领域: | 细胞生物学 | ||
样品: | 非小细胞肺癌患者的细胞 | 项目: | 环肿瘤细胞分析 |
参考: | NSCLC |
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非小细胞肺癌患者的环肿瘤细胞分析 |
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Analysis
of Circulating Tumor Cells in Patients with Non-small Cell Lung Cancer
Using Epithelial Marker-Dependent and -Independent Approaches
Introduction:
Epithelial circulating tumor cells (CTCs) are detectable in patients
with non-small cell lung cancer (NSCLC). However,epithelial to
mesenchymal transition, a widely reported prerequisite for metastasis,
may lead to an underestimation of CTC number. We compared directly an
epithelial marker-dependent (CellSearch) and a marker-independent
(isolation by size of epithelial tumor cells [ISET]) technology platform
for the ability to identify CTCs. Molecular characteristics of CTCs
were also explored.
Methods: Paired peripheral
blood samples were collected from 40 chemona¨ive, stages IIIA to IV
NSCLC patients. CTCs were enumerated by Epithelial Cell Adhesion
Molecule-based immunomagnetic capture (CellSearch, Veridex) and by
filtration (ISET, RareCell Diagnostics). CTCs isolated by filtration
were assessed by immunohistochemistry for epithelial marker expression
(cytokeratins,Epithelial Cell Adhesion Molecule, epidermal growth factor
receptor) and for proliferation status (Ki67).
Results: CTCs
were detected using ISET in 32 of 40 (80%) patients compared with 9 of
40 (23%) patients using CellSearch. A subpopulation of CTCs isolated by
ISET did not express epithelial markers.Circulating tumor microemboli
(CTM, clusters of 3 CTCs) were observed in 43% patients using ISET but
were undetectable by CellSearch. Up to 62% of single CTCs were positive
for the proliferation marker Ki67, whereas cells within CTM were
nonproliferative.
Conclusions: Both technology
platforms detected NSCLC CTCs.ISET detected higher numbers of CTCs
including epithelial marker negative tumor cells. ISET also isolated CTM
and permitted molecular characterization. Combined with our previous
CellSearch data confirming CTC number as an independent prognostic
biomarker for NSCLC, we propose that this complementary dual technology
approach to CTC analysis allows more complete exploration of CTCs in
patients with NSCLC.
The detection and characterization of
circulating tumor cells (CTCs) in cancer patients offer as yet untapped
potential to further understand the biology of human cancer metastasis
and to identify novel treatment strategies. Recent advances in
technology have paved the way to reproducible CTC detection and
enumeration and begun to reveal their potential as a real-time,
minimally invasive, “virtual biopsy”(reviewed in Hou et al.1). The
robust, semiautomated Cell-Search platform (Veridex, LLC, Raritan, NJ)
has been used to demonstrate prognostic significance of CTC numbers in
patients with metastatic breast, prostate, and colorectal cancers2–7
(reviewed by Krebs et al.8) and subsequently has been approved by the US
Food and Drug Administration as a prognostic biomarker and as an aid to
monitoring treatment response in these disease types. We recently
reported that CellSearch detection of 5 CTCs (per 7.5 ml of blood) in
patients with advanced non-small cell lung cancer (NSCLC) is a poor
prognostic factor and that a change in CTC number after a single cycle
of standard-of-care chemotherapy predicts survival outcome.9 However,
two-thirds of patients with stage IV NSCLC had no detectable CTCs, and
CTCs were detectable in less than 5% stage III patients using this
technology platform.
Detection of CTCs using CellSearch is
dependent on tumor cell expression of Epithelial Cell Adhesion
Molecule(EpCam), an epithelial cell marker. However, the paradigm of
epithelial to mesenchymal transition (EMT) as a predominant mechanism
for tumor cell invasion and metastasis raises the possibility that not
all cells in the circulation will express epithelial markers.10–14 Thus,
we hypothesized that the low prevalence of CTCs detected with the
CellSearch technology in patients with advanced NSCLC, although strongly
prognostic,may be due to the loss of EpCam expression. Therefore,we
explored an antigen/EpCAM-independent approach for the ability to
identify CTCs and for the potential to perform molecular
characterization.
FIGURE
1. Biological controls for immunohistochemistry of circulating tumor
cells (CTCs) isolated by ISET. (A)Positive-staining controls and (B)
negative-staining controls for each of the markers used in this study to
characterize CTCs/CTM. Control staining was performed on cell lines or
peripheral blood mononuclear cells (PBMCs),cytospun onto glass slides.
All images were acquired at 400 magnification using a Bioview imaging
system.ISET, isolation by size of epithelial tumor cells; CTM,
circulating tumor microemboli.
FIGURE
2. Exclusion of nontumor cell contaminants on ISET filters and
circulating tumor cell (CTC) enumeration strategy. A,CD45 immunostaining
of H460 tumor cells spiked into healthy donor blood and processed
through the ISET filtration system to exclude white blood cells. Filter
pores appear dark and circular or cylindrical (black arrows), white
blood cells stain brown due to DAB-substrate reaction (red arrow), and
tumor cells appear blue due to the hematoxylin counterstain (blue
arrow). B,Bar chart demonstrating the mean and SE for CTC number
depending on the number of spots analyzed. Four spots or more exhibited
the most representative mean CTC value. C, VE-cadherin (CD144) staining
on clinical samples processed by ISET to exclude mature circulating
endothelial cells (CECs). CECs exhibited small, round, or oval, pale
nuclei with low nuclear-to-cytoplasmic ratio and were positive for CD144
(blue arrows). Nuclei appear blue due to hematoxylin counterstain. A
cluster of CECs is shown in the central panel. Filter pores appear dark
and circular (black arrows). D, CD45 staining on clinical samples
processed by ISET. Cells with CEC morphology are seen with
hematoxylin-stained nuclei (blue arrows). These cells were considered to
be mature CECs on the basis on their morphological similarity with
CD144-positive cells (C) and absence of CD45 expression. E, Typical CD45
negative squamous skin cells exhibiting small, round, pyknotic nuclei
with abundant cytoplasm
(blue arrows). Filter pores appear dark and
circular (exemplified by black arrow). ISET, isolation by size of
epithelial tumor cells.