槲皮素藉由影響PG/β-catenin/C-myc訊號路徑抑制乳癌細胞的增殖和侵襲性

槲皮素 (Quercetin) 是一種在植物中被發現的類黃酮。許多文獻證明了槲皮素具有廣泛的生理活性，包括抗發炎、抗氧化以及抗血管生成，並且表示槲皮素可以預防各種疾病包括乳癌、肺癌、肝癌、腦癌等等。因此，槲皮素在預防疾病以及促進健康方面發揮著重要作用。Plakoglobin (PG, γ-catenin) 是犰狳蛋白家族的成員之一，也是β-catenin的結構同源物。PG除了在細胞中發揮重要的結構作用之外，還會參與細胞的訊號調節，而PG在Wnt/β-catenin這個訊號路徑中的作用跟β-catenin不同。事實上，多項研究都表示PG在多種癌症中具有抑制的作用，並且對於β-catenin有拮抗的作用。PG甚至會透過與細胞內蛋白質的相互作用或是藉由隔離擔任轉錄因子的β-catenin，與β-catenin拮抗來達到調節的功能。為了進一步了解槲皮素對乳癌細胞增殖和遷移的抑制是否伴隨著PG蛋白表達的上調，我們使用MTT分析法來檢測槲皮素對於人類乳癌細胞MDA-MB-231以及MCF-7存活的影響。我們的結果表明，槲皮素透過濃度依賴性的方式抑制MDA-MB-231以及MCF-7的細胞活性。我們進行Western blot以及細胞免疫螢光染色分析評估槲皮素處理後的MDA-MB-231以及MCF-7細胞中PG的表達。發現槲皮素上調MDA-MB-231以及MCF-7乳癌細胞中PG蛋白的表達，同時也抑制了β-catenin以及細胞週期發展過程中所需的下游蛋白如cyclin D1的蛋白表達，另外也抑制了β-catenin下游的c-myc蛋白表達，以及EMT (epithelial-mesenchymal transition) 相關的標的蛋白表現也呈現下降趨勢。在Wound healing以及Migration實驗中我們觀察到乳癌細胞MDA-MB-231經過槲皮素處理後，細胞傷口癒合以及細胞遷移的能力明顯的下降。我們目前的數據表明，槲皮素可能透過上調PG使得PG能夠與β-catenin拮抗，並進而抑制β-catenin下游跟細胞增殖以及EMT相關的訊號路徑，阻止乳癌細胞的增殖和遷移，我們的研究推測槲皮素或許可藉由提升PG表現與抑制β-catenin訊號傳遞路徑來下調乳癌細胞的轉移與生長，並可作為治療乳癌的化學預防藥劑。

關鍵字

乳癌；人類乳癌細胞MDA-MB-231 ；人類乳癌細胞MCF-7 ；槲皮素；斑珠蛋白； Wnt/β-catenin訊號路徑

並列摘要

Quercetin is a flavonoid found in plants. Evidence in the literature proves that quercetin has a wide range of physiological activities, including anti-inflammatory, antioxidant, and anti-angiogenesis, and shows that quercetin prevents various diseases, such as breast cancer, lung cancer, liver cancer, and brain cancer. Therefore, quercetin plays an important role in the prevention and promotion of health. Plakoglobin (PG, γ-catenin) is a member of the Armadillo proteins family and a structural homolog of β-catenin. In addition to playing a significant structural role in the cell, PG participates in cell signaling regulation. The role of PG in the Wnt/β-catenin pathway is different from that of β-catenin. In fact, most studies suggest that PG has a tumor suppressor role in various cancers and, furthermore, it has an antagonistic effect to β-catenin. PG even executes the regulatory function competing with β-catenin that interacts with intracellular proteins or sequestering transcription factors. To understand whether inhibition of quercetin in proliferation and migration was accompanied by up-regulation of PG protein expression, we first used the MTT assay to detect the effect of quercetin on the survival of human breast cancer MDA-MB-231 and MCF-7 cells. Our results showed that quercetin inhibited the cell viability of MDA-MB-231 and MCF-7 cells in a dose-dependent manner. We performed Western blot analysis and immunofluorescence staining to evaluate PG expression in quercetin-treated MDA-MB-231 and MCF-7 cells. We found that quercetin increased PG protein expression in MDA-MB-231 and MCF-7 cells, while inhibiting cyclin D1 required for cell cycle progression and protein expression of β-catenin substrate proteins such as c-myc and EMT-related target proteins, respectively. We observed that wound healing and cell migration of breast cancer cells MDA-MB-231 decreased significantly after quercetin treatment. Our current data suggest that quercetin can antagonize PG with β-catenin by upregulating PG, thereby inhibiting the substrate signaling pathways of β-catenin related to cell proliferation and EMT, preventing the proliferation and migration capacity of breast cancer cells. We hope to develop quercetin as a leading drug for the treatment of breast cancer or as a new adjuvant for breast cancer patients to reduce the side effects of chemotherapy drugs.

並列關鍵字

breast cancer ； human MDA-MB-231 breast cancer cells ； human MCF-7 breast cancer cells ； Quercetin ； Plakoglobin ； Wnt/β-catenin pathway

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