Epithelial-mesenchymal transition (EMT) is a process implicated in invasion and metastasis. MDA-MB-468 breast cancer cells undergo EMT in response to epidermal growth factor (EGF) stimulation with a significant up-regulation of mesenchymal markers (e.g vimentin) and a down-regulation of epithelial markers (e.g. E-cadherin). The present study evaluated the role of Janus kinase (JAK) family and Src family kinase (SFK) signalling in the regulation of EGF-induced EMT marker expression in MDA-MB-468 breast cancer cells.
To investigate the role of JAK and SFK signalling, serum-deprived (0.5% FBS) MDA-MB-468 breast cancer cells were pre-treated with either JAK Inhibitor I or the SFK inhibitor PP2 (0.1, 1 or 10 ÂµM), respectively, for 1 h prior to stimulation with EGF (50 ng/mL) for 6 or 24 h. Real time RT-PCR was used to assess changes in mRNA levels of the EMT markers vimentin, Twist, Snail, N-cadherin and CD44/CD24. Immunoblotting was used to assess changes in STAT3 phosphorylation and vimentin protein expression. siRNA-mediated silencing of gene targets was performed using Dharmacon On-TARGETplus SMARTpool siRNA.
Both JAK Inhibitor I and PP2 (1 and 10 ÂµM) significantly inhibited EGF-mediated STAT3 activation. SFK signalling did not appear to regulate downstream expression of any of the EMT markers assessed, while JAK inhibition significantly inhibited vimentin mRNA and protein induction, but not other EMT markers. Independent siRNA-mediated silencing of JAK family members failed to replicate the phenotype observed with JAK Inhibitor I treatment.
The JAK signalling pathway appears to regulate EGF-induced vimentin in MDA-MB-468 cells. Our results also suggest potential redundancy within the JAK family in the regulation of the EMT marker vimentin.
Clinical trial identification
All authors have declared no conflicts of interest.