Parkin Deficiency Suppresses Antigen Presentation to Promote Tumor Immune Evasion and Immunotherapy Resistance

Parkin is an E3 ubiquitin ligase, which plays a key role in the development of Parkinson disease. Parkin defects also occur in numerous cancers, and a growing body of evidence indicates that Parkin functions as a tumor suppressor that impedes a number of cellular processes involved in tumorigenesis. Here, we generated murine and human models that closely mimic the advanced-stage tumors where Parkin deficiencies are found to provide deeper insights into the tumor suppressive functions of Parkin. Loss of Parkin expression led to aggressive tumor growth, which was associated with poor tumor antigen presentation and limited antitumor CD8+ T-cell infiltration and activation. The effect of Parkin deficiency on tumor growth was lost following depletion of CD8+ T cells. In line with previous findings, Parkin deficiency was linked with mitochondria-associated metabolic stress, PTEN degradation, and enhanced Akt activation. Increased Akt signaling led to dysregulation of antigen presentation, and treatment with the Akt inhibitor MK2206-2HCl restored antigen presentation in Parkin-deficient tumors. Analysis of data from patients with clear cell renal cell carcinoma indicated that Parkin expression was downregulated in tumors and that low expression correlated with reduced overall survival. Furthermore, low Parkin expression correlated with reduced patient response to immunotherapy. Overall, these results identify a role for Parkin deficiency in promoting tumor immune evasion that may explain the poor prognosis associated with loss of Parkin across multiple types of cancer.

SIGNIFICANCE

Parkin prevents immune evasion by regulating tumor antigen processing and presentation through the PTEN/Akt network, which has important implications for immunotherapy treatments in patients with Parkin-deficient tumors.

Modulation of the gut microbiota engages antigen cross-presentation to enhance antitumor effects of CAR T cell immunotherapy

Several studies have shown the influence of commensal microbes on T cell function, specifically in the setting of checkpoint immunotherapy for cancer. In this study, we investigated how vancomycin-induced gut microbiota dysbiosis affects chimeric antigen receptor (CAR) T immunotherapy using multiple preclinical models as well as clinical correlates. In two murine tumor models, hematopoietic CD19+-A20 lymphoma and CD19+-B16 melanoma, mice receiving vancomycin in combination with CD19-directed CAR T cell (CART-19) therapy displayed increased tumor control and tumor-associated antigens (TAAs) cross-presentation compared with CART-19 alone. Fecal microbiota transplant from human healthy donors to pre-conditioned mice recapitulated the results obtained in naive gut microbiota mice. Last, B cell acute lymphoblastic leukemia patients treated with CART-19 and exposed to oral vancomycin showed higher CART-19 peak expansion compared with unexposed patients. These results substantiate the role of the gut microbiota on CAR T cell therapy and suggest that modulation of the gut microbiota using vancomycin may improve outcomes after CAR T cell therapy across tumor types.

Abstract 3846: Parkin regulates tumor evasion by controlling antigen processing and presentation through the PTEN/AKT network

A growing body of evidence supports the role of Parkin as a tumor suppressor involved in a number of cellular processes, including the downregulation of cell cycle and proliferation, migration, invasion, metastasis, mitophagy, and energy metabolic reprogramming. Indeed, epidemiological, genetic, and bioinformatic studies have shown multiple degrees of defects in the PARK2 gene, localized in human chromosome 6q25-27, a region frequently lost in cancers. In the present study, we show a novel role of Parkin in tumor immune surveillance through dysregulation of the PTEN/PI3k/AKT pathway, involving the modulation of antigen presentation machinery and antitumor-specific CD8+ T cell reactivity. We generated murine and human models that resemble the advanced-stage tumors where Parkin deficiencies are mostly found. In the mouse models, we observed a striking increase of tumor aggressiveness in the absence of Parkin that was associated with loss of antigen presentation and a significant decrease in the infiltration of antitumor CD8+ T cells. Importantly, loss of PARK2 also affected the efficacy of a Tumor-Associated Mitochondria Antigens (TAMAs) based vaccine showing the crucial role of Parkin in tumor development and in the context of antitumor cellular therapeutic strategies. Moreover, we also found that the lack of Parkin in the B16-OVA melanoma model also negatively impacts cytosol-derived antigen presentation and CD8+ T cell immunity. Finally, the analysis of TCGA tumor atlas validates the relevance of PARK2 loss on cancer immunotherapy effectiveness. Thus, during the progression and immunotherapy of cancer, the presence of Parkin mutations that result in loss of its functionality impact antigen presentation and facilitate tumor evasion.

Citation Format: Renzo Perales Linares, Hesham Mohei, Nektaria M. Leli, Silvia Beghi, Nektarios Kostopoulos, Amit Maity, Costantinos Koumenis, Andrea Facciabene. Parkin regulates tumor evasion by controlling antigen processing and presentation through the PTEN/AKT network [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3846.

Changes in the lipid profile of elite basketball and soccer players after a match

The lipid profile of elite basketball and soccer athletes was evaluated and compared with that of inactive individuals. Total cholesterol (T-C), low and high density lipoprotein cholesterol (LDL-C and HDL-C), and triglyceride (TG) concentration were measured in the morning and after a soccer or a basketball match. All parameters of lipid profile measured at a fasted and resting state, except HDL-C, were lower in the athletes compared with the controls (p < 0.01). The soccer match resulted in a greater decrease in TG (78.3 ± 6.7 to 70.7 ± 6.3, p < 0.01), T-C (179.3 ± 10.7 to 171.6 ± 9.6, p < 0.01), LDL-C (110.9 ± 8.9 to 103.5 ± 7.5, p < 0.01) compared with the basketball match that resulted only in a decrease in LDL-C (126.8 ± 9.5 to 117.3 ± 9.1, p < 0.01) and an increase in HDL-C that was similar to that observed after the soccer match (9-12%). These findings support the beneficial effects of basketball and soccer on cardiovascular health.