; D004791:Enzyme Inhibitors; D011719:Pyrazines; D011725:Pyridines; D019699:Thrombospondins; D051153:Wnt Proteins; C555451:AXIN1 protein, human; C475438:RSPO3 protein, human; D000098907:R-Spondins; C586458:LGK974
keywords: R‐spondin; WNT pathway; colorectal cancer; gene fusion; targeted therapy