The relevance of RT-PCR detection of disseminated tumour cells is hampered by the expression of markers regarded as tumour-specific in activated lymphocytes

Combination of circulating tumor cells and 18F-FDG PET/CT for precision diagnosis in patients with non-small cell lung cancer

PURPOSE

To investigate the value of 2-deoxy-18f-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) and circulating tumor cells (CTCs) for the differential diagnosis of patients with benign lung diseases and those with NSCLC. To explore the phenotypic heterogeneity of CTCs and their correlation with FDG uptake in patients with Stage I-IV NSCLC.

METHODS

Blood specimens from patients with benign lung diseases and patients with primary NSCLC were collected for the detection of CTCs and their subtypes (epithelial, mixed, and mesenchymal) and analyzed for 18F-FDG PET/CT tumor metabolic parameters, including the maximum standardized uptake value (SUVmax), standard uptake value (SUL), metabolic tumor volume of primary lesion (MTV), total lesion glycolysis of primary lesion (TLG). Clinical data including age, gender, smoking history, tumor size, TNM stage and pathology type were also collected. The value of the two method alone and in combination for the differential diagnosis of benign and malignant was comparatively analyzed. Finally, the differences in CTC and its subtypes in different stages of NSCLC were compared, and FDG metabolic parameters were correlated with CTC subtypes.

RESULTS

There were a total of 65 patients with pulmonary diseases, including 12 patients with benign pulmonary diseases and 53 patients with NSCLC. The mean age was 67 ± 10 (38-89 years), 27 were females and 38 were males. 31 (22 males and 9 females) had a long history of smoking. The mean size of the largest diameter of all single lesions was 36 ± 22 mm with a range of 10-108 mm. Seven out of 12 benign diseases were inflammatory granulomatous lesions and 5 were inflammatory pseudotumours. Twenty-four out of 53 NSCLC were adenocarcinomas and 29 were squamous carcinomas. Twelve out of 53 patients with NSCLC were in Stage I, 10 were in Stage II, 17 were in Stage III and 14 were in Stage IV. SUVmax, SUL, MTV, TLG, total CTCs, epithelial CTCs, and mixed CTCs were all valuable in the differential diagnosis of benign and malignant. TLG combined with mixed CTCs was statistically different from all other diagnostic methods (p < 0.05) and higher than any other diagnostic criteria. In the differential diagnosis of benign and Stage I NSCLC, only total CTC (Z = -2.188 p = 0.039) and mixed CTCs (Z = -3.020 p = 0.014) had certain diagnostic efficacy, and there was no statistical difference between them (p = 0.480). Only mesenchymal CTCs differed in Stage I-IV NSCLC, with a higher number of those who developed distant metastases than those who had non-distant metastases. Epithelial CTCs correlated with SUVmax (r = 0.333, p = 0.015) and SUL (r = 0.374, p = 0.006). Mmesenchymal CTCs correlated with MTV (r = 0.342, p = 0.018) and TLG (r = 0.319, p = 0.02). Further subgroup analyses revealed epithelial CTCs were correlated with SUVmax (r = 0.543, p = 0.009) and SUL (r = 0.552, p = 0.008), and the total CTCs was correlated with SUVmax (r = 0.622, p = 0.003), SUL (r = 0.652, p = 0.003), MTV (r = 0.460, p = 0.031), and TLG (r = 0.472, p = 0.027) in the early group (Stage I-II). Only mesenchymal CTCs was associated with MTV (r = 0.369, p = 0.041), and TLG (r = 0.415, p = 0.02) in the intermediate-late group (Stage III-IV).

CONCLUSION

Both FDG PET metabolic parameters and CTCs demonstrated diagnostic value for NSCLC, and combining TLG with mixed CTCs could enhance their diagnostic efficacy. The total CTCs and mixed CTCs showed greater diagnostic value than FDG PET in distinguishing benign lesions from Stage I NSCLC. In NSCLC patients, the epithelial CTCs exhibited a positive correlation with SUVmax and SUL, while mesenchymal CTCs correlated with MTV, and TLG. Besides, epithelial CTCs showed stronger correlations with SUVmax and SUL, and total CTCs showed stronger correlations with SUVmax, SUL, MTV, and TLG in Stage I-II NSCLC. Only mesenchymal CTCs in Stage III-IV NSCLC showed correlations with MTV and TLG. Stage IV NSCLC cases displayed a higher number of mesenchymal CTCs.

Cell-Main Spectra Profile Screening Technique in Simulation of Circulating Tumour Cells Using MALDI-TOF Mass Spectrometry

Simple Summary

Cancer cells can detach from a primary tumour and present in peripheral blood as circulating tumour cells, or in the widest sense, as circulating atypical cells (CAC). Although CAC are a promising biomarker for non-invasive cancer screening, they occur at very low frequency and their detection and characterization remains challenging. We here validated isolation and concentration of untouched CAC from spiked cancer cell blood samples and combined this with matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). This workflow was optimised to detect as little as six cancer cells per 5000 white blood cells. Future development of our workflow may cover a larger range of cancer types and further improvements to enable the use of MALDI-TOF MS as a cancer-screening platform in clinical settings.

Abstract

Circulating atypical cells (CAC) are released from a primary tumour site into peripheral blood and are indicators of cancer metastasis. CAC occur at very low frequency in circulating blood, and their detection remains challenging. Moreover, white blood cells (WBC) are the major contaminant in enriched CAC samples. Here, we developed matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) as a novel CAC characterization platform. Main spectra profiles (MSP) of normal and cancer cells were generated by MALDI-TOF MS, and a cell-main spectra database was then compiled and analysed using the MALDI Biotyper software. Logarithmic scores accurately predicted distinct cell types. The feasibility of this workflow was then validated using simulated samples, which were prepared by 5000 WBC of three healthy individuals spiked with varying numbers (3, 6, 12, 25, 50, and 100) of lung, colon, or prostate cancer cells. MALDI-TOF MS was able to detect cancer cells down to six cells over the background noise of 5000 WBC with significantly higher predictive scores as compared to WBC alone. Further development of cell-MSP database to cover all cancer types sourced from cell lines and patient tumours may enable the use of MALDI-TOF MS as a cancer-screening platform in clinical settings in the future.

Sensitive and easy screening for circulating tumor cells by flow cytometry

Circulating Tumor Cells (CTCs) represent an easy, repeatable and representative access to information regarding solid tumors. However, their detection remains difficult because of their paucity, their short half-life, and the lack of reliable surface biomarkers. Flow cytometry (FC) is a fast, sensitive and affordable technique, ideal for rare cells detection. Adapted to CTCs detection (i.e. extremely rare cells), most FC-based techniques require a time-consuming pre-enrichment step, followed by a 2-hours staining procedure, impeding on the efficiency of CTCs detection. We overcame these caveats and reduced the procedure to less than one hour, with minimal manipulation. First, cells were simultaneously fixed, permeabilized, then stained. Second, using low-speed FC acquisition conditions and two discriminators (cell size and pan-cytokeratin expression), we suppressed the pre-enrichment step. Applied to blood from donors with or without known malignant diseases, this protocol ensures a high recovery of the cells of interest independently of their epithelial-mesenchymal plasticity and can predict which samples are derived from cancer donors. This proof-of-concept study lays the bases of a sensitive tool to detect CTCs from a small amount of blood upstream of in-depth analyses.

Current approaches for avoiding the limitations of circulating tumor cells detection methods-implications for diagnosis and treatment of patients with solid tumors

Eight million people die of cancer each year and 90% of deaths are caused by systemic disease. Circulating tumor cells (CTCs) contribute to the formation of metastases and thus are the subject of extensive research and an abiding interest to biotechnology and pharmaceutical companies. Recent technological advances have resulted in greatly improved CTC detection, enumeration, expansion, and culture methods. However, despite the fact that nearly 150 years have passed since the first detection and description of CTCs in human blood and enormous technological progress that has taken place in this field, especially within the last decade, few CTC detection methods have been approved for routine clinical use. This reflects the substantial methodological problems related to the nature of these cells, their heterogeneity, and diverse metastatic potential. Here, we provide an overview of CTC phenotypes, including the plasticity of CTCs and the relevance of inflammation and cell fusion phenomena for CTC biology. We also review the literature on CTC detection methodology-its recent improvements, clinical significance, and efforts of its clinical application in cancer patients management. At present, CTC detection remains a challenging diagnostic approach as a result of numerous current methodological limitations. This is especially problematic during the early stages of the disease due to the small numbers of CTCs released into the blood of cancer patients. Nonetheless, the rapid development of novel techniques of CTC detection and enumeration in peripheral blood is expected to expedite their implementation in the clinical setting. It is of utmost importance to understand the biology of CTCs and their distinct populations as a prerequisite for achieving this ultimate goal.

Prognostic role of circulating tumor cells in patients with pancreatic cancer: a meta-analysis

BACKGROUND

Isolation and characterization of circulating tumor cells (CTCs) in patients suffering from a variety of different cancers have become hot biomarker topics. In this study, we evaluated the prognostic value of CTCs in pancreatic cancer.

MATERIALS AND METHODS

Initial literature was identified using Medline and EMBASE. The primary data were hazard ratios (HRs) with 95% confidence intervals (CIs) of survival outcomes, including overall survival (OS) and progression free survival/recurrence free survival (PFS/RFS).

RESULTS

A total of 9 eligible studies were included in this meta-analysis, published between 2002 and 2013. The estimated pooled HR and 95%CI for OS for all studies was 1.64 (95%CI 1.39-1.94, p<0.00001) and the pooled HR and 95%CI for RFS/DFS was 2.36 (95%CI 1.41-3.96, p<0.00001). The HRs and 95%CIs for OS and RFS/ DFS in patients before treatment were 1.93 (95%CI 1.26-2.96, p=0.003) and 1.82 (95%CI 1.22-2.72, p=0.003), respectively. In patients receiving treatment, the HRs and 95%CI for OS and RFS/DFS were 1.37 (95%CI 1.00- 1.86, p=0.05) and 1.89 (95%CI 1.01-3.51, p=0.05), respectively. Moreover, the pooled HR and 95%CI for OS in the post-treatment group was 2.20 (95%CI 0.80-6.02, p=0.13) and the pooled HR for RFS/DFS was 8.36 (95%CI 3.22-21.67, p<0.0001).

CONCLUSIONS

The meta-analysis provided strong evidence supporting the proposition that CTCs detected in peripheral blood have a fine predictive role in pancreatic patients especially on the time point of post-treatment.

Diagnostic significance of alternative splice variants of REST and DOPEY1 in the peripheral blood of patients with breast cancer

Changes in alternative splicing have been linked to cancer development. We hypothesized that changes occurring in tumor tissue can also be detected in the peripheral blood of cancer patients leading to discovery of blood biomarkers of breast cancer. Alternative splicing profiles of 94 genes were examined in cancerous breast tissue. Discriminating splice variants were analyzed in the peripheral blood of early stage (BCI/II) (stage I-II; n = 26), neoadjuvant receiving locally advanced breast cancer patients (LABC) (stage IIb-IIIa, b; n = 10) and healthy volunteers (n = 26) using qRT-PCR analysis. Changes in marker expression during neoadjuvant therapy were analyzed at 15 timepoints. High expression of REST-N50, the alternatively spliced variant of REST, was detected in the blood of LABC patients but not in BCI/II and healthy controls (p = 0.0032 and p = 0.0029, respectively). Expression levels of DOPEY1v2, the alternative splice variant of DOPEY1, in the blood could differentiate cancer from healthy controls (p = 0.024) and discriminate between patient groups (BCI/II vs LABC, p = 0.002). Positive response to neoadjuvant therapy of REST-N50-positive LABC patients correlated with a decrease in REST-N50 levels (p < 0.0001). Assessment of REST-N50 and DOPEY1v2 may prove useful in diagnostic blood tests of breast cancer. REST-N50 shows a high potential as a blood biomarker for evaluating the effectiveness of therapy in the neoadjuvant setting.

Evaluation of prognostic significance of circulating tumor cells detection in rectal cancer patients treated with preoperative radiotherapy: prospectively collected material data

The aim of this study was to evaluate the prognostic value of circulating tumor cells (CTC) in nonmetastatic rectal cancer patients treated with short-term preoperative radiotherapy. In this single-center trial, 162 patients with rectal cancer after preoperative short-term radiotherapy (5 × 5 Gy) were recruited from January, 2008 to September, 2011. Clearance of CTC was determined in 91 patients enrolled in the molecular analysis. CTC presence was evaluated with real-time reverse transcription polymerase chain reaction assay (qPCR) based on the expression of three tumor genetic markers: carcinoembryonic antigen (CEA), cytokeratin 20 (CK20), and/or cancer stem cells marker CD133 (CEA/CK20/CD133). We found that CTC detection 7 days after surgery was of prognostic significance for the local recurrence (P value = 0.006). CTC detected preoperatively and 24 hours after resection had no prognostic value in cancer recurrence; however, there was a significant relationship between CTC prevalence 24 hours after surgery and lymph node metastasis (pN1-2). We also confirmed a significant clearance of CTC in peripheral blood (PB) 24 hours after surgery. Preoperative sampling is not significant for prognosis in rectal cancer patients treated with short-term radiotherapy. Detection of CTC in PB 7 days after surgery is an independent factor predicting local recurrence in this group of patients.

Filter characteristics influencing circulating tumor cell enrichment from whole blood

A variety of filters assays have been described to enrich circulating tumor cells (CTC) based on differences in physical characteristics of blood cells and CTC. In this study we evaluate different filter types to derive the properties of the ideal filter for CTC enrichment. Between 0.1 and 10 mL of whole blood spiked with cells from tumor cell lines were passed through silicon nitride microsieves, polymer track-etched filters and metal TEM grids with various pore sizes. The recovery and size of 9 different culture cell lines was determined and compared to the size of EpCAM+CK+CD45−DNA+ CTC from patients with metastatic breast, colorectal and prostate cancer. The 8 µm track-etched filter and the 5 µm microsieve had the best performance on MDA-231, PC3-9 and SKBR-3 cells, enriching >80% of cells from whole blood. TEM grids had poor recovery of ∼25%. Median diameter of cell lines ranged from 10.9–19.0 µm, compared to 13.1, 10.7, and 11.0 µm for breast, prostate and colorectal CTC, respectively. The 11.4 µm COLO-320 cell line had the lowest recovery of 17%. The ideal filter for CTC enrichment is constructed of a stiff, flat material, is inert to blood cells, has at least 100,000 regularly spaced 5 µm pores for 1 ml of blood with a ≤10% porosity. While cell size is an important factor in determining recovery, other factors must be involved as well. To evaluate a filtration procedure, cell lines with a median size of 11–13 µm should be used to challenge the system.

Increased Th1 immune response in SERPINB3 transgenic mice during acute liver failure

Acute liver failure (ALF) is characterized by severe neurological complications, known as acute hepatic encephalopathy, where brain ammonia and inflammatory processes play a dominant role. In experimental models of acute liver failure SERPINB3 was found significantly increased in microglia, the intrinsic immune cells of the central nervous system. The aim of the present study was to investigate the extent of brain tissue damage and the inflammatory milieu in experimental acute liver failure using a SERPINB3-transgenic mouse model. C57BL/6J wild-type and transgenic mice were inoculated with acetaminophen or phosphate-buffered saline and sacrificed 20 h postinjection. Proliferation and apoptotic activity were analyzed in brain tissue by immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling technique. The expression of cytokines was analysed in brain and liver tissue by real time polymerase chain reaction and in the corresponding serum samples using a Bio-Plex system. Acetaminophen induced a significantly lower body temperature and shorter survival in transgenic than in wild-type mice, despite liver function was similar in both groups. The brain of transgenic mice, expressing SERPINB3 positivity in microglia, showed increased glial cell number, associated to significant lower apoptotic death events, compared with wild-type mice. In mice injected with acetaminophen, remarkably higher values of cytokines mRNA were observed in the liver of both groups, with a trend toward higher values in transgenic animals. In brain tissue similar increase of tumor necrosis factor-αwas detected in transgenic and wild-type mice, while IL-10 mRNA increased only in the wild-type group. A remarkable increase of circulating Th1 cytokines was detected in serum of transgenic mice, while in the wild-type group they remained rather unchanged. These figures were associated with lower levels of granulocyte macropage colony-stimulating factor, despite similar increase of IL-10 values in both groups. In conclusion, in acute liver failure SERPINB3 determines an enhanced inflammatory background, mainly mediated by higher levels of Th1 proinflammatory cytokines.

Identification of suitable reference genes for gene expression measurement in uterine sarcoma and carcinosarcoma tumors

OBJECTIVE

To date no suitable reference genes have been identified in carcinosarcomas and non-epithelial malignant tumors of corpus uteri for normalizing real-time RT-PCR (qRT-PCR) assays. The purpose of this study was to select appropriate references for gene expression studies in these tumors.

MATERIALS AND METHODS

We used RNA extracts from 75 tissue samples, representing 50 tumors and 25 fragments of normal uterine tissues obtained from 50 patients treated for mixed tumors, smooth muscle sarcoma and stromal sarcoma of the uterus. qRT-PCR for five potential reference (housekeeping) genes, namely B2M, HMBS, HPRT1, TBP and UBC, was performed. The expression stability of these genes was assayed using geNorm software application.

RESULTS

The analysis of gene expression data with geNorm identified HPRT1 as the most stable reference gene, followed by UBC and HMBS, for all the investigated tissues. When stratified by disease, the results still pointed at HPRT1 as the gene that retained the greatest robustness in mixed tumors as well as in smooth muscle and stromal sarcomas.

CONCLUSIONS

Our work is the first report on reference gene selection for qRT-PCR applications in mixed tumors, smooth muscle sarcoma and stromal sarcoma of the uterus. A ranking of candidate genes' stability values for the three types of tumors is provided and might serve as a valuable guide for future gene expression studies of these rare entities.

Organ-specific markers in circulating tumor cell screening: an early indicator of metastasis-capable malignancy

Circulating tumor cells (CTCs) represent an important biological link in the spread of primary solid tumors to the metastatic disease responsible for most cancer mortality. Their detection in the peripheral blood of patients with many different carcinomas has shown that tumor-cell dissemination can proceed at an early stage of tumor development and their presence is associated with poor clinical outcomes, particularly in metastatic disease. In this article we describe how the increasingly sensitive isolation and detailed molecular characterization of CTCs has greatly improved our understanding of metastatic proliferation. We focus on how CTC detection and knowledge of the molecular architecture of these cells can serve as biomarkers to signal metastasis-capable disseminating cells and predict therapy-specific response. This has marked clinical utility for improved selection of systemic therapies to the individual needs of a cancer patient, real-time monitoring of metastatic disease treatments and the development of new targeted therapies.

Circulating cancer cells

Circulating tumour cells (CTCs) can be detected in the blood of many patients with different types of early or advanced cancer using antibody-based assays or molecular methods. In many studies the detection and quantification of CTCs has been linked to unfavourable prognosis. CTC detection offers the opportunity for individualized risk assessment beyond that determined by TNM staging. However, discordant results have been reported when different methodologies for CTC detection were used. Therefore, well-standardized detection methods cross-validated between different laboratories are still needed. CTCs are a heterogeneous population of cells with biological characteristics often different from those of their respective primary tumour cells. Pilot studies have shown that phenotyping of CTCs could be used to predict response to targeted therapies. In the era of biological therapeutics, CTC characterization at different time points during the course of disease may provide useful predictive information for the selection of the most appropriate treatment. Therefore, in the future, CTC detection and characterization might become a valuable tool to refine prognosis and serve as a real-time tumour biopsy for individually tailored cancer therapy. Prospective randomized studies are warranted to evaluate the utility of assessing and monitoring CTCs and modifying accordingly treatment strategies in order to improve the clinical outcome of cancer patients.

Detection of the circulating tumor cells in cancer patients

As the presence of tumor cells circulating in the blood is associated with systemic disease and shortened survival, the establishment of a method to detect circulating tumor cells (CTCs) is of critical importance for a more concise staging and follow-up of cancer patients. Recently, the most robust strategies for the determination of CTCs are the PCR-based methods and the CellSearch® system that exploits the immunofluorescent characterization and isolation of cancer cells. Herein, we analyzed the experimental strategies used for determining CTCs with respect to accuracy, sensitivity and reproducibility in cancers of the breast, colon, prostate and melanoma.

Squamous cell carcinoma antigen 1 and 2 expression in cultured normal peripheral blood mononuclear cells and in vulvar squamous cell carcinoma

Squamous cell carcinoma antigen (SCCA) is expressed in normal squamous cell epithelia and in squamous cell carcinomas (SCC). Two nearly identical genes encode the inhibitory serpins SCCA1 (SERPINB3) and SCCA2 (SERPINB4). Serum levels of SCCA are elevated in patients with benign skin diseases and in patients with SCC. SCCA, used for the monitoring of SCC patients, presents no satisfactory diagnostic specificity. As we have shown previously, the reverse transcription polymerase chain reaction (RT-PCR)-based SCCA messenger RNA (mRNA) testing aimed at detecting disseminated cancer cells may be hampered by the false-positive results due to SCCA expression in activated peripheral blood mononuclear cells (PBMC). The aim of this study was to assess the expression of SCCA at mRNA and protein levels in cultured normal PBMC, compared to that in vulvar SCC (VSCC) samples. High SCCA concentrations were found in vulvar tumours and in metastatic lymph nodes, while negative inguinal lymph nodes from the same patients often presented significantly less SCCA. In normal activated PBMC, the level of SCCA protein was the lowest. At the mRNA level SCCA was detectable in normal PBMC even in cultures with no mitogen stimulation, but only by the nested RT-PCR, contrary to VSCC samples found to be SCCA positive already in one-step PCR. Both SCCA1 and SCCA2 transcripts were present in cultured PBMC; SCCA1 was expressed at a higher level than SCCA2. In conclusion, both SCCA forms are detectable in normal PBMC cultured in vitro. SCCA expression level in normal PBMC is much lower than in the squamous epithelium-derived cells. In VSCC, in addition to tumour itself, metastatic lymph nodes seem also to be a potential source of serum SCCA.

Implications of cancer-associated systemic inflammation for biomarker studies

Highly sensitive molecular technologies provide new capacities for cancer biomarker research, but with sensitivity improvements marker specificity is significantly decreased, and too many false-positive results should disqualify the measurement from clinical use. Hence, of the thousands of potential cancer biomarkers only a few have found their way to clinical application. Differentiating false-positive results from true-positive (cancer-specific) results can indeed be difficult, if validation of a marker is performed against inadequate controls. We present examples of accumulating evidence that not only local but also systemic inflammatory reactions are implicated in cancer development and progression and interfere with the molecular image of cancer disease. We analyze several modern strategies of tumor marker discovery, namely, proteomics, metabonomics, studies on circulating tumor cells and circulating free nucleic acids, or their methylation degree, and provide examples of scarce, methodologically correct biomarker studies as opposed to numerous methodologically flawed biomarker studies, that examine cancer patients' samples against those of healthy, inflammation-free persons and present many inflammation-related biomarker alterations in cancer patients as cancer-specific. Inflammation as a cancer-associated condition should always be considered in cancer biomarker studies, and biomarkers should be validated against their expression in inflammatory conditions.

TTF-1 mRNA-positive circulating tumor cells in the peripheral blood predict poor prognosis in surgically resected non-small cell lung cancer patients

Circulating tumor cells (CTCs) have been identified in peripheral blood of cancer patients, and reproducible detection of CTCs has demonstrated the potential as useful diagnostic and prognostic tools in several cancers. Present study aimed to determine the clinical relevance of CTCs in surgically resected non-small cell lung cancer (NSCLC) patients. CTC status in presurgery and postsurgery peripheral blood samples from 79 surgically resected NSCLC patients was investigated using thyroid transcription factor-1 (TTF-1) and cytokeratin19 (CK19) mRNA markers by nested real-time RT (reverse transcription)-PCR assay. Detection of TTF-1((+))CTCs was found to be specific to NSCLC patients. TTF-1((+))CTCs were detected in 36.1% (22/61) of patients before surgery and in 37.5% (18/48) after surgery. For CK19 mRNA-expressing CTCs (CK19((+))CTCs), the detection rate was 42.6% (26/61) before surgery, and 25.0% (12/48) after surgery. Cases with postsurgery TTF-1((+)) and/or CK19((+))TCs was more associated with disease progression (P=0.004) and shorter disease progression-free survival (P=0.006) as compared to those without postsurgery CTCs. As an individual marker, postsurgery TTF-1((+))CTCs-positive status was more associated with disease progression (P=0.004) and shorter disease progression-free survival (P=0.004) as compared to postsurgery TTF-1((+))CTCs-negative status. Particularly, patients with postsurgery TTF-1((+))CTCs, but not presurgery (Pre((-))Post((+)) cases) showed marked shorter disease progression-free survival than other patients (P<0.001). On the other hand, a CK19((+))CTC status individually did not show significant clinical relevance, and presurgery CK19((+))CTC status did not either. Present study suggests that TTF-1 mRNA-expressing CTCs might be a useful surrogate predictor of disease progression before clinical manifestations are apparent, and that monitoring of TTF-1((+))CTCs status after surgery may be useful for identifying high-risk patients among surgically resected NSCLC cases.

Advances in research on circulating tumor cells

Circulating tumor cells (CTCs) are defined as cells that have detached, spontaneously or as a result of clinical operations, from a primary tumor or its metastatic lesions and circulate in the peripheral blood. They are considered as the primary reason for postoperative recurrence and distant metastasis of malignant tumors. In recent years, non-invasive detection of circulating tumor cells has become a new type of diagnostic tool to evaluate postoperative recurrence, distant metastasis, and prognosis. This article reviews recent advances in research on circulating tumor cells.

Cytokeratin 19-positive circulating tumor cells in early breast cancer prognosis

In spite of the heterogeneity of breast cancer at the molecular level, circulating tumor cells (CTCs) may provide a novel prognostic marker. Approximately 20–40% of early breast cancer patients have detectable CTCs using reverse transcription PCR for CK19. The detection of CTCs before adjuvant chemotherapy or during tamoxifen administration has been demonstrated to be an independent adverse prognostic factor in women with early-stage breast cancer. The prognostic value of CTC detection is of great significance in subgroups of patients with estrogen receptor-negative and human EGF receptor 2-positive tumors. Prospective clinical trials are warranted in order to validate the use of CTCs as predictive and/or prognostic markers and assess their utility in individualizing therapy of patients with early breast cancer.

SCG3 transcript in peripheral blood is a prognostic biomarker for REST-deficient small cell lung cancer

PURPOSE

Specific markers of circulating tumor cells may be informative in managing lung cancer. Because the RE-1 silencing transcription factor (REST/NRSF) is a transcriptional repressor that is inactivated in neuroendocrine lung cancer, we identified REST-regulated transcripts (CHGA, CHGB, SCG3, VGF, and PCSK1) for evaluation as biomarkers in peripheral blood.

EXPERIMENTAL DESIGN

Transcripts were screened across lung cancer and normal cell lines. Candidates were assessed by reverse transcription-PCR and hybridization of RNA extracted from the peripheral blood of 111 lung cancer patients obtained at clinical presentation and from 27 cancer-free individuals.

RESULTS

Expression profiling revealed multiple chromogranin transcripts were readily induced on REST depletion, most notably SCG3 was induced >500-fold. The SCG3 transcript was also overexpressed by 12,000-fold in neuroendocrine compared with nonneuroendocrine lung cancer cells. In peripheral blood of lung cancer patients and cancer-free individuals, we found that SCG3 was more tumor-specific and more sensitive than other chromogranin transcripts as a biomarker of circulating tumor cells. Overall, 36% of small cell lung cancer (SCLC) and 16% of non-SCLC patients scored positively for normalized SCG3 transcript. This correlated with worse survival among SCLC patients with limited disease (n = 33; P = 0.022) but not extensive disease (n = 29; P = 0.459). Interestingly, the subcohort of 6 SCLC patients with resistance to platinum/etoposide chemotherapy all scored positively for peripheral blood SCG3 transcript (P = 0.022).

CONCLUSIONS

SCG3 mRNA, a component of the REST-dependent neurosecretory transcriptional profile, provides a sensitive prognostic biomarker for noninvasive monitoring of neuroendocrine lung cancer.

Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer

The enumeration of circulating tumor cells has long been regarded as an attractive diagnostic tool, as circulating tumor cells are thought to reflect aggressiveness of the tumor and may assist in therapeutic decisions in patients with solid malignancies. However, implementation of this assay into clinical routine has been cumbersome, as a validated test was not available until recently. Circulating tumor cells are rare events which can be detected specifically only by using a combination of surface and intracellular markers, and only recently a number of technical advances have made their reliable detection possible. Most of these new techniques rely on a combination of an enrichment and a detection step. This review addresses the assays that have been described so far in the literature, including the enrichment and detection steps and the markers used in these assays. We have focused on breast cancer as most clinical studies on CTC detection so far have been done in these patients.

Micrometastatic disease in breast cancer: clinical implications

The presence of bone marrow disseminated tumour cells (DTCs) was shown to predict poor clinical outcome in early breast cancer. However, peripheral blood is easier to obtain and allows for serial monitoring of minimal residual disease. Towards this aim, circulating tumour cells (CTCs) in the blood are detected using either direct methods, mainly antibody-based assays (immunocytochemistry, immunofluorescence and flow cytometry), or indirect methods, mainly nucleic acid-based assays (detection of mRNA transcripts by reverse transcriptase polymerase chain reaction, RT-PCR). The detection of CTCs using RT-PCR for CK19 was shown to be an independent prognostic factor in women with early breast cancer. Furthermore, considerable progress has been accomplished in genotyping, phenotyping and profiling micrometastatic cells. The challenge now is to integrate minimal residual disease as a prognostic and predictive tool in the management of breast cancer. This requires the standardisation of micrometastatic cell detection and characterisation, which will allow the incorporation of CTCs/DTCs into prospective clinical trials testing their clinical utility.

Phosphorylated EGFR and PI3K/Akt signaling kinases are expressed in circulating tumor cells of breast cancer patients

Introduction

The phosphoinositide-3 kinase (PI3K)/Akt pathway, operating downstream of epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor (HER)2, is implicated in cell migration and survival. EGFR and HER2 are expressed in circulating tumor cells, but the activation status of downstream signaling molecules has not yet been reported.

Methods

To investigate expression levels of EGFR, HER2, PI3K, and Akt in circulating tumor cells, we used peripheral blood mononuclear cells from 32 cytokeratin-19 mRNA-positive patients with early (n = 16) and metastatic (n = 16) breast cancer.

Peripheral blood mononuclear cell cytospins were double stained with cytokeratin antibody along with one of the following: EGFR, phospho-EGFR, HER2, phospho-PI3K, or phospho-Akt antibodies.

Results

EGFR and HER2 were expressed in circulating tumor cells of 38% and 50% patients with early and 44% and 63% patients with metastatic disease, respectively. Interestingly, phospho-PI3K and phospho-Akt expression levels were similar at 88% (14 out of 16) and 81% (13 out of 16), respectively, in circulating tumor cells of patients with early and metastatic disease. Phospho-EGFR was observed in circulating tumor cells of two (33%) early and six (86%) metastatic EGFR-positive patients. Immunomagnetic separation of peripheral blood mononuclear cells, using EpCAM antibody, and subsequent double-staining experiments of circulating tumor cells showed that EGFR was co-expressed with HER2, phospho-Akt and phospho-PI3K kinases, indicating activation of the corresponding survival signaling pathway.

Conclusions

Our findings demonstrate that circulating tumor cells express receptors and activated signaling kinases of the EGFR/HER2/PI3K/Akt pathway, which could be used as targets for their effective elimination.

Detection of circulating tumour cells in peripheral blood with an automated scanning fluorescence microscope

We have developed an automated, highly sensitive and specific method for identifying and enumerating circulating tumour cells (CTCs) in the blood. Blood samples from 10 prostate, 25 colorectal and 4 ovarian cancer patients were analysed. Eleven healthy donors and seven men with elevated serum prostate-specific antigen (PSA) levels but no evidence of malignancy served as controls. Spiking experiments with cancer cell lines were performed to estimate recovery yield. Isolation was performed either by density gradient centrifugation or by filtration, and the CTCs were labelled with monoclonal antibodies against cytokeratins 7/8 and either AUA1 (against EpCam) or anti-PSA. The slides were analysed with the Ikoniscope® robotic fluorescence microscope imaging system. Spiking experiments showed that less than one epithelial cell per millilitre of blood could be detected, and that fluorescence in situ hybridisation (FISH) could identify chromosomal abnormalities in these cells. No positive cells were detected in the 11 healthy control samples. Circulating tumour cells were detected in 23 out of 25 colorectal, 10 out of 10 prostate and 4 out of 4 ovarian cancer patients. Five samples (three colorectal and two ovarian) were analysed by FISH for chromosomes 7 and 8 combined and all had significantly more than four dots per cell. We have demonstrated an Ikoniscope® based relatively simple and rapid procedure for the clear-cut identification of CTCs. The method has considerable promise for screening, early detection of recurrence and evaluation of treatment response for a wide variety of carcinomas.

Detection, clinical relevance and specific biological properties of disseminating tumour cells

Most cancer deaths are caused by haematogenous metastatic spread and subsequent growth of tumour cells at distant organs. Disseminating tumour cells present in the peripheral blood and bone marrow can now be detected and characterized at the single-cell level. These cells are highly relevant to the study of the biology of early metastatic spread and provide a diagnostic source in patients with overt metastases. Here we review the evidence that disseminating tumour cells have a variety of uses for understanding tumour biology and improving cancer treatment.

Circulating tumor cells in breast cancer

PURPOSE OF REVIEW

To critically review the latest findings concerning the detection and characterization of circulating tumor cells in breast cancer.

RECENT FINDINGS

Various studies have used different methods and markers for circulating tumor cell detection in breast cancer. Data on the prognostic value of circulating tumor cell monitoring by the CellSearch system are now available in patients with measurable metastatic breast cancer receiving chemotherapy, whereas no such data are still available for adjuvant or neoadjuvant settings. The detection of cytokeratin 19 mRNA-positive cells before the initiation of adjuvant chemotherapy was shown to be an independent prognostic factor for worse clinical outcome in patients with early breast cancer. Interestingly, this was mainly observed in patients with triple-negative and HER2-positive, but not estrogen receptor-positive/HER2-negative, early breast cancer. Finally, gene-expression profiling of single cells was reported to be feasible with important implications for eliminating circulating tumor cells. Pilot studies have shown that phenotyping of circulating tumor cells could be used to predict response to targeted therapies.

SUMMARY

Circulating tumor cells might become a valuable tool to refine prognosis in early and metastatic breast cancer. Circulating tumor cell phenotyping/profiling may serve as a real-time tumor biopsy for individually-tailored targeted therapies.

Current status in human breast cancer micrometastasis

PURPOSE OF REVIEW

Current research and clinical developments on hematogeneous micrometastasis in breast cancer patients are summarized.

RECENT FINDINGS

Distant metastasis is the leading cause of cancer-related death in breast cancer and bone marrow is a common homing organ for blood-borne disseminated tumor cells derived from primary breast carcinomas. Sensitive immunocytochemical or molecular assays now allow the detection of single disseminated tumor cells in bone marrow or the peripheral blood at a frequency of 10 and these cells are detected in 10-60% of breast cancer patients without clinical or even histopathologic signs of metastasis. Recently, evidence has emerged that the detection of disseminated tumor cells and circulating tumor cells may provide important prognostic information, and in particular might help to monitor efficacy of therapy. Moreover, the characterization of disseminated tumor cells/circulating tumor cells has shed new light on the complex process underlying early tumor cell dissemination and metastatic progression in cancer patients.

SUMMARY

Research on disseminated tumor cells/circulating tumor cells will help to identify novel targets for biological therapies aimed at preventing metastatic relapse and to monitor the efficacy of these therapies. In particular, understanding tumor dormancy and identifying metastatic stem cells might result in the development of new concepts for antimetastatic therapies.

Circulating tumor cells (CTC) detection: clinical impact and future directions

Recent molecular and clinical studies have shown that invasion may occur very early in tumor development, thus emphasizing the potential importance of specific and sensitive detection of circulating tumor cells (CTC) and circulating tumor microemboli (CTM). The technical challenge in this field consists of finding "rare" tumor cells (just a few CTCs mixed with the approximately 10 million leukocytes and 5 billion erythrocytes in 1ml of blood) and being able to distinguish them from epithelial non-tumor cells and leukocytes. Many recent studies have discussed the clinical impact of detecting CTC/CTM. Although conflicting results have been obtained, these studies suggest the vast potential of CTC/CTM detection in cancer prognosis and follow up. However, the variable technical approaches which were used, as well as the number of millilitres of blood analyzed, the quality of sensitivity and specificity tests, the number of patients versus controls and the data interpretation make it very difficult to draw firm conclusions. A particularly important recent finding is that invasive tumor cells tend to loose their epithelial antigens by the epithelial to mesenchymal transition (EMT) process. Furthermore, it is known that non-tumor epithelial cells can also be present in blood. Thus, it appears that a reliable diagnostic identification of CTC and CTM cannot be based on the expression of epithelial-specific transcripts or antigens. Cytopathological examination of CTC/CTM, sensitively enriched from blood, represents a potentially useful alternative and can now be employed in routine analyses as a specific diagnostic assay, and be tested in large, blind, multicenter clinical trials. This basic approach can be complemented by immunological and molecular studies for further characterization of CTC/CTM and of their malignant potential. This review is aimed at helping oncologists critically evaluate past and future research work in this field. The interest in development and assessment of this noninvasive marker should lead to more effective and better tailored anticancer treatments for individual patients, thus resulting in their improved life expectancy.