探討小孢子靈芝免疫調節蛋白 (GMI) 對犬乳腺腫瘤細胞的作用

Abstract

靈芝是以其多種生物活性化合物而聞名，包括多醣類、三萜類及真菌免疫調節蛋白（FIPs），長久以來一直被應用於中醫藥以促進健康。其中，小孢子靈芝免疫調節蛋白（GMI）是一種從小孢子靈芝中分離出的FIP，具有穩定的四聚體結構。在人類癌細胞的研究中，GMI已表現出顯著的抗癌效果，包括抑制細胞侵襲及遷移、與生長因子受體競爭，以及誘導細胞程序性死亡。犬乳腺腫瘤是母犬中最常見的腫瘤之一，其中約50%屬於惡性，對犬隻健康構成重大威脅。雖然手術切除是目前的主要治療方式，但由於高轉移率以及化療和放療等輔助治療的耐受性問題，迫切需要新型治療策略。儘管已有多篇關於GMI在人類癌細胞中的研究，目前尚無研究探討GMI對犬癌症的抗腫瘤效用。本研究旨在評估GMI在犬乳腺腫瘤細胞中的抗腫瘤作用及其潛在機制。本研究選用了三株犬乳腺腫瘤細胞株（CF41-Mg、CMT-1和MPG），結果顯示，GMI處理後的細胞出現了顯著的形態學改變，包括細胞脫落和收縮，並且細胞存活率以劑量和時間依賴性顯著降低。Annexin V-PI染色的流式細胞術分析顯示，細胞凋亡是GMI引起細胞死亡的主要機制。此外，與常用化療藥物阿黴素聯合使用時，GMI顯著增強其細胞毒性效果，大幅降低腫瘤細胞存活率。進一步細胞學試驗的結果顯示，GMI對CMT細胞的遷移和侵襲具有顯著的抑制作用。經由Western blot分析發現，GMI主要透過調節PI3K/AKT和FAK/Beta-catenin等關鍵信號通路來實現其抗腫瘤作用，其次透過Caspase-3及LC3B蛋白表現的分析，證實凋亡及自噬可能也參與GMI造成CMT細胞死亡的機制。此外，GMI對非腫瘤細胞（MDCK）的影響較小，表明其具有良好的選擇性毒性，可能具較低的副作用。這些結果表明，GMI具有成為犬乳腺腫瘤治療劑的潛力，值得進一步研究其臨床應用。

Ganoderma, contains several bioactive compounds, including polysaccharides, triterpenoids, and fungal immunomodulatory proteins (FIPs), and has long been used in traditional Chinese medicine to promote health. Ganoderma microsporum immunomodulatory protein (GMI), a FIP isolated from Ganoderma microsporum, naturally exists as a stable tetramer structure. Studies on human cancer cells have demonstrated its significant anticancer effects, including inhibition of cell invasion and migration, competition with growth factor receptors, and induction of programmed cell death. Canine mammary tumors (CMTs) are among the most common tumors in female dogs, with approximately 50% being malignant, posing a significant health threat. While surgical resection remains the primary treatment, high metastatic rates and resistance to adjuvant therapies such as chemotherapy highlight the urgent need for novel therapeutic strategies. Currently, no studies have explored the antitumor effects of GMI on canine cancers, despite extensive research on human cancer cells. This study aimed to evaluate the antitumor effects of GMI on CMT cells and its underlying mechanisms. Three CMT cell lines (CF41-Mg, CMT-1, and MPG) were treated with GMI, resulting in significant morphological changes, including cell detachment and shrinkage. GMI treatment reduced cell viability in a dose- and time-dependent manner. Annexin V-PI staining analysis confirmed that apoptosis was the primary mechanism of GMI-induced cell death. Additionally, when combined with Doxorubicin, a commonly used chemotherapeutic agent, GMI significantly enhanced its cytotoxic effects, greatly reducing tumor cell viability. Further cellular assays revealed that GMI significantly inhibited the migration, and invasion of CMT cells. Western blot analysis showed that GMI exerted its antitumor effects primarily by modulating key signaling pathways, including PI3K/AKT and FAK/Beta-catenin. Next, the expression analysis of caspase 3 and LC3B revealed both apoptosis and autophagy may be involved in the mechanism of GMT cell death caused by GMI. Moreover, GMI demonstrated minimal effects on non-tumor MDCK cells, indicating its selective cytotoxicity and potential for reduced side effects. These findings suggest that GMI holds significant potential as a therapeutic agent for canine mammary tumors and warrant further investigation into its clinical applications.