白皮杉醇對苯駢芘/葡聚醣硫酸鈉誘導的小鼠結腸炎相關結直腸癌的化學預防功效和分子機制

Abstract

根據世界衛生組織 (World Health Organization, WHO) 2022 年統計資料顯示，大腸直腸癌 (colorectal cancer, CRC) 為全球癌症發生率第三高、死亡率第二高之惡性腫瘤，顯示其對人類健康造成重大威脅。流行病學研究指出，飲食相關致癌物與慢性腸道發炎反應是促進 CRC 發生與進展的重要危險因子。食品加工與高溫烹調過程中所產生之多環芳香烴 (polycyclic aromatic hydrocarbons, PAHs)，可經代謝誘發氧化壓力與促發炎反應，進而活化多條腫瘤相關訊息途徑。其中，苯駢芘(benzo[a]pyrene, B[a]P) 為 PAHs 之代表性致癌物，常與腸道發炎共同促進結腸直腸癌的發生。化學預防 (chemoprevention) 藉由天然或合成化合物抑制發炎反應與致癌過程，已成為癌症預防的重要策略。白皮杉醇 (piceatannol, PIC) 為一種芪類多酚 (stilbenoid)，廣泛存在於葡萄、百香果及白茶中，已被證實具有抗氧化與抗發炎等生物活性。然而，PIC 在發炎相關結腸致癌模型中，不同介入時期之化學預防效果與機制仍缺乏系統性探討。本研究以 B[a]P 與葡聚糖硫酸鈉 (dextran sulfate sodium, DSS) 共同誘導雄性小鼠之發炎相關結腸癌模型，於 18 週內分別在不同致癌階段給予 0.025% PIC，以評估介入時機對腫瘤形成、發炎反應及腸道菌相之影響，並透過 RNA 定序 (RNA-seq) 分析腸道轉錄組變化。結果顯示，持續補充 PIC 可顯著減緩體重流失、降低疾病活動指數 (disease activity index, DAI) 及腫瘤形成，並改善腸道組織形態與上皮屏障功能。PIC 明顯抑制促發炎細胞激素 interleukin-6 (IL-6)、tumor necrosis factor-α (TNF-α) 與 interleukin-1β (IL-1β) 的表現，同時提升抗發炎因子 interleukin-10 (IL-10)，顯示其可有效緩解腸道慢性發炎反應。轉錄組分析顯示，PIC 可下調多條與發炎與腫瘤促進相關之訊息途徑，包括芳香烴受體 (aryl hydrocarbon receptor, AhR)、基質金屬蛋白酶 (matrix metalloproteinases, MMPs)、Wnt 及 PI3K/AKT/mTOR 路徑，並上調與上皮修復與腫瘤抑制相關之轉麩胺酶 3 (transglutaminase 3, TGM3)。蛋白質層級驗證結果進一步證實 PIC 可抑制 PI3K/AKT/mTOR 訊息傳導活化，並促進 TGM3 表現。此外，腸道菌相分析顯示，PIC 可增加具短鏈脂肪酸 (short-chain fatty acids, SCFAs) 產生能力之益生菌，如 Roseburia faecis 與 Kineothrix alysoides，並降低潛在致病菌 Turicibacter sanguinis 與 Romboutsia ilealis 的豐度，進而改善腸道微生態平衡並提升 SCFAs 含量。綜合上述，本研究顯示 PIC 透過抑制發炎反應、調控發炎相關致癌訊息途徑、促進上皮修復及重建腸道菌相平衡，多層次地抑制 B[a]P/DSS 誘導之發炎相關結腸直腸癌發展，突顯其作為天然膳食化學預防劑之應用潛力。

Colorectal cancer (CRC) ranks as the third most frequently diagnosed cancer and the second leading cause of cancer-related mortality worldwide, according to the World Health Organization (WHO, 2022). Accumulating evidence indicates that chronic intestinal inflammation induced by dietary carcinogens is a critical driver of CRC initiation and progression. Polycyclic aromatic hydrocarbons (PAHs), generated during food processing and high-temperature cooking, can induce oxidative stress and pro-inflammatory responses following metabolic activation. Among them, benzo[a]pyrene (B[a]P) is a representative PAH and a well-established carcinogenic marker that synergizes with intestinal inflammation to promote colorectal tumorigenesis. Chemoprevention, which aims to suppress inflammation-associated carcinogenic processes using natural or synthetic compounds, has gained increasing attention. piceatannol (PIC), a naturally occurring stilbenoid polyphenol found in grapes, passion fruit, and white tea, has been reported to exhibit antioxidant and anti-inflammatory activities. However, the chemopreventive efficacy of PIC at different intervention stages and its underlying mechanisms in inflammation-associated CRC remain largely unexplored. In this study, an inflammation-driven CRC model was established using B[a]P combined with dextran sulfate sodium (DSS) in male mice. PIC (0.025%) was administered at different stages over an 18-week period to evaluate the impact of intervention timing on tumor development, inflammatory responses, and gut microbiota composition. Transcriptomic alterations in intestinal tissues were further examined using RNA sequencing (RNA-seq). The results demonstrated that continuous PIC supplementation significantly alleviated body weight loss, reduced disease activity index (DAI) scores, and suppressed tumor formation, accompanied by improvements in intestinal morphology and barrier integrity. Notably, PIC markedly downregulated pro-inflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β), while upregulating the anti-inflammatory cytokine interleukin-10 (IL-10), indicating effective attenuation of chronic intestinal inflammation. RNA-seq analysis revealed that PIC suppressed multiple inflammation- and tumor-associated signaling pathways, including aryl hydrocarbon receptor (AhR), matrix metalloproteinases (MMPs), Wnt, and PI3K/AKT/mTOR pathways, while enhancing the expression of transglutaminase 3 (TGM3), a gene implicated in epithelial repair and tumor suppression. These findings were further validated at the protein level, confirming that PIC inhibited PI3K/AKT/mTOR activation and promoted TGM3 expression. Moreover, PIC significantly modulated gut microbiota composition by enriching short-chain fatty acids (SCFAs)-producing bacteria, such as Roseburia faecis and Kineothrix alysoides, while reducing potentially pathogenic taxa including Turicibacter sanguinis and Romboutsia ilealis. This microbial reshaping was associated with increased SCFAs production and improved intestinal homeostasis. From the above, these findings demonstrate that PIC exerts multifaceted chemopreventive effects primarily through suppression of inflammation, accompanied by modulation of oncogenic signaling pathways, enhancement of epithelial repair, and restoration of gut microbiota balance. PIC therefore represents a promising dietary chemopreventive agent for inflammation-associated colorectal carcinogenesis.