骨肉瘤是一种在青少年恶性肿瘤中发病率居首位的骨肿瘤，严重危害青少年健康，目前其临床治疗以手术治疗为主，辅以放化疗，但治疗效果并不理想，寻找新的骨肉瘤诊疗方法对保护青少年健康具有重要意义。Tn抗原（即黏蛋白型O-聚糖 GalNAcα1-S/T）与T抗原作为肿瘤标志物之一，与肿瘤的诊断及预后密切相关，Tn抗原是合成T抗原的前体，Tn抗原在T抗原合成酶的作用下形成T抗原。有研究表明T抗原高表达的肿瘤患者预后较Tn抗原高表达者为佳。我们前期研究发现高表达T 抗原合成酶的肿瘤细胞体外能增强肿瘤特异性CD8+细胞增殖，减少CD8+T细胞凋亡。本课题综合已有的研究数据，拟通过上调骨肉瘤细胞中T抗原合成酶的表达水平，促使骨肉瘤细胞中更多的Tn抗原转变为T抗原，观察此种改变对骨肉瘤细胞生物学行为及机体肿瘤免疫能力的影响，并探寻其可能的作用机制，以期为骨肉瘤的治疗提供一个新的靶标。

Osteosarcoma is the most prevalent bone neoplasm among the malignancies in adolescence and has become a major threaten for teenagers' health. In current clinical practice, surgery is still the essential treatment, sometimes combined with adjuvant radiochemotherapy. However, the prognostic of these patients remains far from satisfactory. Thus, development of a more effective approach to treat osteosarcoma has become very urgent and of great importance. Tn antigen and T antigen have been reported as tumor markers served in the neoplasms diagnosis and their levels are closely correlated with disease progression. Tn antigen, the precursor of T antigen, is transformed to T antigen by T antigen-synthase. In addition, it has been demonstrated that high level of T antigen-expression rather than that of Tn antigen is predictor of a better outcome. Moreover, our previous study showed that enhanced expression of T antigen-synthase in tumor cells resulted in significant proliferation and reduced apoptosis of tumor-specific CD8+ T cells in vitro. All the data suggest that T antigen-synthase might play a critical role in malignant pathogenesis. Accordingly, our study is aimed to up-regulate the transformation of Tn antigen to T antigen by enhanced expression of T antigen-synthase. Then we observe the effect of this change to the biological behavior of osteosarcoma cells and to tumor-specific immunity. Furthermore, we will try to elucidate the potential mechanism.