台灣紫芝多醣體合併化療藥物之抗腫瘤效果

Abstract

台灣紫芝 (Ganoderma formosanum) 為台灣特有的靈芝品種。本實驗室利用液態深層發酵培養來取得胞外靈芝多醣，並且經過膠體過濾法進行純化，得到三個主要分劃PS-F1、PS-F2、PS-F3。本實驗室先前研究已經證實PS-F2對於已形成C26腫瘤的小鼠具有抗癌效果。本篇研究主要探討當PS-F2結合化療藥物5-fluorouracil (5-FU)是否對於抗癌效果有協同性的加乘。研究結果顯示口服PS-F2對於已形成C26腫瘤的小鼠便已有抑制腫瘤的效果，且PS-F2合併5-FU對於抑制腫瘤的生長有加乘性的效果。在脾臟中，單獨給予PS-F2或5-FU可顯著增加胞殺性T細胞，而合併治療組有更佳卓越的效果。另一方面，多核型骨髓衍生抑制細胞和調節型T細胞再單獨給予的組別就已有顯著性的下降，而合併治療組則有更顯著抑制效果。在浸潤淋巴結中，合併治療組胞殺性T細胞、輔助T細胞、自然殺手細胞則有較明顯上升的現象，另一方面在單獨治療組調節型T細胞比例皆有下降的情形，而合併治療組則有更進一步的下降。腫瘤微環境中，合併治療組其胞殺性T細胞有顯著性的上升，並且多核型骨髓衍生抑制細胞、調節型T細胞腫瘤相關巨噬細胞則有顯著性的下降。另外在單核型骨髓衍生抑制細胞上，我們也發現到給予PS-F2可促進其往巨噬細胞方向成熟，在腫瘤組織中，也偵測到TNF-α、IFN-β、IL-1β、IL-12和iNOS等促發炎相關基因表現有上升的趨勢，而抑制發炎arginase-1基因表現則有下降的趨勢。綜合上述結果，我們的實驗證明PS-F2不但可以活化體內的胞殺性T細胞並削弱免疫抑制型的細胞，而在合併治療上有加乘性的效果，因此PS-F2具有作為免疫療法藥物或者化療藥物佐劑的潛力。

Ganoderma formosanum is a native species of Ganoderma isolated in Taiwan. We have used submerged mycelial culture to produce G. formosanum polysaccharides, and three polysaccharide fractions (PS-F1, PS-F2 and PS-F3) were purified by gel filtration chromatography. Our previous study showed that PS-F2 had antitumor effect in C26 colorectal tumor-bearing mice. In this study, we investigated whether combined treatment with PS-F2 and the chemotherapeutic agent 5-fluorouracil (5-FU) had a synergistic effect against C26 tumor growth in mice. Our data showed that PS-F2 treatment alone by oral gavage could suppress the growth of established tumor, and combined treatment with PS-F2 and 5-FU could further suppress tumor growth synergistically. In the spleen, PS-F2 and 5-FU monotherapies significantly enhanced the population of cytotoxic T lymphocytes (CTL), which was further augmented by the combined treatment. Conversely, the accumulation of immunosuppressive polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and regulatory T (Treg) cells were significantly reduced by PS-F2 and 5-FU monotherapies, and the effect was further augmented in the combination therapy. In the draining lymph nodes, the combination therapy also resulted in significant increases in interferon (IFN)-γ-producing CD4+ and CD8+ T cells. In the tumor microenvironment, combination therapy of PS-F2 and 5-FU significantly increased the CTL population and reduced the accumulation of PMN-MDSCs, Treg cells and tumor associated macrophages (TAMs). The combined therapy also promoted the maturation of monocytic myeloid-derived suppressor cells (M-MDSCs) in the spleen and the tumor. In addition, the combined treatment induced the expression of proinflammatory genes TNF-α, IFN-β, IL-1β, IL-12 and iNOS, and reduced the expression of arginase-1. Overall, our data demonstrate that of PS-F2 exerts its antitumor function by activating CTLs while downregulating immunosuppressive cells, and these effects can be further enhanced when PS-F2 is administered in combination with 5-FU, indicating that PS-F2 has the potential to be used in adjuvant immunotherapy alone or in combination with chemotherapy for the treatment of cancer.