Interference of cytokeratin-20 and mammaglobin-reverse-transcriptase polymerase chain assays designed for the detection of disseminated cancer cells

Detection of Minimal Residual Disease in the Peripheral Blood of Breast Cancer Patients, with a Multi Marker (MGB-1, MGB-2, CK-19 and NY-BR-1) Assay

Purpose

Minimal residual disease (MRD) refers to micrometastases that are undetectable by conventional means and is a potential source of disease relapse. This study aimed to detect the presence of breast cancer (BC) biomarkers (MGB-1, MGB-2, CK-19, NY-BR-1) using real-time polymerase chain reaction (RT-PCR) in peripheral blood mononuclear cells (PBMC) of BC patients and the impact of a positive assay on clinical outcome.

Patients and Methods

Patients in the analysis included females >18 years of age with biopsy-proven carcinoma of the breast. A 10 mL sample of venous blood was obtained from 10 healthy controls and 25 breast cancer patients. Comparisons of peripheral blood markers were made with clinicopathological variables.

Results

High-quality RNA was extracted from all samples with a mean RNA concentration of 224.8±155.3 ng/µL. Each of the molecular markers examined was highly expressed in the primary breast tumors (n = 3, positive controls) with none of the markers detected in healthy negative controls. The NY-BR-1 marker was expressed in one (4%) patient with metastatic disease with no MGB-1 and MGB-2 detected in any sample derived from the study patients. The CK-19 marker was detected in 16 (64%) of the BC cases. No correlation was found between CK-19 expression and tumor stage (P = 0.07) or nodal status (P = 0.32). No correlation was identified in the BC patients between CK-19 expression and receptor status in the BC primary tumor.

Conclusion

This study showed high expression of all 4 markers NY-BR-1, MGB-1, MGB-2 and CK-19 in the PBMCs derived from breast cancer patients. CK-19 was detected in 64% of the stage I–III cases operated with curative intent, the only recurrent events occurring in the CK-19-positive cases. Our data confirm the need to enhance techniques for detection of MRD, which may better predict patients at risk for relapse.

Hybrid microfluidic sorting of rare cells based on high throughput inertial focusing and high accuracy acoustic manipulation

The ability to isolate rare circulating tumor cells (CTCs) from blood samples is essential to perform liquid biopsy as a routine diagnostic and prognostic test. Both label-free and surface biomarker-based cell sorting technologies have been developed to address the demand in high-integrity isolation of rare CTCs for cancer research. Label-free cell sorting mainly relies on the size difference between CTCs and blood cells; thus, it lacks sufficient sorting specificity. Surface biomarker-based cell sorting is highly specific; however, it requires expensive, labor-intensive, and time-consuming labeling due to the use of multiple sets of surface biomarkers. Because of the complex nature and high heterogeneity of tumorigenesis, it is difficult to rely on a single sorting process for high-integrity rare cell isolation. In this study, for the first time, we present a hybrid microfluidic cell sorting method combining high throughput size-dependent inertial focusing for size-based pre-enrichment and high accuracy fluorescence activated acoustic sorting for single cell isolation. After one single hybrid sorting process, we have demonstrated at least 2500-fold purity enrichment of MCF-7 breast cancer cells spiked in diluted whole blood samples with cell viability maintained at 91 ± 1% (viability before sorting was 94 ± 2%). This developed hybrid microfluidic cell sorting technique provides a promising solution for rare cell isolation needed in a variety of biological research and clinical applications.

The first example of integration of sized-based inertial sorting and surface biomarker-based acoustic sorting to achieve >2500-fold enrichment of rare cell populations.

Implications of cancer-associated systemic inflammation for biomarker studies

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

Diagnostic accuracy of small breast epithelial mucin mRNA as a marker for bone marrow micrometastasis in breast cancer: a pilot study

BACKGROUND

Detection of isolated tumour cells (ITC) in the blood or minimal deposits in distant organs such as bone marrow (BM) could be important to identify breast cancer patients at high risk of relapse or disease progression. PCR amplification of tissue or tumour selective mRNA is the most powerful analytical tool for detection of this micrometastasis. We have evaluated for the first time, the diagnostic accuracy of small breast epithelial mucin (SBEM) as a potential marker for BM micrometastasis in breast cancer.

METHODS

A nested RT-PCR assay for detection of SBEM mRNA was compared with immunocytochemistry (ICC) with anticytokeratin AE1/AE3 antibody in paired samples obtained from the BM of breast cancer patients. Associations of SBEM mRNA detection in BM and clinical and pathological parameters were evaluated. SBEM mRNA status and time to breast cancer progression were analysed using Kaplan-Meyer curves.

RESULTS

Fifty stages I-IV breast cancer female patients were prospectively included in our study. SBEM specific transcript was found in BM in 26% of the patients. Detection rate was similar to the percentage of patients with ITCs detected using ICC (24%). SBEM mRNA in BM aspirates were significantly associated with presence of clinically active disease, including locally advanced and metastatic patients (47%, P = 0.021) and tumours with positive hormonal receptors (36.7%, P = 0.035). In addition association with Her2/neu over-expression (44.4%, P = 0.051) and low proliferating tumours (36%, P = 0.067) were close to significant levels. When we analysed time to breast cancer progression adjusting for grade or hormone receptor status, presence of SBEM mRNA in BM defines distinct prognostic groups.

CONCLUSIONS

SBEM might represent a suitable marker for molecular detection of ITCs in BM in breast cancer patients. Analysis of prognostic value for SBEM mRNA-based assay should take into account the heterogeneity and different molecular subtypes of breast cancer.

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.

DETECTION OF DISSEMINATED TUMOR CELLS IN PERIPHERAL BLOOD

Metastases are the major cause of cancer-related deaths in patients with solid epithelial malignancies, such as breast, colorectal and prostate carcinomas. Hematogenous spreading of tumor cells from a primary tumor can be considered as a crucial step in the metastasis cascade leading eventually to the formation of clinically manifest metastases. Consequently, as shown in recent studies, the detection of disseminated tumor cells in peripheral blood might be of clinical relevance with respect to individual patient prognosis and staging or monitoring of therapy. However, the rarity of disseminated tumor cells in peripheral blood renders the application of sensitive techniques mandatory for their detection. The emergence of highly sophisticated reverse transciptase-polymerase chain reaction (RT-PCR) assays, combining a preanalytical enrichment step with the assessment of multiple molecular tumor markers expressed in disseminated tumor cells, provides a powerful tool in detecting disseminated tumor cells with high sensitivity and specificity. This review will discuss currently used tumor markers as well as experimental means to enhance the sensitivity and specificity of RT-PCR assays to detect disseminated tumor cells in the peripheral blood of patients with breast, colorectal, and prostate cancers, and their clinical relevance assessed in recent studies.

Quantitation of circulating tumor cells in blood samples from ovarian and prostate cancer patients using tumor-specific fluorescent ligands

Quantitation of circulating tumor cells (CTCs) can provide information on the stage of a malignancy, onset of disease progression and response to therapy. In an effort to more accurately quantitate CTCs, we have synthesized fluorescent conjugates of 2 high-affinity tumor-specific ligands (folate-AlexaFluor 488 and DUPA-FITC) that bind tumor cells >20-fold more efficiently than fluorescent antibodies. Here we determine whether these tumor-specific dyes can be exploited for quantitation of CTCs in peripheral blood samples from cancer patients. A CTC-enriched fraction was isolated from the peripheral blood of ovarian and prostate cancer patients by an optimized density gradient centrifugation protocol and labeled with the aforementioned fluorescent ligands. CTCs were then quantitated by flow cytometry. CTCs were detected in 18 of 20 ovarian cancer patients (mean 222 CTCs/ml; median 15 CTCs/ml; maximum 3,118 CTCs/ml), whereas CTC numbers in 16 gender-matched normal volunteers were negligible (mean 0.4 CTCs/ml; median 0.3 CTCs/ml; maximum 1.5 CTCs/ml; p < 0.001, chi(2)). CTCs were also detected in 10 of 13 prostate cancer patients (mean 26 CTCs/ml, median 14 CTCs/ml, maximum 94 CTCs/ml) but not in 18 gender-matched healthy donors (mean 0.8 CTCs/ml, median 1, maximum 3 CTC/ml; p < 0.0026, chi(2)). Tumor-specific fluorescent antibodies were much less efficient in quantitating CTCs because of their lower CTC labeling efficiency. Use of tumor-specific fluorescent ligands to label CTCs in peripheral blood can provide a simple, accurate and sensitive method for determining the number of cancer cells circulating in the bloodstream.

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.

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

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

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

Marker genes, commonly used to detect circulating tumour cells in RT-PCR-based tests: squamous-cell carcinoma antigen, epidermal growth factor receptor, mammaglobin, small breast epithelial mucin, but not carbonic anhydrase 9, were shown to be expressed in normal, mitogen-stimulated peripheral blood mononuclear cells (PBMNC). Thus, considering the inflammatory reactions often accompanying cancer development, to reduce false-positive results of the metastatic tumour cell tests, molecular markers should be validated not against normal peripheral blood, but against activated lymphoid cells, such as in vitro mitogen-stimulated PBMNC.

Effect of different cytokines on mammaglobin and maspin gene expression in normal leukocytes: possible relevance to the assays for the detection of micrometastatic breast cancer

In cancer patients, the ability to detect disseminated tumour cells in peripheral blood or bone marrow could improve prognosis and consent both early detection of metastatic disease and monitoring of the efficacy of systemic therapy. These objectives remain elusive mainly due to the lack of specific genetic markers for solid tumours. The use of surrogate tissue-specific markers can reduce the specificity of the assays and give rise to a clinically unacceptable false-positive rate. Mammaglobin (MAM) and maspin are two putative breast tissue-specific markers frequently used for detection of occult tumour cells in the peripheral blood, bone marrow and lymph nodes of breast cancer patients. In this study, it was evaluated whether MAM and maspin gene expression may be induced in the normal blood and bone marrow cells exposed to a panel of cytokines, including chemotactic factors (C5a, interleukin (IL)-8), LPS, proinflammatory cytokines (TNF-α, IL-1β) and growth factors (IL-3, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor). The experimental data show that all cytokines included in the panel, except for IL-8, were able to induce maspin expression; on the contrary, MAM gene was never induced. These results suggest that MAM is more specific than maspin and that the possible interference of cytokines should be taken into account in interpreting molecular assays for detection of isolated tumour cells.

Mammaglobin: a candidate diagnostic marker for breast cancer

Mammaglobin, known for its mammary tissue specificity, has been discussed as a promising diagnostic marker in breast cancer for almost 10 years. In particular, the application of mammaglobin RT-PCR to detect disseminated breast cancer cells has been reported. More than 25 publications evaluate the detection of mammaglobin mRNA in lymph node, blood, and bone marrow specimens of breast cancer patients. Recently, structural details about the mammaglobin complex have been discovered, and these findings can be implemented to optimize detection of the secreted protein. This review summarizes the findings of almost 50 published studies and the current knowledge about the diagnostic utility of mammaglobin.

Detection of disseminated epithelial cancer cells by liquid culture--factors interfering with the standardization of assays

BACKGROUND

Immunocytochemistry is the standard method for detection of disseminated breast-cancer cells. Tumor-cell enrichment by cell culture has been used by several investigators, however assays published have not been well-standardized.

METHODS

Breast-cancer cells from two lines were diluted in hemopoietic cells of varying origins and cultured in different media and different flasks. Factors influencing successful tumor-cell amplification by liquid culture were identified by investigation of 277 cultures. Parallel clinical samples, consisting of BM aspirations, leukapheresis samples and peripheral blood samples obtained from women with breast cancer, were investigated in 113 cultures. Cancer-cell detection by cell culture could be compared to immunocytochemistry in 101 cases.

RESULTS

The frequency of tumor-cell detection was not improved by liquid culture, but a significant correlation between conventional tumor-cell detection and detection after liquid culture was found. Factors influencing tumor-cell amplification in the dilution assay could not be transferred to the investigation of clinical samples. It was concluded that culture-enrichment of disseminated cancer cells was very complex, and could be influenced by a variety of factors-even when a model system was used.

DISCUSSION

It should be recognized that culture-enriched cancer cells probably represent a highly selected population of disseminated cancer cells, despite the significant correlation between tumor cells detected by conventional methods and following conventional methods after liquid culture. There is currently no evidence to suggest that cancer-cell amplification by cell culture could become a standardized technique for the detection of disseminated epithelial tumor cells.

Combination of cytology, fluorescence in situ hybridization for aneuploidy, and reverse-transcriptase polymerase chain reaction for human mammaglobin/mammaglobin B expression improves diagnosis of malignant effusions

PURPOSE

The identification of malignant cells in effusions by conventional cytology is hampered by its limited sensitivity. The aim of this study was to improve tumor cell detection in effusions by molecular approaches.

MATERIALS AND METHODS

A total of 157 effusions from patients with tumors and 72 effusions from patients without a history or evidence of malignancy were included in this study. All effusion specimens were evaluated in parallel by cytology, fluorescence in situ hybridization (FISH) for aneuploidy, and reverse-transcriptase polymerase chain reaction (RT-PCR) for expression of human mammaglobin (hMAM) and mammaglobin B (hMAM-B).

RESULTS

In effusions from patients with tumors, the sensitivities of tumor cell detection by cytology, FISH, and hMAM and hMAM-B detection were 46.2%, 53.3%, 36.4%, and 57.7%, respectively. The corresponding specificities were 94.4%, 97.0%, 87.1%, and 88.6%. Notably, a high percentage of effusions containing malignant cells were in fact transudates, indicating the necessity for molecular diagnostic work-up of transudates collected from patients with tumors. Dependent on the tumor type, the use of appropriate marker combinations improved tumor cell detection in effusions significantly. By combining all four diagnostic tests, a positive test result indicating the presence of malignancy was achieved in 81.1%, with a fairly good specificity of 70.1%.

CONCLUSION

Molecular techniques are definitely useful to detect malignancy in cytologically negative effusions. Tumor cell detection in effusions can be significantly improved by FISH and PCR techniques applying appropriate molecular markers. This finding should help to improve tumor staging, prognostic assessment, and treatment monitoring.

Mammaglobin Expression in Lymph Nodes Is an Important Marker of Metastatic Breast Carcinoma

Context.—Organ specificity is a desirable property of a tumor marker, especially in metastatic adenocarcinomas of unknown primary origin. Mammaglobin, a mammary-specific member of the uteroglobin family, is known to be overexpressed in human breast cancer.

Objective.—We investigated mammaglobin A expression in metastatic carcinomas of lymph nodes from the breast and various other organs and its usefulness in identifying metastatic carcinoma of the breast. For comparative purposes, we also investigated BRST-1 and BRST-2 expression.

Design.—We produced recombinant mammaglobin and polyclonal antimammaglobin antibodies. Mammaglobin expression was analyzed by immunohistochemical staining using a tissue microarray and by reverse transcription–polymerase chain reaction in 210 carcinomas, including those of the breast (n = 70), lung (n = 30), stomach (n = 30), colorectum (n = 25), hepatobiliary tract (n = 20), urinary tract (n = 10), thyroid gland (n = 10), ovary and endometrium (n = 10), and salivary gland (n = 5).

Results.—Mammaglobin expression was observed in 59 cases (84.3%) of breast cancer and in 21 cases (15.0%) of nonbreast cancer. The BRST-1 and BRST-2 expression rates were 75.7% and 44.3% in breast cancer and 26.4% and 2.1% in nonbreast cancer, respectively. Mammaglobin is superior to BRST-1 for both specificity and sensitivity and is superior to BRST-2 for sensitivity.

Conclusion.—Our data suggest that mammaglobin is one of the first relatively mammary-specific and mammary-sensitive markers. Mammaglobin and BRST-2 appear to represent useful markers for breast cancer and should be used as a component of panels evaluating tumors of unknown primary sites.

A novel method for increasing the expression level of recombinant proteins

Expression of recombinant proteins is an important step towards elucidating the functions of many genes discovered through genomic sequencing projects. It is also critical for validating gene targets and for developing effective therapies for many diseases. Here we describe a novel method to express recombinant proteins that are extremely difficult to produce otherwise. The increased protein expression level is achieved by using a fusion partner, MTB32-C, which is the carboxyl terminal fragment of the Mycobacterium tuberculosis antigen, MTB32 (Rv0125). By fusing MTB32-C to the N-termini of target genes, we have demonstrated significant enhancement of recombinant protein expression level in Escherichia coli. The inclusion of a 6xHis tag and the 128-amino acid of MTB32-C will add 13.5 kDa to the fusion molecule. Comparison of the mRNA levels of the fusion and non-fusion proteins indicated that the increased fusion protein expression may be regulated at translational or post-translational steps. There are many potential applications for the generated fusion proteins. For example, MTB32-C fusion proteins have been used successfully as immunogens to generate both polyclonal and monoclonal antibodies. These antibodies have been used to characterize cellular localization of the proteins and to validate gene targets at protein level. In addition, these antibodies may be useful in diagnostic and therapeutic applications for many diseases. If desired, the MTB32-C portion in the fusion protein can be removed after protein expression, making it possible to study protein structure and function as well as to screen for potential drugs. Thus, this novel fusion expression system has become a powerful tool for many applications.

Mammaglobin expression in gynecologic malignancies and malignant effusions detected by nested reverse transcriptase-polymerase chain reaction

The detection of micrometastatic disease remains a challenge for the diagnosis and monitoring of malignant disease. RT-PCR for human mammaglobin (hMAM) was recently shown to provide a sensitive method for assessing circulating breast cancer cells in peripheral blood. This study was aimed at investigating hMAM expression in normal and malignant tissue from the female genital tract and the prostate as well as in malignant effusions derived from gynecologic malignancies. hMAM expression was analyzed with nested RT-PCR in 152 samples of normal (n = 73) and malignant epithelial tissues (n = 79) and in 33 specimens of various normal mesenchymal tissue types. We found hMAM expression was not restricted to the normal mammary gland and breast carcinoma but was also detectable in most specimens of benign and malignant epithelial tissue from the ovary (97% versus 95%), uterus (both 100%), and cervix (91% versus 90%). Notably, hMAM expression was also found in benign prostatic hyperplasia (45%) and in prostate cancer (55%). A much lower expression rate was found in various normal and benign mesenchymal tissues (12%). In keeping with our previous data, hMAM expression was absent in all control samples (n = 124) of peripheral blood and bone marrow from healthy volunteers and patients with hematologic malignancies. In pleural or peritoneal effusions (n = 42) from patients with carcinomas of the breast, endometrium, or ovary, hMAM positivity was noticed in the majority of cases (74%), whereas only 52% of the specimens were cytologically positive for tumor cells. In conclusion, hMAM expression assessed by nested RT-PCR is a sensitive molecular marker for detecting micrometastatic tumor spread into pleural effusions and ascites from patients with breast cancer and various other gynecologic neoplasms.