Progressive tumor formation in mice with conditional deletion of TGF-beta signaling in head and neck epithelia is associated with activation of the PI3K/Akt pathway.
The precise role of transforming growth factor (TGF)-beta signaling in head and neck squamous cell carcinoma (SCC) is not yet fully understood. Here, we report generation of an inducible head- and neck-specific knockout mouse model by crossing TGF-beta receptor I (Tgfbr1) floxed mice with K14-CreER(tam) mice. By applying tamoxifen to oral cavity of the mouse to induce Cre expression, we were able to conditionally delete Tgfbr1 in the mouse head and neck epithelia. On tumor induction with 7,12-dimethylbenz(a)anthracene (DMBA), 45% of Tgfbr1 conditional knockout (cKO) mice (n = 42) developed SCCs in the head and neck area starting from 16 weeks after treatment. However, no tumors were observed in the control littermates. A molecular analysis revealed an enhanced proliferation and loss of apoptosis in the basal layer of the head and neck epithelia of Tgfbr1 cKO mice 4 weeks after tamoxifen and DMBA treatment. The most notable finding of our study is that the phosphoinositide 3-kinase (PI3K)/Akt pathway was activated in SCCs that developed in the Tgfbr1 cKO mice on inactivation of TGF-beta signaling through Smad2/3 and DMBA treatment. These observations suggest that activation of Smad-independent pathways may contribute cooperatively with inactivation of Smad-dependent pathways to promote head and neck carcinogenesis in these mice. Our results revealed the critical role of the TGF-beta signaling pathway and its cross-talk with the PI3K/Akt pathway in suppressing head and neck carcinogenesis.
Bian
Yansong
Y
Functional Genomics Section, Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Cancer Institute, NIH, Bethesda, Maryland 20892-4330, USA.
Terse
Anita
A
Du
Juan
J
Hall
Bradford
B
Molinolo
Alfredo
A
Zhang
Pin
P
Chen
Wanjun
W
Flanders
Kathleen C
KC
Gutkind
J Silvio
JS
Wakefield
Lalage M
LM
Kulkarni
Ashok B
AB
D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002453:Cell Cycle; D049109:Cell Proliferation; D004789:Enzyme Activation; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D017353:Gene Deletion; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism
D015127:9,10-Dimethyl-1,2-benzanthracene; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; C000625842:Tgfbr1 protein, mouse