Aurélien Pommier

High mobility group box protein 1 (HMGB1) is a ubiquitous protein that has multiple functions in the nucleus and cytosol. Following release into the extracellular space, HMGB1 acts as a mediator of inflammation. HMGB1 is overexpressed in many cancers and has both oncogenic and antitumoral effects. Here we investigated the role of HMGB1 expression by cancer cells in the antitumor immune response. Subcutaneous tumors were induced in mice by injection of wild-type or HMGB1-low engineered syngeneic cancer cells. Tumor growth and immune infiltration were assessed, and gene expression was analysed in whole tumors and isolated tumor cells by RNA sequencing analysis. Downregulation of cancer cell-intrinsic HMGB1 prevented tumor growth and reprogrammed the tumor microenvironment into a more inflamed phenotype. Tumor growth was not impacted in immunodeficient mice or in mice deficient in CD8 ⁺ T cells, demonstrating that the impact of HMGB1 downregulation on tumor progression was immune-dependent and mediated by CD8 ⁺ T cells. Transcriptional profiling showed that HMGB1 ^low tumors were enriched in immune pathways such as antigen presentation, T-cell receptor and cytokine signalling. Immune activation was robust and detectable in both tumor tissue and secondary lymphoid organs of mice bearing HMGB1 ^low tumors, but this did not facilitate immune infiltration of wild-type tumors that had been co-injected in the contralateral flank. We propose that tumor cell-intrinsic HMGB1 plays a critical role in modulating the local tumor microenvironment and in limiting anticancer immune responses. Thus, targeting cancer cell-intrinsic HMGB1 may represent a novel approach to improve the outcome of cancer immunotherapy.

Au cours de ces dernières décennies, l’augmentation de la consommation de glucides, d’acides gras et de cholestérol liée aux changements des habitudes alimentaires dans la plupart des pays industrialisés est à l’origine de nombreuses pathologies telles que l’obésité, les troubles cardiovasculaires, le développement du diabète de type II et la survenue de cancers. Plusieurs arguments bibliographiques suggèrent notamment que le cholestérol puisse être un élément à risque dans la survenue du cancer de la prostate. D’une part, l’hypercholestérolémie est associée à une augmentation des cas de cancer de la prostate et, d’autre part, les cellules cancéreuses présentent des dérèglements du métabolisme des lipides associés à l’accumulation de cholestérol dans les tumeurs solides. Les objectifs de ces travaux ont été d’analyser le rôle du cholestérol dans le développement du cancer de la prostate et d’étudier le rôle des récepteurs nucléaires LXRs (liver X receptors), régulateurs fondamentaux de l’homéostasie du cholestérol, dans les mécanismes associés à l’initiation et à la progression tumorale. Nos résultats montrent qu’une accumulation de cholestérol, induite par un régime chez les souris déficientes en LXRs, peut initier les premières étapes du développement tumoral par des mécanismes épigénétiques mettant en jeu l’action répressive de l’histone méthyltransférase EZH2 sur des gènes suppresseurs de tumeur. En parallèle, l’activation pharmacologique des LXRs dans des cellules cancéreuses humaines réduit la croissance tumorale en augmentant la mort des cellules par des mécanismes faisant intervenir les rafts lipidiques. Au total, nos travaux révèlent l’existence d’une relation entre la consommation excessive de cholestérol et la modification d’empreintes épigénétiques, mécanisme de plus en plus associé aux processus carcinogéniques. Nos données indiquent également que les LXRs, en s’opposant à l’accumulation de cholestérol intracellulaire, ralentissent l’initiation et la progression du cancer de la prostate. Ainsi, toute stratégie thérapeutique visant à diminuer le cholestérol intra-tumoral, telle que l’activation pharmacologique des LXRs, peut être considérée comme une piste thérapeutique dans le cadre du cancer de la prostate.

Although obesity is a major risk factor for cancer, it may also improve the response to cancer therapy. Here we investigated the impact of obesity on the efficacy of immune checkpoint inhibitors (ICI). In male mice, obesity promoted tumor growth but enhanced the response to ICI. This was associated with higher expression of immune-related genes within the tumor and enhanced infiltration of tumor-specific CD8 ⁺ T cells. Further, obesity in mice was associated with higher estrogen levels and enrichment of estrogen response genes in the tumor, and anti–programmed cell death 1 (anti–PD-1) efficacy was reduced upon administration of the aromatase inhibitor letrozole, which blocks the production of estrogens. Mechanistically, adipocyte-derived estrogens increased antigen presentation by dendritic cells and tumor-specific CD8 ⁺ T cell cytotoxicity. Last, overweight and obese men with melanoma responded better to ICI, with high estrogen levels being associated with improved response and survival. Our results suggest that estrogens may serve as a predictive factor of response to ICI in men with melanoma.

Chronic kidney disease (CKD) is a growing public health crisis, affecting over 10% of the global population and significantly increasing mortality and morbidity. Irrespective of its underlying cause, tubulointerstitial fibrosis (TIF) is a hallmark of CKD progression, with myofibroblasts being the primary effectors of renal fibrosis. Here, we show that 11beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is a critical driver of pathogenic myofibroblast differentiation and fibrosis in CKD. Using genetic deletion and pharmacological inhibition of 11β-HSD1 in mouse models, we demonstrate a marked reduction in TIF severity and improved renal function, linked to the suppression of a regulatory myofibroblast (Reg-MF) subpopulation. Single-cell and spatial transcriptomics data reveal that 11β-HSD1 is essential for the activation and expansion of Reg-MFs, which is conserved across species and predicts worse outcomes in CKD patients and kidney allograft recipients. These findings establish a direct link between 11β-HSD1 activity and renal fibrogenesis, highlighting its role during the transition from pericytes to pathogenic Reg-MFs. Our results support 11β-HSD1 inhibition as a promising therapeutic strategy to mitigate CKD progression, offering both mechanistic insights and translational potential for improving patient outcomes.

Although immune-based therapies have revolutionized the management of cancer, novel approaches are urgently needed to improve their outcome. We investigated the role of endogenous steroids in the resistance to cancer immunotherapy, as these have strong immunomodulatory functions. Using a publicly available database, we found that the intratumoral expression of 11 beta-hydroxysteroid dehydrogenase type 1 (HSD11B1), which regenerates inactive glucocorticoids into active glucocorticoids, was associated with poor clinical outcome and correlated with immunosuppressive gene signatures in patients with renal cell carcinoma (RCC). HSD11B1 was mainly expressed in tumor-infiltrating immune myeloid cells as seen by immunohistochemistry in RCC patient samples. Using peripheral blood mononuclear cells from healthy donors or immune cells isolated from the tumor of RCC patients, we showed that the pharmacological inhibition of HSD11B1 improved the response to the immune checkpoint inhibitor anti-PD-1. In a subcutaneous mouse model of renal cancer, the combination of an HSD11B1 inhibitor with anti-PD-1 treatment increased the proportion of tumor-infiltrating dendritic cells. In an intrarenal mouse tumor model, HSD11B1 inhibition increased the survival of mice treated with anti-PD-1. In addition, inhibition of HSD11B1 sensitized renal tumors in mice to immunotherapy with resiquimod, a Toll-like receptor 7 agonist. Mechanistically, we demonstrated that HSD11B1 inhibition combined with resiquimod increased T cell-mediated cytotoxicity to tumor cells by stimulating the antigen-presenting capacity of dendritic cells. In conclusion, these results support the use of HSD11B1 inhibitors to improve the outcome of immunotherapy in renal cancer and highlight the role of the endogenous glucocorticoid metabolism in the efficacy of immunotherapy.