【Abstract】
Detachment of cancer cells from the primary tumor and formation of spheroids in ascites is required for implantion metastasis in EOC, but the underlying mechanism of this process has not been thoroughly elucidated. To mimic this process, ovarian cancer cells were grown in 3D and 2D culture. Hey and OVCA433 spheroids exhibited decreased cell proliferation and enhanced adhesion and invasion. SMYD3 expression was elevated in ovarian carcinoma spheroids in association with increased H3K4 methylation. Depletion of SMYD3 by transient siRNA, stable shRNA knockdown and the SMYD3 inhibitor BCI-121 all decreased spheroid invasion and adhesion. Gene expression arrays revealed downregulation of integrin family members. Inhibition assays confirmed that invasion and adhesion of spheroids are mediated by ITGB6 and ITGAM. SMYD3-deficient cells regained the ability to invade and adhere following forced overexpression of SMYD3, ITGB6 and ITGAM. However, this biological ability was not restored by forced overexpression of SMYD3 in ITGB6- and/or ITGAM-deficient cancer cells. SMYD3 and H3K4me3 binding at the ITGB6 and ITGAM promoters was increased in spheroids compared with that in monolayer cells, and the binding was decreased when SMYD3 expression was inhibited, consistent with the expression changes in integrins. SMYD3 expression and integrin-mediated adhesion were also activated in an intraperitoneal xenograft model and in EOC patient spheroids. In vivo, SMYD3 knockdown inhibited tumor metastasis and reduced ascites volume in both the intraperitoneal xenograft model and a PDX model. Overall, our results suggest that the SMYD3-H3K4me3-integrin pathway plays a crucial role in ovarian cancer metastasis to the peritoneal surface.
【中文摘要】
在卵巢癌種植轉移過程中,卵巢癌細胞從原發灶脫落並在腹水中形成懸浮球體細胞團,該過程的潛在機制尚未完全闡明。課題組分別將卵巢癌細胞在2D與3D條件下培養以模擬卵巢癌在原發灶與腹水中的生存狀態。卵巢癌細胞Hey和OVCA433的球體細胞較貼壁細胞增殖能力降低,粘附和侵襲能力增強。課題組發現組蛋白甲基化酶SMYD3表達水平與H3K4的甲基化水平在卵巢癌患者腹水懸浮球體細胞中較原發灶組織表達升高。下調SMYD3表達或使用SMYD3抑制劑BCI-121均可降低卵巢癌球體細胞的侵襲和粘附粘附能力。通過基因表達晶片篩選及功能抑制試驗證實,SMYD3通過調節整合素家族ITGB6和ITGAM促進卵巢癌球體細胞侵襲粘附。在下調SMYD3的球體細胞中過表達ITGB6和ITGAM後可恢復其侵襲粘附能力。但在下調ITGB6或ITGAM的球體細胞中過表達SMYD3不能恢復其侵襲粘附能力。與單層細胞相比,球體細胞中ITGB6和ITGAM啟動子上SMYD3和H3K4me3結合能力增加,促進ITGB6和ITGAM表達。在卵巢癌裸鼠模型及PDX模型中均證實SMYD3可抑制卵巢癌種植轉移及腹水形成。因此,課題組研究表明SMYD3-H3K4me3-整合素途徑在卵巢癌種植轉移過程中發揮重要作用。