c-Src 通过改变细胞代谢模式促进肿瘤发生的分子机理

As the first proto-oncogene identified in mammalian cell, c-src encodes a tyrosine kinase c-Src whose overexpression or overactivation plays key roles in tumorigenesis and progression. Warburg effect is a hallmark of tumor metabolism. It is unknown whether c-Src can promote tumorigenesis by directly regulating Warburg effect. Our preliminary data showed that c-Src could interact with HK2, an enzyme catalyzing a committed step in glycolysis. Intriguingly, c-Src could robustly phosphorylate HK2 and thus stimulate its kinase activity to promote glycolysis, cell proliferation and the growth of xenograft tumor. In this project we will identify c-Src phosphorylation sites on HK2 and create point muations of these sites accordingly. We will also stably express these mutatnts in cancer cell lines with wild type HK2 knocked down to further investigate how the mutations influence enzyme activity of HK2, cell proliferation and the growth of xenograft tumor. In addtion, we will try to make phosphorylation antibodies against c-Src phosphorylation sites on HK2 and detect phosphorylation level of HK2 in clinical samples by immunohistochemistry and western blot to determine the correlation between HK2 phosphoryaltion and the types, grades and prognosis of cancers. All together, our reserch may clarify the molecular mechanism by which c-Src promotes Warburg effect and thus tumorigenesis. We may also find a phosphorylation antibody would be used for diagnosis and evaluation of prognosis of cancers.

c-Src基因是在哺乳动物中发现的第一个原癌基因，其蛋白产物c-Src是一种酪氨酸激酶，该酶过度激活或高表达在肿瘤发生发展中起重要作用。Warburg效应是肿瘤代谢的一大特点，目前仍不清楚c-Src是否能通过直接调节Warburg效应促进肿瘤发生。在前期研究中我们发现c-Src和糖酵解中的限速酶HK2有很强的相互作用，且c-Src能磷酸化HK2，并激活其酶活性，增强糖酵解的速率，促进肿瘤细胞增殖及移植瘤生长。在该项目中我们将进一步确定HK2上c-Src的磷酸化位点；在敲低HK2的细胞中稳定表达其磷酸化位点的突变体，研究突变对HK2酶活性、细胞增殖及移植瘤形成的影响；制备HK2磷酸化位点的抗体，分析临床肿瘤标本中HK2的磷酸化与肿瘤的分型、分级 及预后之间的关系。研究有望揭示c-Src通过调节HK2促进Warburg 效应及肿瘤发生的分子机理，发现一种用于肿瘤诊断及预后评估的磷酸化抗体。

c-src是首个在哺乳动物细胞内被发现与病毒型癌基因v-src同源的原癌基因，其编码的蛋白质c-Src是一个非受体型的酪氨酸激酶。蛋白水平升高或激酶活性的增加导致的c-Src的过度激活能促进多种肿瘤的发生、发展以及转移。肿瘤细胞更依赖于糖酵解而非氧化磷酸化供能已被大家所公认，但是c-Src是否调节了肿瘤细胞这种代谢转变还不清楚。在本项目中，我们发现c-Src能够和己糖激酶HK2相互作用，并且磷酸化HK2的酪氨酸686位点。通过检测己糖激酶的催化活性，我们发现c-Src介导的酪氨酸磷酸化修饰使得HK2的酶活性大大增加，能够更快速的将葡萄糖转化为6-磷酸葡萄糖。HK2上被c-Src磷酸化的酪氨酸位点进行突变会显著削弱c-Src促进的糖酵解、细胞增殖、以及移植瘤的生长。综上，本项目的研究揭示了c-Src促进肿瘤发生和转移的新的机理，对开发新的肿瘤治疗药物提供了理论依据。