“肿瘤递质”谷氨酸在胃癌转移中的作用及机制研究

With the deepening of the research on tumor invasion and metastasis, we putted forward that glutamate in tumor is close to conform the basic condition of acting as a “tumor neurotransmitter” for the first time. However, whether glutamate involves in invasion and metastasis of gastric cancer and the mechanism are still unknown. We found that metastasis gastric cancer cells could secret large amounts of glutamate and glutamate could promote invasion and metastasis in gastric cancer cells via using micro dialysis technology and function experiments in vitro, which suggested that there was a phenomenon of information exchange between gastric cancer cells. Further experiments results showed that NR1 subunit of NMDA receptor was high expression in gastric cancer cells; gastric cancer cells exposured to exogenous glutamate or NMDA could mediate the Ca2+ inflowing into cells and activated the downstream channel to promote the occurrence of gastric cancer metastasis. NMDA receptor antagonist MK801 not only blocked the inward currents, but also reduced the invasion ability in gastric cancer cells. We will conduct an in-depth study of the feasibility of glutamate as a “tumor neurotransmitter” using molecular biology and electrophysiology experiments in this project and fully prove gastric cancer can generate information exchange through “tumor neurotransmitter” and produce certain effect, which is a new starting point for cancer research. At the same time, we will further verify the mechanism of glutamate promoting gastric cancer metastasis and antagonist effects, which in order to provide new idea and new targets for gastric cancer treatment.

随着对肿瘤侵袭转移研究的深入，我们首次提出谷氨酸在肿瘤中已接近符合充当一个“肿瘤递质”的基本条件，但谷氨酸是否参与了胃癌的转移其机制是什么尚不清楚。微透析及体外功能实验发现胃癌高转移细胞可分泌大量谷氨酸，且谷氨酸可促进胃癌细胞的侵袭转移，说明胃癌细胞间存在信息交换现象。为深入研究谷氨酸在胃癌转移中的作用机制，进一步实验发现，胃癌细胞上主要表达NMDA受体的NR1亚基，外源性给予谷氨酸或NMDA，胃癌细胞可介导Ca2+内流，激活下游通路促进胃癌转移的发生。NMDA受体拮抗剂MK801不但能阻断内向电流而且也可降低胃癌细胞的侵袭能力。本项目拟借助分子生物学、电生理学等实验技术深入研究谷氨酸作为“肿瘤递质”的可行性，充分证明胃癌可通过“肿瘤递质”进行信息交换并产生一定作用，这无疑是肿瘤研究的新切入点。同时进一步验证谷氨酸促进胃癌转移的作用机制及拮抗剂的作用效果，为胃癌治疗提供新思路新靶点。

肿瘤细胞之间是否发生信息传递以及其产生信息传递的意义在肿瘤的研究中至关重要。我们的工作表明，胃癌中存在谷氨酸特异性受体的表达。我们检测了人胃癌细胞中NMDA受体的表达情况及胃癌细胞中NMDA受体诱发电流的变化，明确NMDA受体在胃癌的侵袭和转移中的调控作用。免疫组化的结果提示谷氨酸受体NR1亚基在胃癌中的表达与侵袭和转移相关的临床资料水平有关，进一步研究表明NR1亚基在胃癌细胞中表达升高，谷氨酸与其结合不但可以促进胃癌细胞侵袭转移的发生，而且可以使胃癌细胞产生NMDA受体诱发电流，特异性受体阻断剂MK801可部分阻断其作用。同时，为了进一步研究神经元与肿瘤之间是否存在信息传递，我们进一步研究了突触前离子型受体的可塑性变化，应用转基因动物，特异性敲除突触前结构的NR1亚基，从而研究突触前NMDA受体在脊髓背角浅层突触可塑性变化中的作用。我们发现脊髓背角突触前NMDA受体在长时程增强的诱导和表达机制中具有明确的作用。我们进一步研究发现细胞趋化因子CCL2可显著增强脊髓背角浅层神经元中NMDA受体诱发电流。通过研究CCL2在脊髓背角的作用机制，我们发现CCL2可以增强脊髓背角SOM+神经元的NMDA诱发电流，在脊髓背根刺激条件下CCL2也可增强突触诱发NMDA电流。同时，应用钙成像技术，我们进一步发现CCL2可以显著增强突触前NMDA诱发的钙变化。提示谷氨酸作为肿瘤递质，可能通过CCL2/CCR2发挥作用。