Andreia Maia

Cancer cells remodel their metabolic environment to disable infiltrating immune cells. Adenosine is a principal mediator of this immunosuppression, impairing the metabolism and effector functions of T and natural killer (NK) cells. Blocking adenosine receptors or production within a redundant signaling network leaves the metabolite itself intact and has shown limited clinical efficacy. Adenosine deaminase (ADA) instead converts adenosine into inosine, a metabolite that can fuel T cell metabolism. We engineered non-pathogenic, tumor-tropic Escherichia coli K-12 DH5α to surface-display ADA, confining this metabolic switch to the tumor, and co-displayed interleukin-12 (IL-12) to couple metabolic rescue to local immune stimulation. Bacteria-displayed ADA alone restored metabolic and proliferative fitness in adenosine-suppressed lymphocytes to baseline, whereas incorporation of IL-12 coupled this rescue to enhanced effector function. Across multiple preclinical models of hematologic and solid malignancies, the dual-function bacteria were well tolerated, enhanced tumor control, prolonged survival, and induced durable protective immunity against melanoma rechallenge. The bacteria were enriched at tumor sites, reactivated quiescent immune compartments in leukemia, enhanced CAR-NK cell tumor trafficking and activity in pancreatic cancer, and outperformed recombinant proteins in breast cancer. These findings establish a modular living immunotherapeutic strategy that couples a local extracellular metabolic switch with localized cytokine delivery.

Solid tumors evade immunotherapy because of immunosuppressive microenvironments that limit immune cell persistence and function. Although interleukin-12 (IL-12) potently activates antitumor immunity, its clinical use has been constrained by systemic toxicity. Here we engineered a CAR natural killer (NK) cell platform that integrated IL-12 signaling to enhance antitumor immunity. IL-12 signaling synergized with CAR activation to sustain mTORC1 activity through convergent Ras-ERK and PI3K pathways, promoting metabolic fitness, autonomous expansion, and sustained effector function. IL-12 also activated bystander NK cells, T cells, and macrophages to remodel the tumor microenvironment. To improve safety, IL-12 was tethered to a collagen-binding A3-domain, restricting its activity to the extracellular matrix and limiting systemic exposure. In ovarian and pancreatic cancer models, matrix-anchored IL-12 CAR NK cells expanded without exogenous cytokines and achieved durable tumor control. These findings suggest that mTORC1-mediated integration of CAR and cytokine signaling can enhance immune fitness and overcome immunosuppressive tumor microenvironments.

Pancreatic ductal adenocarcinoma (PDAC) has high mortality rates, poor prognosis, and currently limited effective treatments. Natural killer (NK) cells from tumor-infiltrating lymphocytes (TIL) show promise for cancer treatment due to their ability to migrate to the tumor microenvironment (TME) and safe profile. However, expanding functional patient-derived NK cells remains challenging. Here, we cultured, expanded, and characterized TIL-NK cells isolated from central and peripheral tumor regions from PDAC. Ex vivo patient-derived PBMCs and TIL were cultured under IL-2, IL-15, and IL-12 stimulation. Phenotypical and functional NK cell characterization was assessed at the time of surgery and after 12 days of culture evaluating immunophenotype, expansion rate, and activation. A distinct distribution of NK cell infiltration was observed within the TME, with higher NK cell numbers in the periphery of the tumor compared to the central area. Most NK cells displayed a cytotoxic phenotype (CD56⁺ CD16⁺). Compared to PBMCs, TIL-NK cells expressed lower activation markers but superior tumor infiltration and expansion rates, particularly those isolated from the central regions. Notably, cytokine stimulation improved patient-derived NK cell activation and cytotoxic profile. This pilot study provides preliminary but critical insights regarding TIL-NK cells from PDAC patients, laying groundwork for developing NK cell-based immunotherapies for solid tumors.

Tumor immune escape is a major barrier to durable cancer immunotherapy, as advanced malignancies create a tumor microenvironment (TME) that preferentially exhausts and disables T cell responses. While most approved cell therapies are T cell‐based, this limitation motivates the exploration of an alternative effector cell platform. Natural killer (NK) cells, innate cytotoxic lymphocytes capable of antigen‐independent recognition and killing, offer a compelling foundation for next‐generation therapies with an improved safety profile. In this review, we first outline the cellular, molecular, and metabolic features of the immunosuppressive TME that restrict cytotoxic lymphocyte function, emphasizing mechanisms that limit immune cell‐mediated responses. We then summarize key aspects of NK cell biology that can circumvent these barriers and critically evaluate current NK‐based strategies, including engineered chimeric antigen receptor (CAR)‐NK products and metabolic and trafficking interventions. Finally, we highlight emerging in vivo viral and mRNA/lipid nanoparticle platforms for CAR‐NK generation and their potential to enhance scalability and therapeutic durability.

Epithelial ovarian cancer (EOC) remains one of the most lethal gynecological cancers. Cytokine-induced memory–like (CIML) natural killer (NK) cells have shown promising results in preclinical and early-phase clinical trials. In the current study, CIML NK cells demonstrated superior antitumor responses against a panel of EOC cell lines, increased expression of activation receptors, and up-regulation of genes involved in cell cycle/proliferation and down-regulation of inhibitory/suppressive genes. CIML NK cells transduced with a chimeric antigen receptor (CAR) targeting the membrane-proximal domain of mesothelin (MSLN) further improved the antitumor responses against MSLN-expressing EOC cells and patient-derived xenograft tumor cells. CAR arming of the CIML NK cells subtanstially reduced their dysfunction in patient-derived ascites fluid with transcriptomic changes related to altered metabolism and tonic signaling as potential mechanisms. Lastly, the adoptive transfer of MSLN-CAR CIML NK cells demonstrated remarkable inhibition of tumor growth and prevented metastatic spread in xenograft mice, supporting their potential as an effective therapeutic strategy in EOC.

Natural killer (NK) cells have gained attention as a promising adoptive cell therapy platform for their potential to improve cancer treatments. NK cells offer distinct advantages over T-cells, including major histocompatibility complex class I (MHC-I)-independent tumor recognition and low risk of toxicity, even in an allogeneic setting. Despite this tremendous potential, challenges persist, such as limited in vivo persistence, reduced tumor infiltration, and low absolute NK cell numbers. This review outlines several strategies aiming to overcome these challenges. The developed strategies include optimizing NK cell expansion methods and improving NK cell antitumor responses by cytokine stimulation and genetic manipulations. Using K562 cells expressing membrane IL-15 or IL-21 with or without additional activating ligands like 4-1BBL allows “massive” NK cell expansion and makes multiple cell dosing and “off-the-shelf” efforts feasible. Further improvements in NK cell function can be reached by inducing memory-like NK cells, developing chimeric antigen receptor (CAR)-NK cells, or isolating NK-cell-based tumor-infiltrating lymphocytes (TILs). Memory-like NK cells demonstrate higher in vivo persistence and cytotoxicity, with early clinical trials demonstrating safety and promising efficacy. Recent trials using CAR-NK cells have also demonstrated a lack of any major toxicity, including cytokine release syndrome, and, yet, promising clinical activity. Recent data support that the presence of TIL-NK cells is associated with improved overall patient survival in different types of solid tumors such as head and neck, colorectal, breast, and gastric carcinomas, among the most significant. In conclusion, this review presents insights into the diverse strategies available for NK cell expansion, including the roles played by various cytokines, feeder cells, and culture material in influencing the activation phenotype, telomere length, and cytotoxic potential of expanded NK cells. Notably, genetically modified K562 cells have demonstrated significant efficacy in promoting NK cell expansion. Furthermore, culturing NK cells with IL-2 and IL-15 has been shown to improve expansion rates, while the presence of IL-12 and IL-21 has been linked to enhanced cytotoxic function. Overall, this review provides an overview of NK cell expansion methodologies, highlighting the current landscape of clinical trials and the key advancements to enhance NK-cell-based adoptive cell therapy.

Natural killer (NK) cells are a subset of cytotoxic lymphocytes within the innate immune system. While they are naturally cytotoxic, genetic modifications can enhance their tumor-targeting capability, cytotoxicity, persistence, tumor infiltration, and prevent exhaustion. These improvements hold the potential to make NK-cell-based immunotherapies more effective in clinical applications. Currently, several viral and non-viral technologies are used to genetically modify NK cells. For nucleic acid delivery, non-viral methods such as electroporation, lipid nanoparticles, lipofection, and DNA transposons have gained popularity in recent years. On the other hand, viral methods including lentivirus, gamma retrovirus, and adeno-associated virus, remain widely used for gene delivery. Furthermore, gene editing techniques such as clustered regularly interspaced short-palindromic repeats-based, zinc finger nucleases, and transcription activator-like effector nucleases are the pivotal methodologies in this field. This review aims to provide a comprehensive overview of chimeric antigen receptor (CAR) arming strategies and discuss key gene editing techniques. These approaches collectively aim to enhance NK cell/NK cell CAR-based immunotherapies for clinical translation.

Background The tumor microenvironment (TME) is a complex system, where malignant cells co-exist and communicate with immune and non-immune cells.¹ This interaction orchestrates an immune response that regulates and recruits other immune cells that may either promote cancer growth or mediate tumor regression.² The number and spatiotemporal distribution of tumor-infiltrating lymphocytes (TILs) in the TME, as well as NK cells, have been correlated with favorable prognosis in patients with colorectal cancer or pancreatic adenocarcinomas (CRC and PDAC).^3–5 A more detailed analysis of the TME landscape composition will help to understand which specific areas will give rise to immune cells with clinically relevant anti–cancer-directed responses and could be preferentially expanded for immunotherapy using tumor-infiltrating NK cells. Methods Fresh CRC (n=6) and PDAC (n=6) tumor specimens were obtained within 20 minutes after surgery. A certified GI pathologist collected central and periphery tumor regions. From each region, half of the specimen was used for immunophenotypic analysis, the other half was cultured with IL-2 (1000 IU/mL) for 12 days. Immunophenotyping was performed using CD45, CD19, CD3, CD4, CD8, CD56, CD16, and LiveDead marker by flow cytometry at days 0, 6, and 12. Parallel formalin-fixed paraffin-embedded blocks were generated and analyzed by immunohistochemistry (IHC) for CD8 and CD56. Results The immuneprofile of the tumor center and periphery is different both in CRC and PDAC. The mean percentages of B-cells, T-cells (CD4⁺ and CD8⁺ T-cells) and NK cells (CD56^bright CD16^- and CD56⁺ CD16⁺) of tumor regions are presented in figure 1) are more abundant in the TME and formed larger clusters than NK cells (figure 2). The majority of NK cells were found in the stroma however, in some cases, NK cells were located within the malignant epithelium. Representation of percentage of immune cells in the central and periphery tumor regions of both CRC and PDAC tissues. The mean percentage of B-cells, T-cells (including CD4⁺ and CD8⁺-T-cells) and NK cells (including CD56^bright CD16^- and CD56⁺ CD16⁺ subpopulation) during ex vivo expansion (day 0, day 6 and day 12) are represented from the different regions of both CRC (n=6) and PDA (n=6). Representative IHC images of CD8+- T-cells in different regions: stroma (periphery and intratumoral) and intraepithelial of both CRC (n=3) and PDAC (n=3). Semi-quantitative analysis of CD8+- T-cells (from negative (-) to high numbers (+++)). Yellow arrows point to intraepithelial CD8+- T-cells. Scale bar corresponds to 50 µm. Representative IHC images of CD56+ NK cells in different regions: stroma (periphery and intratumoral) and intraepithelial of both CRC (n=3) and PDAC (n=3). Semi-quantitative analysis of CD56+ NK cells (from negative (-) to high numbers (+++)). Yellow arrows point to intraepithelial CD56+ NK cells. Scale bar corresponds to 50 µm. Conclusions Our data in this small set of specimens show that TME immune cells in central and periphery tumor regions present different phenotypes in both tumor types. The tumor periphery exhibits a stronger infiltration with TIL and NK cells as compared to the center. We also observed that immune cells are in close physical contact with tumor cells since they were identified inside the malignant epithelium in some specimens. NK-cells and particularly TIL close to cancer cells may be preferentially harvested to obtain improved anti-cancer-directed NK or TCR alpha-beta-directed immune cell products for active immunotherapy. Acknowledgements The authors would like to thank the Champalimaud Foundation Biobank of the Champalimaud Centre for the Unknown for anonymously releasing tissue specimens. Trial Registration N/A References Giraldo NA, Sanchez-Salas R, Peske JD, Vano Y, Becht E, Petitprez F, Validire P, Ingels A, Cathelineau X, Fridman WH, et al. The clinical role of the TME in solid cancer. Br J Cancer (2019);120:45–53. Li L, Yu R, Cai T, Chen Z, Lan M, Zou T, Wang B, Wang Q, Zhao Y, Cai Y. Effects of immune cells and cytokines on inflammation and immunosuppression in the tumor microenvironment. Int Immunopharmacol (2020);88:106939. Lianyuan T, Dianrong X, Chunhui Y, Zhaolai M, Bin J. The predictive value and role of stromal tumor-infiltrating lymphocytes in pancreatic ductal adenocarcinoma (PDAC). Cancer Biol Ther (2018);19:296–305. Idos GE, Kwok J, Bonthala N, Kysh L, Gruber SB, Qu C. The prognostic implications of tumor-infiltrating lymphocytes in colorectal cancer: a systematic review and meta-analysis. Sci Rep (2020);10:3360. Zhang S, Liu W, Hu B, Wang P, Lv X, Chen S, Shao Z. Prognostic significance of tumor-infiltrating natural killer cells in solid tumors: a systematic review and meta-analysis. Front Immunol (2020);11:1–11. Ethics Approval This study was approved by the Champalimaud Foundation Ethics Committee and by the Ethics Research Committee of NOVA Medical School of NOVA University of Lisbon; approval number 56. Consent Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

Background SARS-CoV-2 primarily infects the upper and lower airway system, yet also endothelial cells and multiple tissues/organ systems. Anti-SARS-CoV-2 directed cellular immune responses may be deleterious or may confer immune protection – more research is needed in order to link epitope-specific T-cell responses with clinically relevant endpoints.¹ Analysis of epitope reactivity in blood from healthy individuals showed pre-existing (CD4+) reactivity most likely due to previous exposure to the common old coronavirus species HCoV-OC43, HCoV-229E, - NL63 or HKU1, or – not mutually exclusive - cross-reactive T-cell responses that would recognize SARS-CoV-2, yet also other non-SARS-CoV-2 targets.^2,3 Detailed single cell analysis in PBMCs from patients with COVID-19 showed strong T-cell activation and expansion of TCR gamma – delta T-cells in patients with fast recovery or mild clinical symptoms.⁴ Previous studies examining antigen-specific T-cell responses in tumor-infiltrating T-cells (TIL) showed that EBV or CMV-specific cellular immune responses in TIL from patients with melanoma or pancreatic cancer. Such virus -specific T-cells may represent ‘bystander’ T-cell activation, yet they may also impact on the quality and quantity of anti-tumor directed immune responses. We tested therefore TIL expanded from 5 patients with gastrointestinal cancer, who underwent elective tumor surgery during the COVID-19 pandemic for recognition of a comprehensive panel of SARS-CoV-2 T-cell epitopes and compared the reactivity, defined by IFN-gamma production to TIL reactivity in TIL harvested from patients in 2018, prior to the pandemic. Methods A set of 187 individual T-cell epitopes were tested for TIL recognition using 100IU IL-2 and 100 IU IL-15. Different peptide epitopes were selected: i) all epitopes were not shared with the 4 common old coronavirus species, ii) some peptides were unique for SARS-CoV-2, and iii) others were shared with SARS-CoV-1. Antigen targets were either 15 mers or 9mers for MHC class II or class I epitopes, respectively, derived from the nucleocapsid, membrane, spike protein, ORF8 or the ORF3a. The amount of IFN-gamma production was reported as pg/10e4 cells/epitope/5 days. Controls included CMV and EBV peptides. Results We detected strong IFN-gamma production directed against antigenic ‘hotspots’ including the ORF3a, epitopes from the SARS-CoV-2 nucleocapsid and spike protein with a range of 12 up to 30 targets being recognized/TIL. Conclusions SARS-CoV-2 epitope recognition, defined by IFN production, can be readily detected in TIL from patients who underwent surgery during the pandemic, which is not the case for TIL harvested prior to the circulating SARS-CoV-2. This suggests a broader exposure of individuals to SARS-CoV-2 and shows that SARS-CoV-2 responses may shape the quality and quantity of anti-cancer directed cellular immune responses in patients with solid epithelial malignancies. Acknowledgements We thank the Surgery, Pathology and Vivarium Units of Champalimaud Clinical Center (N. Figueiredo, A. Brandl, A. Beltran, M. Castillo, C. Silva ). Ethics Approval This study was approved by the Champalimaud Foundation Ethics Committee. Consent All donors provided written consent and the study was approved by the local ethics committee. The study is in compliance with the Declaration of Helsinki. References Grifoni, A., Weiskopf, D., Ramirez, S. I., Mateus, J., Dan, J. M., Moderbacher, C. R., Rawlings, S. A., Sutherland, A., Premkumar, L., Jadi, R. S., Marrama, D., de Silva, A. M., Frazier, A., Carlin, A. F., Greenbaum, J. A., Peters, B., Krammer, F., Smith, D. M., Crotty, S., & Sette, A. ( 2020). Targets of T Cell Responses to SARS-CoV-2 Coronavirus in Humans with COVID-19 Disease and Unexposed Individuals. Cell, 181(7), 1489–1501.e15. https://doi.org/10.1016/j.cell.2020.05.015 Mateus, J., Grifoni, A., Tarke, A., Sidney, J., Ramirez, S. I., Dan, J. M., Burger, Z. C., Rawlings, S. A., Smith, D. M., Phillips, E., Mallal, S., Lammers, M., Rubiro, P., Quiambao, L., Sutherland, A., Yu, E. D., da Silva Antunes, R., Greenbaum, J., Frazier, A., … Weiskopf, D. ( 2020). Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans. Science, eabd3871. https://doi.org/10.1126/science.abd3871 Le Bert, N., Tan, A. T., Kunasegaran, K., Tham, C. Y. L., Hafezi, M., Chia, A., Chng, M. H. Y., Lin, M., Tan, N., Linster, M., Chia, W. N., Chen, M. I.-C., Wang, L.-F., Ooi, E. E., Kalimuddin, S., Tambyah, P. A., Low, J. G.-H., Tan, Y.-J., & Bertoletti, A. ( 2020). SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls. Nature, 584(7821), 457–462. https://doi.org/10.1038/s41586-020-2550-z Zhang, J., Wang, X., Xing, X. et al. Single-cell landscape of immunological responses in patients with COVID-19. Nat Immunol 2020;21:1107–1118. https://doi.org/10.1038/s41590-020-0762-x

Memory formation, guided by microbial ligands, has been reported for innate immune cells. Epigenetic imprinting plays an important role herein, involving histone modification after pathogen-/danger-associated molecular patterns (PAMPs/DAMPs) recognition by pattern recognition receptors (PRRs). Such “trained immunity” affects not only the nominal target pathogen, yet also non-related targets that may be encountered later in life. The concept of trained innate immunity warrants further exploration in cancer and how these insights can be implemented in immunotherapeutic approaches. In this review, we discuss our current understanding of innate immune memory and we reference new findings in this field, highlighting the observations of trained immunity in monocytic and natural killer cells. We also provide a brief overview of trained immunity in non-immune cells, such as stromal cells and fibroblasts. Finally, we present possible strategies based on trained innate immunity that may help to devise host-directed immunotherapies focusing on cancer, with possible extension to infectious diseases.