a-real-time-potency-assay-for-chimeric-antigen-receptor-t-cells

A Real-time Potency Assay for Chimeric Antigen Receptor T Cells Targeting Solid and Hematological Cancer Cells

Chimeric antigen receptor (CAR) T-cell therapy for cancer has achieved significant clinical benefit for resistant and refractory hematological ...

ProMab Biotechnologies. Inc

Autologous T cells expressing chimeric antigen receptors (CARs) specific for CD19 have demonstrated remarkable efficacy as therapeutics for B cell malignancies. In the present study, we generated FLAG-tagged CD19-specific CAR-T cells (CD19-FLAG) and compared them to their non-tagged counterparts for their effects on solid and hematological cancer cells  and . For solid tumors, we used HeLa cervical carcinoma cells engineered to overexpress CD19 (HeLa-CD19), and for hematological cancer we used Raji Burkitt's lymphoma cells, which endogenously express CD19. Like non-tagged CD19 CAR-T cells, CD19-FLAG CAR-T cells expanded in culture >100-fold and exhibited potent cytolytic activity against both HeLa-CD19 and Raji cells . CD19-FLAG CAR-T cells also secreted significantly more IFN-gamma and IL-2 than the control T cells. , CD19-FLAG CAR-T cells significantly blocked the growth of HeLa-CD19 solid tumors, increased tumor cleaved caspase-3 levels, and expanded systemically. CD19-FLAG CAR-T cells also significantly reduced Raji tumor burden and extended mouse survival. These results demonstrate the strong efficacy of FLAG-tagged CD19 CAR-T cells in solid and hematological cancer models.

FLAG-tagged CD19-specific CAR-T cells eliminate CD19-bearing solid tumor cells  and .

CD47 is a glycoprotein of the immunoglobulin superfamily that is often overexpressed in different types of hematological and solid cancer tumors and plays important role in blocking phagocytosis, increased tumor survival, metastasis and angiogenesis. In the present report, we designed CAR (chimeric antigen receptor)-T cells that bind CD47 antigen. We used ScFv (single chain variable fragment) from mouse CD47 antibody to generate CD47-CAR-T cells for targeting different cancer cell lines. CD47-CAR-T cells effectively killed ovarian, pancreatic and other cancer cells and produced high level of cytokines that correlated with expression of CD47 antigen. In addition, CD47-CAR-T cells significantly blocked BxPC3 pancreatic xenograft tumor growth after intratumoral injection into NSG mice. Moreover, we humanized mouse CD47 ScFv and showed that it effectively bound CD47 antigen. The humanized CD47-CAR-T cells also specifically killed ovarian, pancreatic, and cervical cancer cell lines and produced IL-2 that correlated with expression of CD47. Thus, CD47-CAR-T cells can be used as a novel cellular therapeutic agent for treating different types of cancer.

CD47-CAR-T Cells Effectively Kill Target Cancer Cells and Block Pancreatic Tumor Growth.

T cells expressing Chimeric antigen receptors or CAR-T cells are used as a novel treatment against hematological and solid cancers. In this report, we designed CAR with glucocorticoid-induced TNFR-related protein (GITR) co-stimulatory domain to study its ability to co-activate CAR-T cells. EGFR-GITR-CD3 CAR-T cells were cytotoxic against EGFR-positive: pancreatic and ovarian cancer cells but not against EGFR-negative cancer cells. The cytotoxic activity of EGFR-GITR-CD3 CAR-T cells was comparable or better than EGFR-28-CD3 or EGFR-41BB-CD3 CAR-T cells. We designed also EGFR-CD3-GITR-CAR and EGFR-ΔGITR-CD3 with deleted 184-192 amino-acids of co-stimulatory GITR domain, and showed that EGFR-GITR-CD3 had significantly higher cytotoxic activity against EGFR-positive cells. The EGFR-GITR-CD3 cells secreted significantly higher levels of IFN-gamma than EGFR-CD3-GITR and EGFR-ΔGITR-CD3 cells. In addition, Mesothelin-GITR-CD3 CAR-T cells also killed mesothelin-positive ovarian cancer cell lines, and pancreatic cancer cells. Moreover, CD19-GITR-CD3 CAR-T cells had significant cytotoxic activity against CD19-positive cancer cells  and in Raji xenograft tumors . Thus, our results clearly show that GITR co-stimulatory domain can be used as a novel co-stimulatory domain in CAR-T cells.

GITR domain inside CAR co-stimulates activity of CAR-T cells against cancer.

The cell-surface protein B cell maturation antigen (BCMA, CD269) has emerged as a promising target for CAR-T cell therapy for multiple myeloma. In order to create a novel BCMA CAR, we generated a new BCMA monoclonal antibody, clone 4C8A. This antibody exhibited strong and selective binding to human BCMA. BCMA CAR-T cells containing the 4C8A scFv were readily detected with recombinant BCMA protein by flow cytometry. The cells were cytolytic for RPMI8226, H929, and MM1S multiple myeloma cells and secreted high levels of IFN-γ in vitro. BCMA-dependent cytotoxicity and IFN-γ secretion were also observed in response to CHO (Chinese Hamster Ovary)-BCMA cells but not to parental CHO cells. In a mouse subcutaneous tumor model, BCMA CAR-T cells significantly blocked RPMI8226 tumor formation. When BCMA CAR-T cells were given to mice with established RPMI8226 tumors, the tumors experienced significant shrinkage due to CAR-T cell activity and tumor cell apoptosis. The same effect was observed with 3 humanized BCMA-CAR-T cells in vivo. These data indicate that novel CAR-T cells utilizing the BCMA 4C8A scFv are effective against multiple myeloma and warrant future clinical development.

CAR-T Cells Based on Novel BCMA Monoclonal Antibody Block Multiple Myeloma Cell Growth.

T cells engineered with chimeric antigen receptors (CARs) are emerging as powerful cancer immunotherapies. Remarkable efficacies have been demonstrated in treating B-cell malignancies with CAR-T cells, leading to the FDA's first approval of gene therapy. Currently, numerous clinical trials for hematological malignancies and solid tumors are underway worldwide. Production of CAR-T cells with proper qualities is essential for CAR-T success in vivo. Here we detail optimized protocols for the generation of CAR-T cells for preclinical studies using lentiviral gene transfer, expansion of CAR-T cells in culture, detection of CAR expression, and evaluation of CAR-T cellular cytotoxicity in vitro.

Generation of CAR-T Cells for Cancer Immunotherapy.

Hypoxia is a major characteristic of the solid tumor microenvironment. To understand how chimeric antigen receptor-T cells (CAR-T cells) function in hypoxic conditions, we characterized CD19-specific and BCMA-specific human CAR-T cells generated in atmospheric (18% oxygen) and hypoxic (1% oxygen) culture for expansion, differentiation status, and CD4:CD8 ratio. CAR-T cells expanded to a much lower extent in 1% oxygen than in 18% oxygen. Hypoxic CAR-T cells also had a less differentiated phenotype and a higher CD4:CD8 ratio than atmospheric CAR-T cells. CAR-T cells were then added to antigen-positive and antigen-negative tumor cell lines at the same or lower oxygen level and characterized for cytotoxicity, cytokine and granzyme B secretion, and PD-1 upregulation. Atmospheric and hypoxic CAR-T cells exhibited comparable cytolytic activity and PD-1 upregulation; however, cytokine production and granzyme B release were greatly decreased in 1% oxygen, even when the CAR-T cells were generated in atmospheric culture. Together, these data show that at solid tumor oxygen levels, CAR-T cells are impaired in expansion, differentiation and cytokine production. These effects may contribute to the inability of CAR-T cells to eradicate solid tumors seen in many patients.

Hypoxia Selectively Impairs CAR-T Cells In Vitro.

Chimeric antigen receptor (CAR) T cell immunotherapy has demonstrated clinical success in treatment of B-cell hematologic cancers. In this study, we compared human Transferrin epitope tagged CAR-T cells with non-tagged CAR-T cells for cytotoxicity, IFN-gamma secretion and tumor clearance in NSG mice. CD19-TF-CAR-T cells had similar cytotoxicity  to CD19-CAR-T cells against cells expressing CD19 antigen: exogenously CD19 Hela cells and endogenously CD19 Raji cells. In addition, CD22-TF CAR-T cells were similarly cytotoxic against CD22 CHO cells and CD22Raji cells. Both CD19-TF or CD22-TF-CAR-T cells secreted less IFN-gamma as compared to non-tagged CAR-T cells. In a Raji xenograft NSG mouse model, CD19-TF-CAR-T cells were as effective as CD19-CAR-T cells in reducing tumor growth and extending mouse survival. The results show that CD19-TF-CAR-T cells can be monitored using TF antibody  and , and that these cells effectively killed Raji cells  and  with reduced secretion of IFN-gamma. Thus, these TF-tagged CAR-T cells might have improved safety and provide a basis for future clinical studies.

Transferrin epitope-CD19-CAR-T cells effectively kill lymphoma cells  and .

CAR-T (chimeric antigen receptor T cells) immunotherapy is effective in many hematological cancers; however, efficacy in solid tumors is disappointing. Doublecortin-like kinase 1 (DCLK1) labels tumor stem cells (TSCs) in genetic mouse models of colorectal cancer (CRC). Here, we describe a novel CAR-T targeting DCLK1 (CBT-511; with our proprietary DCLK1 single-chain antibody variable fragment) as a treatment strategy to eradicate CRC TSCs. The cell surface expression of DCLK1 and cytotoxicity of CBT-511 were assessed in CRC cells (HT29, HCT116, and LoVo). LoVo-derived tumor xenografts in NOD Scid gamma (NSG)mice were treated with CBT-511 or mock CAR-T cells. Adherent CRC cells express surface DCLK1 (two-dimensional, 2D). A 4.5-fold increase in surface DCLK1 was observed when HT29 cells were grown as spheroids (three-dimensional, 3D). CBT-511 induced cytotoxicity (2D;  < 0.0001), and increased Interferon gamma (IFN-γ) release in CRC cells (2D) compared to mock CAR-T ( < 0.0001). Moreover, an even greater increase in IFN-γ release was observed when cells were grown in 3D. CBT-511 reduced tumor growth by approximately 50 percent compared to mock CAR-T. These data suggest that CRC cells with increased clonogenic capacity express increased surface DCLK1. A DCLK1-targeted CAR-T can induce cytotoxicity in vitro and inhibit xenograft growth in vivo.

DCLK1 Monoclonal Antibody-Based CAR-T Cells as a Novel Treatment Strategy against Human Colorectal Cancers.

Placental alkaline phosphatase, PLAP encoded by  gene in humans is mainly expressed in placenta and testis, and not expressed in any other normal tissues. PLAP is overexpressed in colorectal cancers which makes it an attractive target for CAR (chimeric antigen receptor)-T cell therapy. PLAP mRNA expression was detected in 21.5% (25 out of 116) of colorectal cancer cell lines and this expression was confirmed by FACS at the protein level. In addition, IHC staining on primary colorectal cancer tumors demonstrated PLAP expression in >20% of colorectal cancer tumors. We generated mouse and humanized PLAP ScFv-CAR-T cells and demonstrated high specificity against PLAP-positive colon cancer cells using RTCA (real-time cytotoxicity assay) and IFN-gamma secretion. In addition, humanized-CAR-T cells significantly decreased Lovo xenograft tumor growth . The combination of hPLAP-CAR-T cells with PD-1, PD-L1 or LAG-3 checkpoint inhibitors significantly increased the activity of hPLAP-CAR-T cells. This study demonstrates ability of novel PLAP-CAR-T cells to kill colorectal cancers and that the extent of killing can be increased by combination with checkpoint inhibitors.

PLAP -CAR T cells mediate high specific cytotoxicity against colon cancer cells.

CD19 and CD37 proteins are highly expressed in B-cell lymphoma and have been successfully targeted with different monotherapies, including chimeric antigen receptor (CAR)-T cell therapy. The goal of this study was to target lymphoma with novel CD37, humanized CD37, and bi-specific humanized CD37-CD19 CAR-T cells. A novel mouse monoclonal anti-human CD37 antibody (clone 2B8D12F2D4) was generated with high binding affinity for CD37 antigen (KD = 1.6 nM). The CD37 antibody specifically recognized cell surface CD37 protein in lymphoma cells and not in multiple myeloma or other types of cancer. The mouse and humanized CD37-CAR-T cells specifically killed Raji and CHO-CD37 cells and secreted IFN-gamma. In addition, we generated bi-specific humanized hCD37-CD19 CAR-T cells that specifically killed Raji cells, CHO-CD37, and Hela-CD19 cells and did not kill control CHO or Hela cells. Moreover, the hCD37-CD19 CAR-T cells secreted IFN-gamma against CD37-positive and CD19-positive target CHO-CD37, Hela-CD19 cells, respectively, but not against CD19 and CD37-negative parental cell line. The bi-specific hCD37-CD19 significantly inhibited Raji xenograft tumor growth and prolonged mouse survival in NOD scid gamma mouse (NSG) mouse model. This study demonstrates that novel humanized CD37 and humanized CD37-CD19 CAR-T cells specifically targeted either CD37 positive or CD37 and CD19-positive cells and provides a basis for future clinical studies.

Novel CD37, Humanized CD37 and Bi-Specific Humanized CD37-CD19 CAR-T Cells Specifically Target Lymphoma.

Multiple myeloma (MM) is a hematological cancer caused by abnormal proliferation of plasma cells in the bone marrow, and novel types of treatment are needed for this deadly disease. In this study, we aimed to develop novel CS1 CAR-T cells and bispecific CS1-BCMA CAR-T cells to specifically target multiple myeloma. We generated a new CS1 (CD319, SLAM-7) antibody, clone (7A8D5), which specifically recognized the CS1 antigen, and we applied it for the generation of CS1-CAR. CS1-CAR-T cells caused specific killing of CHO-CS1 target cells with secretion of IFN-gamma and targeted multiple myeloma cells. In addition, bispecific CS1-BCMA-41BB-CD3 CAR-T cells effectively killed CHO-CS1 and CHO-BCMA target cells, killed CS1/BCMA-positive multiple myeloma cells, and secreted IFN-gamma. Moreover, CS1-CAR-T cells and bispecific CS1-BCMA CAR-T cells effectively blocked MM1S multiple myeloma tumor growth in vivo. These data for the first time demonstrate that novel CS1 and bispecific CS1-BCMA-CAR-T cells are effective in targeting MM cells and provide a basis for future clinical trials.

Novel CS1 CAR-T Cells and Bispecific CS1-BCMA CAR-T Cells Effectively Target Multiple Myeloma.

The epithelial cell adhesion molecule (EpCAM) is often overexpressed in many types of tumors, including colorectal cancer. We sequenced and humanized an EpCAM mouse antibody and used it to develop bispecific EpCAM-CD3 antibodies. Three different designs were used to generate bispecific antibodies such as EpCAM-CD3 CrossMab knob-in-hole, EpCAM ScFv-CD3 ScFv (BITE), and EpCAM ScFv-CD3 ScFv-human Fc designs. These antibody designs showed strong and specific binding to the EpCAM-positive Lovo cell line and T cells, specifically killed EpCAM-positive Lovo cells and not EpCAM-negative Colo741 cells in the presence of T cells, and increased T cells' IFN-gamma secretion in a dose-dependent manner. In addition, transfection of HEK-293 cells with EpCAM ScFv-CD3 ScFv human Fc mRNA-LNPs resulted in antibody secretion that killed Lovo cells and did not kill EpCAM-negative Colo741 cells. The antibody increased IFN-gamma secretion against Lovo target cells and did not increase it against Colo741 target cells. EpCAM-CD3 hFc mRNA-LNP transfection of several cancer cell lines (A1847, C30, OVCAR-5) also demonstrated functional bispecific antibody secretion. In addition, intratumoral delivery of the EpCAM-CD3 human Fc mRNA-LNPs into OVCAR-5 tumor xenografts combined with intravenous injection of T cells significantly blocked xenograft tumor growth. Thus, EpCAM-CD3 hFc mRNA-LNP delivery to tumor cells shows strong potential for future clinical studies.

mRNA-Lipid Nanoparticle (LNP) Delivery of Humanized EpCAM-CD3 Bispecific Antibody Significantly Blocks Colorectal Cancer Tumor Growth.

Natural killer (NK) cells are cytotoxic lymphocytes that are critical for the innate immune system. Engineering NK cells with chimeric antigen receptors (CARs) allows CAR-NK cells to target tumor antigens more effectively. In this report, we present novel CAR mRNA-LNP (lipid nanoparticle) technology to effectively transfect NK cells expanded from primary PBMCs and to generate functional CAR-NK cells. CD19-CAR mRNA and BCMA-CAR mRNA were embedded into LNPs that resulted in 78% and 95% CAR expression in NK cells, respectively. BCMA-CAR-NK cells after transfection with CAR mRNA-LNPs killed multiple myeloma RPMI8226 and MM1S cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner in vitro. In addition, CD19-CAR-NK cells generated with CAR mRNA-LNPs killed Daudi and Nalm-6 cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner. Both BCMA-CAR-NK and CD19-CAR-NK cells showed significantly higher cytotoxicity, IFN-gamma, and Granzyme B secretion compared with normal NK cells. Moreover, CD19-CAR-NK cells significantly blocked Nalm-6 tumor growth in vivo. Thus, non-viral delivery of CAR mRNA-LNPs can be used to generate functional CAR-NK cells with high anti-tumor activity.

CAR-NK Cells Generated with mRNA-LNPs Kill Tumor Target Cells In Vitro and In Vivo.

The human epidermal growth factor receptor 2 (HER2) is a transmembrane tyrosine kinase receptor and tumor-associated antigen abnormally expressed in various types of cancer, including breast, ovarian, and gastric cancer. HER2 overexpression is highly correlated with increased tumor aggressiveness, poorer prognosis, and shorter overall survival. Consequently, multiple HER2-targeted therapies have been developed and approved; however, only a subset of patients benefit from these treatments, and relapses are common. More potent and durable HER2-targeted therapies are desperately needed for patients with HER2-positive cancers. In this study, we developed a lipid nanoparticle (LNP)-based therapy formulated with mRNA encoding a novel HER2-CD3-Fc bispecific antibody (bsAb) for HER2-positive cancers. The LNPs efficiently transfected various types of cells, such as HEK293S, SKOV-3, and A1847, leading to robust and sustained secretion of the HER2-CD3-Fc bsAb with high binding affinity to both HER2 and CD3. The bsAb induced potent T-cell-directed cytotoxicity, along with secretion of IFN-λ, TNF-α, and granzyme B, against various types of HER2-positive tumor cells in vitro, including A549, NCI-H460, SKOV-3, A1847, SKBR3, and MDA-MB-231. The bsAb-mediated antitumor effect is highly specific and strictly dependent on its binding to HER2, as evidenced by the gained resistance of A549 and A1847  knockout cells and the acquired sensitivity of mouse 4T1 cells overexpressing the human HER2 extracellular domain (ECD) or epitope-containing subdomain IV to the bsAb-induced T cell cytotoxicity. The bsAb also relies on its binding to CD3 for T-cell recruitment, as ablation of CD3 binding abolished the bsAb's ability to elicit antitumor activity. Importantly, intratumoral injection of the HER2-CD3-Fc mRNA-LNPs triggers a strong antitumor response and completely blocks HER2-positive tumor growth in a mouse xenograft model of human ovarian cancer. These results indicate that the novel HER2-CD3-Fc mRNA-LNP-based therapy has the potential to effectively treat HER2-positive cancer.

Article	Year
FLAG-tagged CD19-specific CAR-T cells eliminate CD19-bearing solid tumor cells and . Frontiers in bioscience (Landmark edition)\| PubMed ID: 28410137	2017
CD47-CAR-T Cells Effectively Kill Target Cancer Cells and Block Pancreatic Tumor Growth. Cancers\| PubMed ID: 29065481	2017
GITR domain inside CAR co-stimulates activity of CAR-T cells against cancer. Frontiers in bioscience (Landmark edition)\| PubMed ID: 29772559	2018
CAR-T Cells Based on Novel BCMA Monoclonal Antibody Block Multiple Myeloma Cell Growth. Cancers\| PubMed ID: 30208593	2018
Generation of CAR-T Cells for Cancer Immunotherapy. Methods in molecular biology (Clifton, N.J.)\| PubMed ID: 30465215	2019
Hypoxia Selectively Impairs CAR-T Cells In Vitro. Cancers\| PubMed ID: 31052261	2019
Transferrin epitope-CD19-CAR-T cells effectively kill lymphoma cells and . Frontiers in bioscience (Landmark edition)\| PubMed ID: 31585889	2020
DCLK1 Monoclonal Antibody-Based CAR-T Cells as a Novel Treatment Strategy against Human Colorectal Cancers. Cancers\| PubMed ID: 31878090	2019
PLAP -CAR T cells mediate high specific cytotoxicity against colon cancer cells. Frontiers in bioscience (Landmark edition)\| PubMed ID: 32472757	2020
Novel CD37, Humanized CD37 and Bi-Specific Humanized CD37-CD19 CAR-T Cells Specifically Target Lymphoma. Cancers\| PubMed ID: 33652767	2021
Novel CS1 CAR-T Cells and Bispecific CS1-BCMA CAR-T Cells Effectively Target Multiple Myeloma. Biomedicines\| PubMed ID: 34680541	2021
mRNA-Lipid Nanoparticle (LNP) Delivery of Humanized EpCAM-CD3 Bispecific Antibody Significantly Blocks Colorectal Cancer Tumor Growth. Cancers\| PubMed ID: 37345198	2023
CAR-NK Cells Generated with mRNA-LNPs Kill Tumor Target Cells In Vitro and In Vivo. International journal of molecular sciences\| PubMed ID: 37686170	2023
HER2-CD3-Fc Bispecific Antibody-Encoding mRNA Delivered by Lipid Nanoparticles Suppresses HER2-Positive Tumor Growth. Vaccines\| PubMed ID: 39066446	2024

Hua Zhou

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