Post-transcriptional Regulation Of PDGFC By RNA Binding Protein HuR In Breast Cancer Cell

Breast cancer is one of the most common cancers for women, with the highest morbidity in female cancer and the second highest death rate but lung cancer. When they go to the doctors, metastasis has happened to most patients, so it becomes the “first killer” of women. The genesis and development of breast cancer is the process participated by many factors, whose pathogenesis is not completely understood yet, but relevant signal path chaos and multigene expression dysregulation are among the most essential reasons, so research on gene expression in breast cancer evolution process is of important theoretical significance and clinical value to the diagnosis and treatment of breast cancer.Platelet-derived growth factor(PDGF), mainly constituted by PDGFA, B, C, D, produces five forms of PDGF-AA,-AB,-BB,-CC and-DD through forming hetero- or homo-dimers. PDGFR-α and PDGFR-β, which are the receptor of PDGF, has abundant expressions in cancer cell and matrix cell. When PDGF is combined with its receptor PDGFR-α and PDGFR-β, it can activate downstream signal to exert its biological function.Platelet-derived growth factor C is the new member of PDGF family, which is expressed in many normal and neoplastic tissues like breast cancer, and was originally found in blood platelet α particle. The fibroblast of cancer matrix cell can express its acceptor a lot, and activated acceptor can activate downstream tyrosine kinases, which participate in the secretion of kinds of cytokines and the formation of tumor microenvironment. However, the research on the action mechanism of PDGC in cancer matrix cell is relatively few. The current study found that PDGFC has important effect in promoting angiogenesis, and overexpressed PDGFC can promote vascular anomaly, and its expression has outstanding effect in the development, progression and metastasis of breast cancer. Nevertheless, the specific mechanism PDGFC regulation of breast cancer remains elusive, so in-depth exploration on its regulatory mechanism is the key point to understand the pathogenesis of breast cancer.Human antigen R is the member of embryonic lethal abnormal vision(ELAV) gene, which includes Hu R, Hu B, Hu C and Hu D, and they mainly regulate the expression of target gene through post-transcriptional mechanism. Hu R is m RNA binding protein which is most sufficiently researched in ELAVL family, is widely expressed in organism histocyte, and is mainly localized in cell nucleus. The cytoplasmic expression of Hu R increases obviously when cells are stimulated by anoxia, inflammatory cytokines and other factors. The researches in recent years show that Hu R protein is the important regulator of immune cells, muscle differentiation, cell division, senility and other vital movements, and is highly activated in metastatic breast cancer. The overexpression of Hu R in breast cancer is closely related with the size of cancer, histological differentiation, survival rate and so on. Our preliminary study also shows that Hu R can strengthen the expression of Snail and promote the transformation of breast cancer. All of these information highly indicate that Hu R may regulate some downstream target gene, and participate in the vicious transformation of breast cancer through autocrine or paracrine. So does Hu R regulate the expression of PDGFC in the development and progression of breast cancer? What is the underlying mechanism? These are the problems that this research is going to solve.More and more research shows that post-transcriptional control of gene expression is fulfilled by the mediation of certain kind of RNA binding protein and mi RNA. In the expression and control of gene, post-transcriptional control, as a kind of accurate control mode, has an important effect in gene expression and the determination of cell’s destiny. RNA binding protein Hu R plays an important effect in the manufacture, embellishing, stability and other aspects through the association with target gene m RNA, and leads to the relevant biological dysfunction of target gene at last.This study aims to dissect the regulatory mechanism of PDGFC. Combining with literature and bioinformatics analysis, we found that 3’ untranslated region of PDGFC has the binding site of Hu R, which indicates that PDGFC may be the target gene of Hu R and be regulated at the post-transcriptional level. Based on the hypothesis above, we have demonstrated the Hu R regulation of PDGFC through real-time PCR, Western blot, RNA-IP, reporter gene system and other experiments, and provided novel insight into the effect of PDGFC in the development and prognosis of breast cancer.After research, we have got following preliminary conclusions:1. PDGFC shows high expression in breast cancer tissue and cell, and is related with patient’s prognosis and biological behavior of cancer cell.2. In breast cancer cell, PDGFC is positively correlated with Hu R. The control of PDGFC happens at the post-transcriptinal level, and the predictive analysis software shows that there are Hu R binding sites in PDGFC 3’UTR.3. Hu R up-regulate the expression of PDGFC through binding to PDGFC m RNA 3’UTR.4. Stress abduction Hu R in breast cancer up-regulate PDGFC. H2O2 excitation and UV exposure of breast cancer cell induce Hu R and consequently up-regulate PDGFC.In conclusion, this study unraveled the relationship between PDGFC in breast cancer cell and Hu R expression, had in-depth discussion on its regulatory mechanism and found that Hu R up-regulate PDGFC through binding to its 3’UTR. Hu R/PDGFC promotes the proliferation and invasion of breast cancer cells. This study revealed the molecular mechanism for Hu R to regulate PDGFC posttranscriptionally, and provided rationale for the development of strategies in the clinical diagnosis and treatment for breast cancer.