Chimeric Antigen receptor-T (CAR-T) cells targeting Epithelial cell adhesion molecule (EpCAM) can inhibit tumor growth in ovarian cancer mouse model

Ovarian cancer (OC) is one of the most lethal solid tumors with poor prognosis. In 2017, two chimeric antigen receptor-T (CAR-T) cell drugs were approved by the U.S. Food and Drug Administration (FDA), and continuously optimized CAR-T cells therapy might be the novel hope for OC patient. EpCAM are known to be over-expressed in OC cells and could be targeted by CAR-T cells. However, the feasibility of using EpCAM-CAR-T cells to treat OC still needs to be verified. We engineered the 3rd-generation EpCAM-CAR containing a single-chain variable fragment (scFv) EpCAM-scFv that targeting EpCAM, a CD8 transmembrane domain, the costimulatory domains from both CD28 and 4-1BB, and activating domain CD3ζ and then transduced the CAR into T-cells via lentivirus. In addition, the cytotoxicity and cytokine releasing ability of the EpCAM-CAR-T cells against OC cell SKOV3 were verified in vitro. The in vivo data also showed that EpCAM-CAR-T cells significantly reduced the tumor size in OC xenograft mouse models. The anti-tumor activity of EpCAM-CAR-T cells against OC in vitro and in vivo indicated that the CAR-T might provide a promising therapeutic approach to OC.     

Canine CD20 gene

The human CD20 antigen, a 35kDa cell surface nonglycosylated hydrophobic phoshpoprotein is expressed consistently on almost all human B-cells, and its monoclonal antibody is used for the therapy on human B-cell lymphoma. In the present study, canine CD20 gene was cloned and sequenced, and the expression of CD20 mRNA was investigated in canine peripheral blood mononuclear cells (PBMCs), and lymph nodes from healthy dogs, and canine lymphoma cells. Using canine cDNA as a template, full-length of canine CD20 gene was sequenced by 5'-RACE and 3'-RACE methods. The full-length of the cDNA sequence of canine CD20 was 1239bp encoding 297 amino acids. The amino acid sequences of canine CD20 showed 73 and 68% sequence similarities with those of human and mouse, respectively. Canine CD20 was predicted to contain domains of amino acid sequences consisting of two extracellular domains (EM), four transmembrane domains (TM), and three intracellular domains (IC) as in human CD20. Canine CD20 mRNA was detected in PBMCs and lymph node from healthy dogs, and B-cells of canine lymphoma, but not in T-cell lymphoma cells and non-T and non-B-cell lymphoma cells by RT-PCR analysis. From these results, canine CD20 might be targeted for monoclonal antibody therapy against B-cell lymphoma of dogs.     

CD20 expression in normal canine B cells and in canine non-Hodgkin lymphoma

We examined the expression of CD20 in normal canine peripheral blood mononuclear cells, normal canine spleen, and canine non-Hodgkin lymphoma (NHL) to determine the feasibility of using this antigen as a diagnostic aid and as a possible target for therapy. An antibody generated against a C-terminal (intracytoplasmic) epitope of human CD20 recognized proteins of 32-36 kd in normal and malignant canine lymphocytes. This antibody showed restricted membrane binding in a subset of lymphocytes in peripheral blood, in the B-cell regions from a normal canine spleen and lymph node, and in malignant cells from 19 dogs with B-cell NHL, but not from 15 dogs with T-cell NHL. The patterns of CD20 reactivity in these samples overlapped those seen using an antibody that recognizes canine CD79a. This anti-CD20 antibody is therefore suitable as an aid to phenotype canine NHL. In contrast, normal canine B cells were not recognized by any of 28 antibodies directed against the extracellular domains of human CD20 (including the chimeric mouse-human antibody Rituximab) or by any of 12 antibodies directed against the extracellular domains of mouse CD20. Thus, the use of CD20 as a therapeutic target will require the generation of specific antibodies against the extracellular domains of canine CD20.     

Immunohistochemical detection of multiple myeloma 1/interferon regulatory factor 4 (MUM1/IRF-4) in canine plasmacytoma: comparison with CD79a and CD20

Multiple myeloma oncogene 1/interferon regulatory factor 4 (MUM1/IRF4) is involved in lymphoid cell differentiation, particularly in the production of plasma cells. We examined the immunoreactivity of mouse monoclonal antibody Mum-1p to MUM1/IRF4 and compared it with expression of CD79a and CD20 in 109 plasmacytomas in 107 dogs. Tissues had been fixed in formalin and embedded in paraffin. One hundred one of 109 (93.5%) tumors were positive for MUM1/IRF4. The staining was nuclear with weak cytoplasmic reaction. Fifty-nine of 105 (56.2%) plasmacytomas were positive for CD79a; only 21 of 108 (19.4%) cases were positive for CD20. MUM1/IRF4 staining was performed on 139 other tumors including B- and T-cell lymphomas, histiocytic proliferations, mast cell tumors, and melanocytic tumors. The only MUM1/IRF4-positive nonplasmacytic tumors were 10 B-cell lymphomas and 1 anaplastic lymphoma. We conclude the following: 1) Antibody Mum-1p is very specific for canine plasmacytomas, 2) antibody Mum-1p is superior in sensitivity and specificity to CD79a and CD20 for the identification of canine plasmacytomas in formalin-fixed, paraffin-embedded tissues, 3) canine lymphomas that express MUM1/IRF4 are few and usually of B-cell origin, 4) other canine leukocytic and melanocytic tumors do not express MUM1/IRF4, and 5) prospective studies are needed to determine whether the expression of MUM1/IRF4, particularly in lymphomas, has prognostic significance.     

IL‐4 downregulates expression of the target receptor CD30 in neoplastic canine mast cells

CD30 is a novel therapeutic target in human mast cell (MC) neoplasms. In this ‘comparative oncology’ study, we examined CD30 expression and regulation in neoplastic canine MC using a panel of immunomodulatory cytokines [interleukin‐2 (IL‐2), IL‐4, IL‐5, IL‐6, IL‐13 and stem cell factor (SCF)] and the canine mastocytoma cell lines NI‐1 and C2. Of all cytokines tested IL‐4 was found to downregulate expression of CD30 in NI‐1 and C2 cells. We also found that the CD30‐targeting antibody‐conjugate brentuximab vedotin induces growth inhibition and apoptosis in both MC lines. Next, we asked whether IL‐4‐induced downregulation of CD30 interferes with brentuximab vedotin‐effects. Indeed, pre‐incubation of NI‐1 cells with IL‐4 decreased responsiveness towards brentuximab vedotin. To overcome IL‐4‐mediated resistance, we applied drug combinations and found that brentuximab vedotin synergizes with the Kit‐targeting drugs masitinib and PKC412 in inhibiting growth of NI‐1 and C2 cells. In summary, CD30 is a new marker and IL‐4‐regulated target in neoplastic canine MC.     

RNA‐transfected CD40‐activated B cells as a vaccine strategy in canine malignancies

Introduction: Cell‐based vaccine strategies using dendritic cells as cellular adjuvant have entered phase III trials in humans and have been found to be safe, feasible, and potentially efficacious. Canine patients are generally smaller than adult human patients, which makes production of canine dendritic cell (DC) vaccines problematic, given patient size and the small number of available DC precursors. Here we describe feasibility studies of a novel cell‐based vaccine strategy which uses CD40‐activated B‐cells (CD40‐B) loaded with RNA. This strategy is based on our observations that RNA‐transfected human CD40‐B can drive anti‐tumor T cell responses. One advantage of using CD40‐B cells is the ability to expand this cell population ex vivo, allowing for the numbers of cells required for therapeutic vaccines. Methods: Twenty milliliters of blood were drawn from 6 normal dogs and 5 canine lymphoma patients. Peripheral blood mononuclear cells were separated by Ficoll centrifugation. Culture conditions for B cell activation were optimized using CD40‐ligand, canine IL‐4, and Toll‐like receptor stimulus with CpGoligodinucleotides (ODN). Cyclosporine was added to eliminate peripheral T lymphocytes. Proliferation and activation of CD40‐B cells were demonstrated by CFSE dilution of B cells quantified by flow cytometry. Gene transfer was achieved by mRNA electroporation. Results: Marked in vitro stimulation and proliferation of canine peripheral B cells were achieved with soluble trimeric CD40L, canine IL‐4, and ODN. CD40‐B cells showed dramatic upregulation of MHC class II molecules and CD21 (B‐cell activation marker). After two weeks in culture, cells were negative for CD3 and CD4. Canine CD40‐B cells were efficiently transfected with mRNA, with >60% of CD40‐B expressing green fluorescent protein after GFP mRNA electroporation. Conclusion: RNA‐transfected CD40‐B cells can be efficiently generated from normal and tumor‐bearing dogs. These results provide rationale to test tumor RNA‐transfected CD40‐B as a novel therapeutic approach to treating canine malignancies. Clinical trials in canine lymphoma have been proposed.     

Hematoporphyrin monomethyl ether combined with He–Ne laser irradiation-induced apoptosis in canine breast cancer cells through the mitochondrial pathway

Hematoporphyrin monomethyl ether (HMME) combined with He-Ne laser irradiation is a novel and promising photodynamic therapy (PDT)-induced apoptosis that can be applied in vitro on canine breast cancer cells. However, the exact pathway responsible for HMME-PDT in canine breast cancer cells remains unknown. CHMm cells morphology and apoptosis were analyzed using optical microscope, terminal deoxynucleotidyl transferase dUTP nick end labeling fluorescein staining and DNA ladder assays. Apoptotic pathway was further confirmed by Real-time-polymerase chain reaction and Western blotting assays. Our results showed that HMME-PDT induced significant changes in cell morphology, such as formation of cytoplasmic vacuoles and the gradual rounding of cells coupled with decreased size and detachment. DNA fragmentation and cell death was shown to occur in a time-dependent manner. Furthermore, HMME-PDT increased the activities of caspase-9 and caspase-3, and released cytochrome c from mitochondria into the cytoplasm. HMME-PDT also significantly increased both mRNA and protein levels of Bax and decreased P53 gene expression in a time-dependent manner, while the mRNA and protein expression of Bcl-2 were repressed. These alterations suggest that HMME-PDT induced CHMm cell apoptosis via the mitochondrial apoptosis pathway and had anti-canine breast cancer effects in vitro.     

Brucella canis induces canine CD4+ T cells multi-cytokine Th1/Th17 production via dendritic cell activation

Brucella canis is a small intracellular Gram-negative bacterium that frequently leads to chronic infections highly resistant to antibiotic therapy in dogs. Also, it causes mild human brucellosis compared to other zoonotic Brucella spp. Herein we characterize the cellular immune response elicited by B. canis by analysing human and canine CD4⁺ T cells after stimulation with autologous monocyte-derived dendritic cells (MoDCs). Human and canine B. canis-primed MoDCs stimulated autologous CD4⁺ T cells; however, a Th1 response was triggered by human MoDCs, whereas canine MoDCs induced Th1/Th17 responses, with increased CD4⁺ T cells producing IFN-γ and IL-17A simultaneously. Each pattern of cellular response may contribute to host susceptibility, helping to understand the differences in B. canis virulence between these two hosts. In addition, other aspects of canine immunology are unveiled by highlighting the participation of IL-17A-producing canine MoDCs and CD4⁺ T cells producing IFN-γ and IL-17A.     

Tumour‐infiltrating lymphocytes in canine melanocytic tumours: An investigation on the prognostic role of CD3+ and CD20+ lymphocytic populations

The study of the immune response in several types of tumours has been rapidly increasing in recent years with the dual aim of understanding the interactions between neoplastic and immune cells and their importance in cancer pathogenesis and progression, as well as identifying targets for cancer immunotherapy. Despite being considered one of the most immunogenic tumour types, melanoma can progress in the presence of abundant lymphocytic infiltration, therefore suggesting that the immune response is not able to efficiently control tumour growth. The purpose of this study was to investigate whether the density, distribution and grade of tumour‐infiltrating lymphocytes (TILs) in 97 canine melanocytic tumours is associated with histologic indicators of malignancy and can be considered a prognostic factor in the dog. As a further step in the characterization of the immune response in melanocytic tumours, an immunohistochemical investigation was performed to evaluate the two main populations of TILs, T‐lymphocytes (CD3⁺) and B‐lymphocytes (CD20⁺). The results of our study show that TILs are present in a large proportion of canine melanocytic tumours, especially in oral melanomas, and that the infiltrate is usually mild. The quantity of CD20⁺ TILs was significantly associated with some histologic prognostic factors, such as the mitotic count, the cellular pleomorphism and the percentage of pigmented cells. Remarkably, a high infiltration of CD20⁺ TILs was associated with tumour‐related death, presence of metastasis/recurrence, shorter overall and disease‐free survival, increased hazard of death and of developing recurrence/metastasis, hence representing a potential new negative prognostic factor in canine melanocytic tumours.     

Characterization of spheres derived from canine mammary gland adenocarcinoma cell lines

There is increasing evidence for the presence of cancer stem cells in several solid tumors, and these cancer stem cells have a potential role in tumor initiation, aggression, and recurrence. The stem cell-like properties of spheres derived from canine mammary tumors remain largely elusive. We attempted to induce sphere formation using four cell lines of canine mammary adenocarcinoma, and characterized the spheres derived from a CHMp line in vitro and in vivo. The CHMp-derived spheres showed predominantly CD44⁺CD24⁻ population, higher expression of stem cell-related genes, such as CD133, Notch3 and MDR, and higher resistance to doxorubicin compared with the CHMp-derived adherent cells. Xenograft transplantations in nude mice demonstrated that only 1 × 10⁴ sphere cells were sufficient for tumor formation. Use of the sphere assay on these sphere-derived tumors showed that sphere-forming cells were present in the tumors, and were maintained in serial transplantation. We propose that spheres derived from canine mammary adenocarcinoma cell lines possess a potential characteristic of cancer stem cells. Spheres derived from canine mammary tumors could be a powerful tool with which to investigate novel therapeutic drugs and to elucidate the molecular and cellular mechanisms that underlie tumorigenesis.     

Isolation and characterization of canine umbilical cord blood-derived mesenchymal stem cells

Human umbilical cord blood-derived mesenchymal stem cells (MSCs) are known to possess the potential for multiple differentiations abilities in vitro and in vivo. In canine system, studying stem cell therapy is important, but so far, stem cells from canine were not identified and characterized. In this study, we successfully isolated and characterized MSCs from the canine umbilical cord and its fetal blood. Canine MSCs (cMSCs) were grown in medium containing low glucose DMEM with 20% FBS. The cMSCs have stem cells expression patterns which are concerned with MSCs surface markers by fluorescence-activated cell sorter analysis. The cMSCs had multipotent abilities. In the neuronal differentiation study, the cMSCs expressed the neuronal markers glial fibrillary acidic protein (GFAP), neuronal class III β tubulin (Tuj-1), neurofilament M (NF160) in the basal culture media. After neuronal differentiation, the cMSCs expressed the neuronal markers Nestin, GFAP, Tuj-1, microtubule-associated protein 2, NF160. In the osteogenic & chondrogenic differentiation studies, cMSCs were stained with alizarin red and toluidine blue staining, respectively. With osteogenic differentiation, the cMSCs presented osteoblastic differentiation genes by RT-PCR. This finding also suggests that cMSCs might have the ability to differentiate multipotentially. It was concluded that isolated MSCs from canine cord blood have multipotential differentiation abilities. Therefore, it is suggested that cMSCs may represent a be a good model system for stem cell biology and could be useful as a therapeutic modality for canine incurable or intractable diseases, including spinal cord injuries in future regenerative medicine studies.     

Identification of tumor-initiating cells in a canine hepatocellular carcinoma cell line

Tumor-initiating cells (TICs) or cancer stem cells (CSCs), a small subset of tumor cells, are involved in tumor initiation, progression, recurrence and metastasis. In human hepatocellular carcinoma (HCC), TICs are enriched with cell surface markers and have the ability to self-renew and differentiate tumors at a high frequency. We established a canine HCC cell line, HCC930599, and analyzed it for stem and progenitor cell marker expression using flow cytometry. HCC930599 showed high CD44 and CD29, moderate CD90, and low CD133, CD34, CD24, CD117, and CD13 expression. CD90⁺CD44⁺ and CD90⁻CD44⁺ cells were characterized using the in vitro sphere assay and an in vivo transplant model. CD90⁺CD44⁺ cells acquired enhanced self-renewal capacity, proliferative activity and tumourigenicity compared with CD90⁻CD44⁺ cells, suggesting that TICs exist in the HCC930599 cell line and that CD90 is a marker for enriched TICs. Understanding TIC characteristics may help elucidate hepatic carcinogenesis and HCC therapy development.     

Interleukin-10 inhibits lipopolysaccharide-induced upregulation of tissue factor in canine peripheral blood monocytes

The potentially fatal hemostatic disorder of disseminated intravascular coagulation (DIC) is initiated in bacterial sepsis by lipopolysaccharide (LPS)-induced tissue factor (TF) expression on monocytes. Interleukin-10 (IL-10) is a potent inhibitory cytokine that downregulates monocyte inflammatory and procoagulant responses. We hypothesized that canine recombinant IL-10 (rIL-10) would inhibit LPS-induced TF upregulation on canine monocytes in a dose-dependent manner. Canine peripheral blood mononuclear cells (PBMC), obtained by double-density gradient centrifugation, and monocytes, purified from PBMC by immunomagnetic bead separation with an anti-canine CD14 antibody (Ab), were stimulated in suspension with LPS (0.1-1000ng/mL) for various times. Recombinant IL-10 (10-5000pg/mL) was added with LPS or up to 2h later. Tissue factor procoagulant activity was measured by cleavage of a chromogenic substrate by activated Factor X generated by the TF-factor VII complex. We found that rIL-10, when given concurrently or 1h after LPS, strongly inhibited LPS-induced TF procoagulant activity in canine PBMC and monocytes. This inhibition was dose-dependent and blocked by an anti-canine IL-10 Ab. Our results indicate that rIL-10 effectively inhibits LPS-induced TF upregulation in canine monocytes and could potentially be useful in limiting the development of DIC in dogs with endotoxemia.     

CD34+, CD41+ acute megakaryoblastic leukemia in a dog

A clinically normal, 5-year-old intact female German Shepherd dog was presented to the local veterinarian to be spayed. Results of a preoperative CBC included mild nonregenerative anemia, severe thrombocytopenia, and 17% unclassified cells. On cytologic examination of aspirates from the dog's enlarged spleen and peripheral lymph nodes, a population of primitive round cells that occasionally resembled megakaryocytes was observed. A bone marrow aspirate specimen was markedly hypercellular with approximately 65% of marrow cells comprising a homogeneous population of immature hematopoietic cells similar to those found in the spleen, lymph nodes, and peripheral blood. Using immunocytochemical stains with canine-specific antibodies, all neoplastic cells strongly expressed cytoplasmic CD41 and 20-70% of the neoplastic cells expressed CD34 weakly to moderately. Rare (<0.5%) neoplastic cells weakly expressed vWF. The cells were negative for all other markers. Based on these results and the morphology of the neoplastic cells, a diagnosis of acute megakaryoblastic leukemia (AMegL) was made. In spite of treatment, results of a CBC performed 1 week later indicated progressive anemia and thrombocytopenia, and the dog was euthanized. To our knowledge, this report documents the first case of canine AMegL diagnosed with both anti-canine CD34 and CD41 antibodies.     

The role of rituximab in the treatment of canine lymphoma: an ex vivo evaluation

Targeting the CD20 receptor that is common to many B-cell Non-Hodgkin's Lymphoma subtypes in people, rituximab is a chimeric monoclonal antibody which has significantly improved disease-free survival rates compared with the use of cytotoxic agents alone. This study evaluated ex vivo canine B cell binding and depletion by rituximab with flow cytometric technique as possible proof of concept for treatment of canine lymphoma. Despite immunohistochemistry supporting CD20 expression, rituximab did not bind or deplete canine B cells and it is unlikely that it will be added to the armamentarium of treatment options for canine lymphoma.     

Canine normal corneal epithelium bears a large population of CD45-positive cells

This investigation sought to identify the presence of immune cells in normal canine corneal epithelium. A whole-mount immunofluorescence study of normal canine epithelium using monoclonal antibodies against CD45, CD11c, CD1c and MHC class II was performed. CD45-positive cells were located in all epithelial layers throughout the cornea, occurring in greater numbers (51.98 ± 4.1/mm²) at the periphery and decreasing towards the central region (11.8 ± 3.1/mm²). CD11c-positive cells were also observed, but were fewer in number. The findings show that the normal canine cornea carries a significant number of cells of immune origin; these cells seem to be of an inactive phenotype as they do not express MHC class II. Further studies are needed to determine whether these cells can express co-stimulatory molecules and act as antigen presenting cells if stimulated.     

A protocol to guide development of a sensitive ELISA for canine erythropoietin

Background: The determination of canine erythropoietin (EPO) concentration is crucial for monitoring the effect of human recombinant (hr) EPO therapy in dogs with chronic renal failure. Current assays are not specific for canine EPO and not sensitive enough to detect physiologic EPO levels in dogs.
Objective: The objective of this study was to develop a simple and sensitive ELISA for canine EPO that could serve as a starting point for developing a commercially available assay.
Methods: The ELISA was based on a mouse monoclonal antibody (mAb) and a rabbit polyclonal antibody (pAb) using 2 different immunization techniques: gene electrotransfer (GET) to generate the pAb and multiple antigen peptides (MAPs) to generate the mAb. The ELISA was performed using both EPO obtained from HeLa cells transfected with an expression plasmid encoding canine EPO and canine plasma with known concentrations of EPO.
Results: The ELISA standard curve was linear for canine EPO concentrations of 7–66 mU/ml. Coefficients of variation were about 10%. No cross-reactivity between canine EPO and hrEPO was detected.
Conclusions: Using novel GET and MAP technology, we developed a sensitive and specific ELISA for canine EPO that can be used to guide future clinical applications for EPO detection and monitoring in dogs.     

Identification of the feline CD63 homologue using retrovirus-mediated expression cloning

Recently, we combined a retrovirus-mediated expression cloning with a simple screening method using non-adherent cells and panning [Anal. Biochem. 315 (2003) 138]. In this study, we applied this method to identify the antigen recognized by an uncharacterized monoclonal antibody raised against a feline cell line, and identified it as the feline homologue of CD63. This simple method is useful for characterizing unknown antibodies that recognize cell surface molecules. Furthermore, the monoclonal antibody identified as an anti-feline CD63 antibody will be useful for studying feline molecular function(s).     

A monoclonal antibody against a canine CD45 homologue: analysis of tissue distribution, biochemical properties and in vitro immunological activity

This report describes the characterisation of a monoclonal antibody (mAb), AB6, which recognises specifically a cluster of canine leukocyte surface molecules. The immunogen used for obtaining the AB6 mAb was a lysate of canine peripheral blood mononuclear cells (PBMC). This novel mAb belongs to the IgG2a isotype, and reacted in Western blot with four different canine leukocyte glycoproteins with apparent molecular weights of 180, 190, 205 and 220 kDa. The AB6 mAb recognised the majority of canine peripheral blood leukocytes as determined by flow cytometry (97%). It also exhibited a broad reactivity pattern against lymphoid and myeloid cells, inhibited the proliferation of mitogen-stimulated canine PBMC and did not recognise human PBMC and murine splenocytes. The biochemical properties, cell and tissue specificity, and in vitro biological activity of the AB6 mAb indicate that it recognises a canine CD45 homologue. The mAb could become a valuable diagnostic and research tool for the evaluation of immune functions in dogs.     

The enhancement of Th1 immune response by anti-PD-L1 antibody in cattle infected with Mycobacterium avium subsp. paratuberculosis

Johne’s disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic enteritis of ruminants. Previous studies have shown that programmed death-ligand 1 (PD-L1) is associated with the disease progression, and PD-L1 blockade activates MAP-specific Th1 responses in vitro. Here, we performed anti-PD-L1 antibody administration using 2 MAP-infected cattle at the late subclinical stage of infection. After administration, bacterial shedding was reduced or maintained at a low level. Additionally, MAP-specific Th1 cytokine production was upregulated, and CD69 expression was increased in T cells. Collectively, the treatment has a potential as a novel control method against Johne’s disease.