title: Differences in Smad4 expression in human papillomavirus type 16-positive and human papillomavirus type 16-negative head and neck squamous cell carcinoma.
abstract: The SMADs are a group of interrelated proteins that mediate transforming growth factor beta (TGF-beta) signaling. Upon TGF-beta binding the TGF-beta type I receptor phosphorylates Smad2 and Smad3, which then complex with Smad4 and translocate to the nucleus, with subsequent activation of target genes. Disruption of TGF-beta signaling is thought to contribute to the development of head and neck squamous cell carcinomas (HNSCC). Alterations in the function of the DPC4/Smad4 tumor suppressor gene have been found to inactivate TGF-beta signaling in several tumor types. For example, DPC4/Smad4 is lost or mutated in colorectal, pancreatic, and esophageal cancers. In addition, DPC4/Smad4 transcriptional activity and TGF-beta ability to inhibit DNA synthesis is blocked by the E7 protein of the human papillomavirus type 16 (HPV16) in cervical carcinoma cell lines. HPV16 infection is a risk factor for the development of a subset of HNSCC. This study was undertaken to investigate a potential correlation between expression of components of the TGF-beta signaling pathway and HPV16 status in HNSCC tumors. We examined the expression of TGF-beta signaling proteins Smad2, Smad2-P, and Smad4 by immunohistochemistry in 27 HPV16-negative and 16 HPV16-positive HNSCCs. We compared the expression patterns and assessed their relationship to HPV16 status. No significant differences were detected between HPV16-positive and HPV16-negative tumors in the expression of Smad2 and Smad2-P. Smad4 expression, however, was decreased in 56% of the HPV16-positive tumors and in 39% of HPV16-negative tumors. This difference was statistically significant (P = 0.01) suggesting that loss of Smad4 expression may be involved in HPV16-induced carcinogenesis of HNSCC.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of Puerto Rico School of Medicine, San Juan, Puerto Rico. abaez@rcm.upr.edu
authors.forename: Adriana
authors.initials: A
authors.lastname: Báez
authors.forename: Alan
authors.initials: A
authors.lastname: Cantor
authors.forename: Sharon
authors.initials: S
authors.lastname: Fonseca
authors.forename: Maria
authors.initials: M
authors.lastname: Marcos-Martinez
authors.forename: Linda A
authors.initials: LA
authors.lastname: Mathews
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Muro-Cacho
authors.forename: Teresita
authors.initials: T
authors.lastname: Muñoz-Antonia
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D004279:DNA, Viral / Q000235:genetics; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D005260:Female; D006258:Head and Neck Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009856:Oncogene Proteins, Viral / Q000235:genetics; D027383:Papillomaviridae / Q000235:genetics / Q000254:growth & development; D050725:Papillomavirus E7 Proteins; D030361:Papillomavirus Infections / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D016133:Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics; D015398:Signal Transduction; D051901:Smad4 Protein; D015534:Trans-Activators / Q000096:biosynthesis*; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; C059731:oncogene protein E7, Human papillomavirus type 16