臺灣紫芝多醣體對於髓質衍生抑制型細胞之影響

Abstract

臺灣紫芝是在台灣所分離的天然靈芝物種。在先前我們已經證明，從臺灣紫芝的深層培養液中純化得到的多醣體。PS-F2在小鼠的腫瘤模式中，具有免疫調節和抗腫瘤特性。髓質衍生抑制型細胞 (myeloid-derived suppressor cells, MDSCs) 為在諸如癌症之病理條件下會擴張的異質髓質細胞群體。於腫瘤微環境裡，MDSCs可以發揮免疫抑制功能並促進腫瘤生長。 在本研究中，我們探討PS-F2是否可以透過直接調節MDSCs的免疫抑制能力來發揮抗腫瘤的功能。我們從C26大腸癌腫瘤小鼠的脾臟中分離出monocytic (M)-MDSCs和polymorphonuclear (PMN)-MDSCs。純化的M-MDSCs確實抑制了被anti-CD3e和anti-CD28抗體刺激的CD4+ T細胞的增生，而純化的PMN-MDSCs卻不影響T細胞的活化。然而，我們的結果顯示，PS-F2處理對M-MDSC的免疫抑制功能沒有顯著效果。另外，本研究也使用顆粒球-巨噬細胞集落刺激因子 (granulocyte-macrophage colony-stimulating factor, GM-CSF) 和白介素 (Interleukin, IL)-6培養了小鼠骨髓細胞，在體外產生骨髓衍生MDSCs (BM-MDSCs)。我們分析了PS-F2刺激對BM-MDSCs的免疫抑制、基因表達和成熟的影響。我們的結果顯示，BM-MDSCs能有效抑制T細胞增生，卻不受PS-F2的影響。PS-F2刺激並未有效改變BM-MDSCs中的基因表達。但是，給予PS-F2會促進成熟表面標記（例如CD11c，CD80和MHCII）的上調。與PS-F2相反，LPS刺激會導致BM-MDSCs免疫抑制活性的強化。總結而言，我們的結果說明了PS-F2可能不會透過直接調節MDSCs的免疫抑制功能，來發揮其抗腫瘤的作用。

Ganoderma formosanum is a native Ganoderma. species isolated in Taiwan, and we have previously shown that the PS-F2, a polysaccharide fraction purified from the submerged culture broth of G. formosanum, has immunomodulatory and anti-tumor properties in mice. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid cells that expand in pathological conditions such as cancer. In the tumor microenvironment, MDSCs exert immunosuppressive functions and promote tumor growth. In the present study, we investigated whether PS-F2 may exert the anti-tumor effect by directly modulating the immunosuppressive effect of MDSCs. We isolated monocytic (M)-MDSCs and polymorphonuclear (PMN)-MDSCs from the spleen of C26 colorectal tumor-bearing mice. Purified M-MDSCs dose-dependently suppressed the proliferation of CD4+ T cells stimulated with anti-CD3ε and anti-CD28 antibodies, while purified PMN-MDSCs did not affect T cell proliferation. Our results showed that PS-F2 treatment did not have significant impact on the immunosuppressive function of M-MDSCs. We also cultured mouse bone marrow cells in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-6 to generate bone marrow-derived MDSCs (BM-MDSCs) in vitro. We analyzed the effect of PS-F2 stimulation on immunosuppression, gene expression, and maturation of BM-MDSCs. Our results showed that BM-MDSCs effectively suppressed T cell proliferation, which was not affected by PS-F2. PS-F2 stimulation did not strongly alter the gene expression profile in BM-MDSCs. However, PS-F2 treatment resulted in the upregulation of maturation surface markers such as CD11c, CD80, and MHCII. In contrast to PS-F2, LPS stimulation resulted in enhanced immunosuppression of BM-MDSCs. Overall, our results indicate that PS-F2 may not exert its anti-tumor effect via directly modulating the immunosuppressive function of the MDSCs.