第四章 實驗結果
第四節 實驗結果圖表
B. (S)-HDAC-42
0 20 40 60 80
cells (106 )
0 1 2 3 4 5
0 (μM) 0.1 (μM) 0.25 (μM) 0.5 (μM) 0.75 (μM) 1 (μM)
A.
cell viability (%) 24hr
48hr
cell viability (%) 24hr
48hr
Figure 8. Antiproliferative effect of (S)-HDAC-42 in multiple myeloma cell lines.
(A. IM-9, B. RPMI-8266, C. U266) (n=3)
表十三、 The IC50 values of (S)-HDAC-42 versus SAHA in MTS assay
Figure 9. Effect of (S)-HDAC-42 on apoptosis by flow cytometry. (n=3) (S)-HDAC-42 (μM)
D 0.1 0.25
0.5 0.75 1
1.3% 7.3%
79.3% 12.1%
1.1% 8.6%
76.2% 14.2%
1.2% 6.2%
79.4% 13.2%
2.5% 12.9%
58.8% 25.7%
3.5% 15.6%
47.8% 33.2%
3.6% 25.6%
3.7% 67.1%
Figure 10. Evidence of apoptosis for (S)-HDAC-42 induced cell death by comet assay.
DMSO 0.1 μM 0.25 μM
0.5 μM 0.75 μM 1 μM
(S)-HDAC-42
Figure 11. Evidence of apoptosis for (S)-HDAC-42 induced cell death by TUNEL assay.
DMSO 0.1 μM 0.25 μM
0.5 μM 0.75 μM 1 μM
(S)-HDAC-42
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 ( μM)
HDAC 1
HDAC 4
100 104 102 96.6 68.9 52.1 %
100 104.6 102.6 96.7 68.9 52 %
Acyl-Histone3
1 1.03 1.05 1.24 1.3 1.33 Fold
α-tublin
Figure 12. The effects of (S)-HDAC-42 on the expression level of HDAC related proteins (HDAC1, HDAC4, and acyl-histone3) in multiple myeloma cells.
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 ( μM )
Caspase-3
β-actin
1 1.2 1.4 1.9 2.3 2.1 Fold
Caspase-8
1 1 1 1 1 1 Fold
PARP
1 1 1.5 2.3 3.7 3.7 Fold
Caspase-9
1 3.2 5.0 6.5 5.8 4.7 Fold
cleaved
cleaved
cleaved
Bcl-2 Bcl-xL
100 94.9 70.1 66.1 45.6 40.6 %
100 101.8 89.2 68.1 48.6 31.2 %
Figure 13. The effects of (S)-HDAC-42 on the expression level of mitochondria dependent apoptotic pathway related proteins (Caspase-3, Caspase-9, Caspase-8, PARP, Bcl-2 and Bcl-xL) in multiple myeloma cells.
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 ( μM )
Cytochrome c Cox IV
100 88.7 70 43.3 45.7 28.3 %
Figure 14. The effects of (S)-HDAC-42 on the expression level of cytochrome c after mitochondria extraction in multiple myeloma cells.
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 (μM)
NF-κB β-actin
Akt
p-Akt (308) p-Akt (473)
100 95 89.4 64.4 43.8 45.5 %
100 61.8 37.4 25.8 18 7 %
100 111 85.7 53.2 10.7 9.7 %
100 69.3 76.7 67 47.9 26.3 %
Figure 15. The effects of (S)-HDAC-42 on the expression level of Akt pathway related proteins (Akt, phospho-Akt and NFκB) in multiple myeloma cells.
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 ( μM)
XIAP IKK-β
survivin IκBα
β-actin IKK-α p-IKKα/β
1 1 1.1 1.18 1.2 1 Fold
100 98 100 79.5 62.1 43.9 %
p-IκBα
100 101 97.2 95.4 95 64.2 %
1 1.1 1 1.1 1.2 1 Fold
100 98.2 75.1 66.6 48.2 48 %
100 89.9 79.1 37.7 18.9 14.2 % 100 76.8 54.1 40.5 32.4 22. %
Figure 16. The effects of (S)-HDAC-42 on the expression level of NF-κ B pathway related proteins and caspase inhibitor proteins in multiple myeloma cells.
D 0.1 0.25 0.5 0.75 1
(S)-HDAC-42 (μM)
p38 MAPK pp38 MAPK Cyclin B1
p16
β-actin
100 103.1 97.2 92.6 80.7 80.6 %
1 1.3 1.2 1.4 2.2 3.2 Fold
100 59.7 23.9 33.8 37.1 21.6 %
100 79 39.8 28 30.5 32.5 %
Bax
Caspase-8
100 97 95 94.3 93.8 90.9 %
1 1 1 1 1 1 Fold
Figure 17. The effects of (S)-HDAC-42 on the expression level of p38,
phospho-p38, Cyclin B1, p16, Bax and Caspase-8 in multiple myeloma cells.
第五章 討論
首先我們探討(S)-HDAC-42 和 SAHA 對於人類多發性骨髓癌細胞株(U266, IM-9 and RPMI-8226)是否具有毒殺效果,由型態上的變化(Figure 7A)以及統計 結果(Figure 7B-8)得知,SAHA 和(S)-HDAC-42 在 24 小時、48 小時以及 72 小 時偵測其存活率時,發現其對於人類多發性骨髓癌細胞株(U266, IM-9 and RPMI-8226)細胞的確有毒殺能力,且呈現隨劑量增加,毒殺活性更加明顯。
根據 MTS assay 結果統計,三株細胞中為 IM-9 對(S)-HDAC-42 具有最敏 感影響,故選用該株癌細胞作為後續研究對象。此外,經過統計,找出 IC50 約為0.30 μM(表十三),因此設定 0.1、0.25、0.5、0.75、1 μM 作為之後實驗 的濃度梯度,從MTS assay
結果可觀察出細胞存活率在作用48 小時有明顯變化,故為未來實驗的時間設 定。
現代生物學將細胞死亡大致分為細胞凋亡和細胞壞死兩大類。當細胞壞 死同時,往往會因為破裂而釋放出許多細胞激素,連帶影響周邊的細胞,因 此在對於除去患處而不影響周邊正常組織的條件下,會希望癌細胞是以凋亡 的方式死亡。細胞凋亡是以細胞核濃縮、染色體DNA被以核小體為單位切成 梯狀片段(Ladder)、細胞縮小,最終形成細胞凋亡小體(Apoptotic bodies)等形 態變化為特徵。而細胞壞死是以粒線體以及其他細胞器腫大、細胞膨脹、導 致細胞膜破裂等形態變化為特徵,染色體DNA被切成不均等的片段。而目前 檢測細胞凋亡的實驗原理,也是根據這些變化特徵作為判斷的依據。
在得知SAHA和(S)-HDAC-42對於人類多發性骨髓癌細胞株(U266, IM-9 and RPMI-8226)中,是具有引發細胞凋亡能力後。我們期望是透過細胞凋亡的 方式來降低存活率。故以三種不同的方式檢測:Annexin V/PI staining (Flow Cytometry)、Comet assay、TUNEL assay。
在Annexin V/PI staining (Flow Cytometry)實驗結果中,代表活細胞的Q3 訊號比例,隨著藥物作用濃度增加而下降,相對地,代表早期凋亡的Q4訊號 比例則是上升(Figure 9)。代表藥物作用會引起人類多發性骨髓癌細胞(IM-9) 膜外翻。
DNA 斷裂在研究上,已被視為細胞凋亡最具代表的細胞特徵,comet assay 中,利用試劑使細胞膜不完整,並將DNA 變性,經過電泳,若是 DNA 完整 會因分子太大而留在原地,相對的碎裂的小分子細胞則是會被拉出細胞外。
經過PI 染劑的結合,在螢光顯微鏡下會顯現紅色螢光。結果顯示,DNA 的拖 尾程度隨著藥物濃度上升而有上升的趨勢(Figure 10)。
TUNEL assay中,利用外加細胞酵素以及labeled dUTP將受損DNA修補,
換句話說,若是DNA有受損,就會發具labeled的訊號。其訊號是在螢光顯微 鏡下發出綠色螢光,而PI染劑會發出紅色螢光標的完整DNA的位置。結果顯 示,DNA的斷裂程度隨著藥物濃度上升而有增加的趨勢(Figure 11)。
在我們的實驗Comet assay和TUNEL assay中,間接證實藥物作用會引起人 類多發性骨髓癌細胞(IM-9)DNA斷裂。三個變化特徵都可以用於判斷
(S)-HDAC-42對於人類多發性骨髓癌細胞株( IM-9),是具有促進細胞凋亡能力 的。
為了從蛋白質訊息傳遞的觀點來了解,(S)-HDAC-42 是如何在人類多發性 骨髓癌細胞株(IM-9)中來引發酵胞凋亡,我們利用西方墨點法來檢視各種蛋白 質,來探討(S)-HDAC-42 對細胞中蛋白質表現量影響。
(S)-HDAC-42 最主要的生理活性即為組蛋白去乙醯酶(HDAC)的抑制劑。
而組蛋白去乙醯酶(HDAC)家族成員有:HDAC1、2、3、4、5、6、7、8。在 基因轉錄的開始,DNA 原本是以纏繞著組蛋白(Histone)的形式捲成染色體的
當組蛋白乙醯酶抑制劑(HDACi)於胞中發揮其抑制效果,會使組蛋白上乙 醯基含量變多,此時DNA 打開進行基因轉錄,同時許多因病變而沉默的抑癌 因子,例如:p53,能恢復表現,對抗癌化(18)。
在本實驗中,當人類骨髓癌細胞株(IM-9)經(S)-HDAC-42處理48小時過 後,隨藥物濃度增加,由western blotting 得知 HDAC1與HDAC4的蛋白表現 量減少。表示(S)-HDAC-42的確具有減少HDAC表現量的能力(Figure 12)。
粒線體路徑(mitochondria dependent pathway)所誘發的細胞凋亡機制是最 具代表意義的。細胞受到細胞外或細胞內的壓力及傷害時,例如:放射性輻 射、氧氣不足、藥物、DNA damage 等。會使細胞質的粒線體膜電位下降(35),
而Bcl-2蛋白位於粒線體膜的外層,調控細胞的存活(36),另外會促使 Cytochrome c從粒線體的intermembrane space釋放到細胞質中,與Apaf-1與 Caspase-9結合刺激形成apoptosome,之後ATP進而活化Caspase-9的複合物,
Caspase-9也促使下游的caspase-3活化,最後誘導走向細胞凋亡(Figure 18) (37-39)。
Figure 18. The cell apoptosis signal pathway
(1) Bcl-2 家族蛋白 白-凋亡蛋白酵素 cysteine aspartyl-specific protease (Caspase),這類蛋白平 常是以未活化形式存在細胞質中,一旦接受到專一性刺激,便行cleavage 斷成活化態(active form),接著進行一連串的酶解作用(proteolysis
cascade)。凋亡蛋白可分為兩大類:
a. Initiator caspases:主要功能是將未活化(pro-form)的 effector caspases 酶 解使其活化 (例如:Caspase-2, Caspase-8, Caspase-9 和 Caspase-10) b. Effector caspases :主要功能是將執行凋亡蛋白的酵素受質酶解使其活
化 (例如:Caspase-3, Caspase-6 和 Caspase-7)(44-45)。
(3) 細胞色素 C (cytochrome c)
當粒線體凋亡機制被啟動之後,粒線體膜電位會下降,使的通透性提高,
原本位於粒線體內的cytochrome c 會被釋放到細胞質(43)與
Apaf-1(Apoptosis activating factor-1)作結合進而活化 caspase-3、caspase-9 等蛋白,而活化態的caspase-3 又會酶解 PARP (Poly ADP-ribose
polymerase),其為具有 DNA 修復功能的蛋白,使的 DNA 受損卻無法獲 得修補,DNA fragmentation¸,最後走向細胞凋亡(40)。
在本實驗中,當人類骨髓癌細胞株(IM-9)經(S)-HDAC-42 處理 48 小 時過後,隨著藥物濃度增加,由western blotting 觀察到(S)-HDAC-42 負 面調控anti-apoptotic protein-Bcl-2 和 Bcl-xL 的蛋白表現量;而正面調控 pro-apoptotic protein-caspase-3 和 caspase-9 的蛋白表現量(Figure 13)。同 時促進cytochrome c 從粒線體的釋放(Figure 14)。換言之,(S)-HDAC-42 對於人類多發性骨髓癌細胞株(IM-9),是具有透過粒線體路徑
(mitochondria dependent pathway)來促進細胞凋亡能力的。
Akt pathway,主要在細胞當中負責增生、分化的訊息活化,由於在 訊息傳遞路徑中占有較上游的位置,故與各種傳遞路徑都有關聯性,可說 是細胞存活不可或缺的蛋白。以癌細胞而言,其中一條關聯路徑NF-κB 在癌症研究被視為重要的target pathway (47)。
NF-κB,為一種體內的生物誘導蛋白質分子(biological trigger),是在 體內許多疾病的生理作用上扮演了重要的角色,從癌症到骨質疏鬆症,
再到細菌感染,皆與之脫離不了關係(47-48)。NF-κB 發現於哺乳動物的 細胞,平時結合於另一分子--IκB,當上游蛋白活化訊號啟動後,身為激 酶的Ikk 會將 IκB 磷酸化,使 IκB 被 ubiqutination,而被 proteasome 標的 降解。此時IκB 脫離 NF-κB,NF-κB 恢復活性,進入細胞核,啟動基因 製造蛋白質(轉錄因子) (49-50)。
在本實驗中,當人類骨髓癌細胞株(IM-9)經(S)-HDAC-42 處理 48 小 時過後,隨著藥物濃度增加,由Western blotting 觀察到(S)-HDAC-42 負 面調控Akt、NF-κB、Ikk 和 IκB 以及 caspase 的抑制劑 survivin 和 XIAP
第六章 結論
從以上多種實驗結果統整,組蛋白抑制劑(S)-HDAC-42 與 SAHA 在多發 性骨髓癌細胞(U266, IM-9 and RPMI-8226)中,的確具有抑制細胞生長進而引 發細胞凋亡的能力,此外,(S)-HDAC-42 比起 SAHA 具有較好的活性。
在多發性骨髓癌細胞株(IM-9),經過 (S)-HDAC-42 藥物加入 48 小時後,
會使胞內Akt 蛋白活化被抑制,同時抑制 IKK 激酶的活性,如此一來,NF-κB 抑制劑IKB 就不會被磷酸化而被 ubiquitin 所標定而被 proteasome 降解,身為 轉錄因子的NF-κB 就無法被釋放入核,以此方式來抑制 NF-κB 的活性。同時 caspase 抑制劑(XIAP,survivin)的活性也被抑制,因此 caspase 活性上升,最後 細胞就走向細胞凋亡(Figure 19)。其 Akt 的抑制和促進凋亡活性,與先前的文 獻所提及實驗假設相符。
以上結果都可顯現出,(S)-HDAC-42 對於多發性骨髓癌的治療是有潛力 的,甚至更優於目前傳統的治療方式及藥物,但其藥物活性機制,仍須更深 入的探討。
Figure 19. The signal transduction effects of (S)-HDAC-42 in multiple myeloma cells
AKT
P
IKK
P
NF-κB IKB
P IKB
P
IKB P
ub
NF-κB
transcription
Cell proliferation
NF-κB
IAP Caspase-9
Caspase-3
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