Characterization of DLL3-positive circulating tumor cells (CTCs) in patients with small cell lung cancer (SCLC) and evaluation of their clinical relevance during front-line treatment.

OBJECTIVES: The aim of the study was to characterize and evaluate the presence of DLL3-positive Circulating Tumor Cells (CTCs) in SCLC patients receiving front-line chemotherapy and assess their clinical relevance. MATERIALS AND METHODS: Peripheral blood was obtained from treatment-naïve patients with SCLC (n = 108 patients), after one etoposide/platinum cycle (n = 68 patients) and on disease progression (n = 48 patients). Immunofluorescence staining using antibodies against the DLL3, cytokeratins (CK), CD45 and vimentin (Vim) was used for the detection and characterization of CTCs. RESULTS: Before treatment, 74.1% of patients had detectable DLL3+/CD45- CTCs. One-treatment cycle significantly decreased both the detection rate (p < 0.001) and the absolute number (p < 0.001) of DLL3+/CD45- CTCs. Triple immunofluorescence staining using anti-CK, anti-Vim and anti-DLL3 antibodies revealed an important CTC heterogeneity since DLL3 could be detected in Vim+, Vim-, CK+ and CK- CTCs. On disease progression, both the detection rate and the absolute number of DLL3+/CD45- CTCs were significantly increased compared to post-1st cycle values (p < 0.001 and p = 0.002, respectively). In addition, 22.7% of patients had detectable DLL3+/CD45- cells which could not be captured by the CellSearch assay. In multivariate analysis, the detection of DLL3+/CD45- CTCs at baseline was significantly associated with decreased progression-free survival (HR = 10.8; p = 0.005) whereas their detection on disease progression was associated with decreased overall survival (HR: 28.2; p = 0.016). CONCLUSIONS: These findings demonstrate an important heterogeneity of CTCs, based on the expression of CK, Vim and DLL3, in patients with SCLC and the changes of DLL3+/CD45- CTCs during treatment seem to be a dynamic biomarker associated with patients' clinical outcome.

Bcl-2 expression in circulating tumor cells (CTCs) of patients with small cell lung cancer (SCLC) receiving front-line treatment.

INTRODUCTION: To investigate the presence of Bcl-2+CTCs in chemotherapy-naïve SCLC patients and their clinical relevance during front-line treatment. METHODS: Peripheral blood was obtained from 66 consecutive-patients before chemotherapy administration, after one-cycle and at relapse. CTCs were detected by CellSearch and immunofluorescence using anti-Bcl-2, anti-M30, anti-cytokeratins(CK), anti-CD45 and anti-vimentin(Vim) antibodies. RESULTS: Before treatment, CTCs were detected in 62.1% and 72.7% of patients using the CellSearch and immunofluorescence (Bcl-2+/CD45-), respectively. One-treatment cycle significantly decreased both CTCs' detection rate(p < 0.001) and their absolute number (p < 0.001). On relapse, both the number of positive-patients and the absolute number of CTC subpopulations were significantly increased, compared to post-1st cycle (CellSearch: p = 0.002 and immunofluorescence: p < 0.001). Immunofluorescence revealed an important CTC heterogeneity (Bcl2+/Vim+, Bcl2+/Vim-, Bcl2+/CK+, Bcl2+/CK- and Bcl2+/M30- CTCs). Moreover, 50.0% of patients without detectable CTCs by CellSearch had detectable Bcl-2+/CD45- cells. Multivariate analysis revealed a significant association between Bcl-2+/CD45-cells at baseline and PFS (HR = 4.5;p = 0.005) and OS (HR: 4.3; p = 0.001). Bcl-2+/CD45-cells after one-treatment cycle were significantly associated with shorter OS (HR: 13.9; p = 0.007). CONCLUSIONS: These results demonstrate an important phenotypic CTCs heterogeneity based on the co-expression of Bcl-2, CK, Vim and M30 in SCLC patients. The changes of Bcl-2+/CD45- CTCs during treatment seem to be a dynamic biomarker associated with treatment efficacy and patients' clinical outcome.

Dynamic changes of phenotypically different circulating tumor cells sub-populations in patients with recurrent/refractory small cell lung cancer treated with pazopanib.

The aim of the study was to investigate the effect of 2nd-line pazopanib on the different CTCs subpopulations in SCLC patients and evaluate the clinical relevance of their changes. Different CTCs subpopulations were evaluated before pazopanib initiation (n = 56 patients), after one-cycle (n = 35) and on disease progression (n = 45) by CellSearch and double immunofluorescence using anti-CKs and anti-Ki67, anti-M30 or anti-Vimentin antibodies. Before treatment, CTCs were detected in 50% of patients by CellSearch whereas 53.4%, 15.5% and 74.1% patients had CK+/Ki67+, CK+/M30+ and CK+/Vim+ CTCs, respectively. One pazopanib cycle significantly decreased the number of CTCs as detected by CellSearch (p = 0.043) as well as the number of CK+/Ki67+ (p < 0.001), CK+/M30+ (p = 0.015) and CK+/Vim+ (p < 0.001) cells. On disease progression, both the incidence and CTC numbers were significantly increased (CellSearch, p = 0.027; CK+/Ki67+, p < 0.001; CK+/M30+, p = 0.001 and CK+/Vim+, p < 0.001). In multivariate analysis, the detection of CK+/Vim+ CTCs after one treatment cycle (HR: 7.9, 95% CI: 2.9-21.8; p < 0.001) and CTCs number on disease progression, as assessed by CellSearch, (HR: 2.0, 95% CI: 1.0-6.0; p = 0.005) were emerged as independent factors associated with decreased OS. In conclusion, pazopanib can eliminate different CTC subpopulations in patients with relapsed SCLC. The analysis of CTCs could be used as a dynamic biomarker of treatment efficacy.

TTF-1- and/or CD56-positive Circulating Tumor Cells in patients with small cell lung cancer (SCLC).

The aim of the study was to evaluate the phenotypic CTCs heterogeneity (TTF-1+ and/or CD56+) in SCLC patients and correlate it with the CellSearch. Peripheral blood was obtained from 108 consecutive patients. CTCs were detected by CellSearch and double-immunofluorescence using anti-CD45, anti-TTF-1 and anti-CD56 antibodies. Before chemotherapy TTF-1+/CD45-, CD56+/CD45- and TTF-1+/CD56+ CTCs were detected in 66(61.1%), 55(50.9%) and 46(42.6%) patients, respectively; 60.2% of patients were CellSearch+. Among the 22 patients with 0 CTCs/7.5 ml on CellSearch, TTF-1+/CD45-, CD56+/CD45- and TTF-1+/CD56+ CTCs were detected in 8(36.4%), 6(27.3) and 6(27.3%) patients, respectively; no CK+/EpCAM+ or TTF1+/EpCAM+ CTCs were detected in these patients. One-chemotherapy cycle decreased both the number of positive patients (p < 0.001) and their CTC number (p < 0.001), irrespectively of their phenotype and the detection method. The incidence and number of the different CTC subpopulations on PD, was significantly increased at their baseline levels. Multivariate analysis revealed that the increased number of CTCs at baseline and on PD were significantly associated with decreased PFS (p = 0.048) and OS (p = 0.041), respectively. There is an important CTC heterogeneity in such patients according to the expression of TTF-1 and CD56 which could detect EpCAM- CTC subpopulations and, thus, undetectable by CellSearch. These CTC subpopulations are dynamically correlated with treatment efficacy and disease-progression.