Inhibition of autophagy by 3-MA on Melatonin‑induced apoptosis in MCF-7 and MDA-MB-231 breast cancer cells

Aim: In this study, we looked at the connection between apoptosis and autophagy after our prior research indicated that melatonin could cause both MCF-7 and MDA-MB-231 cells. Material and methods: To examine the impact of melatonin, 3-methyladenine (3-MA), an autophagy inhibitor, or their combination on apoptotic cell death, two breast cancer cell lines, MCF-7 and MDA-MB-231, have been used. MCF-7 and MDA-MB-231 cells were exposed with melatonin after 5 mM 3-MA pre-culture. Then, apoptosis was detected by TUNEL method. Adouble immunofluorescence staining method assay was used to investigate the molecular changes of Bax/Bcl-2 expression that occurred in the course of treatment. Cell viability was measured by MTT assay. Results: When an autophagy inhibitor, 3-MA, and melatonin treatment were co-administered in MCF-7 cells, apoptosis was decreased, compared to melatonin treatment alone, but it was not significant. In addition, 3-MA application downregulated Bax expression compared with melatonin alone treatment. In MDA-MB-231 cells, the combination treatment of 3-MA and melatonin significantly increased the apoptotic cell death. Moreover, the pro-apoptotic protein, Bax, was significantly up-regulated by 3-MA. Conclusion: Taken together, in MCF-7 cells, inhibition of autophagy contributes to downregulation of apoptosis, whereas increased apoptosis is seen in MDA-MB-231 breast cancer cells. Inhibiting autophagy in MDA-MB-231 cells treated with melatonin could serve as a self-defense mechanism, and this may be a promising approach for adjuvant treatment for breast cancer.