Hardingham J E, Kotasek D, Sage R E, Eaton M C, Pascoe V H, Dobrovic A
Department of Hematology-Oncology, Queen Elizabeth Hospital, Woodville, South Australia.
Mol Med. 1995 Nov;1(7):789-94.
Recurrent and metastatic carcinoma of the colorectum remains a major problem, with survival at 5 years post curative resection still only about 50%. Moreover, up to 30% of patients who present with early stage disease also relapse and die within 5 years, suggesting the presence of micrometastatic disease at diagnosis. One route of metastatic spread is via the blood stream, hence the detection of tumor cells in blood is likely to provide an important predictive tool with respect to relapse of disease. We have developed a sensitive molecular technique to identify tumor cells in blood using mutations in codon 12 of the K-ras gene as a marker.
Twenty-seven patients whose tumor carried a mutation in codon 12 of K-ras were studied for the presence of tumor cells in perioperative peripheral blood samples. Immunomagnetic beads, labeled with an epithelial-specific antibody, were used to harvest epithelial cells from blood. K-ras mutations were identified in this selected population using a polymerase chain reaction (PCR)-based analysis (immunobead-PCR).
Circulating K-ras mutant cells were detected in 9 or 27 patients; seven of these nine patients have since died due to recurrent or metastatic disease. Mutant cells were not detected in 18 patients, and 16 or 18 have remained disease free (median follow-up: 16 months; range: 7-42 months). Kaplan-Meier analysis showed that detection of K-ras mutant cells in bloods was associated with significantly reduced disease-free survival (p = 0.0001).
This study indicates that detection of circulating tumor cells perioperatively by immunobead-PCR provides a sensitive prognostic marker for recurrent and metastatic colorectal cancer.
结直肠癌的复发和转移仍然是一个主要问题，根治性切除术后5年生存率仍仅约为50%。此外，高达30%的早期疾病患者也会在5年内复发并死亡，这表明在诊断时存在微转移疾病。转移扩散的一条途径是通过血流，因此检测血液中的肿瘤细胞可能为疾病复发提供一个重要的预测工具。我们已经开发出一种灵敏的分子技术，利用K-ras基因第12密码子的突变作为标记来识别血液中的肿瘤细胞。
对27例肿瘤携带K-ras基因第12密码子突变的患者，研究其围手术期外周血样本中肿瘤细胞的存在情况。用标记上皮特异性抗体的免疫磁珠从血液中收集上皮细胞。使用基于聚合酶链反应（PCR）的分析方法（免疫磁珠-PCR）在这一选定人群中鉴定K-ras突变。
27例患者中有9例检测到循环K-ras突变细胞；这9例患者中有7例后来因复发或转移性疾病死亡。18例患者未检测到突变细胞，其中16例在18例中无疾病复发（中位随访时间：16个月；范围：7 - 42个月）。Kaplan-Meier分析表明，血液中检测到K-ras突变细胞与无病生存率显著降低相关（p = 0.0001）。
本研究表明，通过免疫磁珠-PCR围手术期检测循环肿瘤细胞可为复发和转移性结直肠癌提供一个灵敏的预后标志物。
