Inhibition of integrin αvβ6 sparks T-cell antitumor response and enhances immune checkpoint blockade therapy in colorectal cancer

Background

Integrin αvβ6 is a heterodimeric cell surface protein whose cellular expression is determined by the availability of the integrin β6 subunit (ITGB6). It is expressed at very low levels in most organs during tissue homeostasis but shows highly upregulated expression during the process of tumorigenesis in many cancers of epithelial origin. Notably, enhanced expression of integrin αvβ6 is associated with aggressive disease and poor prognosis in numerous carcinoma entities. Integrin αvβ6 is one of the major physiological activators of transforming growth factor-β (TGF-β), which has been shown to inhibit the antitumor T-cell response and cause resistance to immunotherapy in mouse models of colorectal and mammary cancer. In this study, we investigated the effect of ITGB6 expression and antibody-mediated integrin αvβ6 inhibition on the tumor immune response in colorectal cancer.

Methods

Using orthotopic and heterotopic tumor cell injection, we assessed the effect of ITGB6 on tumor growth and tumor immune response in wild type mice, mice with defective TGF-β signaling, and mice treated with anti-integrin αvβ6 antibodies. To examine the effect of ITGB6 in human colorectal cancer, we analyzed RNAseq data from the colon adenocarcinoma dataset of The Cancer Genome Atlas (TCGA-COAD).

Results

We demonstrate that expression of ITGB6 is an immune evasion strategy in colorectal cancer, causing inhibition of the antitumor immune response and resistance to immune checkpoint blockade therapy by activating latent TGF-β. Antibody-mediated inhibition of integrin αvβ6 sparked a potent cytotoxic T-cell response and overcame resistance to programmed cell death protein 1 (PD-1) blockade therapy in ITGB6 expressing tumors, provoking a drastic increase in anti-PD-1 treatment efficacy. Further, we show that the majority of tumors in patients with colorectal cancer express sufficient ITGB6 to provoke inhibition of the cytotoxic T-cell response, indicating that most patients could benefit from integrin αvβ6 blockade therapy.

Conclusions

These findings propose inhibition of integrin αvβ6 as a promising new therapy for colorectal cancer, which blocks tumor-promoting TGF-β activation, prevents tumor exclusion of cytotoxic T-cells and enhances the efficacy of immune checkpoint blockade therapy.

Abstract 2821: Gut commensal bacteria modulate functions of tumor-associated neutrophils in human colorectal cancer

Tumor infiltration by immune cells critically impacts on clinical outcome of human colorectal cancer (CRC). While high densities of CD8+ T cells and T-helper type 1 cells are associated with prolonged patient survival, the role of tumor-associated neutrophils (TANs) is debated.

CRC arise in an environment heavily populated by microrganisms. Upon CRC oncogenesis, gut commensal bacteria translocate into the submucosa where they directly interact with residing immune cells. Neutrophils represent a front-line arm of the immune system in the response to bacteria. However, little is known about their interaction with commensal bacteria within CRC tissues. We investigated the interplay between neutrophils and commensal bacterial species present within the CRC microenvironment.

Using an orthotopic CRC xenograft model, we found that commensal bacteria stimulate CRC cells to produce neutrophil recruiting chemokines. We then compared in vitro chemokine induction capacity of Fusobacterium nucleatum (Fn) and Bacteroides fragilis (Bf), two most abundant bacterial species of CRC microenvironment. Fninduced significantly higher levels of IL-8 by CRC cells than Bf, thus more effectively promoting neutrophil recruitment. Accordingly, in human CRC samples, abundance of Fn, but not Bf, significantly correlated with high infiltration by CD66b+ cells. Functional studies indicate that neutrophils cultured in the presence of Fn, but not Bf, lose their ability to enhance proliferation and cytokine release by CD8+ T cells undergoing antigenic stimulation. Moreover, neutrophils exposed to Fn, but not Bf, stimulate release of IL-6 by tumor-associated stromal cells, leading to enhanced tumor cell proliferation.

Our data cumulatively suggest that distinct bacterial components of the human gut flora might differentially modulate functions of CRC infiltrating neutrophils, thus ultimately influencing their prognostic significance.

Note: This abstract was not presented at the meeting.

Citation Format: Valeria Governa, Eleonora Cremonesi, Diego Calabrese, Valentina Mele, Emanuele Trella, Raoul A. Droeser, Martin Bolli, Serenella Eppenberger-Castori, Salvatore Piscuoglio, Charlotte K. y. Ng, Jesus Francisco Glaus Garzon, Lubor Borsig, Klaus-Peter Janssen, Luigi M. Terracciano, Giulio Cesare Spagnoli, Dimitri Christoforidis, Pietro Edoardo Majno-Hurst, Giandomenica Iezzi. Gut commensal bacteria modulate functions of tumor-associated neutrophils in human colorectal cancer [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 2821.

Alleviation of Intestinal Inflammation by Oral Supplementation With 2-Fucosyllactose in Mice

Milk oligosaccharides exert a prebiotic action that contributes to the development of the infant gut microbiota during lactation. Given that milk oligosaccharides remain intact after passage through stomach and small intestine, they can potentially influence the composition of the gut microbiota when ingested as dietary supplements after weaning. To address the regulatory effects of specific oligosaccharides in colitis linked to the microbiota composition, we have supplemented interleukin-10 null (Il10 ^-/-) mice with four fucosylated and sialylated oligosaccharides. We found that oral supplementation with 2-fucosyllactose significantly decreased the severity of colitis as displayed by reduced inflammatory marker expression, histological and diarrhea scores, an increased epithelial integrity and less pronounced colon shortening. Oral supplementation with 2-fucosyllactose led to a marked expansion of the commensal Ruminococcus gnavus, which was accompanied by an enhanced cecal concentration of propionate. Decreased activation of immune cells by R. gnavus was confirmed by reconstitution of antibiotic-treated Il10 ^-/- mice and by stimulation of dendritic cells in vitro. This study demonstrates that post-weaning administration of specific oligosaccharides can shift the composition of the gut microbiota to lessen chronic inflammation as observed in Il10 ^-/- mice. The expansion of R. gnavus sets a positive microbial environment at the cost of pro-inflammatory Gram-negative bacteria, thereby lowering intestinal inflammation.

Gut microbiota modulate T cell trafficking into human colorectal cancer

OBJECTIVE

Tumour-infiltrating lymphocytes (TILs) favour survival in human colorectal cancer (CRC). Chemotactic factors underlying their recruitment remain undefined. We investigated chemokines attracting T cells into human CRCs, their cellular sources and microenvironmental triggers.

DESIGN

Expression of genes encoding immune cell markers, chemokines and bacterial 16S ribosomal RNA (16SrRNA) was assessed by quantitative reverse transcription-PCR in fresh CRC samples and corresponding tumour-free tissues. Chemokine receptor expression on TILs was evaluated by flow cytometry on cell suspensions from digested tissues. Chemokine production by CRC cells was evaluated in vitro and in vivo, on generation of intraperitoneal or intracecal tumour xenografts in immune-deficient mice. T cell trafficking was assessed on adoptive transfer of human TILs into tumour-bearing mice. Gut flora composition was analysed by 16SrRNA sequencing.

RESULTS

CRC infiltration by distinct T cell subsets was associated with defined chemokine gene signatures, including CCL5, CXCL9 and CXCL10 for cytotoxic T lymphocytes and T-helper (Th)1 cells; CCL17, CCL22 and CXCL12 for Th1 and regulatory T cells; CXCL13 for follicular Th cells; and CCL20 and CCL17 for interleukin (IL)-17-producing Th cells. These chemokines were expressed by tumour cells on exposure to gut bacteria in vitro and in vivo. Their expression was significantly higher in intracecal than in intraperitoneal xenografts and was dramatically reduced by antibiotic treatment of tumour-bearing mice. In clinical samples, abundance of defined bacteria correlated with high chemokine expression, enhanced T cell infiltration and improved survival.

CONCLUSIONS

Gut microbiota stimulate chemokine production by CRC cells, thus favouring recruitment of beneficial T cells into tumour tissues.

Abstract A123: Modulation of immune cell trafficking into human colorectal cancer by gut microbiota

Colorectal cancer (CRC) is a leading cause of cancer-related death. CRC infiltration by immune cells, including cytotoxic CD8+ T cells (CTLs), IFN-gamma-producing T-helper 1 cells (Th1), Foxp3+ regulatory T cells (Tregs) and CD16+ MPO+ neutrophils, is associated with favorable prognosis. However, chemokines driving these cell populations into the tumor site, their cellular sources and their microenvironmental triggers remain to be elucidated. We investigated the chemokine/chemokine receptor network promoting CRC infiltration by immune cells associated to favorable prognosis. Analysis of freshly excised specimens of CRC and adjacent healthy colonic tissues revealed that tumor infiltration by beneficial immune cells is associated with the expression of four main chemokine patterns: 1) CCL3, CCL5, CCL8, CXCL9, CXCL10, and CXCL12 for CTLs; 2) CCL5, CCL22, CXCL9 and CXCL12 correlating with CRC infiltration by Th1; 3) CCL22 and CXCL12 attracting Tregs; 4) CXCL2 and CXCL5, promoting chemotaxis of CD16+ MPO+ myeloid cells. Most of identified chemokines were found to be expressed, although at different levels, in primary CRC cells purified from tumor specimens and from xenografts generated upon injection of CRC cells in immunodeficient mice. Notably, chemokine expression levels in orthotopic xenografts, developed upon intracecal injection of tumor cells, were significantly higher as compared to those of subcutaneous tumors. Antibiotic treatment of tumor bearing mice drastically reduced chemokine expression in orthotopic xenografts, thus suggesting a role for commensal bacteria in chemokines induction in tumor cells. Importantly, human CRC samples characterized by high expression of chemokine and immune cell markers, displayed significantly higher bacterial loads, as compared to samples showing low chemokine expression and immune cell infiltration. Furthermore, bacterial loads significantly correlated with expression of CCL3 and CCL5, and Th1 infiltration. These data suggest that stimuli derived from gut flora components may trigger chemokine production in CRC tissues thus leading to tumor infiltration by beneficial immune cells.

Note: This abstract was not presented at the conference.

Citation Format: Eleonora Cremonesi, Francesca Amicarella, Jesus Francisco Glaus Garzon, Valeria Governa, Manuele Giuseppe Muraro, Valentina Mele, Elisabetta Padovan, Daniel Oertli, Paul Zajac, Giulio Cesare Spagnoli, Lubor Borsig, Giandomenica Iezzi. Modulation of immune cell trafficking into human colorectal cancer by gut microbiota [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A123.