Hoot KE, Lighthall J, Han G, Lu SL, Li A, Ju W, Kulesz-Martin M, Bottinger E, Wang XJKeratinocyte-specific Smad2 ablation results in increased epithelial-mesenchymal transition during skin cancer formation and progression. J Clin Invest 118: 2722-2732

Department of Cell and Developmental Biology, Oregon Health & Science University, Portland, Oregon 97239-2999, USA.
Journal of Clinical Investigation (Impact Factor: 13.22). 08/2008; 118(8):2722-32. DOI: 10.1172/JCI33713
Source: PubMed


TGF-beta and its signaling mediators, Smad2, -3, and -4, are involved with tumor suppression and promotion functions. Smad4-/- mouse epidermis develops spontaneous skin squamous cell carcinomas (SCCs), and Smad3-/- mice are resistant to carcinogen-induced skin cancer; however, the role of Smad2 in skin carcinogenesis has not been explored. In the present study, we found that Smad2 and Smad4, but not Smad3, were frequently lost in human SCCs. Mice with keratinocyte-specific Smad2 deletion exhibited accelerated formation and malignant progression of chemically induced skin tumors compared with WT mice. Consistent with the loss of Smad2 in poorly differentiated human SCCs, Smad2-/- tumors were poorly differentiated and underwent epithelial-mesenchymal transition (EMT) prior to spontaneous Smad4 loss. Reduced E-cadherin and activation of its transcriptional repressor Snail were also found in Smad2-/- mouse epidermis and occurred more frequently in Smad2-negative human SCCs than in Smad2-positive SCCs. Knocking down Snail abrogated Smad2 loss-associated EMT, suggesting that Snail upregulation is a major mediator of Smad2 loss-associated EMT. Furthermore, Smad2 loss led to a significant increase in Smad4 binding to the Snail promoter, and knocking down either Smad3 or Smad4 in keratinocytes abrogated Smad2 loss-associated Snail overexpression. Our data suggest that enhanced Smad3/Smad4-mediated Snail transcription contributed to Smad2 loss-associated EMT during skin carcinogenesis.

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    • "One week later, TPA (5 µg in 50 µl acetone) was applied topically to skin twice a week for 20 weeks for tumor promotion. The number of tumors per mouse was recorded weekly [21]. "
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    ABSTRACT: Smad Anchor for Receptor Activation (SARA) has been reported as a critical role in TGF-b signal transduction by recruiting non-activated Smad2/3 to the TGF-b receptor and ensuring appropriate subcellular localization of the activated receptorbound complex. However, controversies still exist in previous reports. In this study, we describe the expression of two SARA isoforms, SARA1 and SARA2, in mice and report the generation and characterization of SARA mutant mice with FYVE domain deletion. SARA mutant mice developed normally and showed no gross abnormalities. Further examination showed that the TGF-b signaling pathway was indeed altered in SARA mutant mice, with the downregulation of Smad2 protein expression. The decreasing expression of Smad2 was caused by enhancing Smurf2-mediated proteasome degradation pathway. However, the internalization of TGF-b receptors into the early endosome was not affected in SARA mutant mouse embryonic fibroblasts (MEFs). Moreover, the downregulation of Smad2 in SARA mutant MEFs was not sufficient to disrupt the diverse cellular biological functions of TGF-b signaling, including growth inhibition, apoptosis, senescence, and the epithelial-to-mesenchymal transition. Our results indicate that SARA is not involved in the activation process of TGF-b signal transduction. Using a two-stage skin chemical carcinogenesis assay, we found that the loss of SARA promoted skin tumor formation and malignant progression. Our data suggest a protective role of SARA in skin carcinogenesis.
    PLoS ONE 09/2014; 9(8):e105299. DOI:10.1371/journal.pone.0105299 · 3.23 Impact Factor
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    • "PPARb/d coordinates a pro‐tumoural gene program in advanced actinic keratosis Skin tumour growth is associated with increased proliferation and migratory potential of keratinocytes, and in this process, Src promotes epithelial cell dedifferentiation during the epithelial‐to‐ mesenchymal transition (EMT). The EMT might also be regulated by other direct or indirect PPARb/d‐modulated signalling pathways such as the Tgfb1/SMAD pathway, which could act on Src expression (Glick, 2012; Han et al, 2005; Hoot et al, 2008; Martins et al, 2009; Nakamura & Tokura, 2011; Newkirk et al, 2007). Thus, we examined the ability of PPARb/d to enhance this transition by measuring expression of EMT markers in actinic keratosis with moderate atypia (grade II) of wild‐type and Pparb/d À/À mice, including growth factors, transcription factors, cytoskeletal and cell surface markers, extracellular matrix proteins and regulators (Fig 6A). "
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    ABSTRACT: Although non-melanoma skin cancer (NMSC) is the most common human cancer and its incidence continues to rise worldwide, the mechanisms underlying its development remain incompletely understood. Here, we unveil a cascade of events involving peroxisome proliferator-activated receptor (PPAR)β/δ and the oncogene Src, which promotes the development of ultraviolet (UV)-induced skin cancer in mice. UV-induced PPARβ/δ activity, which directly stimulated Src expression, increased Src kinase activity and enhanced the EGFR/Erk1/2 signalling pathway, resulting in increased epithelial-to-mesenchymal transition (EMT) marker expression. Consistent with these observations, PPARβ/δ-null mice developed fewer and smaller skin tumours, and a PPARβ/δ antagonist prevented UV-dependent Src stimulation. Furthermore, the expression of PPARβ/δ positively correlated with the expression of SRC and EMT markers in human skin squamous cell carcinoma (SCC), and critically, linear models applied to several human epithelial cancers revealed an interaction between PPARβ/δ and SRC and TGFβ1 transcriptional levels. Taken together, these observations motivate the future evaluation of PPARβ/δ modulators to attenuate the development of several epithelial cancers.
    EMBO Molecular Medicine 02/2014; 6(1). DOI:10.1002/emmm.201302666 · 8.67 Impact Factor
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    • "Bio-Plex® multiplex phosphoprotein analyses of the tumor lysates also showed a reduction in phosphorylation of Akt-Thr308, PDGFRα-Tyr754, and STAT1-Tyr701, but unexpectedly, an increase in phospho-Smad2-Ser465/467 and phospho-VEGFR2-Tyr1175 in the oseltamivir phosphate-treated cohort compared with the untreated cohort. Indeed, the Smad2 protein that is recruited to TGF-β receptors through its interaction with the SMAD anchor for receptor activation protein to mediate the TGF-β signal has been reported to function as a suppressor of prostate66 and breast67 epithelial cancer cells as well as a suppressor of EMT during formation and progression of skin cancer.68,69 The integration of Smad signaling into epithelial cell plasticity is eloquently reviewed by Sundqvist et al70 and Miyazono et al.71 Indeed, there is an intimate connection between Smad proteins and AP-1 components that determines TGF-β-induced invasion of breast cancer cells, and may involve Smad2/3-Fra1 complexes in the activation of the Smad/AP-1-dependent TGF-β-induced invasion program.72 "
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    ABSTRACT: Resistance to drug therapy, along with high rates of metastasis, contributes to the low survival rate in patients diagnosed with pancreatic cancer. An alternate treatment for human pancreatic cancer involving targeting of Neu1 sialidase with oseltamivir phosphate (Tamiflu®) was investigated in human pancreatic cancer (PANC1) cells with acquired resistance to cisplatin and gemcitabine. Its efficacy in overcoming the intrinsic resistance of the cell to chemotherapeutics and metastasis was evaluated. Microscopic imaging, immunocytochemistry, immunohistochemistry, and WST-1 cell viability assays were used to evaluate cell survival, morphologic changes, and expression levels of E-cadherin, N-cadherin, and VE-cadherin before and after treatment with oseltamivir phosphate in PANC1 cells with established resistance to cisplatin, gemcitabine, or a combination of the two agents, and in archived paraffin-embedded PANC1 tumors grown in RAGxCγ double mutant mice. Oseltamivir phosphate overcame the chemoresistance of PANC1 to cisplatin and gemcitabine alone or in combination in a dose-dependent manner, and disabled the cancer cell survival mechanism(s). Oseltamivir phosphate also reversed the epithelial-mesenchymal transition characteristic of the phenotypic E-cadherin to N-cadherin changes associated with resistance to drug therapy. Low-dose oseltamivir phosphate alone or in combination with gemcitabine in heterotopic xenografts of PANC1 tumors growing in RAGxCγ double mutant mice did not prevent metastatic spread to the liver and lung. Therapeutic targeting of Neu1 sialidase with oseltamivir phosphate at the growth factor receptor level disables the intrinsic signaling platform for cancer cell survival in human pancreatic cancer with acquired chemoresistance. These findings provide evidence for oseltamivir phosphate (Tamiflu) as a potential therapeutic agent for pancreatic cancer resistant to drug therapy.
    OncoTargets and Therapy 01/2014; 7:117-34. DOI:10.2147/OTT.S55344 · 2.31 Impact Factor
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