Combination of tucatinib and neural stem cells secreting anti-HER2 antibody prolongs survival of mice with metastatic brain cancer.

Brain metastases are a leading cause of death in patients with breast cancer. The lack of clinical trials and the presence of the blood-brain barrier limit therapeutic options. Furthermore, overexpression of the human epidermal growth factor receptor 2 (HER2) increases the incidence of breast cancer brain metastases (BCBM). HER2-targeting agents, such as the monoclonal antibodies trastuzumab and pertuzumab, improved outcomes in patients with breast cancer and extracranial metastases. However, continued BCBM progression in breast cancer patients highlighted the need for novel and effective targeted therapies against intracranial metastases. In this study, we engineered the highly migratory and brain tumor tropic human neural stem cells (NSCs) LM008 to continuously secrete high amounts of functional, stable, full-length antibodies against HER2 (anti-HER2Ab) without compromising the stemness of LM008 cells. The secreted anti-HER2Ab impaired tumor cell proliferation in vitro in HER2+ BCBM cells by inhibiting the PI3K-Akt signaling pathway and resulted in a significant benefit when injected in intracranial xenograft models. In addition, dual HER2 blockade using anti-HER2Ab LM008 NSCs and the tyrosine kinase inhibitor tucatinib significantly improved the survival of mice in a clinically relevant model of multiple HER2+ BCBM. These findings provide compelling evidence for the use of HER2Ab-secreting LM008 NSCs in combination with tucatinib as a promising therapeutic regimen for patients with HER2+ BCBM.

Early Stage Professionals Committee proceedings from the International Society for Cell & Gene Therapy 2022 Annual Meeting.

In this Committee Proceedings, representatives from the Early Stage Professional (ESP) committee highlight the innovative discoveries and key take-aways from oral presentations at the 2022 International Society for Cell and Gene Therapy (ISCT) Annual Meeting that cover the following subject categories: Immunotherapy, Exosomes and Extracellular Vesicles, HSC/Progenitor Cells and Engineering, Mesenchymal Stromal Cells, and ISCT Late-Breaking Abstracts.

Medulloblastoma rendered susceptible to NK-cell attack by TGFß neutralization.

BACKGROUND: Medulloblastoma (MB), the most common pediatric brain cancer, presents with a poor prognosis in a subset of patients with high risk disease, or at recurrence, where current therapies are ineffective. Cord blood (CB) natural killer (NK) cells may be promising off-the-shelf effector cells for immunotherapy due to their recognition of malignant cells without the need for a known target, ready availability from multiple banks, and their potential to expand exponentially. However, they are currently limited by immune suppressive cytokines secreted in the MB tumor microenvironment including Transforming Growth Factor ß (TGF-ß). Here, we address this challenge in in vitro models of MB. METHODS: CB-derived NK cells were modified to express a dominant negative TGF-ß receptor II (DNRII) using retroviral transduction. The ability of transduced CB cells to maintain function in the presence of medulloblastoma-conditioned media was then assessed. RESULTS: We observed that the cytotoxic ability of nontransduced CB-NK cells was reduced in the presence of TGF-ß-rich, medulloblastoma-conditioned media (21.21 ± 1.19% killing at E:T 5:1 in the absence vs. 14.98 ± 2.11% in the presence of medulloblastoma-conditioned media, n = 8, p = 0.02), but was unaffected in CB-derived DNRII-transduced NK cells (21.11 ± 1.84% killing at E:T 5:1 in the absence vs. 21.81 ± 3.37 in the presence of medulloblastoma-conditioned media, n = 8, p = 0.85. We also observed decreased expression of CCR2 in untransduced NK cells (mean CCR2 MFI 826 ± 117 in untransduced NK + MB supernatant from mean CCR2 MFI 1639.29 ± 215 in no MB supernatant, n = 7, p = 0.0156), but not in the transduced cells. Finally, we observed that CB-derived DNRII-transduced NK cells may protect surrounding immune cells by providing a cytokine sink for TGF-ß (decreased TGF-ß levels of 610 ± 265 pg/mL in CB-derived DNRII-transduced NK cells vs. 1817 ± 342 pg/mL in untransduced cells; p = 0.008). CONCLUSIONS: CB NK cells expressing a TGF-ß DNRII may have a functional advantage over unmodified NK cells in the presence of TGF-ß-rich MB, warranting further investigation on its potential applications for patients with medulloblastoma.

Designing Magnetically Responsive Biohybrids Composed of Cord Blood-Derived Natural Killer Cells and Iron Oxide Nanoparticles.

We report the generation of magnetically responsive, cord blood-derived natural killer (NK) cells using iron oxide nanoparticles (IONPs). NK cells are a promising immune cell population for cancer cell therapy as they can target and lyse target tumor cells without prior education. However, NK cells cannot home to disease sites based on antigen recognition, instead relying primarily on external stimuli and chemotactic gradients for transport. Hence, we hypothesized that conjugating IONPs onto the surface of NK cells provides an added feature of magnetic homing to the NK cells, improving their therapeutic function. We describe a robust design for conjugating the IONPs onto the surface of NK cells, which maintains their intrinsic phenotype and function. The conferred magnetic-responsiveness is utilized to improve the cytolytic function of the NK cells for target cells in 2D and 3D models. These findings demonstrate the feasibility of improving NK cell homing and therapeutic efficacy with our NK:IONP "biohybrid".

Cord blood natural killer cells expressing a dominant negative TGF-ß receptor: Implications for adoptive immunotherapy for glioblastoma.

Cord blood (CB) natural killer (NK) cells are promising effector cells for tumor immunotherapy but are currently limited by immune-suppressive cytokines in the tumor microenvironment, such as transforming growth factor (TGF-ß). We observed that TGF-ß inhibits expression of activating receptors such as NKG2D and DNAM1 and decreases killing activity against glioblastoma tumor cells through inhibition of perforin secretion. To overcome the detrimental effects of TGF-ß, we engrafted a dominant negative TGF-ß receptor II (DNRII) on CB-derived NK cells by retroviral transduction and evaluated their ability to kill glioblastoma cells in the presence of TGF-ß. After manufacture using Good Manufacturing Practice-compliant methodologies and transduction with DNRII, CB-derived DNRII-transduced NK cells expanded to clinically relevant numbers and retained both their killing ability and their secretion of interferon-γ upon activation. More important, these cells maintained both perforin expression and NKG2D/DNMA1 expression in the presence of TGF-ß allowing for recognition and killing of glioblastoma tumor cells. Hence, NK cells expressing a DNRII should have a functional advantage over unmodified NK cells in the presence of TGF-ß-secreting tumors and may be an important therapeutic approach for patients with cancer.

Prussian blue nanoparticle-based photothermal therapy combined with checkpoint inhibition for photothermal immunotherapy of neuroblastoma.

We describe "photothermal immunotherapy," which combines Prussian blue nanoparticle (PBNP)-based photothermal therapy (PTT) with anti-CTLA-4 checkpoint inhibition for treating neuroblastoma, a common, hard-to-treat pediatric cancer. PBNPs exhibit pH-dependent stability, which makes them suitable for intratumorally-administered PTT. PBNP-based PTT is able to lower tumor burden and prime an immune response, specifically an increased infiltration of lymphocytes and T cells to the tumor area, which is complemented by the antitumor effects of anti-CTLA-4 immunotherapy, providing a more durable treatment against neuroblastoma in an animal model. We observe 55.5% survival in photothermal immunotherapy-treated mice at 100days compared to 12.5%, 0%, 0%, and 0% survival in mice receiving: anti-CTLA-4 alone, PBNPs alone, PTT alone, and no treatment, respectively. Additionally, long-term surviving, photothermal immunotherapy-treated mice exhibit protection against neuroblastoma rechallenge, suggesting the development of immunity against these tumors. Our findings suggest the potential of photothermal immunotherapy in improving treatments for neuroblastoma.

Improving efficacy of cancer immunotherapy by genetic modification of natural killer cells.

Natural killer (NK) cells are members of the innate immune system that recognize target cells via activating and inhibitory signals received through cell receptors. Derived from the lymphoid lineage, NK cells are able to produce cytokines and exert a cytotoxic effect on viral infected and malignant cells. It is their unique ability to lyse target cells rapidly and without prior education that renders NK cells a promising effector cell for adoptive cell therapy. However, both viruses and tumors employ evasion strategies to avoid attack by NK cells, which represent biological challenges that need to be harnessed to fully exploit the cytolytic potential of NK cells. Using genetic modification, the function of NK cells can be enhanced to improve their homing, cytolytic activity, in vivo persistence and safety. Examples include gene modification to express chemokine, high-affinity Fc receptor and chimeric antigen receptors, suicide genes and the forced expression of cytokines such as interleukin (IL)-2 and IL-15. Preclinical studies have clearly demonstrated that such approaches are effective in improving NK-cell function, homing and safety. In this review, we summarize the recent advances in the genetic manipulations of NK cells and their application for cellular immunotherapeutic strategies.

Liver myeloid-derived suppressor cells expand in response to liver metastases in mice and inhibit the anti-tumor efficacy of anti-CEA CAR-T.

Chimeric antigen receptor-modified T cell (CAR-T) technology, a promising immunotherapeutic tool, has not been applied specifically to treat liver metastases (LM). While CAR-T delivery to LM can be optimized by regional intrahepatic infusion, we propose that liver CD11b+Gr-1+ myeloid-derived suppressor cells (L-MDSC) will inhibit the efficacy of CAR-T in the intrahepatic space. We studied anti-CEA CAR-T in a murine model of CEA+ LM and identified mechanisms through which L-MDSC expand and inhibit CAR-T function. We established CEA+ LM in mice and studied purified L-MDSC and responses to treatment with intrahepatic anti-CEA CAR-T infusions. L-MDSC expanded threefold in response to LM, and their expansion was dependent on GM-CSF, which was produced by tumor cells. L-MDSC utilized PD-L1 to suppress anti-tumor responses through engagement of PD-1 on CAR-T. GM-CSF, in cooperation with STAT3, promoted L-MDSC PD-L1 expression. CAR-T efficacy was rescued when mice received CAR-T in combination with MDSC depletion, GM-CSF neutralization to prevent MDSC expansion, or PD-L1 blockade. As L-MDSC suppressed anti-CEA CAR-T, infusion of anti-CEA CAR-T in tandem with agents targeting L-MDSC is a rational strategy for future clinical trials.

Anti-KIT designer T cells for the treatment of gastrointestinal stromal tumor.

BACKGROUND: Imatinib mesylate is an effective treatment for metastatic gastrointestinal stromal tumor (GIST). However, most patients eventually develop resistance and there are few other treatment options. Immunotherapy using genetically modified or designer T cells (dTc) has gained increased attention for several malignancies in recent years. The aims of this study were to develop and test novel anti-KIT dTc engineered to target GIST cells. METHODS: Human anti-KIT dTc were created by retroviral transduction with novel chimeric immune receptors (CIR). The gene for stem cell factor (SCF), the natural ligand for KIT, was cloned into 1st generation (SCF-CD3ζ, 1st gen) and 2nd generation (SCF-CD28-CD3ζ, 2nd gen) CIR constructs. In vitro dTc proliferation and tumoricidal capacity in the presence of KIT+ tumor cells were measured. In vivo assessment of dTc anti-tumor efficacy was performed by treating immunodeficient mice harboring subcutaneous GIST xenografts with dTc tail vein infusions. RESULTS: We successfully produced the 1st and 2nd gen anti-KIT CIR and transduced murine and human T cells. Average transduction efficiencies for human 1st and 2nd gen dTc were 50% and 42%. When co-cultured with KIT+ tumor cells, both 1st and 2nd gen dTc proliferated and produced IFNγ. Human anti-KIT dTc were efficient at lysing GIST in vitro compared to untransduced T cells. In mice with established GIST xenografts, treatment with either 1st or 2nd gen human anti-KIT dTc led to significant reductions in tumor growth rates. CONCLUSIONS: We have constructed a novel anti-KIT CIR for production of dTc that possess specific activity against KIT+ GIST in vitro and in vivo. Further studies are warranted to evaluate the therapeutic potential and safety of anti-KIT dTc.

An Engineered Prussian Blue Nanoparticles-based Nanoimmunotherapy Elicits Robust and Persistent Immunological Memory in a TH-MYCN Neuroblastoma Model.

A combination therapy using Prussian blue nanoparticles (PBNP) as photothermal therapy (PTT) agents coated with CpG oligodeoxynucleotides, an immunologic adjuvant, as a nanoimmunotherapy (CpG-PBNP-PTT) for neuroblastoma (NB) is described. NB driven by MYCN amplification confers high risk and correlates with a dismal prognosis, accounting for the majority of NB-related mortality. The efficacy of the CpG-PBNP-PTT nanoimmunotherapy in a clinically relevant, TH-MYCN murine NB model (9464D) overexpressing MYCN is tested. When administered to 9464D NB cells in vitro, CpG-PBNP-PTT triggers thermal dose-dependent immunogenic cell death and tumor cell priming for immune recognition in vitro, measured by the expression of specific costimulatory and antigen-presenting molecules. In vivo, intratumorally administered CpG-PBNP-PTT generates complete tumor regression and significantly higher long-term survival compared to controls. Furthermore, CpG-PBNP-PTT-treated mice reject tumor rechallenge. Ex vivo studies confirm these therapeutic responses result from the generation of robust T cell-mediated immunological memory. Consequently, in a synchronous 9464D tumor model, CpG-PBNP-PTT induces complete tumor regression on the treated flank and significantly slows tumor progression on the untreated flank, improving animal survival. These findings demonstrate that localized administration of the CpG-PBNP-PTT nanoimmunotherapy drives potent systemic T cell responses in solid tumors such as NB and therefore has therapeutic implications for NB.

Activation of 4-1BBL+ B cells with CD40 agonism and IFNγ elicits potent immunity against glioblastoma.

Immunotherapy has revolutionized the treatment of many tumors. However, most glioblastoma (GBM) patients have not, so far, benefited from such successes. With the goal of exploring ways to boost anti-GBM immunity, we developed a B cell-based vaccine (BVax) that consists of 4-1BBL+ B cells activated with CD40 agonism and IFNγ stimulation. BVax migrates to key secondary lymphoid organs and is proficient at antigen cross-presentation, which promotes both the survival and the functionality of CD8+ T cells. A combination of radiation, BVax, and PD-L1 blockade conferred tumor eradication in 80% of treated tumor-bearing animals. This treatment elicited immunological memory that prevented the growth of new tumors upon subsequent reinjection in cured mice. GBM patient-derived BVax was successful in activating autologous CD8+ T cells; these T cells showed a strong ability to kill autologous glioma cells. Our study provides an efficient alternative to current immunotherapeutic approaches that can be readily translated to the clinic.

Polyamines drive myeloid cell survival by buffering intracellular pH to promote immunosuppression in glioblastoma.

Glioblastoma is characterized by the robust infiltration of immunosuppressive tumor-associated myeloid cells (TAMCs). It is not fully understood how TAMCs survive in the acidic tumor microenvironment to cause immunosuppression in glioblastoma. Metabolic and RNA-seq analysis of TAMCs revealed that the arginine-ornithine-polyamine axis is up-regulated in glioblastoma TAMCs but not in tumor-infiltrating CD8+ T cells. Active de novo synthesis of highly basic polyamines within TAMCs efficiently buffered low intracellular pH to support the survival of these immunosuppressive cells in the harsh acidic environment of solid tumors. Administration of difluoromethylornithine (DFMO), a clinically approved inhibitor of polyamine generation, enhanced animal survival in immunocompetent mice by causing a tumor-specific reduction of polyamines and decreased intracellular pH in TAMCs. DFMO combination with immunotherapy or radiotherapy further enhanced animal survival. These findings indicate that polyamines are used by glioblastoma TAMCs to maintain normal intracellular pH and cell survival and thus promote immunosuppression during tumor evolution.

PLGA nanodepots co-encapsulating prostratin and anti-CD25 enhance primary natural killer cell antiviral and antitumor function.

Natural killer (NK) cells are attractive effector cells of the innate immune system against human immunodeficiency virus (HIV) and cancer. However, NK cell therapies are limited by the fact that target cells evade NK cells, for example, in latent reservoirs (in HIV) or through upregulation of inhibitory signals (in cancer). To address this limitation, we describe a biodegradable nanoparticle-based "priming" approach to enhance the cytotoxic efficacy of peripheral blood mononuclear cell-derived NK cells. We present poly(lactic-co-glycolic acid) (PLGA) nanodepots (NDs) that co-encapsulate prostratin, a latency-reversing agent, and anti-CD25 (aCD25), a cell surface binding antibody, to enhance primary NK cell function against HIV and cancer. We utilize a nanoemulsion synthesis scheme to encapsulate both prostratin and aCD25 within the PLGA NDs (termed Pro-aCD25-NDs). Physicochemical characterization studies of the NDs demonstrated that our synthesis scheme resulted in stable and monodisperse Pro-aCD25-NDs. The NDs successfully released both active prostratin and anti-CD25, and with controllable release kinetics. When Pro-aCD25-NDs were administered in an in vitro model of latent HIV and acute T cell leukemia using J-Lat 10.6 cells, the NDs were observed to prime J-Lat cells resulting in significantly increased NK cell-mediated cytotoxicity compared to free prostratin plus anti-CD25, and other controls. These findings demonstrate the feasibility of using our Pro-aCD25-NDs to prime target cells for enhancing the cytotoxicity of NK cells as antiviral or antitumor agents.

Engineering the TGFß Receptor to Enhance the Therapeutic Potential of Natural Killer Cells as an Immunotherapy for Neuroblastoma.

PURPOSE: The ability of natural killer (NK) cells to lyse allogeneic targets, without the need for explicit matching or priming, makes them an attractive platform for cell-based immunotherapy. Umbilical cord blood is a practical source for generating banks of such third-party NK cells for "off-the-shelf" cell therapy applications. NK cells are highly cytolytic, and their potent antitumor effects can be rapidly triggered by a lack of HLA expression on interacting target cells, as is the case for a majority of solid tumors, including neuroblastoma. Neuroblastoma is a leading cause of pediatric cancer-related deaths and an ideal candidate for NK-cell therapy. However, the antitumor efficacy of NK cells is limited by immunosuppressive cytokines in the tumor microenvironment, such as TGFß, which impair NK cell function and survival. EXPERIMENTAL DESIGN: To overcome this, we genetically modified NK cells to express variant TGFß receptors, which couple a mutant TGFß dominant-negative receptor to NK-specific activating domains. We hypothesized that with these engineered receptors, inhibitory TGFß signals are effectively converted to activating signals. RESULTS: Modified NK cells exhibited higher cytotoxic activity against neuroblastoma in a TGFß-rich environment in vitro and superior progression-free survival in vivo, as compared with their unmodified controls. CONCLUSIONS: Our results support the development of "off-the-shelf" gene-modified NK cells, that overcome TGFß-mediated immune evasion, in patients with neuroblastoma and other TGFß-secreting malignancies.

Beyond CAR T Cells: Other Cell-Based Immunotherapeutic Strategies Against Cancer.

Background: Chimeric antigen receptor (CAR)-modified T cells have successfully harnessed T cell immunity against malignancies, but they are by no means the only cell therapies in development for cancer. Main Text Summary: Systemic immunity is thought to play a key role in combatting neoplastic disease; in this vein, genetic modifications meant to explore other components of T cell immunity are being evaluated. In addition, other immune cells-from both the innate and adaptive compartments-are in various stages of clinical application. In this review, we focus on these non-CAR T cell immunotherapeutic approaches for malignancy. The first section describes engineering T cells to express non-CAR constructs, and the second section describes other gene-modified cells used to target malignancy. Conclusions: CAR T cell therapies have demonstrated the clinical benefits of harnessing our body's own defenses to combat tumor cells. Similar research is being conducted on lesser known modifications and gene-modified immune cells, which we highlight in this review.

Composite iron oxide-Prussian blue nanoparticles for magnetically guided T1-weighted magnetic resonance imaging and photothermal therapy of tumors.

Theranostic nanoparticles offer the potential for mixing and matching disparate diagnostic and therapeutic functionalities within a single nanoparticle for the personalized treatment of diseases. In this article, we present composite iron oxide-gadolinium-containing Prussian blue nanoparticles (Fe3O4@GdPB) as a novel theranostic agent for T1-weighted magnetic resonance imaging (MRI) and photothermal therapy (PTT) of tumors. These particles combine the well-described properties and safety profiles of the constituent Fe3O4 nanoparticles and gadolinium-containing Prussian blue nanoparticles. The Fe3O4@GdPB nanoparticles function both as effective MRI contrast agents and PTT agents as determined by characterizing studies performed in vitro and retain their properties in the presence of cells. Importantly, the Fe3O4@GdPB nanoparticles function as effective MRI contrast agents in vivo by increasing signal:noise ratios in T1-weighted scans of tumors and as effective PTT agents in vivo by decreasing tumor growth rates and increasing survival in an animal model of neuroblastoma. These findings demonstrate the potential of the Fe3O4@GdPB nanoparticles to function as effective theranostic agents.

Photothermal therapy improves the efficacy of a MEK inhibitor in neurofibromatosis type 1-associated malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive tumors with low survival rates and the leading cause of death in neurofibromatosis type 1 (NF1) patients under 40 years old. Surgical resection is the standard of care for MPNSTs, but is often incomplete and can generate loss of function, necessitating the development of novel treatment methods for this patient population. Here, we describe a novel combination therapy comprising MEK inhibition and nanoparticle-based photothermal therapy (PTT) for MPNSTs. MEK inhibitors block activity driven by Ras, an oncogene constitutively activated in NF1-associated MPNSTs, while PTT serves as a minimally invasive method to ablate cancer cells. Our rationale for combining these seemingly disparate techniques for MPNSTs is based on several reports demonstrating the efficacy of systemic chemotherapy with local PTT. We combine the MEK inhibitor, PD-0325901 (PD901), with Prussian blue nanoparticles (PBNPs) as PTT agents, to block MEK activity and simultaneously ablate MPNSTs. Our data demonstrate the synergistic effect of combining PD901 with PBNP-based PTT, which converge through the Ras pathway to generate apoptosis, necrosis, and decreased proliferation, thereby mitigating tumor growth and increasing survival of MPNST-bearing animals. Our results suggest the potential of this novel local-systemic combination "nanochemotherapy" for treating patients with MPNSTs.

Conjugating Prussian blue nanoparticles onto antigen-specific T cells as a combined nanoimmunotherapy.

AIM: To engineer a novel nanoimmunotherapy comprising Prussian blue nanoparticles (PBNPs) conjugated to antigen-specific cytotoxic T lymphocytes (CTL), which leverages PBNPs for their photothermal therapy (PTT) capabilities and Epstein-Barr virus (EBV) antigen-specific CTL for their ability to traffic to and destroy EBV antigen-expressing target cells. MATERIALS & METHODS: PBNPs and CTL were independently biofunctionalized. Subsequently, PBNPs were conjugated onto CTL using avidin-biotin interactions. The resultant cell-nanoparticle construct (CTL:PBNPs) were analyzed for their physical, phenotypic and functional properties. RESULTS: Both PBNPs and CTL maintained their intrinsic physical, phenotypic and functional properties within the CTL:PBNPs. CONCLUSION: This study highlights the potential of our CTL:PBNPs nanoimmunotherapy as a novel therapeutic for treating virus-associated malignancies such as EBV+ cancers.

Phase I Hepatic Immunotherapy for Metastases Study of Intra-Arterial Chimeric Antigen Receptor-Modified T-cell Therapy for CEA+ Liver Metastases.

PURPOSE: Chimeric antigen receptor-modified T cells (CAR-T) have demonstrated encouraging results in early-phase clinical trials. Successful adaptation of CAR-T technology for CEA-expressing adenocarcinoma liver metastases, a major cause of death in patients with gastrointestinal cancers, has yet to be achieved. We sought to test intrahepatic delivery of anti-CEA CAR-T through percutaneous hepatic artery infusions (HAIs). EXPERIMENTAL DESIGN: We conducted a phase I trial to test HAI of CAR-T in patients with CEA(+) liver metastases. Six patients completed the protocol, and 3 received anti-CEA CAR-T HAIs alone in dose-escalation fashion (10(8), 10(9), and 10(10) cells). We treated an additional 3 patients with the maximum planned CAR-T HAI dose (10(10) cells × 3) along with systemic IL2 support. RESULTS: Four patients had more than 10 liver metastases, and patients received a mean of 2.5 lines of conventional systemic therapy before enrollment. No patient suffered a grade 3 or 4 adverse event related to the CAR-T HAIs. One patient remains alive with stable disease at 23 months following CAR-T HAI, and 5 patients died of progressive disease. Among the patients in the cohort that received systemic IL2 support, CEA levels decreased 37% (range, 19%-48%) from baseline. Biopsies demonstrated an increase in liver metastasis necrosis or fibrosis in 4 of 6 patients. Elevated serum IFNγ levels correlated with IL2 administration and CEA decreases. CONCLUSIONS: We have demonstrated the safety of anti-CEA CAR-T HAIs with encouraging signals of clinical activity in a heavily pretreated population with large tumor burdens. Further clinical testing of CAR-T HAIs for liver metastases is warranted.

Liver metastases induce reversible hepatic B cell dysfunction mediated by Gr-1+CD11b+ myeloid cells.

LM escape immune surveillance, in part, as a result of the expansion of CD11b+MC, which alter the intrahepatic microenvironment to promote tumor tolerance. HBC make up a significant proportion of liver lymphocytes and appear to delay tumor progression; however, their significance in the setting of LM is poorly defined. Therefore, we characterized HBC and HBC/CD11b+MC interactions using a murine model of LM. Tumor-bearing livers showed a trend toward elevated absolute numbers of CD19+ HBC. A significant increase in the frequency of IgM(lo)IgD(hi) mature HBC was observed in mice with LM compared with normal mice. HBC derived from tumor-bearing mice demonstrated increased proliferation in response to TLR and BCR stimulation ex vivo compared with HBC from normal livers. HBC from tumor-bearing livers exhibited significant down-regulation of CD80 and were impaired in inducing CD4(+) T cell proliferation ex vivo. We implicated hepatic CD11b+MC as mediators of CD80 down-modulation on HBC ex vivo via a CD11b-dependent mechanism that required cell-to-cell contact and STAT3 activity. Therefore, CD11b+MC may compromise the ability of HBC to promote T cell activation in the setting of LM as a result of diminished expression of CD80. Cross-talk between CD11b+MC and HBC may be an important component of LM-induced immunosuppression.