Molecular Mechanism Of P21^CIP1 Maintaining Breast Cancer Stem Cell Characteristics

In recent years,cancer stem cells have been a hot research area,but the mechanism of its existence has not been fully elucidated.Breast cancer is the highest incidence of malignant tumors in women.Although its malignancy and mortality are lower than other malignant tumors,its threat to women's health cannot be ignored.Studies have shown that there are breast cancer stem cells in breast cancer that can self-renew and can divide asymmetrically.They have a small proportion in tumors but are closely related to tumor growth,metastasis and recurrence.p21 is a direct downstream gene of TP53.It is considered to be part of the tumor suppressor pathway,but some evidences suggest that the expression of p21 protein maintains the steady state of cancer stem cells and protects them from environmental disturbances and can be used as a key gene for cancer stem cell maintenance.In view of the harm of breast cancer,this study studied the relationship between p21 gene and breast cancer stem cells and the mechanism of p21 gene in breast cancer stem cells.In order to better understand the occurrence and development of breast cancer,recurrence and targeted therapy provide new reference and direction.The lentiviral vector was used to knock down the expression of the p21 gene in breast cancer cells 3475,MCF-7 and MDA-MB-231.The survival rate,migration ability and stem-related gene expression of knockdown p21 gene breast cancer cells were detected by MTT cell activity assay,cell scratch healing,crystal violet staining,Western Blot and qPCR,respectively.The results showed that the interference with p21 expression increased cell proliferation,increased migration ability and decreased expression of stem genes such as CD90,OCT4 and NANOG,confirming the promotion of p21 and breast cancer stem cells.Furthermore,we performed transcriptome sequencing of p21 shRNA cell lines and analyzed differentially expressed genes and differentially altered splicing.The results suggest that p21 knockdown has an effect on maintaining plasma membrane composition,controlling cell signaling,and DNA transcription.Finally,qPCR was used to verify the difference in gene expression and cell sternness,which was closely related to the changes of key genes in the wnt pathway,and the DNA repair and endocytosis functions were verified by conventional chemotherapy drugs and recombinant vaccinia virus.It was found that knocking down p21 made the cells sensitive to DNA damage,while the sensitivity to recombinant vaccinia virus with endocytosis as the main entry mechanism was reduced.Finally,we found that p21 regulates the transcription of the stem maintenance effector gene in tumor cells on the one hand and affects endocytosis on the other hand to regulate cell signal transduction in response to external signal regulation.The two effects combine to maintain the sternness of breast cancer stem cells.This result can provide experience for the study of cancer stem cells and provide new ideas for the treatment of tumors.