SALL4 Suppresses PTEN Expression To Promote Glioma Cell Proliferation By PI3K/AKT Signaling Pathway

Objective:In resent year, although rapid development in healthcare, including early detection and diagnosis, major resection with the help of microsurgery,even chemoradiotherapy after surgery and immunotherapy,but the prognosis and living quality remain undesirable because of rapid proliferation, and their average survival of glioblastoma(GBM) is 15 to 18 months. Many causes should be account for tumor formation, such as genetic mutation, drugs, physical and chemical element inheritance, among them the activation of oncogene and inactivation of tumor suppressor gene has been generally recognized by investigator. A resent research found that a newly discovered oncogene, salt human-like genes(SALL4), the human homolog of Drosophilagene spalt has the function of tumor regulation and might be a new maker for evaluating the prognosis of tumor. SALL4 could code a zinc finger protein transcription factors, which was located in human chromosome 20q13, including SALL4 A and SALL4 B two kinds of production. What’s more,scientists had found that SALL4 had the ability of maintain embryonic stem cell pluripotency and self-renewal, which was closely related to tumor genesis and progression, leukemia, hepatocellular, carcinoma, gastric cancer, esophageal carcinoma, lung cancer and many other common malignant tumor. An obvious decreasing of proliferation, increasing of apoptosis and suppression of invasive ability were observed in some malignant tumor, and for a hepatocellular patient, high level of SALL4 means a shorter survival and poor prognosis. Loss of function or mutation of tumor suppressor gene PTEN also participated in the progression of various malignant tumor, in some carcinoma SALL4 could targeted inhibit the expression of PTEN and play a important role to promote cancer. It is reported that SALL4 has relationship with proliferation and apoptosis in glioma, the specific mechanism was still unclear yet. Thus, this study was conducted to explore the expression of SALL4 in glioma by qPCR. Subsequently, molecular functions of SALL4 in glioma cell lines were studied by using sall4-siRNA and PTEN inhibitor phen(bpv) in glioblastoma(GBM) U87 and U251 cell lines.69 glioma tissue which were parts of samples in recent 3 years collected from the First Affiliated Hospital of Soochow University, by quantitative PCR(qPCR) we detected the expression of SALL4 in glioma. Subsequently, appropriate glioma cells line were screened out for the present study. Then, we transfected the U87 and U251 cells line with SALL4-siRNA,and phen(bpv) were used as contrast, cell proliferation, the cell cycle were assessed to explain the function of SALL4 in glioma, and Western Blot was used to detect the related protein(such as PTEN,PI3 K,P-PI3 K,AKT,P-AKT,cyclin D1.)expression of PI3K/AKT signaling pathway,Results1. Expression of SALL4 in glioma samples and glioma cell linesTo have a better understand of the expression of SALL4 in glioma samples and non-cancerous brain tissues, qPCR was assessed in 69 gliomas samples and 6 non-cancerous brain tissues. Results suggested that the expression of SALL4 was significantly higher in glioma samples than non-cancerous brain tissues(P < 0.01), and increased along with the increasing degree of malignancy in glioma,that was to say the higher grade means the higher expression of SALL4.2. PTEN was increased when down-regulation the expression of SALL4qPCR and Western Blot data showed the expression of PTEN was obvious increased both in mRNA and protein level as silencing SALL4 by transfected with SALL4-siRNA. however, the suppression effectiveness was reversed to a great extent when PTEN inhibitor phen(bpv) was added.3. SALL4-siRNA depressed proliferation in glioma cell lines U87 and U251The SALL4 expression was decreased after transfected with SALL4-siRNA, as a result, cell proliferation was distinctly decreased in glioma cells. And further cell cycle model was conducted, the results showed that G1 phase was increased and S phase was decreased in cells whose SALL4 was blocked, but in phen(bpv) group, the repression effect was significantly relieved.4. The related protein of PTEN/PI3K/AKT signaling pathway was examined in cells down-regulation SALL4Western blot results suggested that PTEN protein was increased and the protein phosphaorylation was suppressed after down-regulation SALL4, the p-PI3 K, p-AKT, Methods cyclin D1 protein in cells transfected with SALL4-siRNA were significantly inferior to cells with Negative control, and in SALL4-siRNA-bpv groups, protein level were fell in between。ConclusionFrom the present study we can see that the expression of SALL4 was higher in glioma samples than non-tumor brain tissues and increased along with the increasing degree of malignancy in glioma. Down-regulation of SALL4 depressed proliferation in glioma cells.Blocking SALL4 could restrain PTEN expression and PI3K/AKT activity in result suppress cell growth in a certain extent.