The Expression Of MALAT1 In Breast Cancer Plasma And Its Regulation Mechanism On The Proliferation Of ER-positive Cells

Objective:To investigate the level of plasma MALAT1 in breast cancer(BC)patients and its clinical significance.Methods:Different fragment expression levels of plasma MALAT1 were detected from 10 healthy controls.The expressions of GAPDH and MALAT1 of plasma samples collected from 102 preoperative breast cancer patients,64 postoperative breast cancer patients,47 breast benign tumor patients and 50 healthy controls were determined by RT-qPCR.The potential association between plasma GAPDH levels and cases'clinicopathologic features was analyzed to evaluate the stability of GAPDH.The diagnostic efficiency of MALAT1,CA153 and CEA for breast cancer was tested through constructing Receiver operating characteristic(ROC)curve.Meanwhile,the association between MALAT1 levels and the clinicopathologic features and the expressions of MALAT1 between preoperative and postoperative BC patients were analyzed.Results:GAPDH level was stable in female plasma and was not affected by age and pathology(P>0.05).GAPDH can be used as a reference for the detection of plasma lncRNAs in our paper.The levels of different MALAT1 fragments were inconsistent(x2=27.042,P<0.001).Levels of MALAT1 were significantly elevated in preoperative BC patients[5.58(2.17?12.34)]compared with breast benign tumor patients and healthy controls[1.08(0.61?2.58)(Z=6.209,P<0.001),1.63(0.98?3.51)(Z=4.871,P<0.001)].However,there was no significantly difference between breast benign tumor patients and healthy controls(Z=-1.675,P =0.094).The MALAT1 levels of low grade patients(grade ? and ?)were higher than those of breast benign tumor patients(Z=5.593,P<0.001).The relative expression of MALAT1 in postoperative plasma was significantly reduced(Z=2.248,P =0.025).Area under the ROC curve of MALAT1,CA153 and CEA were 0.744,0.619 and 0.553 respectively.The sensitivity and specificity were 54.1%,60.0%,70.0%and 86.3%,66.7%,44.1%respectively.The levels of MALAT1 were associated with TNM stage(Z=-1.982,P =0.047),lymph node metastasis(Z=-2.186,P =0.029)and tumor differentiation(Z=-2.435,P =0.015).Conclusion:Plasma MALAT1 may be an important basis for the diagnosis of breast cancer.Objective:To investigate the potential mechanism of MALAT1 involved in the regulation of ER-positive breast cancer cells proliferation.Methods:ER-positive breast cancer and adjacent tissues of 20 patients in Jiangsu Cancer Hospital during June 2017 to January 2018 were collected.The levels of MALAT1 and miR-503-5p were measured by RT-qPCR.The viability of MCF7 and T47D cells treated with siRNA(small interfering RNA,siRNA)/negative control(si-NC),miRNA/negative control(miRNA NC)or calycosin was quantified using cell counting kit-8(CCK-8)assay and clone formation assay.By luciferase reporter assay,the interaction between miR-503-5p and MALAT1 was detected.ER? protein levels in MCF7 cells treated with calycosin were tested via western blot analysis.Chromatin immunoprecipitation Chip assay was used to detect whether the transcription factor ER? regulated the transcription of MALAT1 gene in MCF7 cells.Results:MALAT1 was highly expressed in ER-positive breast cancer tissues(P<0.05).Knockdown of MALAT1 significantly inhibited ER-positive BC cells proliferation(P<0.05).Meanwhile,we found that calycosin inhibited proliferation of ER-positive breast cancer cells more significantly compared with ER-negative breast cancer cells(P<0.05).The Chip results indicated that there was a binding site of transcription factor ER? in the MALAT1 promoter region at-816?-562.Calycosin increased the binding of ER? to this region in MCF7 cells(P<0.05).miR-503-5p was markedly decreased in ER-positive breast cancer tissues compared with those in adjacent tissues(P<0.05).Overexpression of miR-503-5p inhibited ER-positive BC cells proliferation(P<0.05).By computational analysis followed by luciferase reporter assay,the results revealed that MALAT1 could bind to miR-503-5p directly(P<0.05).Conclusion:Calycosin may inhibit proliferation of ER-positive breast cancer cells through ER?-MALAT1-miR-503-5p signaling pathway.