The clinical significance of disseminated tumor cells in breast cancer

Searching for the "Holy Grail" of breast cancer recurrence risk: a narrative review of the hunt for a better biomarker and the promise of circulating tumor DNA (ctDNA)

BACKGROUND

This paper is a narrative review of a major clinical challenge at the heart of breast cancer care: determining which patients are at risk of recurrence, which require systemic therapy, and which remain at risk in the survivorship phase of care despite initial therapy.

METHODS

We review the literature on prognostic and predictive biomarkers in breast cancer with a focus on detection of minimal residual disease.

RESULTS

While we have many tools to estimate and refine risk that are used to individualize local and systemic therapy, we know that we continue to over treat many patients and undertreat others. Many patients also experience what is, at least in hindsight, needless fear of recurrence. In this review, we frame this dilemma for the practicing breast oncologist and discuss the search for what we term the "holy grail" of breast cancer evaluation: the ideal biomarker of residual distant disease. We review the history of attempts to address this problem and the up-to-date science on biomarkers, circulating tumor cells and circulating tumor DNA (ctDNA).

CONCLUSION

This review suggests that the emerging promise of ctDNA may help resolve a crticical dilemma at the heart of breast cancer care, and improve prognostication, treatment selection, and outcomes for patients with breast cancer.

Myeloid-like tumor hybrid cells in bone marrow promote progression of prostate cancer bone metastasis

BACKGROUND

Bone metastasis is the leading cause of death in patients with prostate cancer (PCa) and currently has no effective treatment. Disseminated tumor cells in bone marrow often obtain new characteristics to cause therapy resistance and tumor recurrence. Thus, understanding the status of disseminated prostate cancer cells in bone marrow is crucial for developing a new treatment.

METHODS

We analyzed the transcriptome of disseminated tumor cells from a single cell RNA-sequencing data of PCa bone metastases. We built a bone metastasis model through caudal artery injection of tumor cells, and sorted the tumor hybrid cells by flow cytometry. We performed multi-omics analysis, including transcriptomic, proteomic and phosphoproteomic analysis, to compare the difference between the tumor hybrid cells and parental cells. In vivo experiments were performed to analyze the tumor growth rate, metastatic and tumorigenic potential, drug and radiation sensitivity in hybrid cells. Single cell RNA-sequencing and CyTOF were performed to analyze the impact of hybrid cells on tumor microenvironment.

RESULTS

Here, we identified a unique cluster of cancer cells in PCa bone metastases, which expressed myeloid cell markers and showed a significant change in pathways related to immune regulation and tumor progression. We found that cell fusion between disseminated tumor cells and bone marrow cells can be source of these myeloid-like tumor cells. Multi-omics showed the pathways related to cell adhesion and proliferation, such as focal adhesion, tight junction, DNA replication, and cell cycle, were most significantly changed in these hybrid cells. In vivo experiment showed hybrid cells had a significantly increased proliferative rate, and metastatic potential. Single cell RNA-sequencing and CyTOF showed tumor-associated neutrophils/monocytes/macrophages were highly enriched in hybrid cells-induced tumor microenvironment with a higher immunosuppressive capacity. Otherwise, the hybrid cells showed an enhanced EMT phenotype with higher tumorigenicity, and were resistant to docetaxel and ferroptosis, but sensitive to radiotherapy.

CONCLUSION

Taken together, our data demonstrate that spontaneous cell fusion in bone marrow can generate myeloid-like tumor hybrid cells that promote the progression of bone metastasis, and these unique population of disseminated tumor cells can provide a potential therapeutic target for PCa bone metastasis.

Expression of Carboxypeptidase A3 and Tryptase as Markers for Lymph Node Metastasis of Canine Cutaneous Mast Cell Tumors

Detection of metastatic mast cell tumors (MCTs) in lymph nodes is a critical factor for treatment, prognosis, and clinical management. Presence/absence of mast cells in the lymph nodes cannot be used as a sole parameter to determine metastasis due to the inability to differentiate neoplastic from non-neoplastic/inflammatory mast cells. While cytologic and histopathologic classifications for assessment of metastatic MCTs based on the numbers and distribution of mast cells have been developed, inconsistency between the clinical interpretation of these grading schemes and actual metastatic status occurs. The aim of this study is to identify a novel diagnostic tool to accurately predict overt metastatic mast cell tumors in lymph nodes. We investigated the possibility of using RT-qPCR to detect mRNA expression of mast cell-specific genes in lymph nodes with different stages of MCT metastatic classification. We are able to establish a highly sensitive and discriminating RT-qPCR measuring Carboxy peptidase A3 (CPA3) and tryptase mRNA expression and identify the cut-off values with high sensitivity and specificity for overt metastatic MCTs in lymph nodes. An area of future interest would be to expand our analysis of the extent to which cut-off values for these markers in correctly identifying disease status, as well as predicting clinical outcomes and survival times. This would offer valuable information regarding the practical applicability of this technique and may enable us to improve our standards of detection metastasis, including possibility of molecular analysis of cytologic specimens obtained from suspicious nodes subjected to surgical excision.

Utility of urinary ctDNA to monitoring minimal residual disease in early breast cancer patients

BACKGROUND

Cancer recurrence for patients with early breast cancer is significant. Patients will benefit from more non-invasive modes of monitoring and we aim to study the feasibility of urinary circulating tumor DNA (ctDNA) to monitor for residual disease (MRD).

METHODS

In this longitudinal study, 300 early breast cancer patients were recruited prospectively. Measurements were taken prior to treatment and at different time points thereafter for a total of 8 measurements. Comparisons were made with healthy volunteers and patients without detectable mutations in urine specimens. Disease free relapse were correlated to both urinary DNA quantity and ctDNA concentration.

RESULTS

Baseline index measurements showed 38% of patients with detectable mutations. The concordance with biopsy tissues was 97.3%. Overall, breast cancer patients had higher urinary DNA compared with healthy volunteers. Over time, fluctuations in urinary DNA was negligible in healthy volunteers, indicating the stability of the marker. Among the patients with detectable mutations, we observed that higher urinary DNA quantity measurements at 6-month and patients with positive mutations were associated with greater risk of relapse. Hazard ratios for patients in this category was 1.65 (95% CI 1.26-2.16) and 1.98 (95% CI 1.48-2.63) respectively.

CONCLUSION

Urinary DNA offers non-invasive probing and real-time monitoring of breast cancer relapse. Our results demonstrated clear clinical relevance in breast cancer and significant risk profiling of early breast cancer patients. This potentially aids to complement current cancer relapse monitoring and may help in early intervention.

The Metabolic Mechanisms of Breast Cancer Metastasis

Breast cancer is one of the most common malignancy among women worldwide. Metastasis is mainly responsible for treatment failure and is the cause of most breast cancer deaths. The role of metabolism in the progression and metastasis of breast cancer is gradually being emphasized. However, the regulatory mechanisms that conduce to cancer metastasis by metabolic reprogramming in breast cancer have not been expounded. Breast cancer cells exhibit different metabolic phenotypes depending on their molecular subtypes and metastatic sites. Both intrinsic factors, such as MYC amplification, PIK3CA, and TP53 mutations, and extrinsic factors, such as hypoxia, oxidative stress, and acidosis, contribute to different metabolic reprogramming phenotypes in metastatic breast cancers. Understanding the metabolic mechanisms underlying breast cancer metastasis will provide important clues to develop novel therapeutic approaches for treatment of metastatic breast cancer.

Mechanisms of cancer stem cell therapy

Cancer stem cells (CSCs) are responsible for carcinogenesis and tumorigenesis and are involved in drug and radiation resistance, metastasis, tumor relapse and initiation. Remarkably, they have other abilities such as inheritance of self-renewal and de-differentiation. Hence, targeting CSCs is considered a potential anti-cancer therapeutic strategy. Recent advances in the identification of biomarkers to recognize CSCs and the development of new techniques to evaluate tumorigenic and carcinogenic roles of CSCs are instrumental to this approach. Elucidation of signaling pathways that regulate CSCs colony progression and drug resistance are critical in establishing effective targeted therapies. CSCs play a central key role in immunomodulation, immune evasion and effector immunity, which alters immune system balancing. These include mTOR, SHH, NOTCH and Wnt/β-catering in cancer progression. In this review article, we discuss the importance of these CSCs pathways in cancer therapy.

Nanomedical detection and downstream analysis of circulating tumor cells in head and neck patients

The establishment of novel biomarkers in liquid biopsies of cancer patients has come more into focus in prognostic and diagnostic research efforts. Due to their prognostic relevance disseminated tumor cells or circulating tumor cells are the subject of intensive research and are discussed as early diagnostic indicators for treatment failure and the formation of micrometastases. A potential association of this early-systemic tumor component with poor prognosis of cancer patients could be already demonstrated for various entities including breast, colon, lung, melanoma, ovarian and prostate cancers. Thus, the detection of circulating tumor cells seems to be also applicable for minimal-invasive monitoring of therapy progress in head and neck cancer patients. A major problem of the use in clinical routine is that circulating tumor cells could not be detected by modern imaging techniques. To overcome these limitations highly sensitive detection methods and techniques for their molecular characterization are urgently needed allowing mechanistic understanding and targeting of circulating tumor cells. Especially the medical application of nanotechnology (nanomedical methods) has made valuable contributions to the field. Here, we want to provide a comprehensive overview on (nanomedical) detection methods for circulating tumor cells and discuss their merits, pitfalls and future perspectives especially for head and neck solid squamous cell carcinoma (HNSCC) patients.

Optimization and In Vivo Profiling of a Refined Rat Model of Walker 256 Breast Cancer Cell-Induced Bone Pain Using Behavioral, Radiological, Histological, Immunohistochemical and Pharmacological Methods

In the majority of patients with advanced breast cancer, there is metastatic spread to bones resulting in pain. Clinically available drug treatments for alleviation of breast cancer-induced bone pain (BCIBP) often produce inadequate pain relief due to dose-limiting side-effects. A major impediment to the discovery of novel well-tolerated analgesic agents for the relief of pain due to bony metastases is the fact that most cancer-induced bone pain models in rodents relied on the systemic injection of cancer cells, causing widespread formation of cancer metastases and poor general animal health. Herein, we have established an optimized, clinically relevant Wistar Han female rat model of breast cancer induced bone pain which was characterized using behavioral assessments, radiology, histology, immunohistochemistry and pharmacological methods. In this model that is based on unilateral intra-tibial injection (ITI) of Walker 256 carcinoma cells, animals maintained good health for at least 66 days post-ITI. The temporal development of hindpaw hypersensitivity depended on the initial number of Walker 256 cells inoculated in the tibiae. Hindpaw hypersensitivity resolved after approximately 25 days, in the continued presence of bone tumors as evidenced by ex vivo histology, micro-computed tomography scans and immunohistochemical assessments of tibiae. A possible role for the endogenous opioid system as an internal factor mediating the self-resolving nature of BCIBP was identified based upon the observation that naloxone, a non-selective opioid antagonist, caused the re-emergence of hindpaw hypersensitivity. Bolus dose injections of morphine, gabapentin, amitriptyline and meloxicam all alleviated hindpaw hypersensitivity in a dose-dependent manner. This is a first systematic pharmacological profiling of this model by testing standard analgesic drugs from four important diverse classes, which are used to treat cancer induced bone pain in the clinical setting. Our refined rat model more closely mimics the pathophysiology of this condition in humans and hence is well-suited for probing the mechanisms underpinning breast cancer induced bone pain. In addition, the model may be suitable for efficacy profiling of new molecules from drug discovery programs with potential to be developed as novel agents for alleviation of intractable pain associated with disseminated breast cancer induced bony metastases.

Microfluidic and Nanofluidic Resistive Pulse Sensing: A Review

The resistive pulse sensing (RPS) method based on the Coulter principle is a powerful method for particle counting and sizing in electrolyte solutions. With the advancement of micro- and nano-fabrication technologies, microfluidic and nanofluidic resistive pulse sensing technologies and devices have been developed. Due to the unique advantages of microfluidics and nanofluidics, RPS sensors are enabled with more functions with greatly improved sensitivity and throughput and thus have wide applications in fields of biomedical research, clinical diagnosis, and so on. Firstly, this paper reviews some basic theories of particle sizing and counting. Emphasis is then given to the latest development of microfuidic and nanofluidic RPS technologies within the last 6 years, ranging from some new phenomena, methods of improving the sensitivity and throughput, and their applications, to some popular nanopore or nanochannel fabrication techniques. The future research directions and challenges on microfluidic and nanofluidic RPS are also outlined.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

Detection of circulating tumor cell-specific markers in breast cancer patients using the quantitative RT-PCR assay

BACKGROUND

Breast cancer is a highly prevalent disease among women worldwide. While the expression of certain proteins within breast cancer tumors is used to determine the prognosis and select therapies, additional markers need to be identified. Circulating tumor cells (CTCs) are constituent cells that have detached from a primary tumor to circulate in the bloodstream. CTCs are considered the main source of breast cancer metastases; therefore, detection of CTCs could be a promising diagnostic method for metastatic breast cancer.

METHODS

In this study, the CircleGen CTC RT-qDx assay was used to analyze the mRNA expression levels of six CTC-specific markers including EpCAM, CK19, HER2, Ki67, hTERT, and vimentin with a total of 692 peripheral whole blood samples from 221 breast cancer patients and 376 healthy individuals.

RESULTS

This assay showed high specificity with multiple markers; none of the healthy controls were detected positive, whereas 21.7 and 14 % of breast cancer patients were positive for EpCAM and CK19, respectively. Of the 221 breast cancer patients, 84 (38 %), 46 (20.8 %), 83 (37.6 %), and 39 (17.6 %) were positively for HER2, Ki67, hTERT, and vimentin mRNA, respectively. Of the 84 patients who were HER2 positive, nine (4 %) were also positive for EpCAM, CK19, Ki67, hTERT, and vimentin. Of the 139 breast cancer patients who were HER2 negative, 65 (29.1 %) were negative for EpCAM, CK19, Ki67, hTERT, and vimentin. Furthermore, the EpCAM-positive population decreased from 21.5 to 8.3 % after completion of anti-tumor treatment (TP4). Similarly, the CK19, HER2, hTERT, and vimentin positives also decreased from 13.9 to 9.5 %, from 37.7 to 21.4 %, from 37.2 to 33.3 %, and from 17.5 to 14.3 %, respectively, after completion of anti-tumor treatment. In contrast, the Ki67 positives increased from 20.6 to 41.7 % after completion of anti-tumor treatment.

CONCLUSIONS

mRNA overexpression of six CTC-specific markers was detected by the CircleGen CTC RT-qDx assay with high specificity, and the obtained mRNA expression levels of CTC-specific markers might provide useful criteria to select appropriate anti-tumor treatment for breast cancer patients.

Detection of circulating tumor cells in patients with breast cancer using the quantitative RT-PCR assay for monitoring of therapy efficacy

Circulating tumor cells (CTCs) are an independent prognostic factor for patients with breast cancer. However, the role of CTCs in early breast cancer management is not yet clearly defined. The aim of this study was to isolate and characterize CTCs in blood sample of a breast cancer patient as a biomarker for monitoring treatments efficacy. In this study, 692 blood samples from 221 breast cancer patients and 376 healthy individuals was used to detect CTCs with multiple markers including epithelial cell adhesion molecule (EpCAM), cytokeratin (CK) 19, human epidermal growth factor (HER) 2, Ki67, human telomerase reverse transcriptase (hTERT), and vimentin using quantitative reverse transcription PCR (RT-qPCR). A total of 153 (69.2%) blood samples of 221 patients with breast cancer were found to be positive for at least one of the cancer-associated marker gene before treatment. After chemotherapy, no CTCs were found in 28 (33.3%) of the 84 blood samples analyzed for the presence of CTCs using the RT-qPCR, whereas 56 (66.7%) blood samples were still found to be positive for at least one of the markers. After completing the therapy, the CTC positivity rate decreased to 7 (20.6%) in the neoadjuvant group, whereas this increased to 7 (14%) cases in the adjuvant group. There was no statistically significant relationship between TNM stage and detection of CTC-related markers. Data from this study suggest that RT-qPCR assay for the detection of CTC markers might be useful in selecting appropriate therapeutics and for monitoring treatment efficacy in breast cancer patients.

Breast cancer metastasis: issues for the personalization of its prevention and treatment

Despite important progress in adjuvant and neoadjuvant therapies, metastatic disease often develops in breast cancer patients and remains the leading cause of their deaths. For patients with established metastatic disease, therapy is palliative, with few breaks and with mounting adverse effects. Many have hypothesized that a personalized or precision approach (the terms are used interchangeably) to cancer therapy, in which treatment is based on the individual characteristics of each patient, will provide better outcomes. Here, we discuss the molecular basis of breast cancer metastasis and the challenges in personalization of treatment. The instability of metastatic tumors remains a leading obstacle to personalization, because information from a patient's primary tumor may not accurately reflect the metastasis, and one metastasis may vary from another. Furthermore, the variable presence of tumor subpopulations, such as stem cells and dormant cells, may increase the complexity of the targeted treatments needed. Although molecular signatures and circulating biomarkers have been identified in breast cancer, there is lack of validated predictive molecular markers to optimize treatment choices for either prevention or treatment of metastatic disease. Finally, to maximize the information that can be obtained, increased attention to clinical trial design in the metastasis preventive setting is needed.

Biomarkers of residual disease, disseminated tumor cells, and metastases in the MMTV-PyMT breast cancer model

Cancer metastases arise in part from disseminated tumor cells originating from the primary tumor and from residual disease persisting after therapy. The identification of biomarkers on micro-metastases, disseminated tumors, and residual disease may yield novel tools for early detection and treatment of these disease states prior to their development into metastases and recurrent tumors. Here we describe the molecular profiling of disseminated tumor cells in lungs, lung metastases, and residual tumor cells in the MMTV-PyMT breast cancer model. MMTV-PyMT mice were bred with actin-GFP mice, and focal hyperplastic lesions from pubertal MMTV-PyMT;actin-GFP mice were orthotopically transplanted into FVB/n mice to track single tumor foci. Tumor-bearing mice were treated with TAC chemotherapy (docetaxel, doxorubicin, cyclophosphamide), and residual and relapsed tumor cells were sorted and profiled by mRNA microarray analysis. Data analysis revealed enrichment of the Jak/Stat pathway, Notch pathway, and epigenetic regulators in residual tumors. Stat1 was significantly up-regulated in a DNA-damage-resistant population of residual tumor cells, and a pre-existing Stat1 sub-population was identified in untreated tumors. Tumor cells from adenomas, carcinomas, lung disseminated tumor cells, and lung metastases were also sorted from MMTV-PyMT transplant mice and profiled by mRNA microarray. Whereas disseminated tumors cells appeared similar to carcinoma cells at the mRNA level, lung metastases were genotypically very different from disseminated cells and primary tumors. Lung metastases were enriched for a number of chromatin-modifying genes and stem cell-associated genes. Histone analysis of H3K4 and H3K9 suggested that lung metastases had been reprogrammed during malignant progression. These data identify novel biomarkers of residual tumor cells and disseminated tumor cells and implicate pathways that may mediate metastasis formation and tumor relapse after therapy.

Breast tumor cell detection at single cell resolution using an electrochemical impedance technique

Gold micro-electrodes with various diameters (25, 50, 75, 100 and 250 μm) were manufactured using standard micro-fabrication techniques and optimized for counting of MCF-7 cells (breast tumor cells) with single cell resolution. For specific cell capture, anti-EpCAM was immobilized on 11-mercaptoundecanoic acid (11-MUA)-3-mercaptopropionic acid (3-MPA) mixed self-assembled monolayer (SAM) modified gold surface of micro-electrodes. Electrodes were characterized using optical, cyclic voltammetry and electrochemical impedance spectroscopic (EIS) techniques. Cell capture response recorded using EIS suggested that optimum electrode dimensions should be analogous to desired cell size. For MCF-7 cells with an average diameter of 18 ± 2 μm, an electrode with 25 μm diameter was established as the optimum electrode size for precise single cell recognition and enumeration. In EIS investigation, the 25 μm electrode exhibited an impedance change of ~2.2 × 10(7) Ω in response to a single tumor cell captured on its surface. On the other hand other electrodes (250, 100, 75 and 50 μm) showed much less response for a single tumor cell. In future, the use of high density arrays of such electrodes with surface modifications will result in miniaturized lab on a chip devices for precise counting of MCF-7 cells with single cell resolution.

New insights into the mechanisms of organ-specific breast cancer metastasis

Despite the substantial advances obtained in the treatment of localized malignancies, metastatic disease still lacks effective treatment and remains the primary cause of cancer mortality, including in breast cancer. Thus, in order to improve the survival of cancer patients it is necessary to effectively improve prevention or treatment of metastasis. To achieve this goal, complementary strategies can be envisaged: the first one is the eradication of established metastases by adding novel modalities to current treatments, such as immunotherapy or targeted therapies. A second one is to prevent tumor cell dissemination to secondary organs by targeting specific steps governing the metastatic cascade and organ-specific tropism. A third one is to block the colonization of secondary organs and subsequent cancer cell growth by impinging on the ability of disseminated cancer cells to adapt to the novel microenvironment. To obtain optimal results it might be necessary to combine these strategies. The development of therapeutic approaches aimed at preventing dissemination and organ colonization requires a deeper understanding of the specific genetic events occurring in cancer cells and of the host responses that co-operate to promote metastasis formation. Recent developments in the field disclosed novel mechanisms of metastasis. In particular the crosstalk between disseminated cancer cells and the host microenvironment is emerging as a critical determinant of metastasis. The identification of tissue-specific signals involved in metastatic progression will open the way to new therapeutic strategies. Here, we will review recent progress in the field, with particular emphasis on the mechanisms of organ specific dissemination and colonization of breast cancer.

Unravelling the complexity of metastasis - molecular understanding and targeted therapies

Despite recognizing the devastating consequences of metastasis, we are not yet able to effectively treat cancer that has spread to vital organs. The inherent complexity of genomic alterations in late-stage cancers, coupled with numerous heterotypic interactions that occur between tumour and stromal cells, represent fundamental challenges in our quest to understand and control metastatic disease. The incorporation of genomic and other systems level approaches, as well as technological breakthroughs in imaging and animal modelling, have galvanized the effort to overcome gaps in our understanding of metastasis. Future research carries with it the potential to translate the wealth of new knowledge and conceptual advances into effective targeted therapies.

Pharmacogenomics and cancer stem cells: a changing landscape?

Pharmacogenomics in oncology holds the promise to personalize cancer therapy. However, its clinical application is still limited to a few genes, and, in the large majority of cancers, the correlation between genotype and clinical outcome has been disappointing. One possible explanation is that current pharmacogenomic studies do not take into account the emerging role of cancer stem cells (CSCs) in drug sensitivity and resistance. CSCs are a subpopulation of cells driven by specific signal-transduction pathways, but genetic variants affecting their activity are generally neglected in current pharmacogenomic studies. Moreover, in several malignancies, CSCs represent a rare sub-population; therefore, whole tumor profiling might mask CSC gene expression patterns. This article reviews current evidence on CSC chemoresistance and shows how common genetic variations in CSC-related genes may predict individual response to anti-cancer agents. Furthermore, we provide insights into the design of pharmacogenomic studies to address the clinical usefulness of CSC genetic profiling.

Circulating tumor cells and plasma DNA analysis in patients with indeterminate early or metastatic breast cancer

BACKGROUND

Circulating tumor cells (CTCs) and tumor-specific alterations in cell-free plasma DNA can both be used as markers of prognosis in breast cancer. To date, there have been no studies that have compared these as markers for subclinical metastases in the follow-up of early breast cancer. In this study, we measured CTCs and plasma DNA in a published group of patients with multiple pulmonary nodules and indeterminate metastatic disease.

PATIENTS & METHODS

A single blood sample for CTC and plasma DNA measurement was taken approximately 1.5 years after surgery from 19 women with histologically confirmed primary breast cancer and small pulmonary nodules. The CellSearch system was used to enrich and enumerate CTCs from peripheral blood. DNA was isolated from plasma and was analyzed by quantitative real-time PCR for DNA concentration, integrity and evidence of HER2 amplification.

RESULTS

Of the 19 individuals with 'indeterminate' early or metastatic breast cancer, 17 demonstrated no evidence of CTCs, one had one CTC and one had three CTCs. The mean plasma DNA concentration was low and within the range detected in healthy female controls, as were the values for DNA integrity. HER2 amplification was detected in the plasma DNA in four of the eight patients with HER2 immunohistochemistry 3+ tumors, but there was no overlap with the two CTC-positive patients. None of the patients have relapsed thus far (median follow-up: 3.5 years).

CONCLUSION

Both CTC and plasma DNA analyses together suggested that these patients had little evidence of metastatic disease. Future studies will be designed to assess the utility of these biomarkers in the follow-up of a larger number of women with breast cancer.

Biomarkers in cancer micrometastasis: where are we at?

Despite considerable advances in the field of solid tumors, disseminated malignancy remains the cause of the vast majority of cancer-related deaths. In patients with no overt metastasis, early spread of tumor cells is usually undetected by current imaging technologies. In addition, the metastatic process is complex and depends on multiple interactions (crosstalk) of disseminating tumor cells with the individual homeostatic mechanisms, which the tumor cells can usurp. Despite these many variables, a flurry of surrogate biomarkers to detect micrometastasis has been developed in the last decade. These biomarkers open avenues for understanding cancer dormancy and metastasis, have the potential to provide novel therapeutic targets and may help predict outcome and therapeutic decisions at diagnosis and during follow-up of cancer patients. This review focuses on ongoing efforts to unravel metastasis biology, surrogate biomarkers currently investigated to monitor micrometastasis and tools used to identify, quantify and determine their capacity to efficiently establish metastasis.

Primary breast cancer patients with high risk clinicopathologic features have high percentages of bone marrow epithelial cells with ALDH activity and CD44⁺CD24lo cancer stem cell phenotype

BACKGROUND

Cancer stem cells (CSCs) are purported to be epithelial tumour cells expressing CD44(+)CD24(lo) that exhibit aldehyde dehydrogenase activity (Aldefluor(+)). We hypothesised that if CSCs are responsible for tumour dissemination, disseminated cells in the bone marrow (BM) would be positive for putative breast CSC markers. Therefore, we assessed the presence of Aldefluor(+) epithelial (CD326(+)CD45(dim)) cells for the presence of the CD44(+)CD24(lo) phenotype in BM of patients with primary breast cancer (PBC).

METHODS

BM aspirates were collected at the time of surgery from 66 patients with PBC. Thirty patients received neoadjuvant chemotherapy (NACT) prior to aspiration. BM was analysed for Aldefluor(+) epithelial cells with or without CD44(+)CD24(lo) expression by flow cytometry. BM aspirates from three healthy donors (HD) were subjected to identical processing and analyses and served as controls.

RESULTS

Patients with triple-receptor-negative (TN) tumours had a significantly higher median percentage of CD44(+)CD24(lo) CSC within Aldefluor(+) epithelial cell population than patients with other immunohistochemical subtypes (P=0.018). Patients with TN tumours or with pN2 or higher pathologic nodal status were more likely to have a proportion of CD44(+)CD24(lo) CSC within Aldefluor(+) epithelial cell population above the highest level of HD. Furthermore, patients who received NACT were more likely to have percentages of Aldefluor(+) epithelial cells than the highest level of HD (P=0.004).

CONCLUSION

The percentage of CD44(+)CD24(lo) CSC in the BM is higher in PBC patients with high risk tumour features. The selection or enrichment of Aldefluor(+) epithelial cells by NACT may represent an opportunity to target these cells with novel therapies.

Breast cancer at bone metastatic sites: recent discoveries and treatment targets

Breast carcinoma is the most common cancer of women. Bones are often involved with breast carcinoma metastases with the resulting morbidity and reduced quality of life. Breast cancer cells arriving at bone tissues mount supportive microenvironment by recruiting and modulating the activity of several host tissue cell types including the specialized bone cells osteoblasts and osteoclasts. Pathologically activated osteoclasts produce osteolytic lesions associated with bone pain, pathological fractures, cord compression and other complications of metastatic breast carcinoma at bone. Over the last decade there has been enormous growth of knowledge in the field of osteoclasts biology both in the physiological state and in the tumor microenvironment. This knowledge allowed the development and implementation of several targeted therapeutics that expanded the armamentarium of the oncologists dealing with the metastases-associated osteolytic disease. While the interactions of cancer cells with resident bone cells at the established metastatic gross lesions are well-studied, the preclinical events that underlie the progression of disseminated tumor cells into micrometastases and then into clinically-overt macrometastases are just starting to be uncovered. In this review, we discuss the established information and the most recent discoveries in the pathogenesis of osteolytic metastases of breast cancer, as well as the corresponding investigational drugs that have been introduced into clinical development.

Micro- and nanotechnology approaches for capturing circulating tumor cells

Circulating tumor cells (CTC) are cells that have detached from primary tumors and circulate in the bloodstream where they are carried to other organs, leading to seeding of new tumors and metastases. CTC have been known to exist in the bloodstream for more than a century. With recent progress in the area of micro- and nanotechnology, it has been possible to adopt new approaches in CTC research. Microscale and nanoscale studies can throw some light on the time course of CTC appearance in blood and CTC overexpression profiles for cancer-related markers and galvanize the development of drugs to block metastases. CTC counts could serve as endpoint biomarkers and as prognostic markers for patients with a metastatic disease. This paper reviews some of the recent researches on using micro- and nanotechnology to capture and profile CTC.

Versatile label free biochip for the detection of circulating tumor cells from peripheral blood in cancer patients

The isolation of circulating tumor cells (CTCs) using microfluidics is attractive as the flow conditions can be accurately manipulated to achieve an efficient separation. CTCs are rare events within the peripheral blood of metastatic cancer patients which makes them hard to detect. The presence of CTCs is likely to indicate the severity of the disease and increasing evidences show its use for prognostic and treatment monitoring purposes. We demonstrated an effective separation using a microfluidic device to utilize the unique differences in size and deformability of cancer cells to blood cells. Using physical structures placed in the path of blood specimens in a microchannel, CTCs which are generally larger and stiffer are retained while most blood constituents are removed. The placements of the structures are optimized by computational analysis to enhance the isolation efficiency. With blood specimens from metastatic lung cancer patients, we confirmed the successful detection of CTCs. The operations for processing blood are straightforward and permit multiplexing of the microdevices to concurrently work with different samples. The microfluidic device is optically transparent which makes it simple to be integrated to existing laboratory microscopes and immunofluorescence staining can be done in situ to distinguish cancer cells from hematopoietic cells. This also minimizes the use of expensive staining reagents, given the small size of the microdevice. Identification of CTCs will aid in the detection of malignancy and disease stage as well as understanding the phenotypic and genotypic expressions of cancer cells.

New technologies for the detection of circulating tumour cells

The vast majority of cancer-related death is due to the metastatic spread of the primary tumour. Circulating tumour cells (CTC) are essential for establishing metastasis and their detection has long been considered as a possible tool to assess the aggressiveness of a given tumour and its potential of subsequent growth at distant organs. Conventional markers are not reliable in detecting occult metastasis and, for example, fail to identify approximately 40% of cancer patients in need of more aggressive or better adjusted therapies. Recent studies in metastatic breast cancer have shown that CTC detection can be used as a marker for overall survival and assessment of the therapeutic response. The benefits of CTC detection in early breast cancer and other solid tumours need further validation. Moreover, optimal CTC detection techniques are the subject of controversy as several lack reproducibility, sensitivity and/or specificity. Recent technical advances allow CTC detection and characterization at the single-cell level in the blood or in the bone marrow. Their reproducibility propels the use of CTC in cancer staging and real-time monitoring of systemic anticancer therapies in several large clinical trials. CTC assays are being integrated in large clinical trials to establish their potential in the management of cancer patients and improve our understanding of metastasis biology. This review will focus on the techniques currently used, the technical advancements made, the limitations of CTC detection and future perspectives in this field.

Long term survival following the detection of circulating tumour cells in head and neck squamous cell carcinoma

BACKGROUND

Techniques for detecting circulating tumor cells in the peripheral blood of patients with head and neck cancers may identify individuals likely to benefit from early systemic treatment.

METHODS

Reconstruction experiments were used to optimise immunomagnetic enrichment and RT-PCR detection of circulating tumor cells using four markers (ELF3, CK19, EGFR and EphB4). This method was then tested in a pilot study using samples from 16 patients with advanced head and neck carcinomas.

RESULTS

Seven patients were positive for circulating tumour cells both prior to and after surgery, 4 patients were positive prior to but not after surgery, 3 patients were positive after but not prior to surgery and 2 patients were negative. Two patients tested positive for circulating cells but there was no other evidence of tumor spread. Given this patient cohort had mostly advanced disease, as expected the detection of circulating tumour cells was not associated with significant differences in overall or disease free survival.

CONCLUSION

For the first time, we show that almost all patients with advanced head and neck cancers have circulating cells at the time of surgery. The clinical application of techniques for detection of spreading disease, such as the immunomagnetic enrichment RT-PCR analysis used in this study, should be explored further.

Found in transcription: gene expression and other novel blood biomarkers for the early detection of breast cancer

Early detection of a growing breast tumor is of key importance for patient survival. Despite limitations, mammography screening has improved the detection of breast tumors, however many tumors are not detected. This is especially true for younger women and women with high breast density. Novel diagnostic blood biomarkers either generated by the tumor and released into the blood, or generated by nontumor cells as a response to the tumor presence, can now potentially help improve the accuracy of early-stage breast cancer detection. They include multicomponent biomarkers, circulating tumor cells and RNA expression of peripheral blood. These novel biomarkers and their potential use will be presented and discussed in this review, with special emphasis on gene expression-based markers.

Identification of circulating tumour cells in early stage breast cancer patients using multi marker immunobead RT-PCR

Introduction

The ability to screen blood of early stage operable breast cancer patients for circulating tumour cells is of potential importance for identifying patients at risk of developing distant relapse. We present the results of a study of the efficacy of the immunobead RT-PCR method in identifying patients with circulating tumour cells.

Results

Immunomagnetic enrichment of circulating tumour cells followed by RT-PCR (immunobead RT-PCR) with a panel of five epithelial specific markers (ELF3, EPHB4, EGFR, MGB1 and TACSTD1) was used to screen for circulating tumour cells in the peripheral blood of 56 breast cancer patients.

Twenty patients were positive for two or more RT-PCR markers, including seven patients who were node negative by conventional techniques. Significant increases in the frequency of marker positivity was seen in lymph node positive patients, in patients with high grade tumours and in patients with lymphovascular invasion. A strong trend towards improved disease free survival was seen for marker negative patients although it did not reach significance (p = 0.08).

Conclusion

Multi-marker immunobead RT-PCR analysis of peripheral blood is a robust assay that is capable of detecting circulating tumour cells in early stage breast cancer patients.

Lobular phenotype related to occult-metastatic spread in axillary sentinel node and/or bone marrow in breast carcinoma

To determine whether any histological trait was associated with regional and/or systemic spread of occult tumour cells (OTCs) in small size invasive breast cancer, we compared tumour characteristics, axillary sentinel lymph node (SN) and bone marrow (BM) status in a series of 287 pT1T2 cases. Surgery was the first step of treatment, associated with SN procedure and with BM aspiration for the detection of OTC. SN was histologically classified as negative, metastatic (>2mm), micro-metastatic (>0.2mm and 2mm) or involved by OTC detected by immunohistochemistry (Ni+, 0.2mm). BM specimens were analysed after immunocytochemistry and classified as negative or positive with atypical cytokeratin-positive OTC. Metastasis and micro-metastasis in the SN were correlated with size, grade and vascular invasion. In contrast, presence of OTC in both SN and BM was independent of these parameters but positively associated with lobular type. This correlation was also observed for BM status, which was similarly independent of the tumour characteristics. No association was found between SN status and BM status. Our data indicate that, in the course of breast cancer, OTC spreading is frequent and could be an early event, related to lobular histological type but independent of classical histoprognostic parameters, and that the loco-regional metastatic spread of OTC is not a prerequisite for systemic involvement.

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.

Cancer micrometastasis and tumour dormancy

Many epithelial cancers carry a poor prognosis even after curative resection of early stage tumours. Tumour progression in these cancer patients has been attributed to the existence and persistence of disseminated tumour cells (DTC) in various body compartments as a sign of minimal residual disease. Bone marrow (BM) has been shown to be a common homing organ and reservoir for DTC. A significant correlation between the presence of DTC in BM and metastatic relapse has been reported in various tumour types. However, only a portion of patients with DTC in BM at primary surgery relapse. Thus far, little is known about the conditions required for the persistence of dormancy or the escape from the dormant phase into the active phase of metastasis formation. Thereby, this peculiar stage of conceivably balanced tumour cell division and death may last for decades in cancer patients. Most likely, the ability of a dormant DTC to "be activated" is a complex process involving (i) somatic aberrations in the tumour cells, (ii) the interaction of the DTC with the new microenvironment at the secondary site, and (iii) hereditary components of the host (i.e., cancer patient). In this review, we will summarize the key findings of research on micrometastatic cancer cells and discuss these findings in the context of the concept of tumour dormancy.

Cellular interactions in the vascular niche: implications in the regulation of tumor dormancy

Angiogenesis plays an established role in the promotion of growth of dormant micrometastasis, because blood vessels deliver oxygen and nutrients to the tumor microenvironment. In addition to this feeding function, however, there is accumulating evidence suggesting that endothelial cells-and perhaps other cellular components of the microenvironment--could communicate both positive and negative signals to tumor cells. This cross-talk between heterogeneous cell types could turn out to be important in the regulation of cancer cell behavior. Normal cells recruited during the angiogenic process, or attracted to future sites of metastasis by soluble products released by cancer cells, have been shown to create a niche favorable to tumor cell proliferation and survival. In addition, following an exogenous angiogenic spike, as may occur during inflammation, the same mechanisms could lead to re-activation of poorly angiogenic tumor cells seeded into tissues. In this review, we discuss the possible implications of this hypothesis for our understanding of the phenomenon of tumor dormancy.

Circulating tumor cell detection predicts early metastatic relapse after neoadjuvant chemotherapy in large operable and locally advanced breast cancer in a phase II randomized trial

PURPOSE

Circulating tumor cells in blood from metastatic breast cancer patients have been reported as a surrogate marker for tumor response and shorter survival. The aim of this study was to determine whether circulating tumor cells are present in the blood of patients with large operable or locally advanced breast cancer before neoadjuvant chemotherapy and after neoadjuvant chemotherapy before surgery.

EXPERIMENTAL DESIGN

Blood samples of 7.5 mL were obtained on CellSave tubes from patients included in a phase II trial (REMAGUS 02). Circulating tumor cells were immunomagnetically separated and fluorescently stained by the CellSearch system. Blood from 20 metastatic breast cancer patients was used as a positive control.

RESULTS

From October 2004 to July 2006, preneoadjuvant chemotherapy and/or postneoadjuvant chemotherapy blood samples were obtained from 118 patients. At least 1 circulating tumor cell was detected in 22 of 97 patients with preneoadjuvant chemotherapy samples (23%; 95% confidence interval, 15-31%; median, 2 cells; range, 1-17 cells). Circulating tumor cell positivity rates were 17% in 86 postneoadjuvant chemotherapy samples and 27% in all 118 patients. Persistence of circulating tumor cells at the end of neoadjuvant chemotherapy was not correlated with treatment response. After a short median follow-up of 18 months, the presence of circulating tumor cells (P=0.017), hormone receptor negativity, and large tumor size were independent prognostic factors for shorter distant metastasis-free survival.

CONCLUSION

Circulating tumor cells can be detected by the CellSearch system at a low cutoff of 1 cell in 27% of patients receiving neoadjuvant chemotherapy. Circulating tumor cell detection was not correlated to the primary tumor response but is an independent prognostic factor for early relapse.

Prognostic value of the molecular detection of circulating tumor cells using a multimarker reverse transcription-PCR assay for cytokeratin 19, mammaglobin A, and HER2 in early breast cancer

PURPOSE

To investigate the prognostic value of the molecular detection of circulating tumor cells (CTCs) using three markers [cytokeratin 19 (CK19), mammaglobin A (MGB1), and HER2] in early breast cancer.

EXPERIMENTAL DESIGN

CK19mRNA+, MGB1mRNA+, and HER2mRNA+ cells were detected using real-time (CK19) and nested (MGB1 and HER2) reverse transcription-PCR in the peripheral blood of 175 women with stage I to III breast cancer before the initiation of adjuvant chemotherapy. The detection of CTCs was correlated with clinical outcome. In 10 patients, immunofluorescence staining experiments were done to investigate the coexpression of cytokeratin, MGB1, and HER2 in CTCs.

RESULTS

CK19mRNA+, MGB1mRNA+, and HER2mRNA+ cells were detected in 41.1%, 8%, and 28.6% of the 175 patients, respectively. Patients had one of the following molecular profiles: CK19mRNA+/MGB1mRNA+/HER2mRNA+ (n = 8), CK19mRNA+/MGB1mRNA+/HER2mRNA- (n = 1), CK19mRNA+/MGB1mRNA-/HER2mRNA+ (n = 42), CK19mRNA+/MGB1mRNA-/HER2mRNA- (n = 21), CK19mRNA-/MGB1mRNA+/HER2mRNA- (n = 5), and CK19mRNA-/MGB1mRNA-/HER2mRNA- (n = 98). Double-immunofluorescence experiments confirmed the following CTC phenotypes: CK+/MGB1+, CK+/MGB1-, CK-/MGB1+, CK+/HER2+, CK+/HER2-, MGB1+/HER2-, and MGB1+/HER2+. In univariate analysis, the detection of CK19mRNA+, MGB1mRNA+, and HER2mRNA+ cells was associated with shorter disease-free survival (DFS; P < 0.001, P = 0.001, and P < 0.001, respectively), whereas the detection of CK19mRNA+ and MGB1mRNA+ cells was associated with worse overall survival (P = 0.044 and 0.034, respectively). In multivariate analysis, estrogen receptor-negative tumors and the detection of CK19mRNA+ and MGB1mRNA+ cells were independently associated with worse DFS.

CONCLUSION

The detection of peripheral blood CK19mRNA+ and MGB1mRNA+ cells before adjuvant chemotherapy predicts poor DFS in women with early breast cancer.

Review: Biological relevance of disseminated tumor cells in cancer patients

The prognosis of cancer patients is largely determined by the occurrence of distant metastases. In patients with primary tumors, this relapse is mainly due to clinically occult micrometastasis present in secondary organs at primary diagnosis but not detectable even with high resolution imaging procedures. Sensitive and specific immunocytochemical and molecular assays enable the detection and characterization of disseminated tumor cells (DTC) at the single cell level in bone marrow (BM) as the common homing site of DTC and circulating tumor cells (CTC) in peripheral blood. Because of the high variability of results in DTC and CTC detection, there is an urgent need for standardized methods. In this review, we will focus on BM and present currently available methods for the detection and characterization of DTC. Furthermore, we will discuss data on the biology of DTC and the clinical relevance of DTC detection. While the prognostic impact of DTC in BM has clearly been shown for primary breast cancer patients, less is known about the clinical relevance of DTC in patients with other carcinomas. Current findings suggest that DTC are capable to survive chemotherapy and persist in a dormant nonproliferating state over years. To what extent these DTC have stem cell properties is subject of ongoing investigations. Further characterization is required to understand the biology of DTC and to identify new targets for improved risk prevention and tailoring of therapy. Our review will focus on breast, colon, lung, and prostate cancer as the main tumor entities in Europe and the United States.

Cancer stem cells: markers or biomarkers?

INTRODUCTION

The lineages assumed by stem cells during hematopoiesis can be identified by the pattern of protein markers present on the surface of cells at different stages of differentiation. Specific antibodies directed at these markers have facilitated the isolation of hematopoietic stem cells by flow cytometry.

DISCUSSION

Similarly, stem cells in solid organs also can be identified using cell surface markers. In addition, solid tumors have recently been found to contain small proportions of cells that are capable of proliferation, self-renewal, and differentiation into the various cell types seen in the bulk tumor. Of particular concern, these tumor-initiating cells (termed cancer stem cells when multipotency and self-renewal have been demonstrated) often display characteristics of treatment resistance, particularly to ionizing radiation. Thus, it is important to be able to identify these cells in order to better understand the mechanisms of resistance, and to be able to predict outcome and response to treatment. This depends, of course, on identifying markers that can be used to identify the cells, and for some solid tumors, a specific pattern of cell surface markers is emerging. In breast cancer, for example, the tumor-initiating cells have a characteristic Lin(-)CD44(+)CD24(-/lo) ESA(+) antigenic pattern. In cells derived from some high-grade gliomas, expression of CD133 on the cell surface appears to select for a population of tumor-initiating, treatment resistant cells.

CONCLUSION

Because multiple markers, typically examined on single cells using flow cytometry, are used routinely to identify the subpopulation of tumor-initiating cells, and because the number of these cells is small, the challenge remains to detect them in clinical samples and to determine their ability to predict outcome and/or response to treatment, the hallmarks of established biomarkers.

Orthopedic surgery implications of breast cancer

Breast cancer is the most common malignancy and the second leading cause of death in women. The metastatic involvement of bone denotes disease progression and decreased survival. Controversy exists regarding the exact pathophysiologic mechanism of metastasis and the different pathways that determine an osteoblastic versus osteoclastic bone compromise. Several breakthrough advances in imaging techniques aid in the detection, staging and follow-up of bone metastases. Although usually responsive to hormonal therapy and pharmacologic interventions, skeletal metastases often require some type of surgical intervention. Orthopedic surgeons should establish an active role in the multidisciplinary treatment of patients with breast cancer.

Disseminated Tumor Cells of Breast Cancer Patients: A Strong Prognostic Factor for Distant and Local Relapse

Purpose: Clinical significance of disseminated tumor cells (DTC) in bone marrow of early breast cancer patients has been reported, but improvements in detection methods are needed.

Experimental Design: Bone marrow aspirates from 621 patients with stage I to III breast cancer were screened for cytokeratin-positive (CK+) cells. CK+ cells were categorized into DTC only if they had specific morphologic features of tumor cells. Bone marrow status and clinical and pathologic variables of the patients were correlated with clinical outcome after a median follow-up of 56 months.

Results: DTC and non-DTC CK+ cells were detected in 15% and 34% of patients, respectively, with no correlation with clinical and pathologic variables. On univariate analysis, DTC detection was associated with a poorer distant metastasis-free survival (DMFS; P = 0.0013) and overall survival (OS; P = 0.005). Moreover, DTC detection was also associated with local relapse-free survival (P = 0.0009). On multivariate analysis, DTC detection was an independent prognostic factor for DMFS, local relapse-free survival, and OS. There was no significant interaction between DTC detection and hormonal receptors status (P = 0.34). Non-DTC CK+ cells had no clinical significance.

Conclusion: DTC detection is a powerful prognostic marker for DMFS and OS in early breast cancer patients and can be individualized from irrelevant non-DTC CK+ cells by morphologic criteria. Biologically, despite high rates of systemic adjuvant therapy and locoregional irradiation in this series, DTC detection remains a prognostic factor of distant and, more strikingly, of local relapse, in favor of resistance to treatment of locally or distant disseminated cancer cells in DTC-positive patients.

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.

Expression of small breast epithelial mucin (SBEM) protein in tissue microarrays (TMAs) of primary invasive breast cancers

AIMS

Small breast epithelial mucin (SBEM) is a recently described gene product that shows promise as a new breast biomarker. The aim was to investigate for the first time SBEM protein expression in a large cohort (n = 300) of invasive breast cancers, its relationship to established clinical variables and its association with clinical outcome.

METHODS AND RESULTS

Immunohistochemical analysis was performed on tissue microarrays consisting of 149 oestrogen receptor (ER) alpha- and 151 ERalpha+ breast cancers. Overall, 18% of tumours were SBEM+ (n = 53/300). However, SBEM protein was more frequently observed in ER- (22%) than in ER+ cancers (13%; P = 0.049). A significant association with psoriasin/S100A7 expression (P < or = 0.0001) was observed in the entire cohort. SBEM was also positively associated with HER-2 (P = 0.046) in ER- cancers, and increased levels of SBEM were strongly associated with higher tumour grade (P = 0.0015). Furthermore, SBEM expression showed a trend towards an association with reduced overall survival and relapse-free survival in the ER+ cohort (P = 0.063 and P = 0.072, respectively).

CONCLUSIONS

Our results suggest that SBEM may identify a unique subset of breast cancers with poor prognosis and may have future implications for therapeutic management of this disease.