title: Transforming growth factor-alpha: a surrogate endpoint biomarker?
abstract: BACKGROUND
  Dysplastic oral leukoplakia (DOL) has been the index lesion in prevention trials for upper aerodigestive tract squamous cell carcinoma (SCC). Vitamin A derivatives, including 13-cis retinoic acid (13-CRA), have been used to treat DOL and to reduce the risk of subsequent SCC. Results from a trial of 13-CRA in patients with DOL are presented here. Transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor messenger RNA (mRNA) expression were studied to validate their use as surrogate endpoint biomarkers in prevention trials for SCC.
  
  
  METHODS
  In a prospective, randomized, double-blind trial of 13-CRA in 28 patients with DOL, TGF-alpha and epidermal growth factor receptor mRNA expression were analyzed in sequential biopsy specimens of DOL and of adjacent normal-appearing mucosa, utilizing a quantitative, competitive, reverse transcriptase polymerase chain reaction and were compared using the Wilcoxon signed-rank test for paired comparisons.
  
  
  RESULTS
  In biopsy specimens of DOL, TGF-alpha mRNA expression at baseline, but not baseline expression of epidermal growth factor receptor mRNA, was significantly elevated when compared with its expression in specimens from adjacent normal-appearing mucosa (p = 0.003). In patients randomized to 13-CRA who had > or = 50% clearance of DOL during treatment, significant modulation of TGF-alpha mRNA overexpression was seen after 6 months of treatment (p = 0.016). TGF-alpha mRNA overexpression at baseline predicted a subsequent response to 13-CRA (p 0.066).
  
  
  CONCLUSIONS
  The full extent of the association between TGF-alpha overexpression and the development of SCC is unknown. Evidence is presented in this article that TGF-alpha overexpression mediates the relationship between 13-CRA and DOL, but there is no direct evidence that it mediates the relationship between 13-CRA and the prevention of SCC. Determination of the extent to which TGF-alpha overexpression mediates this relationship and complete validation of TGF-alpha's role as a surrogate endpoint biomarker await the results of animal and human trials that utilize reduction in the incidence of SCC as their endpoint.
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Beenken
authors.forename: Richard
authors.initials: R
authors.lastname: Hockett
authors.forename: William
authors.initials: W
authors.lastname: Grizzle
authors.forename: Heidi L
authors.initials: HL
authors.lastname: Weiss
authors.forename: Allan
authors.initials: A
authors.lastname: Pickens
authors.forename: Marjorie
authors.initials: M
authors.lastname: Perloff
authors.forename: Winfred F
authors.initials: WF
authors.lastname: Malone
authors.forename: Kirby I
authors.initials: KI
authors.lastname: Bland
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000517:prevention & control; D018450:Disease Progression; D004311:Double-Blind Method; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D015474:Isotretinoin / Q000627:therapeutic use; D007972:Leukoplakia, Oral / Q000188:drug therapy* / Q000378:metabolism*; D008297:Male; D009062:Mouth Neoplasms / Q000517:prevention & control; D011446:Prospective Studies; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016211:Transforming Growth Factor alpha / Q000378:metabolism*
chemical_list: D014408:Biomarkers, Tumor; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D066246:ErbB Receptors; D015474:Isotretinoin