p21 Prevents the Exhaustion of CD4+ T Cells Within the Antitumor Immune Response Against Colorectal Cancer

BACKGROUND & AIMS

T cells are crucial for the antitumor response against colorectal cancer (CRC). T-cell reactivity to CRC is nevertheless limited by T-cell exhaustion. However, molecular mechanisms regulating T-cell exhaustion are only poorly understood.

METHODS

We investigated the functional role of cyclin-dependent kinase 1a (Cdkn1a or p21) in cluster of differentiation (CD) 4+ T cells using murine CRC models. Furthermore, we evaluated the expression of p21 in patients with stage I to IV CRC. In vitro coculture models were used to understand the effector function of p21-deficient CD4+ T cells.

RESULTS

We observed that the activation of cell cycle regulator p21 is crucial for CD4+ T-cell cytotoxic function and that p21 deficiency in type 1 helper T cells (Th1) leads to increased tumor growth in murine CRC. Similarly, low p21 expression in CD4+ T cells infiltrated into tumors of CRC patients is associated with reduced cancer-related survival. In mouse models of CRC, p21-deficient Th1 cells show signs of exhaustion, where an accumulation of effector/effector memory T cells and CD27/CD28 loss are predominant. Immune reconstitution of tumor-bearing Rag1-/- mice using ex vivo-treated p21-deficient T cells with palbociclib, an inhibitor of cyclin-dependent kinase 4/6, restored cytotoxic function and prevented exhaustion of p21-deficient CD4+ T cells as a possible concept for future immunotherapy of human disease.

CONCLUSIONS

Our data reveal the importance of p21 in controlling the cell cycle and preventing exhaustion of Th1 cells. Furthermore, we unveil the therapeutic potential of cyclin-dependent kinase inhibitors such as palbociclib to reduce T-cell exhaustion for future treatment of patients with colorectal cancer.

Polyol Pathway Links Glucose Metabolism to the Aggressiveness of Cancer Cells

Cancer cells alter their metabolism to support their malignant properties. In this study, we report that the glucose-transforming polyol pathway (PP) gene aldo-keto-reductase-1-member-B1 (AKR1B1) strongly correlates with epithelial-to-mesenchymal transition (EMT). This association was confirmed in samples from lung cancer patients and from an EMT-driven colon cancer mouse model with p53 deletion. In vitro, mesenchymal-like cancer cells showed increased AKR1B1 levels, and AKR1B1 knockdown was sufficient to revert EMT. An equivalent level of EMT suppression was measured by targeting the downstream enzyme sorbitol-dehydrogenase (SORD), further pointing at the involvement of the PP. Comparative RNA sequencing confirmed a profound alteration of EMT in PP-deficient cells, revealing a strong repression of TGFβ signature genes. Excess glucose was found to promote EMT through autocrine TGFβ stimulation, while PP-deficient cells were refractory to glucose-induced EMT. These data show that PP represents a molecular link between glucose metabolism, cancer differentiation, and aggressiveness, and may serve as a novel therapeutic target.Significance: A glucose-transforming pathway in TGFβ-driven epithelial-to-mesenchymal transition provides novel mechanistic insights into the metabolic control of cancer differentiation. Cancer Res; 78(7); 1604-18. ©2018 AACR.

Abstract 450: Aldo-keto reductase family 1 member b1 links glucose metabolism to epithelial-to-mesenchymal transition

Introduction: We performed a bioinformatic analysis to identify metabolic genes connected with the process of epithelial-to-mesenchymal-transition (EMT) and the results indicated a possible role for aldo-keto reductase family 1 member B1 (AKR1B1). AKR1B1 is a member of the polyol pathway responsible for catalyzing the reduction of numerous aldehydes, such as glucose. Based on the importance of EMT during carcinogenesis and metastatic progression and on the relevance of enhanced glycolytic rate in cancer cells, we investigated a direct role for AKR1B1 during EMT and tumor progression.

Experimental Procedure: The bioinformatic analysis was performed on datasets from the NCI60 panel of cancer cell lines. Cancer cells from lung, breast and ovarian origin have been investigated in vitro: changes in EMT markers were monitored by western blotting as well as immunofluorescence, growth assays were performed using the IncuCyte® ZOOM, migration rate was tested by wound-healing assays. Changes in stem-like properties were determined by western blotting, FACS and sphere-formation assays. Immunohistochemistry (IHC) was performed on FFPE specimens from lung cancer patients. Additionally, IHC was performed on samples from a mouse model of AOM-induced colon tumorigenesis in mice with an intestinal epithelial cell-specific p53 deletion (which were shown to undergo EMT) and in the wildtype counterparts.

Results: AKR1B1 gene and protein expression was found significantly higher (7-fold) in mesenchymal-like cells. ShRNA-mediated knockdown of AKR1B1 lead to mesenchymal-to-epithelial transition in vitro and suppressed EMT induced by TGF-β or by high glucose levels. Besides reduced migration, AKR1B1-deficient cells displayed decreased proliferation rate and colony-formation ability. Moreover, AKR1B1 knockdown or its inhibition with specific drugs diminished cancer stem cells. The phenotypes observed with AKR1B1 knockdown could be obtained by targeting sorbitol dehydrogenase (SORD), the second and last enzyme of the polyol pathway. Suppression of each enzyme resulted in an impaired glycolytic and oxidative metabolism and adding fructose, the end-product of the polyol pathway, rescued the expression of EMT markers. IHC on samples from the AOM-induced colon cancer model indicated a higher AKR1B1 expression in invasive tumors from p53ΔIEC mice as compared to both p53-deficient non-invasive or wildtype tumors. Finally, AKR1B1 staining of cancer tissues from a cohort of lung cancer patients confirmed a significant correlation with EMT and a negative prognostic value.

Conclusion: In summary, we describe a glucose-related pathway with a previously unknown role in regulating cancer plasticity and EMT, which links altered glucose metabolism to growth and migratory ability, with several potential implications. Targeting polyol pathway enzymes could be a potentially effective therapeutic strategy to arrest cancer progression.

Citation Format: Annemarie Schwab, Aarif Siddiqui, Maria Eleni Vazakidou, Francesca Napoli, Martin Boettcher, Bianca Menchicchi, Ida Rapa, Maximilian Waldner, Dimitrios Mougiakakos, Marco Volante, Florian Greten, Thomas Brabletz, Paolo Ceppi. Aldo-keto reductase family 1 member b1 links glucose metabolism to epithelial-to-mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 450. doi:10.1158/1538-7445.AM2017-450

Structure of chitosan determines its interactions with mucin

Synthetic and natural mucoadhesive biomaterials in optimized galenical formulations are potentially useful for the transmucosal delivery of active ingredients to improve their localized and prolonged effects. Chitosans (CS) have potent mucoadhesive characteristics, but the exact mechanisms underpinning such interactions at the molecular level and the role of the specific structural properties of CS remain elusive. In the present study we used a combination of microviscosimetry, zeta potential analysis, isothermal titration calorimetry (ITC) and fluorescence quenching to confirm that the soluble fraction of porcine stomach mucin interacts with CS in water or 0.1 M NaCl (at c < c*; relative viscosity, η(rel), ∼ 2.0 at pH 4.5 and 37 °C) via a heterotypic stoichiometric process significantly influenced by the degree of CS acetylation (DA). We propose that CS-mucin interactions are driven predominantly by electrostatic binding, supported by other forces (e.g., hydrogen bonds and hydrophobic association) and that the DA influences the overall conformation of CS and thus the nature of the resulting complexes. Although the conditions used in this model system are simpler than the typical in vivo environment, the resulting knowledge will enable the rational design of CS-based nanostructured materials for specific transmucosal drug delivery (e.g., for Helicobacter pylori stomach therapy).