Figure 1.

Alterations of PD-L1/PD-L2 correlate with expression of PD-L1 in malignant B cells. (A) Representative FISH images of probes targeting PD-L1 and PD-L2, which lie adjacent on chromosome 9p24.1, and a centromeric region of chromosome 9 (CEP9, aqua) hybridized against individual malignant cell nuclei highlighted by 4′,6-diamidino-2-phenylindole, showing PD-L1/PD-L2 polysomy, copy gain, amplification, and rearrangement (original magnification, ×100). (B) Waterfall plot showing individual TCRLBCL cases (x-axis) and the proportion of malignant cells with the indicated PD-L1/PD-L2 alteration (y-axis); r, relapsed/refractory cases; arrow, 4 cases with high-level amplifications; #, a case with a productive PD-L2 rearrangement (verified by PD-L2 IHC, panel D). (C) Comparison of the proportion of cases with PD-L1/PD-L2 relative gain (ie, copy gain or amplification) across cases of TCRLBCL (n = 33, red), cHL (n = 108, blue),¹³ and DLBCL-NOS (n = 21, gray). (D) Representative IHC demonstrating nuclear PAX5 (red) and membranous PD-L1 (brown) coexpression by a malignant B cell in a case of TCRLBCL with PD-L1/PD-L2 amplification (left), and representative IHC demonstrating membranous PD-L2 expression (brown, PAX5-staining was not performed) by a malignant B cell in a case of TCRLBCL, demonstrating rearrangement of PD-L2 (right) (original magification, ×100). (E) Waterfall plot showing individual TRLBCL cases (x-axis) and malignant cell-specific PD-L1 H-score (y-axis). The corresponding genetic classification for each case is indicated. (F) Comparison of PD-L1 H-scores for individual cases (● and ▲) displayed according to those with PD-L1/PD-L2 relative gain (ie, amplification or copy gain; n = 21) vs those without (n = 12). Four cases where >75% of tumor nuclei showed PD-L1/PD-L2 amplification are designated with triangles. (G) Comparison of malignant tumor cell PD-L1 H-scores for cases of TCRLBCL (n = 33, red), cHL (n = 106, blue),¹³ and DLBCL-NOS (n = 20, gray). For box-and-whisker plots (F, G) the median (line), 25th and 75th percentiles (boxes), and extreme values (whiskers) are indicated. Statistical comparisons by the 2-sided Mann-Whitney U test (F, G) and Fisher’s exact test with Bonferroni correction for multiple comparisons (C).