p62/SQSTM1 interacts with vimentin to enhance breast cancer metastasis.

The signalling adaptor p62 is frequently overexpressed in numerous cancer types. Here, we found that p62 expression was elevated in metastatic breast cancer and its overexpression correlated with reduced metastasis- and relapse-free survival times. Analysis of p62 expression in breast cancer cell lines demonstrated that high p62 expression was associated with the invasive phenotypes of breast cancer. Indeed, silencing p62 expression attenuated the invasive phenotypes of highly metastatic cells, whereas overexpressing p62 promoted the invasion of non-metastatic cells in in vitro microfluidic model. Moreover, MDA-MB-231 cells with p62 depletion which were grown in a three-dimensional culture system exhibited a loss of invasive protrusions. Consistently, genetic ablation of p62 suppressed breast cancer metastasis in both zebrafish embryo and immunodeficient mouse models, as well as decreased tumourigenicity in vivo. To explore the molecular mechanism by which p62 promotes breast cancer invasion, we performed a co-immunoprecipitation-mass spectrometry analysis and revealed that p62 interacted with vimentin, which mediated the function of p62 in promoting breast cancer invasion. Vimentin protein expression was downregulated upon p62 suppression and upregulated with p62 overexpression in breast cancer cells. Linear regression analysis of clinical breast cancer specimens showed a positive correlation between p62 and vimentin protein expression. Together, our findings provide strong evidence that p62 functions as a tumour metastasis promoter by binding vimentin and promoting its expression. This finding might help to develop novel molecular therapeutic strategies for breast cancer metastasis treatment.

Inhibition of AURKA kinase activity suppresses collective invasion in a microfluidic cell culture platform.

Tumor local invasion is the first step of metastasis cascade which remains the key obstacle for cancer therapy. Collective cell migration plays a critical role in tumor invading into surrounding tissues. In vitro assays fail to assess collective invasion in a real time manner. Herein we aim to develop a three-dimensional (3D) microfluidic cell invasion model to determine the dynamic process. In this model, collective invasion of breast cancer cells is induced by the concentration gradient of fetal bovine serum. We find that breast cancer cells adopt a collective movement rather than a random manner when the cells invade into extracellular matrix. The leading cells in the collective movement exhibit an increased expression of an Aurora kinase family protein - AURKA compared with the follower cells. Inhibition of AURKA kinase activity by VX680 or AKI603 significantly reduces the phosphorylation of ERK1/2 (Thr202/Tyr204) and collective cohort formation. Together, our study illustrates that AURKA acts as a potential therapeutic target for suppressing the process of tumor collective invasion. The 3D microfluidic cell invasion model is a reliable, measurable and dynamic platform for exploring potential drugs to inhibit tumor collective invasion.

A novel small molecule aurora kinase inhibitor attenuates breast tumor-initiating cells and overcomes drug resistance.

Chemoresistance is a major cause of cancer treatment failure. Tumor-initiating cells (TIC) have attracted a considerable amount of attention due to their role in chemoresistance and tumor recurrence. Here, we evaluated the small molecule Aurora kinase inhibitor AKI603 as a novel agent against TICs in breast cancer. AKI603 significantly inhibited Aurora-A (AurA) kinase and induced cell-cycle arrest. In addition, the intragastric administration of AKI603 reduced xenograft tumor growth. Interestingly, we found that breast cancer cells that were resistant to epirubicin expressed a high level of activated AurA and also have a high CD24(Low)/CD44(High) TIC population. The inhibition of AurA kinase by AKI603 abolished the epirubicin-induced enrichment of TICs. Moreover, AKI603 suppressed the capacity of cells to form mammosphere and also suppressed the expression of self-renewal genes (ß-catenin, c-Myc, Sox2, and Oct4). Thus, our work suggests the potential clinical use of the small molecule Aurora kinase inhibitor AKI603 to overcome drug resistance induced by conventional chemotherapeutics in breast cancer.