| Summary: | 碩士 === 國立臺灣大學 === 生命科學系 === 106 === Lung cancer is the leading cause of cancer death worldwide, and the 5-year survival of lung cancer patients is only 12% after traditional treatments. A revolutionary therapy of cancer called immunotherapy uses the natural capability of immune system to detect and destroy abnormal cells and to prevent cancer development. Since the purpose of immunotherapy is enhancing cytotoxic specificity for tumors, it is important for immunotherapy to find a potential target gene that possesses positive immunomodulatory properties against cancer. Our previous study indicated that semaphorin 6A (SEMA6A) was down-regulated in lung cancer tissue. Moreover, semaphorin family was reported for its immunoregulatory properties in the past studies. However, the effect of SEMA6A on immunity is still unclear. In our pilot study, we isolated mouse splenocytes and co-cultured them with overexpressing SEMA6A human lung cancer cell lines. SEMA6A increased the proportion of T-cell and the migration ability of splenocytes. Furthermore, we analyzed the combined effect of SEMA6A and SEMA3A on patient’s survival by Kaplan-Meier survival curves because SEMA6A and SEMA3A were demonstrated to have the same receptors: Plexin A2 and Plexin A4. The data shows that poor survival rate is significant in patients who have low expressions of SEMA6A and high expression of SEMA3A (p<0.01) while the other combinations of SEMA6A and SEMA3A expressions do not significantly influence the survival of patients. Accordingly, we aimed to study the characteristics of SEMA6A on regulation of immunity ex vivo and the interaction of SEMA6A and SEMA3A in immunity. In order to avoid the influence of endogenous SEMA3A, at first, we knocked down the expression of SEMA3A in mouse lung cancer cell, KLN205. Mouse splenocytes were subsequently isolated and co-cultured with different condition of KLN205 and divided into four groups: Control, SEMA6A, SEMA3A, SEMA6A+SEMA3A. After three or nine days of cultivation, we compared the migration, proliferation, cytotoxic activity of splenocytes between the groups and predicted the immune cells that might be regulated by SEMA6A and SEMA3A using ImmQuant and GSEA. The results indicated that SEMA6A could enhance the cell number and migration ability of splenocytes and reduce proliferation of T regulatory cells compared to the control after nine days. Besides, SEMA6A could extenuate the suppressive effect of SEMA3A in proliferation and cytotoxic capability of T cytotoxic cells. The suppressive effect of SEMA3A on cytotoxic activity of natural killer cells was also extenuated by SEMA6A. Finally, we analyzed gene expressions in these splenocytes utlizing microarray. Based on the microarray results, we predicted that SEMA6A could induce the activity of dendritic cells and attenuate the suppressive effect of SEMA3A in B cells using ImmQuant and GSEA software. However, there was no significant effect of SEMA6A on M1 and M2 macrophages. In conclusion, SEMA6A could induce anti-cancer immunity through either directly regulating the signialing pathway of immune cells or reducing the immune inhibition of SEMA3A. Thus, SEMA6A may be a potential target for cancer immunotherapy in the future.
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