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Original article
RSPO3 expands intestinal stem cell and niche compartments and drives tumorigenesis
  1. John Hilkens1,
  2. Nikki C Timmer1,
  3. Mandy Boer1,
  4. Gerjon J Ikink1,
  5. Matthias Schewe2,
  6. Andrea Sacchetti2,
  7. Martijn A J Koppens1,
  8. Ji-Ying Song3,
  9. Elvira R M Bakker1
  1. 1Department of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands
  2. 2Department of Pathology, Josephine Nefkens Institute, Erasmus Medical Centre, Rotterdam, The Netherlands
  3. 3Department of Experimental Animal Pathology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
  1. Correspondence to Dr Elvira R M Bakker, or Dr J Hilkens, Department of Molecular Genetics, Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX, The Netherlands; e.bakker{at}nki.nlj.hilkens{at}nki.nl

Abstract

Objective The gross majority of colorectal cancer cases results from aberrant Wnt/β-catenin signalling through adenomatous polyposis coli (APC) or CTNNB1 mutations. However, a subset of human colon tumours harbour, mutually exclusive with APC and CTNNB1 mutations, gene fusions in RSPO2 or RSPO3, leading to enhanced expression of these R-spondin genes. This suggested that RSPO activation can substitute for the most common mutations as an alternative driver for intestinal cancer. Involvement of RSPO3 in tumour growth was recently shown in RSPO3-fusion-positive xenograft models. The current study determines the extent into which solely a gain in RSPO3 actually functions as a driver of intestinal cancer in a direct, causal fashion, and addresses the in vivo activities of RSPO3 in parallel.

Design We generated a conditional Rspo3 transgenic mouse model in which the Rspo3 transgene is expressed upon Cre activity. Cre is provided by cross-breeding with Lgr5-GFP-CreERT2 mice.

Results Upon in vivo Rspo3 expression, mice rapidly developed extensive hyperplastic, adenomatous and adenocarcinomatous lesions throughout the intestine. RSPO3 induced the expansion of Lgr5+ stem cells, Paneth cells, non-Paneth cell label-retaining cells and Lgr4+ cells, thus promoting both intestinal stem cell and niche compartments. Wnt/β-catenin signalling was modestly increased upon Rspo3 expression and mutant Kras synergised with Rspo3 in hyperplastic growth.

Conclusions We provide in vivo evidence that RSPO3 stimulates the crypt stem cell and niche compartments and drives rapid intestinal tumorigenesis. This establishes RSPO3 as a potent driver of intestinal cancer and proposes RSPO3 as a candidate target for therapy in patients with colorectal cancer harbouring RSPO3 fusions.

  • CANCER
  • INTESTINAL STEM CELL
  • SIGNALING

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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