Richard Spritz and colleagues present a genome-wide association study of autoimmune vitiligo in 4,680 cases and 39,586 controls and report 23 new risk loci. Their results highlight specific pathways, including immune response, apoptosis and melanocyte function, that may be important in the pathobiology of autoimmune vitiligo. Vitiligo is an autoimmune disease in which depigmented skin results from the destruction of melanocytes1, with epidemiological association with other autoimmune diseases2. In previous linkage and genome-wide association studies (GWAS1 and GWAS2), we identified 27 vitiligo susceptibility loci in patients of European ancestry. We carried out a third GWAS (GWAS3) in European-ancestry subjects, with augmented GWAS1 and GWAS2 controls, genome-wide imputation, and meta-analysis of all three GWAS, followed by an independent replication. The combined analyses, with 4,680 cases and 39,586 controls, identified 23 new significantly associated loci and 7 suggestive loci. Most encode immune and apoptotic regulators, with some also associated with other autoimmune diseases, as well as several melanocyte regulators. Bioinformatic analyses indicate a predominance of causal regulatory variation, some of which corresponds to expression quantitative trait loci (eQTLs) at these loci. Together, the identified genes provide a framework for the genetic architecture and pathobiology of vitiligo, highlight relationships with other autoimmune diseases and melanoma, and offer potential targets for treatment.

Richard Spritz and colleagues report genome-wide association analyses identifying 13 new susceptibility loci for generalized vitiligo. Their functional pathway analysis shows that many vitiligo susceptibility loci encode immunoregulatory proteins or melanocyte components. We previously reported a genome-wide association study (GWAS) identifying 14 susceptibility loci for generalized vitiligo. We report here a second GWAS (450 individuals with vitiligo (cases) and 3,182 controls), an independent replication study (1,440 cases and 1,316 controls) and a meta-analysis (3,187 cases and 6,723 controls) identifying 13 additional vitiligo-associated loci. These include OCA2-HERC2 (combined P = 3.80 × 10−8), MC1R (P = 1.82 × 10−13), a region near TYR (P = 1.57 × 10−13), IFIH1 (P = 4.91 × 10−15), CD80 (P = 3.78 × 10−10), CLNK (P = 1.56 × 10−8), BACH2 (P = 2.53 × 10−8), SLA (P = 1.58 × 10−8), CASP7 (P = 3.56 × 10−8), CD44 (P = 1.78 × 10−9), IKZF4 (P = 2.75 × 10−14), SH2B3 (P = 3.54 × 10−18) and TOB2 (P = 6.81 × 10−10). Most vitiligo susceptibility loci encode immunoregulatory proteins or melanocyte components that likely mediate immune targeting and the relationships among vitiligo, melanoma, and eye, skin and hair coloration.

Squamous cell carcinomas (SCCs) of the skin are sun-induced skin cancers that are particularly numerous in patients on T cell immunosuppression. We found that blood vessels in SCCs did not express E-selectin, and tumors contained few cutaneous lymphocyte antigen (CLA)⁺ T cells, the cell type thought to provide cutaneous immunosurveillance. Tumors treated with the Toll-like receptor (TLR)7 agonist imiquimod before excision showed induction of E-selectin on tumor vessels, recruitment of CLA⁺ CD8⁺ T cells, and histological evidence of tumor regression. SCCs treated in vitro with imiquimod also expressed vascular E-selectin. Approximately 50% of the T cells infiltrating untreated SCCs were FOXP3⁺ regulatory T (T reg) cells. Imiquimod-treated tumors contained a decreased percentage of T reg cells, and these cells produced less FOXP3, interleukin (IL)-10, and transforming growth factor (TGF)-β. Treatment of T reg cells in vitro with imiquimod inhibited their suppressive activity and reduced FOXP3, CD39, CD73, IL-10, and TGF-β by indirect mechanisms. In vivo and in vitro treatment with imiquimod also induced IL-6 production by effector T cells. In summary, we find that SCCs evade the immune response at least in part by down-regulating vascular E-selectin and recruiting T reg cells. TLR7 agonists neutralized both of these strategies, supporting their use in SCCs and other tumors with similar immune defects.

Secretory GTPases like Rab27B control vesicle exocytosis and deliver critical proinvasive growth regulators into the tumor microenvironment. The expression and role of Rab27B in breast cancer were unknown. Expression of green fluorescent protein (GFP) fused with wild-type Rab3D, Rab27A, or Rab27B, or Rab27B point mutants defective in GTP/GDP binding or geranylgeranylation, or transient silencing RNA to the same proteins was used to study Rab27B in estrogen receptor (ER)–positive human breast cancer cell lines (MCF-7, T47D, and ZR75.1). Cell cycle progression was evaluated by flow cytometry, western blotting, and measurement of cell proliferation rates, and invasion was assessed using Matrigel and native type I collagen substrates. Orthotopic tumor growth, local invasion, and metastasis were analyzed in mouse xenograft models. Mass spectrometry identified proinvasive growth regulators that were secreted in the presence of Rab27B. Rab27B protein levels were evaluated by immunohistochemistry in 59 clinical breast cancer specimens, and Rab3D, Rab27A, and Rab27B mRNA levels were analyzed by quantitative real-time polymerase chain reaction in 20 specimens. Statistical tests were two-sided. Increased expression of Rab27B promoted G ₁ to S phase cell cycle transition, proliferation and invasiveness of cells in culture, and invasive tumor growth and hemorrhagic ascites production in a xenograft mouse model (n = 10; at 10 weeks, survival of MCF-7 GFP- vs GFP-Rab27B–injected mice was 100% vs 62.5%, hazard ratio = 0.26, 95% confidence interval = 0.08 to 0.88, P = .03). Mass spectrometric analysis of purified Rab27B-secretory vesicles identified heat-shock protein 90α as key proinvasive growth regulator. Heat-shock protein 90α secretion was Rab27B-dependent and was required for matrix metalloproteinase-2 activation. All Rab27B-mediated functional responses were GTP- and geranylgeranyl-dependent. Presence of endogenous Rab27B mRNA and protein, but not of Rab3D or Rab27A mRNA, was associated with lymph node metastasis ( P < .001) and differentiation grade ( P = .001) in ER-positive human breast tumors. Rab27B regulates invasive growth and metastasis in ER-positive breast cancer cell lines, and increased expression is associated with poor prognosis in humans.