Melatonin (N-acetyl-5-methoxytryptamine, MEL), secreted by the pineal gland, plays an important role in regulation of various functions in the human body. There is evidence that MEL exhibits antitumor effect in various types of cancer. We studied the combined effect of MEL and drugs from different pharmacological groups, such as cytarabine (CYT) and navitoclax (ABT-737), on the state of the pool of acute myeloid leukemia (AML) tumor cell using the MV4-11 cell line as model. The combined action of MEL with CYT or ABT-737 contributed to the decrease in proliferative activity of leukemic cells, decrease in the membrane potential of mitochondria, and increase in the production of reactive oxygen species (ROS) and cytosolic Ca2+. We have shown that introduction of MEL together with CYT or ABT-737 increases expression of the C/EBP homologous protein (CHOP) and the autophagy marker LC3A/B and decreases expression of the protein disulfide isomerase (PDI) and binding immunoglobulin protein (BIP), and, therefore, could modulate endoplasmic reticulum (ER) stress and initiate autophagy. The findings support an early suggestion that MEL is able to provide benefits for cancer treatment and be considered as an adjunct to the drugs used in cancer therapy.
Keywords: ER stress; autophagy; cytarabine; melatonin; navitoclax; proliferation.