Anti-SIRPα antibodies as a potential new tool for cancer immunotherapy
Tadahiko Yanagita, Yoji Murata, Daisuke Tanaka, Sei-ichiro Motegi, Eri Arai, Edwin Widyanto Daniwijaya, Daisuke Hazama, Ken Washio, Yasuyuki Saito, Takenori Kotani, Hiroshi Ohnishi, Per-Arne Oldenborg, Noel Verjan Garcia, Masayuki Miyasaka, Osamu Ishikawa, Yae Kanai, Takahide Komori, Takashi Matozaki
Tadahiko Yanagita, Yoji Murata, Daisuke Tanaka, Sei-ichiro Motegi, Eri Arai, Edwin Widyanto Daniwijaya, Daisuke Hazama, Ken Washio, Yasuyuki Saito, Takenori Kotani, Hiroshi Ohnishi, Per-Arne Oldenborg, Noel Verjan Garcia, Masayuki Miyasaka, Osamu Ishikawa, Yae Kanai, Takahide Komori, Takashi Matozaki
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Research Article Immunology Oncology

Anti-SIRPα antibodies as a potential new tool for cancer immunotherapy

Abstract

Tumor cells are thought to evade immune surveillance through interaction with immune cells. Much recent attention has focused on the modification of immune responses as a basis for new cancer treatments. SIRPα is an Ig superfamily protein that inhibits phagocytosis in macrophages upon interaction with its ligand CD47 expressed on the surface of target cells. Here, we show that SIRPα is highly expressed in human renal cell carcinoma and melanoma. Furthermore, an anti-SIRPα Ab that blocks the interaction with CD47 markedly suppressed tumor formation by renal cell carcinoma or melanoma cells in immunocompetent syngeneic mice. This inhibitory effect of the Ab appeared to be mediated by dual mechanisms: direct induction of Ab-dependent cellular phagocytosis of tumor cells by macrophages and blockade of CD47-SIRPα signaling that negatively regulates such phagocytosis. The antitumor effect of the Ab was greatly attenuated by selective depletion not only of macrophages but also of NK cells or CD8+ T cells. In addition, the anti-SIRPα Ab also enhances the inhibitory effects of Abs against CD20 and programmed cell death 1 (PD-1) on tumor formation in mice injected with SIRPα-nonexpressing tumor cells. Anti-SIRPα Abs thus warrant further study as a potential new therapy for a broad range of cancers.

Authors

Tadahiko Yanagita, Yoji Murata, Daisuke Tanaka, Sei-ichiro Motegi, Eri Arai, Edwin Widyanto Daniwijaya, Daisuke Hazama, Ken Washio, Yasuyuki Saito, Takenori Kotani, Hiroshi Ohnishi, Per-Arne Oldenborg, Noel Verjan Garcia, Masayuki Miyasaka, Osamu Ishikawa, Yae Kanai, Takahide Komori, Takashi Matozaki

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Figure 3

Importance of macrophages for the antitumor effect of the MY-1 mAb against mouse SIRPα in vivo.

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Importance of macrophages for the antitumor effect of the MY-1 mAb again...
(A) BALB/c mice were injected i.v. with either PBS liposomes as a control (Ctrl) or clodronate liposomes (Clodronate). Splenocytes isolated from the mice 3 days later were stained with propidium iodide (PI), a brilliant violet (BV) 510–conjugated mAb against CD45, a BV 421–conjugated mAb against CD11b, and a phycoerythrin-conjugated (PE-conjugated) mAb against F4/80 for analysis by flow cytometry. The relative number of F4/80+CD11b+ cells (macrophages) is expressed as a percentage of all viable CD45+ cells on each plot. (B) BALB/c mice were injected with PBS liposomes or clodronate liposomes, RENCA cells, and either MY-1 or control IgG according to the indicated schedule. Tumor volume was measured at the indicated time points. (C and D) CFSE-labeled RENCA cells were incubated for 4 hours with BALB/c mouse BM-derived macrophages (BMDMs) in the presence of the indicated Abs, after which cells were harvested, stained with a biotin-conjugated mAb against F4/80 and allophycocyanin-conjugated (APC-conjugated) streptavidin as well as with PI, and analyzed by flow cytometry. The relative number of CFSE+F4/80+ BMDMs (BMDMs that had phagocytosed CFSE-labeled RENCA cells) is expressed as a percentage of all viable F4/80+ cells in the representative plots (C) as well as for a representative experiment (D). (E) CFSE-labeled RENCA cells were incubated for 4 hours with BMDMs in the presence of control IgG or of intact or F(ab′)2 fragments of MY-1. The percentage of CFSE+F4/80+ BMDMs among viable F4/80+ cells was then determined as in C. (F) RENCA cells were transfected with signal regulatory protein α (Sirpa) or control siRNAs, after which cells were labeled with CFSE and stained with PI, a biotin-conjugated mAb against mouse SIRPα (P84) (or isotype control), and APC-conjugated streptavidin for analysis by flow cytometry (left panel). The CFSE-labeled RENCA cells were also incubated for 4 hours with BMDMs in the presence of the indicated Abs. The percentage of CFSE+F4/80+ BMDMs among viable F4/80+ cells was then determined as in C (right panel). Data are representative of 3 separate experiments (A and C–F); the mean ± SEM of triplicate determinations (n = 3) (D, E, and right panel in F), or the mean ± SEM for n = 8 mice per group in 2 separate experiments (B). ***P < 0.001, by 2-way (B) or 1-way (D, E, and right panel in F) ANOVA with Tukey’s test.