Cryopreserved NK cells in the treatment of haematological malignancies: preclinical study

Cryopreservation of Immune Cells: Recent Progress and Challenges Ahead

Cryopreservation of immune cells is considered as a key enabling technology for adoptive cellular immunotherapy. However, current immune cell cryopreservation technologies face the challenges with poor biocompatibility of cryoprotection materials, low efficiency, and impaired post-thaw function, limiting their clinical translation. This review briefly introduces the adoptive cellular immunotherapy and the approved immune cell-based products, which involve T cells, natural killer cells and etc. The cryodamage mechanisms to these immune cells during cryopreservation process are described, including ice formation related mechanical and osmotic injuries, cryoprotectant induced toxic injuries, and other biochemical injuries. Meanwhile, the recent advances in the cryopreservation medium and freeze-thaw protocol for several representative immune cell type are summarized. Furthermore, the remaining challenges regarding on the cryoprotection materials, freeze-thaw protocol, and post-thaw functionality evaluation of current cryopreservation technologies are discussed. Finally, the future perspectives are proposed toward advancing highly efficient cryopreservation of immune cells.

Optimizing the cryopreservation and post-thaw recovery of natural killer cells is critical for the success of off-the-shelf platforms

Natural killer (NK) cells are a promising allogeneic, off-the-shelf, cellular immunotherapy product. These cells can be manipulated ex vivo, genetically edited to enhance tumor targeting and expanded to produce large cell banks for multiple patient infusions. Therapeutic efficacy of these products depends on the recovery of viable and functional cells post-thaw. Post-thaw loss of viability and cytolytic activity results in large, and often variable, discrepancies between the intended cell dose (based on counts at cryopreservation) and the actual dose administered. Compared to their highly activated state in fresh culture, post-thaw NK cells demonstrate critical changes in cytokine production, cytotoxic activity, in vivo proliferation and migration. When these NK cells are introduced into the highly immunosuppressive tumor microenvironment, the functional changes induced by cryopreservation further limits the clinical potential of these products. This report will review the impact of cryopreservation on ex vivo expanded NK cells and outlines strategies described in published studies to recover post-thaw function.

Knockout of the inhibitory receptor TIGIT enhances the antitumor response of ex vivo expanded NK cells and prevents fratricide with therapeutic Fc-active TIGIT antibodies

BACKGROUND

Inhibitory receptor T-cell Immunoreceptor with Ig and ITIM domains (TIGIT) expressed by Natural Killer (NK) and T cells regulates cancer immunity and has been touted as the next frontier in the development of cancer immunotherapeutics. Although early results of anti-TIGIT and its combinations with antiprogrammed death-ligand 1 were highly exciting, results from an interim analysis of phase III trials are disappointing. With mixed results, there is a need to understand the effects of therapeutic anti-TIGIT on the TIGIT+ immune cells to support its clinical use. Most of the TIGIT antibodies in development have an Fc-active domain, which binds to Fc receptors on effector cells. In mouse models, Fc-active anti-TIGIT induced superior immunity, while Fc receptor engagement was required for its efficacy. NK-cell depletion compromised the antitumor immunity of anti-TIGIT indicating the essential role of NK cells in the efficacy of anti-TIGIT. Since NK cells express TIGIT and Fc-receptor CD16, Fc-active anti-TIGIT may deplete NK cells via fratricide, which has not been studied.

METHODS

CRISPR-Cas9-based TIGIT knockout (KO) was performed in expanded NK cells. Phenotypic and transcriptomic properties of TIGIT KO and wild-type (WT) NK cells were compared with flow cytometry, CyTOF, and RNA sequencing. The effect of TIGIT KO on NK-cell cytotoxicity was determined by calcein-AM release and live cell imaging-based cytotoxicity assays. The metabolic properties of TIGIT KO and WT NK cells were compared with a Seahorse analyzer. The effect of the Fc-component of anti-TIGIT on NK-cell fratricide was determined by co-culturing WT and TIGIT KO NK cells with Fc-active and Fc-inactive anti-TIGIT.

RESULTS

TIGIT KO increased the cytotoxicity of NK cells against multiple cancer cell lines including spheroids. TIGIT KO NK cells upregulated mTOR complex 1 (mTORC1) signaling and had better metabolic fitness with an increased basal glycolytic rate when co-cultured with cancer cells compared with WT NK cells. Importantly, TIGIT KO prevented NK-cell fratricide when combined with Fc-active anti-TIGIT.

CONCLUSIONS

TIGIT KO in ex vivo expanded NK cells increased their cytotoxicity and metabolic fitness and prevented NK-cell fratricide when combined with Fc-active anti-TIGIT antibodies. These fratricide-resistant TIGIT KO NK cells have therapeutic potential alone or in combination with Fc-active anti-TIGIT antibodies to enhance their efficacy.

TIGIT Expression on Activated NK Cells Correlates with Greater Anti-Tumor Activity but Promotes Functional Decline upon Lung Cancer Exposure: Implications for Adoptive Cell Therapy and TIGIT-Targeted Therapies

Treatments targeting TIGIT have gained a lot of attention due to strong preclinical and early clinical results, particularly with anti-PD-(L)1 therapeutics. However, this combination has failed to meet progression-free survival endpoints in phase III trials. Most of our understanding of TIGIT comes from studies of T cell function. Yet, this inhibitory receptor is often upregulated to the same, or higher, extent on NK cells in cancers. Studies in murine models have demonstrated that TIGIT inhibits NK cells and promotes exhaustion, with its effects on tumor control also being dependent on NK cells. However, there are limited studies assessing the role of TIGIT on the function of human NK cells (hNK), particularly in lung cancer. Most studies used NK cell lines or tested TIGIT blockade to reactivate exhausted cells obtained from cancer patients. For therapeutic advancement, a better understanding of TIGIT in the context of activated hNK cells is crucial, which is different than exhausted NK cells, and critical in the context of adoptive NK cell therapeutics that may be combined with TIGIT blockade. In this study, the effect of TIGIT blockade on the anti-tumor activities of human ex vivo-expanded NK cells was evaluated in vitro in the context of lung cancer. TIGIT expression was higher on activated and/or expanded NK cells compared to resting NK cells. More TIGIT+ NK cells expressed major activating receptors and exerted anti-tumor response as compared to TIGIT- cells, indicating that NK cells with greater anti-tumor function express more TIGIT. However, long-term TIGIT engagement upon exposure to PVR+ tumors downregulated the cytotoxic function of expanded NK cells while the inclusion of TIGIT blockade increased cytotoxicity, restored the effector functions against PVR-positive targets, and upregulated immune inflammation-related gene sets. These combined results indicate that TIGIT blockade can preserve the activation state of NK cells during exposure to PVR+ tumors. These results support the notion that a functional NK cell compartment is critical for anti-tumor response and anti-TIGIT/adoptive NK cell combinations have the potential to improve outcomes.

Cryopreserved PM21-Particle-Expanded Natural Killer Cells Maintain Cytotoxicity and Effector Functions In Vitro and In Vivo

There is a great interest in developing natural killer (NK) cells as adoptive cancer immunotherapy. For off-the-shelf approaches and to conduct multicenter clinical trials, cryopreserved NK cells are the preferred product. However, recent studies reported that cryopreservation of NK cells results in loss of cell motility and, as a consequence, cytotoxicity which limits the clinical utility of such products. This study assessed the impact of cryopreservation on the recovery and function of PM21-particle expanded NK cells (PM21-NK cells) as well as their antitumor activity in vitro using 2D and 3D cancer models and in vivo in ovarian cancer models, including patient-derived xenografts (PDX). Viable PM21-NK cells were consistently recovered from cryopreservation and overnight rest with a mean recovery of 73 ± 22% (N = 19). Thawed and rested NK cells maintained the expression of activating receptors when compared to expansion-matched fresh NK cells. Cryopreserved NK cells that were thawed and rested showed no decrease in cytotoxicity when co-incubated with tumor cells at varying effector-to-target (NK:T) ratios compared to expansion-matched fresh NK cells. Moreover, no differences in cytotoxicity were observed between expansion-matched cryopreserved and fresh NK cells in 3D models of tumor killing. These were analyzed by kinetic, live-cell imaging assays co-incubating NK cells with tumor spheroids. When exposed to tumor cells, or upon cytokine stimulation, cryopreserved NK cells that were thawed and rested showed no significant differences in surface expression of degranulation marker CD107a or intracellular expression of TNFα and IFNγ. In vivo antitumor activity was also assessed by measuring the extension of survival of SKOV-3-bearing NSG mice treated with fresh vs. cryopreserved NK cells. Cryopreserved NK cells caused a statistically significant survival extension of SKOV-3-bearing NSG mice that was comparable to that observed with fresh NK cells. Additionally, treatment of NSG mice bearing PDX tumor with cryopreserved PM21-NK cells resulted in nearly doubling of survival compared to untreated mice. These data suggest that PM21-NK cells can be cryopreserved and recovered efficiently without appreciable loss of viability or activity while retaining effector function both in vitro and in vivo. These findings support the use of cryopreserved PM21-NK cells as a cancer immunotherapy treatment.

Ex vivo expanded allogeneic natural killer cells have potent cytolytic activity against cancer cells through different receptor-ligand interactions

Background

Recently, allogeneic natural killer (NK) cells have gained considerable attention as promising immunotherapeutic tools due to their unique biological functions and characteristics. Although many NK expansion strategies have been reported previously, a deeper understanding of cryopreserved allogeneic NK cells is needed for specific therapeutic approaches.

Methods

We isolated CD3⁻CD56⁺ primary natural killer (pNK) cells from healthy donors and expanded them ex vivo using a GMP-compliant method without any feeder to generate large volumes of therapeutic pNK cells and cryopreserved stocks. After validation for high purity and activating phenotypes, we performed RNA sequencing of the expanded and cryopreserved pNK cells. The pNK cells were used against various cancer cell lines in 7-AAD/CFSE cytotoxicity assay. For in vivo efficacy study, NSG mice bearing subcutaneous cisplatin-resistant A2780cis xenografts were treated with our pNK cells or cisplatin. Antitumor efficacy was assessed by measuring tumor volume and weight.

Results

Compared to the pNK cells before expansion, pNK cells after expansion showed 2855 upregulated genes, including genes related to NK cell activation, cytotoxicity, chemokines, anti-apoptosis, and proliferation. Additionally, the pNK cells showed potent cytolytic activity against various cancer cell lines. Interestingly, our activated pNK cells showed a marked increase in NKp44 (1064-fold), CD40L (12,018-fold), and CCR5 (49-fold), and did not express the programmed cell death protein 1(PD-1). We also demonstrated the in vitro and in vivo efficacies of pNK cells against cisplatin-resistant A2780cis ovarian cancer cells having a high programmed death-ligand 1(PD-L1) and low HLA-C expression.

Conclusions

Taken together, our study provides the first comprehensive genome wide analysis of ex vivo-expanded cryopreserved pNK cells. It also indicates the potential use of expanded and cryopreserved pNK cells as a highly promising immunotherapy for anti-cancer drug resistant patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02089-0.

Cryopreservation of NK and T Cells Without DMSO for Adoptive Cell-Based Immunotherapy

Dimethylsufoxide (DMSO) being universally used as a cryoprotectant in clinical adoptive cell-therapy settings to treat hematological malignancies and solid tumors is a growing concern, largely due to its broad toxicities. Its use has been associated with significant clinical side effects-cardiovascular, neurological, gastrointestinal, and allergic-in patients receiving infusions of cell-therapy products. DMSO has also been associated with altered expression of natural killer (NK) and T-cell markers and their in vivo function, not to mention difficulties in scaling up DMSO-based cryoprotectants, which introduce manufacturing challenges for autologous and allogeneic cellular therapies, including chimeric antigen receptor (CAR)-T and CAR-NK cell therapies. Interest in developing alternatives to DMSO has resulted in the evaluation of a variety of sugars, proteins, polymers, amino acids, and other small molecules and osmolytes as well as modalities to efficiently enable cellular uptake of these cryoprotectants. However, the DMSO-free cryopreservation of NK and T cells remains difficult. They represent heterogeneous cell populations that are sensitive to freezing and thawing. As a result, clinical use of cryopreserved cell-therapy products has not moved past the use of DMSO. Here, we present the state of the art in the development and use of cryopreservation options that do not contain DMSO toward clinical solutions to enable the global deployment of safer adoptively transferred cell-based therapies.

MAGT1 messenger RNA-corrected autologous T and natural killer cells for potential cell therapy in X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia disease

BACKGROUND AIM

X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect' (XMEN) disease is caused by mutations in the magnesium transporter 1 (MAGT1) gene. Loss of MAGT1 function results in a glycosylation defect that abrogates expression of key immune proteins such as the NKG2D receptor on CD8⁺ T and NK cells, which is critical for the recognition and killing of virus-infected and transformed cells, a biomarker for MAGT1 function. Patients with XMEN disease frequently have increased susceptibility to EBV infections and EBV-associated B cell malignancies, for which no specific treatment options are currently available. Experimental transfer of donor EBV-specific cytotoxic T cells may be beneficial but carries the risks of eliciting alloimmune responses. An approach for cell therapy to address viral infections and associated complications that avoids the risks of alloimmunity is needed.

METHODS

Here the authors assess the feasibility and efficiency of correcting autologous lymphocytes from XMEN patients by MAGT1 mRNA electroporation (EP) that avoids genomic integration and can be scaled for clinical application.

RESULTS AND CONCLUSIONS

Restoration of NKG2D expression was demonstrated in XMEN patient lymphocytes after MAGT1 mRNA electroporation that reach healthy donor levels in CD8⁺ T and NK cells at 1-2 days after EP. NKG2D expression persisted at ∼50% for 2 weeks after EP. Functionally, mRNA-correction of XMEN NK cells rescued cytotoxic activity also to healthy donor NK cell level. The restored NKG2D receptor expression and function were unaffected by cryopreservation, which will make feasible repeat infusions of MAGT1 mRNA-corrected autologous XMEN CD8⁺ T and NK cells for potential short term therapy for XMEN patients without the risks of alloimmunization.

Analysis of ex vivo expanded and activated clinical-grade human NK cells after cryopreservation

BACKGROUND AIMS

Several methods to expand and activate (EA) NK cells ex vivo have been developed for the treatment of relapsed or refractory cancers. Infusion of fresh NK cells is generally preferred to the infusion of cryopreserved/thawed (C/T) NK cells because of concern that cryopreservation diminishes NK cell activity. However, there has been little head-to-head comparison of the functionality of fresh versus C/T NK cell products.

METHODS

We evaluated activity of fresh and C/T EA NK cells generated by interleukin (IL)-15, IL-2 and CD137L expansion.

RESULTS

Analysis of C/T NK cell products demonstrated decreased recovery of viable CD56⁺ cells, but the proportion of NK cells in the C/T EA NK cell product did not decrease compared with the fresh EA NK cell product. Fresh and C/T EA NK cells demonstrated increased granzyme B compared with NK cells pre-expansion, but only fresh EA NK cells showed increased NKG2D. Compared with fresh EA NK cells, cytotoxic ability of C/T EA NK cells was reduced, but C/T EA NK cells remained potently cytotoxic against tumor cells via both antibody-independent and antibody-dependent mechanisms within 4 h post-thaw. Fresh EA NK cells generated high levels of gamma interferon (IFN-γ), which was abrogated by JAK1/JAK2 inhibition with ruxolitinib, but C/T EA NK cells showed lower IFN-γ unaffected by JAK1/JAK2 inhibition.

DISCUSSION

Usage of C/T EA NK cells may be an option to provide serial "boost" NK cell infusions from a single apheresis to maximize NK cell persistence and potentially improve NK-induced responses to refractory cancer.

Nanoparticle-Mediated Intracellular Protection of Natural Killer Cells Avoids Cryoinjury and Retains Potent Antitumor Functions

The ability of natural killer (NK) cells to mediate potent antitumor immunity in clinical adoptive transfer settings relies, in large part, on their ability to retain cytotoxic function following cryopreservation. To avoid potential systemic toxicities associated with infusions of NK cells into patients in the presence of dimethylsulfoxide (DMSO), interest in alternative cryoprotective agents (CPAs) with improved safety profiles has grown. Despite the development of various sugars, amino acids, polyols, and polyampholytes as cryoprotectants, their ability to promote protection from intracellular cryodamage is limited because they mostly act outside of the cell. Though ways to shuttle cryoprotectants intracellularly exist, NK cells' high aversity to manipulation and freezing has meant they are highly understudied as targets for the development of new cryopreservation approaches. Here, the first example of a safe and efficient platform for the intracellular delivery of non-DMSO CPAs to NK cells is presented. Biocompatible chitosan-based nanoparticles are engineered to mediate the efficient DMSO-free cryopreservation of NK cells. NK cells cryopreserved in this way retain potent cytotoxic, degranulation, and cytokine production functions against tumor targets. This not only represents the first example of delivering nanoparticles to NK cells, but illustrates the clinical potential in manufacturing safer allogeneic adoptive immunotherapies "off the shelf."

Improving the Clinical Application of Natural Killer Cells by Modulating Signals Signal from Target Cells

Relapsed acute myeloid leukemia (AML) is a significant post-transplant complication lacking standard treatment and associated with a poor prognosis. Cellular therapy, which is already widely used as a treatment for several hematological malignancies, could be a potential treatment alternative. Natural killer (NK) cells play an important role in relapse control but can be inhibited by the leukemia cells highly positive for HLA class I. In order to restore NK cell activity after their ex vivo activation, NK cells can be combined with conditioning target cells. In this study, we tested NK cell activity against KG1a (AML cell line) with and without two types of pretreatment—Ara-C treatment that induced NKG2D ligands (increased activating signal) and/or blocking of HLA–KIR (killer-immunoglobulin-like receptors) interaction (decreased inhibitory signal). Both treatments improved NK cell killing activity. Compared with target cell killing of NK cells alone (38%), co-culture with Ara-C treated KG1a target cells increased the killing to 80%. Anti-HLA blocking antibody treatment increased the proportion of dead KG1a cells to 53%. Interestingly, the use of the combination treatment improved the killing potential to led to the death of 85% of KG1a cells. The combination of Ara-C and ex vivo activation of NK cells has the potential to be a feasible approach to treat relapsed AML after hematopoietic stem cell transplantation.

How do I structure logistic processes in preparation for outsourcing of cellular therapy manufacturing?

As cell and gene therapies (CGT) assume center stage in early-phase clinical trials for several acute and chronic diseases, there is heightened interest in the standardization and automation of manufacturing processes in preparation for commercialization. Toward this goal, a hybrid and oftentimes geographically separated model comprising regional cell procurement and infusion facilities and a centralized cell manufacturing unit is gaining traction in the field. Although CGT processing facilities in academic institutions are not involved directly in the manufacturing of these therapies, they must be prepared to collaborate with commercial or contract manufacturing organizations (CMOs) and be ready to address several supply-chain challenges that have emerged for autologous and allogeneic CGT. Academic center cell-processing facilities must handle many events up- and downstream of manufacturing such as donor screening, cell collection, product labeling, cryopreservation, transportation, and thaw infusion. These events merit closer evaluation in the context of multifacility manufacturing since standard procedures have yet to be established. Based on our institutional experience, we summarize logistical challenges encountered in the handling and distribution of CGT products in early phase studies, specifically those involving CMO (outsourced) manufacturing. We also make recommendations to standardize processes unique to the CGT supply chain, emphasizing the need to maintain needle-to-needle traceability from product collection to infusion. These guidelines will inform the development of more complex supply-chain models for larger-scale cell and gene therapeutics.

Bioinspired Preservation of Natural Killer Cells for Cancer Immunotherapy

The ability to cryopreserve natural killer (NK) cells has a significant potential in modern cancer immunotherapy. Current cryopreservation protocols cause deterioration in NK cell viability and functionality. This work reports the preservation of human cytokine-activated NK cell viability and function following cryopreservation using a cocktail of biocompatible bioinspired cryoprotectants (i.e., dextran and carboxylated ε-poly-L-lysine). Results demonstrate that the recovered NK cells after cryopreservation and rewarming maintain their viability immediately after thawing at a comparable level to control (dimethyl sulfoxide-based cryopreservation). Although, their viability drops in the first day in culture compared to controls, the cells grow back to a comparable level to controls after 1 week in culture. In addition, the anti-tumor functional activity of recovered NK cells demonstrates higher cytotoxic potency against leukemia cells compared to control. This approach presents a new direction for NK cell preservation, focusing on function and potentially enabling storage and distribution for cancer immunotherapy.

Recurrent Stimulation of Natural Killer Cell Clones with K562 Expressing Membrane-Bound Interleukin-21 Affects Their Phenotype, Interferon-γ Production, and Lifespan

A pattern of natural killer cell (NK cell) heterogeneity determines proliferative and functional responses to activating stimuli in individuals. Obtaining the progeny of a single cell by cloning the original population is one of the ways to study NK cell heterogeneity. In this work, we sorted single cells into a plate and stimulated them via interleukin (IL)-2 and gene-modified K562 feeder cells that expressed membrane-bound IL-21 (K562-mbIL21), which led to a generation of phenotypically confirmed and functionally active NK cell clones. Next, we applied two models of clone cultivation, which differently affected their phenotype, lifespan, and functional activity. The first model, which included weekly restimulation of clones with K562-mbIL21 and IL-2, resulted in the generation of relatively short-lived (5⁻7 weeks) clones of highly activated NK cells. Levels of human leukocyte antigen class II molecule-DR isotype (HLA-DR) expression in the expanded NK cells correlated strongly with interferon-γ (IFN-γ) production. The second model, in which NK cells were restimulated weekly with IL-2 alone and once on the sixth week with K562-mbIL21 and IL-2, produced long-lived clones (8⁻14 weeks) that expanded up to 10⁷ cells with a lower ability to produce IFN-γ. Our method is applicable for studying variability in phenotype, proliferative, and functional activity of certain NK cell progeny in response to the stimulation, which may help in selecting NK cells best suited for clinical use.

Optimization of Large-Scale Expansion and Cryopreservation of Human Natural Killer Cells for Anti-Tumor Therapy

Allogeneic natural killer (NK) cell therapy is a potential therapeutic approach for a variety of solid tumors. We established an expansion method for large-scale production of highly purified and functionally active NK cells, as well as a freezing medium for the expanded NK cells. In the present study, we assessed the effect of cryopreservation on the expanded NK cells in regards to viability, phenotype, and anti-tumor activity. NK cells were enormously expanded (about 15,000-fold expansion) with high viability and purity by stimulating CD3⁺ T cell-depleted peripheral blood mononuclear cells (PBMCs) with irradiated autologous PBMCs in the presence of IL-2 and OKT3 for 3 weeks. Cell viability was slightly reduced after freezing and thawing, but cytotoxicity and cytokine secretion were not significantly different. In a xenograft mouse model of hepatocellular carcinoma cells, cryopreserved NK cells had slightly lower anti-tumor efficacy than freshly expanded NK cells, but this was overcome by a 2-fold increased dose of cryopreserved NK cells. In vivo antibody-dependent cell cytotoxicity (ADCC) activity of cryopreserved NK cells was also demonstrated in a SCID mouse model injected with Raji cells with rituximab co-administration. Therefore, we demonstrated that expanded/frozen NK cells maintain viability, phenotype, and anti-tumor activity immediately after thawing, indicating that expanded/frozen NK cells can provide ‘ready-to-use’ cell therapy for cancer patients.

Natural killer cells as a therapeutic tool for infectious diseases - current status and future perspectives

Natural Killer (NK) cells are involved in the host immune response against infections due to viral, bacterial and fungal pathogens, all of which are a significant cause of morbidity and mortality in immunocompromised patients. Since the recovery of the immune system has a major impact on the outcome of an infectious complication, there is major interest in strengthening the host response in immunocompromised patients, either by using cytokines or growth factors or by adoptive cellular therapies transfusing immune cells such as granulocytes or pathogen-specific T-cells. To date, relatively little is known about the potential of adoptively transferring NK cells in immunocompromised patients with infectious complications, although the anti-cancer property of NK cells is already being investigated in the clinical setting. This review will focus on the antimicrobial properties of NK cells and the current standing and future perspectives of generating and using NK cells as immunotherapy in patients with infectious complications, an approach which is promising and might have an important clinical impact in the future.

Synergistic Effects of Cabozantinib and EGFR-Specific CAR-NK-92 Cells in Renal Cell Carcinoma

The chimeric antigen receptor-modified immune effector cell (CAR-T and CAR-NK) therapies are newly developed adoptive treatments of cancers. However, their therapeutic efficacy against solid tumors is limited. Combining CAR-T or CAR-NK cells with chemotherapeutic drugs to treat solid tumor may be a promising strategy. We developed an epidermal growth factor- (EGFR-) specific third-generation CAR. NK-92 cells were modified with the CAR by lentivirus infection. The specific killing ability of the CAR-modified NK-92 cells (CAR-NK-92) against renal cell carcinoma (RCC) cell lines was confirmed in vitro. The synergistic effects of cabozantinib and EGFR-specific CAR-NK-92 cells were investigated in vitro and in vivo. Our results showed that the CAR-NK-92 cells lyse RCC cells in an EGFR-specific manner. Treatment with cabozantinib could increase EGFR and decrease PD-L1 membrane surface expression in RCC cells and enhance the killing ability of CAR-NK-92 cells against the RCC cells in vitro. Furthermore, the CAR-NK-92 cells show synergistic therapeutic efficacy with cabozantinib against human RCC xenograft models. Our results provided the basis for combination with chemotherapy as a novel strategy for enhancing the therapeutic efficacy of CAR-modified immune effector cells for solid tumors.