植化素對大腸直腸癌之抑制機制與營養代謝體之分析

Abstract

大腸直腸癌(colorectal cancer)在全球癌症致死原因中位居第二，其發生原因與飲食、生活習慣、遺傳等因素相關。腸道的癌化機制是一系列基因突變累積的結果，包含adenomatous polyposis coli (APC)突變使β-catenin表現增加，導致細胞異常增生，產生腺瘤；K-ras的異常表現，使不正常的細胞持續生長，腺瘤加大；p53的突變使異常細胞不會凋亡，最後形成惡性腫瘤。 過去研究顯示，植物內所含的植化素(phytochemicals)具有抑制癌症發生的效果。本研究參考相關文獻，選出六種具有抑制大腸直腸癌潛力的植化素，包括epigallocatechin gallate (EGCG)、sulforaphane (SFN)、phenethyl isothiocyanate (PEITC)、6-shogaol (SG)、ursolic acid (UA)與resveratrol (RV)，分別對大腸癌細胞株HT-29及HCT 116進行處理，分析這些植化素對APC、β-catenin、p53等蛋白表現的影響，篩選出能顯著影響上述蛋白表現之植化素，繼而進行代謝體學分析，以了解其作用機制。 結果顯示，resveratrol可有效抑制β-catenin增加、促進wild-type p53表現，並使mutant p53降低，效果最佳。接著進行代謝體分析後發現，resveratrol可抑制大腸癌細胞HT-29及HCT 116之taurine產生、降低HT-29之hypoxanthine與5’-methylthioadensine並提高其CMP；在HCT 116中，resveratrol可提升purine metabolism、TCA cycle及胺基酸相關代謝產物。由此推測，resveratrol可經由對wild-type p53與mutant p53之調控來影響purine metabolism及促進葡萄糖進入TCA cycle產生能量，減少其醣解作用發生，進而達到抑制癌細胞生長之效果。

Colorectal cancer (CRC) is the third major cause of cancer-related mortality in Taiwan. The risk factors of CRC include age, family history, inflammatory bowel diseases, and environmental and dietary procarcinogens. In genetic phase, it goes through a series of gene mutations, including APC, β-catenin and p53, from small benign precursor lesions to metastatic carcinomas. Based on information from literatures, this study chose six phytochemicals, including epigallocatechin gallate (EGCG), sulforaphane (SFN), phenethyl isothiocyanate (PEITC), 6-shogaol (SG), ursolic acid (UA) and resveratrol (RV), to investigate their effect on HT-29 and HCT 116 colorectal cancer cells in terms of regulating APC, β-catenin and p53. Then we selected the most effective one for further metabolic profile analysis. Results showed that resveratrol can suppress β-catenin, mutant p53 expression and increase wild-type p53 expression. And the metabolic profiling indicated that resveratrol can reduce taurine in both colorectal cancer cells, decrease hypoxanthine and 5’-methylthioadensine, enhance CMP in HT-29 cells. In HCT 116 cells, resveratrol is able to raise purine metabolism, TCA cycle and amino acid related metabolites. In conclusion, resveratrol may affect purine metabolism and TCA cycle by regulating wild-type p53 and mutant p53 expression.