Bartholomeusz Chandra, Itamochi Hiroaki, Yuan Linda X H, Esteva Francisco J, Wood Christopher G, Terakawa Naoki, Hung Mien-Chie, Ueno Naoto T
Breast Cancer Translational Research Laboratory, The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Cancer Res. 2005 Sep 15;65(18):8406-13. doi: 10.1158/0008-5472.CAN-05-1754.
We are currently conducting clinical trials of E1A gene therapy for patients with ovarian cancer. The adenovirus type 5 E1A gene suppresses growth of ovarian cancer cells that overexpress HER-2/neu (HER2) and growth of some--but not all--that express low HER2. In HER2-overexpressing cells, suppression by E1A is predominantly by down-regulation of HER2, but the mechanism in low HER2-expressing cells is not fully understood. The adenoviral E1B protein has sequential and functional homology to Bcl-2 and prolongs the viability of adenovirus host cells by inhibiting E1A-induced apoptosis. Bcl-2 is overexpressed in ovarian cancer and participates in chemoresistance; we hypothesized that Bcl-2 inhibits E1A-induced apoptosis leading to resistance to E1A gene therapy. E1A suppressed colony formation of ovarian cancer cells that express low levels of Bcl-2 and HER2 (OVCAR-3 and OVCA 433), but enhanced colony formation in low HER2-, high Bcl-2-expressing ovarian cancer cells (2774 and HEY). Treating 2774 or HEY cells with antisense oligonucleotide Bcl-2 (Bcl-2-ASO) did not reduce cell viability. E1A combined with Bcl-2-ASO led to significant decreases in cell viability resulting from increased apoptosis relative to cells treated with E1A alone (P < 0.05). The increase in apoptosis was partly due to cytochrome c release and subsequently caspase-9 activation by Bcl-2-ASO. Finally, in an ovarian cancer xenograft model, treatment with Bcl-2-ASO did not prolong survival, but E1A plus Bcl-2-ASO did (P < 0.001). In conclusion, ovarian tumors overexpressing Bcl-2 may not respond well to E1A gene therapy, but treatment with a combination of E1A and Bcl-2-ASO may overcome this resistance.
我们目前正在对卵巢癌患者进行E1A基因疗法的临床试验。5型腺病毒E1A基因可抑制过表达HER-2/neu（HER2）的卵巢癌细胞的生长以及部分（而非全部）低表达HER2的细胞的生长。在HER2过表达的细胞中，E1A的抑制作用主要是通过下调HER2实现的，但低HER2表达细胞中的机制尚不完全清楚。腺病毒E1B蛋白与Bcl-2具有序列和功能同源性，并通过抑制E1A诱导的凋亡来延长腺病毒宿主细胞的存活期。Bcl-2在卵巢癌中过表达并参与化疗耐药；我们推测Bcl-2抑制E1A诱导的凋亡从而导致对E1A基因疗法产生耐药。E1A抑制了低表达Bcl-2和HER2的卵巢癌细胞（OVCAR-3和OVCA 433）的集落形成，但增强了低HER2、高Bcl-2表达的卵巢癌细胞（2774和HEY）的集落形成。用反义寡核苷酸Bcl-2（Bcl-2-ASO）处理2774或HEY细胞并没有降低细胞活力。E1A与Bcl-2-ASO联合使用导致细胞活力显著下降，相对于单独用E1A处理的细胞，凋亡增加（P<0.05）。凋亡增加部分是由于细胞色素c释放以及随后Bcl-2-ASO激活了caspase-9。最后，在卵巢癌异种移植模型中，用Bcl-2-ASO治疗并没有延长生存期，但E1A加Bcl-2-ASO则延长了生存期（P<0.001）。总之，过表达Bcl-2的卵巢肿瘤可能对E1A基因疗法反应不佳，但E1A和Bcl-2-ASO联合治疗可能克服这种耐药性。
