Fbxw7通过负调控SOX10抑制肿瘤增殖及转移的机制研究

SOX10 was reported to be up-regulated in multiple tumors including melanoma and glioma and the up-regulation of SOX10 may contribute to the increased proliferating and migratory capacity of tumor cells. However, the mechanism that SOX10 is up-regulated in these cancers remains unknown. Using tandem affinity purification and mass spectra (TAP-MS) assay we have identified a SOX10 associating protein Fbxw7, the subunit responsible for the substrates recruitment of SCF-Fbxw7 E3 ubiquitin ligase. The interaction between SOX10 and Fbxw7 was confirmed using Co-IP. Functionally, overexpression of Fbxw7 increased the ubiquitination level of SOX10 and promoted the degradation of SOX10. These data indicate that SCF-Fbxw7 is the E3 ubiquitin ligase which meidates the degradation of SOX10. In this project, we will examine whether Fbxw7 negatively regulates the stability of SOX10 in tumor cells including melanoma and glioma. We will also detect the mutation of Fbxw7 and analyze the correlation between the mutation of Fbxw7 and the protein level of SOX10 in tumor samples. In addition, we will determine whether the proteins level of Fbxw7 is inversely correlated with SOX10 in tumor samples. Finally, we will test the effect of the dysregulation of Fbxw7-SOX10 pathway on the proliferating, migratory and invasive ability of tumors. Taken together, in this project we hope to demonstrate the common mechanism by which SOX10 is up-regulated in multiple tumors and reveal the important role of Fbxw7-SOX10 signal pathway in modulating the progression of tumors.

SOX10在黑色素瘤以及神经胶质瘤等多种肿瘤中表达上调，并促进肿瘤的增殖、迁移与侵袭。但是SOX10在肿瘤中表达上调的机理尚不明确。本项目前期通过串联亲和纯化-质谱法发现与SOX10相互作用蛋白Fbxw7。功能研究发现，高表达Fbxw7可明显增加SOX10蛋白的泛素化水平，促进SOX10蛋白降解：提示Fbxw7是介导SOX10降解的E3泛素连接酶。Fbxw7是一个重要的肿瘤抑制因子，在多种肿瘤中表达下调或突变失活。因此我们提出科学假设： Fbxw7可通过泛素化介导的降解作用调控SOX10的表达，在黑色素瘤等一类肿瘤中，Fbxw7表达下调或突变失活导致SOX10表达上调，进而加速肿瘤的增殖与转移。接下来我们将以黑色素瘤与神经胶质瘤为模型，检测Fbxw7-SOX10信号通路在调控肿瘤细胞增殖、迁移和侵袭中的作用；通过突变分析和免疫组化在临床标本中检测Fbxw7-SOX10表达相关性及临床意义。

SOX10在黑色素瘤以及神经胶质瘤等多种肿瘤中表达上调，并促进肿瘤的增殖、迁移与侵袭。但是SOX10在黑色素瘤中表达上调的机理尚不明确。本项目通过串联亲和纯化-质谱鉴定Fbxw7与SOX10具有相互作用。通过co-IP进一步验证SOX10与Fbxw7具有相互作用；通过缺失突变结合co-IP鉴定Fbxw7的WD40结构域通过SOX10的CPD基序与SOX10相互作用。进一步分析发现Fbxw7作为SOX10的E3泛素连接酶，调控SOX10蛋白的稳定性，从而调控SOX10在黑色素瘤中的表达。GSK3-B介导SOX10 CBD基序的磷酸化，促进Fbxw7对SOX10的泛素化降解。黑色素瘤中敲低Fbxw7上调SOX10蛋白及其下游蛋白MIA的表达，导致黑色素瘤细胞的迁移能力上升；而高表达Fbxw7下调SOX10及MIA的表达， 抑制黑色素瘤迁移能力；通过拯救（rescue）实验证明SOX10在介导Fbxw7的转移抑制中起着关键作用。通过本项目的研究，我们阐述了SOX10在黑色素瘤中表达上调的机制；发现了Fbxw7新的底物。

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