Altered trafficking of Fas and subsequent resistance to Fas-mediated apoptosis occurs by a wild-type p53 independent mechanism in esophageal adenocarcinoma.
BACKGROUND
Decreased cell-surface expression of Fas (CD95) results in resistance to Fas-mediated apoptosis in esophageal adenocarcinoma (EA). Because p53 is known to increase transcription of Fas and also may induce trafficking of the protein to the plasma membrane, we investigated whether the loss of wild-type (wt)-p53 function accounts for our previous findings.


METHODS
Surgical specimens of Barrett's Esophagus containing areas of dysplasia were immunostained for p53 and Fas protein expression. Three EA cell lines were transfected with a wt-p53 containing adenovirus to examine the effects of p53 overexpression. The p53 status of these EA cell lines was determined by sequence analysis.


RESULTS
Regions of dysplasia where p53 protein accumulation was observed corresponded to areas of loss of Fas expression. Sequence analysis of the p53 coding sequence in three EA cell lines (Seg-1, Bic-1, and Flo-1) that retain Fas protein within the cytoplasm, demonstrated that Seg-1 contained wt-p53, but mutations were found in Flo-1 and Bic-1 cell lines. Adenoviral transduction of the cell lines with wt-p53 resulted in cell growth arrest in Seg-1 and Bic-1 and induced cell death in Flo-1, but did not result in an increase in Fas protein expression, cell-surface expression, or restoration of sensitivity to Fas-mediated apoptosis.


CONCLUSIONS
These data suggest that decreased cell-surface expression of Fas and resistance to Fas-mediated apoptosis may occur independently of loss of wt p53 expression.
Mahidhara
Raja S
RS
Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Queiroz De Oliveira
Pierre E
PE
Kohout
Jaromir
J
Beer
David G
DG
Lin
Jiayuh
J
Watkins
Simon C
SC
Robbins
Paul D
PD
Hughes
Steven J
SJ
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D004938:Esophageal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D015972:Gene Expression Regulation, Neoplastic; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D051379:Mice; D010190:Pancreatic Neoplasms; D021381:Protein Transport / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D049452:Green Fluorescent Proteins