Melatonin Enhances the Antitumor and Immunomodulatory Effects of Bacillus Calmette-Guerin Immunotherapy in a Murine Bladder Cancer Model Publisher Pubmed



Menbari Oskouie I ; Khatami F ; Mesbah G ; Baghdadabad LZ ; Eidinezhad N ; Mashhadi R ; Zahmatkesh P ; Heshamt R ; Nikoofar P ; Aghamir SMK
Source: Molecular Biology Reports Published:2026

Abstract

Background: The intravesical Bacillus Calmette-Guerin (BCG) immunotherapy in Bladder Cancer (BC) is the standard adjuvant therapy with challenges such as limited efficacy and recurrence. We aimed to assess the synergistic antitumor effects of melatonin and BCG in vivo. Methods: The xerograph C57BL/6J mice model developed with injection of 2.0 × 10⁶ MB49 cells. After two weeks, mice were grouped: control (PBS + DMSO), melatonin (200 µg), high-dose BCG (HDBCG, 3.0 × 10⁶ CFU), melatonin with low-dose BCG (LDBCG + MLT, 1.0 × 10⁶ CFU), and melatonin with HDBCG (HDBCG + MLT). At the end of the study the histologically was assessed for proliferation, microangiogenesis, and inflammation. Complete blood counts (CBC), Erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were measured. Gene expression was determined by real-time PCR. Results: The HDBCG + MLT decreased tumor weight and volume compared with to LDBCG + MLT and HDBCG alone (p < 0.05). Histopathology showed HDBCG + MLT increased apoptosis and immune cell infiltration, with reduced mitotic figures and micro-vessel density. Serological analysis indicates HDBCG alone induced significant increases in WBC count and CRP levels, whereas co-administration of melatonin markedly attenuated these elevations (p < 0.05) without altering ESR. In HDBCG + MLT group, BAX, P53, Syn3, E-cadherin, IL-2, IL-10, and IFN-γ upregulated, while BCL-2, VEGF-A, HIF-1α, and TGF-α downregulated. Conclusions: Co-administration of melatonin enhanced the antitumor efficacy of BCG immunotherapy in BC, as evidenced by increased apoptosis and immune cell infiltration, along with marked suppression of angiogenesis and the EMT pathway. © The Author(s), under exclusive licence to Springer Nature B.V. 2026.