
==== Front
Oncol Rep
Oncol Rep
Oncology Reports
1021-335X
1791-2431
D.A. Spandidos

39219278
10.3892/or.2024.8806
OR-52-5-08806
Articles
Antitumor activities of anti‑CD44 monoclonal antibodies in mouse xenograft models of esophageal cancer
Ishikawa Kenichiro 12
Suzuki Hiroyuki 1
Ohishi Tomokazu 34
Nakamura Takuro 1
Yanaka Miyuki 1
Li Guanjie 1
Tanaka Tomohiro 1
Ohkoshi Akira 2
Kawada Manabu 4
Kaneko Mika K. 1
Katori Yukio 2
Kato Yukinari 1
1 Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, Aoba-ku, Sendai, Miyagi 980-8575, Japan
2 Department of Otolaryngology, Head and Neck Surgery, Tohoku University Graduate School of Medicine, Aoba-ku, Sendai, Miyagi 980-8575, Japan
3 Institute of Microbial Chemistry (BIKAKEN), Numazu, Microbial Chemistry Research Foundation, Numazu, Shizuoka 410-0301, Japan
4 Institute of Microbial Chemistry (BIKAKEN), Laboratory of Oncology, Microbial Chemistry Research Foundation, Shinagawa-ku, Tokyo 141-0021, Japan
Correspondence to: Dr Yukinari Kato, Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan, E-mail: dengfeiwen2012@163.com yukinari.kato.e6@tohoku.ac.jp
11 2024
29 8 2024
29 8 2024
52 5 14718 4 2024
23 7 2024
Copyright: © 2024 Ishikawa et al.
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
CD44 is a type I transmembrane glycoprotein associated with poor prognosis in various solid tumors. Since CD44 plays a critical role in tumor development by regulating cell adhesion, survival, proliferation and stemness, it has been considered a target for tumor therapy. Anti-CD44 monoclonal antibodies (mAbs) have been developed and applied to antibody-drug conjugates and chimeric antigen receptor-T cell therapy. Anti-pan-CD44 mAbs, C44Mab-5 and C44Mab-46, which recognize both CD44 standard (CD44s) and variant isoforms were previously developed. The present study generated a mouse IgG2a version of the anti-pan-CD44 mAbs (5-mG2a and C44Mab-46-mG2a) to evaluate the antitumor activities against CD44-positive cells. Both 5-mG2a and C44Mab-46-mG2a recognized CD44s-overexpressed CHO-K1 (CHO/CD44s) cells and esophageal tumor cell line (KYSE770) in flow cytometry. Furthermore, both 5-mG2a and C44Mab-46-mG2a could activate effector cells in the presence of CHO/CD44s cells and exhibited complement-dependent cytotoxicity against both CHO/CD44s and KYSE770 cells. Furthermore, the administration of 5-mG2a and C44Mab-46-mG2a significantly suppressed CHO/CD44s and KYSE770 ×enograft tumor development compared with the control mouse IgG2a. These results indicate that 5-mG2a and C44Mab-46-mG2a could exert antitumor activities against CD44-positive cancers and be a promising therapeutic regimen for tumors.

CD44
mAb
ADCC
CDC
esophageal tumor
antitumor activity
Japan Agency for Medical Research and Development (AMED)JP23ama121008 JP24am0521010 JP23bm1123027 JP23ck0106730 Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI)22K06995 21K20789 21K07168 22K07224 The present study was supported in part by Japan Agency for Medical Research and Development (AMED) (grant nos. JP23ama121008, JP24am0521010, JP23bm1123027 and JP23ck0106730) and by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) (grant nos. 22K06995, 21K20789, 21K07168 and 22K07224).
==== Body
pmcIntroduction

Overexpression of CD44 is observed in various solid tumors, which are involved in the tumor malignant progression through the promotion of cellular proliferation, invasiveness and stemness via specific signaling pathways (1). The diversity of CD44 molecular function is mediated by the alternative splicing (2). CD44 is encoded in 20 exons. The first five (1–5) and the last five (16–20) are constant exons that generate the shortest CD44 standard (CD44s) isoform. The exons 6–15 are alternatively spliced and inserted into the CD44s as variant exons (3). The CD44 splice variants with variant exons are designated CD44 variant (CD44v) isoforms. The inclusion of CD44v exons in various combinations is regulated by receptor tyrosine kinase signaling and splicing activators of pre-mRNA (1).

CD44 possesses an extracellular domain (ectodomain), a transmembrane domain, and an intracellular cytoplasmic domain (4). The ectodomain contains a hyaluronic acid (HA)-binding domain (HABD) that mediates cellular homing, adhesion, migration and proliferation (4). Both CD44s and CD44v isoforms have the HABD, and the HA binding causes conformational changes of the CD44, which results in the promotion of intracellular signaling pathways to regulate cell migration and proliferation (5). In CD44v isoforms, the variant exons-encoding sequences form the stem region, which provides a co-receptor for various growth factors and cytokines. These functions activate specific signaling pathways to promote invasion and stemness (6). Therefore, different isoforms of CD44v exhibit different functions according to the inserted variant exons in the CD44 ectodomain.

The relationship between CD44 expression and prognosis in patients with cancer has been evaluated and showed both poor and favorable outcomes (7). Currently, increased evidence suggests that overexpression of CD44 and its isoforms is an unfavorable indicator in patients with cancer (7). In an analysis of multiple studies, including 583 pancreatic cancer cases, overexpression of CD44 was predictive of poor overall survival, a more advanced stage and more lymph node invasion (8). Furthermore, another meta-analysis investigated the prognostic significance of cancer stem cell markers, including CD44, from 52 studies of ovarian cancer. The study concluded that CD44 overexpression was predictive of worse disease-free survival and resistance to chemotherapy (9).

Several anti-CD44 monoclonal antibodies (mAbs) have been developed for preclinical and clinical research for tumor therapy. An anti-pan-CD44 mAb (H4C4) reduced tumor growth, metastasis and post-radiation recurrence in a human pancreatic tumor xenograft model (10). A humanized anti-pan-CD44 mAb, RG7356, showed the cytotoxicity for B cell leukemia but no cytotoxicity on normal B cells. Administration of RG7356 to immunodeficient mice engrafted with chronic lymphocytic leukemia cells resulted in complete clearance of engrafted leukemia cells (11). Phase I clinical trials with RG7356 were conducted in patients with acute myeloid leukemia (12) and advanced CD44-positive solid tumor patients (13). Although RG7356 showed an acceptable safety profile, the studies were not continued due to the lack of a clinical and/or pharmacodynamic dose-response relationship with RG7356 (13).

Therapies using anti-CD44v6 mAbs were considered since CD44v6 plays critical roles in the malignant progression of tumors (14). Humanized anti-CD44v6 mAbs, including BIWA-4 and BIWA-8, were developed. These mAbs labeled with 186Re were evaluated in head and neck squamous cell carcinoma xenograft-bearing mice and exhibited therapeutic efficacy (15). Furthermore, the BIWA-4 was developed into a humanized version-drug conjugate, bivatuzumab-mertansine (anti-tubulin agent), which was evaluated in clinical trials (16). However, the clinical trials were terminated because of the severe skin toxicity, such as lethal epidermal necrolysis (17). Since CD44v6 is expressed in normal skin epithelium, the toxicity of mertansine in the skin was most likely responsible for the high toxicity (17,18). Previously, a mutated version of BIWA-4, called BIWA-8, was developed for increasing binding affinity by two amino acid substitutions of the light chain (15). The BIWA-8 was further developed to chimeric antigen receptors (CARs). The BIWA-8 CAR-T showed antitumor activities against multiple myeloma or acute myeloid leukemia engrafted with immunodeficient mice (19). Furthermore, the BIWA-8 CAR-T exhibited efficacy in lung and ovarian carcinomas xenograft models (20), which is expected for an application toward solid tumors.

In our previous studies, an anti-pan-CD44 mAb, C44Mab-5 (IgG1, kappa) was developed using the Cell-Based Immunization and Screening (CBIS) method (21). Another mAb (C44Mab-46) (22) was created by immunization of the CD44v3-10 ectodomain. Both C44Mab-5 and C44Mab-46 have the epitopes within the constant exon 2- and 5-encoded sequences (23–25) and could be applied to immunohistochemistry in oral squamous cell carcinoma (21) and esophageal squamous cell carcinoma (ESCC) (22), respectively. Furthermore, various anti-CD44v mAbs have been developed, such as C44Mab-6 (an anti-CD44v3 mAb) (26), C44Mab-108 (an anti-CD44v4 mAb) (27), C44Mab-3 (an anti-CD44v5 mAb) (28), C44Mab-9 (an anti-CD44v6 mAb) (29), C44Mab-34 (an anti-CD44v7/8 mAb) (30), C44Mab-1 (an anti-CD44v9 mAb) (31) and C44Mab-18 (an anti-CD44v10 mAb) (32). The combinational use of the anti-CD44 mAbs is essential for comprehensively analyzing human tumors.

In the present study, a mouse IgG2a type of recombinant C44Mab-5 (5-mG2a) and C44Mab-46 (C44Mab-46-mG2a) was produced using fucosyl-transferase 8 (FUT8)-deficient ExpiCHO-S cells and the antitumor activity in xenograft-bearing mice was investigated.

Materials and methods

Cell lines

ESCC cell line KYSE770 was obtained from the Japanese Collection of Research Bioresources. Chinese hamster ovary (CHO)-K1 was obtained from the American Type Culture Collection. CHO/CD44s was previously established by transfecting pCAG-Ble/PA16-CD44s into CHO-K1 cells (22). KYSE770 was cultured in Dulbecco's Modified Eagle's Medium (DMEM; Nacalai Tesque, Inc.) supplemented with 10% (v/v) heat-inactivated fetal bovine serum (FBS; Thermo Fisher Scientific, Inc.), 0.25 µg/ml amphotericin B, 100 µg/ml streptomycin, and 100 U/ml penicillin (Nacalai Tesque, Inc.). CHO-K1 was cultured in Roswell Park Memorial Institute (RPMI)-1640 medium (Nacalai Tesque, Inc.) supplemented with 10% (v/v) FBS, 0.25 µg/ml amphotericin B, 100 µg/ml streptomycin and 100 U/ml penicillin (RPMI-1640 complete medium). CHO/CD44s were cultured in RPMI-1640 complete medium containing 0.5 mg/ml Zeocin (InvivoGen). All cells were cultured in a humidified incubator at 37°C with 5% CO2.

Antibodies

Anti-pan-CD44 mAbs, C44Mab-5 and C44Mab-46 were previously established (21,22). To generate recombinant mAbs, VH cDNAs of C44Mab-5 or C44Mab-46 and CH of mouse IgG2a were cloned into the pCAG-Ble vector (FUJIFILM Wako Pure Chemical Corporation). VL cDNA of C44Mab-5 or C44Mab-46 and CL cDNA of mouse kappa light chain were also subcloned into the pCAG-Neo vector (FUJIFILM Wako Pure Chemical Corporation). The vectors were transduced into BINDS-09 (FUT8-knockout ExpiCHO-S) cells (33). 5-mG2a and C44Mab-46-mG2a were purified using Ab-Capcher (ProteNova Co., Ltd.). 281-mG2a (an anti-hamster podoplanin mAb, control mouse IgG2a) was previously described (34).

Flow cytometry

The cells, obtained using 0.25% trypsin and 1 mM ethylenediamine tetraacetic acid (EDTA; Nacalai Tesque, Inc.), were treated with 5-mG2a and C44Mab-46-mG2a, or control blocking buffer [phosphate-buffered saline (PBS) containing 0.1% bovine serum albumin (Nacalai Tesque, Inc.)] for 30 min at 4°C. Subsequently, the cells were treated with anti-mouse IgG conjugated with Alexa Fluor 488 (1:2,000; Cell Signaling Technology, Inc.) for 30 min at 4°C. Fluorescence data were collected using the SA3800 Cell Analyzer (Sony Corp.) and analyzed using SA3800 software ver. 2.05 (Sony Corp.).

Antibody-dependent cellular cytotoxicity (ADCC) reporter bioassay

An ADCC Reporter Bioassay kit (Promega Corporation) was used for the ADCC reporter bioassay. The human FcγRIIIa receptor and a nuclear factor of activated T-cells (NFAT) response element driving firefly luciferase-expressed Jurkat cells were used as effector cells. The target CHO/CD44s and KYSE770 cells (12,500 cells per well) were seeded into a 96-well white solid plate. The serially diluted 5-mG2a and C44Mab-46-mG2a were added to the target cells. The effector cells (75,000 cells in 25 µl) were then added and co-cultured with antibody-treated target cells at 37°C for 6 h. Luminescence was measured with a GloMax luminometer (Promega Corporation).

Complement-dependent cytotoxicity (CDC)

The target CHO/CD44s and KYSE770 cells were labeled using 10 µg/ml Calcein AM (Thermo Fisher Scientific, Inc.). The target cells (1×104 cells/well) were mixed with 100 µg/ml of control 281-mG2a, 5-mG2a, or C44Mab-46-mG2a and rabbit complement (final dilution 1:10, Low-Tox-M Rabbit Complement; Cedarlane Laboratories). The calcein release to the medium was measured after a 4-h incubation. The maximum fluorescence of the medium was also measured after lysing all cells with a buffer containing 0.5% Triton X-100, 10 mM Tris-HCl (pH 7.4), and 10 mM EDTA. Cytotoxicity (% of lysis) was calculated as % lysis=(E-S)/(M-S) ×100. E is the fluorescence of combined target and effector cells. S is the spontaneous fluorescence of target cells only. M is the maximum fluorescence measured. Statistical analyses were performed using GraphPad PRISM 6 software (GraphPad Software, Inc.; Dotmatics).

Antitumor activity of 5-mG2a and C44Mab-46-mG2a in xenografts of CHO/CD44s and KYSE770

All animal experiments were performed following regulations and guidelines to minimize animal distress and suffering in the laboratory by the Institutional Committee for Experiments of the Institute of Microbial Chemistry (Numazu, Japan). The animal study protocol was approved (approval nos. 2023-037 and 2023-054) by the Institutional Committee for Experiments of the Institute of Microbial Chemistry (Numazu, Japan). BALB/c nude mice (5-week-old female, a total of 72 mice) were purchased from Jackson Laboratories, Inc. and maintained on an 11-h light/13-h dark cycle at a temperature of 23±2°C and 55±5% humidity in a specific pathogen-free environment, across the experimental period. Food and water were supplied ad libitum. The weight of the mice was monitored twice per week and their health was monitored three times per week. CHO/CD44s and KYSE770 cells (5×106 cells) suspended with BD Matrigel Matrix Growth Factor Reduced (BD Biosciences) were inoculated into the left flank of the mice subcutaneously. On day 7 after the inoculation, 100 µg of 5-mG2a (n=8), C44Mab-46-mG2a (n=8), or control 281-mG2a (n=8) in 100 µl PBS were injected intraperitoneally. Additional antibody injections were performed on days 14 and 21. The tumor volume was measured on days 7, 9, 14, 17, 21 and 23. In the KYSE770 ×enograft experiment (500 µg dosage), 500 µg of 5-mG2a (n=8), C44Mab-46-mG2a (n=8), or control 281-mG2a (n=8) in 100 µl PBS were injected intraperitoneally on days 8 and 13 after the inoculation. The tumor volume was measured on days 8, 12, and 19. The tumor volume was calculated using the formula: Volume=W2 × L/2, where W is the short diameter and L is the long diameter. The loss of original body weight was determined to a point >25% (35) and/or a maximum tumor size >3,000 mm3 and/or significant changes in the appearance of tumors as humane endpoints for euthanasia. Cervical dislocation was used for euthanasia. Mice death was confirmed by respiratory arrest and rigor mortis. The xenograft tumors were carefully removed from the sacrificed mice and weighed immediately.

Immunohistochemical analysis

The paraffin-embedded xenograft tumors were autoclaved in citrate buffer (pH 6.0; Nichirei Biosciences, Inc.) for 20 min. After blocking with SuperBlock T20 (Thermo Fisher Scientific, Inc.), sections (4 µm) were incubated with 1 µg/ml of C44Mab-46 and mPMab-1 [a mouse-rat chimeric antibody against mouse podoplanin (36)] for 1 h at room temperature and then treated with the EnVision+ Kit for mouse (Agilent Technologies, Inc.) for 30 min. The color was developed using 3,3′-diaminobenzidine tetrahydrochloride (DAB; Agilent Technologies, Inc.). Counterstaining was performed with hematoxylin (Merck KGaA). Hematoxylin and eosin (H&E) staining was performed using hematoxylin and eosin (FUJIFILM Wako Pure Chemical Corporation). Leica DMD108 fluorescence microscope (Leica Microsystems GmbH) was used to examine the sections and obtain images.

Statistical analyses

All data are expressed as the mean ± standard error of the mean (SEM). Two-way ANOVA with Tukey's multiple comparisons test and two-way ANOVA with Sidak's multiple comparisons tests were conducted in CDC and tumor weight measurement, respectively. Two-way ANOVA with Sidak's multiple comparisons test was utilized for tumor volume and mice weight. GraphPad Prism 6 (GraphPad Software, Inc.; Dotmatics) was used for all calculations. P<0.05 was considered to indicate a statistically significant difference.

Results

Flow cytometric analysis against CHO/CD44s and KYSE770 cells using 5-mG2a and C44Mab-46-mG2a

In our previous study, anti-pan-CD44 mAbs (C44Mab-5 and C44Mab-46) were established and were shown to be available for flow cytometry and immunohistochemistry (21,22). In the present study, a mouse IgG2a type of C44Mab-5 and C44Mab-46 (5-mG2a and C44Mab-46-mG2a) were produced by combining VH and VL of both mAbs with CH and CL of mouse IgG2a, respectively (Fig. 1A). The reactivity of CD44s-overexpressed CHO-K1 cells (CHO/CD44s) and an endogenous CD44-expressing esophageal tumor cell line (KYSE770) was first confirmed. 5-mG2a and C44Mab-46-mG2a detected CHO/CD44s in a concentration-dependent manner (Fig. 1B), but did not detect parental CHO-K1 cells (negative control, Fig. S1). 5-mG2a and C44Mab-46-mG2a also detected KYSE770 cells in a concentration-dependent manner (Fig. 1C). KYSE770 cells were also recognized by anti-CD44v mAbs including C44Mab-6 (an anti-CD44v3 mAb), C44Mab-3 (an anti-CD44v5 mAb), C44Mab-9 (an anti-CD44v6 mAb), and C44Mab-18 (an anti-CD44v10 mAb) (Fig. S2). These results indicated that 5-mG2a and C44Mab-46-mG2a recognize exogenous and endogenous CD44.

5-mG2a and C44Mab-46-mG2a-mediated ADCC pathway activation in the presence of CHO/CD44s and KYSE770 cells

To compare the ADCC pathway activation by 5-mG2a and C44Mab-46-mG2a, the ADCC reporter bioassay was performed to measure the biological activity of the FcγRIIIa-mediated pathway activation by mAbs (37). CHO/CD44s cells were treated with diluted mAbs and then incubated with effector cells, which possess the human FcγRIIIa receptor and Firefly luciferase regulated by an NFAT response element. As demonstrated in Fig. 2A, 5-mG2a and C44Mab-46-mG2a activated the effector in a concentration-dependent manner (EC50; 6.4×10−8 g/ml and 5.4×10−8 g/ml, respectively). In the presence of KYSE770 cells, 5-mG2a activated the effector (EC50; 2.5×10−7 g/ml, Fig. 2B). However, C44Mab-46-mG2a did not (Fig. 2B).

The CDC by 5-mG2a and C44Mab-46-mG2a against CHO/CD44s and KYSE770 cells

The CDC mediated by 5-mG2a and C44Mab-46-mG2a against CHO/CD44s and KYSE770 cells was next examined. As shown in Fig. 3, both 5-mG2a and C44Mab-46-mG2a significantly exerted CDC against CHO/CD44s cells (67 and 88% cytotoxicity, respectively) and KYSE770 (27 and 31% cytotoxicity, respectively) compared with those induced by control mouse IgG2a (281-mG2a). These results demonstrated that 5-mG2a and C44Mab-46-mG2a exhibited potent CDC activities against CHO/CD44s and KYSE770 cells.

Antitumor effects of 5-mG2a and C44Mab-46-mG2a against CHO/CD44s xenograft

In the CHO/CD44s xenograft tumors, 100 µg of 5-mG2a, C44Mab-46-mG2a, or control mouse IgG2a were injected into mice intraperitoneally on days 7, 14 and 21, following CHO/CD44s inoculation. On days 7, 9, 14, 17, 21 and 23, the tumor volume was measured. The 5-mG2a and C44Mab-46-mG2a administration resulted in a significant reduction in tumor volume on days 17 (P<0.05), 21 (P<0.01) and 23 (P<0.01) compared with that of the control mouse IgG2a (Fig. 4A). The 5-mG2a and C44Mab-46-mG2a administration resulted in 46 and 48% reductions in tumor volume compared with that of the control mouse IgG2a on day 23, respectively. The histological analyses of tumors are demonstrated in Fig. S3. In the necrotic area of tumors, leukocytes and erythrocytes were infiltrated. Membranous staining of CD44 in tumor and podoplanin-positive macrophage were also detected. However, a significant difference among control, 5-mG2a and C44Mab-46-mG2a-treated tumors could not be observed.

The weight of CHO/CD44s tumors treated with 5-mG2a and C44Mab-46-mG2a was lower than that of tumors treated with the control mouse IgG2a (53 and 55% reduction, respectively; P=0.11 and P=0.09; Fig. 4B). Loss of body weight was not observed in the CHO/CD44s tumor-implanted mice during the treatments (Fig. 4C).

Antitumor effects of 5-mG2a and C44Mab-46-mG2a on KYSE770 ×enografts

In the KYSE770 ×enograft models, 100 µg of 5-mG2a and C44Mab-46-mG2a and control mouse IgG2a were injected into mice on days 7, 14 and 21, following KYSE770 inoculation. Although the tendency of the reduction of tumor volume by the treatment with 5-mG2a and C44Mab-46-mG2a was observed, significant differences were not obtained (Fig. S4). The dosage (500 µg) was next increased and the antitumor effects were investigated. As revealed in Fig. 5, 500 µg of 5-mG2a, C44Mab-46-mG2a and control mouse IgG2a were injected into mice on days 8 and 13, following KYSE770 inoculation. On days 8, 12 and 19, the tumor volume was measured. The 5-mG2a and C44Mab-46-mG2a administration resulted in a significant reduction in tumor volume on day 19 (P<0.01) compared with that of the control mouse IgG2a (Fig. 5A). The 5-mG2a and C44Mab-46-mG2a administration resulted in 51 and 37% reduction of tumor volume compared with that of the control mouse IgG2a on day 19, respectively. The histological analyses of tumors are demonstrated in Fig. S5. Membranous staining of CD44 in tumors and podoplanin-positive macrophages at the tumor periphery were observed. Infiltrated podoplanin-positive macrophages into tumors were not observed compared with KYSE770 ×enograft.

The weight of KYSE770 tumors treated with 5-mG2a and C44Mab-46-mG2a was significantly lower than that of tumors treated with the control mouse IgG2a [47% (P<0.05) and 40% (P<0.05) reduction, respectively; Fig. 5B]. Loss of body weight was not observed in the KYSE770 tumor-implanted mice during the treatments (Fig. 5C).

Discussion

In the present study, mouse IgG2a type anti-pan-CD44 mAbs (5-mG2a and C44Mab-46-mG2a) was produced and antitumor activity against CHO/CD44s and KYSE770 ×enograft tumors was evaluated. Although 5-mG2a possesses superior affinity to CD44-expressing cells compared with C44Mab-46-mG2a (22,38), both 5-mG2a and C44Mab-46-mG2a showed comparable ability of effector activation (Fig. 2A), CDC (Fig. 3A) and antitumor activity against CHO/CD44s (Fig. 4). Against KYSE770 cells, 5-mG2a exhibited superior reactivity in flow cytometry (Fig. 1C) and effector activation (Fig. 2B) compared with C44Mab-46-mG2a. However, both mAbs showed similar antitumor activity to KYSE770 ×enograft in high dosage (Fig. 5).

After the phase I trial of RG7356 in solid tumors, the developer Roche group reported that the CD44s expression is associated with HA production and predicts response to treatment with RG7356 in both xenograft tumor models and clinical response (39). The group also identified that overexpression of CD44s stimulates the HA production (39). These results suggest the close interplay between CD44s and HA and a potential biomarker to enrich patient responses to anti-CD44 mAb therapy in the clinic. In the present study, CD44s-overexpressed CHO-K1 cells and KYSE770 cells were used, which mainly express CD44v (Fig. S2) (22). Due to the lower levels of total CD44 (Fig. 1) and the CD44v expression in KYSE770 cells, a high dosage (500 µg) of mAbs was needed to suppress the KYSE770 ×enograft.

As revealed in Fig. 2B, C44Mab-46-mG2a did not activate the effector cells in the presence of KYSE770 but exerted the antitumor effect in vivo (Fig. 5). The CDC is a crucial antitumor mechanism by mAbs (40,41). Some tendency was observed that C44Mab-46-mG2a showed a more significant CDC effect compared with 5-mG2a (Fig. 3). The difference could be sufficient to exert similar antitumor effects in vivo by 5-mG2a and C44Mab-46-mG2a. There was less infiltrated podoplanin-positive macrophage into KYSE770 ×enograft compared with CHO/CD44 (Figs. S3 and S5). Since the infiltrated effector cells exert ADCC activity (42), this may be one of the reasons why ADCC did not contribute markedly in KYSE770 cells. One more possibility is their epitope. 5-mG2a recognizes the N-terminal part of CD44 [amino acids 25–36, (25)], and C44Mab-46-mG2a recognizes the central part of CD44 [amino acids 174–178, (23,24)]. Furthermore, IgG antibodies can form ordered hexamers upon binding to their antigen on cell surfaces. These hexamers efficiently bind the hexavalent complement component C1q, the first step in the classical pathway of complement activation (43,44). The structure of C44Mab-46-mG2a-CD44 complex may provide the adequate access of complements to exert CDC.

Complement has been considered as an adjunctive component that potentiates the antibody-mediated cytolytic effects. However, complement is currently considered an essential effector of tumor cytotoxic responses of antibody-based immunotherapy, which is guiding new therapeutic options (41). An increasing body of evidence suggests that complement plays critical roles in not only mAb-mediated tumor cytolysis but also several immunomodulatory functions in tumor immunosurveillance and antitumor immunity (45,46). The complicated crosstalk of complement effectors with cellular pathways that drive B cell and T cell responses influences T helper/effector T cell survival, differentiation and B cell activation. Therefore, the involvement of complement in our experimental system and/or immunocompetent mouse models should be investigated in future studies.

Most therapeutic mAbs exhibit adverse effects by recognizing antigens in normal cells (47). Clinical trials of an anti-CD44v6 mAb (BIWA-4) bivatuzumab-mertansine drug conjugate to solid tumors failed because of the skin toxicities (17,18). Therefore, cancer-selective or specific mAbs would reduce the adverse effects. Cancer-specific mAbs (CasMabs) against HER2 [H2Mab-214 (48) and H2Mab-250 (49)] have been developed by the authors and the reactivity to cancer and normal cells has been evaluated using flow cytometry. The antitumor effect in mouse xenograft models has been also reported using a mouse IgG2a or human IgG1 types recombinant mAbs (50). Some anti-CD44 mAbs which exhibit cancer specificity have been reported (51). Among them, the 4C8 mAb recognizes aberrantly O-glycosylated CD44v6 with Tn (GalNAca1-O-Ser/Thr) antigen. The 4C8 chimeric antigen receptor (CAR)-T cells demonstrated target-specific cytotoxicity in vitro, significant tumor regression, and prolonged survival in vivo (52). In our CasMab development against CD44, already established anti-CD44 mAbs were screened by comparing the reactivity against cancer and normal cells. The CasMabs against CD44 could be applicable for designing modalities such as antibody-drug conjugates and CAR-T cells.

Supplementary Material

Supporting Data

Acknowledgements

The authors thank Mr Shun-ichi Ohba and Ms Akiko Harakawa [Institute of Microbial Chemistry (BIKAKEN), Numazu, the Microbial Chemistry Research Foundation] for technical assistance with animal experiments.

Availability of data and materials

The data generated in the present study are included in the figures and/or tables of this article.

Authors' contributions

KI, HS, TO, TN, MY, GL and TT performed the experiments. MK, MKK and YKato designed the experiments. KI, HS, AO, YKatori and YKato engaged the analysis and interpretation of data. KI, HS, and YKato wrote the manuscript. HS and YKato confirm the authenticity of all the raw data. All authors read and approved the final version of the manuscript.

Ethics approval and consent to participate

Animal experiments were approved (approval nos. 2023-037 and 2023-054) by the Institutional Committee for Experiments of the Institute of Microbial Chemistry (Numazu, Japan).

Patient consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Abbreviations

CD44s CD44 standard

CD44v CD44 variant

HA hyaluronic acid

mAb monoclonal antibody

ADCC antibody-dependent cellular cytotoxicity

CDC complement-dependent cytotoxicity

FcγR Fcγ receptor

CAR chimeric antigen receptor

FUT8 fucosyl-transferase 8

CHO Chinese hamster ovary

CBIS Cell-Based Immunization and Screening

ESCC esophageal squamous cell carcinoma

PBS phosphate-buffered saline

Figure 1. Flow cytometry using 5-mG2a and C44Mab-46-mG2a. (A) Class-switched and defucosylated mouse IgG2a mAbs, 5-mG2a and C44Mab-46-mG2a, were generated from C44Mab-5 and C44Mab-46 (mouse IgG1), respectively. (B) CHO/CD44s and (C) KYSE770 cells were treated with 10–0.01 µg/ml of 5-mG2a and C44Mab-46-mG2a (red) or buffer control (black), followed by Alexa Fluor 488-conjugated anti-mouse IgG. Fluorescence data were analyzed using the SA3800 Cell Analyzer. mAb, monoclonal antibody.

Figure 2. Evaluation of ADCC activity. The ADCC reporter assay by 5-mG2a and C44Mab-46-mG2a in the presence of (A) CHO/CD44s and (B) KYSE770 cells. Values are presented as the mean ± SD. N.D., not determined; ADCC, antibody-dependent cellular cytotoxicity; mAb, monoclonal antibody.

Figure 3. Evaluation of CDC activity by 5-mG2a and C44Mab-46-mG2a against CHO/CD44s and KYSE770 cells. The CDC induced by 5-mG2a, C44Mab-46-mG2a, or control mouse IgG2a (281-mG2a) against (A) CHO/CD44s and (B) KYSE770 cells. Values are shown as the mean ± SEM. *P<0.05 and **P<0.01; one-way ANOVA with Tukey's multiple comparisons test. CDC, complement-dependent cytotoxicity; mAb, monoclonal antibody.

Figure 4. Antitumor activity of 5-mG2a and C44Mab-46-mG2a against CHO/CD44s xenograft tumor. (A) Measurement of tumor volume in CHO/CD44s xenograft. CHO/CD44s cells (5×106 cells) were injected into mice subcutaneously. On day 7, 100 µg of 5-mG2a and C44Mab-46-mG2a or control mouse IgG2a (281-mG2a) were injected into mice intraperitoneally. On days 14 and 21, additional antibodies were injected. On days 7, 9, 14, 17, 21 and 23 following the inoculation, the tumor volume was measured. Values are presented as the mean ± SEM. *P<0.05 and **P<0.01; two-way ANOVA with Sidak's multiple comparisons test. (B) The weight (left) and appearance (right) of excised CHO/CD44s xenografts on day 23. Values are presented as the mean ± SEM; one-way ANOVA with Tukey's multiple comparisons test. (C) The body weight (left) and appearance (right) of control mouse IgG2a, 5-mG2a, and C44Mab-46-mG2a-treated mice. Scale bar, 1 cm. mAb, monoclonal antibody.

Figure 5. Antitumor activity of 5-mG2a and C44Mab-46-mG2a against KYSE770 ×enograft tumor. (A) Measurement of tumor volume in KYSE770 ×enograft. KYSE770 cells (5×106 cells) were injected into mice subcutaneously. On day 8, 500 µg of 5-mG2a and C44Mab-46-mG2a or control mouse IgG2a (281-mG2a) were injected into mice intraperitoneally. On day 13, additional antibodies were injected. On days 8, 12, and 19 following the inoculation, the tumor volume was measured. Values are presented as the mean ± SEM. **P<0.01; two-way ANOVA with Sidak's multiple comparisons test. (B) The weight (left) and appearance (right) of the excised KYSE770 ×enografts on day 19. Values are presented as the mean ± SEM. *P<0.05; one-way ANOVA with Tukey's multiple comparisons test. (C) The body weight (left) and appearance (right) of control mouse IgG2a, 5-mG2a and C44Mab-46-mG2a-treated mice. Scale bar, 1 cm. mAb, monoclonal antibody.
==== Refs
References

1 Ponta H Sherman L Herrlich PA CD44: From adhesion molecules to signalling regulators Nat Rev Mol Cell Biol 4 33 45 2003 10.1038/nrm1004 12511867
2 Zöller M CD44: Can a cancer-initiating cell profit from an abundantly expressed molecule? Nat Rev Cancer 11 254 267 2011 10.1038/nrc3023 21390059
3 Prochazka L Tesarik R Turanek J Regulation of alternative splicing of CD44 in cancer Cell Signal 26 2234 2239 2014 10.1016/j.cellsig.2014.07.011 25025570
4 Guo Q Yang C Gao F The state of CD44 activation in cancer progression and therapeutic targeting FEBS J 289 7970 7986 2022 10.1111/febs.16179 34478583
5 Zöller M CD44, hyaluronan, the hematopoietic stem cell, and leukemia-initiating cells Front Immunol 6 235 2015 26074915
6 Hassn Mesrati M Syafruddin SE Mohtar MA Syahir A CD44: A multifunctional mediator of cancer progression Biomolecules 11 1850 2021 10.3390/biom11121850 34944493
7 Cirillo N The hyaluronan/CD44 axis: A double-edged sword in cancer Int J Mol Sci 24 15812 2023 10.3390/ijms242115812 37958796
8 Liu Y Wu T Lu D Zhen J Zhang L CD44 overexpression related to lymph node metastasis and poor prognosis of pancreatic cancer Int J Biol Markers 33 308 313 2018 10.1177/1724600817746951 29683068
9 Tao Y Li H Huang R Mo D Zeng T Fang M Li M Clinicopathological and prognostic significance of cancer stem cell markers in ovarian cancer patients: Evidence from 52 studies Cell Physiol Biochem 46 1716 1726 2018 10.1159/000489586 29730663
10 Li L Hao X Qin J Tang W He F Smith A Zhang M Simeone DM Qiao XT Chen ZN Antibody against CD44s inhibits pancreatic tumor initiation and postradiation recurrence in mice Gastroenterology 146 1108 1118 2014 10.1053/j.gastro.2013.12.035 24397969
11 Zhang S Wu CC Fecteau JF Cui B Chen L Zhang L Wu R Rassenti L Lao F Weigand S Kipps TJ Targeting chronic lymphocytic leukemia cells with a humanized monoclonal antibody specific for CD44 Proc Natl Acad Sci USA 110 6127 6132 2013 10.1073/pnas.1221841110 23530247
12 Vey N Delaunay J Martinelli G Fiedler W Raffoux E Prebet T Gomez-Roca C Papayannidis C Kebenko M Paschka P Phase I clinical study of RG7356, an anti-CD44 humanized antibody, in patients with acute myeloid leukemia Oncotarget 7 32532 32542 2016 10.18632/oncotarget.8687 27081038
13 Menke-van der Houven van Oordt CW Gomez-Roca C van Herpen C Coveler AL Mahalingam D Verheul HM van der Graaf WT Christen R Rüttinger D Weigand S First-in-human phase I clinical trial of RG7356, an anti-CD44 humanized antibody, in patients with advanced, CD44-expressing solid tumors Oncotarget 7 80046 80058 2016 10.18632/oncotarget.11098 27507056
14 Todaro M Gaggianesi M Catalano V Benfante A Iovino F Biffoni M Apuzzo T Sperduti I Volpe S Cocorullo G CD44v6 is a marker of constitutive and reprogrammed cancer stem cells driving colon cancer metastasis Cell Stem Cell 14 342 356 2014 10.1016/j.stem.2014.01.009 24607406
15 Verel I Heider KH Siegmund M Ostermann E Patzelt E Sproll M Snow GB Adolf GR van Dongen GA Tumor targeting properties of monoclonal antibodies with different affinity for target antigen CD44V6 in nude mice bearing head-and-neck cancer xenografts Int J Cancer 99 396 402 2002 10.1002/ijc.10369 11992408
16 Orian-Rousseau V Ponta H Perspectives of CD44 targeting therapies Arch Toxicol 89 3 14 2015 10.1007/s00204-014-1424-2 25472903
17 Tijink BM Buter J de Bree R Giaccone G Lang MS Staab A Leemans CR van Dongen GA A phase I dose escalation study with anti-CD44v6 bivatuzumab mertansine in patients with incurable squamous cell carcinoma of the head and neck or esophagus Clin Cancer Res 12 6064 6072 2006 10.1158/1078-0432.CCR-06-0910 17062682
18 Riechelmann H Sauter A Golze W Hanft G Schroen C Hoermann K Erhardt T Gronau S Phase I trial with the CD44v6-targeting immunoconjugate bivatuzumab mertansine in head and neck squamous cell carcinoma Oral Oncol 44 823 829 2008 10.1016/j.oraloncology.2007.10.009 18203652
19 Casucci M Nicolis di Robilant B Falcone L Camisa B Norelli M Genovese P Gentner B Gullotta F Ponzoni M Bernardi M CD44v6-targeted T cells mediate potent antitumor effects against acute myeloid leukemia and multiple myeloma Blood 122 3461 3472 2013 10.1182/blood-2013-04-493361 24016461
20 Porcellini S Asperti C Corna S Cicoria E Valtolina V Stornaiuolo A Valentinis B Bordignon C Traversari C CAR T cells redirected to CD44v6 control tumor growth in lung and ovary adenocarcinoma bearing mice Front Immunol 11 99 2020 10.3389/fimmu.2020.00099 32117253
21 Yamada S Itai S Nakamura T Yanaka M Kaneko MK Kato Y Detection of high CD44 expression in oral cancers using the novel monoclonal antibody, C44Mab-5 Biochem Biophys Rep 14 64 68 2018 29872736
22 Goto N Suzuki H Tanaka T Asano T Kaneko MK Kato Y Development of a novel Anti-CD44 monoclonal antibody for multiple applications against esophageal squamous cell carcinomas Int J Mol Sci 23 5535 2022 10.3390/ijms23105535 35628345
23 Takei J Asano T Suzuki H Kaneko MK Kato Y Epitope mapping of the anti-CD44 monoclonal antibody (C44Mab-46) using alanine-scanning mutagenesis and surface plasmon resonance Monoclon Antib Immunodiagn Immunother 40 219 226 2021 10.1089/mab.2021.0028 34678095
24 Asano T Kaneko MK Takei J Tateyama N Kato Y Epitope mapping of the anti-CD44 monoclonal antibody (C44Mab-46) using the REMAP method Monoclon Antib Immunodiagn Immunother 40 156 161 2021 10.1089/mab.2021.0012 34283655
25 Asano T Kaneko MK Kato Y Development of a novel epitope mapping system: RIEDL insertion for epitope mapping method Monoclon Antib Immunodiagn Immunother 40 162 167 2021 10.1089/mab.2021.0023 34424761
26 Suzuki H Kitamura K Goto N Ishikawa K Ouchida T Tanaka T Kaneko MK Kato Y A Novel anti-CD44 variant 3 monoclonal antibody C44Mab-6 was established for multiple applications Int J Mol Sci 24 8411 2023 10.3390/ijms24098411 37176118
27 Suzuki H Tanaka T Goto N Kaneko MK Kato Y Development of a novel anti-CD44 variant 4 monoclonal antibody C44Mab-108 for immunohistochemistry Curr Issues Mol Biol 45 1875 1888 2023 10.3390/cimb45030121 36975491
28 Kudo Y Suzuki H Tanaka T Kaneko MK Kato Y Development of a novel Anti-CD44 variant 5 monoclonal antibody C44Mab-3 for multiple applications against pancreatic carcinomas Antibodies (Basel) 12 31 2023 10.3390/antib12020031 37218897
29 Ejima R Suzuki H Tanaka T Asano T Kaneko MK Kato Y Development of a novel Anti-CD44 variant 6 monoclonal antibody C44Mab-9 for multiple applications against colorectal carcinomas Int J Mol Sci 24 4007 2023 10.3390/ijms24044007 36835416
30 Suzuki H Ozawa K Tanaka T Kaneko MK Kato Y Development of a novel anti-CD44 variant 7/8 monoclonal antibody, C44Mab-34, for multiple applications against oral carcinomas Biomedicines 11 1099 2023 10.3390/biomedicines11041099 37189717
31 Tawara M Suzuki H Goto N Tanaka T Kaneko MK Kato Y A novel anti-CD44 variant 9 monoclonal antibody C44Mab-1 was developed for immunohistochemical analyses against colorectal cancers Curr Issues Mol Biol 45 3658 3673 2023 10.3390/cimb45040238 37185762
32 Ishikawa K Suzuki H Kaneko MK Kato Y Establishment of a novel anti-CD44 variant 10 monoclonal antibody C44Mab-18 for immunohistochemical analysis against oral squamous cell carcinomas Curr Issues Mol Biol 45 5248 5262 2023 10.3390/cimb45070333 37504249
33 Li G Suzuki H Ohishi T Asano T Tanaka T Yanaka M Nakamura T Yoshikawa T Kawada M Kaneko MK Kato Y Antitumor activities of a defucosylated anti-EpCAM monoclonal antibody in colorectal carcinoma xenograft models Int J Mol Med 51 18 2023 10.3892/ijmm.2023.5221 36660940
34 Nanamiya R Suzuki H Takei J Li G Goto N Harada H Saito M Tanaka T Asano T Kaneko MK Kato Y Development of monoclonal antibody 281-mG2a-f against golden hamster podoplanin Monoclon Antib Immunodiagn Immunother 41 311 319 2022 10.1089/mab.2021.0058 35483059
35 Queiroz AL Dantas E Ramsamooj S Murthy A Ahmed M Zunica ERM Liang RJ Murphy J Holman CD Bare CJ Blocking ActRIIB and restoring appetite reverses cachexia and improves survival in mice with lung cancer Nat Commun 13 4633 2022 10.1038/s41467-022-32135-0 35941104
36 Yamada S Kaneko MK Nakamura T Ichii O Konnai S Kato Y Development of mPMab-1, a mouse-rat chimeric antibody against mouse podoplanin Monoclon Antib Immunodiagn Immunother 36 77 79 2017 10.1089/mab.2017.0002 28387612
37 Garvin D Stecha P Gilden J Wang J Grailer J Hartnett J Fan F Cong M Cheng ZJ Determining ADCC activity of antibody-based therapeutic molecules using two bioluminescent reporter-based bioassays Curr Protoc 1 e296 2021 10.1002/cpz1.296 34787960
38 Takei J Kaneko MK Ohishi T Hosono H Nakamura T Yanaka M Sano M Asano T Sayama Y Kawada M A defucosylated anti-CD44 monoclonal antibody 5-mG2a-f exerts antitumor effects in mouse xenograft models of oral squamous cell carcinoma Oncol Rep 44 1949 1960 2020 33000243
39 Birzele F Voss E Nopora A Honold K Heil F Lohmann S Verheul H Le Tourneau C Delord JP van Herpen C CD44 isoform status predicts response to treatment with anti-CD44 antibody in cancer patients Clin Cancer Res 21 2753 2762 2015 10.1158/1078-0432.CCR-14-2141 25762343
40 Golay J Taylor RP The role of complement in the mechanism of action of therapeutic anti-cancer mAbs Antibodies (Basel) 9 58 2020 10.3390/antib9040058 33126570
41 Reis ES Mastellos DC Ricklin D Mantovani A Lambris JD Complement in cancer: Untangling an intricate relationship Nat Rev Immunol 18 5 18 2018 10.1038/nri.2017.97 28920587
42 Galon J Bruni D Approaches to treat immune hot, altered and cold tumours with combination immunotherapies Nat Rev Drug Discov 18 197 218 2019 10.1038/s41573-018-0007-y 30610226
43 Hiemstra IH Santegoets KCM Janmaat ML De Goeij BECG Ten Hagen W van Dooremalen S Boross P van den Brakel J Bosgra S Andringa G Preclinical anti-tumour activity of HexaBody-CD38, a next-generation CD38 antibody with superior complement-dependent cytotoxic activity EBioMedicine 93 104663 2023 10.1016/j.ebiom.2023.104663 37379657
44 de Jong RN Beurskens FJ Verploegen S Strumane K van Kampen MD Voorhorst M Horstman W Engelberts PJ Oostindie SC Wang G A novel platform for the potentiation of therapeutic antibodies based on antigen-dependent formation of IgG hexamers at the cell surface PLoS Biol 14 e1002344 2016 10.1371/journal.pbio.1002344 26736041
45 Schmudde I Laumonnier Y Köhl J Anaphylatoxins coordinate innate and adaptive immune responses in allergic asthma Semin Immunol 25 2 11 2013 10.1016/j.smim.2013.04.009 23694705
46 Carroll MC Isenman DE Regulation of humoral immunity by complement Immunity 37 199 207 2012 10.1016/j.immuni.2012.08.002 22921118
47 Gogia P Ashraf H Bhasin S Xu Y Antibody-drug conjugates: A review of approved drugs and their clinical level of evidence Cancers (Basel) 15 3886 2023 10.3390/cancers15153886 37568702
48 Arimori T Mihara E Suzuki H Ohishi T Tanaka T Kaneko MK Takagi J Kato Y Locally misfolded HER2 expressed on cancer cells is a promising target for development of cancer-specific antibodies Structure 32 536 549.e5 2024 10.1016/j.str.2024.02.007 38460519
49 Kaneko MK Suzuki H Kato Y Establishment of a novel cancer-specific anti-HER2 monoclonal antibody H2Mab-250/H2CasMab-2 for breast cancers Monoclon Antib Immunodiagn Immunother 43 35 43 2024 10.1089/mab.2023.0033 38563783
50 Kaneko MK Suzuki H Ohishi T Nakamura T Tanaka T Kato Y A cancer-specific monoclonal antibody against HER2 exerts antitumor activities in human breast cancer xenograft models Int J Mol Sci 25 1941 2024 10.3390/ijms25031941 38339219
51 Lodewijk I Dueñas M Paramio JM Rubio C CD44v6, STn & O-GD2: Promising tumor associated antigens paving the way for new targeted cancer therapies Front Immunol 14 1272681 2023 10.3389/fimmu.2023.1272681 37854601
52 Aasted MKM Groen AC Keane JT Dabelsteen S Tan E Schnabel J Liu F Lewis HS Theodoropulos C Posey AD Wandall HH Targeting solid cancers with a cancer-specific monoclonal antibody to surface expressed aberrantly O-glycosylated proteins Mol Cancer Ther 22 1204 1214 2023 10.1158/1535-7163.MCT-23-0221 37451822
