IL-15-secreting CAR natural killer cells directed toward the pan-cancer target CD70 eliminate both cancer cells and cancer-associated fibroblasts

BACKGROUND

It remains challenging to obtain positive outcomes with chimeric antigen receptor (CAR)-engineered cell therapies in solid malignancies, like colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC). A major obstacle is the lack of targetable surface antigens that are not shared by healthy tissues. CD70 emerges as interesting target, due to its stringent expression pattern in healthy tissue and its apparent role in tumor progression in a considerable amount of malignancies. Moreover, CD70 is also expressed on cancer-associated fibroblasts (CAFs), another roadblock for treatment efficacy in CRC and PDAC. We explored the therapeutic potential of CD70 as target for CAR natural killer (NK) cell therapy in CRC, PDAC, focusing on tumor cells and CAFs, and lymphoma.

METHODS

RNA-seq data and immunohistochemical analysis of patient samples were used to explore CD70 expression in CRC and PDAC patients. In addition, CD70-targeting CAR NK cells were developed to assess cytotoxic activity against CD70+ tumor cells and CAFs, and the effect of cytokine stimulation on their efficacy was evaluated. The in vitro functionality of CD70-CAR NK cells was investigated against a panel of tumor and CAF cell lines with varying CD70 expression. Lymphoma-bearing mice were used to validate in vivo potency of CD70-CAR NK cells. Lastly, to consider patient variability, CD70-CAR NK cells were tested on patient-derived organoids containing CAFs.

RESULTS

In this study, we identified CD70 as a target for tumor cells and CAFs in CRC and PDAC patients. Functional evaluation of CD70-directed CAR NK cells indicated that IL-15 stimulation is essential to obtain effective elimination of CD70+ tumor cells and CAFs, and to improve tumor burden and survival of mice bearing CD70+ tumors. Mechanistically, IL-15 stimulation resulted in improved potency of CD70-CAR NK cells by upregulating CAR expression and increasing secretion of pro-inflammatory cytokines, in a mainly autocrine or intracellular manner.

CONCLUSIONS

We disclose CD70 as an attractive target both in hematological and solid tumors. IL-15 armored CAR NK cells act as potent effectors to eliminate these CD70+ cells. They can target both tumor cells and CAFs in patients with CRC and PDAC, and potentially other desmoplastic solid tumors.

Site-specific 68Ga-labeled nanobody for PET imaging of CD70 expression in preclinical tumor models

BACKGROUND

CD70-CD27 is a costimulatory ligand-receptor pair in the tumor necrosis factor receptor family. With only limited expression in normal tissues, CD70 is constitutively expressed in a variety of solid tumors and hematologic malignancies, facilitating immunosuppression through CD27 signaling in the tumor microenvironment by enhanced survival of regulatory T cells, induction of T cell apoptosis, and T cell exhaustion. Consequently, CD70 is an increasingly recognized target for developing antibody-based therapies, but its expression patterns vary among different tumor types in spatial distribution, magnitude of expression and percentage of positive cells. In that regard, individual confirmation of CD70 expression at screening and during treatment could enhance the successful implementation of anti-CD70 therapies. Here, we developed a gallium-68 (⁶⁸Ga) radiolabeled single-domain antibody-fragment targeting CD70 for in vivo positron emission tomography (PET) imaging.

RESULTS

An anti-CD70 VHH construct containing a C-direct-tag with a free thiol was developed to enable site-specific conjugation to a NOTA bifunctional chelator for ⁶⁸Ga radiolabeling. [⁶⁸Ga]Ga-NOTA-anti-CD70 VHH was obtained in good radiochemical yield of 30.4 ± 1.7% and high radiochemical purity (> 94%). The radiolabeled VHH showed excellent in vitro and in vivo stability. Specific binding of [⁶⁸Ga]Ga-NOTA-anti-CD70 VHH was observed on CD70^high 786-O cells, showing significantly higher cell-associated activity when compared to the blocking condition (p < 0.0001) and CD70^low NCl-H1975 cells (p < 0.0001). PET imaging showed specific radiotracer accumulation in CD70 expressing human tumor xenografts, which was efficiently blocked by prior injection of unlabeled anti-CD70 VHH (p = 0.0029). In addition, radiotracer uptake in CD70^high tumors was significantly higher when compared with CD70^low tumors (p < 0.0001). The distribution of the radioactivity in the tumors using autoradiography was spatially matched with immunohistochemistry analysis of CD70 expression.

CONCLUSION

[⁶⁸Ga]Ga-NOTA-anti-CD70 VHH showed excellent in vivo targeting of CD70 in human cancer xenografts. PET imaging using this radioimmunoconjugate holds promise as a non-invasive method to identify and longitudinally follow-up patients who will benefit most from anti-CD70 therapies.

Auranofin Synergizes with the PARP Inhibitor Olaparib to Induce ROS-Mediated Cell Death in Mutant p53 Cancers

Auranofin (AF) is a potent, off-patent thioredoxin reductase (TrxR) inhibitor that efficiently targets cancer via reactive oxygen species (ROS)- and DNA damage-mediated cell death. The goal of this study is to enhance the efficacy of AF as a cancer treatment by combining it with the poly(ADP-ribose) polymerase-1 (PARP) inhibitor olaparib (referred to as ‘aurola’). Firstly, we investigated whether mutant p53 can sensitize non-small cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC) cancer cells to AF and olaparib treatment in p53 knock-in and knock-out models with varying p53 protein expression levels. Secondly, we determined the therapeutic range for synergistic cytotoxicity between AF and olaparib and elucidated the underlying molecular cell death mechanisms. Lastly, we evaluated the effectiveness of the combination strategy in a murine 344SQ 3D spheroid and syngeneic in vivo lung cancer model. We demonstrated that high concentrations of AF and olaparib synergistically induced cytotoxicity in NSCLC and PDAC cell lines with low levels of mutant p53 protein that were initially more resistant to AF. The aurola combination also led to the highest accumulation of ROS, which resulted in ROS-dependent cytotoxicity of mutant p53 NSCLC cells through distinct types of cell death, including caspase-3/7-dependent apoptosis, inhibited by Z-VAD-FMK, and lipid peroxidation-dependent ferroptosis, inhibited by ferrostatin-1 and alpha-tocopherol. High concentrations of both compounds were also needed to obtain a synergistic cytotoxic effect in 3D spheroids of the murine lung adenocarcinoma cell line 344SQ, which was interestingly absent in 2D. This cell line was used in a syngeneic mouse model in which the oral administration of aurola significantly delayed the growth of mutant p53 344SQ tumors in 129S2/SvPasCrl mice, while either agent alone had no effect. In addition, RNA sequencing results revealed that AF- and aurola-treated 344SQ tumors were negatively enriched for immune-related gene sets, which is in accordance with AF’s anti-inflammatory function as an anti-rheumatic drug. Only 344SQ tumors treated with aurola showed the downregulation of genes related to the cell cycle, potentially explaining the growth inhibitory effect of aurola since no apoptosis-related gene sets were enriched. Overall, this novel combination strategy of oxidative stress induction (AF) with PARP inhibition (olaparib) could be a promising treatment for mutant p53 cancers, although high concentrations of both compounds need to be reached to obtain a substantial cytotoxic effect.

Targeting CD70 in combination with chemotherapy to enhance the anti-tumor immune effects in non-small cell lung cancer

Despite the recent emergence of immune checkpoint inhibitors, clinical outcomes of metastatic NSCLC patients remain poor, pointing out the unmet need to develop novel therapies to enhance the anti-tumor immune response in NSCLC. In this regard, aberrant expression of the immune checkpoint molecule CD70 has been reported on many cancer types, including NSCLC. In this study, the cytotoxic and immune stimulatory potential of an antibody-based anti-CD70 (aCD70) therapy was explored as single agent and in combination with docetaxel and cisplatin in NSCLC in vitro and in vivo. Anti-CD70 therapy resulted in NK-mediated killing of NSCLC cells and increased production of pro-inflammatory cytokines by NK cells in vitro. The combination of chemotherapy and anti-CD70 therapy further enhanced NSCLC cell killing. Moreover, in vivo findings showed that the sequential treatment of chemo-immunotherapy resulted in a significant improved survival and delayed tumor growth compared to single agents in Lewis Lung carcinoma-bearing mice. The immunogenic potential of the chemotherapeutic regimen was further highlighted by increased numbers of dendritic cells in the tumor-draining lymph nodes in these tumor-bearing mice after treatment. The sequential combination therapy resulted in enhanced intratumoral infiltration of both T and NK cells, as well as an increase in the ratio of CD8+ T cells over Tregs. The superior effect of the sequential combination therapy on survival was further confirmed in a NCI-H1975-bearing humanized IL15-NSG-CD34+ mouse model. These novel preclinical data demonstrate the potential of combining chemotherapy and aCD70 therapy to enhance anti-tumor immune responses in NSCLC patients.

Cellular senescence in cancer: clinical detection and prognostic implications

Cellular senescence is a state of stable cell-cycle arrest with secretory features in response to cellular stress. Historically, it has been considered as an endogenous evolutionary homeostatic mechanism to eliminate damaged cells, including damaged cells which are at risk of malignant transformation, thereby protecting against cancer. However, accumulation of senescent cells can cause long-term detrimental effects, mainly through the senescence-associated secretory phenotype, and paradoxically contribute to age-related diseases including cancer. Besides its role as tumor suppressor, cellular senescence is increasingly being recognized as an in vivo response in cancer patients to various anticancer therapies. Its role in cancer is ambiguous and even controversial, and senescence has recently been promoted as an emerging hallmark of cancer because of its hallmark-promoting capabilities. In addition, the prognostic implications of cellular senescence have been underappreciated due to the challenging detection and sparse in and ex vivo evidence of cellular senescence in cancer patients, which is only now catching up. In this review, we highlight the approaches and current challenges of in and ex vivo detection of cellular senescence in cancer patients, and we discuss the prognostic implications of cellular senescence based on in and ex vivo evidence in cancer patients.

The CD70-CD27 axis in oncology: the new kids on the block

The immune checkpoint molecule CD70 and its receptor CD27 are aberrantly expressed in many hematological and solid malignancies. Dysregulation of the CD70-CD27 axis within the tumor and its microenvironment is associated with tumor progression and immunosuppression. This is in contrast to physiological conditions, where tightly controlled expression of CD70 and CD27 plays a role in co-stimulation in immune responses. In hematological malignancies, cancer cells co-express CD70 and CD27 promoting stemness, proliferation and survival of malignancy. In solid tumors, only expression of CD70 is present on the tumor cells which can facilitate immune evasion through CD27 expression in the tumor microenvironment. The discovery of these tumor promoting and immunosuppressive effects of the CD70-CD27 axis has unfolded a novel target in the field of oncology, CD70.

In this review, we thoroughly discuss current insights into expression patterns and the role of the CD70-CD27 axis in hematological and solid malignancies, its effect on the tumor microenvironment and (pre)clinical therapeutic strategies.

Auranofin reveals therapeutic anticancer potential by triggering distinct molecular cell death mechanisms and innate immunity in mutant p53 non-small cell lung cancer

Auranofin (AF) is an FDA-approved antirheumatic drug with anticancer properties that acts as a thioredoxin reductase 1 (TrxR) inhibitor. The exact mechanisms through which AF targets cancer cells remain elusive. To shed light on the mode of action, this study provides an in-depth analysis on the molecular mechanisms and immunogenicity of AF-mediated cytotoxicity in the non-small cell lung cancer (NSCLC) cell line NCI–H1299 (p53 Null) and its two isogenic derivates with mutant p53 R175H or R273H accumulation.

TrxR is highly expressed in a panel of 72 NSCLC patients, making it a valid druggable target in NSCLC for AF. The presence of mutant p53 overexpression was identified as an important sensitizer for AF in (isogenic) NSCLC cells as it was correlated with reduced thioredoxin (Trx) levels in vitro. Transcriptome analysis revealed dysregulation of genes involved in oxidative stress response, DNA damage, granzyme A (GZMA) signaling and ferroptosis. Although functionally AF appeared a potent inhibitor of GPX4 in all NCI–H1299 cell lines, the induction of lipid peroxidation and consequently ferroptosis was limited to the p53 R273H expressing cells. In the p53 R175H cells, AF mainly induced large-scale DNA damage and replication stress, leading to the induction of apoptotic cell death rather than ferroptosis. Importantly, all cell death types were immunogenic since the release of danger signals (ecto-calreticulin, ATP and HMGB1) and dendritic cell maturation occurred irrespective of (mutant) p53 expression. Finally, we show that AF sensitized cancer cells to caspase-independent natural killer cell-mediated killing by downregulation of several key targets of GZMA.

Our data provides novel insights on AF as a potent, clinically available, off-patent cancer drug by targeting mutant p53 cancer cells through distinct cell death mechanisms (apoptosis and ferroptosis). In addition, AF improves the innate immune response at both cytostatic (natural killer cell-mediated killing) and cytotoxic concentrations (dendritic cell maturation).

Abstract 2414: Immunogenic properties of chemotherapeutic agents in the treatment of non-small cell lung cancer

Introduction. Accumulating evidence suggests that the clinical success of chemotherapy is not only attributed to direct tumor cell toxicity, but also relies on its anti-tumor effects by immunomodulation. In this regard, the concept of immunogenic cell death (ICD) has emerged as a cornerstone of therapy-induced anti-tumor immunity. To this end, we assessed different chemotherapeutic agents on their ability to induce ICD in vitro and in vivo in non-small cell lung cancer (NSCLC).

Material and methods. NSCLC cell lines (NCI-H1975, A549, NCI-H1650 and LLC) were treated with the IC50 of different chemotherapeutic agents: docetaxel (DOC), carboplatin (CARBO), cisplatin (CDDP), oxaliplatin (OXA) and mafosfamide (MF). In addition, combinations of DOC (IC50) with CARBO (IC40) or CDDP (IC40) were included. Release of important damage-associated molecular patterns (DAMPs) was evaluated: ATP (bioluminescence), ecto-CRT (flow cytometry) and HMGB1 (ELISA) after 24h, 48h and 72h of treatment, respectively. In addition, phagocytosis and maturation status of dendritic cells (DCs) were assessed. Finally, a vaccination assay was performed to validate in vitro findings using 6-week old female C57BL/6J mice (5 mice/condition). Mice were vaccinated twice (1 × 106 treated cells/mouse) before receiving the challenge (5 × 104 live cells/mouse).

Results. Three out of four NSCLC cell lines (NCI-H1975, A549 and LLC) showed significant higher levels of ATP, ecto-CRT and HMGB1 after treatment with DOC, DOC+CARBO and DOC+CDDP compared to vehicle. In addition, phagocytosis of treated tumor cells and maturation (CD86) of DCs were significantly increased in all three human NSCLC cell lines after treatment with the above-mentioned chemotherapeutic regimens. Furthermore, murine LLC cells treated with DOC, MF, DOC+CARBO and DOC+CDDP resulted in a significant release of all three DAMPs in vitro, as opposed to treatment with OXA. Along similar lines, 0%, (DOC+CDDP), 20% (MF and DOC+CARBO) and 80% (OXA) of the mice developed a tumor at the challenge site in vivo. This was not the case for treatment with DOC, which resulted in tumor growth at the challenge site in 60% of the mice.

Conclusion. Overall, these findings demonstrate the immunostimulatory effects of clinically relevant chemotherapeutic regimens, especially DOC+CARBO and DOC+CDDP, making it worthwhile to investigate these agents in combination strategies with immunotherapy in NSCLC.

Citation Format: Tal Flieswasser, Jinthe Van Loenhout, Laurie Freire Boullosa, Astrid Van den Eynde, Jorrit De Waele, Jonas Van Audenaerde, Filip Lardon, Evelien Smits, Patrick Pauwels, Jacobs Julie. Immunogenic properties of chemotherapeutic agents in the treatment of non-small cell lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2414.

Unveiling a CD70-positive subset of cancer-associated fibroblasts marked by pro-migratory activity and thriving regulatory T cell accumulation

Cancer-associated fibroblasts (CAFs) are involved in the proliferative and invasive behavior of colorectal cancer (CRC). Nonetheless, CAFs represent a heterogeneous population with both cancer-promoting and cancer-restraining actions, lacking specific markers to target them. Expression of the immune checkpoint molecule CD70 is normally limited to cells of the lymphoid lineage. Instead, tumor cells hijack CD70 to facilitate immune evasion by increasing the amount of suppressive regulatory T cells (Tregs). The aim of this study was to explore CD70 expression patterns in CRC, not merely focusing on the tumor cells, but also taking the tumor stromal cells into account. We have analyzed the prognostic value of CD70 expression by immunohistochemistry in CRC specimens and its relationship with well-known fibroblast markers and Tregs. In addition, in vitro experiments were conducted to unravel the role of CD70-positive CAFs on migration and immune escape. We reveal prominent expression of CD70 on a specific subset of CAFs in invasive CRC specimens. Cancer cells show almost no expression of CD70. The presence of CD70-positive CAFs proved to be an independent adverse prognostic marker. Functionally, CD70-positive CAFs stimulated migration and significantly increased the frequency of naturally occurring Tregs. In conclusion, we have identified the expression of CD70 on CAFs as a novel prognostic marker for CRC. We have found evidence of a cross talk between CD70⁺ CAFs and naturally occurring Tregs, paving the way towards immune escape. As such, this study provides a strong rationale for the exploration of CD70-targeting antibodies in CRC.