Preliminary Study On The SPA-1Regulating E-cadherin In Breast Cancer Cells

Cancer metastasis is the mainly reason of causing death of cancer patients. Epithelialto mesenchymal transitions (EMT) is one of the mechanisms. Firstly, normal epithelialcells develop into carcinoma in situ with cellular polarity disappearing. Then the basementmembranes gradually disperse since of intercellular adhesion destruction. Following theseepigenetic changes and genetic changes, cells migrate into the matrix and move to otherorgans via the lymphatic or blood circulation. During this process one of the most typicalsign is the gradual loss of epithelial cell adhesion molecule E-cadherin expression in EMT.Rap1, one of important small GTPase proteins, plays a critical role in cellproliferation and adhesion. It has been reported that Rap1activity participated inintercellular adhesion which is mediated by E-cadherin. E-cadherin plays an importantrole in the maintenance of epithelial cell morphology, structure and function.Signal-induced proliferation associated protein1(SPA-1), a kind of Rap1specific GAPs,is one of the candidate genes in breast cancer metastasis efficiency modifier locus Mtes1and closely associated with breast cancer metastasis.In order to explore the mechanism of how SPA-1regulates tumor metastasis, wecarried out immunohistochemistry method to detect SPA-1, Vimentin and E-cadherinexpression in ten breast cancer tissue sections from breast cancer patients to explore howSPA-1regulates E-cadherin during EMT process. The results showed that low E-cadherinexpression but high expression of vimentin were found in the EMT undergoing cellslocated directly at contact region of the surrounding stroma cells. However, highexpression of E-cadherin but no vimentin expression were identified in the epithelial cellsat the interior of islands region.SPA-1was found low expression in MCF-7breast cancer cell but high expression instrong metastatic MDA-MB-231breast cancer cells. After transfected Sipa1gene intoMCF-7cells, overexpression of SPA-1reduced E-cadherin expression. When knockeddown Sipa-1gene in MDA-MB-231cells, E-cadherin was clear detectablly induced. Inaddition, EMT related transcription factors such as HIF-1and Snail were decreased atmRNA level when Sipa1gene was silenced. On the other hand, when MCF-7cells were treated with EGTA to destruct intercellular adhesion, E-cadherin kept identical expressionlevel in both vector or Sipa1gene transfected cells.In summary, these results indicated that SPA-1may play an important role to regulateE-cadherin expression during breat cancer cell EMT and EMT related HIF-1transcriptionfactor.