小蘖鹼為一種異喹啉生物鹼，存在於小蘖科植物的根、莖或樹皮中，具有抗心律不整及抗腫瘤的功效。為了找出小蘖鹼在 HER2/neu 過表現細胞中的化學預防分子作用機制，我們分析數個不同 p185HER2/neu 蛋白質表現量的細胞株，結果發現相較於正常 HER2/neu 表現量的細胞株，小蘖鹼會針對 HER2/neu 過表現的細胞株有較高抑制細胞存活率的效果。此外小蘖鹼在 HER2/neu 過表現的細胞株會有依劑量及依時間抑制 p185HER2/neu 蛋白質表現量的情形。進一步觀察發現小蘖鹼會抑制 p185HER2/neu 的活性及其下游 Akt 與 ERK 的活性。此外我們發現小蘖鹼會抑制 p185HER2/neu 過表現的卵巢癌細胞 (SKOV3) 的轉移能力。另外也證明了 EGF 會回覆藉由小蘖鹼所抑制的 MMP2 的活性，而 PI3K 的抑制劑會抑制由 EGF 所回覆的 MMP2 活性。綜合所有的實驗結果可說明，小蘖鹼會促進 p185HER2/neu 蛋白質降解而造成 HER2/neu 過表現細胞的損壞，並藉由抑制PI3K/Akt 訊號路徑進而減弱了由 p185HER2/neu 所調控的轉移情形。 Berberine, an isoquinoline alkaloid, present in the roots, rhizome and stem bark of Berberis species, has been shown to possess potent anti-arrhythmic and anti-turmor properties. To explore the molecular mechanism of the chemopreventive effects of berberine in the HER2/neu-overexpressing cancer cells, we examined several human cancer cell lines having different levels p185HER2/neu expression and found that berberine exhibited much more growth-inhibitory activity in the HER2/neu-overexpressing cancer cells than those cells expressing basal levels of p185HER2/neu. Depletion of p185HER2/neu was also observed in HER2/neu-overexpressing cancer cells in a dose- and time-dependant manner. We also demonstrate that berberine can downregulate the activated form of p185HER2/neu as well as Akt and ERK, downstream substrates of p185HER2/neu. Furthermore, we found that berberine is potent in suppressing transformation phenotype of SKOV3 cells (HER2/neu-overexpressing ovarian cancer cell) including metastasis-associated properties. We also elucidate that EGF specifically restores the activation of MMP2 after its activity was reduced by berberine; the restoration of MMP2 activity was also inhibited by PI3K inhibitor. These finding suggest that berberine can cause HER2/neu-overexoressing cancer cell damage by inducing degradation of p185HER2/neu, and then inhibiting the PI3K/Akt-signaling pathway to attenuate the p185HER2/neu mediated metastasis.
