Division of Mathematics and Computer Science, University of South Carolina Upstate, Spartanburg, SC, USA.
Cell Cycle. 2013 Apr 1;12(7):1071-82. doi: 10.4161/cc.24067. Epub 2013 Mar 1.
As DNA damage checkpoints are barriers to carcinogenesis, G(2) checkpoint function was quantified to test for override of this checkpoint during melanomagenesis. Primary melanocytes displayed an effective G(2) checkpoint response to ionizing radiation (IR)-induced DNA damage. Thirty-seven percent of melanoma cell lines displayed a significant defect in G(2) checkpoint function. Checkpoint function was melanoma subtype-specific with "epithelial-like" melanoma lines, with wild type NRAS and BRAF displaying an effective checkpoint, while lines with mutant NRAS and BRAF displayed defective checkpoint function. Expression of oncogenic B-Raf in a checkpoint-effective melanoma attenuated G(2) checkpoint function significantly but modestly. Other alterations must be needed to produce the severe attenuation of G(2) checkpoint function seen in some BRAF-mutant melanoma lines. Quantitative trait analysis tools identified mRNA species whose expression was correlated with G(2) checkpoint function in the melanoma lines. A 165 gene signature was identified with a high correlation with checkpoint function (p < 0.004) and low false discovery rate (≤ 0.077). The G(2) checkpoint gene signature predicted G(2) checkpoint function with 77-94% accuracy. The signature was enriched in lysosomal genes and contained numerous genes that are associated with regulation of chromatin structure and cell cycle progression. The core machinery of the cell cycle was not altered in checkpoint-defective lines but rather numerous mediators of core machinery function were. When applied to an independent series of primary melanomas, the predictive G(2) checkpoint signature was prognostic of distant metastasis-free survival. These results emphasize the value of expression profiling of primary melanomas for understanding melanoma biology and disease prognosis.
由于 DNA 损伤检查点是致癌作用的障碍，因此量化 G(2)检查点功能以测试黑色素瘤发生过程中对该检查点的超越。原代黑素细胞对电离辐射（IR）诱导的 DNA 损伤显示出有效的 G(2)检查点反应。37%的黑素瘤细胞系显示出 G(2)检查点功能的显著缺陷。检查点功能是黑素瘤亚型特异性的，“上皮样”黑素瘤系具有野生型 NRAS 和 BRAF，显示出有效的检查点，而具有突变型 NRAS 和 BRAF 的系显示出有缺陷的检查点功能。在具有有效检查点的黑素瘤中表达致癌性 B-Raf 会显著但适度地减弱 G(2)检查点功能。其他改变可能需要产生在一些 BRAF 突变黑素瘤系中观察到的 G(2)检查点功能的严重衰减。定量性状分析工具鉴定了与黑素瘤系中 G(2)检查点功能相关的 mRNA 种类。鉴定出一个与检查点功能高度相关（p < 0.004）且假发现率低（≤ 0.077）的 165 个基因特征。G(2)检查点基因特征预测 G(2)检查点功能的准确率为 77-94%。该特征在溶酶体基因中富集，包含许多与染色质结构和细胞周期进程调节相关的基因。在检查点缺陷系中，细胞周期的核心机制没有改变，而是核心机制功能的许多介质发生了改变。当应用于独立的原发性黑素瘤系列时，预测 G(2)检查点的特征对无远处转移生存是预后的。这些结果强调了原发性黑素瘤表达谱分析对于理解黑色素瘤生物学和疾病预后的价值。
