title: Mutation of p53 in head and neck squamous cell carcinoma correlates with Bcl-2 expression and increased susceptibility to cisplatin-induced apoptosis.
abstract: BACKGROUND
  The p53 protein, a well-known tumor suppressor that functions primarily as a transcription factor, initiates cell cycle arrest and apoptosis after genotoxic stress. The antiapoptotic regulator Bcl-2 is a downstream modulator of p53-induced apoptosis. Loss of function of the p53 tumor suppressor through mutation is an important event that contributes to cellular transformation. Mutation of p53 is one of the most common genetic alterations in squamous cell carcinomas of the head and neck (SCCHN). We hypothesized that p53 mutation is associated with Bcl-2 expression and susceptibility to apoptosis in SCCHN.
  
  
  METHODS
  Exons 5 to 8 of the p53 gene were sequenced in 22 SCCHN tumor samples and correlated with the Bcl-2 expression and apoptosis rates in these tumors. In addition, a Bcl-2-expressing SCCHN cell line, UMSCC74B, was stably transfected with a temperature-sensitive mutant p53 construct, and Bcl-2 expression levels were examined at the mutant and the wild-type temperatures.
  
  
  RESULTS
  Bcl-2 expression was inversely correlated with wild-type p53 status in SCCHN tumors (p = .05). Furthermore, there was a modest increase (1.7-fold) in apoptosis in the wild-type p53 tumors compared with mutant p53 SCCHN. Immunoblotting of UMSCC74B cells stably transfected with the temperature-sensitive mutant p53 construct demonstrated that shifting these cells to the mutant p53 temperature (39.5 degrees C) resulted in decreased expression of Bcl-2 compared with levels in cells grown at the wild-type p53 temperature (32.5 degrees C). Further investigation showed that SCCHN cells expressing predominantly mutant p53 and decreased Bcl-2 were more susceptible to cisplatin-induced apoptosis than vector-transfected controls (p < .0001).
  
  
  CONCLUSIONS
  These results suggest that p53 mutation directly modulates Bcl-2 expression and therefore susceptibility to chemotherapy-induced apoptosis in SCCHN cells in vitro.
authors.affiliation: Department of Otolaryngology, University of Pittsburgh School of Medicine and the University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Genevieve A
authors.initials: GA
authors.lastname: Andrews
authors.forename: Sichuan
authors.initials: S
authors.lastname: Xi
authors.forename: Rebecca G
authors.initials: RG
authors.lastname: Pomerantz
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Lin
authors.forename: William E
authors.initials: WE
authors.lastname: Gooding
authors.forename: Abbey L
authors.initials: AL
authors.lastname: Wentzel
authors.forename: Li
authors.initials: L
authors.lastname: Wu
authors.forename: David
authors.initials: D
authors.lastname: Sidransky
authors.forename: Jennifer Rubin
authors.initials: JR
authors.lastname: Grandis
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D002945:Cisplatin / Q000494:pharmacology; D003720:Densitometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D016158:Genes, p53 / Q000235:genetics*; D006258:Head and Neck Neoplasms / Q000235:genetics* / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D009154:Mutation; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D002945:Cisplatin