SQSTM1/p62 Enhances Breast Cancer Metastasis

1.Background Breast cancer has the highest incidence in female cancer threating to women's health seriously.Distant metastases are responsible for the most of the cancer related deaths,especially in breast cancer.Currently,we find new drugs inhibiting the breast cancer metastasis by targeting HER2,EGFR and VEGFR,etc.Metastasis is a multi-step process: the invading breast cancer cells escape from the primary tumor;transferred by the blood circulation;proliferate in the distant organs and become new metastases.Breast cancer distal metastases often occur in the liver,lungs,brain and bone organs.Epithelial-mesenchymal transition(EMT)process is an important part of breast cancer metastasis.Current studies have shown that some factors could affect metastasis,such as steroid hormone,transforming growth factor beta(TGF-?),matrix metalloproteinase(MMPs)and hypoxia-inducible factor 1 alpha(HIF-1?).p62 serves as a multiple functional protein and plays an important role in autophagy.Many researches have uncover p62 can regulate tumor proliferation,migration and stemness by autophagy-independent pathway.The high expression of p62 can be used as a predictor of poor prognosis of breast cancer patients.Researching on the regulatory mechanisms of metastasis will provide the theoretical basis for the selective medication on breast cancer.2.Methods Breast cancer cell lines MDA-MB-231,MCF-10 A and MCF-7 were used in this study.1.j The expression level of p62 in MDA-MB-231 cell line was higher than that in MCF-10 A and MCF-7.The p62 level was knocked down in 231 cell lines and over-expressed in MCF-10 A and MCF-7.The invasion and metastasis of breast cancer cells were studied by transwell experiment.2.The effect of changes of p62 expression level on the growth morphology of tumor cells was studied by three-dimensional culture.3.Draw the survival curve of breast cancer patient.Download the public data GSE6532 and GSE1379 from GEO database.4.Predict the target genes of p62 in breast cancer metastasis.Download the data of p62 interaction network,analysis in String and DAVID.3.Results1.p62 enhances the invasive and migrate ability of breast cancer cells.Silencing p62 expression dramatically reduced the invasive capacity of MDA-MB-231 cells to invade through matrigel pre-coated transwells.In contrast,overexpressing p62 in MCF-7 and MCF-10 A cells resulted in the acquisition of migration and invasion ability as indicated by the Wound healing and Transwell assays.2.p62 affects breast cancer cell morphology and growth pattern.Normal MDA-MB-231 cells grow separately and present the branching morphology,outward expanding in three dimensional culture,and Vimentin has been widely distributed.After knocking down the expression of p62,it has become spherical and Vimentin gathered outside the nucleus.3.High p62 expression correlates with poor clinical prognosis.4.Predicting the downstream target genes of p62 in breast cancer metastasis.These factors which interacted with p62 were enriched in NF-?B and MAPK signaling pathway.Parts of the molecules belong to protein kinase.RIPK and PRKC are the predicting targets of p62 in breast cancer metastasis.4.Conclusions(1)p62 overexpression enhances the metastatic ability of breast cancer cells.(2)RIPK and PRKC are the predicting targets of p62 in breast cancer metastasis.