MiR-22-3p Negatively Regulates The Role Of NLRP3/Caspase-1/IL-1? Axis In Invasion And Metastasis Of Breast Cancer

BackgroundBreast cancer is the first malignant tumor in women and its mortality rate is second only to lung cancer."Global cancer statistics,2018" that were published online in CA in 2018 show that about 2.1 million women suffering from breast cancer,which killed about 630,000 patients,and the incidence rate of 10%to 12%of the annual of various malignant tumors.Tumor metastasis is the leading cause of death in cancer patients and it is difficult to inhibit this process with existing treatment methods.Tumor metastasis can be divided into cellular autonomous metastasis and non-cellular autonomous metastasis,but the type of metastasis of breast cancer has not been clearly recognized.Therefore,further elucidation of the molecular mechanism of breast cancer metastasis and search for new therapeutic methods are the focus of breast cancer prevention and treatment.Inflammasome is a complex of various intracellular proteins that composed of Nod-like receptor(NLR),apoptosis-related speckle-like protein(ASC)and cysteinyl aspartate specific proteinase(Caspase-1).It is an important component of innate immunity,which can recognize endogenous danger signals and cause inflammatory immune response.Inflammation fundamentally determines the different stages of breast cancer development,including initiation,progression,and metastasis.Nod-like receptor protein 3(NLRP3)was found to be required for tumor progression.Existing research have shown that NLRP3 inflammasome polymorphism is associated with various malignant tumors such as colon cancer and melanoma,but whether NLRP3 inflammasome is associated with breast cancer metastasis has not been reported yet.Therefore,this study aims to clarify the role of NLRP3 inflammasome in breast cancer metastasis and clarify its specific regulatory mechanism.MethodsFirst,Oncomine database was used to identify the NLRP3 mRNA levels in different breast cancer data sets.By adopting TCGA,microarrays of breast cancer tissues and breast cancer cell lines,we clarified the relationship of NLRP3 expression and invasive breast cancer.Later,MDA-MB-231 and MCF-7 stable expression cell lines with NLRP3 down regulation and overexpression were established by lentivirus transfection.The effects of NLRP3 on the metastatic ability of breast cancer cells in vitro and in vivo were observed by Would-healing test,Transwell test,zebrfish and nude mouse tumor bearing models.Furthermore,the effects of NLRP3 on downstream caspase-1 and IL-1? signals were detected by Immunofluorescence,Western blot and ELISA.we found miR-22-3p targeting NLRP3 through qPCR,Western blot,and dual luciferase reporter assays.ResultsWe found that the expression of NLRP3 mRNA level in invasive breast cancer data sets was higher than that in normal tissues.Meanwhile,15 patients with different clinical stages of breast cancer and invasive breast cancer microarray BC081120e was used to detect the expression of NLRP3,and notably higher expression of NLRP3 was found in invasive ductal carcinoma than adjacent normal breast tissue.The mRNA and protein levels of NLRP3/caspase-1/IL-1? in triple negative breast cancer cells MDA-MB-231 are higher than those in other breast cancer cell lines.Treatment with MCC950 or siRNA can inhibit its metastatic ability in vitro and in vivo.On the contrary,overexpression of NLRP3 in MCF-7 cells can promote their metastatic ability in vitro and in vivo.We further identified that miR-22-3p,a tumor suppressor micro-RNA,was lowly expressed in breast cancer and directly targeted NLRP3.Downregulation of miR-22-3p upregulated NLRP3/caspase-1/IL-1? signaling pathway,resulting in promote epithelial mesenchymal transformation of breast cancer and then increase the ability of tumor metastasis.Conversely,increasing the expression of miR-22-3p can significantly weaken the ability of epithelial mesenchymal transformation and metastasis of breast cancer in vitro and in vivo.ConclusionmiR-22-3p negatively regulates the role of NLRP3/Caspase-1/IL-1? axis in invasion and metastasis of breast cancer.