人芽囊原蟲 (Blastocystis hominis) 是一種常見於全世界哺乳動物和家禽腸胃道中的微小寄生蟲。 患病率在已開發國家為 (5-20%)，而在發展中國家由於衛生條件較差和與動物密切接觸的關係人芽囊原蟲的患病率約為 60%。多項研究結果顯示，人芽囊原蟲感染，與炎症性腸病 (inflammatory bowel disease, IBD) 與腸道功能性障礙 (irritable bowel syndrome, IBS) 等腸胃道疾病有關。其他研究表明，人芽囊原蟲感染會促進大腸直腸癌 (colorectal cancer, CRC) 的發展和腸道菌群失調，這種情況下的腸道菌群中如具核梭桿菌 (Fusobacteria nucleatum)的數量改變，透過其蛋白質可促進大腸直腸癌細胞的生長，而直接影響癌症的發展。由於在其他研究中也觀察到：人芽囊原蟲感染在大腸直腸癌患者中的患病率較高。因此，本研究希望通過探討人芽囊原蟲對大腸直腸癌腫瘤發展中的微生物群的影響，從而去釐清人芽囊原蟲和大腸直腸癌之間的關聯性和致病機制。根據研究結果，我們發現人芽囊原蟲在大腸直腸癌患者中檢測陽性率明顯高於全球平均感染率，並且人芽囊原蟲和具核梭桿菌均可促進大腸直腸癌細胞的增殖。更進一步我們發現：人芽囊原蟲感染後會透過 Wnt/β-catenin 信號傳遞路徑，激活下游相關調控因子。此外，我們透過共培養系統發現人芽囊原蟲可促進具核梭桿菌的增殖。透過本篇研究結果顯示，人芽囊原蟲感染與大腸直腸癌發展具有高度關聯性，因此可藉由治療人芽囊原蟲感染作為提高大腸直腸癌治療效果的新策略。

Blastocystis hominis (B. hominis) is a common microscopic parasite in the gastrointestinal tract of mammalian and domestic animals worldwide. The prevalence of Blastocystis hominis is about 60% in developing countries, due to poor hygiene and close contact with animals, compared to developed countries (5-20%). Several studies revealed that B. hominis infection is associated with gastrointestinal diseases such as IBD and IBS, causing diarrhea, abdominal pain, or other symptoms. Another study shows that B. hominis contributed to colorectal cancer (CRC) and gut microbiota dysbiosis, the bacteria directly causing affection in cancer metabolism by producing metabolites such as F. nucleatum to promote the growth of CRC cells since they have also observed a higher prevalence of B. hominis infection in CRC patients, in this study, to investigate the causality and underlying mechanisms between B. hominis and CRC by understanding that B. hominis affects on the microbiota in tumor progression. This study reveals the prevalence of B. hominis and F. nucleatum in CRC patients by PCR technique. The prevalence of B. hominis in CRC patients is significantly higher than in healthy people. In-vitro investigation showed that both B. hominis and F. nucleatum triggered the higher proliferation of CRC cells. In addition, the co-incubation system revealed that B. hominis triggered the proliferation of F. nucleatum. B. hominis induced the activation of the Wnt/β-catenin signaling pathway, confirmed by real-time PCR and immunofluorescence staining. These results suggest that the high association of B. hominis with CRC and identifying B. hominis infection treatment can serve as a novel strategy to improve the efficacy of CRC therapy if positive to B. hominis.

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