Andrew Pack

Introduction. Uveal Melanomas are a cancer of the melanocytes in the uveal tract of the eye, which is made up of the iris, choroid and ciliary body.¹ Virtually all uveal melanomas’s mechanism of pathogenesis is a mutation that activates a gene, GNAQ, which is involved in the GPCR pathway.² Uveal melanomas are relatively rare, with an incidence of 1-9 cases per million people per year.¹ The prognosis of uveal melanomas is relatively poor, with a 5 year 30% mortality and a 15 year 45% mortality.¹ This type of cancer is more common among people aged 50-70, those with fair skin, and those with a family history.¹ Uveal melanomas can be diagnosed by an ophthalmologist with a slit lamp.¹ Uveal melanomas most commonly metastasize to the liver, lungs and lymph nodes.^1,3 Currently uveal melanomas are treated with a variety of treatments including brachytherapy, enucleation, and checkpoint therapy.² Single Cell Sequencing was done to interrogate the highly heterogeneous tumor microenvironment, and to investigate why they had limited responsiveness to checkpoint therapy that worked better for cutaneous melanomas.⁴ Methodology. Single Cell Sequencing was conducted on cells from 8 primary and 3 metastatic samples.⁴ The metastatic aggressiveness of these tumors varied, where Class 1 tumors are generally characterized by low metastatic risk, and class 2 are generally characterized by higher metastatic risk.⁵ Results. A t-SNE plot was made from 1865 expressed RNA genes of 59,915 cells.⁴ Marker genes that were known for specific cell types allowed them to label these cells, i.e. NK cells, T cells, etc.⁴ Quantification of cells by type in each tumor sample was conducted.⁴ Ridge plots of the CD8+ T cell were created using Seurat, a R package, which showed that LAG3 was highly expressed, and PD-L1 and CTLA-4 were lower expresed.⁴ Immunohistochemistry confirmed that RNA expression levels of LAG3 correlated with expression of LAG3 protein.⁴ Conclusion. This provided more data on the heterogeneous environment of uveal melanomas, and provided rationale for a potential therapeutic target for checkpoint therapy: LAG3.^4’6 What makes LAG3 checkpoint therapy particularly promising is in other cancer models like chronic lymphocytic leukemia, LAG3 has been tested in dual LAG3/PD1 immune checkpoint therapy with good efficacy.⁷ In addition in a mice model, LAG3 immunotherapy has been able to cause regression of recurrent melanoma.⁸

1. Jager MJ, Shields CL, Cebulla CM, Abdel-Rahman MH, Grossniklaus HE, Stern MH, Carvajal RD, Belfort RN, Jia R, Shields JA, Damato BE. Uveal melanoma. Nat Rev Dis Primers. 2020 Apr 9;6(1):24. doi: 10.1038/s41572-020-0158-0. PMID: 32273508.
2. Smit KN, Jager MJ, de Klein A, Kiliҫ E. Uveal melanoma: Towards a molecular understanding. Progress in Retinal and Eye Research. 2020;75:100800. doi:10.1016/j.preteyeres.2019.100800.
3. Johansson, P.A., Brooks, K., Newell, F. et al. Whole genome landscapes of uveal melanoma show an ultraviolet radiation signature in iris tumours. Nat Commun 11, 2408 (2020). https://doi.org/10.1038/s41467-020-16276-8.
4. Durante, M.A., Rodriguez, D.A., Kurtenbach, S. et al. Single-cell analysis reveals new evolutionary complexity in uveal melanoma. Nat Commun 11, 496 (2020). https://doi.org/10.1038/s41467-019-14256-1.
5. Field MG, Durante MA, Anbunathan H, Cai LZ, Decatur CL, Bowcock AM, Kurtenbach S, Harbour JW. Punctuated evolution of canonical genomic aberrations in uveal melanoma. Nat Commun. 2018 Jan 9;9(1):116. doi: 10.1038/s41467-017-02428-w. PMID: 29317634; PMCID: PMC5760704.
6. Karlsson, J., Nilsson, L.M., Mitra, S. et al. Molecular profiling of driver events in metastatic uveal melanoma. Nat Commun 11, 1894 (2020). https://doi.org/10.1038/s41467-020-15606-0.
7. Wierz M, Pierson S, Guyonnet L, Viry E, Lequeux A, Oudin A, Niclou SP, Ollert M, Berchem G, Janji B, Guérin C, Paggetti J, Moussay E. Dual PD1/LAG3 immune checkpoint blockade limits tumor development in a murine model of chronic lymphocytic leukemia. Blood. 2018 Apr 5;131(14):1617-1621. doi: 10.1182/blood-2017-06-792267. Epub 2018 Feb 13. PMID: 29439955; PMCID: PMC5887766.
8. Andrews LP, Marciscano AE, Drake CG, Vignali DA. LAG3 (CD223) as a cancer immunotherapy target. Immunol Rev. 2017;276(1):80-96. doi:10.1111/imr.12519.