The inhibitory effect of melatonin on the proliferation of irradiated A549 cell line

Lung cancer is the leading cause of cancer-related deaths worldwide. The high resistance of this type of cancer to radiotherapy and chemotherapy is the greatest challenge for the complete eradication of cancer cells. Although the combination of chemotherapeutic agents has some promising results, severe side effects may limit the received tumor dose. The current study aimed at evaluating the possible synergic effect of melatonin on radiation-induced apoptosis and cell proliferation inhibition.

A549 cells were incubated with melatonin or vehicle and then irradiated with a single dose of 0, 0.5, 2, or 8 Gy X-rays. The cells were incubated with 1 nM of melatonin or vehicle for 1 week and then treated with 1 mM of melatonin or vehicle 1 h before irradiation. Cell proliferation was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and apoptosis was assessed using flowcytometry detection of annexin V.

Irradiation of the cells with different X-ray doses had no significant impact on MTT results. However, the administration of 1 mM of melatonin 1 h before irradiation significantly reduced the cell proliferation. Nonetheless, there was no significant difference between this treatment group and 1 mM melatonin group. Moreover, the administration of melatonin in combination with irradiation did not show any significant effects on radiation-induced apoptosis.

The current study results indicated that the treatment of A549 cells with melatonin could suppress cell proliferation, whereas it did not mediate the induction of apoptosis.