茶氨酸抗肿瘤作用及其机制的研究进展

　　γδT细胞杀伤肿瘤细胞是非MHC限制性的，研究报道在各种实体瘤浸润淋巴细胞中均发现γδT细胞的表达和抗肿瘤效应。临床研究发现，口服茶氨酸可以增强γδT细胞活性，促进γδT细胞分泌IFN-γ [19]，抑制肿瘤。其机理可能是，茶氨酸在肾脏被分解释放出乙胺，乙胺通过抑制甲羟戊酸通路，诱导产生异戊烯焦磷酸(IPP)，IPP是γδT细胞抗原，可以促进γδT细胞增殖[20]。

　　树突状细胞(DC)是功能强大的抗原提呈细胞，具有激活静息型T细胞及诱导初级免疫应答的能力。雷明盛[21]证明茶氨酸可能是通过抑制COX-2的表达，减少内源性的IL-10合成，促使DC成熟，从而促使IL-12分泌，调节IL-10/IL-12的平衡，激活细胞毒性T淋巴细胞(CTL)，促使CTL增殖或穿孔素产生来实现抗癌作用。另外，雷明盛[21]还证明，茶氨酸刺激DC调节T淋巴细胞抑制SCID小鼠肺腺癌移植瘤，可能是通过免疫监视及清除畸变细胞作用，以及下调血管内皮生长因子(VEGF)的表达水平，抑制肿瘤血管形成等机制来实现。

　　茶氨酸的直接抗癌作用研究起步较晚，目前还在初级阶段，相关机制的研究还不够透彻，随着分子生物学技术的发展，一些新的作用位点，越来越多地被发现，通过对免疫调节分子机制，特别是细胞信号传导通路方面更加深入的研究，也许可以从中找到答案。

　　5展望

　　茶氨酸作为茶叶中的功效成分，具有防治肿瘤的活性。茶氨酸与抗肿瘤药物联合作用，能有效地抑制肿瘤生长，阻止肿瘤迁移，降低抗肿瘤药物毒副作用;茶氨酸单独使用可抑制肿瘤细胞浸润和转移。谷氨酸盐载体在茶氨酸生物活性中扮演了重要的角色，茶氨酸通过作用于谷氨酸盐载体，竞争性抑制了肿瘤细胞对谷氨酸盐的吸收，降低了细胞内谷胱甘肽的生物合成，使GS-X生成减少，抗肿瘤药物不能被泵出细胞，在胞内积累，从而增强了抗肿瘤药物的抗癌效果;茶氨酸还可通过调节人体免疫功能单独发挥抗癌作用。

　　化疗是治疗恶性肿瘤的重要手段，因其毒性强，副作用大，使患者的生活质量降低，另外还易产生耐药性，影响治疗效果。人们期望茶氨酸可以作为一种天然药物，应用于临床治疗，减轻癌症患者经济负担，缓解治疗痛苦，提高患者的生活质量。茶氨酸作为一种天然活性物质，其具有广阔的应用前景，值得继续研究与开发。

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