Immune expression and inhibition of heat shock protein 90 in uveal melanoma.
OBJECTIVE
To examine the immunohistochemical profile of heat shock protein 90 (Hsp90) in uveal melanoma and the cytotoxicity of an Hsp90 inhibitor, 17-allylamino-17-demethoxygeldanamycin (17-AAG), in uveal melanoma cell lines.


METHODS
Hsp90 expression was determined by immunohistochemistry in 44 paraffin-embedded sections of primary human uveal melanoma and in five uveal melanoma cell lines (92.1, OCM-1, MKT-BR, SP6.5, and UW-1). Sulforhodamine B-based proliferation assay was used to compare uveal melanoma cell growth with a range of concentrations of 17-AAG. Changes in cell migration, invasion, cell cycle fractions, and apoptotic activity were also evaluated. Expression of intracellular proteins was determined by Western blot analysis after 17-AAG exposure.


RESULTS
Immunohistochemical expression of Hsp90 was identified in 68% of the paraffin-embedded sections and significantly associated with largest tumor dimension (P = 0.03). 17-AAG significantly reduced the proliferation rates of uveal melanoma cell lines, with concentrations of 100 to 0.1 micromol/L. 17-AAG also significantly reduced the migratory and invasive capabilities of uveal melanoma cell lines. Cell cycle analysis showed that 17-AAG induced accumulations of cells in G(1). Caspase-3 protease activity analysis, a marker for apoptosis, showed a significant increase after drug exposure. The cytotoxic effect of 17-AAG was associated with decreased levels of phosphorylated Akt and cyclin-dependent kinase 4.


CONCLUSIONS
The immunohistochemical expression of Hsp90 in uveal melanoma indicates worse prognosis. To the best of our knowledge, this is the first report showing the inhibitory effect on uveal melanoma cells using 17-AAG to target Hsp90. Therefore, Hsp90 may be used as a potential target for treatment of patients with uveal melanoma.
Faingold
Dana
D
Department of Ophthalmology and Pathology, The McGill University Health Center and Henry C. Witelson Ocular Pathology Laboratory, Montreal, Quebec, Canada. faingolddana@yahoo.com
Marshall
Jean-Claude
JC
Antecka
Emilia
E
Di Cesare
Sebastian
S
Odashiro
Alexandre N
AN
Bakalian
Silvin
S
Fernandes
Bruno F
BF
Burnier
Miguel N
MN
D016227:Benzoquinones / Q000494:pharmacology; D002453:Cell Cycle / Q000276:immunology; D045744:Cell Line, Tumor; D002465:Cell Movement; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007150:Immunohistochemistry; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008545:Melanoma / Q000276:immunology*; D014604:Uveal Neoplasms / Q000276:immunology*
D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; C112765:tanespimycin