Exploration Of Feature Genes Of Basal Breast Cancer Stem Cells And Their Subtyping Functionality

The high heterogeneity of breast cancer makes different breast cancer subtypes differing in their prognosis and therapies,thus,accurate subtyping is essential in personalized treatment design.Among the subtypes,basal breast cancer represents a particularly challenging subtype with distinctive phenotypic,molecular features and poor prognosis.The concept of cancer stem cells has brought the dawn of the treatment of basal breast cancer.CD44+CD24-/low stem cells are regarded as more metastasis and invasion,which are mainly enriched in basal breast cancer.Therefore,identifying pivotal genes that maintain cancer stem cells features using the CD44+CD24-/low cohort maybe effective to identify biomarkers and new targets of basal breast cancers.In this study,We conducted cancer stem cells sorting and non-stem cells sorting in SUM149 PT and HCC1937 cell lines by flow cytometry.RNA-Seq and a sequential bioinformatics analysis were performed to identify the promissing subtyping genes among differentially expressed genes(DEGs).The candidate genes were validated and the fuctional studies of pivotal genes were carried out in vitro.Main results were listed follows:(1)CD44+CD24-/low stem cell subpopulation was highly expressed in basal breast cancer cell lines(P<0.001)and CD44+CD24-/low stem cells and non-CD44+CD24-/low stem cells were sorted by flow cytometry;(2)After RNA-Seq analysis,there are 134 DEGs shared by SUM149 PT,HCC1937 cancer stem and non stem cells.GO analysis indicated that the most enriched Biological Process,Cellular Component,Molecular Functions were extracellular matrix organization,extracellular region and peroxidase activity,respectively.Moreover,the pathway most enriched for DEGs was Pathway in cancer;(3)The candidate subtyping genes from bioinformatics analysis were validated in 12 different breast cancer cell lines at transcriptional and translational levels.Amoung the 14 candidate genes,FA2 H and IL-6 were found to become promising subtyping marker genes to identify the basal subtype;(4)The siRNA technique was used to silence FA2 H in SKBR3 cells to explore the functional roles of FA2 H on breast cancer stem cell regulation and possible mechanism,and we unveiled that silencing FA2 H gene activated the IL-6/STAT3 axis to increase the expression of cancer stem cells and migration.The effect of IL-6 on the stem cell-related function of breast cancer cells was detected.The results showed that IL-6 could significantly increase the proportion of cancer stem cells and self-renewal in SKBR3 cells(P<0.01).