Melatonin is best known for regulating sleep, but its biology extends far beyond circadian timing. A growing body of oncology research explores melatonin as a pleiotropic modulator of tumor behavior—affecting apoptosis, oxidative stress, angiogenesis, immune tone, and even drug resistance. The question for clinicians is not whether melatonin does “something” in cancer models; it is how these signals translate into meaningful outcomes for patients, and what a clinically responsible interpretation looks like today.

Mechanistic Signals Worth Watching

Mechanistically, melatonin interacts with multiple cancer-relevant pathways. Reviews in hematologic malignancies describe pro-apoptotic shifts (increased Bax/Bcl-2 ratio, cytochrome-c release, caspase activation), modulation of reactive oxygen species (paradoxically pro-oxidant in tumor contexts, antioxidant in normal tissue), and cell-cycle arrest. In glioblastoma models, additional anti-angiogenic and anti-invasion effects are reported, alongside impacts on mitochondrial function and autophagy. A separate mechanistic review centers on apoptosis, outlining melatonin’s capacity to sensitize malignant cells to cytotoxic therapies while offering redox protection to non-tumor tissues.

Of particular translational interest is melatonin’s interaction with the NF-κB axis and drug efflux machinery. In diffuse large B-cell lymphoma (DLBCL) cell lines, melatonin suppressed P-glycoprotein (ABCB1) expression via down-modulation of NF-κB signaling, increasing intracellular exposure to epirubicin and amplifying apoptosis. While these are in vitro data, the clarity of the pathway (NF-κB → P-gp → chemoresistance) provides a mechanistic rationale for clinical exploration.

What the Evidence Shows So Far

In hematologic cancers, a comprehensive review summarizes consistent anti-proliferative and pro-apoptotic effects across leukemia, lymphoma, and myeloma models, with adjunctive synergy alongside chemotherapy and radiotherapy. In glioblastoma, an oncology review aggregates preclinical evidence that melatonin curbs proliferation, migration, and angiogenesis, while enhancing sensitivity to standard therapies such as temozolomide. These lines of evidence are preclinical-dominant, but they are internally coherent across models: melatonin appears to destabilize tumor survival programs while supporting normal tissue resilience.

Clinical signals are beginning to surface. A randomized, placebo-controlled phase II study in head-and-neck cancer patients receiving high-dose radiotherapy with cisplatin tested a 3% melatonin mucoadhesive gel for oral mucositis prevention. While overall severe mucositis reduction was not statistically significant across the entire cohort, the cisplatin subgroup experienced significantly lower incidence and shorter duration of severe mucositis. This suggests a plausible role for melatonin as a localized supportive-care intervention, pending confirmatory phase III data.

Safety Landscape and Reported Dosing Ranges

A systematic review and meta-analysis of higher-dose melatonin in adults (≥10 mg) across diverse indications found no increase in serious adverse events or withdrawals due to adverse events in low-bias trials, though minor events (e.g., drowsiness, headache, dizziness) were more frequent. Safety reporting was inconsistent in many studies, and long-term data remain limited, but the aggregate short-term signal is generally reassuring.

In oncology research, reported melatonin exposure spans a wide spectrum: in vitro concentrations (often 0.1–1.0 mM) to probe mechanism; in vivo animal dosing that varies by model and route; and early clinical contexts using oral or topical formulations in supportive-care or adjunctive designs. These values describe research parameters rather than therapeutic standards, underscoring the need for rigorous trials that link pharmacokinetics and pharmacodynamics to clinical endpoints.

Where This Leaves Us Clinically

The weight of current evidence positions melatonin as a biologically active, multi-target molecule with two attributes clinicians care about: capacity to sensitize tumors to standard therapies and a tendency to protect normal tissues from treatment-related stress. The mucositis trial’s subgroup signal hints at tangible patient-facing benefits in supportive care. At the same time, most oncology-specific claims rest on preclinical or small early-phase data. The outstanding work is translational: trials that define indication-specific dosing, timing relative to cytotoxic therapy, formulation (systemic versus topical), and validated outcomes (response rates, toxicity reduction, quality of life, survival).

Until those data mature, melatonin’s oncologic profile is best described as “promising and plausible,” with mechanistic depth, encouraging early clinical signals, and a short-term safety profile that justifies further study. The task ahead is to convert signal into standards—with careful attention to pharmacology, patient selection, and endpoints that matter.

References

1. Li T, et al. Melatonin: does it have utility in the treatment of haematological neoplasms? Br J Pharmacol. 2018. PMCID: PMC6057911
2. Liu K, et al. Melatonin increases chemosensitivity of DLBCL cells to epirubicin via NF-κB–P-glycoprotein pathway. Transl Oncol. 2021. PMCID: PMC7527585
3. Moretti E, et al. Melatonin’s antineoplastic potential against glioblastoma. Anticancer Res. 2020. PMCID: PMC7140435
4. Li Y, et al. Melatonin for the prevention and treatment of cancer. Oncotarget/Review. 2015. PMID: 26184078
5. Andersen LP, et al. Safety of higher doses of melatonin in adults: a systematic review and meta-analysis. J Pineal Res. 2021. PMID: 34923676
6. Sánchez-González C, et al. High-dose melatonin mucoadhesive gel for prevention/treatment of oral mucositis in head & neck cancer: Phase II RCT. 2021. PMID: 33738704
7. Talib WH, et al. Modulation of apoptosis by melatonin for improving cancer therapy. J Pineal Res. 2019. PMID: 31077716

Notes: Dosing, schedules, and formulations mentioned in the cited literature describe research parameters only and do not constitute therapeutic standards.