Expression of RPE65, a putative receptor for plasma retinol-binding protein, in nonmelanocytic skin tumours.
BACKGROUND
In a recent report we described RPE65, a protein originally characterized in retinal pigment epithelium, to be expressed in normal human epidermis. RPE65 is suspected to be involved in cellular uptake of retinol which is transported in the bloodstream complexed with plasma retinol-binding protein.


OBJECTIVE
To evaluate protein and mRNA expression of RPE65 in actinic keratosis (AK), squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) compared with normal skin.


METHODS
RPE65 mRNA expression in skin tumours relative to normal skin of the respective donor was studied by real-time polymerase chain reaction in AK (n = 15), invasive SCC (n = 30) and BCC (n = 18). A peptide-specific anti-RPE65 antibody was used for immunohistochemical staining of formalin-fixed and paraffin-embedded tissue sections of the respective tumours.


RESULTS
RPE65 mRNA expression was reduced in AK. A highly significant reduction of RPE65 mRNA was observed in invasive SCC relative to normal skin of the respective donors. Immunohistochemistry revealed a continuous staining of basal and suprabasal keratinocytes in normal human epidermis. RPE65 in AK shown by immunohistochemical staining was reduced and quite irregular, whereas invasive SCC revealed no staining of tumour cells with the anti-RPE65 antibody. RPE65 mRNA values were elevated, whereas immunohistochemical staining for RPE65 protein was heterogeneous in BCC.


CONCLUSIONS
These results suggest progressive downregulation of RPE65 from AK to invasive SCC.
Hinterhuber
G
G
Department of Dermatology, Division of General Dermatology, University of Vienna, School of Medicine, Währinger Gürtel 19-20, A-1090 Vienna, Austria. gabriele.hinterhuber@meduniwien.ac.at
Cauza
K
K
Dingelmaier-Hovorka
R
R
Diem
E
E
Horvat
R
R
Wolff
K
K
Foedinger
D
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002280:Basal Cell Carcinoma / Q000378:metabolism* / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins; D015536:Down-Regulation; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007124:Immunoenzyme Techniques; D007642:Keratosis / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D054839:Retinol-Binding Proteins, Plasma; D012878:Skin Neoplasms / Q000378:metabolism* / Q000473:pathology; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase
D002352:Carrier Proteins; D005136:Eye Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D012177:Retinol-Binding Proteins; D054839:Retinol-Binding Proteins, Plasma; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase