We examined the immune microenvironment of primary colorectal cancer using immunohistochemistry, laser capture microdissection/qRT-PCR, flow cytometry, and functional analysis of tumor-infiltrating ...lymphocytes. A subset of colorectal cancer displayed high infiltration with activated CD8(+) cytotoxic T lymphocyte (CTL) as well as activated Th1 cells characterized by IFNγ production and the Th1 transcription factor TBET. Parallel analysis of tumor genotypes revealed that virtually all of the tumors with this active Th1/CTL microenvironment had defects in mismatch repair, as evidenced by microsatellite instability (MSI). Counterbalancing this active Th1/CTL microenvironment, MSI tumors selectively demonstrated highly upregulated expression of multiple immune checkpoints, including five-PD-1, PD-L1, CTLA-4, LAG-3, and IDO-currently being targeted clinically with inhibitors. These findings link tumor genotype with the immune microenvironment, and explain why MSI tumors are not naturally eliminated despite a hostile Th1/CTL microenvironment. They further suggest that blockade of specific checkpoints may be selectively efficacious in the MSI subset of colorectal cancer.
The findings reported in this article are the first to demonstrate a link between a genetically defined subtype of cancer and its corresponding expression of immune checkpoints in the tumor microenvironment. The mismatch repair-defective subset of colorectal cancer selectively upregulates at least five checkpoint molecules that are targets of inhibitors currently being clinically tested.
Pro-carcinogenic bacteria have the potential to initiate and/or promote colon cancer, in part via immune mechanisms that are incompletely understood. Using ApcMin mice colonized with the ...human pathobiont enterotoxigenic Bacteroides fragilis (ETBF) as a model of microbe-induced colon tumorigenesis, we show that the Bacteroides fragilis toxin (BFT) triggers a pro-carcinogenic, multi-step inflammatory cascade requiring IL-17R, NF-κB, and Stat3 signaling in colonic epithelial cells (CECs). Although necessary, Stat3 activation in CECs is not sufficient to trigger ETBF colon tumorigenesis. Notably, IL-17-dependent NF-κB activation in CECs induces a proximal to distal mucosal gradient of C-X-C chemokines, including CXCL1, that mediates the recruitment of CXCR2-expressing polymorphonuclear immature myeloid cells with parallel onset of ETBF-mediated distal colon tumorigenesis. Thus, BFT induces a pro-carcinogenic signaling relay from the CEC to a mucosal Th17 response that results in selective NF-κB activation in distal colon CECs, which collectively triggers myeloid-cell-dependent distal colon tumorigenesis.
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•B. fragilis toxin-induced tumorigenesis requires epithelial IL17 and Stat3 signaling•IL17 targets colonic epithelial cells (CECs) to promote ETBF-mediated carcinogenesis•IL17-activated NF-κb signaling in CECs triggers C-X-C chemokine expression•NF-κB-induced chemokines direct pro-tumoral myeloid infiltration to distal colon
Chung et al. uncover a complex, microbe-driven carcinogenic mechanism whereby the Bacteroides fragilis toxin targets the colonic epithelium to trigger an IL-17 mucosal immune response that relays back to epithelial cells, inciting pro-tumoral myeloid cell infiltration, principally to the distal colon, corresponding to the region of tumorigenesis in ApcMin/− mice.
Many human cancers are dramatically accelerated by chronic inflammation. However, the specific cellular and molecular elements mediating this effect remain largely unknown. Using a murine model of ...pancreatic intraepithelial neoplasia (PanIN), we found that KrasG12D induces expression of functional IL-17 receptors on PanIN epithelial cells and also stimulates infiltration of the pancreatic stroma by IL-17-producing immune cells. Both effects are augmented by associated chronic pancreatitis, resulting in functional in vivo changes in PanIN epithelial gene expression. Forced IL-17 overexpression dramatically accelerates PanIN initiation and progression, while inhibition of IL-17 signaling using genetic or pharmacologic techniques effectively prevents PanIN formation. Together, these studies suggest that a hematopoietic-to-epithelial IL-17 signaling axis is a potent and requisite driver of PanIN formation.
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•IL-17+ T cells are recruited to the pancreas in response to Kras and inflammation•IL-17A overexpression accelerates PanIN initiation and progression•Inhibition of IL-17 signaling effectively prevents PanIN initiation and progression•Kras activates expression of functional IL-17 receptors on PanIN epithelium
McAllister et al. show that KrasG12D induces IL-17 receptors expression on PanIN epithelial cells and stimulates infiltration of IL-17-producing immune cells in a murine PanIN model, the latter of which is confirmed in human PanIN and that inhibition of IL-17 signaling prevents pancreatic neoplasia initiation.
Approximately 10% of patients with mismatch repair-proficient (MMRp) colorectal cancer showed clinical benefit to anti-PD-1 monotherapy (NCT01876511). We sought to identify biomarkers that delineate ...patients with immunoreactive colorectal cancer and to explore new combinatorial immunotherapy strategies that can impact MMRp colorectal cancer.
We compared the expression of 44 selected immune-related genes in the primary colon tumor of 19 patients with metastatic colorectal cancer (mCRC) who responded (
= 13) versus those who did not (
= 6) to anti-PD-1 therapy (NCT01876511). We define a 10 gene-based immune signature that could distinguish responder from nonresponder. Resected colon specimens (
= 14) were used to validate the association of the predicted status (responder and nonresponder) with the immune-related gene expression, the phenotype, and the function of tumor-infiltrating lymphocytes freshly isolated from the same tumors.
Although both IL17
and IL17
immunoreactive MMRp colorectal cancers are associated with intratumor correlates of adaptive immunosuppression (CD8/IFNγ and PD-L1/IDO1 colocalization), only IL17
MMRp tumors (3/14) have a tumor immune microenvironment (T
ME) that resembles the T
ME in primary colon tumors of patients with mCRC responsive to anti-PD-1 treatment.
The detection of a preexisting antitumor immune response in MMRp colorectal cancer (immunoreactive MMRp colorectal cancer) is not sufficient to predict a clinical benefit to T-cell checkpoint inhibitors. Intratumoral IL17-mediated signaling may preclude responses to immunotherapy. Drugs targeting the IL17 signaling pathway are available in clinic, and their combination with T-cell checkpoint inhibitors could improve colorectal cancer immunotherapy.
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Fusobacteria are commonly associated with human colorectal cancer (CRC), but investigations are hampered by the absence of a stably colonized murine model. Further, Fusobacterium nucleatum subspecies ...isolated from human CRC have not been investigated. While F. nucleatum subspecies are commonly associated with CRC, their ability to induce tumorigenesis and contributions to human CRC pathogenesis are uncertain. We sought to establish a stably colonized murine model and to understand the inflammatory potential and virulence genes of human CRC F. nucleatum, representing the 4 subspecies,
,
,
, and
. Five human CRC-derived and two non-CRC derived F. nucleatum strains were tested for colonization, tumorigenesis, and cytokine induction in specific-pathogen-free (SPF) and/or germfree (GF) wild-type and
mice, as well as
assays and whole-genome sequencing (WGS). SPF wild-type and
mice did not achieve stable colonization with F. nucleatum, whereas certain subspecies stably colonized some GF mice but without inducing colon tumorigenesis. F. nucleatum subspecies did not form
biofilms or associate with the mucosa in mice.
inflammation was inconsistent across subspecies, whereas F. nucleatum induced greater cytokine responses in a human colorectal cell line, HCT116. While F. nucleatum subspecies displayed genomic variability, no distinct virulence genes associated with human CRC strains were identified that could reliably distinguish these strains from non-CRC clinical isolates. We hypothesize that the lack of F. nucleatum-induced tumorigenesis in our model reflects differences in human and murine biology and/or a synergistic role for F. nucleatum in concert with other bacteria to promote carcinogenesis.
Colon cancer is a leading cause of cancer morbidity and mortality, and it is hypothesized that dysbiosis in the gut microbiota contributes to colon tumorigenesis. Fusobacterium nucleatum, a member of the oropharyngeal microbiome, is enriched in a subset of human colon tumors. However, it is unclear whether this genetically varied species directly promotes tumor formation, modulates mucosal immune responses, or merely colonizes the tumor microenvironment. Mechanistic studies to address these questions have been stymied by the lack of an animal model that does not rely on daily orogastric gavage. Using multiple murine models,
assays with a human colon cancer cell line, and whole-genome sequencing analysis, we investigated the proinflammatory and tumorigenic potential of several F. nucleatum clinical isolates. The significance of this research is development of a stable colonization model of F. nucleatum that does not require daily oral gavages in which we demonstrate that a diverse library of clinical isolates do not promote tumorigenesis.
Several predictive biomarkers are currently approved or are under investigation for the selection of patients for checkpoint blockade. Tumor PD-L1 expression is used for stratification of non-small ...cell lung (NSCLC) patients, with tumor mutational burden (TMB) also being explored with promising results, and mismatch-repair deficiency is approved for tumor site-agnostic disease. While tumors with high PD-L1 expression, high TMB, or mismatch repair deficiency respond well to checkpoint blockade, tumors with lower PD-L1 expression, lower mutational burdens, or mismatch repair proficiency respond much less frequently.
We studied two patients with unexpected responses to checkpoint blockade monotherapy: a patient with PD-L1-negative and low mutational burden NSCLC and one with mismatch repair proficient colorectal cancer (CRC), both of whom lack the biomarkers associated with response to checkpoint blockade, yet achieved durable clinical benefit. Both maintained T-cell responses in peripheral blood to oncogenic driver mutations - BRAF-N581I in the NSCLC and AKT1-E17K in the CRC - years after treatment initiation. Mutation-specific T cells were also found in the primary tumor and underwent dynamic perturbations in the periphery upon treatment.
These findings suggest that T cell responses to oncogenic driver mutations may be more prevalent than previously appreciated and could be harnessed in immunotherapeutic treatment, particularly for patients who lack the traditional biomarkers associated with response. Comprehensive studies are warranted to further delineate additional predictive biomarkers and populations of patients who may benefit from checkpoint blockade.
IFN-producing killer dendritic cells (IKDC) represent a recently discovered cell type in the immune system that possesses a number of functions contributing to innate and adaptive immunity, including ...production of type 1 and 2 IFNs, interleukin (IL)-12, natural killing, and ultimately antigen presentation to naïve T cells. Here, we compared in vitro and in vivo responses of mouse IKDC, conventional dendritic cells (DC), and natural killer (NK) cells to murine cytomegalovirus infection and found distinct functions among these cell subsets. Upon recognition of infected fibroblasts, IKDC, as well as NK, produced high level of IFN-gamma, but unlike NK, IKDC simultaneously produced IL-12p40 and up-regulated MHC class II (MHC-II) and costimulatory molecules. Using MHC-II molecule expression as a phenotypic marker to distinguish activated IKDC from activated NK, we further showed that highly purified MHC-II(+) IKDC but not NK cross-present MHC class I-restricted antigens derived from MCMV-infected targets to CD8(+) T cells in vitro and in vivo. Our findings emphasize the unique nature of IKDC as a killer antigen-presenting cell directly linking innate and adaptive immunity.
Immune-mediated tissue regeneration driven by a biomaterial scaffold is emerging as an innovative regenerative strategy to repair damaged tissues. We investigated how biomaterial scaffolds shape the ...immune microenvironment in traumatic muscle wounds to improve tissue regeneration. The scaffolds induced a pro-regenerative response, characterized by an mTOR/Rictor-dependent T helper 2 pathway that guides interleukin-4–dependent macrophage polarization, which is critical for functional muscle recovery. Manipulating the adaptive immune system using biomaterials engineering may support the development of therapies that promote both systemic and local pro-regenerative immune responses, ultimately stimulating tissue repair.
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