Department of Radiation Oncology, University of Tübingen, Hoppe-Seyler-Straße 3, D-72076 Tübingen, Germany.
Radiat Oncol. 2010 Nov 16;5:108. doi: 10.1186/1748-717X-5-108.
The phosphatidylinositol-3-kinase (PI3K)/Akt pathway is frequently deregulated in prostate cancer and associated with neoplastic transformation, malignant progression, and enhanced resistance to classical chemotherapy and radiotherapy. Thus, it is a promising target for therapeutic intervention. In the present study, the cytotoxic action of the Akt inhibitor Erufosine (ErPC3) was analyzed in prostate cancer cells and compared to the cytotoxicity of the PI3K inhibitor LY294002. Moreover, the efficacy of combined treatment with Akt inhibitors and ionizing radiation in prostate cancer cells was examined.
Prostate cancer cell lines PC3, DU145, and LNCaP were treated with ErPC3 (1-100 µM), LY294002 (25-100 µM), irradiated (0-10 Gy), or subjected to combined treatments. Cell viability was determined by the WST-1 assay. Apoptosis induction was analyzed by flow cytometry after staining with propidium iodide in a hypotonic citrate buffer, and by Western blotting using antibodies against caspase-3 and its substrate PARP. Akt activity and regulation of the expression of Bcl-2 family members and key downstream effectors involved in apoptosis regulation were examined by Western blot analysis.
The Akt inhibitor ErPC3 exerted anti-neoplastic effects in prostate cancer cells, however with different potency. The anti-neoplastic action of ErPC3 was associated with reduced phosphoserine 473-Akt levels and induction of apoptosis. PC3 and LNCaP prostate cancer cells were also sensitive to treatment with the PI3K inhibitor LY294002. However, the ErPC3-sensitive PC3-cells were less susceptible to LY294002 than the ErPC3-refractory LNCaP cells. Although both cell lines were largely resistant to radiation-induced apoptosis, both cell lines showed higher levels of apoptotic cell death when ErPC3 was combined with radiotherapy.
Our data suggest that constitutive Akt activation and survival are controlled by different different molecular mechanisms in the two prostate cancer cell lines - one which is sensitive to the Akt-inhibitor ErPC3 and one which is more sensitive to the PI3K-inhibitor LY294002. Our findings underline the importance for the definition of predictive biomarkers that allow the selection patients that may benefit from the treatment with a specific signal transduction modifier.
磷酸肌醇-3-激酶（PI3K）/Akt 通路在前列腺癌中经常失调，与肿瘤转化、恶性进展以及对经典化疗和放疗的耐药性增强有关。因此，它是治疗干预的一个有前途的靶点。在本研究中，分析了 Akt 抑制剂 Erufosine（ErPC3）在前列腺癌细胞中的细胞毒性作用，并与 PI3K 抑制剂 LY294002 的细胞毒性进行了比较。此外，还研究了 Akt 抑制剂与电离辐射联合治疗在前列腺癌细胞中的疗效。
用 ErPC3（1-100µM）、LY294002（25-100µM）、照射（0-10Gy）或联合处理处理前列腺癌细胞系 PC3、DU145 和 LNCaP。通过 WST-1 测定法测定细胞活力。通过碘化丙啶在低渗柠檬酸盐缓冲液中的染色后用流式细胞术分析细胞凋亡诱导，并通过 Western blot 分析用针对半胱天冬酶-3及其底物 PARP 的抗体分析。通过 Western blot 分析检测 Akt 活性以及 Bcl-2 家族成员的表达调控和参与凋亡调控的关键下游效应子。
Akt 抑制剂 ErPC3 在前列腺癌细胞中发挥抗肿瘤作用，但效力不同。ErPC3 的抗肿瘤作用与磷酸丝氨酸 473-Akt 水平降低和细胞凋亡诱导有关。PC3 和 LNCaP 前列腺癌细胞也对 PI3K 抑制剂 LY294002 敏感。然而，ErPC3 敏感的 PC3 细胞对 LY294002 的敏感性低于 ErPC3 抗性的 LNCaP 细胞。尽管两种细胞系对辐射诱导的凋亡均有很大的抗性，但当 ErPC3 与放射治疗联合使用时，两种细胞系均显示出更高水平的凋亡细胞死亡。
我们的数据表明，在两种前列腺癌细胞系中，组成性 Akt 激活和存活受不同的分子机制控制，一种对 Akt 抑制剂 ErPC3 敏感，另一种对 PI3K 抑制剂 LY294002 更敏感。我们的研究结果强调了定义预测生物标志物的重要性，这些生物标志物允许选择可能从特定信号转导修饰剂治疗中受益的患者。
