a Graduate Institute of Food Safety Management , National Pingtung University of Science and Technology , Pingtung , Taiwan.
b Department of Orthopedics , Kaohsiung Municipal Ta-Tung Hospital , Kaohsiung , Taiwan.
Cell Cycle. 2018;17(17):2175-2186. doi: 10.1080/15384101.2018.1520565. Epub 2018 Sep 22.
We previously demonstrated that Bim is the main BH3-only protein replacing Bak/Bax from Bcl-xl to activate apoptosis in a p53-independent manner in response to doxorubicin in prostate cancer. However, the comparison of doxorubicin treatment between LNCaP cells carrying p53-wild type and PC3 cells carrying p53-null suggested that p53 might be essential for maximizing apoptosis. Inhibition of ATM did not affect doxorubicin-induced apoptosis. Overexpression of p53 did not affect ABT-263-induced apoptosis and nevertheless, the combination of doxorubicin with ABT-263 induced higher apoptotic responses than did doxorubicin or ABT-263 alone. These results advocated that doxorubicin-induced DNA damage controls p53 function for intensifying apoptosis. Indeed, overexpression of p53 only enhanced apoptosis under conditions of severe DNA damage induced by high concentrations of doxorubicin in LNCaP cells. Immunofluorescence staining showed vague γH2AX foci and enlarged nuclei in LNCaP cells in response to high concentrations of doxorubicin, en route to apoptosis. In addition, our results revealed that the apoptosis in response to DNA replication stress induced by CFS-1686, a catalytic inhibitor of topoisomerase, is p53-independent. Interestingly, the combination of doxorubicin with CFS-1686 generated DNA damage and replication stress simultaneously, resulting in a synergistic apoptotic effect in prostate cancer cells. Thus, we concluded that p53 is a sensor for enhanced apoptosis in response to DNA damage stress, not DNA replication stress, at least in prostate cancer.
我们之前已经证明，在前列腺癌细胞中，Bim 是主要的 BH3 仅有蛋白，可替代 Bcl-xl 中的 Bak/Bax，从而在不依赖 p53 的情况下，通过多柔比星激活细胞凋亡。然而，LNCaP 细胞（携带野生型 p53）和 PC3 细胞（携带 p53 缺失型）接受多柔比星处理的比较表明，p53 可能是使细胞凋亡最大化的关键。抑制 ATM 激酶不影响多柔比星诱导的细胞凋亡。过表达 p53 不影响 ABT-263 诱导的细胞凋亡，但多柔比星与 ABT-263 的联合应用比单独使用多柔比星或 ABT-263 诱导出更高的细胞凋亡反应。这些结果表明，多柔比星诱导的 DNA 损伤控制 p53 功能以增强细胞凋亡。事实上，仅在 LNCaP 细胞中，高浓度多柔比星诱导的严重 DNA 损伤条件下，过表达 p53 才增强细胞凋亡。免疫荧光染色显示，LNCaP 细胞对高浓度多柔比星反应时出现模糊的 γH2AX 焦点和细胞核增大，这是细胞凋亡的迹象。此外，我们的结果表明，CFS-1686（拓扑异构酶催化抑制剂）诱导的 DNA 复制应激引起的细胞凋亡不依赖于 p53。有趣的是，多柔比星与 CFS-1686 的联合应用同时产生了 DNA 损伤和复制应激，从而在前列腺癌细胞中产生协同的细胞凋亡效应。因此，我们得出结论，p53 是增强对 DNA 损伤应激而不是 DNA 复制应激反应的凋亡的传感器，至少在前列腺癌中是这样。
