洞观免疫：肿瘤免疫Hallmark，一篇157个引文的综述

Immunotherapy is revolutionizing the clinical management of multiple tumors. However, only a fraction of patients with cancer respond to immunotherapy, and currently available immunotherapeutic agents are expensive and generally associated with considerable toxicity, calling for the identification of robust predictive biomarkers.

The overall genomic configuration of malignant cells, potentially favoring the emergence of immunogenic tumor neoantigens, as well as specific mutations that compromise the ability of the immune system to recognize or eradicate the disease have been associated with differential sensitivity to immunotherapy in preclinical and clinical settings. Along similar lines, the type, density, localization, and functional orientation of the immune infiltrate have a prominent impact on anticancer immunity, as do features of the tumor microenvironment linked to the vasculature and stroma, and systemic factors including the composition of the gut microbiota. By these considerations, we outline the hallmarks of successful anticancer immunotherapy.

The success of anticancer immunotherapy depends to a large degree

on the features of cancer cells that determine

(i)Immunogenicity: their intrinsic potential to initiate a tumor-targeting immune response,  (ii)Immunosuppression: their ability to establish an immunosuppressive tumor microenvironment (TME),

(iii) Susceptibility: their sensitivity to immune effector mechanisms (Fig. 1).

L. Galluzzi, A. Buqué, O. Kepp, L. Zitvogel, G. Kroemer, Immunogenic cell death in cancer and infectious disease. Nat. Rev. Immunol. 17, 97–111 (2017)

Depiction of tumor cells dying as a result of genomically targeted therapies with release of tumor antigens; tumor antigens are taken up by APCs and are presented in the context of B7 costimulatory molecules to T cells; T cells recognize antigens on APCs to become activated; activated T cells also upregulate inhibitory checkpoints such as CTLA-4 and PD-1; immune checkpoint therapy prevents attenuation of T cell responses, thereby allowing T cells to kill tumor cells; and T cells may differentiate into memory T cells that can reactivate in the presence of recurrent tumor.

P. Sharma, J. P. Allison, Immune checkpoint targeting in cancer therapy: Toward combination strategies with curative potential. Cell 161, 205–214 (2015)

cancer cells and lymphocytes engage in a metabolic competition that influences the overall immunological status of the TME (and hence the likelihood for efficient anticancer immune responses)

C. H. Chang, J. Qiu, D. O’Sullivan, M. D. Buck, T. Noguchi, J. D. Curtis, Q. Chen, M. Gindin, M. M. Gubin, G. J. van der Windt, E. Tonc, R. D. Schreiber, E. J. Pearce, E. L. Pearce, Metabolic competition in the tumor microenvironment is a driver of cancer progression. Cell 162, 1229–1241 (2015).

genetic and epigenetic alterations affecting the interferon gamma receptor (IFNGR) signaling pathway in malignant cells, including (but not limited to) JAK1, JAK2, and APLNR mutations, have been associated with resistance to ICB in a variety of preclinical and clinical settings

Maximal heterozygosity at HLA-I loci (A, B, and C) improved overall survival after ICB compared to patients who were homozygous for at least one HLA locus. In two independent melanoma cohorts, patients with the HLA-B44 supertype had extended survival, whereas the HLA-B62 supertype (including HLA-B*15:01) or somatic LOH at HLA-I, was associated with poor outcome. Molecular dynamics simulations of HLA-B*15:01 revealed unique elements that may impair CD8 T cell recognition of neoantigens.

D. Chowell, L. G. T. Morris, C. M. Grigg, J. K. Weber, R. M. Samstein, V. Makarov, F. Kuo, S. M. Kendall, D. Requena, N. Riaz, B. Greenbaum, J. Carroll, E. Garon, D. M. Hyman, A. Zehir, D. Solit, M. Berger, R. Zhou, N. A. Rizvi, T. A. Chan, Patient HLA class I genotype influences cancer response to checkpoint blockade immunotherapy. Science 359, 582–587 (2018)

Three aspects of the immunological tumor infiltrate have a major impact on the success of anticancer immunotherapy (and several forms of conventional therapy): (i) composition, (ii) localization, and (iii) functionality (Fig. 2)

Three interrelated but conceptually distinct aspects of the immunological tumor infiltrate determine the likelihood of cancer patients to respond to immunotherapy:

(i)the relative abundance of effector versus suppressor cells (left),  (ii) the localization of immune cells concerning their malignant counterparts (middle)  (iii) the activation status of immune effectors (right) 

Tumor-infiltrating CD8 T cells, T helper 1 (TH1)–polarized CD4 T cells, and CD103 DCs are widely considered to be central players in the initiation and execution of anticancer immune responses driven by multiple (immuno)therapeutic agents.

Thus, high intratumoral amounts of these cells have been consistently associated with improved disease outcome (66). Conversely, extensive tumor infiltration by CD4 CD25 FOXP3 regulatory T (Treg) cells or M2-polarized macrophages, both of which mediate robust immunosuppressive effects, has generally been linked with limited sensitivity to a variety of (immuno)therapeutic regimens (66).

the relative abundance of intratumoral CD8 T cells over Treg cells often conveys improved informative value as compared to the abundance of each population taken individually

W. H. Fridman, L. Zitvogel, C. Sautès­Fridman, G. Kroemer, The immune contexture in cancer prognosis and treatment. Nat. Rev. Clin. Oncol. 14, 717–734 (2017)

Exposure of nonmalignant tissue to a variety of stressors leads to infiltration by inflammatory cells, most of which are innate immune effectors. Chronic inflammation can promote the development of precancerous lesions, which are often held in check by local immune effectors. The transition to a fully malignant phenotype is characterized by a change in the infiltrate that is dominated by immunosuppressive cell types, such as macrophages of the M2 phenotype, myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Treg). The metastatic spread of malignant cells occurs in the context of a further deterioration in local immune control. However, central memory lymphocytes educated against cancer neoantigens in tertiary lymphoid structures (TLSs) might control a primary tumor, and these cells can also circulate and mediate the immunosurveillance of individual metastases. DC, dendritic cell.

the so-called immune-excluded phenotype, in which high levels of T cells and other immune cells accumulate at the tumor margin but cannot invade malignant cell nests, is generally linked to poor disease outcome, as compared to the “inflamed” or “hot” phenotype, in which intratumoral immune cells are abundant and get into direct apposition with neoplastic cells.

 D. S. Chen, I. Mellman, Elements of cancer immunity and the cancer­immune set point. Nature 541, 321–330 (2017)

 This approach has raised great expectations as a possible means to quantitatively, spatially, and qualitatively characterize the cancer immune infiltrate in the same sample at improved resolution. It will be interesting to see whether such expectations will be met and imaging mass cytometry will eventually replace immunohistochemistry in this setting.

C. Giesen, H. A. O. Wang, D. Schapiro, N. Zivanovic, A. Jacobs, B. Hattendorf, P. J. Schüffler, D. Grolimund, J. M. Buhmann, S. Brandt, Z. Varga, P. J. Wild, D. Gunther, B. Bodenmiller, Highly multiplexed imaging of tumor tissues with a subcellular resolution by mass cytometry. Nat. Methods 11, 417–422 (2014) 

The tumor stroma and vasculature are less investigated than tumor-infiltrating immune cells for their role in tumor-targeting immune responses. However, accumulating evidence suggests that these two nonmalignant components of the TME can have a considerable impact on the success of anticancer immunotherapy.

 The tumor endothelium expresses FAS ligand (FASL) downstream of vascular endothelial growth factor A (VEGFA) and prostaglandin E2 (PGE2) signaling(1), hence favoring the preferential extravasation of CD4 CD25 FOXP3 Treg cells (2) as a consequence of cytotoxic T lymphocyte (CTL) elimination.

Cadherin 5 (CDH5) also contributes to the limited permeability of the tumor endothelium to immune effector cells (3). CD4 TH1 cells secreting IFN­g appear to participate in a bidirectional cross­talk with the tumor endothelium, resulting in vascular normalization and immune cell reprogramming (4).

Cancer­associated fibroblasts (CAFs) secrete high amounts of TGF­ β (5), resulting in the establishment of a dense stromal reaction commonly known as desmoplastic stroma. Protein tyrosine kinase 2(PTK2; best known as FAK) activation in malignant cells and CAFs have been involved in this process (6).

 However, although TGF­ β is involved in immune exclusion, the actual impact of the desmoplastic stroma on anticancer immunity remains to be clarified. CAFs can also delete tumor­targeting T cells via a contact­dependent mechanism involving Fas ligand (FASL) and programmed cell death 1 ligand 2 (PDCD1LG2; another PD­1 ligand best known as PD­L2; 7) and secrete matrix metalloproteinases (MMPs) that generate soluble NK cell­activating receptor (sNCAR) ligands (8).

 Hypoxia, lactate accumulation, and (at least in some tumors) the local microbiota also contribute to immunosuppression via a variety of mechanisms (9).

 The likelihood of cancer patients to obtain clinical benefits from immunotherapy depends on their global immunological competence, which can be influenced by cancer­ and treatment ­unrelated factors including variations in genes involved in the elicitation, regulation, and execution of tumor ­targeting immunity; by viral infections or pharmacological agents resulting in systemic immunosuppression; and by the composition of the gut microbiota. In addition, developing tumors (and some forms of treatment) can change the systemic immunological microenvironment by favoring the generation of immature myeloid cells with immunosuppressive activity, by altering the gut microbiome (dysbiosis), and by releasing cytokines and other factors that quench anticancer immune responses. Many of these changes are instrumental for tumors to resist to treatment, hence constituting promising targets for the development of novel therapeutic interventions. These and other circulating factors including indicators of the functional competence of immune effector cells may be harnessed as biomarkers to assist clinical decision­ making.

it is now clear that the composition of the gut microbiome has a major impact not only on intestinal tumorigenesis but also on the susceptibility of extraintestinal tumors to chemo- and immunotherapy.

L. Zitvogel, L. Galluzzi, S. Viaud, M. Vétizou, R. Daillere, M. Merad, G. Kroemer, Cancer, and the gut microbiota: An unexpected link. Sci. Transl. Med. 7, 271ps1 (2015)

Fecal microbiota transplantation (FMT) from cancer patients who responded to ICIs into germ-free or antibiotic-treated mice ameliorated the antitumor effects of the PD-1 blockade, whereas FMT from nonresponding patients failed to do so. Metagenomics of patient stool samples at diagnosis revealed correlations between clinical responses to ICIs and the relative abundance of Akkermansia muciniphila. Oral supplementation with A. muciniphila after FMT with non-responder feces restored the efficacy of PD-1 blockade in an interleukin-12– dependent manner by increasing the recruitment of CCR9 CXCR3 CD4 T lymphocytes into mouse tumor beds.

L. Zitvogel, Y. Ma, D. Raoult, G. Kroemer, T. F. Gajewski, The microbiome in cancer immunotherapy: Diagnostic tools and therapeutic strategies. Science 359, 1366–1370 (2018).
Fig. 1. The microbiome at the crossroads between physiology and pathology in cancer. The intestinal microbiota plays a crucial role in the life-long programming of innate and acquired immune responses because it fine-tunes the delicate balance between inflammation, infection, and tolerance of food and commensal antigens. Several therapeutic modalities could be harnessed to restore the homeostasis of the gut and the metaorganism during cancer progression and treatment.

1.Need to investigate genetic, epigenetic, and immunological heterogeneity. Sampling the TME at multiple locations and ideally at multiple time points in the course of treatment might enable an improved characterization of malignant lesions concerning both heterogeneity and evolutionary behavior, and hence provide superior feedback to clinicians.

2.It will be crucial to investigate in detail how such processes, which includebioenergetic metabolism, autophagy, cellular senescence, and immunomodulation, operate in the stroma, endothelium, and immune infiltrate and how these compartments are connected together in the regulation of antitumor immunity.

3. Although immunohistochemical tests can partially circumvent such issues for intracellular or membrane-bound proteins, the actual abundance of secreted factors in the TME remains challenging to be tested.

4 .To develop safe and efficient combinatorial regimens, it will be critical to delve deeper into how conventional therapeutic approaches (that is, surgery, chemotherapy, radiation therapy, and targeted therapy)  influence the efficacy of immunotherapy .

5. Finally, the impact of the gut microbiome on the efficacy of multiple forms of treatment, including immunotherapy, has just begun to emerge. By the robust preclinical and clinical findings of the last few years, this aspect of anticancer immune responses deserves additional attention (157). It is therefore imperative not only to monitor the microbiome of patients enrolled in clinical trials but also to define harmonized procedures for preclinical investigation.