Squamous cell carcinoma and mammary abscess formation through squamous metaplasia in Smad4/Dpc4 conditional knockout mice.
Smad4 is a central mediator for TGFbeta signals, which play important functions in many biological processes. To study the role of Smad4 in mammary gland development and neoplasia, we disrupted this gene in mammary epithelium using a Cre-loxP approach. Smad4 is expressed in the mammary gland throughout development; however, its inactivation did not cause abnormal development of the gland during the first three pregnancies. Instead, lack of Smad4 gradually induced cell proliferation, alveolar hyperplasia and transdifferentiation of mammary epithelial cells into squamous epithelial cells. Consequently, all mutant mice developed squamous cell carcinoma and/or mammary abscesses between 5 and 16 months of age. We demonstrated that absence of Smad4 resulted in beta-catenin accumulation at onset and throughout the process of transdifferentiation, implicating beta-catenin, a key component of the Wnt signaling pathway, in the development of squamous metaplasia in Smad4-null mammary glands. We further demonstrated that TGFbeta1 treatment degraded beta-catenin and induced epithelial-mesenchymal transformation in cultured mammary epithelial cells. However, such actions were blocked in the absence of Smad4. These findings indicate that TGFbeta/Smad4 signals play a role in cell fate maintenance during mammary gland development and neoplasia.
Li
Wenmei
W
Genetics of Development and Disease Branch, NIDDK, NIH, 10/9N105, 10 Center Drive, Bethesda, MD 20892, USA.
Qiao
Wenhui
W
Chen
Lin
L
Xu
Xiaoling
X
Yang
Xiao
X
Li
Dan
D
Li
Cuiling
C
Brodie
Steven G
SG
Meguid
Michael M
MM
Hennighausen
Lothar
L
Deng
Chu-Xia
CX
D000038:Abscess / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002454:Cell Differentiation / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004817:Epidermis / Q000033:anatomy & histology / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D004848:Epithelium / Q000473:pathology / Q000502:physiology*; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism / Q000473:pathology*; D008679:Metaplasia; D051379:Mice; D018345:Mice, Knockout; D011247:Pregnancy; D015398:Signal Transduction; D051901:Smad4 Protein; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism; D051176:beta Catenin
C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C497796:SMAD4 protein, human; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D051176:beta Catenin