Abstract
Purpose :
Uveal melanoma (UM) is the most common and lethal eye cancer in adults. Most benign nevi harbor the UM driver mutations in GNAQ/GNA11, suggesting additional genetic insults are required for UM initiation. While ultraviolet light, the major risk factor for skin melanoma, is filtered out by the ocular lens and cornea, the blue light (BL) spectra reaches the posterior of the eye. However, the exact role of BL in inducing uveal melanomagenesis is not well understood. In this study, we investigated the impacts of GNAQ mutation and BL irradiation in UM development.
Methods :
Using a solar simulator (TSS-156R, OAI), we analyzed the impact of acute (1 sun (1000 W/m2), 30 min) and chronic (0.3 sun, 3 hours/day, 4 days) BL exposure (400-500 nm) on UM cell lines, normal choroidal melanocytes (NCMs), and GNAQ-mutant CMs (a precursor cell for UM). NCMs were isolated from human donor eyes, and a GNAQ mutation (c.626A>T) was introduced by lentivirus to generate the mutant CMs. The proliferation rate and clonogenicity potential (i.e. soft agar and spheroid assay; in vitro clue of malignant transformation) of NCMs and mutant CMs were compared. The cell viability (CCK8 assay), reactive oxygen species (ROS, DCFDA assay) levels, and proteomic changes (analyzed by mass spectrometry and DAVID database) post BL exposure were assessed. Statistical analyses were performed by Student’s t-test. A P value < 0.05 was considered significant.
Results :
GNAQ-mutant CMs maintained the expression of melanocyte markers (Vimentin, MelanA, TRP1, HMB-45, S100) and displayed increased proliferation and clonogenicity potential compared to NCMs. Chronic BL irradiation reduced the viability of NCMs but not UM cell lines (i.e. 92.1, MP46 and OMM2.5). Acute BL exposure generated ~100-fold and 7-fold more ROS in 92.1 and NCMs, respectively, compared to non-treated cells. Proteomic analysis identified that BL caused endoplasmic reticulum stress and reduced DNA repair in NCMs, and significant oxidative stress in 92.1 cells.
Conclusions :
We report that BL affected the oxidative status of melanocytes and UM cells, which may lead to DNA damage that can accelerate mutation accumulation, thus initiating or facilitating UM development. In addition, GNAQ mutation and BL exposure trigger central clues involved in uveal melanomagenesis, suggesting that BL may represent an additional hit in the process of GNAQ-mutant nevi transformation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.