Melatonin inhibits FAK signaling to suppress PD-L1 expression and enhance chemosensitivity in triple-negative breast cancer

Published on Tuesday, 10 March 2026

Abstract

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype lacking targetable hormone receptors, making conventional chemotherapy the primary treatment option, despite its associated toxicity and potential for drug resistance. Melatonin, a natural hormone with anticancer and immunomodulatory properties, has shown promise in multiple cancers; however, its role in TNBC remains unclear.

Methods: We analyzed serum melatonin levels in TNBC patients and healthy controls. The biological effects of melatonin were then evaluated in human (MDA-MB-231, MDA-MB-468) and murine (4T1) TNBC cell lines. In vitro assays assessed proliferation, apoptosis, migration, epithelial-mesenchymal transition (EMT), and chemosensitization. Mechanistic pathways were analyzed, and an orthotopic 4T1 syngeneic mouse model was employed to confirm antitumor and immunomodulatory effects in vivo.

Results: We found that TNBC patients had significantly lower serum melatonin levels than healthy controls. In vitro, melatonin reduced cell viability, migration, and tumorsphere formation, and promoted apoptosis. Mechanistically, it downregulated focal adhesion kinase (FAK) and programmed death-ligand 1 (PD-L1). FAK inhibition increased melatonin sensitivity, whereas FAK overexpression conferred resistance. Melatonin also enhanced cisplatin cytotoxicity. In vivo, melatonin treatment suppressed tumor growth, increased CD8⁺ T-cell infiltration, and decreased PD-L1 expression and the number of FOXP3⁺ regulatory T cells in the tumor microenvironment.

Conclusions: Melatonin suppresses TNBC progression by inhibiting proliferation and migration and by modulating the immune microenvironment through the FAK-PD-L1 axis. These findings highlight melatonin as a potential low-toxicity adjunct to enhance the efficacy of current TNBC therapies.

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About this publication.

The Di Bella's Method: Use of Melatonin, Retinoids (40mg per day Beta-Carotene, 10mg per day ATRA and 10mg per day Axerophthol palmitate), Estrogen therapy (Anastrozole 1 mg tab per day), pseudo-Metronomic Chemotherapy Cyclophosphamide and/or Hydroxyurea, Somatostatin/Octreotide analogues and/or derivatives with Cabergoline and/or Bromocriptine (together with others chemical compounds) in TNBC/Breast Cancer:

- A retrospective observational clinical study of triple negative breast cancer cases treated with Di Bella Method: A preliminary data;

- The Synergism of Somatostatin, Melatonin, Vitamins Prolactin and Estrogen Inhibitors Increased Survival, Objective Response and Performance Status In 297 Cases of Breast Cancer;

- Complete objective response, stable for 5 years, with the Di Bella Method, of multiple-metastatic carcinoma of the breast;

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonin, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 122 cases of breast cancer;

- Complete objective response to biological therapy of plurifocal breast carcinoma;

- The Di Bella Method (A Fixed Part - Melatonin tablets. From 30-40mg/day up to 200mg/day and more orally in patients with advanced stage of cancer disease and/or patients without respond to traditional treatments);

- Melatonin use in cancer patients have started in 1974, when melatonin prepared according to Prof. Di Bella’s formulation [...]. For 11 days was administered to the patient, admitted to the general medical ward at the Maggiore-Pizzardi Hospital in Bologna, very slowly (over approx. 8 hours) and intravenously administered 1000 mg of melatonin for 11 days. During the course of each day, the patient was intravenously administered 4 saline drips of 500 ml, each containing ten 25 mg bottles of freeze-dried melatonin, lasting 2 hours, totaling 1000 mg per day. No other drug of any kind was administered in order to ascertain the effect of the MLT without interference [...]. From Melatonin with adenosine solubilized in water and stabilized with glycine for oncological treatment - technical preparation, effectivity and clinical findings;

- About Melatonin - In vitro, review and in vivo publications;

- Publication: Melatonin anticancer effects: Review (from Di Bella's Foundation);

- Publication: Key aspects of melatonin physiology: 30 years of research (from Di Bella's Foundation);

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

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

- 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);