TITLE:
Regulation of Breast Cancer Progression by Phosphorylation of the Tumor Suppressor Tropomyosin-1 Alpha
AUTHORS:
Mouna Zerradi, François Houle, Jacques Huot
KEYWORDS:
Tropomyosin 1, Phosphorylation, F-Actin, Cell Migration, Invasion
JOURNAL NAME:
Journal of Cancer Therapy,
Vol.6 No.9,
August
28,
2015
ABSTRACT: Background:
Tropomyosin 1 alpha chain (Tm1) is an actin-binding protein that regulates the
endothelial cell response to oxidative stress following its phosphorylation at
Serine 283 (S283). Tm1 is also a major tumor suppressor in breast cancer. In
the present study, we investigated the role of phosphorylation of Tm1 in
regulating its tumor suppressor properties. Methods: MDA MB231 breast cancer
cells stably overexpressing wild type form of Tm1 or Tm1 mutants (S283A and
S283E) were generated. Proliferation and cell viability were assayed by means
of the enzymatic cleavage of the tetrazolium salt WST-1 to formazan dye by
cellular mitochondrial dehydrogenases. Adhesion assays were performed at various
periods of time on cells grown on plastic. Cell migration was evaluated by
using the wound-healing assay and by measuring transendothelial migration of cancer cells. Malignant transformation in vitro was determined by using the
anchorage-independent growth assay on
soft agar. Results: We found that cells expressing the phosphomimetic form of Tm1 S283E/Tm1 are characterized by an increased adhesion to the
substratum. Moreover, the migration of MDA-MB231/S283E/Tm1 cells in a wound
closure assay is reduced compared to parental cells or those expressing the
non-phosphorylatable form of Tm1 (S283A). Similarly, the transendothelial
migration of MDA-MB231/S283E/Tm1 cells is also reduced as compared to the other
cell lines. Moreover, we found that the cells expressing the S283A mutants form
more colonies in soft agar that those expressing the S283E mutants. Conclusion:
Phosphorylation of Tm1 at Ser283 contributes to its anti-tumor properties, and
this effect results mainly from an increase in cell adhesion associated with a
decrease in their migratory and invasive potentials.