Inhibition of ERK1/2 Signaling Pathway is Involved in Melatonin's Antiproliferative Effect on Human MG-63 Osteosarcoma Cells

Abstract

Background: In a previous study, we found that melatonin inhibits MG-63 osteosarcoma cell proliferation; however, the underlying mechanisms remain elusive. Mitogen-activated protein kinase (MAPK) and Akt signaling pathways play key roles in the anticancer effects of melatonin. Aims: The present study investigated whether MAPK and Akt signaling pathways are involved in melatonin's antiproliferative actions on the human MG-63 osteosarcoma cells. Methods/Results: Western blot analysis confirmed that melatonin significantly inhibited phosphorylation of ERK1/2 but not p38, JNK, or Akt. The expression of ERK1/2, p38, JNK, and Akt was not altered by melatonin. PD98059 and melatonin alone, and especially in combination, significantly inhibited cell proliferation. The changes included G₁ and G₂/M phase arrest of the cell cycle, and a downregulation of the expression at both the protein and mRNA levels of cyclin D1 and CDK4 (related to the G₁ phase) and of cyclin B1 and CDK1 (related to the G₂/M phase) as measured by flow cytometry after propidium iodide staining, and both western blot and real-time PCR, respectively. Furthermore, the combination of PD98059 and melatonin synergistically and markedly augmented the action of either agent alone. Co-immunoprecipitation further confirmed that there was an interaction between p-ERK1/2 and cyclin D1, CDK4, cyclin B1, or CDK1, which was blunted in the presence of melatonin or PD98059. Conclusion: These findings suggest that melatonin's antiproliferative action is mediated by inhibition of the ERK1/2 signaling pathway rather than the p38, JNK, or Akt pathways.

Melatonin, a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis

“…Considering other studies showing that melatonin inhibition of cancer cell growth involves mitogen-activated kinases and AKT signaling, Liu et al [268] examined changes in these signaling pathways in an attempt to determine if they also relate to the mechanisms by which melatonin interferes with the proliferation of osteosarcoma cells. In human MG-63 osteosarcoma cells, melatonin significantly inhibited the phophoactivation of ERK1/2 but was without effect on either p38, JNK or AKT.…”

“…Likewise, when MG-63 cells were incubated with a combination of melatonin and PD98059, it highly effectively blocked ERK1/2 activation. Thus, ERK1/2 inhibition is likely involved in the process by which melatonin arrests MG-63 osteosarcoma cells in the G1 and G2/M phases of the cell cycle [268]. In contrast, since p38, JNK and AKT were not changed by melatonin treatment, it was concluded these pathways are not involved.…”

Increase in motility and invasiveness of MCF7 cancer cells induced by nicotine is abolished by melatonin through inhibition of ERK phosphorylation

“…Numerous studies have documented that melatonin displays several anticancer effects, by pleiotropically acting upon different targets, including ERK activation . Indeed, melatonin can efficiently mitigate and even suppress migration and invasiveness in different cancer types, such as nasopharyngeal, renal, gastrointestinal, and breast tumors, probably involving a wide range of different actions, including CSK remodeling …”

Melatonin-Induced Changes in Cytosolic Calcium Might be Responsible for Apoptosis Induction in Tumour Cells

“…In a gastric cancer cell line it was already shown that proapoptotic effect of melatonin could be due to activation of a Caspase-dependent pathway and inhibition of the nuclear translocation of NF-κB p65, two processes that are regulated by p38 and c-Jun N-terminal kinase (JNK) [18]. Nevertheless, in human MG-63 osteosarcoma cells melatonin´s antiproliferative action was mediated by inhibition of the extracellular signal-regulated kinase (ERK1/2) signalling pathway rather than the p38, JNK, or Akt pathways [19]. However, the precise molecular mechanisms of melatonin action in cancer cells are still under investigation.…”