幾丁聚醣(Chitosan)為甲殼類動物外骨骼中的主要成份，可由幾丁質(chitin)經鹼水解而來，近年來已知其具有降低體內膽固醇的作用，可以有效預防高血脂引起的冠心病、脂肪肝；亦有報告指出chitosan可抑制惡性細胞的轉移，使腫瘤細胞走向apoptosis，以及增加實驗老鼠對抗細菌感染的能力。本研究的目的是評估chitosan對於抗腫瘤發生的能力及其相關機制的探討。先以LMWC(Low molecular weight chitosan)與HMWC(High molecular weight chitosan)同時進行in vivo與in vitro實驗，評估幾丁聚醣(LMWC、HMWC)對腸胃道細胞的影響，結果發現LMWC與HMWC對預防與治療腸胃道癌症的效果不佳。因此我們使用另一種可溶於水的幾丁寡醣(water soluble chitosan oligomer)進行多種癌細胞株的篩選，結果發現water soluble chitosan對人類大腸癌細胞(colon 205、HT-29)，膀胱癌細胞(T24)，血癌細胞(Jurkat)無明顯抑制細胞生長效果，而對血癌細胞(U937、HL-60)有微量抑制細胞生長的效果，只有胃癌細胞(AGS)的細胞生長可被有效的抑制約51%。因此進一步的分析AGS細胞經water soluble chitosan處理後細胞週期的變化，發現細胞在S phase的百分比與control組相比有減少的趨勢；因此我們利用BrdU cell cycle analysis assay分析細胞DNA合成的情形，結果發現AGS細胞經加藥處理後在S phase的DNA合成被抑制。接下來我們分析AGS細胞調控細胞週期相關蛋白的表現，結果發現Cyclin D1、Cyclin D3、p21/Cip與p27/Kip蛋白表現增加，而PCNA、RBBP蛋白的表現減少，推測water soluble chitosan對AGS細胞的生長抑制功能是經由調控這些蛋白而得。本研究也分析了water soluble chitosan對AGS細胞MMP蛋白活性的影響，結果發現water soluble chitosan可有效抑制MMP-2與MMP-9蛋白的活性，抑制效果並隨著劑量而增加。本研究結論為幾丁聚醣在作為癌症治療或預防藥物的使用仍須進一步的被研究與探討。

Chitosan derived from chitin by deacetylation in the presence of alkali present mainly in the exoskeleton of crustaceans. It has been reported that chitosan has various biological functions such as improving the symptom of fatty liver and hyperlipidaemia, enhancing the protecting effect of mice against bacteria infection, and avoiding metastasis of malignant cell. The present study was designed to investigate the anti-tumorigenic effects and related mechanisms of chitosan. LMWC (Low molecular weight chitosan) and HMWC (High molecular weight chitosan) were used to evaluate their anti-tumorigenic effects on gastro-intestinal cells, both in vivo and in vitro. We found that LMWC/HMWC possessed only limited G-I cancer cells inhibition effects both in cell culture and animal study. Thus, water soluble chitosan (WSC) was applied, instead of LMWC/HMWC, to test their anti-tumoeigenesis potency. Through a screening test of several cancer cell lines, the results showed that a significant inhibition effects was observed in AGS cells. Therefore, we further investigated the influence of cell cycle regulation of WSC on AGS cells. Flow cytometry analysis of cell cycle distribution indicated that the percentage of S phase reduced dramatically in cells treated with WSC. In addition, BrdU incorporation assay revealed a decreased DNA synthesis rate in treated AGS cells. Cell cycle-related genes expressions were analyzed and the results indicated that Cyclin D1, Cyclin D3, p21/Cip and p27/Kip were up-regulated, while the PCNA, BRBP and were down-regulated. Moreover, we also found that the activity of one of the metastasis-regulating proteins (MMP-2, MMP-9) could be inhibited in AGS cells treated with WSC. Base on the present findings, we concluded that WSC possess mild growth inhibition potency on AGS cancer cells. More studies are needed to further confirm the role of chitosan in cancer therapy or cancer chemoprevention.

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