Immune expression and inhibition of HSP90 in uveal melanoma

Purpose: To examine the immunohistochemical profile of Hsp90 in uveal melanoma and the effects of Hsp90 inhibitor 17-AAG, in uveal melanoma cell lines. Methods: Hsp90 expression was studied in 44 sections of human uveal melanoma and in five uveal melanoma cell lines (92.1, OCM-1, MKTBR, SP6.5 and UW-1). Sulfurhodamine-B based proliferation assay was assessed with a range of concentrations of 17-AAG. Changes in cell migration and invasion were evaluated in vitro in the presence or absence of 17-AAG. Cell cycle fractions were determined by flow cytometry and the caspase 3 protease activity was detected using the BD ApoAlertTM Caspase Colorimetric Assay. Expression of intracellular proteins was determined by Western blot analysis. Results: Immunohistochemical expression of Hsp90 was identified in 68 % of the paraffin embedded sections and was significantly associated with largest tumor dimension. A statistically significant reduction on proliferation rate of uveal melanoma cell lines was observed with drug concentrations of 100 μM to 1 μM and also a reduction of their migratory and invasive capabilities. Exposure to 17-AAG induced accumulations of cells in G1 and loss of cells in S phase and also a significant increase in Caspase 3 protease activity. The cytotoxic effect of 17-AAG was associated with decreased levels of phospho-AKT after 24 h exposure to the drug. Conclusions: The immunohistochemical expression of Hsp90 in uveal melanoma indicates worse prognosis. Inhibition of HSP90 function by 17-AAG had an effect on cell motility and invasive potential, inducing cell cycle arrest and promoting apoptosis. Further trials in uveal melanoma models should be undertaken to study the effect of 17 AAG to target Hsp90 in vivo.