Inhibition of SOX2 induces cell apoptosis and G1/S arrest in Ewing’s sarcoma through the PI3K/Akt pathway

Abstract

BackgroundEwing’s sarcoma is an aggressive bone and soft tissue tumor with a high incidence in children and adolescents. Due to its high malignancy and poor prognosis, identification of novel biomarkers for intervention therapies is necessary to improve outcome. The EWS/FLI1 fusion gene is a characteristic of Ewing’s sarcoma in most cases. Sex determining region Y-box 2 (SOX2) is a primary target of EWS/FLI1. It has been identified as an oncogene and linked to apoptotic resistance in several types of cancer. However, its role and regulatory mechanisms in Ewing’s sarcoma are largely unknown.MethodsWe systematically investigated the role of SOX2 in Ewing’s sarcoma cell lines, human tissue samples and xenograft models. The expression of SOX2 was detected in Ewing’s sarcoma samples by WB and IHC. siRNAs were used to knockdown EWS/FLI1 and SOX2 in A673 and RD-ES cell lines with the efficiencies tested by qRT-PCR and WB. The effect of SOX2 on cell cycle and apoptosis was determined by Flow cytometric and TUNEL assays. Akt overexpression was performed with plasmid. The protein expression of the corresponding factors was examined by WB analysis. Inhibition of SOX2 in vivo was performed by siRNA against SOX2 in xenograft models, and the protein expression of the regulators testified in vitro was examined in xenograft tumors by IHC and WB.ResultsThe results confirmed that SOX2 was highly expressed in Ewing’s sarcoma and was the target of EWS/FLI1. SOX2 advanced Ewing’s sarcoma cell survival and proliferation by regulating p21, p27 and cyclin-E to facilitate G1/S phase transition and mediating caspase-3, PARP via both extrinsic (Fas and caspase-8) and intrinsic (caspase-9, Bad, Bcl-2 and XIAP) apoptotic pathways to restrain cell apoptotsis. Additionally, SOX2 regulated the cell-cycle progression and apoptosis via activation of the PI3K/Akt signaling pathway. The mechanisms were proved both in vitro and in vivo.ConclusionsThe results demonstrate that SOX2 played a central role in promoting Ewing’s sarcoma cell proliferation in vitro and in vivo with the underlying mechanisms expounded. These findings suggest that SOX2 may serve as a potential biomarker for targeted intervention in Ewing’s sarcoma.

Sox2‐dependent inhibition of p21 is associated with poor prognosis of endometrial cancer

“…SOX2 tightly regulates cancer cell proliferation, apoptotic signaling, invasion, and migration in many cancer types . Previous studies have shown that SOX2 is required for positive cell cycle progression and the expression of some cell cycle regulatory genes in various cancer cells.…”

“…These transcriptional factors regulating the pluripotency of normal stem cells are essential for maintenance of several types of cancer cells . In addition, SOX2 has been reported to be essential for cell survival and cancer progression and initiation in many types of cancers, including glioblastoma, breast cancer, pancreatic cancer, gastric cancer, melanoma, lung cancer, osteosarcoma, and Ewing sarcoma . Recently, we also demonstrated that SOX2 expression was required for the growth and survival of ovarian cancer cells .…”

“…(16) In addition, SOX2 has been reported to be essential for cell survival and cancer progression and initiation in many types of cancers, including glioblastoma, (17) breast cancer, (18) pancreatic cancer, (19,20) gastric cancer, (21) melanoma, (22) lung cancer, (23) osteosarcoma, (24) and Ewing sarcoma. (25) Recently, we also demonstrated that SOX2 expression was required for the growth and survival of ovarian cancer cells. (26) In most types of cancers, SOX2 acts as an oncogenic transcriptional factor, and thus it may become a novel therapeutic target in these cancers.…”

A Novel Notch–YAP Circuit Drives Stemness and Tumorigenesis in Embryonal Rhabdomyosarcoma

“…YAP (Cell Signaling #4912, 1:40) and SOX2 IHC (Cell Signaling #3579, 1:100) were performed as described (5,55). Ki67 (Dako #M7240) staining was performed per the manufacturer’s protocol.…”

FOXM1 in sarcoma: role in cell cycle, pluripotency genes and stem cell pathways

“…In Ewing sarcoma SOX2 enables cell proliferation and survival by regulating p27, p21 and cyclin E to facilitate G1/S phase transition. In a systematic evaluation of Ewing sarcoma cell lines, human samples and xenograft models siRNA mediated inhibition of SOX2 induces apoptosis and G1/S phase arrest [51]. Ewing sarcoma expresses neurogenic genes, and the postulated cell of origin of Ewing sarcoma is either a mesenchymal stem cell or primitive early neuro-ectodermal cell.…”