Cytokeratin-19 mRNA-positive circulating tumor cells during follow-up of patients with operable breast cancer: prognostic relevance for late relapse

New insights into the correlations between circulating tumor cells and target organ metastasis

Organ-specific metastasis is the primary cause of cancer patient death. The distant metastasis of tumor cells to specific organs depends on both the intrinsic characteristics of the tumor cells and extrinsic factors in their microenvironment. During an intermediate stage of metastasis, circulating tumor cells (CTCs) are released into the bloodstream from primary and metastatic tumors. CTCs harboring aggressive or metastatic features can extravasate to remote sites for continuous colonizing growth, leading to further lesions. In the past decade, numerous studies demonstrated that CTCs exhibited huge clinical value including predicting distant metastasis, assessing prognosis and monitoring treatment response et al. Furthermore, increasingly numerous experiments are dedicated to identifying the key molecules on or inside CTCs and exploring how they mediate CTC-related organ-specific metastasis. Based on the above molecules, more and more inhibitors are being developed to target CTCs and being utilized to completely clean CTCs, which should provide promising prospects to administer advanced tumor. Recently, the application of various nanomaterials and microfluidic technologies in CTCs enrichment technology has assisted to improve our deep insights into the phenotypic characteristics and biological functions of CTCs as a potential therapy target, which may pave the way for us to make practical clinical strategies. In the present review, we mainly focus on the role of CTCs being involved in targeted organ metastasis, especially the latest molecular mechanism research and clinical intervention strategies related to CTCs.

The Diversity of Liquid Biopsies and Their Potential in Breast Cancer Management

Analyzing blood as a so-called liquid biopsy in breast cancer (BC) patients has the potential to adapt therapy management. Circulating tumor cells (CTCs), extracellular vesicles (EVs), cell-free DNA (cfDNA) and other blood components mirror the tumoral heterogeneity and could support a range of clinical decisions. Multi-cancer early detection tests utilizing blood are advancing but are not part of any clinical routine yet. Liquid biopsy analysis in the course of neoadjuvant therapy has potential for therapy (de)escalation.Minimal residual disease detection via serial cfDNA analysis is currently on its way. The prognostic value of blood analytes in early and metastatic BC is undisputable, but the value of these prognostic biomarkers for clinical management is controversial. An interventional trial confirmed a significant outcome benefit when therapy was changed in case of newly emerging cfDNA mutations under treatment and thus showed the clinical utility of cfDNA analysis for therapy monitoring. The analysis of PIK3CA or ESR1 variants in plasma of metastatic BC patients to prescribe targeted therapy with alpesilib or elacestrant has already arrived in clinical practice with FDA-approved tests available and is recommended by ASCO. The translation of more liquid biopsy applications into clinical practice is still pending due to a lack of knowledge of the analytes' biology, lack of standards and difficulties in proving clinical utility.

Duplex Phenotype Detection and Targeting of Breast Cancer Cells Using Nanotube Nanoprobes and Raman Imaging

We designed, synthesized, and characterized a Raman nanoprobe made of dye-sensitized single-walled carbon nanotubes (SWCNTs) that can selectively target biomarkers of breast cancer cells. The nanoprobe is composed of Raman-active dyes encapsulated inside a SWCNT, whose surface is covalently grafted with poly(ethylene glycol) (PEG) at a density of ∼0.7% per carbon. Using α-sexithiophene- and β-carotene-derived nanoprobes covalently bound to an antibody, either anti-E-cadherin (E-cad) or anti-keratin-19 (KRT19), we prepared two distinct nanoprobes that specifically recognize biomarkers on breast cancer cells. Immunogold experiments and transmission electron microscopy (TEM) images are first used to guide the synthesis protocol for higher PEG-antibody attachment and biomolecule loading capacity. The duplex of nanoprobes was then applied to target E-cad and KRT19 biomarkers in T47D and MDA-MB-231 breast cancer cell lines. Hyperspectral imaging of specific Raman bands allows for simultaneous detection of this nanoprobe duplex on target cells without the need for additional filters or subsequent incubation steps. Our results confirm the high reproducibility of the nanoprobe design for duplex detection and highlight the potential of Raman imaging for advanced biomedical applications in oncology.

Comprehensive liquid biopsy analysis as a tool for the early detection of minimal residual disease in breast cancer

Liquid biopsy (LB) provides a unique minimally invasive tool to follow-up cancer patients over time, to detect minimal residual disease (MRD), to study metastasis-biology and mechanisms of therapy-resistance. Molecular characterization of CTCs offers additionally the potential to understand resistance to therapy and implement individualized targeted treatments which can be modified during the disease evolution and follow-up period of a patient. In this study, we present a long-term follow-up of operable breast cancer patients based on a comprehensive liquid biopsy analysis. We performed a comprehensive liquid biopsy analysis in peripheral blood of 13 patients with early-stage operable breast cancer at several time points for a period of ten years, consisting of: (a) CTC enumeration using the CellSearch system, (b) phenotypic analysis of CTCs using Immunofluorescence, (c) gene expression analysis, in EpCAM(+) CTCs for CK-19, CD24,CD44, ALDH1, and TWIST1, (d) analysis of PIK3CA and ESR1 mutations in EpCAM(+) CTCs and corresponding plasma ctDNA and (e) DNA methylation of ESR1 in CTCs. 10/13 (77%) patients were found negative for LB markers in PB during the whole follow-up period, and these patients did not relapse during the follow-up. However, 3/13(18%) patients that were positive for at least one LB marker relapsed within the follow-up period. The molecular characteristics of CTCs were highly different even for the same patient at different time points, and always increased before the clinical relapse. Our results indicate that liquid biopsy can reveal the presence of MRD at least 4 years before the appearance of clinically detectable metastatic disease demonstrating that a comprehensive liquid biopsy analysis provides highly important information for the therapeutic management of breast cancer patients.

Detection of circulating tumour cells before and following adjuvant chemotherapy and long-term prognosis of early breast cancer

Background

The detection of circulating tumour cells (CTC) is prognostic for disease recurrence in early breast cancer (BC). This study aims to investigate whether this prognostic effect persists or varies over time.

Methods

The study population consisted of prospectively included stage I–III BC patients. The presence of CK19 mRNA-positive CTC in the peripheral blood was evaluated before and after adjuvant chemotherapy, using a real-time RT–PCR assay. Longitudinal samples were collected for a subset of patients.

Results

Baseline CTC data were available from 1220 patients, while 1132 had both pre- and post-therapy data. After a median follow-up of 134.1 months, CTC positivity at baseline was associated with shorter overall survival (OS; HR_adj = 1.72, 95% CI 1.34–2.21, p < 0.001). For disease-free survival, an interaction with time (p = 0.045) was observed. CTC positivity predicted early (within 5 years; HR_adj = 1.76, 95_% CI 1.33–2.32, p < 0.001) but not late recurrence (HR_adj = 1.10, 95% CI 0.79–1.53, p = 0.577). Following adjuvant chemotherapy, more patients converted from CTC-positive to CTC-negative than vice versa (p < 0.001). Ten-year OS was 68.6% for + /+ and 86.7% for −/− group (p < 0.001). CTC status at follow-up predicted disease recurrence.

Conclusion

CTC detection pre- and post-adjuvant chemotherapy is prognostic for early relapse, supporting investigations for novel adjuvant therapeutic approaches.

Keratin 19 maintains E-cadherin localization at the cell surface and stabilizes cell-cell adhesion of MCF7 cells

A cytoskeletal protein keratin 19 (K19) is highly expressed in breast cancer but its effects on breast cancer cell mechanics are unclear. In MCF7 cells where K19 expression is ablated,we found that K19 is required to maintain rounded epithelial-like shape and tight cell-cell adhesion. A loss of K19 also lowered cell surface E-cadherin levels. Inhibiting internalization restored cell-cell adhesion of KRT19  knockout cells, suggesting that E-cadherin internalization contributed to defective adhesion. Ultimately, while K19 inhibited cell migration and invasion, it was required for cells to form colonies in suspension. Our results suggest that K19 stabilizes E-cadherin complexes at the cell membrane to maintain cell-cell adhesion which inhibits cell invasiveness but provides growth and survival advantages for circulating tumor cells.

Predicting amplification of MYCN using CpG methylation biomarkers in neuroblastoma

Background: Neuroblastoma is the most common extracranial solid tumor in childhood. Amplification of MYCN in neuroblastoma is a predictor of poor prognosis. Materials and methods: DNA methylation data from the TARGET data matrix were stratified into MYCN amplified and non-amplified groups. Differential methylation analysis, clustering, recursive feature elimination (RFE), machine learning (ML), Cox regression analysis and Kaplan-Meier estimates were performed. Results and Conclusion: 663 CpGs were differentially methylated between the two groups. A total of 25 CpGs were selected by RFE for clustering and ML, and a 100% clustering accuracy was obtained. ML validation on three external datasets produced high accuracy scores of 100%, 97% and 93%. Eight survival-associated CpGs were also identified. Therapeutic interventions may need to be targeted to patient subgroups.

Liquid Biopsy to Detect Minimal Residual Disease: Methodology and Impact

One reason why some patients experience recurrent disease after a curative-intent treatment might be the persistence of residual tumor cells, called minimal residual disease (MRD). MRD cannot be identified by standard radiological exams or clinical evaluation. Tumor-specific alterations found in the blood indirectly diagnose the presence of MRD. Liquid biopsies thus have the potential to detect MRD, allowing, among other things, the detection of circulating tumor DNA (ctDNA), circulating tumor cells (CTC), or tumor-specific microRNA. Although liquid biopsy is increasingly studied, several technical issues still limit its clinical applicability: low sensitivity, poor standardization or reproducibility, and lack of randomized trials demonstrating its clinical benefit. Being able to detect MRD could give clinicians a more comprehensive view of the risk of relapse of their patients and could select patients requiring treatment escalation with the goal of improving cancer survival. In this review, we are discussing the different methodologies used and investigated to detect MRD in solid cancers, their respective potentials and issues, and the clinical impacts that MRD detection will have on the management of cancer patients.

RNA-Based CTC Analysis Provides Prognostic Information in Metastatic Breast Cancer

In metastatic breast cancer (MBC) the molecular characterization of circulating tumor cells (CTCs) provides a unique tool to understand metastasis-biology and therapy-resistance. We evaluated the prognostic significance of gene expression in EpCAM⁽⁺⁾ CTCs in 46 MBC patients based on a long follow-up. We selected a panel consisting of stem cell markers (CD24, CD44, ALDH1), the mesenchymal marker TWIST1, receptors (ESR1, PGR, HER2, EGFR) and the epithelial marker CK-19. Singleplex RT-qPCR was used for TWIST1 and CK-19 and multiplex RT-qPCR for stem cell markers and receptors. A group of 19 healthy donors (HD) was used as control. Univariate (p = 0.001) and multivariate analysis (p = 0.002) revealed the prognostic value of combined gene expression of CK-19(+), CD44^high/CD24^low, ALDH1^high/CD24^low and HER2 over-expression for overall survival (OS). The Kaplan–Meier estimates of OS were significantly different in patients positive for CK-19 (p = 0.028), CD44^high/CD24^low (p = 0.002), ALDH1^high/CD24^low (p = 0.007) and HER2-positive (p = 0.022). Our results indicate that combined gene expression analysis in EpCAM⁽⁺⁾ CTCs provides prognostic information in MBC.

Clinical management and biology of tumor dormancy in breast cancer

Clinical tumor dormancy is specified as an extended latency period between removal of the primary tumor and subsequent relapse in a cancer patient who has been clinically disease-free. In particular, patients with estrogen receptor-positive breast cancer can undergo extended periods of more than five years before they relapse with overt metastatic disease. Recent studies have shown that minimal residual disease in breast cancer patients can be monitored by different liquid biopsy approaches like analysis of circulating tumor cells or cell-free tumor DNA. Even though the biological principles underlying tumor dormancy in breast cancer patients remain largely unknown, clinical observations and experimental studies have identified emerging mechanisms that control the state of tumor dormancy. In this review, we illustrate the latest discoveries on different molecular aspects that contribute to the control of tumor dormancy and distant metastatic relapse, then discuss current treatments affecting minimal residual disease and dormant cancer cells, and finally highlight how novel liquid biopsy based diagnostic methodologies can be integrated into the detection and molecular characterization of minimal residual disease.

Dynamic changes of CTCs in patients with metastatic HR(+)/HER2(-) breast cancer receiving salvage treatment with everolimus/exemestane

PURPOSE

Detection of CTCs represents a poor prognostic factor in patients with early and metastatic breast cancer (mBC) and treatment with everolimus-exemestane (E/E) is an established effective treatment in hormone receptor-positive/HER2-negative mBC patients. The effect of E/E on CTCs in mBC patients was prospectively investigated.

METHODS

CTCs from 50 pre-treated patients with mBC receiving E/E were analyzed using the CellSearch (CS) platform and triple immunofluorescence (IF) staining for cytokeratin, M30 and Ki67 expression to assess their proliferative and apoptotic status.

RESULTS

CTCs (by CS) were detected in 64% of patients before treatment and E/E administration resulted in their decreased prevalence [(n = 18; 36%, p = 0.004) and (n = 7; 19.4%, p = 0.019) post-1st and post-3rd treatment cycle, respectively] whereas it was significantly increased at disease progression (PD: 61%) compared to post-1st and post-3rd cycle (p = 0.049 and p = 0.021, respectively). Ki67-positive CTCs were detected in 60%, 60%, 17% and 50% of patients before treatment, post-1st, post-3rd cycle and at PD, respectively, while the opposite was observed for M30-positive CTCs (0% at baseline, 10% after the 1st cycle, 50% after the 3rd cycle and 0% at PD). The detection of even ≥ 1 CTC/5 ml after one cycle was associated with decreased PFS (3.3 vs 9.0 months, p = 0.025) whereas the detection of even ≥ 2 CTCs at PD was associated with decreased OS (32.4 vs 19.5 months; p = 0.009).

CONCLUSIONS

The combination of E/E resulted in early elimination of proliferating CTCs in mBC patients and this effect was associated with a favorable clinical outcome.

Longitudinal Multi-Parametric Liquid Biopsy Approach Identifies Unique Features of Circulating Tumor Cell, Extracellular Vesicle, and Cell-Free DNA Characterization for Disease Monitoring in Metastatic Breast Cancer Patients

Dynamics of mRNA from circulating tumor cells (CTCs), mRNA from extracellular vesicles (EVs), and cell-free DNA (cfDNA) were assessed to examine the relevance of a longitudinal multi-parametric liquid biopsy strategy. Eighteen milliliters of blood was drawn from 27 hormone receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC) patients at disease progression and at two subsequent radiologic staging time points. CTC mRNA and EV mRNA were analyzed using multi-marker qPCR, and cfDNA was analyzed using targeted next-generation sequencing (NGS). The presence of ERBB2 or ERBB3 overexpression signals in CTCs significantly correlated with disease progression (87% specificity, 36% sensitivity, p-value = 0.023), and the presence of either ERBB3 signals in CTCs or EVs or cfDNA variants in ERBB3 also showed a significant association with progressive MBC. Fluctuations during treatment were detected in the EV fraction with the appearance of hitherto undetected ERCC1 signals correlating with progressive disease (97% specificity, 18% sensitivity, p-value = 0.030). Allele frequency development of ESR1 and PIK3CA variants detected at subsequent staging time points could be used as a predictor for therapy success and, importantly, might help guide therapy decisions. The three analytes, each with their own unique features for disease monitoring, were shown to be complementary, underlining the usefulness of the longitudinal multi-parametric liquid biopsy approach.

Targeting the cytoskeleton against metastatic dissemination

Cancer is a pathology characterized by a loss or a perturbation of a number of typical features of normal cell behaviour. Indeed, the acquisition of an inappropriate migratory and invasive phenotype has been reported to be one of the hallmarks of cancer. The cytoskeleton is a complex dynamic network of highly ordered interlinking filaments playing a key role in the control of fundamental cellular processes, like cell shape maintenance, motility, division and intracellular transport. Moreover, deregulation of this complex machinery contributes to cancer progression and malignancy, enabling cells to acquire an invasive and metastatic phenotype. Metastasis accounts for 90% of death from patients affected by solid tumours, while an efficient prevention and suppression of metastatic disease still remains elusive. This results in the lack of effective therapeutic options currently available for patients with advanced disease. In this context, the cytoskeleton with its regulatory and structural proteins emerges as a novel and highly effective target to be exploited for a substantial therapeutic effort toward the development of specific anti-metastatic drugs. Here we provide an overview of the role of cytoskeleton components and interacting proteins in cancer metastasis with a special focus on small molecule compounds interfering with the actin cytoskeleton organization and function. The emerging involvement of microtubules and intermediate filaments in cancer metastasis is also reviewed.

The Signaling Duo CXCL12 and CXCR4: Chemokine Fuel for Breast Cancer Tumorigenesis

Simple Summary

Breast cancer remains the most common malignancy in women. In this review, we explore the role of the CXCL12/CXCR4 pathway in breast cancer. We show that the CXCL12/CXCR4 cascade is involved in nearly every aspect of breast cancer tumorigenesis including proliferation, cell motility and distant metastasis. Moreover, we summarize current knowledge about the CXCL12/CXCR4-targeted therapies. Due to the critical roles of this pathway in breast cancer and other malignancies, we believe that audiences in different fields will find this overview helpful.

Abstract

The CXCL12/CXCR4 signaling pathway has emerged in the recent years as a key player in breast cancer tumorigenesis. This pathway controls many aspects of breast cancer development including cancer cell proliferation, motility and metastasis to all target organs. Moreover, the CXCL12/CXCR4 cascade affects both immune and stromal cells, creating tumor-supporting microenvironment. In this review, we examine state-of-the-art knowledge about detrimental roles of the CXCL12/CXCR4 signaling, discuss its therapeutic potential and suggest further research directions beneficial both for basic research and personalized medicine in breast cancer.

Morphology, Motility, and Cytoskeletal Architecture of Breast Cancer Cells Depend on Keratin 19 and Substrate

Cancer cells gain motility through events that accompany modulation of cell shape and include altered expression of keratins. However, the role of keratins in change of cancer cell architecture is not well understood. Therefore, we ablated the expression of keratin 19 (K19) in breast cancer cells of the MDA-MB-231 cell line and found that cells lacking K19 become more elongated in culture, with morphological reversion toward the parental phenotype upon transduction of KRT19. Also, the number of actin stress fibers and focal adhesions were significantly reduced in KRT19 knockout (KO) cells. The altered morphology of KRT19 KO cells was then characterized quantitatively using digital holographic microscopy (DHM), which not only confirmed the phenotypic change of KRT19 KO cells but also identified that the K19-dependent morphological change is dependent on the substrate type. A new quantitative method of single cell analysis from DHM, via average phase difference maps, facilitated evaluation of K19-substrate interactive effects on cell morphology. When plated on collagen substrate, KRT19 KO cells were less elongated and resembled parental cells. Assessing single cell motility further showed that while KRT19 KO cells moved faster than parental cells on a rigid surface, this increase in motility became abrogated when cells were plated on collagen. Overall, our study suggests that K19 inhibits cell motility by regulating cell shape in a substrate-dependent manner. Thus, this study provides a potential basis for the altered expression of keratins associated with change in cell shape and motility of cancer cells. © 2020 International Society for Advancement of Cytometry.

Keratin 19 regulates cell cycle pathway and sensitivity of breast cancer cells to CDK inhibitors

Keratin 19 (K19) belongs to the keratin family of proteins, which maintains structural integrity of epithelia. In cancer, K19 is highly expressed in several types where it serves as a diagnostic marker. Despite the positive correlation between higher expression of K19 in tumor and worse patient survival, the role of K19 in breast cancer remains unclear. Therefore, we ablated K19 expression in MCF7 breast cancer cells and found that K19 was required for cell proliferation. Transcriptome analyses of KRT19 knockout cells identified defects in cell cycle progression and levels of target genes of E2F1, a key transcriptional factor for the transition into S phase. Furthermore, proper levels of cyclin dependent kinases (CDKs) and cyclins, including D-type cyclins critical for E2F1 activation, were dependent on K19 expression, and K19-cyclin D co-expression was observed in human breast cancer tissues. Importantly, K19 interacts with cyclin D3, and a loss of K19 resulted in decreased protein stability of cyclin D3 and sensitivity of cells towards CDK inhibitor-induced cell death. Overall, these findings reveal a novel function of K19 in the regulation of cell cycle program and suggest that K19 may be used to predict the efficacy of CDK inhibitors for treatments of breast cancer.

Intermediate Filaments as Effectors of Cancer Development and Metastasis: A Focus on Keratins, Vimentin, and Nestin

Intermediate filament (IF) proteins make up the largest family of cytoskeletal proteins in metazoans, and are traditionally known for their roles in fostering structural integrity in cells and tissues. Remarkably, individual IF genes are tightly regulated in a fashion that reflects the type of tissue, its developmental and differentiation stages, and biological context. In cancer, IF proteins serve as diagnostic markers, as tumor cells partially retain their original signature expression of IF proteins. However, there are also characteristic alterations in IF gene expression and protein regulation. The use of high throughput analytics suggests that tumor-associated alterations in IF gene expression have prognostic value. Parallel research is also showing that IF proteins directly and significantly impact several key cellular properties, including proliferation, death, migration, and invasiveness, with a demonstrated impact on the development, progression, and characteristics of various tumors. In this review, we draw from recent studies focused on three IF proteins most associated with cancer (keratins, vimentin, and nestin) to highlight how several “hallmarks of cancer” described by Hanahan and Weinberg are impacted by IF proteins. The evidence already in hand establishes that IF proteins function beyond their classical roles as markers and serve as effectors of tumorigenesis.

Liquid biopsies

Liquid biopsy is based on minimally invasive blood tests and has a high potential to significantly change the therapeutic strategy in cancer patients, providing an extremely powerful and reliable noninvasive clinical tool for the individual molecular profiling of patients in real time. Liquid biopsy approaches include the analysis of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), circulating miRNAs, and tumor-derived extracellular vesicles (EVs) that are shed from primary tumors and their metastatic sites into peripheral blood. The major advantage of liquid biopsy analysis is that it is minimally invasive, and can be serially repeated, thus allowing extracting information from the tumor in real time. Moreover, the identification of predictive biomarkers in peripheral blood that can monitor response to therapy in real time holds a very strong potential for novel approaches in the therapeutic management of cancer patients. In this review, we summarize recent knowledge on CTCs and ctDNA and discuss future trends in the field.

KRT19 and CEACAM5 mRNA-marked circulated tumor cells indicate unfavorable prognosis of breast cancer patients

AIM

To investigate the clinical and prognostic significance of circulated tumor cells (CTC) marked by cytokeratin 19 coding gene KRT19 mRNA and carcinoembryonic antigen coding gene CEACAM5 mRNA in preoperative peripheral blood of breast cancer patients and provide molecular markers for breast cancer metastasis risk.

METHODS

The mRNA levels of KRT19 and CEACAM5 in preoperative peripheral blood of breast cancer patients without (n = 603) and with (n = 76) distant metastases at the time of initial diagnosis were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The relationship between CTC_KRT19, CTC_CEACAM5 and clinicopathological features, local recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), or overall survival (OS) was statistically analyzed.

RESULTS

In different pathological stages of breast cancer, the rates of CTC_KRT19-pos and CTC_CEACAM5-pos increased with the increase of the stages (P = 0.077 and P = 0.004). Preoperative CTC_KRT19-pos in breast cancer patients was closely related to the lymph node metastasis statues (P < 0.0001), and had no significant correlation with other clinicopathological features. There was no significant correlation between CTC_CEACAM5 and the clinicopathological features. Patients with high levels of CTC double-marked by KRT19 and CEACAM5 mRNA had shorter DMFS (P < 0.0001) and OS (P = 0.016) for patients with breast cancer. The 7-year DMFS rates for the low-, intermediate-, and high-risk groups were 90.7%, 67.5%, and 59.1%, respectively (P < 0.0001). The prognosis of patients with decreased KRT19 and CEACAM5 mRNA after treatment is better than that of patients who have not decreased, and the combination of the two indicators is better than the single one for predicting PFS (P = 0.002 compare with P = 0.036 or P = 0.047).

CONCLUSION

Double-marked CTC by KRT19 and CEACAM5 mRNA is a prognostic index of breast cancer patients before surgery and after chemotherapy. Single-marked CTC by KRT19 mRNA indicates lymph node statues of preoperative patients. Therefore, the RT-qPCR-based molecular diagnosis of CTC could be used for prognostic prediction of breast cancer patients and guiding clinical treatment.

High BMI1 mRNA expression in peripheral whole blood is associated with favorable prognosis in advanced non-small cell lung cancer patients

Polycomb group member protein BMI1 is involved in maintaining cell identity, proliferation, differentiation and human oncogenesis. In the present study, we determined BMI1 mRNA expression in whole blood and evaluated the impact of the expression level on the treatment response and survival of 96 advanced NSCLC patients treated with first-line platinum-based chemotherapy. We also determined BMI1 mRNA expression in primary tumors from 22 operable NSCLC patients treated with radical surgery. We found that compared with control subjects, BMI1 mRNA expression in whole blood of advanced NSCLC patients was decreased (P<0.001). Similarly, we observed decreased BMI1 mRNA expression in primary tumors compared to normal lungs from operable NSCLC patients (P=0.001). We found high BMI1 mRNA expression in blood was associated with longer progression-free survival (PFS) (P=0.049) and overall survival (OS) (P=0.012) in advanced NSCLC patients treated with first-line platinum-based chemotherapy. However, no association between the BMI1 mRNA level and response to chemotherapy was found (P=0.21). Multivariate Cox proportional hazards regression analysis showed elevated BMI1 mRNA level in whole blood was an independent prognostic factor for longer PFS (P=0.012) and OS (P<0.001). In conclusion, BMI1 mRNA expression in whole blood might represent a new biomarker for the diagnosis and prognosis of NSCLC.

Establishment of a multimarker qPCR panel for the molecular characterization of circulating tumor cells in blood samples of metastatic breast cancer patients during the course of palliative treatment

Background

Circulating tumor cells (CTC) are discussed to be an ideal surrogate marker for individualized treatment in metastatic breast cancer (MBC) since metastatic tissue is often difficult to obtain for repeated analysis. We established a nine gene qPCR panel to characterize the heterogeneous CTC population in MBC patients including epithelial CTC, their receptors (EPCAM, ERBB2, ERBB3, EGFR) CTC in Epithelial-Mesenchymal-Transition [(EMT); PIK3CA, AKT2), stem cell-like CTC (ALDH1) as well as resistant CTC (ERCC1, AURKA] to identify individual therapeutic targets.

Results

At TP0, at least one marker was detected in 84%, at TP1 in 74% and at TP2 in 79% of the patients, respectively. The expression of ERBB2, ERBB3 and ERCC1 alone or in combination with AURKA was significantly associated with therapy failure. ERBB2 + CTC were only detected in patients not receiving ERBB2 targeted therapies which correlated with no response. Furthermore, patients responding at TP2 had a significantly prolonged overall-survival than patients never responding (p = 0.0090).

Patients and Methods

2 × 5 ml blood of 62 MBC patients was collected at the time of disease progression (TP0) and at two clinical staging time points (TP1 and TP2) after 8–12 weeks of chemo-, hormone or antibody therapy for the detection of CTC (AdnaTest EMT-2/StemCell Select™, QIAGEN Hannover GmbH, Germany). After pre-amplification, multiplex qPCR was performed. Establishment was performed using various cancer cell lines. PTPRC (Protein tyrosine phosphatase receptor type C) and GAPDH served as controls.

Conclusions

Monitoring MBC patients using a multimarker qPCR panel for the characterization of CTC might help to treat patients accordingly in the future.

Detection of Minimal Residual Disease and Its Clinical Applications in Melanoma and Breast Cancer Patients

Melanoma and breast cancer (BC) patients face a high risk of recurrence and disease progression after curative surgery and/or therapeutic treatment. Monitoring for minimal residual disease (MRD) during a disease-free follow-up period would greatly improve patient outcomes through earlier detection of relapse or treatment resistance. However, MRD monitoring in solid tumors such as melanoma and BC are not well established. Here, we discuss the clinical applications of MRD monitoring in melanoma and BC patients and highlight the current approaches for detecting MRD in these solid tumors.

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

Background

To 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.

Methods

CTCs 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.

Results

Sequential 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 (p<0.001) and the absolute number (p<0.001) 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).

Conclusions

CK⁺/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.

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.

Assessment of Cytokeratin-19 Gene Expression in Peripheral Blood of Breast Cancer Patients and Breast Cancer Cell Lines

Detection of cytokeratin-19 (CK19) expression as an epithelial-specific marker in circulating tumor cells (CTCs) of breast cancer patients can be important for diagnostic purposes. Comparison of CK19 expression in breast cancer cell lines can indicate that expression of this marker is different in various breast cancer cell lines based on their category. Thirty-five breast cancer patients were evaluated for detection of CK19 mRNA in their peripheral blood using CK19-specific primers and a nested reverse transcriptase polymerase chain reaction (RT-PCR) technique. CK19 expression levels were detected in MCF7, T47D, SK-BR-3, and MDA-MB-231 cell lines by semiquantitative RT-PCR and Western blot analyses. Statistical analysis of our data indicates that there is no significant difference between CK19 expression and histopathological parameters and some molecular markers, including Ki-67, HER-2, and P53, but there are statistically significant correlations between estrogen receptor (P = 0.040) and progesterone receptor (P = 0.046) with CK19 expression. CK19 expression was detected in MCF7, T47D, and SK-BR-3 cell lines but not in MDA-MB-231 cell line. More studies are needed to determine the relationship between this marker and other markers in the diagnosis and treatment of breast cancer. On the other hand, the study of different markers using breast cancer cell lines as experimental models of breast cancer could have an impact on improving the health outcomes of patients with breast cancer.

The Role of CTCs as Tumor Biomarkers

Detection of Circulating Tumor Cells (CTCs) in peripheral blood can serve as a "liquid biopsy" approach and as a source of valuable tumor markers. CTCs are rare, and thus their detection, enumeration and molecular characterization are very challenging. CTCs have the unique characteristic to be non-invasively isolated from blood and used to follow patients over time, since these cells can provide significant information for better understanding tumour biology and tumour cell dissemination. CTCs molecular characterization offers the unique potential to understand better the biology of metastasis and resistance to established therapies and their analysis presents nowadays a promising field for both advanced and early stage patients. In this chapter we focus on the latest findings concerning the clinical relevance of CTC detection and enumeration, and discuss their potential as tumor biomarkers in various types of solid cancers. We also highlight the importance of performing comparison studies between these different methodologies and external quality control systems for establishing CTCs as tumor biomarkers in the routine clinical setting.

Gene expression profiling and DNA methylation analyses of CTCs

A variety of molecular assays have been developed for CTCs detection and molecular characterization. Molecular assays are based on the nucleic acid analysis in CTCs and are based on total RNA isolation and subsequent mRNA quantification of specific genes, or isolation of genomic DNA that can be for DNA methylation studies and mutation analysis. This review is mainly focused on gene expression and methylation studies in CTCs in various types of cancer.

PIK3CA mutational status in circulating tumor cells can change during disease recurrence or progression in patients with breast cancer

PURPOSE

Molecular characterization of circulating tumor cells (CTC) is crucial for the investigation of molecular-targeted therapies while PIK3CA somatic mutations play a crucial role in therapy response. We investigated the presence of PIK3CA mutations in CTC and whether this is associated with clinical outcome.

EXPERIMENTAL DESIGN

We developed and validated an ultrasensitive methodology for the detection of PIK3CA mutations that is based on a combination of allele-specific, asymmetric rapid PCR and melting analysis. We analyzed PIK3CA hotspot mutations in: (i) a training group consisting of EpCAM-positive CTC fraction from 37 patients with clinically confirmed metastasis, and 26 healthy female volunteers and 15 primary breast tumor tissues and (ii) an independent group consisting of EpCAM-positive CTC fraction from 57 metastatic and 118 operable breast cancer patients and 76 corresponding primary tumors.

RESULTS

The assay could detect 0.05% of mutated dsDNA in the presence of 99.95% wtDNA for both exons (9 and 20) and was highly specific (0/26 healthy donors). PIK3CA mutations were identified in EpCAM-positive CTC in 20 of 57(35.1%) and in 23 of 118 (19.5%) patients with metastatic and operable breast cancer, and in 45 of 76(59.2%) corresponding FFPEs. Our data indicate that PIK3CA mutational status in CTCs can change during disease progression and is associated with worse survival (P = 0.047).

CONCLUSIONS

PIK3CA hotspot mutations are present at a relatively high frequency in CTCs and their presence is associated with worse survival in patients with breast cancer with metastasis. Evaluation of PIK3CA mutational status in CTCs is a strategy with potential clinical application.

Fine-needle aspirate CYFRA 21-1, an innovative new marker for diagnosis of axillary lymph node metastasis in breast cancer patients

To compare the value of cytokeratin fragment 21-1 (CYFRA 21-1) concentration in the fine-needle biopsy aspirates (fine needle aspirate [FNA] CYFRA 21-1) with cytopathology of fine-needle aspiration biopsy (FNA cytology) and to assess whether CYFRA 21-1 concentrations from ultrasound-guided fine-needle aspiration biopsy (US-FNAB) specimens (FNA CYFRA 21-1) is not inferior to FNA cytology in the diagnosis of axillary lymph node (ALN) metastasis of breast cancer patients.This study received institutional review board approval, and written informed consent was obtained from all patients. US-FNAB was performed in 373 ALNs from 358 patients with invasive breast cancer. Concentrations of CYFRA 21-1 were measured from washouts of the syringe used during US-FNAB (FNA CYFRA 21-1), and ALN metastasis was determined using a cutoff value of 1.93 ng/mL. FNA cytology, intraoperative sentinel lymph node biopsy, and surgical pathology results were reviewed and analyzed. The noninferiority margin for the difference in accuracies between FNA cytology and FNA CYFRA 21-1 was set as 5%.Among 373 ALNs, 136 (36.5%) were benign, and 237 (63.5%) were metastatic. The mean FNA CYFRA 21-1 was significantly higher in metastatic ALNs compared to that in benign ALNs (P = 0.001). For the diagnosis of ALN metastasis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FNA CYFRA 21-1 (cutoff value 1.93 ng/mL) were not significantly different from those of FNA cytology (P > 0.05). FNA CYFRA 21-1 reached statistical noninferiority to FNA cytology in terms of diagnostic accuracy for ALN metastasis. Of the 20 ALNs (8 metastasis, 12 benign) that showed insufficient results on FNA cytology, FNA CYFRA 21-1 accurately diagnosed 15 ALNs (4 metastasis, 11 benign).The diagnostic performance of FNA CYFRA 21-1 is comparable with that of FNA cytology for breast cancer ALN metastasis. Our results indicate that FNA CYFRA 21-1, using an US-FNAB specimen, can be a useful method equal to FNA cytology in terms of diagnostic accuracy.

Clinical implications of circulating tumor cells of breast cancer patients: role of epithelial-mesenchymal plasticity

There is increasing interest in circulating tumor cells (CTCs) due to their purported role in breast cancer metastasis, and their potential as a “liquid biopsy” tool in breast cancer diagnosis and management. There are, however, questions with regards to the reliability and consistency of CTC detection and to the relationship between CTCs and prognosis, which is limiting their clinical utility. There is increasing acceptance that the ability of CTCs to alter from an epithelial to mesenchymal phenotype plays an important role in determining the metastatic potential of these cells. This review examines the phenotypic and genetic variation, which has been reported within CTC populations. Importantly, we discuss how the detection and characterization of CTCs provides additional and often differing information from that obtained from the primary tumor, and how this may be utilized in determining prognosis and treatment options. It has been shown for example that hormone receptor status often differs between the primary tumor and CTCs, which may help to explain failure of endocrine treatment. We examine how CTC status may introduce alternative treatment options and also how they may be used to monitor treatment. Finally, we discuss the most interesting current clinical trials involving CTC analysis and note further research that is required before the breast cancer “liquid biopsy” can be realized.

Markers for the identification of late breast cancer recurrence

Postmenopausal women with early breast cancer are at an ongoing risk of relapse, even after successful surgery and treatment of the primary tumor. The treatment of breast cancer has changed in the past few years because of the discovery of prognostic and predictive biomarkers that allow individualized breast cancer treatment. However, it is still not clear how to identify women that are at high risk of a late recurrence. Clinical parameters are good prognostic markers for early recurrence, but only nodal status and, to a lesser extent, tumor size have proven to be strong prognostic markers for late recurrence. Multi-gene signatures have become widely used for the prediction of overall recurrence risk and tailoring administration of adjuvant chemotherapy, but only a few have been shown to be prognostic for late (distant) relapse. There is a need to accurately identify women who may benefit from extended endocrine therapy but also those who may be spared any additional treatment. Recent results from large clinical trials have shown that the research is going in the right direction, and these results might help to optimize extended endocrine therapy for patients with early breast cancer. However, further research is needed to select individual biomarkers or multi-gene signatures that offer identification of late recurrence specifically and thus justify routine use of these tests in the clinical setting.

Markers for the identification of late breast cancer recurrence

Postmenopausal women with early breast cancer are at an ongoing risk of relapse, even after successful surgery and treatment of the primary tumor. The treatment of breast cancer has changed in the past few years because of the discovery of prognostic and predictive biomarkers that allow individualized breast cancer treatment. However, it is still not clear how to identify women that are at high risk of a late recurrence. Clinical parameters are good prognostic markers for early recurrence, but only nodal status and, to a lesser extent, tumor size have proven to be strong prognostic markers for late recurrence. Multi-gene signatures have become widely used for the prediction of overall recurrence risk and tailoring administration of adjuvant chemotherapy, but only a few have been shown to be prognostic for late (distant) relapse. There is a need to accurately identify women who may benefit from extended endocrine therapy but also those who may be spared any additional treatment. Recent results from large clinical trials have shown that the research is going in the right direction, and these results might help to optimize extended endocrine therapy for patients with early breast cancer. However, further research is needed to select individual biomarkers or multi-gene signatures that offer identification of late recurrence specifically and thus justify routine use of these tests in the clinical setting.

The expression of CK-19 gene in circulating tumor cells of blood samples of metastatic breast cancer women

Breast cancer is the most common cancer in women worldwide. Breast cancer in one third of all patients will go on to metastasis, which is the main cause of mortality in cancer cases. Tumor cells detach from primary tumor and enter into the circulation as circulating tumor cells (CTCs) which can form metastatic lesions. In this study, the expression of CK-19 gene in blood samples of metastatic breast cancer women was investigated and compared to control group. Twenty one patients with metastatic breast cancer and 20 healthy female volunteers enrolled in this study. For every patient and healthy donor 10 ml peripheral blood was collected. Peripheral blood mononuclear cells were isolated by gradient density centrifugation using Ficoll Hypaque. CK-19 gene expression was evaluated using SYBR green-based real-time quantitative polymerase chain reaction assays. The relative expression level of CK-19 was calculated using the 2(-ΔΔCt) analysis method. The mean of CK-19 expression was increased in metastatic breast cancer when compared to those of normal women (1.50 fold). 38.1% of the metastatic breast cancer patients showed CK-19 mRNA-detectable CTCs in their blood samples. There was no statistically significant difference between the relative expression level of CK-19 and the patient's clinicopathological characteristics. According to our knowledge, no study for determining CTC biomarkers in Iranian breast cancer women patients has yet been established. Our results suggest that the CK-19 mRNA expression investigation may be useful for monitoring CTCs in the blood of metastatic breast cancer patients, predicting early metastatic relapse or monitoring of anti-metastasis treatments.

Evaluation of proliferation and apoptosis markers in circulating tumor cells of women with early breast cancer who are candidates for tumor dormancy

Introduction

Clinical dormancy is frequently observed in breast cancer. In the present study, we aimed to characterize circulating tumor cells (CTCs) in dormancy candidates (DC) with early breast cancer in terms of proliferation and apoptosis.

Methods

Cytospins of peripheral blood mononuclear cells (PBMCs) were obtained from DC (n = 122) who were disease-free for at least 5 years and from metastatic patients (n = 40) who relapsed more than 5 years after surgery. Sequential samples from eight DC (n = 36) who maintained a prolonged disease-free status and from eight DC (n = 27) presenting late relapse during follow-up, were also analyzed. PBMCs were triple stained with a pancytokeratin, antibody along with anti-Ki67 and anti-M30 antibodies as proliferation and apoptosis markers, respectively.

Results

CTCs were identified in 40 (33%) of 122 DC and in 15 (37.5%) of 40 metastatic patients. In total, twenty-five (62.5%) DC had exclusively dormant (Ki67(-)/M30(-)), seven (17.5%) had proliferative Ki67(+)/M30(-), four (10%) had apoptotic Ki67(-)/M30(+) and four (10%) had both phenotypes of proliferative and apoptotic CTCs. In comparison, 53.4% of CTC-positive metastatic patients had exclusively dormant and 46.6% had proliferative CTCs; none had apoptotic CTCs (P = 0.039). Among all CTCs detected in DC patients, 82.4% were dormant, whereas in the nondormant population, 32.5% were proliferative and 67.5% apoptotic. The respective percentages in metastatic patients were 59.1%, 100% and 0% (P <0.0001). Moreover, apoptotic CTCs prevailed among nondormant CTCs detected in sequential samples from DC who remained in a prolonged disease-free status compared to those presenting late relapse during follow-up (70.6% versus 43.5% (P = 0.0002)).

Conclusions

The apoptotic index of CTCs is increased during clinical dormancy, whereas the proliferation index is increased on relapse. In addition, apoptotic CTCs are more frequently encountered during follow-up in DC patients who remain disease-free compared to those with subsequent late relapse, suggesting that monitoring proliferation and apoptosis in CTCs during clinical dormancy merits further investigation as a tool for predicting late disease recurrence.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0485-8) contains supplementary material, which is available to authorized users.

Circulating tumor cells in non-metastatic triple-negative breast cancer

Circulating tumor cells (CTCs) can be identified in approximately 25 % of stage I-III breast cancer patients; CTCs presence is a predictor of poor outcome in metastatic breast cancer, but little is known regarding the prognostic significance of CTCs in non-metastatic triple-negative breast cancer (TNBC) patients. The aim of this study was to determine whether CTCs predict worse outcome in non-metastatic TNBC patients. We evaluated CTCs in 113 patients with stages I-III TNBC at the time of definitive surgery. CTCs were assessed using the CellSearch System^®. Progression-free and overall survival were defined as time elapsed between date of diagnosis and either date of clinical disease progression, death, or last follow-up. Log-rank test and Cox regression analysis were used to determine associations of CTCs with progression-free and overall survival. The median follow-up was 40 months. CTCs were identified in 23/113 (20 %) of patients. No primary tumor characteristic or lymph node status predicted the presence of CTCs. The identification of ≥2 CTCs predicted shorter progression-free (log rank P ≤ 0.001; hazard ratio 8.30, 95 % CI 2.61–26.37) and overall survival (log rank P = 0.0004; hazard ratio 7.19, 95 % CI 1.98–26.06) versus survival for patients with <2 CTCs. Two or more CTCs predict shorter progression-free and overall survival in TNBC patients. Larger studies are needed to determine whether CTC assessment provides beneficial information that could be used in stratifying TNBC patients at increased risk for disease progression. Finally, CTCs characterization could facilitate the development of novel treatment approaches for TNBC.

Identification of proteins with increased levels in ameloblastic carcinoma

PURPOSE

The comparative proteomic approach by a combination of 2-dimensional electrophoresis and matrix-assisted laser desorption-ionization-time of flight mass spectrometry (MS) analysis is an attractive strategy for the discovery of cancer biomarkers and therapeutic targets. The identification of protein biomarkers associated with ameloblastic carcinoma (AC), a malignant epithelial odontogenic tumor, will potentially improve the diagnostic and prognostic accuracy for this malignant neoplasm. The aim of the present study was to identify highly expressed proteins in AC that could be considered as potential biomarkers.

MATERIALS AND METHODS

The protein profile of an AC was compared with the protein profiles of 3 cases of benign ameloblastoma. Proteins that showed increased levels in AC were identified using MS, and the augmented amount of some of these proteins in the malignant lesion was confirmed by Western blot or immunohistochemistry.

RESULTS

We detected a total of 782 spots in the protein profile of AC, and 19 of them, showing elevated levels compared with benign ameloblastoma, were identified using MS. These proteins have been implicated in several cellular functions, such as cell structure, metabolism, stress response, and signal transduction.

CONCLUSIONS

The increased expression of the identified proteins and the minor expression of some proteins that might inhibit tumor progression could be involved in the evolution from a benign lesion to carcinoma.

Circulating tumor cells as promising novel biomarkers in solid cancers

The presence of circulating tumor cells (CTCs) in peripheral blood can serve as a "liquid biopsy" approach and has thus emerged lately as one of the hottest fields in cancer research. CTCs can be isolated from blood in a non-invasive approach, and can be used to follow patients over time since these cells can provide significant information for a better understanding of tumor biology and tumor cell dissemination. CTC molecular characterization offers the unique potential to better understand the biology of metastasis and resistance to established therapies, and analysis of these cells presents a promising field for both advanced and early-stage patients. CTC detection, enumeration, and molecular characterization are very challenging since CTCs are rare, and the amount of available sample is very limited. Since detection of CTCs has been shown to be of considerable utility in the clinical management of patients with solid cancers, various analytical systems for their isolation and detection have been developed. New areas of research are directed towards developing novel assays for single-CTC isolation and molecular characterization. The clinical significance of CTCs has been evaluated in many types of solid cancers, and the CTC enumeration test in metastatic breast, colorectal, and prostate cancer was cleared by the FDA almost a decade ago. This review is mainly focused on the clinical potential of CTCs as novel biomarkers in 10 different types of solid cancers: breast, ovarian, prostate, lung, colorectal, hepatocellular carcinoma, pancreatic, head and neck, bladder cancer and melanoma.

CK-19 mRNA-positive cells in peripheral blood predict treatment efficacy and survival in small-cell lung cancer patients

Small-cell lung caner (SCLC) is the most aggressive form of lung cancer. The aim of this study was to investigate whether the presence of cytokeratin-19 (CK-19) mRNA-positive circulating tumor cells (CTCs) predicts treatment response, progression-free survival (PFS), and overall survival (OS) in SCLC patients who received standard therapy. Fifty-five SCLC patients were enrolled in this single-center prospective study. CK-19 mRNA-positive CTCs in blood samples were detected using real-time quantitative-PCR assay before the initiation of chemotherapy (B0) and after one chemotherapy cycle (B1) and three chemotherapy cycles (B3). The association with known prognostic factors and the effect of CK-19 mRNA-positive CTCs on patients' prognosis were analyzed. Patients with positivity for CK-19 mRNA-positive CTCs at B0, B1, and B3 time points had shorter PFS and OS compared with patients without (P = 0.014 and P = 0.01, respectively, at B0; P = 0.008 and P = 0.002, respectively, at B1; P = 0.003 and P = 0.001, respectively, at B3). Conversion of initial positivity for CK-19 mRNA-positive CTCs to negativity at B1 and B3 time points was associated with longer PFS and OS compared with patients with persistent positivity at three time points (P = 0.008 and P = 0.010, respectively). Multivariate analysis demonstrated that the presence of CK-19 mRNA-positive CTCs at B0, B1, and B3 time points remained strong predictors of PFS and OS after adjustment for clinically significant factors. In conclusion, detection of CK-19 mRNA-positive CTCs before and during chemotherapy is an accurate indication of subsequent disease progression and mortality for SCLC patients.

Relevance of molecular characterization of circulating tumor cells in breast cancer in the era of targeted therapies

Development in circulating tumor cells (CTCs) technologies represents a valuable tool for the better understanding of tumor biology. The clinical relevance of CTCs as a prognostic factor is well established both in metastatic and early-stage breast cancer patients. The eradication or decrease of CTCs following treatment is associated with improved clinical outcomes. Because of the availability of novel cancer treatments that specifically target tumor cells underlying signaling pathways, molecular characterization of CTCs has strong potential to translate into personalized treatments. A handful of studies have explored relevant markers such as the estrogen and progesterone receptor, HER2 and EGF receptor. However, there is not a single validation of a molecular marker in CTCs that provides prognostic information or predicts response to cancer therapies. This review describes the latest results on the characterization of breast cancer CTCs with a focus on CTC biology and implications in clinical practice.

Gene expression markers in circulating tumor cells may predict bone metastasis and response to hormonal treatment in breast cancer

Circulating tumor cells (CTCs) have recently attracted attention due to their potential as prognostic and predictive markers for the clinical management of metastatic breast cancer patients. The isolation of CTCs from patients may enable the molecular characterization of these cells, which may help establish a minimally invasive assay for the prediction of metastasis and further optimization of treatment. Molecular markers of proven clinical value may therefore be useful in predicting disease aggressiveness and response to treatment. In our earlier study, we identified a gene signature in breast cancer that appears to be significantly associated with bone metastasis. Among the genes that constitute this signature, trefoil factor 1 (TFF1) was identified as the most differentially expressed gene associated with bone metastasis. In this study, we investigated 25 candidate gene markers in the CTCs of metastatic breast cancer patients with different metastatic sites. The panel of the 25 markers was investigated in 80 baseline samples (first blood draw of CTCs) and 30 follow-up samples. In addition, 40 healthy blood donors (HBDs) were analyzed as controls. The assay was performed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) with RNA extracted from CTCs captured by the CellSearch system. Our study indicated that 12 of the genes were uniquely expressed in CTCs and 10 were highly expressed in the CTCs obtained from patients compared to those obtained from HBDs. Among these genes, the expression of keratin 19 was highly correlated with the CTC count. The TFF1 expression in CTCs was a strong predictor of bone metastasis and the patients with a high expression of estrogen receptor β in CTCs exhibited a better response to hormonal treatment. Molecular characterization of these genes in CTCs may provide a better understanding of the mechanism underlying tumor metastasis and identify gene markers in CTCs for predicting disease progression and response to treatment.

Detection and prognostic significance of circulating tumor cells in nonmetastatic breast cancer patients

SUMMARY Distant metastasis remains the primary cause of death for breast cancer patients. Metastasis is a complex, multistep process wherein a subset of cells from a heterogeneous tumor acquire the ability to disseminate from the primary tumor and invade the blood and/or lymph nodes. Although tumor size, tumor characteristics and axillary lymph node status are the most common parameters utilized to predict disease recurrence in nonmetastatic patients, a significant number of lymph node-negative patients with localized disease will develop distant metastases despite successful primary treatment. These data suggest that tumor cell dissemination can occur early in disease progression, sometimes bypassing the lymphatic system. Occult micrometastases, or circulating tumor cells in the blood, are rare tumor cells that remain undetected by standard histopathogical and high-resolution imaging methodologies. This review focuses on current methodologies used to detect circulating tumor cells and their prognostic significance in nonmetastatic breast cancer patients.