Genetic variation of human neutrophil Fcγ receptors and SIRPα in antibody‐dependent cellular cytotoxicity towards cancer cells

Abstract

The efficacy of cancer therapeutic antibodies varies considerably among patients. Anti-cancer antibodies act through different mechanisms, including antibody-dependent cellular cytotoxicity (ADCC) triggered via Fcγ receptors (FcγR). This phagocyte ADCC can be promoted by interference with CD47-SIRPα interactions, but the magnitude of this enhancement also varies among individuals. Both FcγR and SIRPα display considerable genetic variation, and we investigated whether this explains some of the variability in ADCC. Because of linkage disequilibrium between FcγR variants the interpretation of previous reports suggesting a potential link between FcγR polymorphisms and ADCC has been troublesome. We performed an integrated genetic analysis that enables stratification. ADCC by activated human neutrophils towards Trastuzumab-coated breast cancer cells was predominantly dependent on FcγRIIa. Neutrophils from individuals with the FcγRIIa-131H polymorphic variant displayed significantly higher killing capacity relative to those with FcγRIIa-131R. Furthermore, ADCC was consistently enhanced by targeting CD47-SIRPα interactions, and there were no significant functional differences between the two most prevalent SIRPα polymorphic variants. Thus, neutrophil ADCC capacity is directly related to the FcγRIIa polymorphism, and targeting CD47-SIRPα interactions enhances ADCC independently of FcγR and SIRPα genotype, thereby further suggesting that CD47-SIRPα interference might be a generic strategy for potentiating the efficacy of antibody therapy in cancer.

Discovery of high affinity, pan-allelic, and pan-mammalian reactive antibodies against the myeloid checkpoint receptor SIRPα

“…26 As an orthogonal confirmation, we selected 510 individuals representing different populations from the above Phase 3 project, procured the respective DNA samples, and performed Sanger sequencing of exon 3 the SIRPA gene of these individuals. In agreement with Treffers et al, 25 our bioinformatic analyses of SIRPα sequences from 2535 individuals and Sanger sequencing of 510 samples identified only two SIRPα variants, v1 and v2 (Table S1), represented as three allelic groups: homozygous v1/v1, homozygous v2/v2, and heterozygous v1/v2. Examples of the detailed sequence analyses are described in Fig.…”

“…24 More recently, Treffers et al quantified SIRPα polymorphisms in Caucasians and identified only the two prevalent SIRPα variants, v1 and v2, within this population. 25 Whereas genetic variation of SIRPα does not seem to affect intrinsic phagocyte function, 25 activation of a single functional SIRPα variant in heterozygote macrophages is sufficient to inhibit antibody-dependent effector functions. 9 Thus, effective therapeutic targeting of SIRPα across diverse patient populations requires pan-allelic anti-SIRPα antibodies.…”

Plasticity in Pro- and Anti-tumor Activity of Neutrophils: Shifting the Balance

“…Of interest, although FcγRI is the high-affinity receptor for IgG1 antibodies, no effect was found when monovalent Fc fragments were used for blockade. This might be explained by the incapacity to fully block the receptor by use of these monovalent Fc fragments or due to the relatively low expression levels on the surface of neutrophils ( 150 ). Nevertheless, contradicting results were described regarding the potential of FcγRI on neutrophils in mediating ADCC.…”

The interplay between neutrophils and microbiota in cancer

“…). Neutrophils may also mediate antibody‐dependent cell‐mediated cytotoxicity of tumors, become nonprofessional antigen presenters to CD4 + T cells, and activate CD8 + T cells, B cells, dendritic cells, or NK cells . NK cell‐derived IFN‐γ promotes the tumor‐killing functions of VEGF‐expressing neutrophils .…”

“…6 TAN MECHANISMS IN THE TUMORAn extensive list of neutrophil anti-tumor mechanisms has been compiled by Sionov et al,105 including production of ROS, 47,106,107 IL-12, TNF, cathelicidins, CCL2, CCL3, IL-1 , and TRAIL16,47,[108][109][110][111] (Fig. 2).Neutrophils may also mediate antibody-dependent cell-mediated cytotoxicity of tumors,101,112 become nonprofessional antigen presenters to CD4 + T cells,[113][114][115] and activate CD8 + T cells,17,47 B cells, 116 dendritic cells, 117 or NK cells 118. NK cell-derived IFN-promotes the tumor-killing functions of VEGF-expressing neutrophils 119.…”