N-glycosylation Regulates Intrinsic IFN-γ Resistance in Colorectal Cancer: Implications for Immunotherapy

BACKGROUND & AIMS

Advanced colorectal carcinoma (CRC) is characterized by a high frequency of primary immune evasion and refractoriness to immunotherapy. Given the importance of interferon (IFN)-γ in CRC immunosurveillance, we investigated whether and how acquired IFN-γ resistance in tumor cells would promote tumor growth, and whether IFN-γ sensitivity could be restored.

METHODS

Spontaneous and colitis-associated CRC development was induced in mice with a specific IFN-γ pathway inhibition in intestinal epithelial cells. The influence of IFN-γ pathway gene status and expression on survival was assessed in patients with CRC. The mechanisms underlying IFN-γ resistance were investigated in CRC cell lines.

RESULTS

The conditional knockout of the IFN-γ receptor in intestinal epithelial cells enhanced spontaneous and colitis-associated colon tumorigenesis in mice, and the loss of IFN-γ receptor α (IFNγRα) expression by tumor cells predicted poor prognosis in patients with CRC. IFNγRα expression was repressed in human CRC cells through changes in N-glycosylation, which decreased protein stability via proteasome-dependent degradation, inhibiting IFNγR-signaling. Downregulation of the bisecting N-acetylglucosaminyltransferase III (MGAT3) expression was associated with IFN-γ resistance in all IFN-γ-resistant cells, and highly correlated with low IFNγRα expression in CRC tissues. Both ectopic and pharmacological reconstitution of MGAT3 expression with all-trans retinoic acid increased bisecting N-glycosylation, as well as IFNγRα protein stability and signaling.

CONCLUSIONS

Together, our results demonstrated that tumor-associated changes in N-glycosylation destabilize IFNγRα, causing IFN-γ resistance in CRC. IFN-γ sensitivity could be reestablished through the increase in MGAT3 expression, notably via all-trans retinoic acid treatment, providing new prospects for the treatment of immune-resistant CRC.

Ketogenic Diet and Beta-Hydroxybutyrate in Colorectal Cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-related death in the United States. Although certain genetic predispositions may contribute to one's risk for developing CRC, dietary and lifestyle factors may play an important role as well. In a recent study in Nature, Dmitrieva-Posocco et al, reveal a potential protective role of the ketogenic diet in colorectal cancer growth and progression. Administration of a ketogenic diet to CRC-bearing mice demonstrated a tumor-suppressive effect. Specifically, the ketone body β-hydroxybutyrate (BHB) exhibited the ability to suppress epithelial cell proliferation and inhibit tumor growth. BHB acts on cancer cells through regulation of homeodomain-only protein Hopx, known regulator of CRC. Furthermore, BHB requires a surface receptor Hcar to induce Hopx expression and suppress proliferation of intestinal epithelial cells. Taken together, these results describe a new therapeutic approach of using dietary intervention for the prevention and treatment of colorectal cancer.

IL27 Signaling Serves as an Immunologic Checkpoint for Innate Cytotoxic Cells to Promote Hepatocellular Carcinoma

Although inflammatory mechanisms driving hepatocellular carcinoma (HCC) have been proposed, the regulators of anticancer immunity in HCC remain poorly understood. We found that IL27 receptor (IL27R) signaling promotes HCC development in vivo. High IL27EBI3 cytokine or IL27RA expression correlated with poor prognosis for patients with HCC. Loss of IL27R suppressed HCC in vivo in two different models of hepatocarcinogenesis. Mechanistically, IL27R sig-naling within the tumor microenvironment restrains the cytotoxicity of innate cytotoxic lymphocytes. IL27R ablation enhanced their accumulation and activation, whereas depletion or functional impairment of innate cytotoxic cells abrogated the effect of IL27R disruption. Pharmacologic neutralization of IL27 signaling increased infiltration of innate cytotoxic lymphocytes with upregulated cytotoxic molecules and reduced HCC development. Our data reveal an unexpected role of IL27R signaling as an immunologic checkpoint regulating innate cytotoxic lymphocytes and promoting HCC of different etiologies, thus indicating a therapeutic potential for IL27 pathway blockade in HCC.

SIGNIFICANCE

HCC, the most common form of liver cancer, is characterized by a poor survival rate and limited treatment options. The discovery of a novel IL27-dependent mechanism controlling anticancer cytotoxic immune response will pave the road for new treatment options for this devastating disease. This article is highlighted in the In This Issue feature, p. 1825.

β-Hydroxybutyrate suppresses colorectal cancer

Colorectal cancer (CRC) is among the most frequent forms of cancer, and new strategies for its prevention and therapy are urgently needed1. Here we identify a metabolite signalling pathway that provides actionable insights towards this goal. We perform a dietary screen in autochthonous animal models of CRC and find that ketogenic diets exhibit a strong tumour-inhibitory effect. These properties of ketogenic diets are recapitulated by the ketone body β-hydroxybutyrate (BHB), which reduces the proliferation of colonic crypt cells and potently suppresses intestinal tumour growth. We find that BHB acts through the surface receptor Hcar2 and induces the transcriptional regulator Hopx, thereby altering gene expression and inhibiting cell proliferation. Cancer organoid assays and single-cell RNA sequencing of biopsies from patients with CRC provide evidence that elevated BHB levels and active HOPX are associated with reduced intestinal epithelial proliferation in humans. This study thus identifies a BHB-triggered pathway regulating intestinal tumorigenesis and indicates that oral or systemic interventions with a single metabolite may complement current prevention and treatment strategies for CRC.

Abstract 5162: Role of IFN-gamma-activation of distinct tumor and stromal cell populations in colorectal carcinoma pathogenesis

Tumor and stromal cell plasticity induced by different tumor microenvironments (TMEs) has a significant impact on tumorigenesis of colorectal carcinoma (CRC). Specifically the role of the immunological TME has been investigated intensively. The prognosis of CRC is influenced by the density and localization of infiltrating T cells. Moreover, the presence of an mRNA expression profile indicative of a type 1 adaptive immune response (high IFN-γ and IFN-induced gene expression, cytotoxic T cell (CTL) signature) represents a positive prognostic factor for patients with CRC. IFN-γ is a major mediator of the Th1 immune response, which is produced by NK, NKT, Th1 cells and CTL. The role of IFN-γ in anti-tumor immune response has been mainly attributed to the immune-modulatory activity of the cytokine, such as the recruitment and activation of cytotoxic T-cells or monocytes. However, the expression of the IFN-γ receptor is ubiquitous and studies of IFN-γ-induced genes expression in CRC revealed that many different cell types are stimulated by the cytokine within a tumor, including tumor cells and stromal cells such as macrophages/monocytes and endothelial cells. In vitro, IFN-γ shows anti-tumorigenic activities in CRC cell lines, activates monocytes and exerts potent anti-angiogenic effects on endothelial cells. Here we investigated the cell-type-specific impact of the response to IFN-γ on CRC development using mouse strains with conditional knock-out of the IFN-γ receptor in intestinal epithelial cells (Villin-Cre), T-cells (CD4-Cre), myeloid cells (CD11b-Cre) and endothelial cells (Tie2-Cre + BMT). Tumor growth was chemically induced by injection of azoxymethane combined with three cycles of treatment with dextran-sodium sulfate. This model recapitulates inflammation-induced carcinogenesis. Our results revealed increased tumor numbers and load when the IFN-γ response was blocked in epithelial cells, despite an initial attenuation of inflammation. Tumors that developed in Ifngr2-Villin-Cre mice showed an attenuated IFN-γ response, and a decrease of CD8+ T cell infiltration, cell death and hypoxia. Abrogation of the IFN-γ-response in endothelial cells also fostered tumor growth, which could be attributed to an increase of angiogenesis. Surprisingly, only a modest effect was seen in the T-cell-specific knock-out, in comparison to the myeloid-specific knock-out, which was associated with a strong increase of tumor numbers and load. The latter indicated that the anti-tumorigenic activity mediated by IFN-γ relies to a larger extent on the innate than on the adaptive immune response. Our study documents that the anti-tumorigenic activity of IFN-γ is based on direct effects on epithelial tumor cells and on the vasculature, as well as on the involvement of the innate immune response.

Citation Format: Nathalie Britzen-Laurent, Wei Guo, Victoria Langer, Svetlana Khoziainova, Thomas Weisenburger, Thomas H. Winkler, Julia Straube, Maximilian J. Waldner, Christoph Becker, Elisabeth Naschberger, Lisa Skottke, Tripal Philipp, Sergei Grivennikov, Michael Stürzl. Role of IFN-gamma-activation of distinct tumor and stromal cell populations in colorectal carcinoma pathogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5162.