Smad2 and Smad3 Phosphorylated at Both Linker and COOH-Terminal Regions Transmit Malignant TGF-β Signal in Later Stages of Human Colorectal Cancer

Matsuzaki, Koichi; Kitano, Chiaki; Murata, Miki; Sekimoto, Go; Yoshida, Katsunori; Uemura, Yoshiko; Seki, Toshihito; Taketani, Shigeru; Fujisawa, Jun–ichi; Okazaki, Kazuichi

doi:10.1158/0008-5472.can-08-4203

Cited by 115 publications

(186 citation statements)

References 48 publications

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“…For the linker domains, all 5 relevant missense changes in SMAD2 and SMAD3 were predicted to be benign mirroring the results for SMAD4. A number of reports have implicated inappropriate phosphorylation of serine/threonine residues within the R-SMAD linker domains in the pathology of CRCs (44,45), but we found only one change (T184A) in the linker domain of SMAD2 that could represent a relevant change. Taken together, our data suggest that SMAD4, SMAD2, and SMAD3 are mutated in a similar manner with homologous MH1 and MH2 domain changes acting through analogous mechanisms to prevent the formation of activated complexes.…”

Section: Discussioncontrasting

confidence: 52%

SMAD2,SMAD3andSMAD4Mutations in Colorectal Cancer

et al. 2013

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Activation of the canonical TGF-b 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-XSer 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-b signaling pathway. Cancer Res; 73(2); 725-35. Ó2012 AACR.

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Section: Discussioncontrasting

confidence: 52%

SMAD2,SMAD3andSMAD4Mutations in Colorectal Cancer

et al. 2013

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“…The Smad proteins consist of conserved N-and Cterminal domains, separated by a divergent linker region. The Smad3 linker region containing four serine/threonine phosphorylation sites at Thr179, Ser204, Ser208, and Ser213 (10)(11)(12)(13)(14)(15)(16)(17)(18) can be phosphorylated by several kinases, such as the MAPK family and cyclin-dependent kinase (CDK) family (10)(11)(12)(13)(15)(16)(17)(18)(19)(20). These residues except Ser213 are subject to phosphorylation in response to TGFb (11,12,14).…”

Section: Introductionmentioning

confidence: 99%

Definition of Smad3 Phosphorylation Events That Affect Malignant and Metastatic Behaviors in Breast Cancer Cells

et al. 2014

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Smad3, a major intracellular mediator of TGFb signaling, functions as both a positive and negative regulator in carcinogenesis. In response to TGFb, the TGFb receptor phosphorylates serine residues at the Smad3 C-tail. Cancer cells often contain high levels of the MAPK and CDK activities, which can lead to the Smad3 linker region becoming highly phosphorylated. Here, we report, for the first time, that mutation of the Smad3 linker phosphorylation sites markedly inhibited primary tumor growth, but significantly increased lung metastasis of breast cancer cell lines. In contrast, mutation of the Smad3 C-tail phosphorylation sites had the opposite effect. We show that mutation of the Smad3 linker phosphorylation sites greatly intensifies all TGFb-induced responses, including growth arrest, apoptosis, reduction in the size of putative cancer stem cell population, epithelialmesenchymal transition, and invasive activity. Moreover, all TGFb responses were completely lost on mutation of the Smad3 C-tail phosphorylation sites. Our results demonstrate a critical role of the counterbalance between the Smad3 C-tail and linker phosphorylation in tumorigenesis and metastasis. Our findings have important implications for therapeutic intervention of breast cancer. Cancer Res; 74(21);

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“…The linker domain undergoes regulatory phosphorylation by mitogen-activated protein kinase (MAPK) pathways including extracellular signal-regulated kinase, c-Jun N-terminal kinase (JNK), p38 MAPK, and cyclin-dependent kinase (CDK) as well as glycogen synthase kinase 3-b (Fig. 1a, middle) [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

“…In cancer cells, however, Smad signaling itself drives pro-tumorigenic gene expression [44,45] and tumor-initiating stem cell behavior [46]. Linker phosphorylation can explain these long-standing paradoxes concerning Smad signaling, since such phosphorylation occurs apart from the canonical Smad signaling, instead promoting cell growth, invasion, and fibrosis via JNK and CDK pathways [23,27,28,32,47]. TGF-b can activate the Smad pathway via linker phosphorylation [28], as well as the non-Smad pathway, usually in parallel [7].…”

Section: Introductionmentioning

confidence: 99%