Abstract
Purpose :
The association between uveal melanoma (UM) and ultraviolet light (UV) damage has yet to be conclusively demonstrated. Spleen tyrosine kinase (Syk), a non-receptor tyrosine kinase with anti-tumorigenic properties, has been shown to be upregulated under stressed conditions, such as following UV exposure. In the present study, we used Syk as a UV exposure marker and compared its expression in the conjunctiva and choroid of normal human eyes (NHE) and eyes containing UM to investigate the link between UV damage and UM. We also investigated basal Syk levels in conjunctival fibroblasts to assess their sensitivity to UV damage.
Methods :
Automated immunohistochemical staining against Syk was performed in 23 UM enucleated eyes and 34 NHE age-matched Eyebank eyes. A score was established by evaluating staining intensity (0–2) and extension (0–2); both values were added to generate an immunoreactive score (IRS; 0–4). Syk expression was evaluated in choroidal fibroblasts in all eyes. In order to determine if UM eyes were exposed to more UV, we compared Syk expression in choroidal fibroblasts from UM eyes and NHE. Moreover, we compared Syk levels in conjunctival fibroblasts to choroidal fibroblasts within groups. Unpaired t-test with Welch’s correction was used for statistical analysis.
Results :
No significant difference in Syk expression was identified between UM cases and NHE in conjunctival (P=0.8833) or choroidal fibroblasts (P=0.7344). Choroidal fibroblasts in UM-containing eyes showed significantly greater staining compared to conjunctival fibroblasts in the same UM-containing eyes (P=0.0078) and within NHE (P=0.0291). Only specimens with conjunctival and choroidal data were included in the analysis (UM, n = 18; NHE, n = 15).
Conclusions :
Herein, we showed that there were no significant differences in Syk expression between UM-harboring eyes and NHE. This suggests that UV may not be an important risk factor for UM development. Moreover, we found greater basal Syk expression in choroidal versus conjunctival fibroblasts. As Syk plays a protective role following UV damage, the lower levels identified in the conjunctival might, in part, explain the high frequency of UV-related lesions, such as pterygium, in this structure and not in other ocular tissues.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.