Phenotypic characterization of circulating tumor cells in the peripheral blood of patients with small cell lung cancer

BackgroundTo evaluate the phenotypic heterogeneity of circulating tumor cells (CTCs) based on the expression of proliferative, apoptotic and Epithelial-to-Mesenchymal Transmission (EMT) markers during front-line treatment in patients with small cell lung cancer (SCLC) and to evaluate their clinical relevance.MethodsCTCs from 108 chemotherapy-naïve patients with SCLC were analyzed by double immunofluorescence staining using anti-Ki67, anti-M30, anti-Vimentin along with anti-CKs antibodies. In 83 patients CTCs were also enumerated using the CellSearch.ResultsSequential samples were available from 76 and 48 patients after one-treatment cycle and on disease progression (PD), respectively, for immunofluorescence and from 50 and 36 patients after one-cycle and on PD, respectively, for CellSearch. At baseline, 60.2% of the patients had detectable CTCs by either method. Both proliferative (CK67+) and non-proliferative (Ki67-), apoptotic (M30+) and non-apoptotic (M30-) as well as EMT (Vim+) CTCs were present in the same patient. Among 22 patients without detectable CTCs by CellSearch, CK+/Ki67+ and CK+/Vim+ CTCs could be detected in 6 (27.3%) and 6 (27.3%) patients, respectively. One-chemotherapy cycle reduced both the incidence of detection (p0.001) and the absolute number (p0.001) of CTCs; conversely, on PD both the incidence of detection and the number of CTCs were significantly increased (p = 0.002 and p = 0.04, respectively). Multivariate analysis revealed that the increased number of Vim+ CTCs at baseline and of non-apoptotic CTCs on PD could be emerged as independent prognostic factors associated with decreased OS(p = 0.009 and p = 0.023, respectively).ConclusionsCK+/Ki67+, CK+/M30+ and CK+/Vim+ CTCs represent distinct subpopulations of CTCs in patients with SCLC, can be detected even in the absence of detectable CTCs by CellSearch; CK+/Ki67+ and CK+/Vim+ CTCs are associated with unfavorable clinical outcome.背景 本研究旨在评估小细胞肺癌（small cell lung cancer, SCLC）患者一线治疗期间，循环肿瘤细胞（circulating tumor cells, CTCs）基于增殖、凋亡及上皮-间质转化（epithelial-to-mesenchymal transition, EMT）标志物表达的表型异质性，并评估其临床相关性。 方法 对108例初治小细胞肺癌患者的循环肿瘤细胞，采用抗Ki67、抗M30、抗波形蛋白（Vimentin）及抗细胞角蛋白（CKs）抗体开展双重免疫荧光染色分析；其中83例患者的循环肿瘤细胞还通过CellSearch检测系统完成了计数。 结果 分别有76例、48例患者在完成1个治疗周期后及疾病进展（disease progression, PD）时提供了序贯样本，用于免疫荧光检测；另有50例、36例患者在完成1个治疗周期后及疾病进展时提供了序贯样本，用于CellSearch检测。基线时，60.2%的患者可通过任一方法检出循环肿瘤细胞。同一患者体内可同时存在增殖型（Ki67+）与非增殖型（Ki67-）、凋亡型（M30+）与非凋亡型（M30-）以及间质表型（Vim+）的循环肿瘤细胞。在22例经CellSearch检测未检出循环肿瘤细胞的患者中，分别有6例（27.3%）、6例（27.3%）可检测到CK+/Ki67+及CK+/Vim+循环肿瘤细胞。1个化疗周期后，循环肿瘤细胞的检出率（p<0.001）与绝对计数（p<0.001）均显著降低；反之，疾病进展时，循环肿瘤细胞的检出率与绝对计数均显著升高（分别为p=0.002与p=0.04）。多因素分析显示，基线时Vim+循环肿瘤细胞数量增多、疾病进展时非凋亡型循环肿瘤细胞数量增多，可作为与总生存期（overall survival, OS）缩短相关的独立预后因素（分别为p=0.009与p=0.023）。 结论 CK+/Ki67+、CK+/M30+及CK+/Vim+循环肿瘤细胞代表了小细胞肺癌患者体内循环肿瘤细胞的不同亚群，即便在CellSearch检测呈阴性的样本中也可被检出；CK+/Ki67+与CK+/Vim+循环肿瘤细胞与不良临床预后相关。