Adoptive NK Cell Transfer as a Treatment in Colorectal Cancer Patients: Analyses of Tumour Cell Determinants Correlating With Efficacy In Vitro and In Vivo

Background

Colorectal cancer (CRC) is a heterogeneous disease with variable mutational profile and tumour microenvironment composition that influence tumour progression and response to treatment. While chemoresistant and poorly immunogenic CRC remains a challenge, the development of new strategies guided by biomarkers could help stratify and treat patients. Allogeneic NK cell transfer emerges as an alternative against chemoresistant and poorly immunogenic CRC.

Methods

NK cell-related immunological markers were analysed by transcriptomics and immunohistochemistry in human CRC samples and correlated with tumour progression and overall survival. The anti-tumour ability of expanded allogeneic NK cells using a protocol combining cytokines and feeder cells was analysed in vitro and in vivo and correlated with CRC mutational status and the expression of ligands for immune checkpoint (IC) receptors regulating NK cell activity.

Results

HLA-I downmodulation and NK cell infiltration correlated with better overall survival in patients with a low-stage (II) microsatellite instability-high (MSI-H) CRC, suggesting a role of HLA-I as a prognosis biomarker and a potential benefit of NK cell immunotherapy. Activated allogeneic NK cells were able to eliminate CRC cultures without PD-1 and TIM-3 restriction but were affected by HLA-I expression. In vivo experiments confirmed the efficacy of the therapy against both HLA⁺ and HLA⁻ CRC cell lines. Concomitant administration of pembrolizumab failed to improve tumour control.

Conclusions

Our results reveal an immunological profile of CRC tumours in which immunogenicity (MSI-H) and immune evasion mechanisms (HLA downmodulation) favour NK cell immunosurveillance at early disease stages. Accordingly, we have shown that allogeneic NK cell therapy can target tumours expressing mutations conferring poor prognosis regardless of the expression of T cell-related inhibitory IC ligands. Overall, this study provides a rationale for a new potential basis for CRC stratification and NK cell-based therapy.

Antigen-specific primed cytotoxic T cells eliminate tumour cells in vivo and prevent tumour development, regardless of the presence of anti-apoptotic mutations conferring drug resistance

Cytotoxic CD8⁺ T (Tc) cells are the main executors of transformed and cancer cells during cancer immunotherapy. The latest clinical results evidence a high efficacy of novel immunotherapy agents that modulate Tc cell activity against bad prognosis cancers. However, it has not been determined yet whether the efficacy of these treatments can be affected by selection of tumoural cells with mutations in the cell death machinery, known to promote drug resistance and cancer recurrence. Here, using a model of prophylactic tumour vaccination based on the LCMV-gp33 antigen and the mouse EL4 T lymphoma, we analysed the molecular mechanism employed by Tc cells to eliminate cancer cells in vivo and the impact of mutations in the apoptotic machinery on tumour development. First of all, we found that Tc cells, and perf and gzmB are required to efficiently eliminate EL4.gp33 cells after LCMV immunisation during short-term assays (1-4 h), and to prevent tumour development in the long term. Furthermore, we show that antigen-pulsed chemoresistant EL4 cells overexpressing Bcl-X_L or a dominant negative form of caspase-3 are specifically eliminated from the peritoneum of infected animals, as fast as parental EL4 cells. Notably, antigen-specific Tc cells control the tumour growth of the mutated cells, as efficiently as in the case of parental cells. Altogether, expression of the anti-apoptotic mutations does not confer any advantage for tumour cells neither in the short-term survival nor in long-term tumour formation. Although the mechanism involved in the elimination of the apoptosis-resistant tumour cells is not completely elucidated, neither necroptosis nor pyroptosis seem to be involved. Our results provide the first experimental proof that chemoresistant cancer cells with mutations in the main cell death pathways are efficiently eliminated by Ag-specific Tc cells in vivo during immunotherapy and, thus, provide the molecular basis to treat chemoresistant cancer cells with CD8 Tc-based immunotherapy.

Granzyme A Contributes to Inflammatory Arthritis in Mice Through Stimulation of Osteoclastogenesis

OBJECTIVE

Granzyme A (GzmA) levels are elevated in the plasma and synovium of patients with rheumatoid arthritis (RA), suggesting involvement of this protease in the pathogenesis of the disease. GzmA contributes to sepsis by regulating the production of proinflammatory cytokines. The purpose of this study was to evaluate the contribution of GzmA to the pathogenesis of RA in vivo and to examine the possibility that GzmA acting via tumor necrosis factor (TNF) stimulates osteoclastogenesis.

METHODS

Inflammatory arthritis induced by type II collagen was evaluated in wild-type, GzmA-deficient, and perforin-deficient mice. The osteoclastogenic potential of GzmA was examined in vitro using bone marrow cells and colony-forming unit-granulocyte-macrophage (CFU-GM) cells and in vivo using GzmA-deficient mice.

RESULTS

Gene deletion of GzmA attenuated collagen-induced arthritis, including serum levels of proinflammatory cytokines, joint damage, and bone erosion in affected mice, suggesting that osteoclast activity is reduced in the absence of GzmA. Accordingly, GzmA-treated bone marrow cells produced multinucleated cells that fulfilled the criteria for mature osteoclasts: tartrate-resistant acid phosphatase (TRAP) activity, β integrin expression, calcitonin receptor expression, and resorptive activity on dentin slices. GzmA appeared to act without accessory cells, and its activity was not affected by osteoprotegerin, suggesting a minor contribution of RANKL. It also induced the expression and secretion of TNF. Neutralization of TNF or stimulation of CFU-GM cells from TNF^-/- mice prevented GzmA-induced osteoclastogenesis. GzmA-deficient mice had reduced osteoclastogenesis in vivo (fewer calcitonin receptor-positive multinucleated cells and fewer transcripts for cathepsin K, matrix metalloproteinase 9, and TRAP in joints) and reduced serum levels of C-terminal telopeptide of type I collagen.

CONCLUSION

GzmA contributes to the joint destruction of RA partly by promoting osteoclast differentiation.

Toll-Like Receptors 2 and 4 Cooperate in the Control of the Emerging Pathogen Brucella microti

Toll-like receptors (TLRs) recognize pathogen-derived molecules and play a critical role during the host innate and adaptive immune response. Brucella spp. are intracellular gram-negative bacteria including several virulent species, which cause a chronic zoonotic infection in a wide range of mammalian hosts known as brucellosis. A new Brucella species, Brucella microti, was recently isolated from wild rodents and found to be highly pathogenic in mice. Using this species-specific model, it was previously found that CD8⁺ T cells are required to control this infection. In order to find out the role of TLR-mediated responses in the control of this pathogen, the course of infection of B. microti was analyzed over 3 weeks in wild-type (WT) and TLR knock out (KO) mice including TLR2^-/-, TLR4^-/-, TLR9^-/-, TLR2×4^-/- and TLR2×4×9^-/-. WT and single TLR2, TLR4 and TLR9 KO mice similarly control infection in liver and spleen. In contrast, bacterial clearance was delayed in TLR2×4^-/- and TLR2×4×9^-/- mice at 7 and 14 days post-infection. This defect correlated with impaired maturation and pro-inflammatory cytokine production in B. microti-infected dendritic cells from TLR2×4^-/- and TLR2×4×9^-/- mice. Finally, it was found that Tc cells from TLR2×4^-/- and TLR2×4×9^-/- mice showed reduced ability to inhibit growth of B. microti in macrophages, suggesting the involvement of TLR2 and 4 in the generation of specific Tc cells. Our findings indicate that TLR2 and TLR4 are required to control B. microti infection in mice and that this effect could be related to its participation in the maturation of dendritic cells and the generation of specific CD8⁺ Tc cells.

Mouse cytotoxic T cell-derived granzyme B activates the mitochondrial cell death pathway in a Bim-dependent fashion

Cytotoxic T cells (Tc) use perforin and granzyme B (gzmB) to kill virus-infected cells and cancer cells. Recent evidence suggests that human gzmB primarily induces apoptosis via the intrinsic mitochondrial pathway by either cleaving Bid or activating Bim leading to the activation of Bak/Bax and subsequent generation of active caspase-3. In contrast, mouse gzmB is thought to predominantly induce apoptosis by directly processing pro-caspase-3. However, in certain mouse cell types gzmB-mediated apoptosis mainly occurs via the mitochondrial pathway. To investigate whether Bim is involved under the latter conditions, we have now employed ex vivo virus-immune mouse Tc that selectively kill by using perforin and gzmB (gzmB(+)Tc) as effector cells and wild type as well as Bim- or Bak/Bax-deficient spontaneously (3T9) or virus-(SV40) transformed mouse embryonic fibroblast cells as targets. We show that gzmB(+)Tc-mediated apoptosis (phosphatidylserine translocation, mitochondrial depolarization, cytochrome c release, and caspase-3 activation) was severely reduced in 3T9 cells lacking either Bim or both Bak and Bax. This outcome was related to the ability of Tc cells to induce the degradation of Mcl-1 and Bcl-XL, the anti-apoptotic counterparts of Bim. In contrast, gzmB(+)Tc-mediated apoptosis was not affected in SV40-transformed mouse embryonic fibroblast cells lacking Bak/Bax. The data provide evidence that Bim participates in mouse gzmB(+)Tc-mediated apoptosis of certain targets by activating the mitochondrial pathway and suggest that the mode of cell death depends on the target cell. Our results suggest that the various molecular events leading to transformation and/or immortalization of cells have an impact on their relative resistance to the multiple gzmB(+)Tc-induced death pathways.