Melatonin as an Epigenetic Modulator to Regulate Angiogenesis in Dalton's Lymphoma

Melatonin (N-acetyl-5-methoxy-tryptamine) is a promising antitumor agent and antioxidant. The pharmacological dose of melatonin has an oncostatic function by various means, including angiogenesis. Evidences indicate that melatonin, using multiple interrelated mechanisms, exhibits a variety of oncostatic properties in a variety of tumors during different stages of progression.

The present study was undertaken to investigate the epigenetic modulations in the vascular endothelial growth factor VEGF, TIMP3, and CDH1 genes in Dalton lymphoma (DL) cells; furthermore, melatonin may reverse these epigenetic modulations. Endothelial cells (ECs) are the precursors for the development of new blood vessels; therefore, an EC proliferation assay was performed with and without DL ascites (DLA). EC migration leads to capillary formation, in which matrix metalloproteinases (MMPs) play a very important role in providing space for EC proliferation and migration. Furthermore, ECs were checked for MMP-9 secretion through enzyme-linked immunosorbent assay. The MMP activity was also confirmed by gelatin zymography. Reactive oxygen species (ROS) level was also measured on ECs in the presence and absence of DLA. These activities of ECs or the tumor microenvironment were regulated by growth factors, such as VEGF secretion by cancer cells and the inhibition or silencing of endogenous antiangiogenic genes. In this, chromatin modification plays a very important role; also, in this, DNA methylation and histone deacetylases (HDACs) play a significant role. So, in the DL cells, the authors try to find the HDACs and DNMTs levels with respect to the control thymus cells by Reverse Transcription-polymerase chain reaction (RT-PCR). Further DNA methylation was checked by the MS-PCR technique. Proteins and melatonin were studied using VINA 2.0 software.

DLA promote a significant increase in EC proliferation and a high amount of MMP-9 in the presence of DLA. The gelatin zymography also showed the high activity of MMP-2 and MMP-9 with respect to normal ECs. The ROS levels are also found to be high in DLA-induced ECs. The melatonin treatment successfully decreases EC proliferation, MMP-9 levels, and the MMP-2 and MMP-9 activities. The ROS levels were also reduced. The RT-PCR analysis showed that the melatonin modulates the alterations in HDAC1, 2, 6, and 9 and DNMT1, DNMT3A and DNMT3B with respect to the control. The MS-PCR results signify one of the possible ways of action of melatonin on DL cells.