細胞穿透型胜肽，如醣胺多醣結合胜肽（GAG-binding peptide）屬於可將各種分子載體轉運到活細胞中的短鏈胜肽。本研究主要探討短鏈胜肽結合化學物後(WCTK001)其對特定細胞株的細胞毒殺性。為了觀察WCTK001是否對細胞有毒性，本研究首先以WCTK001分別處理各種細胞株48小時後再偵測細胞存活率。有趣的是我們觀察到WCTK001只會對特定細胞株具有細胞毒殺性，並發現WCTK001會造成該特定細胞株的細胞凋亡以及DNA損傷。由於WCTK001是藉由細胞表面Heparan sulfate proteoglycans (HSPGs)進入細胞，實驗結果發現與其他細胞株相比，該特定細胞株在細胞表面醣基化之syndecan-1 (SDC-1)蛋白表現相對較高，顯示SDC-1醣基化對於WCTK001引發的細胞毒性可能是必需的。為了確認WCTK001所引起的細胞毒性，我們將細胞分別單獨處理胜肽或胜肽結合不同之化學物，實驗結果顯示只有WCTK001與其衍生物具有特定細胞株之特異細胞毒殺性。接著，我們也發現WCTK001引發的細胞凋亡雖然會造成DNA修復蛋白PARP降解，但是未能偵測到任何caspases活化。此外，經WCTK001處理後的特定細胞株之粒線體型態破碎，且其細胞色素c會被釋放至細胞質中。我們也發現WCTK001誘導的細胞毒性與鈣釋放無關。相反地，在抗氧化劑存在下會降低其細胞毒性。整體而言，我們認為WCTK001會誘導caspase-independent細胞死亡，其引發粒線體破碎、細胞色素c釋放、PARP降解，最終導致特定細胞株凋亡。

Cell-penetrating peptides, such as GAG-binding peptides, are short peptides that can transport various molecular cargos into living cells. In this study, we investigate cytotoxic effects of a specific chemical-conjugated peptide, WCTK001, on cancer cells. To investigate the cytotoxic effect of WCTK001, we treated different cell lines with WCTK001 and examined cell viability. Interestingly, we found that WCTK001 induced cytotoxicity in specific cell lines. Coordinately, cell lines sensitive to WCTK001 displayed a higher level of glycosylated syndecan-1 (SDC-1) when compared to other cell types, implying that SDC-1 glycosylation is essential for WCTK001-mediated cytotoxicity. To understand the nature of cytotoxicity induced by WCTK001, we treated cells with the peptide, or peptide in conjugation with different chemicals, among which WCTK001 and its analog induced significant cytotoxic effect on the specific cell lines. Notably, we found that WCTK001induced PARP cleavage in the absence of caspase activity. In addition, mitochondria fragmentation and cytochrome-c release were detected in the presence of WCTK001. We also found that WCTK001 induced cytotoxicity was independent of calcium release. Conversely, WCTK001-induced cytotoxicity was diminished upon the treatment with anti-oxidant reagent. In conclusion, WCTK001 induces caspase-independent cell death, which is mediated by mitochondria fragmentation, cytochrome-c release, PARP cleavage, and ultimately leading to apoptosis in specific cell lines.

1. Introduction 1
1.1 Current status and therapy of oral cancer 1
1.2 Heparan sulfate proteoglycans 2
1.3 Chemical-conjugated GAG-Binding peptide 4
1.4 Mechanisms of cell death 7
1.5 Reactive oxygen species (ROS) in cancer 8
1.6 N-acetylcysteine (NAC) 9
2. Hypothesis and specific aims 10
3. Material and Methods 11
4. Results 16
4-1. The effect of WCTK001 in different cell lines 16
4-2. WCTK001 induced apoptosis in Ca922 16
4-3. WCTK001 induces PARP cleavage in a caspase-independent manner. 16
4-4. Chemical conjugation is essential for inducing cytotoxicity 17
4-5. WCTK001 treatment induced mitochondria fragmentation and release of cytochrome-c 17
4-6. WCTK001 induced cytotoxicity is partially suppressed by N-acetylcysteine 18
4-7. WCTK001 induced ROS generation in Ca922 cells 18
4-8. WCTK001 induced cytotoxicity is cell type specific 18
4-9. SDC-1 expression level is critical for the cell survival of Ca922 20
4-10. Overexpression of EGFP-SDC-1 does not increase cell sensitivity to WCTK001 20
4-11. WCTK001 treatment induced DNA damage 20
4-12. WCTK001 induced cytotoxicity is light-sensitive 21
5. Discussion 23
6. Figures 27
Figure 1. WCTK001 induces cell death in oral cancer cells. 27
Figure 2. WCTK001 induced apoptosis in Ca922. 28
Figure 3. WCTK001 induces PARP cleavage without caspase activation. 29
Figure 4. Chemical conjugation induces cytotoxicity. 30
Figure 5. WCTK001 treatment induced mitochondria fragmentation and cytochrome-c release. 31
Figure 6. WCTK001 induced cytotoxicity is partially suppressed by N-acetylcysteine (NAC). 32
Figure 7. WCTK001 induced ROS generation in Ca922 cells. 33
Figure 8. WCTK001 induced cytotoxicity is cell type specific. 34
Figure 9. SDC-1 is essential for the cell survival of Ca922. 35
Figure 10. Overexpression of SDC-1 does not increase sensitivity to WCTK001. 36
Figure 11. WCTK001 treatment induced DNA damage. 37
Figure 12. WCTK001 induced cytotoxicity is light-sensitive 38
Figure 13. Schematic model of the roles of WCTK001 induced apoptosis 39
7. Reference 40
8. Table 46
9. Appendix 49

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