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. 2021 Jun 8;205(3):333–342. doi: 10.1111/cei.13618

Anti‐CD47 antibody synergizes with cisplatin against laryngeal cancer by enhancing phagocytic ability of macrophages

Jingmiao Wang 1,✉, Haizhong Zhang 1, Xiaoyan Yin 1, Yanrui Bian 1
PMCID: PMC8374222  PMID: 33999416

Abstract

Cisplatin is mainly used in late‐stage or recurrent laryngeal cancer patients. However, the effect of the chemotherapy is limited due to cisplatin resistance. Therefore, we explored the synergized role of immunosuppressive mediator with cisplatin in laryngeal cancer. Cancer cells isolated from tissues of patients with laryngeal cancer were treated with cisplatin to screen the potential immunosuppressive mediator, whose synergized effects with cisplatin were explored both in vivo and in vitro. CD47 was selected for its high expression in cisplatin‐treated laryngeal cancer cells. Blocking CD47 expression using its neutralizing antibody (aCD47) synergized with cisplatin to increase macrophage phagocytosis in a co‐culture system of human epithelial type 2 (Hep‐2) cancer cells with tumor‐associated macrophages (TAMs). Moreover, aCD47 together with cisplatin prevented tumor growth by inhibiting proliferation of cancer cells and the secretion of proinflammatory cytokines, as well as by inducing the apoptosis of cancer cells and phagocytosis of TAMs in a Hep‐2‐implanted mouse tumor model. aCD47 synergized with cisplatin against laryngeal cancer by enhancing the phagocytic ability of TAMs, and the combined therapy of cisplatin and aCD47 might serve as a novel therapeutic strategy against laryngeal cancer.

Keywords: CD47, cisplatin, laryngeal cancer, mice, phagocytosis

aCD47 synergized with Cisplatin against laryngeal cancer by enhancing the phagocytic ability of TAMs, and the combined therapy of Cisplatin and aCD47 might serve as a novel therapeutic strategy against laryngeal cancer.

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INTRODUCTION

Laryngeal cancer is a malignancy that occurs in the larynx, and is one of the most common malignant tumors of the upper respiratory and digestive tract, accounting for 1–5% of systemic malignant tumors. In 2018 in the United States, 12 150 new cases of laryngeal cancer were diagnosed and 3710 patients died of this disease, which contributed to approximately 0.8% of all new cancer diagnosis and 0.6% of all cancer‐related deaths [1]. Although the incidence rate of laryngeal cancer has decreased annually for the last decade due to the reduced use of tobacco, its 5‐year survival rate of 60.9% has not changed during the past several years. This is because the survival rate for patients with laryngeal cancer is strongly associated with the initial stage of disease at diagnosis, reaching as high as 90% for early‐stage T1 and T2 tumors, according to the tumor–node–metastasis (TNM) classification of malignant tumors by the American Joint Committee on Cancer (AJCC). Moreover, its cure rate is reduced to less than 40% for Stages III or IV at presentation. Therefore, early diagnosis and timely treatment lead to improved therapeutic effects with a high cure rate. However, approximately 40–50% cases of laryngeal cancer present an advanced stage clinically, leading to poor therapeutic effect [2, 3].

Cisplatin is mainly utilized to treat patients with laryngeal cancer of Stages III or IV, as well as recurrent patients after laryngectomy. However, only a small proportion of patients react well to cisplatin‐based chemotherapy as a result of cisplatin resistance, which is one of the important factors that limit its therapeutic effects [4]. A number of published studies have indicated that chemotherapy resistance is strongly associated with changes in the immune microenvironment of tumors [5, 6, 7, 8, 9], suggesting that the host immune system could influence the outcome of chemotherapy. In this context, considering that the functional state of host immune system has a predictive and prognostic impact on the fate of cancer patients treated with conventional or targeted chemotherapies, immunotherapies combined with conventional therapies are emerging as a novel effective strategy for cancer treatment. However, currently there is little research regarding this combination therapy against laryngeal cancer.

CD47 is a well‐known immune regulator. By binding with its ligands, such as signaling regulatory protein α (SIRPα), thrombospondin‐1 (TSP‐1), SH2‐domain bearing protein tyrosine phosphatase substrate‐1 (SHPS‐1) and integrins, it modulates the activation of T, B and dendritic cells, the transmigration of neutrophils and the phagocytosis of macrophages. A number of studies have reported that CD47 is highly expressed in various cancer cells, which binds to SIRPα on the tumor‐associated macrophages (TAMs) that sends a signal of ‘do not eat me’ to macrophages, leading to the escape of cancer cells from the immune system. Therefore, blocking the expression of CD47 on cancer cells effectively increases the phagocytic abilities of phagocytes. Based on this observation, CD47 is currently considered as a promising target in cancer therapy [10, 11, 12, 13, 14]. Nonetheless, only one publication has implicated the role of CD47 in laryngeal cancer, which suggested that CD47 was a potential target to treat laryngeal squamous cell carcinoma [15]. Thus, our current study aimed to explore the therapeutic effect of cisplatin‐based therapy combined with CD47 against laryngeal cancer.

MATERIALS AND METHODS

Patient samples

Cancer tissue samples were obtained from five patients with laryngeal cancer who signed consent forms. Tissues were then digested into a single‐cell suspension. After centrifuging, single cells were cultured in complete Dulbecco’s modified Eagle’s medium (DMEM) containing 10% fetal bovine serum (FBS) (gibco, Carlsbad, California, usa) in the presence of 7.5 μM cisplatin (CAS 15663‐27‐1) (Sigma‐Aldrich, St Louis, Missouri, USA) for 24 h. Cells were then harvested for the following studies. The collection of cancer tissue samples from patients was approved by the ethics committee of the Second Hospital of Hebei Medical University.

FACS detection

Human laryngeal cancer cell line human epithelial type 2 (Hep‐2, Cat. no. CCL‐23) (ATCC, Manassas, Virginia, USA) was maintained in complete DMEM. After being treated with 7.5 μM cisplatin for 24 h, cells were collected to measure CD47 expression. Treated cells were stained with anti‐CD47 fluorescein isothiocyanate (FITC) (Cat. no. 11‐0479‐42) (Thermo Fisher Scientific, Fremont, California, USA), then sorted by flow cytometry (BD FACSVia). Moreover, treated cells were stained with CD47 antibody (Cat. no. 14‐0479‐82) (Thermo Fisher Scientific), followed by 4′,6‐diamidino‐2‐phenylindole (DAPI) staining for nuclei and Alexa Fluor 488 phalloidin staining for cytoskeleton; images were then captured using a confocal microscope.

Isolation of human TAMs

TAMs were isolated from laryngeal cancer samples of patients, as previously described [16]. Briefly, fresh tissues were cut into pieces and digested in DMEM containing 5% fetal bovine serum (FBS), 2 mg/ml collagenase I and 2 mg/ml hyaluronidase (Sigma‐Aldrich) at 37°C for 2 h. After sequentially filtering through 500 μm mesh and a 70 μm cell strainer, 1 ml cell suspension was added to a 15 ml tube with 5 ml 45% Percoll (GE Healthcare, Chicago, Illinois, USA) in the middle and 5 ml 60% Percoll at the bottom, then centrifuged at 600 g for 20 min. Mononuclear cells were collected at between 45 and 60% Percoll, followed by a magnetic activated cell sorting system using a direct CD14 isolation kit to acquire TAMs (Miltenyi Biotec, San Diego, California, USA), according to the manufacturer’s instructions.

Co‐culture system

After pretreatment with or without 7.5 μM cisplatin for 24 h, Hep2 cells were labeled with carboxyfluorescein succinimidyl ester (CFSE) and co‐cultured with isolated primary TAMs at a 1:1 ratio in the absence or presence of 10 μg/ml anti‐CD47 neutralizing antibody (aCD47) for 24 h. Subsequently, co‐cultured TAMs were sorted by flow cytometry. Moreover, CellTruth blue‐labeled Hep2 cells were co‐cultured with CFSE‐labeled TAMs and treated as mentioned above. Then a confocal microscope was used to capture images to analyze the phagocytosis of TAMs.

Western blot

Total protein from treated cells or tumor tissues were isolated, then Western blot was performed as previously described [17]. β‐actin was used as loading control. The antibodies used were CD47 (Cat. no.14‐0479‐82) (Thermo Fisher), β‐actin (ab8227; Abcam, Cambridge, Massachusetts, USA), transforming growth factor‐β (TGF‐β) (ab92486; Abcam), interleukin‐12p70 (IL‐12p70) (Cat. no. MAB219) (R&D Systems, Minneapolis, Minnesota, USA) and interferon‐γ (IFN‐γ) (ab9657; Abcam).

Reverse transcription–polymerase chain reaction (RT–PCR)

Total mRNA was extracted from treated cells using Omega Bio‐Tek’s E.Z.N.A.® HP total RNA kit and Qiagen’s RNeasy® Plus mini kit (74134), following the manufacturer’s instructions, and transcribed into cDNA. RT–PCR was performed as described previously [18] using glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) as control.

Transportation of Hep2 cells into non‐obese diabetic/severe combined immunodeficiency (NOD/SCID) mice

Female NOD/SCID mice, 3–4 weeks old (GemPharmatech, Nanjing, China), received a 200 cGy whole‐body irradiation 12 h before Hep2 cell transplantation; 2 × 106 Hep2 cells in 0.2 ml medium were injected into the flank of NOD/SCID mice from the tail vein. When the tumor volume reached approximately 50 mm3, mice were injected with 2.5 mg/kg cisplatin [cis‐diamine‐dichloroplatinum (CDDP)] or phosphate‐buffered saline (PBS) three times every 3 days; 24 h after the last injection, tumor tissues were collected for the following studies.

Transportation of Hep2 cells into C57BL/6 mice

Hep2 cells, 2×106, in 0.2 ml medium were injected into the flank of C57BL/6 mice (GemPharmatech, Nanjing, China), and mice bearing tumors of approximately 50 mm3 in size were randomly divided into four groups and treated with PBS, CDDP, aCD47 or CDDP + aCD47 three times every 3 days, respectively. The CDDP or aCD47 dosage was 2.5 mg/kg. Tumor sizes were monitored every 3 days from the first treatment. Tumor tissues were collected 18 days after the first dose. After digestion, cells were stained with allophycocyanin (APC)‐CD45 (ab221245; Abcam), BV510‐CD8 (Cat. no. 563256) (BD Biosciences, San Jose, California, USA) to sort CD8+ T cells by flow cytometry.

The green fluorescent protein (GFP)‐Hep‐2 cell humanized mouse model was established and treated as indicated above. The tumor tissues were collected, digested and sorted by flow cytometry to analyze the proportion of GFP‐labeled Hep2 cells in the tumor tissues from different groups. All animal studies were approved by the ethics committee of the Second Hospital of Hebei Medical University.

Enzyme‐linked immunosorbent assay (ELISA)

The production of TGF‐β, IL‐12p70 and IFN‐γ in the tissues were measured using a TGF‐β ELISA kit (ab100647; Abcam), an IL‐12p70 ELISA kit (D1200; R&D Systems) and an IFN‐γ ELISA kit (ab174443; Abcam), respectively.

Proliferating cell nuclear antigen (PCNA) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining

Paraffin‐embedded sections were incubated with anti‐PCNA antibody (ab19166; Abcam). Sections of tumor tissues were stained using the TUNEL kit (ab66110; Abcam) according to the manufacturer’s instructions. Images were taken using a Zeiss Axioplan 2 fluorescence microscope.

Statistical analysis

Data were analyzed using SPSS and reported as means ± standard deviation (SD). Data were analyzed by Student’s t‐test and one‐ or two‐way analysis of variation (ANOVA) analysis followed by a post‐hoc test. Each experiment was repeated independently at least three times. Statistical significance was confirmed when the p‐value was less than 0.05.

RESULTS

Cisplatin treatment increased CD47 expression in laryngeal cancer tissue cell lines

First, we isolated cells from laryngeal cancer tissues of five patients, which were then treated with 7.5 μM cisplatin for 24 h. Among all the genes associated with immunosuppression, including programmed cell death protein 1 (PD‐1), programmed death ligand 1 (PD‐L1), cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4), indoleamine 2,3‐dioxygenase 1 (IDO 1), signal transducer and activator of transcription 3 (STAT‐3), CD47, CD73 and colony‐stimulating factor 1 receptor (CSF1R), only CD47 showed significantly higher expression (Figure 1a). The protein levels of CD47 were also induced in the cells derived from patients 24 h after cisplatin treatment (Figure 1b). Next, we treated human laryngeal cancer cell line Hep‐2 with 7.5 μM cisplatin for 24 h; both the mRNA and protein levels of CD47 were significantly induced by cisplatin (Figure 1c). In addition, the up‐regulated expression of CD47 in cisplatin‐treated cells was confirmed by flow cytometry (Figure 1d) and confocal microscopy (Figure 1e). Thus, cisplatin remarkably increased the expression of CD47 in laryngeal cancer cells both in vitro and in vivo.

FIGURE 1.

FIGURE 1

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Cisplatin treatment increased CD47 expression in cells from laryngeal cancer tissue from patients and the human laryngeal cancer cell line. (a) Gene expression in patient‐derived laryngeal cancer cells post‐cisplatin treatment. Five laryngeal cancer samples obtained from five patients underwent an enzymatic digestion and digested single cells were cultured in complete Dulbecco’s modified Eagle’s medium (DMEM) medium containing 7.5 μM cisplatin; 24 h later, cells were harvested for the examination of gene expression. The mRNA levels of gene associated with immunosuppression [including programmed cell death 1 (PD‐1), programmed cell death ligand 1 (PD‐L1), cytotoxic T lymphocyte antigen (CTLA‐4), indoleamine 2,3‐dioxygenase 1 (IDO1), signal transducer and activator of transcription (STAT)‐3, CD47, CD73 and colony‐stimulating factor 1 receptor (CSF‐1R)] were examined by real‐time polymerase chain reaction (PCR). GAPDH was detected as control. n = 5. (b) The protein levels of CD47 in patient‐derived laryngeal cancer cells post‐cisplatin treatment were examined by Western blot. β‐actin was used as loading control. Human laryngeal cancer cell line human epithelial type 2 (Hep‐2) cells were treated with 7.5 μM cisplatin for 24 h, the expression of CD47 in mRNA level (up) and protein level (low) were examined by real‐time PCR and Western blot (c); n = 3. Data represent means ± standard deviation (SD). ***p < 0.001 (versus cisplatin group). The CD47 expressions were also detected via flow cytometry (d) and confocal microscopy (e). Scale bar, 10 μm

aCD47 improved macrophage phagocytosis of cisplatin‐treated Hep2 cells

TAMs are well recognized as a crucial effector of tumor environment to regulate tumor growth, angiogenesis, metastasis, immune regulation and chemo‐resistance [19]. Therefore, we isolated TAMs from laryngeal cancer tissues from patients, which were then co‐cultured with CFSE‐labeled Hep2 cells, followed by pretreatment with cisplatin. Cisplatin pretreatment did not change the number of Hep2 cells phagocytized by TAMs compared to the control group (Figure 2a,b), which suggested that Hep2 cells pretreated with cisplatin did not alter the phagocytic ability of TAMs. Notably, the supplement of aCD47 in co‐culture medium significantly increased the number of cisplatin‐pretreated Hep2 cells phagocytized by TAMs. In addition, confocal images also indicated that aCD47 synergized with cisplatin to promote TAM phagocytosis (Figure 2c). Based on these observations, inhibiting the expression of CD47 by aCD47 facilitated cisplatin in increasing the phagocytic ability of TAMs.

FIGURE 2.

FIGURE 2

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Macrophages exhibited improved phagocytosis against cisplatin‐treated human laryngeal cancer cell line human epithelial type 2 (Hep‐2) with the assistance of αCD47. Representative flow cytometric images (a) and quantification (b) of the phagocytosis of Hep‐2 cells by tumor‐associated macrophages (TAMs). TAMs were isolated from five fresh laryngeal cancer samples. Hep‐2 cells were treated with cisplatin for 24 h (7.5 μM). Treated Hep‐2 cells were labeled with carboxyfluorescein succinimidyl ester (CFSE) and co‐cultured with TAMs (the cell ratio = 1:1) with or without the addition of αCD47 (10 μg/ml) for 24 h. The αCD47 group indicated that Hep‐2 without cisplatin treated co‐cultured with macrophages with the presence of αCD47. The phagocytosis of macrophages against tumor cells (measured by the CFSE positive macrophages) were examined by 24 h co‐culture; n = 20. (c) Fluorescence microscopy analysis of the phagocytosis experiments. Scale bar, 10 μm. Hep‐2 cells and TAMs were labeled with CellTrace Blue and CFSE, respectively, and treated as indicated above. ***p < 0.001

aCD47 synergized with cisplatin to suppress tumor growth in vivo

To further evaluate the effect of CD47 in laryngeal cancer in vivo, we first injected Hep2 cells into NOD/SCID mice. When the tumor volume reached approximately 50 mm3, mice were administered 2.5 mg/kg CDDP or PBS three times every 3 days. As expected, the expression of CD47 in the tumor tissues was significantly up‐regulated (Figure 3a–c), which was consistent with our study in vitro. Next, we began to treat mice with cisplatin, aCD47 or both when tumor size reached approximately 50 mm3. Compared to the control group, aCD47 injection delayed tumor progression (Figure 3d), and cisplatin treatment further inhibited tumor growth. Notably, the combination of cisplatin and aCD47 significantly suppressed the tumor size, which indicated that the mice treated with the combination of cisplatin and aCD47 exhibited the smallest tumor among all these four groups (Figure 3d). Furthermore, the proliferation of Hep2 cells, as indicated by the PCNA staining, was reduced by cisplatin/aCD47 treatment, and was further inhibited by cisplatin + aCD47 (Figure 3e). In contrast, the apoptosis of Hep2 cells, as reflected by TUNEL staining, was induced by cisplatin/aCD47 treatment, and further increased by their combination (Figure 3e). In addition, we injected GFP‐labeled Hep2 cells into the mice and tumor tissues were digested to analyze the proportion of GFP‐Hep2 cells and TAMs by flow cytometry. The number of Hep2 cells phagocytized by TAMs, as reflected by the co‐stained GFP and F4/80, was not altered by either cisplatin or aCD47 treatment (Figure 3f,g). Nonetheless, combined treatment of cisplatin and aCD47 markedly improved the phagocytic ability of TAMs in comparison with either cisplatin/aCD47 alone. Thus, these results revealed that aCD47 strongly synergized with cisplatin to inhibit tumor growth by suppressing the proliferation and inducing the apoptosis of cancer cells, as well as promoting the phagocytic ability of TAMs.

FIGURE 3.

FIGURE 3

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In vivo anti‐tumor effect of cisplatin and anti‐CD47 antibody in a humanized mouse model. Human epithelial type 2 (Hep‐2) cells were injected into the flank of non‐obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. When the tumor volumes reached approximately 50 mm3, mice received phosphate‐buffered saline (PBS) or cis‐diamine‐dichloroplatinum (CDDP) three times every 3 days. The administration dosage of CDDP was 2.5 mg/kg; 24 h post‐last injection, tumor tissues were collected for examination. CD47 expressions in tumor tissues post‐treatment were examined by real‐time polymerase chain reaction (PCR) (a), Western blot (b) and immunofluorescent staining (c). Red, blue and green colors represented CD47 signals from phycoerythrin (PE)‐conjugated αCD47, 4′,6‐diamidino‐2‐phenylindole (DAPI) staining of nuclei and Alexa Fluor 488 phalloidin staining of cytoskeleton, respectively. Scale bar, 10 μm. (d) Average tumor growth curves of Hep‐2 cells tumors in control and treated groups. C57BL/6 mice bearing tumors of ~50 mm3 received PBS, cisplatin, αCD47 or CDDP + αCD47 three times every 3 days. The administration dosages of cisplatin and αCD47 were 2.5 mg/kg and 2.5 mg/kg, respectively. Data represented as means ± standard deviation (SD), n = 6; **p < 0.01. (e) Analysis of proliferation [proliferating cell nuclear antigen (PCNA) staining] and apoptosis [terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining] in tumor tissues after treatment with various therapeutic agents. Green fluorescent protein (GFP)‐Hep‐2 cells humanized mouse model was established and treated as indicated above, the in‐vivo phagocytosis of macrophages against tumor cells were examined via flow cytometry. Representative flow cytometric images (f) and quantification (g) of the phagocytosis. Data represented as means ± standard deviation (SD), n = 6; **p < 0.01, ***p < 0.001

Combination of cisplatin and αCD47 modulated the tumor immune microenvironment in the Hep‐2‐injected mouse tumor model

As CD47 is a well‐recognized immune regulator, we next assessed the effect of aCD47 in the immune microenvironment in vivo. First, we analyzed T cells in the tumor tissues from Hep2 cell‐injected mice, and flow cytometry data indicated that the number of CD8+ T cells were significantly increased by the combination therapy compared to control, cisplatin or aCD47 groups (Figure 4a,b). Moreover, the expression levels of proinflammatory cytokines in the tumor tissues, including TGF‐β, ILi12p70 and IFN‐γ, were all significantly reduced by the combination therapy in comparison with the other three groups (Figure 4c–h), which further confirmed the effectiveness of the combination therapy against laryngeal cancer. Taken together, our data revealed that aCD47 synergized with cisplatin against laryngeal cancer.

FIGURE 4.

FIGURE 4

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Combination of cisplatin and αCD47 modulated the tumor immune microenvironment in the Hep‐2‐injected tumor model. Flow cytometry gating (a) and histogram analysis (b) of CD8+ T cells in the tumor tissues at the end of treatment. Data represented as means ± SD, n = 6; **p < 0.01, ***p < 0.001. ELISA results of transforming growth factor (TGF)‐β (c), interleukin (IL)‐12p70 (d) and interferon (IFN)‐γ (e) production in the tumors from mice receiving different treatments. Protein levels of TGF‐β (f), IL‐12p70 (g) and IFN‐γ (h) in tumor tissues examined by Western blot. Data represent means ± standard deviation (SD); n = 8; *p < 0.05, **p < 0.01, ***p < 0.001

DISCUSSION

Laryngeal cancer is one of the prevalent malignant tumors of the upper respiratory and digestive tract. Although its incidence is gradually decreasing in the past decade, its 5‐year survival rate remains as high as 60.9%, because patients usually present Stages III or IV laryngeal cancer at diagnosis and show severe drug resistance to conventional therapy such as cisplatin. Therefore, in our current study, we isolated laryngeal cancer cells from cancer tissues of patients with laryngeal cancer, which were treated with cisplatin to screen for immunosuppression‐associated factors. Consequently, CD47 was selected for its high expression following cisplatin treatment. Anti‐CD47 antibody then synergized with cisplatin to ameliorate tumor growth in Hep2‐implated C57BL/6 mice by increasing the phagocytic ability of TAMs. Hence, our combination therapy greatly improved the therapeutic efficacy of cisplatin against laryngeal cancer in comparison with conventional cisplatin intervention.

Immunosuppression is the reduction of efficacy or activation of the immune system. Immunosuppression usually occurs as an adverse reaction in conditions such as organ transplant. However, cisplatin is also utilized for treatment against autoimmune diseases and graft‐versus‐host disease after bone marrow transplant. Cancer‐associated immunosuppression contributes to cancer progression, which is also one of the reasons for the unsatisfying outcome of conventional cancer therapy. To date, the combination of conventional cancer therapy with immunotherapy emerges as a promising strategy for cancer [20, 21]. Therefore, in our study, we also evaluated the immune microenvironment in laryngeal cancer cells isolated from patients after treatment with cisplatin. We examined the expression of mediators known to be responsible for tumor evasion, including PD‐1, PD‐L1, CTLA‐4, IDO 1, STAT‐3, CD47, CD73 and colony‐stimulating CSF‐1R[22]. Among all these various effectors, CD47 was the only highly expressed gene in cisplatin‐treated laryngeal cancer cells. Therefore, we selected CD47 and explored its role in laryngeal cancer in the following studies.

Cisplatin is a chemotherapy medication used to treat numerous cancers, including laryngeal cancer, testicular cancer, ovarian cancer, cervical cancer, breast cancer and bladder cancer, etc. [23, 24, 25, 26, 27]. However, cisplatin resistance has been a prominent impediment in the clinic [28]. Reduced accumulation of cisplatin, deactivated cell apoptotic signaling and enhanced activities of detoxification and DNA repair have been shown to impair the cytotoxic effects of cisplatin in tumor cells, which contributes to cisplatin resistance [29]. Accordingly, considerable effort has been made to attenuate cisplatin resistance. Recently, combination therapy of cisplatin with novel agents targeting the tumor microenvironment has made promising development. Based on these clinical successes, we screened several immunosuppression‐related factors, and found CD47 to be a target that was both associated with cisplatin resistance and tumor microenvironment.

Although this study revealed that inhibiting the expression of CD47 and signal regulatory protein α (SIRPα) in laryngeal squamous cell carcinoma from patients simultaneously promoted phagocytosis of macrophages, our project aimed to investigate the synergistic effect of CD47 with cisplatin against laryngeal cancer. Our data suggested that the amount of tumor cells phagocytized by macrophages was significantly increased, because cisplatin‐induced expression of CD47 was blocked by anti‐CD47 antibody, leading to an enhanced effect of antibody‐dependent cellular phagocytosis (ADCP) [30]. Our observation was consistent with a previous report where anti‐CD47 antibody also enhanced trastuzumab anti‐tumor efficacy as a result of the antibody‐dependent cellular phagocytosis (ADCP) effect [31].

In summary, our study has revealed that anti‐CD47 antibody effectively synergizes with cisplatin to attenuate tumor growth by promoting the phagocytic ability of macrophages in Hep2 cell‐implanted mice.

CONFLICT OF INTERESTS

The authors declare that they have no financial disclosures or conflicts of interest.

AUTHOR CONTRIBUTIONS

Jingmiao Wang conceived this study; Jingmiao Wang, Haizhong Zhang, Xiaoyan Yin and Yanrui Bian performed the experiments, collected and analyzed the data and wrote the manuscript.

ACKNOWLEDGEMENTS

This work was supported by the Medical Scientific Research of Hebei Health Commission (20200947).

Wang J, Zhang H, Yin X, Bian Y. Anti‐CD47 antibody synergizes with cisplatin against laryngeal cancer by enhancing phagocytic ability of macrophages. Clin Exp Immunol. 2021;205:333–342. 10.1111/cei.13618

DATA AVAILABILITY STATEMENT

Data are available upon reasonable request to Dr Jingmiao Wang.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

Data are available upon reasonable request to Dr Jingmiao Wang.

Articles from Clinical and Experimental Immunology are provided here courtesy of British Society for Immunology

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