The Mechanism Study Of A New Microtubule Inhibitor SQ On The Metastasis Of MCF-7 And MDA-MB-231 Cells

Breast cancer is the most common cause of cancer death in women of all ages in the world,and the main cause of death is due to the metastasis.Therefore,novel chemotherapeutic compounds with high activity and effect to anti-metastasis of breast cancers are needed urgently in research and development.Compounds that target microtubules are naturally a good choice for anti-metastasis because of their roles in altering microtubule dynamics.Taxol,a microtubule stabilizing agent,has always been the first-line drug in the clinical treatment for breast cancers,but it is easy to lead to poor prognosis with drug resistance.Combretastatin A-4(CA-4)is a natural active product of cis-stilbene structure extracted from the African Willow Combretum caffrum by Pettit et al.,which acts as an anti-tumor compound by inhibiting microtubule polymerization and easy to be isomerized into other inactive forms.3,4,5-Trimethoxyphenyl-3-hydroxy-4-methoxyphenylselenosulfoxide(SQ)is a CA-4 analogue with a selenium element as a bridging structure that significantly increases the stability of the compound.In our previous study we found that SQ has good anti-tumor effects through in vivo and in vitro experiments.Specifically,SQ inhibited breast cancer MCF-7 xenograft tumor growth in dose-dependent manner;SQ induced breast cancer MCF-7 and MDA-MB-231 cells undergoing G2/M phase arrest and thereby promoting apoptosis in timedependent manners;the inhibition of MDM2 expression by SQ treatment is involved in SQinduced apoptosis.Here,we found that SQ reversed epidermal growth factor(EGF)-induced motility and invasion in breast cancer cell lines by the in vitro Wound healing and Transwell assay.Further studies showed that SQ treatment resulted in inhibitory alteration of EGF-stimulated epithelialto-mesenchymal transition(EMT)and MMP-2 activity.What is more,SQ significantly inhibited the EGF-induced mouse double minute 2(MDM2)expression and transcription factor Twist1 expression.In addition,compared with the control cells,MDM2 overexpression upregulated Twistl expression and dramatically promoted cell migration and invasion,MDM2 under-expression also down-regulated Twist1 expression and suppressed cell motility and invasion.Further studies on anti-metastasis found that low-concentration SQ inhibited the motility and invasion of triple-negative breast cancer MDA-MB-231 cells,and was closely related to the inhibition of EMT and F-actin expression.Tube formation assay showed that SQ inhibited the formation of Vasculogenic mimicry(VM)in MDA-MB-231 cells,and it was found to be associated with down-regulation of VE-cadherin and EphA2 by western blot.Furthermore,since SQ inhibited VM formation,the expression of vascular endothelial growth factor(VEGF)was subsequently detected.SQ has a significant inhibitory effect on the protein expression and secretion of VEGF in MDA-MB-231 cells.Conditioned medium(CM)was collected and stimulated endothelial cell HUVEC.SQ-treated CM significantly inhibited the motility and invasion of HUVEC by the Wound healing and Transwell assay.In addition,exogenously VEGF reversed CM-inhibited EMT.In summary,this study evaluated a novel microtubule inhibitor SQ to inhibit breast cancer cell motility and invasion.In addtion,the effects of SQ on VM formation and endothelial cell migration and invasion in tumor microenvironment were also detected.We provides preliminary experimental data support and evidence for the development of SQ as a drug for breast cancer with anti-metastatic effect.It also provides a new therapeutic direction for triplenegative breast cancers which lacking hormone therapy targets.