白皮杉醇抑制M2型巨噬細胞促腫瘤轉移功效及其分子機轉

Abstract

在全球腸癌現今為第三大癌症，根據世界衛生組織的調查近三十年全球患病率有上升的趨勢，其中我國發生率高居世界第一。現今大腸癌末期治癒率低且復發率高。而腫瘤微環境正是造成其不易治療的原因之一。腫瘤微環境指腫瘤和其周遭細胞的交互作用，其中M2型巨噬細胞為具抗發炎及促腫瘤生長的能力，因此抑制M2型巨噬細胞調節的腫瘤微環境，並阻斷腸癌細胞生長和轉移極為重要。白皮杉醇 (Piceatannol, PIC) 常見於花生、山葡萄、桃金孃和百香果等天然物，且被證實具有抗癌功效。因此本研究以phorbol 12-myristate 13-acetate (PMA) 誘導人類單核球細胞THP-1分化為M2型巨噬細胞，並與人類腸癌細胞SW480進行共培養 (Co-culture) 模式評估白皮杉醇抑制M2型巨噬細胞誘發之促腫瘤轉移微環境的功效及其調節分子機制。體外共培養之結果顯示，不具細胞毒性的PIC可顯著抑制THP-1分化成M2型巨噬細胞，而干擾M2型巨噬細胞活化腸癌細胞內Transforming Growth Factor Beta (TGF-β) / Drosophila mothers against decapentaplegic protein 2/3 (Smad2/3) 訊號路徑及其下游調節之促轉移因子Matrix metallopeptidase 9 (MMP-9) 和 Monocyte chemoattractant protein-1 (MCP-1) 的表現，而抑制腸癌細胞之移動能力。在 Balb/CAnN.Cg-Foxnlnu/CrlNarl裸鼠之異種移植 (Xenograft) 動物模式中亦證實，M2型巨噬細胞可促進腫瘤細胞的發展與肺轉移情形，經腹腔注射50 mg/kg白皮杉醇後可顯著降低皮下與肺臟腫瘤的發生與發展。免疫組織染色法分析之結果發現，白皮杉醇可經由降低腫瘤組織中表現M2型巨噬細胞並減少微環境中TGF-β的表達，而發揮抗增生和抗轉移的功效。綜合以上結果建議，白皮杉醇具有預防或治療腸癌的潛力，此研究成果更可供未來開發為機能性食品或輔助治療試劑之依據。

In the world, colorectal cancer is the third most commonly diagnosed cancer worldwide today. According to the World Health Organization survey, the global prevalence rate of colorectal cancer has increased in the past 30 years, and the incidence rate in Taiwan is the highest in the world. At present, the cure rate of colorectal cancer is low and the recurrence rate is high. The tumor microenvironment is known to be involved in acquired resistance of tumors to various therapies. The tumor microenvironment refers to the interaction between the tumor and its surrounding cells. Among them, M2 type macrophages have anti-inflammatory and tumor-promoting ability, therefore, it is very important to inhibit the tumor microenvironment regulated by M2 type macrophages and to hinder the growth and metastasis of colorectal cancer cells. Piceatannol (PIC) is a natural product commonly found in peanut, grapes, myrtle and passion fruit and has been shown to have anti-tumor effects. Therefore, this study used phorbol 12-myristate 13-acetate (PMA) to induce human monocytic cell THP-1 to differentiate into M2 type macrophages, and co-culture with human colorectal cancer cell SW480. We aimed to evaluate the efficacy of PIC in inhibiting M2 macrophage-induced tumor metastasis microenvironment and the underlying molecular mechanisms. The results of in vitro co-culture experiment showed that PIC at maximium non-toxic concentrations significantly inhibited the differentiation of THP-1 into M2 macrophages, therefore, suppression of M2 type macrophage activation in colorectal cancer cells. transforming growth factor beta (TGF-β) / drosophila mothers against decapentaplegic protein 2/3 (Smad2/3) signal pathway and downstream regulation of the transfer factors matrix metallopeptidase 9 (MMP-9) and monocyte chemoattractant protein-1 (MCP-1) in colorectal cancer, thereby inhibiting their mobility potency. Consistent with in vitro findings, the intraperitoneal (i.p.) injection of 50 mg/kg piceatannol significantly decreased the subcutaneous tumor growth and pulmonary metastases by inhibiting the M2-macrophage polarization and TGF-β secretion in the tumor microenvironment of SW480 xenograft mouse model. Taken together, our results suggest that PIC has the potential to prevent or treat colorectal cancer, and these findings provide important riches for future development PIC as functional foods or adjuvant therapeutic agents.