Down-regulation of laminin-binding integrins by 1 alpha,25-dihydroxyvitamin D3 in human melanoma cells in vitro.
In the present investigation the effect of 1 alpha,25(OH)2D3 on the expression of the integrin laminin receptor on the melanoma cell line SK-MEL-28 has been examined. The SK-MEL-28 cells were shown to contain high-affinity receptors for 1 alpha,25(OH)2D3 and cell proliferation was found to be inhibited in a dose-dependent manner in response to the hormone. Using monoclonal antibodies against the alpha 6-sub-unit of the integrin laminin receptor, immunocytochemistry demonstrated that exposure of cells to 1 alpha,25(OH)2D3 for 5 days caused a reduced staining intensity. This observation was further confirmed by dot blot analysis, where a dose-dependent decline of alpha 6 expression was obtained after treatment of the cells with 1 alpha,25(OH)2D3 for 6 days. FACS-analysis was performed in order to quantify this decline, and it was found that the level of alpha 6-subunits on the cell surface was reduced by more than 40%. Additional investigations including Northern blot analyses of poly(A)+RNA extracts also showed a dose-dependent reduction of alpha 6 mRNA. Interestingly, the decrease of alpha 6 expression on the surface of SK-MEL-28 melanoma cells was accompanied by a reduced ability of the cells to adhere to an artificial basement membrane. In conclusion, the present investigation shows that besides having an antiproliferative effect on the SK-MEL-28 melanoma cells, 1 alpha,25(OH)2D3 is also able to inhibit the surface expression of the alpha 6-subunit of the integrin laminin receptor. Moreover, the results strongly indicate that 1 alpha,25(OH)2D3 exerts its regulatory effect on the alpha 6-subunit at the transcriptional level rather than at the protein level.
Hansen
C M
CM
Department of Biochemistry, Leo Pharmaceutical Products, Ballerup, Denmark.
Madsen
M W
MW
Arensbak
B
B
Skak-Nielsen
T
T
Latini
S
S
Binderup
L
L
D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics; D000954:Antigens, Surface / Q000096:biosynthesis* / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002117:Calcitriol / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D039503:Integrin alpha6; D039121:Integrin alpha6beta1; D039161:Integrin alpha6beta4; D016023:Integrins / Q000096:biosynthesis* / Q000235:genetics; D007797:Laminin / Q000378:metabolism*; D008544:Melanocytes / Q000187:drug effects* / Q000378:metabolism; D008545:Melanoma / Q000473:pathology*; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D018167:Receptors, Calcitriol / Q000378:metabolism; D017474:Receptors, Laminin / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D000954:Antigens, Surface; D000970:Antineoplastic Agents; D006131:Growth Inhibitors; D039503:Integrin alpha6; D039121:Integrin alpha6beta1; D039161:Integrin alpha6beta4; D016023:Integrins; D007797:Laminin; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D018167:Receptors, Calcitriol; D017474:Receptors, Laminin; D002117:Calcitriol; C082908:integrin alpha7beta1