Figure 1.
Generation and purification of mIFN-γ and hIFN-γ immunocytokines targeting CD70.
(A) Two plasmids – pMAZ-IgH and pMAZ-IgL – were used as backbones to construct and express anti-CD70 immunocytokines bearing either murine (m) or human (h) IFN-γ. pMAZ-IgH expresses the anti-CD70 heavy chain separated from murine or human IFN-γ by a flexible (Gly)4-Ser linker. pMAZ-IgL encodes the anti-CD70 light chain. For details of construction, expression and purification, please see the Materials and Methods section. (B) Coomassie Blue-stained SDS-PAGE gel of mIFN-γ-anti-CD70 immunocytokine (lane 1), and hIFN-γ-anti-CD70 immunocytokine (lane 2) purified from supernatants of 293T cells after transfection with the plasmids described in A.
Figure 2.
Anti-CD70-IFN-γ immunocytokines induce species-specific phosphorylation of STAT1.
Murine (RenCa) or human (Caki-1) RCC cells were treated with anti-CD70 immunocytokines bearing either murine (m) or human (h) IFN-γ (‘Anti-CD70 fusion’, 50 ng/ml). As controls, parallel populations of these cells were treated with recombinant murine or human IFN-γ (‘Native’, 10 ng/ml). At the indicated times post-treatment, cells were examined by immunoblotting for either phosphorylated (p-STAT1) or total STAT1.
Figure 3.
Anti-CD70-IFN-γ immunocytokines display species-specific antiviral activity.
Murine (RenCa) or human (Caki-1) RCC cells were pre-treated for 16 h with anti-CD70 immunocytokines bearing either murine (m) or human (h) IFN-γ (‘Anti-CD70 fusion’, 50 ng/ml). As controls, parallel populations of these cells were pre-treated for 16 h with recombinant murine or human IFN-γ (‘Native’, 10 ng/ml), or with unfused anti-CD70 antibody (50 ng/ml). Following pre-treatment, cells were infected with VSV-GFP (MOI = 5 for RenCa, 0.05 for Caki-1). (A) Infected cells were photographed by brightfield (for demonstration of cytopathic effect) or by fluorescence (to show viral replication) microscopy 20 h post-infection. (B) Viability of cells treated as above was determined 20 h post-infection. (C) VSV progeny yield from supernatants of infected cells was determined by standard plaque assay 20 h post-infection. Error bars represent mean +/− S.D, n = 3.
Figure 4.
Anti-CD70-IFN-γ immunocytokines bind human CD70.
(A) 293T cells were transfected with an expression vector encoding Myc-tagged human CD70 (‘CD70’), or with an empty vector (‘Vec’). 24 h post-transfection, cells were examined for CD70 expression in lysates by anti-Myc immunoblotting (inset, top panel; β-actin loading control, bottom panel), or on the cell surface by FACS staining with a FITC-conjugated anti-CD70 monoclonal antibody. (B) 293T cells were transfected as in A with either an empty vector (‘Vec’) or an expression vector encoding Myc-tagged CD70 (‘CD70’). 24 h post-transfection, cells were incubated with either Rituximab as an isotype control human IgG1 antibody (‘Isotype Control’, left panel), or with immunocytokines bearing either murine (m) or human (h) IFN-γ (‘Anti-CD70 fusion’), and, following labeling with FITC-conjugated anti-human IgG secondary antibodies, analyzed by FACS for CD70 expression. (C) The ATCC-derived RCC cell lines 786-O, 769-P, Caki-1, and ACHN were incubated with either an isotype control human IgG1 antibody (Rituximab, dashed line), anti-CD70-mIFN-γ immunocytokine (thin solid line), or anti-CD70-hIFN-γ immunocytokine (thick solid line), followed by labeling with FITC-conjugated anti-human IgG secondary antibodies and detection of fluorescence by FACS. All four ATCC cell lines are robustly and specifically stained by both anti-CD70 IFN-γ immunocytokines.
Figure 5.
Anti-CD70-IFN-γ immunocytokines are cytotoxic to RCC cell lines in the presence of bortezomib.
RCC cell lines RenCa (A) or Caki-1 (B) were treated either with unfused anti-CD70 antibody (‘Anti-CD70’), with recombinant, native human or murine IFN-γ (‘Native’), or with human or murine IFN-γ immunocytokines (‘Anti-CD70 fusion’) for 72 h in the presence of their MTD of bortezomib (black bars). As controls, these cells were also treated with each agent singly (grey bars). In conditions requiring bortezomib co-treatment, bortezomib was added to cells 1 h before IFN-γ.
Figure 6.
Anti-CD70-IFN-γ immunocytokines exert RIP1-dependent necrotic activity on RCC cell lines.
(A) RenCa, Caki-1, 786-O, or HRC63 cells were co-treated with bortezomib (MTD) and, respectively, murine (RenCa) or human (Caki-1, 786-O, and HRC63) IFN-γ immunocytokines (‘Anti-CD70 fusion’, 50 ng/ml) in the presence or absence of 50 μM RIP1 kinase inhibitor Nec-1 for 72–84 h. The MTD of bortezomib for 786-0 and HRC63 cells was 4 ng/ml and 2 ng/ml, respectively. Cell viability was determined by Trypan Blue exclusion analysis. Error bars represent mean +/− S.D; n = 3. (B) RenCa, Caki-1, 786-O, or HRC63 cells pre-treated without (-Nec-1) or with (+Nec-1) for 1h, before co-treatment with IFN-γ immunocytokines and bortezomib as in (A), were photographed 72 h post-treatment.
Figure 7.
IFN-γ signaling components show elevated expression in ccRCC.
Box plots depicting mRNA expression levels of key IFN-γ signaling components (IFNGR1, IFNGR2, JAK1 and STAT1) in 21 paired ccRCC and normal samples [50]. The data were normalized using Robust Multi-array average (RMA) [54]. The gene fold-changes for Tumor-Normal comparison were obtained by LIMMA [41]. Y-axis shows RMA-normalized expression level (on log2 scale) of each mRNA. The solid line within each box is the median, and distance between box and whiskers indicate interquartile ranges.