Cancer Research Institute, Tomsk National Research Medical Center of the Russian Academy of Sciences, 634009, Tomsk, Russia.
Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences, 630090, Novosibirsk, Russia.
J Gastrointest Cancer. 2024 Sep;55(3):1190-1198. doi: 10.1007/s12029-024-01066-y. Epub 2024 Jun 3.
Rectal cancer (RC) occupies a leading position in the structure of oncological morbidity and mortality. Aberrant methylation of tumor-suppressor genes and hypomethylation of retrotransposons were shown to be detectable in cell-free DNA, circulating in the blood (cfDNA) of cancer patients, indicating the possibility to use them as diagnostic and prognosis markers.
Evaluation of the changes in the methylation level of LINE-1 elements and SEPTIN9 and IKZF1 genes in the cell-surface-bound cfDNA (csb-cfDNA) from the blood of RC patients after antitumor therapy at a long-term follow-up.
Blood samples were obtained from RC patients (n = 25) before treatment, after preoperative chemotherapy (3 courses according to the XELOX scheme), 10-15 days after surgery, and every 3 months during 12 months of dynamic observation. The methylation level of LINE-1, SEPTIN9, and IKZF1 in the csb-cfDNA was evaluated by quantitative methyl-specific PCR.
The LINE-1 methylation level in the csb-cfDNA increased 1.6 times in RC patients after chemotherapy and 3 times after tumor resection versus methylation level before therapy. The SEPTIN9 gene methylation level in the csb-cfDNA decreased by 1.7 times in RC patients after chemotherapy and by 2.3 times after tumor resection compared with the values before the treatment. The IKZF1 gene methylation level decreased by 2 times in RC patients after combined therapy. Notably, all patients with relapses (n = 5) showed an increase in methylation level for the SEPTIN9 and IKZF1 genes and a decrease of methylation level for the LINE-1 elements by 2 times or more in comparison with the level 10-15 days after surgery. There were no changes in the circulating SEPTIN9, IKZF1, and LINE-1 methylation levels during the 12-month follow-up period after the combined therapy of RC patients (n = 20) without relapses.
The results indicate that SEPTIN9, IKZF1, and LINE-1 methylation levels in the csb-cfDNA are potential markers of the effectiveness of antitumor therapy and early detection of relapse in RC patients.
直肠癌（RC）在肿瘤发病率和死亡率结构中占据主导地位。在癌症患者的循环无细胞 DNA（cfDNA）中，已显示肿瘤抑制基因的异常甲基化和反转录转座子的低甲基化是可检测到的，这表明它们有可能作为诊断和预后标志物。
评估在长期随访中，RC 患者经过抗肿瘤治疗后，细胞表面结合 cfDNA（csb-cfDNA）中 LINE-1 元件和 SEPTIN9、IKZF1 基因甲基化水平的变化。
从 25 例 RC 患者（治疗前、术前化疗 3 个疗程[XELOX 方案]、手术后 10-15 天和 12 个月动态观察期间每 3 个月）采集血样。采用定量甲基特异性 PCR 评估 csb-cfDNA 中 LINE-1、SEPTIN9 和 IKZF1 的甲基化水平。
RC 患者化疗后和肿瘤切除后 csb-cfDNA 中的 LINE-1 甲基化水平分别增加了 1.6 倍和 3 倍，与治疗前相比。RC 患者化疗后和肿瘤切除后 csb-cfDNA 中的 SEPTIN9 基因甲基化水平分别降低了 1.7 倍和 2.3 倍，与治疗前相比。联合治疗后，IKZF1 基因甲基化水平降低了 2 倍。值得注意的是，所有复发患者（n=5）均表现出 SEPTIN9 和 IKZF1 基因的甲基化水平升高，与手术后 10-15 天相比，LINE-1 元件的甲基化水平降低了 2 倍或更多。在 20 例无复发的 RC 患者联合治疗后 12 个月的随访期间，循环 SEPTIN9、IKZF1 和 LINE-1 甲基化水平没有变化。
结果表明，csb-cfDNA 中 SEPTIN9、IKZF1 和 LINE-1 的甲基化水平是 RC 患者抗肿瘤治疗效果和早期复发检测的潜在标志物。
