Here, we show that autophagy is activated in the intestinal epithelium in murine and human colorectal cancer and that the conditional inactivation of Atg7 in intestinal epithelial cells inhibits the formation of pre-cancerous lesions in Apc(+/-) mice by enhancing anti-tumour responses. The antibody-mediated depletion of CD8(+) T cells showed that these cells are essential for the anti-tumoral responses mediated by the inhibition of autophagy. We show that Atg7 deficiency leads to intestinal dysbiosis and that the microbiota is required for anticancer responses. In addition, Atg7 deficiency resulted in a stress response accompanied by metabolic defects, AMPK activation and p53-mediated cell-cycle arrest in tumour cells but not in normal tissue. This study reveals that the inhibition of autophagy within the epithelium may prevent the development and progression of colorectal cancer in genetically predisposed patients.
The intestinal epithelium acts as a barrier between the organism and its microenvironment, including the gut microbiota. It is the most rapidly regenerating tissue in the human body thanks to a pool of intestinal stem cells (ISCs) expressing Lgr5. The intestinal epithelium has to cope with continuous stress linked to its digestive and barrier functions. Epithelial repair is crucial to maintain its integrity, and Lgr5-positive intestinal stem cell (Lgr5+ISC) resilience following cytotoxic stresses is central to this repair stage. We show here that autophagy, a pathway allowing the lysosomal degradation of intracellular components, plays a crucial role in the maintenance and genetic integrity of Lgr5+ISC under physiological and stress conditions. Using conditional mice models lacking the autophagy gene Atg7 specifically in all intestinal epithelial cells or in Lgr5+ISC, we show that loss of Atg7 induces the p53-mediated apoptosis of Lgr5+ISC. Mechanistically, this is due to increasing oxidative stress, alterations to interactions with the microbiota, and defective DNA repair. Following irradiation, we show that Lgr5+ISC repair DNA damage more efficiently than their progenitors and that this protection is Atg7 dependent. Accordingly, we found that the stimulation of autophagy on fasting protects Lgr5+ISC against DNA damage and cell death mediated by oxaliplatin and doxorubicin treatments. Finally, p53 deletion prevents the death of Atg7-deficient Lgr5+ISC but promotes genetic instability and tumor formation. Altogether, our findings provide insights into the mechanisms underlying maintenance and integrity of ISC and highlight the key functions of Atg7 and p53.
T lymphocyte migration is an essential step to mounting an efficient immune response. The rapid and random motility of these cells which favors their sentinel role is conditioned by chemokines as well as by the physical environment. Morphological changes, underlaid by dynamic actin cytoskeleton remodeling, are observed throughout migration but especially when the cell modifies its trajectory. However, the signaling cascade regulating the directional changes remains largely unknown. Using dynamic cell imaging, we investigated in this paper the signaling pathways involved in T cell directionality. We monitored cyclic adenosine 3′-5′ monosphosphate (cAMP) variation concomitantly with actomyosin distribution upon T lymphocyte migration and highlighted the fact that spontaneous bursts in cAMP starting from the leading edge, are sufficient to promote actomyosin redistribution triggering trajectory modification. Although cAMP is commonly considered as an immunosuppressive factor, our results suggest that, when transient, it rather favors the exploratory behavior of T cells.
Background: Mucosal-Associated Invariant T cells (MAITs) are an abundant subset of non-conventional T-cells with potent cytotoxic capacity (up to 20% of circulating T-cells) that are naturally resident in many tissues and solid tumors. T-cell redirection is a clinically validated approach to treating haematological cancers but has limited success in solid tumors. Classical T-cell engagers (TCE) bind the epsilon chain of the TCR leading to activation of all T-cells. MAIT cells utilize a semi-invariant TCR and recognize bacterial metabolites presented in the context of the MR1 protein. Biomunex has generated bispecific antibodies that bind the MAIT semi-invariant TCR (iTCR) and the HER2 receptor tyrosine kinase expressed on tumor cells. This enables the formation of an efficient immunological synapse and exclusive redirection of MAIT cells to directly kill cancer cells. Methods: Using the Biomunex proprietary BiXAb® platform, bispecific, tetravalent antibodies were generated that target the MAIT iTCR and HER2. Specific binding to the two targets was demonstrated by ELISA, DUAL ELISA and in FACS. In general, BiXAb®-mediated MAIT-cell activation, proliferation and degranulation were followed by gating on MAIT cells within a purified CD8 cell population. Tumor cell lines expressing varying amounts of HER2 were co-cultured with MAIT cells (peripheral and tumor-resident) and the BiXAb®s in several cytotoxic assays which were evaluated by measuring Chromium release, LDH release and FACS. Results: The iTCR x HER2 BiXAb® efficiently binds both target proteins with similar affinities to the parental Mabs and can bind both simultaneously, as judged by Dual ELISA. The iTCR x HER2 BiXAb® binds the MAIT-cell TCR and can bind cancer cells over a wide range of HER2 expression. BiXAb® engagement of MAIT cells and cancer cells leads to rapid activation, proliferation and degranulation of MAIT cells. In a population of PBMCs, only MAIT cells are activated by the BiXAb®. Even at low effector to target ratios (E:T = 2:1), MAIT cells efficiently kill engaged cancer cells in a HER2-dependent manner (over 50% cytotoxicity in 18 hrs). The MAIT-directed BiXAb® does not activate other T-cell subsets and hence has significantly reduced cytokine release when compared to a classical T-cell engager. Conclusions: BiXAb® mediated MAIT cell redirection leads to efficient killing of cancer cells and is a promising new approach for the treatment of solid tumors. The iTCR x HER2 BiXAb® has no impact on the general CD8 or CD4 T-cell population which may address some of the clinical limitations of classical TCEs. Citation Format: Simon Edward Plyte, Marie Fraudeau, Jonathan Grivel, Paloma Hougron, Katja Klausz, Dorothee Winterberg, Britta von Below, Alexandre Ivagnes, Claire Germain, Sebastian Amigorena, Eugene Zhukovsky, Matthias Peipp, Pierre-Emmanuel Gerard, Olivier Lantz, Julie Prigent. MAIT engagers: An efficacious novel modality in the field of T-cell engagers for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2954.
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