Extended Data Fig. 6: Analysis of Siglec-15 mRNA expression in human cancers.

a, The inverse correlation of mRNA expression levels between Siglec-15 and T cell signature genes (CD3E, IFNG, GZMA and GZMB) in bladder cancer by meta-analysis of TCGA databases. Pearson r score and P value are shown (n = 407 human samples). b–d, Validation of anti-Siglec-15 antibody clone PA5-48221. b, Representative quantitative immunofluorescence images of positive staining on 293T cells overexpressing Siglec-15 (293T-S15⁺, left panel) compared to mock transfected 293T cells (293T-S15-, right panel) (DAPI, blue and S15, red).Scale bars, 100 um. Data are representative of four independent experiments. c, QIF scores of 293T-S15⁺ and 293T-S15^– cell lines. Data are mean ± s.e.m. (n = 4 independent experiments). P values by two-tailed unpaired t-test. d, Comparison of Siglec-15 protein and RNA expression using RNAscope in situ detection by QIF. Pearson r score and P value are shown (n = 27 human samples). e, The relative levels of Siglec-15 mRNA in human cancer cell lines from the BioGPS database. f, Cell surface expression of Siglec-15 on LOX IMVI and U87 human cancer lines by staining with anti-Siglec-15 and control mAb and analyzed with flow cytometry. Data are representative of three independent experiments.