Melatonin modulates microfilament phenotypes in epithelial cells: Implications for adhesion and inhibition of cancer cell migration

Cell migration and adhesion are cytoskeleton-dependent functions that play a key role in epithelial physiology. Specialized epithelial cells in water transport have specific microfilament rearrangements that make these cells adopt a polyhedral shape, forming a sealed monolayer which functions as permeability barrier. Also, specific polarized microfilament phenotypes are formed at the front and the rear of migratory epithelial cells. In pathological processes such as cancer, increased migration occurs in invasive cells driven by the formation of polarized and differential microfilament phenotypes. Melatonin, the main product secreted by the pineal gland during dark phase of the photoperiod, acts as a cytoskeletal modulator in normal and cancer cells. In this paper we will summarize evidence supporting that melatonin acts as a microfilament modulator in epithelial MDCK cells, and we will describe its effects on cytoskeleton organization involved in the mechanism by which melatonin synchronizes water transport. In addition, we will review recent data that indicate that melatonin is able to switch microfilament phenotypes in MCF-7 human mammary cancer cells, from invasive migratory cells to dormant microfilament phenotypes that occur in non-migratory cells. Moreover, we will discuss the implications of the cytoskeleton as therapeutic target for cancer cells.