Abbott D W, Freeman M L, Holt J T
Department of Cell Biology and Pathology, Vanderbilt University, Nashville, TN 37232, USA.
J Natl Cancer Inst. 1998 Jul 1;90(13):978-85. doi: 10.1093/jnci/90.13.978.
The protein product of the BRCA2 gene mediates repair of double-strand breaks in DNA. Because a number of cancer therapies exert cytotoxic effects via the initiation of double-strand breaks, cancers comprised of cells carrying BRCA2 gene mutations may be more amenable to treatment with agents that cause such breaks.
We identified a human pancreatic adenocarcinoma cell line lacking one copy of the BRCA2 gene and containing a mutation (6174delT) in the remaining copy. In vitro and in vivo experiments were conducted with this cell line and with other carcinoma cell lines matched for similar genetic mutations, similar differentiation status, and/or similar carcinoma type to examine double-strand break repair, sensitivity to drugs that induce double-strand breaks, and radiation sensitivity.
BRCA2-defective cells were unable to repair the double-strand DNA breaks induced by ionizing radiation. These cells were also markedly sensitive to mitoxantrone, amsacrine, and etoposide (drugs that induce double-strand breaks) (two-sided P = .002) and to ionizing radiation (two-sided P = .001). Introduction of antisense BRCA2 deoxyribonucleotides into cells possessing normal BRCA2 function led to increased sensitivity to mitoxantrone (two-sided P = .008). Tumors formed by injection of BRCA2-defective cells into nude mice were highly sensitive (>90% tumor size reduction, two-sided P = .002) to both ionizing radiation and mitoxantrone when compared with tumors exhibiting normal BRCA2 function. Histologic analysis of irradiated BRCA2-defective tumors showed a large degree of necrosis compared with that observed for control tumors possessing normal BRCA2 function.
BRCA2-defective cancer cells are highly sensitive to agents that cause double-strand breaks in DNA.
BRCA2基因的蛋白质产物介导DNA双链断裂的修复。由于许多癌症治疗通过引发双链断裂发挥细胞毒性作用，由携带BRCA2基因突变的细胞组成的癌症可能对导致此类断裂的药物更敏感。
我们鉴定出一株人胰腺腺癌细胞系，该细胞系缺失一个BRCA2基因拷贝，且另一个拷贝存在突变（6174delT）。用该细胞系以及与相似基因突变、相似分化状态和/或相似癌类型匹配的其他癌细胞系进行体外和体内实验，以检测双链断裂修复、对诱导双链断裂药物的敏感性以及放射敏感性。
BRCA2缺陷细胞无法修复电离辐射诱导的DNA双链断裂。这些细胞对米托蒽醌、安吖啶和依托泊苷（诱导双链断裂的药物）（双侧P = 0.002）以及电离辐射（双侧P = 0.001）也明显敏感。将反义BRCA2脱氧核苷酸导入具有正常BRCA2功能的细胞会导致对米托蒽醌的敏感性增加（双侧P = 0.008）。与具有正常BRCA2功能的肿瘤相比，将BRCA2缺陷细胞注射到裸鼠体内形成的肿瘤对电离辐射和米托蒽醌均高度敏感（肿瘤大小减少>90%，双侧P = 0.002）。与具有正常BRCA2功能的对照肿瘤相比，对BRCA2缺陷肿瘤进行辐射后的组织学分析显示坏死程度更高。
BRCA2缺陷癌细胞对导致DNA双链断裂的药物高度敏感。
