| Breast cancer is the most common malignancy in women with considerably more than 1.5 million new cases diagnosed worldwide.Breast cancer has been a challenging threat to the public health and the situation is particularly concerning.Based on the expression status of estrogen receptor,progesterone receptor,human epidermal growth factor receptor 2 and Ki-67,breast cancer could be divided into four categories:Luminal A,Luminal B,the Her2-enriched and triple-negative breast cancer subtypes.In recent years,the advanced improvement of early diagnosis and clinical therapy for breast cancer has significantly reduced the mortality of Luminal and HER2 breast cancers.However,the mortality of triple-negative breast cancer remains high,which is still a serious concern.To better individualize the comprehensive therapy and decrease the mortality of cancer and improve the life quality of patients,it is an urgent to have an in-depth knowledge and understanding of the heterogeneity of breast cancer.Besides,finding new biomarkers for triple-negative breast together with fulfillment and improvement of the diagnosis and treatment therapy for specific breast cancer subtypes will be of great significance.Human Pinxl protein,associated with shelterin proteins,is 45KD and consists of 328 amino acids.Currently,increasing studies have revealed that PinX1 is down-regulated in diverse cacers.Besides,PinXl perhaps interacts with human telomere or/and telomerase to suppress the tumor procedure and growth.It has the potential to be a tumor suppressor.Nonetheless,the relationship between PinXl and triple-negative breast cancer is still unclear.In addition,its diagnostic,prognostic and clinicopathological significance in triple-negative breast cancer are to be further explored.In this study,PinXl expression levels of breast cancer tissues and the adjacent normal tissues were investigated by quantitative real-time PCR and immunoblotting assays.The results revealed that both PinXl mRNA and protein expression were down-regulated in breast cancer tissues(P<0.05).Then the immunohistochemistry(IHC)was performed to detect PinXl expression and its clinical significance on a Tissue microarray.Our results showed that,in 59 invasive ductal breast carcinomas,PinXl expression was inversely related to histology grade while it was positively associated with PR status and ER status(P<0.05).However,there was no significant relationship between PinXl expression and other clinicopathological parameters including age at surgery,clinical stage,pT stage,Her2 status and P53 status(P>0.05).Then analyses about the positive staining of PinXl were stratified by different breast cancer subtypes in the breast cancer tissues above.Significantly,PinXl was down-regulated in basal-like/triple-negative breast cancer(P<0.01),which indicated that PinX1 may be correlated with the development and progression of triple-negative breast cancer.To clarify the probable role of PinXl in TNBC,the PinXl knockout and stably over-expressed MDA-MB-231 cell lines were constructed by the CRISPR-Cas9 system and gene transfection.The association of PinXl expression with cell proliferation,migration and apoptosis of MDA-MB-231 were observed by CCK-8 assay,wound healing assay,transwell assay,flow cytometric analyses and immunoblotting of the cleaved casepase-3 protein level.CCK-8 assay results showed that overexpression of PinXl significantly inhibited the proliferation of MDA-MB-231 while PinX1 knockout promoted cell proliferation.The wound healing and transwell assay revealed that migration rate was inhibited when the PinX1 was over-expressed.However,it was significantly reversed when the PinX1 was knockout.Consistently,the flow cytometric analyses revealed that overexpression of PinXl significantly augmented the number of apoptosis cells in MDA-MB-231 while PinX1 knockout markedly decreased the proportion of apoptosis cells.Besides,we observed a higher expression level of cleaved casepase-3 in the PinX1 over-expressed group compared with the negative control.All in all,our results demonstrated that PinXl was significantly down-regulated in breast cancer tissues compared with the normal counterparts.Besides,overexpression of PinXl inhibited the proliferation rates and migration ability of TNBC and increased the apoptosis rates of TNBC.In conclusion,PinX1 significantly plays critical roles in the development and progression of triple-breast cancer,which is promosing to be a potential therapeutic target and molecular biomarker for triple-negative breast cancer. |
PDF Full Text Request