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All-trans retinoic acid suppresses CD8+ T-cell terminal exhaustion and potentiates anti-PD-1 therapy in glioblastoma

Published on Friday, 11 September 2026

Abstract

Terminal exhaustion of CD8⁺ T cells limits the efficacy of immune checkpoint blockade (ICB), particularly in glioblastoma, which is characterized by an immunosuppressive tumor microenvironment. Therefore, a better understanding of the regulators of terminal exhaustion could overcome intrinsic resistance to ICB and improve the efficacy of immunotherapy.

In this study, we report that all-trans retinoic acid (ATRA) suppresses CD8⁺ T-cell terminal exhaustion. The administration of ATRA during CD8⁺ T-cell activation in vitro conferred resistance to terminal exhaustion and preserved effector cytokine production and effector function.

Mechanistically, ATRA selectively induced the expression of the long isoform of T-cell factor 1 (TCF-1βBD) through activation of the canonical WNT/β-catenin pathway. In a mouse glioma model, adoptively transferred ATRA-conditioned CD8⁺ T cells exhibited increased TCF-1βBD and β-catenin expression and resistance to exhaustion, which led to superior tumor-infiltrating CD8+ T-cell polyfunctionality and enhanced glioma suppression.

Importantly, oral administration of ATRA also suppressed terminal exhaustion of tumor-infiltrating CD8+ T cells and synergized with anti-PD-1 therapy, overcoming resistance to immune checkpoint blockade (ICB) in two mouse models of glioma. Combined ATRA and anti-PD-1 treatment also displayed synergistic therapeutic potential by significantly reducing recurrence in a mouse model of glioma that had undergone surgical resection.

Single-cell transcriptomic analysis of glioblastoma patients receiving anti-PD-1 therapy revealed that CD8⁺ T cells from responders were enriched in genes that respond to retinoic acid and WNT-associated genes, which correlated with improved survival.

These findings establish ATRA as a modulator of CD8⁺ T-cell exhaustion through the induction of WNT/β-catenin-dependent TCF-1βBD expression, suggesting that ATRA has therapeutic potential for overcoming resistance to ICB in glioma.

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About this publication.

The Di Bella's Method: Use of Retinoids (40mg per day Beta-Carotene, 10mg per day ATRA and 10mg per day Axerophthol palmitate), Melatonin (since 1974), Somatostatin/Octreotide analogues and/or derivatives (since 1977), Vitamin D, prolactin inhibitors Cabergoline and/or Bromocriptine with pseudo-Metronomic Chemotherapy Cyclophosphamide and/or Hydroxyurea (together with others chemical compounds) in Glioblastoma, Brain/Head&Neck Cancer (the dosage and administration schedule must be individualised for each patient):

- Recurrent Glioblastoma Multiforme (grade IV – WHO 2007): a case of complete objective response achieved by means of the concomitant administration of Somatostatin and Octreotide – Retinoids – Vitamin E – Vitamin D3 – Vitamin C – Melatonin – D2 R agonists (Di Bella Method – DBM) associated with Temozolomide;

- A retrospective observational study on cases of anaplastic brain tumors treated with the Di Bella Method: A rationale and effectiveness;

- The Di Bella Method DBM improved survival objective response and performance status in a retrospective observational clinical study on 23 tumours of the head and neck;

- The Di Bella Method (A Fixed Part - All-Trans Retinoic Acid, Analogues and/or Derivatives - Approximately 60mg per day orally: 40mg per day Beta-Carotene/β-Carotene, 10mg per day ATRA and 10mg per day Axerophthol palmitate);

- All-Trans-Retinoic Acid (ATRA - analogues and/or derivatives) - In vitro, review and in vivo publications;

- Solution of retinoids in vitamin E in the Di Bella Method biological multitherapy;

- The Di Bella Method (A Fixed Part - Alpha tocopheryl acetate/Vitamin E, approximately 20 grams per day orally);

- Cancer and Vitamin E (analogues and/or derivatives) and cancer - In vitro, review and in vivo publications;

- The Di Bella Method (A Variable Part - Chondroitin sulfate/Proteoglycans/Glycosaminoglycans, up to 3-4 grams per day, orally);

- The Di Bella Method (A Fixed Part - Somatostatin, Octreotide, Sandostatin LAR, analogues and/or derivatives since 1977);

- Somatostatin in oncology, the overlooked evidences - In vitro, review and in vivo publications;

- Publication, 2018 Jul: Over-Expression of GH/GHR in Breast Cancer and Oncosuppressor Role of Somatostatin as a Physiological Inhibitor (from Di Bella's Foundation);

- Publication, 2018 Sep: The over-expression of GH/GHR in tumour tissues with respect to healthy ones confirms its oncogenic role and the consequent oncosuppressor role of its physiological inhibitor, somatostatin: a review of the literature (from Di Bella's Foundation);

- Publication, 2019 Aug: The Entrapment of Somatostatin in a Lipid Formulation: Retarded Release and Free Radical Reactivity (from Di Bella's Foundation);

- Publication, 2019 Sep: Effects of Somatostatin and Vitamin C on the Fatty Acid Profile of Breast Cancer Cell Membranes (from Di Bella's Foundation);

- Publication, 2019 Sep: Effects of somatostatin, curcumin, and quercetin on the fatty acid profile of breast cancer cell membranes (from Di Bella's Foundation);

- Publication, 2020 Sep: Two neuroendocrine G protein-coupled receptor molecules, somatostatin and melatonin: Physiology of signal transduction and therapeutic perspectives (from Di Bella's Foundation);

- The Di Bella Method (A Fixed Part - Bromocriptine and/or Cabergoline);

- Prolactin inhibitors in oncology - In vitro, review and in vivo publications;

- The Di Bella Method (A Fixed Part - Cyclophosphamide 50mg tablets and/or Hydroxyurea 500mg tablets, one or two per day);

The Di Bella's Method: Use of Retinoic Acid, Beta-Carotene and Axerophthol palmitate in Vitamin E with pseudo-Metronomic Chemotherapy Cyclophosphamide and/or Hydroxyurea - together with others chemical compounds: the dosage and administration schedule must be individualised for each patient - in several Oncological Pathologies:

- Chronic Lymphocytic Leukemia: Long-Lasting Remission with Combination of Cyclophosphamide, Somatostatin, Bromocriptine, Retinoids, Melatonin, and ACTH;

- Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in advanced non-small-cell lung cancer patients with low performance status;

- Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in chemotherapy-pretreated patients with advanced lung adenocarcinoma and low performance status;

- Observations on the Report of a case of pulmonary adenocarcinoma with lymph node, hepatic and osseus metastasis;

- Pleural Mesothelioma: clinical records on 11 patients treated with Di Bella's Method;

- Malignant pleural mesothelioma, stage T3-T4. Consideration of a case study;

- Excellent result in a Mesothelioma case treated exclusively with Di Bella Method for over 4 years and still treatment with positive results;

- A case of advanced Multiple Myeloma treated with Di Bella Method (DBM) into total remission for 13 years;

- Neuroblastoma: Complete objective response to biological treatment;

- Cyclophosphamide plus Somatostatin, Bromocriptin, Retinoids, Melatonin and ACTH in the Treatment of Low-grade Non-Hodgkin’s Lymphomas at Advanced Stage: Results of a Phase II Trial;

- Relapse of High-Grade Non-Hodgkin’s Lymphoma After Autologous Stem Cell Transplantation: A Case Successfully Treated With Cyclophosphamide Plus Somatostatin, Bromocriptine, Melatonin, Retinoids, and ACTH;

- Low-grade Non-Hodgkin Lymphoma at Advanced Stage: A Case Successfully Treated With Cyclophosphamide Plus Somatostatin, Bromocriptine, Retinoids, and Melatonin;