Deciphering the Intricate Relationship Between Macrophages, Pigmentation, and Prognosis in Uveal Melanoma

Abstract

High pigmentation and the abundance of M2 macrophages have been identified as negative predictors in uveal melanoma (UM). Risk factors associated with UM that are prevalent in high-risk White populations are still present, although less common, in relatively low-risk Asian populations. Research indicates that proangiogenic M2 macrophages and monosomy 3 play significant roles in UM progression. Our aim was to investigate the impact of tumor-associated macrophages in UM and examine their correlation with monosomy 3 and pigmentation. Transmission electron microscopy was used to analyze the morphology of macrophages in UM. Forty UM samples underwent fluorescent in situ hybridization for monosomy 3 identification. Immunohistochemistry was done to assess M2/M1 macrophages on 82 UM tissue samples. IL-10 and IL-12 expressions were quantified in UM serum samples by enzyme-linked immunosorbent assay. The expression of all markers was correlated with pigmentation markers (tyrosinase-related protein 1, tyrosinase-related protein 2, silver protein, and microphthalmia-associated transcription factor). Prognostic outcomes were determined using the Cox proportional hazard model and log-rank tests. Increased expression of M2/M1 macrophages was observed in 31 UM cases, which correlated with the high expression of pigmentation markers. IL-10 concentration was high in UM cases. Monosomy 3 was evident in 50% of UM cases and significantly associated with increased immunoexpression of M2/M1 macrophages and pigmentation markers. Reduced metastasis-free survival was observed in patients with UM with high M2/M1 macrophage expression (P = .001). High pigmentation and increased M2 macrophage density could impact the tumor microenvironment in UM. This could contribute to ineffective antitumor immune responses in patients with UM. Our findings suggest avenues for developing novel therapeutic approaches to counteract these immunosuppressive effects in UM.

Keywords: monosomy 3; pigmentation; tumor-associated macrophages; uveal melanoma.