- 學位論文
利用犬隻腫瘤模式探討腫瘤與宿主免疫力之相關性
Investigation of the correlation between tumor and host immunity in canine tumors
摘要
犬傳染性花柳性腫瘤（CTVT）具有特殊的腫瘤生長模式，包括生長期 (progression phase, P phase) 及自然消退期 (spontaneous regression phase, R phase)。先前研究指出，P期的CTVT細胞會製造高濃度的TGF-β以抑制宿主的抗腫瘤免疫反應；而當腫瘤浸潤淋巴球 (tumor infiltrating lymphocytes, TIL)產生大量的IL-6時，則能抗TGF-β的活性，進而回復宿主的免疫反應，以促使腫瘤消退。雖然目前關於CTVT的腫瘤形成機制已有許多發現，如：CTVT具有抑制樹突狀細胞的功能或是會分泌B細胞毒殺因子等。但我們相信，仍有未知的因子參與在該腫瘤與宿主免疫系統的互動中。在本研究中，我們證實了在CTVT的消退期中，其調控型T細胞的比率較P期時為低，且此變化與R期高量表現的IL-6有關。此外，我們首次利用基因微陣列(GeneChipR Canine Genome 2.0 Arrays Affymetrix array)，來比較CTVT P及R期的基因表現變化。其結果顯示，在R期IL-6的升高與TIMD-4, GPNMB 及 PLTP基因的高表現量有正相關性。同時，我們也發現Th17細胞的相關基因會大量表現在R期。綜合前述結果，顯示CTVT的生長可能與調節型T細胞和Th17細胞的數目消長有關。在臨床方面，我們於犬肥大細胞腫瘤及犬淋巴瘤的病犬中檢測Th17細胞及調節型T細胞的比值，發現與健康犬隻相比，腫瘤犬中的Th17細胞皆有顯著性地減少，而調節型T細胞在腫瘤犬中則有顯著性增加，這也證明在犬肥大細胞瘤及犬淋巴瘤中，Th17細胞及調節型T細胞也有不正常的比值。另外，根據基因微陣列分析，我們挑選了幾個在P或R期有大量表現的基因，檢測這些基因是否有可能做為犬腫瘤的生物標記。檢測結果發現CHI3L1可依其表現量來區分惡性犬乳腺腫瘤的級別：在臨床第一期的惡性犬乳腺腫瘤組織中，其CHI3L1的表現量顯著性高於第四、五期；而具有高表現量的CHI3L1病犬，其術後存活時間也顯著性地高於低表現量者。綜合上逑，本研究的結論為：(1) IL-6 在CTVT消退中扮演著重要的角色，因IL-6可回復被TGF-β 所抑制的免疫反應，降低調節型T細胞的產生，且與Th17細胞的增加可能具有相關性。(2) Th17細胞與調節型T細胞異常的比例關係不只在實驗接種的CTVT犬隻中發現，在臨床犬隻腫瘤中也有相同的現象。(3) CHI3L1可做為評估惡性犬乳腺腫瘤預後之因子。
並列摘要
Canine transmissible venereal tumor (CTVT) has a unique growth pattern that includes progression (P) and spontaneous regression (R) phases. Previous studies have indicated that a high concentration of TGF-β suppresses host antitumor immunity in the P phase of CTVT. During the R phase, IL-6 derived from tumor infiltrating lymphocytes antagonizes TGF-β activity and restores immunity, leading to CTVT regression. Although many findings such as B cell cytotoxic molecules or inhibition of dendritic cells have been reported to contribute to CTVT development, it is believed that further investigation is needed to disclose the interaction between tumor growth and host immunity. In this study, we demonstrated that IL-6 diminished regulatory T cell (Treg) generation during the R phase. Moreover, using GeneChipR Canine Genome 2.0 Arrays Affymetrix array, we compared the gene expression profiles of P- and R-phase CTVTs for the first time. The results indicated that TIMD-4, GPNMB and PLTP were associated with IL-6 induction during the R phase. We also found that Th17-related genes were up-regulated in the R phase. The discoveries mentioned here imply that there might be an imbalance between Th17 and Treg that results in CTVT progression. Further, the Th17/Treg imbalance in tumors was also validated in clinical cancer patients. We detected the ratios of Th17 and Treg in dogs suffering from mast cell tumor (MCT) and lymphoma (LSA). The results showed a significant decrease of Th17 and a dramatic increase of Treg in dogs with MCT and LSA. This indicated that abnormal ratios of Th17 and Treg are important in canine tumors. In addition, we chose several genes of high expression in the CTVT P and R phases to examine their possible applications as biomarkers in canine tumors. The results demonstrated that a higher expression of CHI3L1 was found in stage I tumors and favored a good prognosis of malignant canine mammary gland tumor (cMGT). Taken together, the results of this study conclude that: (1) IL-6 plays a key role in CTVT regression, as it antagonizes the immunosuppression of TGF-β, reduces Treg generation, and may increase Th17 cells; (2) The imbalance of Th17/Treg exists not only in an experimental CTVT model, but also in clinical canine tumors, which is relevant to patient prognosis. (3) CHI3L1 is a potential biomarker for the prognosis prediction of malignant cMGT.
參考文獻
延伸閱讀
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