Haruna Takedaa,b, Alistair G. Rustc,d, Jerrold M. Warda, Christopher Chin Kuan Yewa, Nancy A. Jenkinsa,e and Neal G. Copelanda,e
a Division of Genomics and Genetics, Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore 138673
b Department of Pathology, School of Medicine, Kanazawa Medical University, Ishikawa 920-0293, Japan
c Experimental Cancer Genetics, Wellcome Trust Sanger Institute, Cambridge CB10 1HH, United Kingdom
d Tumour Profiling Unit, The Institute of Cancer Research, Chester Beatty Laboratories, London SW3 6JB, United Kingdom
e Cancer Research Program, Houston Methodist Research Institute, Houston, TX 77030
Published in PNAS on 22 March 2016.
Mutations in SMAD4 predispose to the development of gastrointestinal cancer, which is the third leading cause of cancer-related deaths. To identify genes driving gastric cancer (GC) development, we performed a Sleeping Beauty (SB) transposon mutagenesis screen in the stomach of Smad4+/− mutant mice. This screen identified 59 candidate GC trunk drivers and a much larger number of candidate GC progression genes. Strikingly, 22 SB-identified trunk drivers are known or candidate cancer genes, whereas four SBidentified trunk drivers, including PTEN, SMAD4, RNF43, and NF1, are known human GC trunk drivers. Similar to human GC, pathway analyses identified WNT, TGF-β, and PI3K-PTEN signaling, ubiquitin- mediated proteolysis, adherens junctions, and RNA degradation in addition to genes involved in chromatin modification and organization as highly deregulated pathways in GC. Comparative oncogenomic filtering of the complete list of SB-identified genes showed that they are highly enriched for genes mutated in human GC and identified many candidate human GC genes. Finally, by comparing our complete list of SB-identified genes against the list of mutated genes identified in five large-scale human GC sequencing studies, we identified LDL receptor-related protein 1B (LRP1B) as a previously unidentified human candidate GC tumor suppressor gene. In LRP1B, 129 mutations were found in 462 human GC samples sequenced, and LRP1B is one of the top 10 most deleted genes identified in a panel of 3,312 human cancers. SB mutagenesis has, thus, helped to catalog the cooperative molecular mechanisms driving SMAD4-induced GC growth and discover genes with potential clinical importance in human GC.
SB mutagenesis accelerates GC development in Smad4+/− mutant mice.
(A) Smad4KO:SB mice develop tumors earlier than Smad4KO mice (P < 0.01).
(B) Smad4KO:SB mice also develop more tumors per mouse in the stomach, jejunum, ileum, and colon than Smad4KO mice, but they do not develop more tumors per mouse in the duodenum.
(C–E) Histopathology of gastric lesions identified in Smad4KO:SB. C shows gastric intestinal metaplasia and inflammation.
D shows a gastric adenoma, and E illustrates a gastric adenocarcinoma. Co, colon; Duo, duodenum; Ile, ileum; Jej, jejunum; Sto, stomach. (Scale bars: C, 100 μm; D, 0.5 mm; E, 200 μm.)