Caspase-3 expression is reduced, in the absence of cleavage, in terminally differentiated normal oral epithelium but is increased in oral squamous cell carcinomas and correlates with tumour stage.
Oral carcinomas are known to have a greater apoptotic index than normal oral epithelium, evident as shrinking cells with condensed chromatin. In this study, these morphologically apoptotic cells stained positively for cleaved (active) caspase-3. In normal oral epithelium, cleaved caspase-3 positive-cells were only rarely detected. The terminally differentiated surface epithelial layers did not express cleaved caspase-3. The caspase-3 pro-enzyme showed a gradient of expression in normal oral epithelium, decreasing with differentiation. No expression was detectable in surface epithelial layers. Lack of expression of the major 'executioner' caspase-3 may, at least in part, explain differences in morphology between terminally differentiated and apoptotic cells. In cancers of different tissue origins, caspase-3 pro-enzyme expression can be either increased or decreased compared with normal tissue counterparts. To determine how caspase-3 expression alters during oral carcinogenesis, caspase-3 expression was compared in 39 samples of normal oral epithelium and 54 oral squamous cell carcinomas. Squamous cell carcinomas had more intense caspase-3 staining than normal epithelium (p < 0.001). Moreover, within the oral squamous cell carcinoma series, there was significantly more intense nuclear and cytoplasmic staining with increasing STNMP stage (p = 0.017 and 0.03, respectively). This was a reflection of significant associations with site (S), palpable lymph nodes (N), and differentiation (P). Both caspase-3 staining intensity and the percentage of cells positive for caspase-3 were inversely associated with differentiation. Studies of the mechanisms by which high levels of caspase-3 expression are tolerated in oral carcinoma cells may identify targets that can be used to harness caspase-3 overexpression for therapeutic benefit.
Hague
Angela
A
Department of Oral and Dental Science, University of Bristol Dental School, Lower Maudlin Street, Bristol, BS1 2LY, UK. a.hague@bristol.ac.uk
Eveson
John W
JW
MacFarlane
Marion
M
Huntley
Suzanne
S
Janghra
Nari
N
Thavaraj
Selvam
S
D000368:Aged; D017209:Apoptosis / Q000502:physiology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D053148:Caspase 3; D020169:Caspases / Q000032:analysis*; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004792:Enzyme Precursors / Q000032:analysis; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D015603:Keratinocytes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000378:metabolism*; D009062:Mouth Neoplasms / Q000378:metabolism* / Q000473:pathology; D009367:Neoplasm Staging
D004792:Enzyme Precursors; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases