R-Spondin chromosome rearrangements drive Wnt-dependent tumour initiation and maintenance in the intestine

Abstract

Defining the genetic drivers of cancer progression is a key in understanding disease biology and developing effective targeted therapies. Chromosome rearrangements are a common feature of human malignancies, but whether they represent bona fide cancer drivers and therapeutically actionable targets, requires functional testing. Here, we describe the generation of transgenic, inducible CRISPR-based mouse systems to engineer and study recurrent colon cancer-associated EIF3E–RSPO2 and PTPRK–RSPO3 chromosome rearrangements in vivo. We show that both Rspo2 and Rspo3 fusion events are sufficient to initiate hyperplasia and tumour development in vivo, without additional cooperating genetic events. Rspo-fusion tumours are entirely Wnt-dependent, as treatment with an inhibitor of Wnt secretion, LGK974, drives rapid tumour clearance from the intestinal mucosa without effects on normal intestinal crypts. Altogether, our study provides direct evidence that endogenous Rspo2 and Rspo3 chromosome rearrangements can initiate and maintain tumour development, and indicate a viable therapeutic window for LGK974 treatment of RSPO-fusion cancers.

RSPO2 gene rearrangement: a powerful driver of β-catenin activation in liver tumours

“…Interestingly, the EIF3E–RSPO2 fusion was reported to be sufficient to initiate WNT-dependent tumour development in a CRISPR-based murine colon cancer model, and the WNT secretion inhibitor LGK974 could drive rapid tumour clearance in this model 41. Thus, inhibition of WNT secretion (eg, using a porcupine inhibitor) might be a promising target for the treatment of hepatic RSPO2-activated tumours, and our molecular diagnostic approach might serve as companion diagnostic to select HCC patients that may benefit from such a precision medicine concept.…”

Discovery of chemical probes that suppress Wnt/β‐catenin signaling through high‐throughput screening

“…38 An in vivo study reported that LGK974 diminished/eradicated tumors carrying RSPO fusions from the intestinal mucosa without effects on normal intestinal crypts. 39 In addition, LGK974 prevented proliferation and induced differentiation of RNF43-mutant pancreatic adenocarcinoma in xenograft models. 40 Currently, a phase I clinical trial (Clinicaltrials.gov ID NCT01351103) of LGK974 for patients with malignancies of histological origin carrying genetic alterations upstream in the Wnt signaling pathway (eg, RNF43 mutation or RSPO fusion) is underway.…”

“…Another potent PORCN inhibitor, LGK974, was discovered by the screening of ~2 400 000 compounds using a TCF/LEF reporter assay, where Wnt3a‐secreting cells were cocultured with mouse Leydig TM3 cells expressing SuperTOPFlash for the activation of the Wnt pathway . An in vivo study reported that LGK974 diminished/eradicated tumors carrying RSPO fusions from the intestinal mucosa without effects on normal intestinal crypts . In addition, LGK974 prevented proliferation and induced differentiation of RNF43 ‐mutant pancreatic adenocarcinoma in xenograft models .…”

Sizing up human brain evolution

“…Finally, it will be interesting to evaluate LGRindependent, RSPO-mediated WNT signalling in cancer. Chromosomal abnormalities that lead to activation of RSPO2 or RSPO3 have been shown to drive WNT-dependent colon tumours 14 . Szenker-Ravi and colleagues' demonstration that these two RSPOs can modulate WNT activity independent of LGR adds a twist to these findings, and should prompt scientists to look for cancer-causing mutations in RSPO2 evolutionary model.…”