三陰性 (Triple-negative) 乳癌的轉移能力與復發率極高，是臨床上最難治療的一種乳癌，因為缺乏estrogen receptor (ER)、progesterone receptor (PR) 與human epidermal growth factor receptor 2 (HER2) 基因之表現，使三陰性乳癌對於賀爾蒙療法與標靶治療具有抗性。雖然部分三陰性乳癌患者對於化療藥物如Paclitaxel有不錯的反應，但殘留的癌細胞仍造成三陰性乳癌的復發。且殘留的三陰性乳癌細胞有能力在活體實驗中驅使腫瘤微環境形成，幫助已經潛伏在遠端組織的indolent tumor cells進行上皮細胞-間質細胞轉換 (epithelial-mesenchymal transition，EMT)，加速轉移癌增殖並形成復發，且此種能力是其他類型的乳癌如luminal-type所沒有的。而第一型類胰島素生長因子接受器 (Type I insulin-like growth factor receptor，IGF1R) 訊號傳遞路徑已在細胞和動物實驗中被證實能夠調節三陰性乳癌細胞的EMT轉換，進而加速細胞的侵襲與轉移。因此，若能設計藥物或抗體針對IGF1R訊號傳遞路徑之相關活化調控因子進行抑制，或許能治療或延緩三陰性乳癌的轉移與復發，為病患爭取存活的時間。 Quercetin (槲皮素) 是一種帶有多種生物活性的類黃酮 (flavonoid)，具有抗癌能力，能在細胞或動物實驗中抑制各種致癌物所誘發的上皮細胞癌化。針對乳癌細胞，quercetin可促使人類MCF-7乳癌細胞株之細胞週期停止於S phase，並誘使透過caspase依賴性路徑進行細胞凋亡。Quercetin亦可抑制matrix metalloproteinases (MMPs) 的表現與分泌，進而抑制乳癌細胞的侵襲。另外，quercetin可藉由抑制heat shock protein 27之表現，進而抑制EMT轉換，降低aldehyde dehydrogenase-positive (ALDH+) 之乳癌幹細胞的自我更新 (self-renewal)。但quercetin對於三陰性乳癌EMT轉換與侵襲能力的影響仍尚未釐清，因此，本三年期的研究計劃將針對quercetin是否能夠藉由調節IGF1R訊號路徑的活性，來減少三陰性乳癌細胞的EMT轉換，並抑制三陰性乳癌細胞的轉移等機轉作深入探討。 目前，在我們第一年的初步研究成果中發現quercetin確實能夠在濃度依賴性的條件下抑制MDA-MB-231乳癌細胞中vimentin、fibronetin與vascular endothelial growth factor receptor (VEGFR) 等mesenchymal-like相關標記的表現，並同時促進keratin-18, -19與ZO-1等epithelial-like相關標記表現。證明quercetin確實能夠逆轉MDA-MB-231細胞的EMT轉換。另外，quercetin亦降低MDA-MB-231細胞中IGF1R接受器酪胺酸磷酸化的程度，且抑制IGF1R所調控的EMT相關轉錄因子如snail和slug的表現與轉錄活性，暗示quercetin可能是透過抑制IGF1R訊號路徑的活化來降低三陰性乳癌細胞株的EMT轉換與侵襲。我們將繼續動物實驗的設計與進行，期望動物實驗的研究成果與細胞實驗相符，以驗證quercetin對抗三陰性乳癌轉移與復發的機制，並配合其低毒性和非致癌性之特性，將有助於設計出抗癌效果比quercetin更強的癌症化學治療預防試劑或輔佐治療藥劑。
Insulin-like growth factor I receptor (IGF-IR) signaling is essential for breast cancer progression by elevating the levels and function of transcription repressors ZEB1, snail and slug to allow breast cancer cells undergoing epithelial-to-mesenchymal transition (EMT) and invasion. Quercetin exerts its potent anti-proliferating activities against various types of malignant cells； however, the reversal effect of quercetin on EMT and invasion of breast cancer has not been fully deciphered. Here, we report that quercetin possesses a diminished capacity for the expression of EMT markers, including ZEB1, snail and slug, in a dose-dependent manner in human MDA-MB-453 breast cancer cells. Quercetin also down-regulated the aggressive invasive phonotype of MDA-MB-231 cells, as demonstrated by a cell-based wound healing and a Boyden chamber transwell assay. Noticeably, quercetin increased the levels of CCN6 [Wnt-1-induced signaling protein 3 (WISP3)] and insulin-like growth factor-binding protein 3 (IGFBP3), the two secreted proteins that nullify IGF-1 and the resulting IGF-IR signaling pathway, in conditioned media. In concordance with elevation of CCN6 and IGFBP3, treatment with an equivalent amount of quercetin was sufficient to inhibit the phosphorylation and activation of Akt and ERK1/2, two downstream kinases involving in IGF-IR signaling. Taken together, these preliminary data suggest that quercetin causes the induction of CCN6 and IGFBP3 that contributes to blockade of IGF-IR signaling and the reduced levels of ZEB1, snail and slug, and consequently reverses EMT and invasion phenotype of MDA-MB-231 cells.
