Jahr S, Hentze H, Englisch S, Hardt D, Fackelmayer F O, Hesch R D, Knippers R
Department of Biology, Universität Konstanz, Germany.
Cancer Res. 2001 Feb 15;61(4):1659-65.
Increased levels of DNA fragments have frequently been found in the blood plasma of cancer patients. Published data suggest that only a fraction of the DNA in blood plasma is derived from cancer cells. However, it is not known how much of the circulating DNA is from cancer or from noncancer cells. By quantitative methylation-specific PCR of the promoter region of the CDKN2A tumor suppressor gene, we were able to quantify the fraction of plasma DNA derived from tumor cells. In the plasma samples of 30 unselected cancer patients, we detected quantities of tumor DNA from only 3% to as much as 93% of total circulating DNA. We investigated possible origins of nontumor DNA in the plasma and demonstrate here a contribution of T-cell DNA in a few cases only. To investigate the possibility that plasma DNA originates from apoptotic or necrotic cells, we performed studies with apoptotic (staurosporine) and necrotic (staurosporine plus oligomycin) cells in vitro and with mice after induction of apoptotic (anti-CD95) or necrotic (acetaminophen) liver injury. Increasing amounts of DNA were found to be released in the supernatants of cells and in the blood plasma samples of treated animals. A clear discrimination of apoptotic and necrotic plasma DNA was possible by gel electrophoresis. The same characteristic patterns of DNA fragments could be identified in plasma derived from different cancer patients. The data are consistent with the possibility that apoptotic and necrotic cells are a major source for plasma DNA in cancer patients.
癌症患者血浆中经常发现DNA片段水平升高。已发表的数据表明，血浆中的DNA只有一小部分来自癌细胞。然而，尚不清楚循环DNA中有多少来自癌细胞或非癌细胞。通过对CDKN2A肿瘤抑制基因启动子区域进行定量甲基化特异性PCR，我们能够量化源自肿瘤细胞的血浆DNA比例。在30例未经选择的癌症患者的血浆样本中，我们检测到肿瘤DNA的量占总循环DNA的3%至93%。我们研究了血浆中非肿瘤DNA的可能来源，仅在少数情况下证明了T细胞DNA的作用。为了研究血浆DNA源自凋亡或坏死细胞的可能性，我们在体外对凋亡（星形孢菌素）和坏死（星形孢菌素加寡霉素）细胞以及诱导凋亡（抗CD95）或坏死（对乙酰氨基酚）肝损伤后的小鼠进行了研究。发现细胞上清液和处理动物的血浆样本中释放的DNA量增加。通过凝胶电泳可以清楚地区分凋亡和坏死的血浆DNA。在来自不同癌症患者的血浆中可以鉴定出相同的DNA片段特征模式。这些数据与凋亡和坏死细胞是癌症患者血浆DNA的主要来源这一可能性一致。
