果胶诱导人前列腺癌细胞凋亡：果胶结构与诱导细胞凋亡功能的相关性

作者：Crystal L Jackson2,3, Tina M Dreaden2,3, LisaK Theobald2,3, Nhien M Tran2,3, Tiffany L Beal2,3,Manal Eid4, Mu Yun Gao2,3, Robert B Shirley4, Mark T Stoffel2,3, M Vijay Kumar4, and Debra Mohnen1,2,3

复合碳水化合物研究中心和生物化学与分子生物学系，佐治亚大学，雅典，GA 30602和佐治亚医学院和VA医学中心，奥古斯塔，GA 30912

雄激素非依赖性前列腺癌细胞的治疗选择是有限的。因此，发现诱导雄激素反应性和雄激素不敏感细胞凋亡的药剂至关重要。在这里，我们验证一种来自植物细胞壁的成分果胶能够诱导雄激素响应（LNCaP）和雄激素非依赖性（LNCaP C4-2）人前列腺癌细胞的细胞凋亡。通过Apoptosense测定和胱天蛋白酶-3及其底物，聚（ADP-核糖）聚合酶的激活，市场上能买到的的分级果胶粉（FPP）在两种细胞系中诱导细胞凋亡（比未处理的细胞高约40倍）。相反，柑橘果胶（CP）和经pH调整的 CP，PectaSol，几乎没有细胞凋亡活性。糖基残基组成和连锁分析显示果胶之间没有显着差异。用于除去酯键的温和碱​​处理破坏了FPP的细胞凋亡活性并产生了高聚半乳糖醛酸（HG）寡糖。用果胶甲基酯酶处理FPP以去除半乳糖醛酸羧基甲基酯和/或用内部多聚半乳糖酶来切割非甲基化的HG，导致细胞凋亡活性没有显着降低，这表明需要除羧甲基酯之外的碱敏感连接。 CP（HTCP）的热处理导致诱导与FPP相当的显着水平的凋亡，揭示了生产一种具有凋亡能力的果胶结构的手段。这些结果表明，果胶中的特定结构元素是细胞凋亡活性的原因，并且这种结构可以通过CP的热处理产生或富集。这些发现为果胶凋亡活性的机理研究奠定了基础，并为开发基于果胶的药物，营养保健品或旨在对抗前列腺癌发生的推荐饮食改变奠定了基础。

关键词：细胞凋亡/癌症/果胶/前列腺/结构

Pectin induces apoptosis in human prostate cancer cells: correlation of apoptotic function with pectin structure

Crystal L Jackson2,3, Tina M Dreaden2,3, LisaK Theobald2,3, Nhien M Tran2,3, Tiffany L Beal2,3,Manal Eid4, Mu Yun Gao2,3, Robert B Shirley4, Mark
T Stoffel2,3, M Vijay Kumar4, and Debra Mohnen1,2,3
2 3
  Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602 and
4
Medical College of Georgia and VA Medical Center, Augusta, GA 30912
Received on September 26, 2006; revised on May 9, 2007; accepted on May 11, 2007
Treatment options for androgen-independent prostate cancer cells are limited. Therefore, it is critical to identify agents that induce death of both androgen-responsive and androgen-insensitive cells. Here we demonstrate that a product of plant cell walls, pectin, is capable of inducing apoptosis in androgen-responsive (LNCaP) and androgen- independent (LNCaP C4-2) human prostate cancer cells. Commercially available fractionated pectin powder (FPP)induced apoptosis (approximately 40-fold above non- treated cells) in both cell lines as determined by the Apoptosense assay and activation of caspase-3 and its sub- strate, poly(ADP-ribose) polymerase. Conversely, citrus pectin (CP) and the pH-modified CP, PectaSol, had little or no apoptotic activity. Glycosyl residue composition and linkage analyses revealed no significant differences among the pectins. Mild base treatment to remove ester linkages destroyed FPP’s apoptotic activity and yielded homogalacturonan (HG) oligosaccharides. The treatment of FPP with pectinmethylesterase to remove galacturono- syl carboxymethylesters and/or with endopolygalacturo- nase to cleave nonmethylesterified HG caused no major reduction in apoptotic activity, implicating the requirement for a base-sensitive linkage other than the carboxymethyl- ester. Heat treatment of CP (HTCP) led to the induction of significant levels of apoptosis comparable to FPP, suggesting a means for generating apoptotic pectic struc- tures. These results indicate that specific structural elements within pectin are responsible for the apoptotic activity, and that this structure can be generated, or enriched for, by heat treatment of CP. These findings provide the foundation for mechanistic studies of pectin apoptotic activity and a basis for the development of pectin- based pharmaceuticals, nutraceuticals, or recommended diet changes aimed at combating prostate cancer occurrence
and progression.
Key words: apoptosis/cancer/pectin/prostate/structure