title: SMAD2, SMAD3 and SMAD4 mutations in colorectal cancer.
abstract: Activation of the canonical TGF-β signaling pathway provides growth inhibitory signals in the normal intestinal epithelium. Colorectal cancers (CRCs) frequently harbor somatic mutations in the pathway members TGFBR2 and SMAD4, but to what extent mutations in SMAD2 or SMAD3 contribute to tumorigenesis is unclear. A cohort of 744 primary CRCs and 36 CRC cell lines were sequenced for SMAD4, SMAD2, and SMAD3 and analyzed for allelic loss by single-nucleotide polymorphism (SNP) microarray analysis. Mutation spectra were compared between the genes, the pathogenicity of mutations was assessed, and relationships with clinicopathologic features were examined. The prevalence of SMAD4, SMAD2, and SMAD3 mutations in sporadic CRCs was 8.6% (64 of 744), 3.4% (25 of 744), and 4.3% (32 of 744), respectively. A significant overrepresentation of two genetic hits was detected for SMAD4 and SMAD3, consistent with these genes acting as tumor suppressors. SMAD4 mutations were associated with mucinous histology. The mutation spectra of SMAD2 and SMAD3 were highly similar to that of SMAD4, both in mutation type and location within the encoded proteins. In silico analyses suggested the majority of the mutations were pathogenic, with most missense changes predicted to reduce protein stability or hinder SMAD complex formation. The latter altered interface residues or disrupted the phosphorylation-regulated Ser-Ser-X-Ser motifs within SMAD2 and SMAD3. Functional analyses of selected mutations showed reductions in SMAD3 transcriptional activity and SMAD2-SMAD4 complex formation. Joint biallelic hits in SMAD2 and SMAD3 were overrepresented and mutually exclusive to SMAD4 mutation, underlining the critical roles of these three proteins within the TGF-β signaling pathway.
authors.affiliation: Ludwig Colon Cancer Initiative Laboratory, Ludwig Institute for Cancer Research, Department of Surgery, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Nicholas I
authors.initials: NI
authors.lastname: Fleming
authors.forename: Robert N
authors.initials: RN
authors.lastname: Jorissen
authors.forename: Dmitri
authors.initials: D
authors.lastname: Mouradov
authors.forename: Michael
authors.initials: M
authors.lastname: Christie
authors.forename: Anuratha
authors.initials: A
authors.lastname: Sakthianandeswaren
authors.forename: Michelle
authors.initials: M
authors.lastname: Palmieri
authors.forename: Fiona
authors.initials: F
authors.lastname: Day
authors.forename: Shan
authors.initials: S
authors.lastname: Li
authors.forename: Cary
authors.initials: C
authors.lastname: Tsui
authors.forename: Lara
authors.initials: L
authors.lastname: Lipton
authors.forename: Jayesh
authors.initials: J
authors.lastname: Desai
authors.forename: Ian T
authors.initials: IT
authors.lastname: Jones
authors.forename: Stephen
authors.initials: S
authors.lastname: McLaughlin
authors.forename: Robyn L
authors.initials: RL
authors.lastname: Ward
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Hawkins
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Ruszkiewicz
authors.forename: James
authors.initials: J
authors.lastname: Moore
authors.forename: Hong-Jian
authors.initials: HJ
authors.lastname: Zhu
authors.forename: John M
authors.initials: JM
authors.lastname: Mariadason
authors.forename: Antony W
authors.initials: AW
authors.lastname: Burgess
authors.forename: Dana
authors.initials: D
authors.lastname: Busam
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhao
authors.forename: Robert L
authors.initials: RL
authors.lastname: Strausberg
authors.forename: Peter
authors.initials: P
authors.lastname: Gibbs
authors.forename: Oliver M
authors.initials: OM
authors.lastname: Sieber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D009154:Mutation; D051899:Smad2 Protein / Q000235:genetics*; D051900:Smad3 Protein / Q000235:genetics*; D051901:Smad4 Protein / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: C497782:SMAD2 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta