Transformation of human keratinocytes is characterized by quantitative and qualitative alterations of the T-16 antigen (Trop-2, MOv-16).
The regulation of synthesis and post-translational processing of the T-16 antigen, a human cell-surface glycoprotein of 50 to 60 kDa, was investigated in normal and transformed human keratinocytes in vitro. Normal keratinocytes of interfollicular and follicular origin were compared with squamous-cell-carcinoma lines, spontaneously immortalized keratinocytes, and SV-40 transformed keratinocytes. FACS analysis and radio-immunoprecipitation showed that the synthesis and expression of T-16 was 3- to 4-fold higher in transformed keratinocytes than in their normal counterparts. In normal keratinocytes, no quantitative differences were observed among freshly prepared cells, primary cultures and sub-cultures. In SDS-PAGE, a single broad band at 50 to 60 kDa was observed in normal keratinocytes, whereas 2 bands at 42 and 45 to 55 kDa were detected after transformation. Tunicamycin treatment of living cells and glycosidase digestion of immunopurified T-16 antigen revealed this molecular heterogeneity to be due to different N-glycosylation in normal and transformed keratinocytes. In pulse-chase experiments, 2 distinct precursor proteins at 38 and 42 kDa were detected in transformed keratinocytes, whereas in normal cells the 38-kDa signal was dramatically decreased. These findings indicate that quantitative and qualitative changes of T-16 mark the transformation process of human keratinocytes, showing similar post-translational alterations in all transformed populations investigated.
Schön
M P
MP
Department of Dermatology, University Medical Center Steglitz, Free University of Berlin, Germany.
Orfanos
C E
CE
D000951:Antigens, Neoplasm / Q000096:biosynthesis / Q000378:metabolism*; D000954:Antigens, Surface / Q000096:biosynthesis / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D015815:Cell Adhesion Molecules; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D000071858:Epithelial Cell Adhesion Molecule; D006031:Glycosylation; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D008562:Membrane Glycoproteins