Background: Mammary cancer is the most prevalent type of cancer in female dogs. The main cause of
mortality is the occurrence of metastasis. The metastatic process is complex and involves the Epithelial-
Mesenchymal Transition (EMT), which can be activated by Transforming Growth Factor beta (TGF-β) and involves
changes in cellular phenotype, as well as, in the expression of proteins such as E-cadherin, N-cadherin, vimentin and
claudin-7. Melatonin is a hormone with oncostatic and anti-metastatic properties and appears to participate in the
TGF-β pathway. Thus, the present work aimed to evaluate the expression of EMT markers, E-cadherin, N-cadherin,
vimentin and claudin-7, as well as, the cell migration of the canine mammary cancer cell line, CF41, after treatment
with melatonin and TGF-β silencing.
Methods: Canine mammary cancer cell line, CF41, was cultured and characterized in relation to markers ER, PR
and HER2. Cell line CF41 with reducing expression level of TGF-βwas performed according to Leonel et al. (2017).
Expression of the protein E-caderin, N-cadherin, vimentin and claudin-7 was evaluated by immunocytochemistry
and quantified by optical densitometry. The analysis of cell migration was performed in transwell chambers with
8μM pore size membrane.
Results: CF41 cells present a triple negative phenotype, which is an aggressive phenotype. Immunocytochemistry
staining showed increased expression of E-caderin and claudin-7 (P˂0.05) and decreased expression of N-cadherin
and vimentin (P˂0.05) in CF41 cells after treatment with 1mM melatonin and TGF-β silencing. Moreover, treatment
with melatonin and TGF-β silencing was able to reduce migration in cell line CF41 (P˂0.05).
Conclusion: Our data suggests that therapies combining TGF- β1 silencing and melatonin may be effective in suppressing
the process of EMT, corroborating the hypothesis that melatonin acts on the TGF-β1 pathway and can
reduce the metastatic potential of CF41 cells. This is so far the first study that reports melatonin treatment in CF41
cells with TGF-β1 silencing and its effect on EMT. Thus, further studies are needed to confirm this hypothesis.