| Abstract: | 癌症幹細胞假說是癌症研究領域的一個新興概念，在腫瘤中只有一小部分的具有幹細胞特性的癌細胞有能力形成腫瘤。而癌症幹細胞已被證實與腫瘤抗藥性以及癌症轉移具高度的相關性，因此在乳癌研究中，已指出具有高度細胞內 aldehyde dehydrogenase (ALDH) 活性的細胞為乳癌幹細胞 (Breast cancer stem cells, BCSCs)。針對癌症幹細胞的標靶療法被認為是新興的癌症治療方向。在許多癌症中，熱休克蛋白 (Heat shock proteins, HSPs) 有過度表現的情形產生。其與癌症之間的發展，如腫瘤的轉移和存活以及預後有密切的關係。在許多癌症中也有 HSP27 有過量的表現，如乳癌、肝癌、前列腺癌和卵巢癌等，表示 HSP27 在這些癌症中可能扮演重要的角色。檞黃素是植物性多酚類化合物，屬於類黃酮的一種。已指出具有抗氧化、抗癌、抗發炎和保護心血管等作用。最近，檞黃素已指出藉由抑制 HSP27 可降低肺癌幹細胞的抗藥性。到目前為止，檞黃素影響乳癌幹細胞的作用還不明確。
當 AS-B145 及 AS-B244 乳癌細胞株處理檞黃素 ， ALDH 陽性細胞族群有減少的現象，檞黃素並可抑制癌細胞中的乳癌幹細胞自我更新的能力以及抑制乳癌細胞移動能力。在分子層次上，檞黃素可減少 HSP27 蛋白的表現量。由抗體微陣列分析乳癌幹細胞內磷酸化之 HSP27 以及其上游磷酸? p38 MAPK 的磷酸化皆明顯高於非幹細胞之乳癌細胞。利用 HSP27 specific siRNA 方式 ， AS-B145 ALDH 陽性細胞族群、自我更新的能力和細胞移動能力都與處理檞黃素類似。而降低 HSP27 的表現量，細胞生長及細胞的存活都有減少的現象。了解 HSP27 如何影響維持乳癌幹細胞的分子機制是有趣的研究課題並可能提供乳癌治療上的新方向。
Cancer stem cell (CSC) hypothesis is an emerging area in cancer research which concepts as only a small population of cancer cells with stem cell-like characteristics is responsible for tumorigenesis. CSCs have been reported to be associated with chemoresistance, radioresistance and metastasis of cancer. Targeting cancer stem cells has been considered as a new strategy in cancer therapy recently. In breast cancer research, breast cancer stem cells (BCSCs) have been identified as cells with a high level of intracellular aldehyde dehydrogenase (ALDH) activity. Heat shock proteins (HSPs) are overexpressed in a wide range of human cancers. Their expression is highly associated with cancer development, such as metastasis and poor prognosis of cancer patients. Many cancer cells have markedly increased heat shock protein 27(HSP27) levels, such as breast, liver, prostate and ovarian cancer. HSP27 may play an important role in these cancers. Quercetin is a phytochemical polyphenolic compound which is known as a flavonoid and has been reported with antioxidant, anticarcinogenic, anti-inflammatory, and cardioprotective activities. Recently, quercetin has been proved to suppress drug resistance of lung cancer stem cells by inhibiting HSP27. Until now, the effect of quercetin in targeting BCSCs remains unknown. Here we demonstrated that quercetin exhibits effect in targeting BCSCs.
The ALDH+ population of two breast cancer cell lines, AS-B145 and AS-B244, was decreased by quercetin in dose dependent manner. The cell migration of AS-B145 or AS-B244 was also inhibited by quercetin. Furthermore, the mammosphere formation capacity, which represents the self renewal a ability of BCSCs, two cell lines were dose dependently suppressed by quercetin. In the molecular level, the HSP27 expression was inhibited by quercetin with western blot analysis. By antibody array method, the phosphorylation of HSP27 and its upstream kinase p38MAPK was increased in ALDH+ BCSCs in comparison with ALDH- non-BCSCs. Using HSP27 specific siRNA, ALDH+ population, cell migration and mammosphere formation of HSP27 knockdown AS-B145 cells were also decreased to the level which was similar as quercetin treatment. The cell growth and cell survival of AS-B145 cells were also decreased after knockdown of HSP27. Further investigation of the molecular mechanisms of how HSP27 influence the maintenance of BCSCs will be an interesting research topic and it may provide a new insight in breast cancer therapy. |
