Fig 2: Nectin4 inhibits NK cytotoxicity via TIGIT. (A, C) IL2 secretion by parental BW (A, C), (A) BW-TIGIT and (C) BW-DNAM1 cells. IL2 secretion was determined by ELISA (od 650 nm) following incubation with control anti-TIGIT or anti-DNAM1 antibodies (left in a and C) or with PVR expressing cells (right in a and C). (B, D) IL2 secretion of parental BW (B, D), (B) BW-TIGIT and (D) BW-DNAM1 cells. IL2 secretion was determined by ELISA (od 650 nm) following incubation with Raji cells transfected either with an empty vector (Raji E) as a control, or with Nectin4 (Raji N4). Figure shows one representative experiment out of 3 performed. *P<0.05. (E) FACS staining of Raji cells overexpressing Nectin4 with TIGIT-Ig. TIGIT-Ig was preincubated with no antibody (left), with a control mAb (anti-CD99 mAb clone 12E7, middle) or with anti-TIGIT blocking antibody (mAb #4 generated as described previously,14 right). Black line histograms represent TIGIT-Ig binding. Gray filled histograms represent background staining of the secondary antibody only. (F) Mean fluorescence intensity (MFI) values of the TIGIT-Ig staining shown in (E) relative to NO antibody staining, *p<2×10-4. (G) [35S] methionine-labeled Raji cells transfected either with an empty vector as control (Raji empty—gray) or with Nectin4 (Raji Nectin4—black), were incubated for 5 hours with NK cells. NK cells were preincubated with no antibody (left), with a control antibody (anti-CD99 mAb clone 12E7, middle) or with an anti-TIGIT antibody (mAb #4 generated as described previously,14 right). The effector to target (E:T) ratios are indicated on the x-axis. Figure shows one representative experiment out of three performed. Shown is the relative average killing ±SD, *p<0.05. FACS, fluorescence-activated cell sorting; IL2, interleukin-2; NK, natural killer; NS, not significant.

Fig 3: Novel checkpoint inhibitor anti-Nectin4 antibodies block TIGIT binding. (A, B) FACS staining of Raji cells transfected either with an empty vector (gray histograms) or with Nectin4 over-expression (black histograms). Gray filled histograms represent background staining of secondary antibody only. Cells were stained with anti-Nectin4 mAb clone .01 (A) or clone .05 (B). (C, D) FACS staining with TIGIT-Ig of Raji overexpressing Nectin4 with (black histograms) or without (gray histograms) preincubation with anti-Nectin4 mAb clone .01 (C) or clone .05 (D). Gray, filled histograms represent background staining. Figures show one representative experiment out of three performed. Graph depicting the mean fluorescence intensity values of the stainings appears in online supplementary figure 3a–d. (E) Avidity quantification between Nectin4-Ig and anti-Nectin4 mAb clone .01 and clone .05 using MST. Measurements were repeated with at least three independent protein preparations. FACS, fluorescence-activated cell sorting; MST, microscale thermophoresis

Fig 4: TIGIT but not DNAM1, CD112R or CD96—interacts with Nectin4. (A) FACS staining of IL-2 activated primary NK cells with Nectin4-Ig. Gray filled histogram represents background staining with secondary antibody only; black line histogram represents specific binding as indicated. (B–F) FACS staining of Raji cells transfected either with an empty vector as control (gray histograms) or with Nectin4 (black histograms). Cells were stained with commercial anti-Nectin4 mAb (B), TIGIT-Ig (C), DNAM1-Ig (D), CD112-Ig (E) or CD96-Ig (F). Figures show one representative experiment out of three performed. Graph depicting the mean fluorescence intensity values of the stainings appears in online supplementary figure 2. (G) Direct binding of Nectin4 to TIGIT. The binding of fluorophore-labeled TIGIT-Ig and its ligands PVR-Ig (red) and Nectin4-Ig (green) was determined using MST. Measurements were repeated with at least three independent protein preparations. FACS, fluorescence-activated cell sorting; IL-2, interleukin-2; MST, microscale thermophoresis; NK, natural killer.

Fig 5: Murine Nectin4 does not bind murine TIGIT. (A) Overexpression of murine Nectin4 (indicated as mNectin4) on Raji cells. Western blots were performed with antimurine Nectin4 AB and expression was compared with Raji cells expressing empty vector (indicated as empty). Staining for GAPDH was used as a loading control. (B) FACS staining of Raji cells transfected either with an empty vector as control (gray histograms), or with murine Nectin4 (black histograms). Cells were stained with murine TIGIT-Ig. Figures show one representative experiment out of three performed. Graph depicting the mean fluorescence intensity values of the stainings appears in online supplementary figure 4 FACS, fluorescence-activated cell sorting.