Inhibition of Ehrlich ascites carcinoma growth by melatonin: Studies with micro-CT

Melatonin is a versatile indolamine synthesized and secreted by the pineal gland in response to the photoperiodic information received by the retinohypothalamic signaling pathway. Melatonin has many benefits, such as organizing circadian rhythms and acting as a powerful hormone. We aimed to show the antitumor effects of melatonin in both in vivo and in vitro models through the mammalian target of rapamycin (mTOR) signaling pathway and the Argyrophilic Nucleolar Regulatory Region (AgNOR), using the Microcomputed Tomography (Micro CT). Ehrlich ascites carcinoma (EAC) cells were administered into the mice by subcutaneous injection. Animals with solid tumors were injected intraperitoneally with 50 and 100 mg/kg melatonin for 14 days. Volumetric measurements for the taken tumors were made with micro-CT imaging, immunohistochemistry (IHC), real-time polymerase chain reaction (PCR) and AgNOR. Statistically, the tumor tissue volume in the Tumor+100 mg/kg melatonin group was significantly lower than that in the other groups in the data obtained from micro-CT images. In the IHC analysis, the groups treated with Tumor+100 mg/kg melatonin were compared when the mTOR signaling pathway and factor 8 (F8) expression were compared with the control group. It was determined that there was a significant decrease (p < 0.05). Significant differences were found in the total AgNOR area/nuclear area (TAA/NA) ratio in the treatment groups (p < 0.05). Furthermore, there were significant differences between the amount of mTOR mRNA for the phosphatidylinositol 3-kinase (PI3K), AKT Serine/Threonine Kinase (PKB/AKT) genes (p < 0.05). Cell apoptosis was evaluated with Annexin V in an in vitro study with different doses of melatonin; It was observed that 100 µg/mL melatonin dose caused an increase in the apoptotic cell death. In this study, we have reported anti-tumor effects of melatonin in cell culture studies as well as in mice models. Comprehensive characterization of the melatonin-mediated cancer inhibitory effects will be valuable in advancing our fundamental molecular understanding and translatability of pre-clinical findings to earlier phases of clinical trials.