Effect of melatonin treatment on the intratumor heterogeneity in breast cancer model
Session type: Poster / e-Poster / Silent Theatre session
Cancer progression is strongly influenced by intratumor heterogeneity, which can be resultant of acidification of tumor microenvironment by hypoxia and preferential anaerobic glycolysis. In this context, melatonin, has shown several antitumor actions, as immunomodulatory, antioxidant, pro-apoptotic, antiangiogenic and possibly can control the intratumor heterogeneity. The aims of this study were to evaluate the action of melatonin on intratumor heterogeneity in breast cancer by in vitro and in vivo studies.
Triple-negative breast cancer cells (MDA-MB-231) were implanted in Balb/c nude mice (n=14), which were treated with melatonin (n=7) or vehicle (n=7). At the end, micro-PET/CT scanning was performed with 18F-FDG, which is an analogue of glucose, and with 18F-FAZA, a specific radiopharmaceutical for hypoxia detection. Then, markers of hypoxia (pimonidazole, HIF-1α, GLUT-1/3, CA-IX/XII) were evaluated by immunohistochemistry in mammary tumors. To in vitro studies MDA-MB-231 cells were treated with melatonin or vehicle under normal pH and low pH conditions (acidosis) and gene and protein expression of hypoxia markers were evaluated by qPCR and immunocytochemistry.
The results showed that there was a lower tumor growth in animals treated with melatonin (p<0.05). The PET/CT images showed that in some tumors with high volume, there was no uptake of 18F-FDG in the tumor center, corresponding to areas of necrosis, and there was an intratumor 18F-FAZA uptake heterogeneity, indicating possible hypoxic areas. All markers of hypoxia evaluated by immunohistochemistry showed less expression in melatonin treated tumors (p<0.05). Also, the in vitro results were correlated with the in vivo study, showing that melatonin has effectiveness under acidosis conditions.
Taken together, our results showed an important action of melatonin in control the adverse conditions in tumor microenvironment and control the cancer progression.