Melanoma Cells In Peripheral Blood Research Articles

Abstract 384: Detection of circulating melanoma cells in paired arterial and venous specimens from uveal melanoma patients with hepatic metastatic

Abstract Background: Circulating tumor cells (CTCs) represent a surrogate biomarker for hematogenous metastases. The detection of CTCs has gained increasing interest for prediction of clinical outcome. However, it remains to be determined whether uveal melanoma cells circulating in a peripheral vein predict systemic recurrence and poorer overall prognosis. Uveal melanoma, the most common primary cancer of the eye in adults, is unique in that the uveal tract is devoid of lymphatics. Since systemic recurrence develops exclusively via hematogenous spread, patients with uveal melanomas present a special opportunity to explore the prognostic potential of CTCs. Although the lung is the first organ through which venous drainage from the affected eye passes and indeed the only organ through which all venous blood must pass, 80-95% of systemic metastases are found first in the liver without development of lung metastases. To address these issues, we investigated the numbers of CTCs in paired arterial (femoral) and venous (antecubital) blood specimens obtained from uveal melanoma patients with hepatic metastases. Methods: CTCs in blood specimens were measured in 17 uveal melanoma patients with multiple hepatic metastases, including 10 patients with liver-only metastases and 7 patients with hepatic and extra-hepatic metastases. Peripheral arterial and venous blood specimens were collected at the same time prior to liver directed treatment. CTCs were analyzed using CellTracks Circulating melanoma Cell Kit by CellSearch System. The clinical information and sources of blood specimens were blinded when CTCs were analyzed. Result: CTCs were detectable from all 17 arterial blood specimens (100%) (median 5, range 1 to 168). In contrast, much smaller numbers of CTCs were detectable in 52.9% (9/17) of venous blood specimens (median 1, range 0 to 8) from the same patients. In terms of degree of tumor burden, patients who have hepatic as well as extra-hepatic metastasis showed higher numbers of arterial CTCs (median 12, range 5 to 168), compared to patients who have liver-only metastasis (median 4, range 1 to 11). More importantly, there is no significant correlation between numbers of arterial CTCs and the degree of tumor volume in the liver in patients who have liver-only metastases. Conclusions: Using this technology, the detection of uveal melanoma cells in peripheral blood is feasible. Peripheral capillary beds effectively filter CTCs from venous blood; thus venous blood might not be the best source for measurement of CTCs in patients with metastatic uveal melanoma. The paucity of clinically evident non-hepatic metastases despite the effective filtration by peripheral capillary beds remains unexplained and may be a demonstration of the “seed and soil” hypothesis. CTCs are a non-invasive source of uveal melanoma cells for evaluating tumor biology. Further investigation is warranted. Citation Format: Mizue Terai, Zhaomei Mu, David Eschelman, Carin Gonsalves, Ken Kageyama, Michael J. Mastrangelo, Marlana Orloff, Ryan Weight, Massimo Cristofanilli, Takami Sato. Detection of circulating melanoma cells in paired arterial and venous specimens from uveal melanoma patients with hepatic metastatic. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 384. doi:10.1158/1538-7445.AM2015-384

Expression of the Stem Cell Markers Nestin and CD133 on Circulating Melanoma Cells

Different molecular markers have been identified for melanoma-initiating cells including CD133 and nestin. Assuming that metastasis requires a dissemination of tumor-initiating cells, presence of circulating tumor-initiating cells should be associated with worse patient outcome. In this study, 20 ml blood was collected from 32 consecutive patients affected by metastatic melanoma and blood was enriched for circulating melanoma cells (CMCs) by CD45 depletion of the non-melanoma cell fraction. Multiparameter cytometry was carried out to co-stain with combinations of CD133 and nestin (NES). Six tissue samples from metastatic lesions of six different patients were stained with the same antibodies by immunohistochemistry. Percentage of NES-positive CMCs correlated with tumor burden and number of metastatic sites. Cox regression analysis revealed levels of lactate dehydrogenase (LDH; hazard ratio: 12.8 (1.35-121.5); P=0.02), number of metastatic sites (hazard ratio 3.87 (1.66-9.03); P=0.02), tumor burden (hazard ratio 5.72 (1.57-20.9); P=0.01), and percentage of NES-expressing CMCs ≥ 35% (hazard ratio 5.73 (1.66-19.7); P=0.006) to be factors related to shorter overall survival. CD133- and NES-expression profiles on CMCs were similar to matched metastatic tissue. These findings show that CMCs expressed stem cell-associated markers NES and CD133. Higher expression of NES on CMCs might represent an index of poor prognosis.

Correlation of stem cell marker nestin expression on circulating melanoma cells with extension of disease and survival.

8551 Background: Within circulating melanoma cells (CMCs) there may be a subset of cells with stem cell characteristics able to develop distant metastasis. We evaluated the presence of melanoma cells bearing stem cell phenotype in the bloodstream of patients (pts) with metastatic melanoma. Stem cell marker assessment included nestin (NES) and CD133. Methods: Twenty-five ml blood were collected after informed consent from 32 consecutive pts affected by metastatic uveal (n = 14) or cutaneous (n = 18) melanoma and from (n = 6) healthy volunteers according to ethically approved protocols. Blood was enriched for tumour cells by CD45 depletion of the non-melanoma cell fraction using a magnetic bead separation technique. Potential melanoma cells were identified using flow cytometry with the markers MELAN-A and HMB45. Multiparameter cytometry was carried out to co-stain with the combinations of CD133 and NES. Five tissue samples from metastatic lesions of five different pts were stained with the same antibodies by immunohistochemistry. Results: No cells positive for the melanocyte markers were detected in blood from volunteers. In pts MELANA and/or HMB45 positive cells were detected in 28 samples (87.5%). The absolute number of melanoma cells ranged from 0 to 1233 (median 53) per 10 mL of blood. NES expressing cells were more represented compared to CD133 expressing cells (median 18.0% [0.3%-85.1%] vs. median 0.1% [0%-23.4%]). Percentage of NES-positive cells correlated significantly with tumor burden (p = 0.01) and number of metastatic sites (p = 0.03), whereas percentage of CD133-positive cells and absolute total number of cells did not. Cox regression analysis revealed levels of LDH (HR: 12.8 [1.35-121.5]; p = 0.02), number of metastatic sites (HR 3.87 [1.66-9.03]; p = 0.02), tumor burden (HR 5.72 [1.57- 20.9]; p = 0.01) and high level of NES expression (HR 3.5 [0.92-13.6]; p = 0.04) to be factors related to shorter overall survival. CD133 and NES expression profiles on CMCs and in matched metastatic tissue were similar. Conclusions: Melanoma cells in peripheral blood expressed stem cell associated markers NES and CD133. Higher expression of NES on CMCs might represent an index of poor prognosis. No significant financial relationships to disclose.

Circulating melanoma cells and distant metastasis-free survival in stage III melanoma patients with or without adjuvant interferon treatment (EORTC 18991 side study)

Aim To evaluate the prognostic and predictive importance of detection of melanoma cells in peripheral blood using reverse transcriptase polymerase chain reaction (RT-PCR) in stage III cutaneous melanoma patients after sentinel or regional lymph node dissection. Patients and methods Serial testing for tyrosinase and Mart-1/Melan-A transcripts in peripheral blood was performed every 6 months over a maximum period of 60 months in a subset of patients enrolled in EORTC 18991 phase 3 trial, comparing pegylated interferon-α-2b with observation. Univariate and multivariate analyses were performed to estimate the role of RT-PCR as prognostic and predictive factor for distant metastasis-free survival (DMFS). Results Among 299 patients who underwent RT-PCR analyses, 109 (36.5%) had at least one positive sample, either at time of randomisation ( N = 17) or subsequently ( N = 92). The cumulative rate of positive results was similar in the two treatment groups, as the DMFS from first RT-PCR positivity. RT-PCR result, positive versus negative, at a given time point, had no prognostic impact on subsequent DMFS. Cox time-dependent analysis indicated a significantly higher risk of developing distant metastasis in patients with a positive sample as compared to those with a negative one: hazard ratio (HR) of 2.23 (95% confidence interval (CI), 1.40–3.55; p < .001). These results were comparable in the 2 treatment groups, indicating that RT-PCR assessment was not predictive for treatment outcome. Conclusion Detection of circulating tumour cells by RT-PCR for tyrosinase and Mart-1/Melan-A was a time-dependent moderate prognostic factor for subsequent development of distant metastasis in stage III melanoma patients.

Circulating melanoma cells in peripheral blood of patients with uveal melanoma before and after different therapies and association with prognostic parameters: a pilot study

To evaluate whether tumour therapy for malignant uveal melanoma leads to a shedding of melanoma cells into the systemic circulation. Ninety-four peripheral blood samples from 81 patients with malignant uveal melanoma were collected before and after different tumour therapies and the number of circulating melanoma cells (CMCs) was investigated (seven patients with enucleation, 49 patients with stereotactic radiotherapy, 19 patients with endoresection of the tumour, 15 patients with ruthenium-brachytherapy and four patients with transpupillary thermotherapy). A cellular approach was used to detect CMCs through an immunocytological assay with tumour cell enrichment by immunomagnetic cell sorting. The number of CMCs was analysed further according to specific patient characteristics, tumour parameters and the development of metastasis. There was no significant difference between the number of CMCs before and after the different therapies (p = 0.78). There was also no significant association between established prognostic parameters of primary uveal melanoma and the detection of CMCs (all p >0.05). The number of CMCs was not related to the development of metastasis in a short median follow-up time of 16 months (p > 0.05). No changes in CMC values were observed before and after different tumour therapies. In the majority of cases therapy does not lead to a shedding of detectable melanoma cells into the systemic circulation.

Expression of stem cell markers in circulating melanoma cells

e22056 Background: Within circulating tumor cells there may be a subset of cell with stem cell (tumor initiating) characteristics able to develop distant metastasis. Several markers including nestin and CD133 have been found to be possible candidates to identify such a kind of subpopulation in other experimental models. We evaluated the presence of melanoma cells bearing stem cell phenotype in the bloodstream of patients with cutaneous or uveal melanoma after depletion of the leukocytes fraction. Methods: Between 50 and 100 ml of peripheral blood were collected from 12 melanoma patients with various tumor burden as well as three healthy volunteers. Blood samples were enriched for tumour cells by CD45 depletion of the leukocyte fraction using magnetic beads separation (EasySep, Stem Cell Technologies. Inc.). The remaining material was stained with antibodies for the markers Melan-A/Mart-1 (Dako) and HMB45 (Dako), CD133 (Miltenyi Biotec) and nestin (R&amp;D System) and analysed by flow cytometry (BD FACSCalibur). Ten ml of blood were further processed and CD133, nestin, Melan-A/Mart-1 transcripts were quantified by Real Time RT-PCR (LightCycler, Roche Diagnostic). Results: CD45-depleted fractions in healthy controls were negative for melanoma markers. Melan-A/Mart-1 and/or HMB45 positive cells were detectable in 11 out of 12 melanoma patients. The absolute number of melanoma cells identified ranged from 6 to 176 per 10 ml of blood. Nestin expressing cells were more represented compared to CD133 expressing cells (median 27.4%, range 0.3% to 65.1% vs. median 9.3%, range 0.1% to 16.8%) within the melanoma fraction of cells positive for Melan-A/Mart-1 and/or HMB45. In one patient two different melanoma cell populations were detectable. The population of cells with lower expression of the melanoma markers showed at the same time higher expression of nestin and CD133 (5.9% vs. 1.3% and 10.2% vs. 6.7% respectively). Nestin results were in good accordance to the FACS data (nestin: r=0.55; CD133: r=0.23; Pearson test). Conclusions: The novel negative separation technique allows reliable isolation of melanoma cells from peripheral blood of patients with metastatic disease. A significant fraction of melanoma cells in peripheral blood bears a stem cell phenotype. No significant financial relationships to disclose.

Visualization of Circulating Melanoma Cells in Peripheral Blood of Patients with Primary Uveal Melanoma

In patients with uveal melanoma, tumor cell dissemination and subsequent formation of metastases are confined mainly to the hematogenous route. Here, we sought to isolate circulating melanoma cells in peripheral blood of patients with primary uveal melanoma and clinically localized disease. Blood samples from 52 patients with clinically localized uveal melanoma and from 20 control individuals were prospectively collected before therapy of the primary tumor. Tumor cells expressing the melanoma-associated chondroitin sulfate proteoglycan were enriched by immunomagnetic cell sorting and visualized by immunocytologic staining. Results were compared with clinical data at presentation. In 10 of 52 patients [19%; 95% confidence interval (95% CI), 10-33%], between 1 and 5 circulating melanoma cells were detected in 50 mL peripheral blood. No melanoma-associated chondroitin sulfate proteoglycan-positive cells were detected in any of the 20 controls examined. The presence of tumor cells in peripheral blood was associated with ciliary body invasion [odds ratio (OR), 20.0; 95% CI, 3.0-131.7], advanced local tumor stage (OR, 6.7; 95% CI, 1.8-25.4), and anterior tumor localization (OR, 4.0; 95% CI, 1.2-12.7), all established factors for uveal melanoma progression. Immunomagnetic enrichment enables detection of intact melanoma cells in peripheral blood of patients with clinically localized ocular disease. Visualization and capturing of these cells provide a unique tool for characterizing potentially metastasizing tumor cells from a primary melanoma at an early stage of the disease.

Multimarker real‐time reverse transcription‐PCR for quantitative detection of melanoma‐associated antigens: a novel possible staging method

Detection of melanoma cells in peripheral blood is a promising method for monitoring haematogenous spread of melanoma cells. It enables us to detect early metastasis and to better stratify candidates for adjuvant immunotherapy. Inconsistent data on the sensitivity and clinical relevance of this method have been reported. We developed a multimarker real-time reverse transcription-PCR (RT-PCR) for quantification of five melanoma markers: Melan-A, gp100, MAGE-3, MIA and tyrosinase. In this prospective study, 65 patients with resected cutaneous melanoma stage IIB-III were screened. Peripheral blood samples were collected every 3 months for the following 18 months, and circulating melanoma cells were examined and compared with clinical staging results. Eighteen patients relapsed during the trial and showed different types of melanoma progression. All these patients experienced statistically significant tumour marker elevation in the period from 0 to 9 months before the disease progression. MAGE-3 was the most sensitive progression marker. In patients with progression, we observed three concordant positive markers in 39% of cases, two concordant positive markers in 28%, and finally one marker in 33%. This report describes a multiple-marker real-time RT-PCR, which is able to provide quantitative data on melanoma markers in the peripheral blood of melanoma patients. Measurement of the studied molecular markers in our hands represents a prognostic factor and a useful method for early detection of metastasis and treatment response of melanoma patients.

Issues affecting molecular staging in the management of patients with melanoma

Prediction of metastatic potential remains one of the main goals to be pursued in order to better assess the risk subgroups of patients with melanoma. Detection of occult melanoma cells in peripheral blood (circulating metastatic cells [CMC]) or in sentinel lymph nodes (sentinel node metastatic cells [SNMC]), could significantly contribute to better predict survival in melanoma patients. An overview of the numerous published studies indicate the existence of several drawbacks about either the reliability of the approaches for identification of occult melanoma cells or the clinical value of CMC and SNMC as prognostic factors among melanoma patients. In this sense, characterization of the molecular mechanisms involved in development and progression of melanoma (referred to as melanomagenesis) could contribute to better classify the different subsets of melanoma patients. Increasing evidence suggest that melanoma develops as a result of accumulated abnormalities in genetic pathways within the melanocytic lineage. The different molecular mechanisms may have separate roles or cooperate during all evolutionary phases of melanocytic tumourigenesis, generating different subsets of melanoma patients with distinct aggressiveness, clinical behaviour, and response to therapy. All these features associated with either the dissemination of occult metastatic cells or the melanomagenesis might be useful to adequately manage the melanoma patients with different prognosis as well as to better address the different melanoma subsets toward more appropriate therapeutic approaches.

Traditional urinary cytology and tyrosinase RT-PCR in metastatic melanoma patients: correlation with clinical status

Background:The finding of a suspicious urinary cytology is not uncommon in melanoma patients, in as much as morphology alone is often unable to distinguish the variable cytological features of melanoma...

Circulating Tyrosinase and MART-1 mRNA does not Independently Predict Relapse or Survival in Patients with AJCC Stage I–II Melanoma

The detection of melanoma cells in peripheral blood has been proposed to select patients with a high risk of relapse. In this study, tyrosinase and melanoma antigen recognized by T cells 1 (MART-1) mRNA expression was evaluated in serial samples obtained before definitive surgery and during follow-up in patients with American Joint Committee on Cancer stage I-II melanoma. Serial samples (n=2,262) were collected from 236 patients from 1997 to 2002. Analyses of the RNA samples were performed with a calibrated reverse transcriptase-PCR assay. Gender, age, primary tumor site, ulceration, thickness, Clark level, and histological subtype were analyzed together with tyrosinase and MART-1 mRNA treated as updated covariates in a Cox proportional-hazard model. After a median follow-up time of 66 months, 42 out of 236 patients (18%) had relapsed. The following variables were significantly associated with relapse-free survival in the univariate analyses: tyrosinase, MART-1, gender, ulceration, thickness, Clark level, and histological subtype. Entering these covariates into a multivariate Cox analysis resulted in thickness as the single independent prognostic factor (P<0.0001), whereas MART-1 (P=0.07) approached significance at the 5% significance level. The serial measurements of tyrosinase and MART-1 mRNA in peripheral blood of stage I-II melanoma patients cannot be demonstrated to have independent prognostic impact on relapse-free survival.

Five-year results of prognostic value of tyrosinase in peripheral blood of uveal melanoma patients

Tyrosinase-based reverse transcriptase-polymerase chain reaction (RT-PCR) is a method for the detection of circulating melanoma cells in peripheral blood. To our knowledge, no long-term studies on the prognostic impact of tyrosinase PCR in uveal melanoma have yet been reported. In this prospective, non-randomized, observational cohort study, we included 41 patients with uveal malignant melanoma. RT-PCR for tyrosinase was performed in each patient before and after treatment. A clinical follow-up was performed for each patient for at least 5 years, including chest X-ray, serum liver enzyme determination, ultrasound of the liver and bone scintigraphy. The PCR results, age of the patients, tumour size, tumour location, tumour therapy, internal reflectivity, histology, development of distant metastasis and survival rate during follow-up were analysed. At the time of diagnosis, tyrosinase messenger RNA (mRNA) in peripheral blood, suggesting the presence of circulating melanoma cells, was detected in 16 of the 41 patients. Sixty-nine percent of the PCR samples with a positive result prior to therapy revealed a negative result after therapy. The internal reflectivity of the tumour (P=0.021) and the 5-year survival (P=0.023) showed a statistically significant association with positive PCR. It can be concluded that tyrosinase RT-PCR is a sensitive method for the detection of melanoma cells in peripheral blood. This study indicates that the presence of tumour cells in peripheral blood correlates with 5-year survival. Our results suggest a prognostic value of this method. Nevertheless, prospective analysis of a larger cohort is needed to determine the ultimate value of RT-PCR for tyrosinase in blood testing.

Molecular detection of MART-1, tyrosinase and MIA in peripheral blood, lymph nodes and metastatic sites of stage III/IV melanoma patients.

Melanoma lesions that develop in the same patient at different times or simultaneously at different locations may differ antigenically, because malignant melanoma is heterogeneous in terms of its biological, immunological and metastatic properties. The objective of this study was to characterize the molecular profiles of melanoma cells in peripheral blood, lymph nodes and metastatic tissues, employing the messenger RNA (mRNA) expression of tyrosinase, melanoma-inhibiting activity (MIA) and melanoma antigen recognized by T cells-1 (MART-1) as markers. Samples of cells propagated from metastatic sites were obtained from 17 stage III/IV melanoma patients and assayed by reverse transcriptase-polymerase chain reaction (RT-PCR), using specific primers for each marker. In eight patients, marker profiles were analysed in simultaneously obtained specimens of peripheral blood, lymph nodes and metastatic tissues originating from the same patient. Tyrosinase, MIA and MART-1 were expressed in 59%, 76% and 76% of the metastases, respectively. Simultaneously obtained specimens of peripheral blood, lymph nodes and metastatic tissues showed a high degree of homogeneity: 60%, 75% and 20% for tyrosinase, MIA and MART-1, respectively. Our findings suggest that the rather homogeneous expression pattern found in different tumour sites analysed in the same patient is of potential prognostic and therapeutic importance. Furthermore, melanoma lesions may be negative for the expression of antigens such as MART-1, and discrepancies in expression patterns between peripheral blood and metastatic tissues may occur, especially for this marker. Finally, our findings support the notion that molecular screening using an RT-PCR approach is appropriate in this kind of investigation.

Quantitative detection of circulating tumor cells in cutaneous and ocular melanoma and quality assessment by real-time reverse transcriptase-polymerase chain reaction.

Inconsistent reports on the detection of melanoma cells in peripheral blood by reverse transcriptase-PCR (RT-PCR) have resulted in uncertainty on the prognostic value of circulating melanoma cells. We developed real-time RT-PCR assays for quantitation of tyrosinase, MelanA/MART1, and gp100 and for porphobilinogen deaminase housekeeping gene. Melanoma tissue (n = 18), peripheral blood samples from healthy donors (n = 21), and patients with cutaneous (n = 122) and uveal (n = 64) melanoma from our institution were analyzed. For quality control, an additional 251 samples from ongoing multicenter studies were compared with in-house samples. Tyrosinase was not detected in healthy donor blood samples. For the two other markers, cutoff values had to be defined to distinct patient samples from controls. Patients with stage IV uveal and cutaneous melanoma expressed all three markers more frequently and at higher levels in peripheral blood as compared with earlier stages. The variation of expression was 4 logs and correlated with tumor load and serum lactate dehydrogenase. In 2 of 3 uveal melanoma patients, detection of circulating tumor cells preceded the development of liver metastases. The diagnostic sensitivity was optimal in blood samples containing >0.1pg/ microl porphobilinogen deaminase (95.7% of in-house samples and 57.4% of multicenter samples). Real-time RT-PCR is able to quantitatively define the quality of a sample and provides quantitative data for melanoma markers. Disparities in the results of previous studies may be attributable to undetected differences in sample quality. The prognostic relevance of this assay is currently under evaluation in several prospective randomized trials.

Detection of melanoma seeding during surgical procedures – an RT-PCR based model

Aim: It has long been suggested that malignant cells may be shed into the blood stream during any given surgical procedure for cancer. A number of studies have now reported the detection of occult melanoma cells in peripheral blood using a reverse transcriptase polymerase chain reaction (RT-PCR) based assay. The principal aim of these studies has been to determine a prognostic value for the test and not to evaluate the influence of intervention upon results.Methods:In this pilot study we aimed to determine whether the assay could be used as a model to detect cells that are seeded during surgery. Peripheral blood samples were obtained pre- and post-operatively on twenty patients undergoing surgery for malignant melanoma – ten with primary disease and ten undergoing regional lymphadenectomy. A further ten patients undergoing surgery for non-melanoma conditions provided controls.Results: Using RT-PCR, it was possible to identify tyrosinase transcripts in the peripheral blood of one of ten patients undergoing excision of local disease and four of ten undergoing surgery for regional metastatic disease.Conclusion: It was concluded that this technique does enable detection of a greater percentage of RT-PCR findings post-operatively. This in turn may provide a means for optimizing or comparing surgical techniques and provides a potential guide in the use of adjuvant therapies.

Quantitative RT-PCR assessment of melanoma cells in peripheral blood during immunotherapy for metastatic melanoma.

Circulating malignant cells in peripheral blood are thought to be precursors and surrogate markers of distant metastases and hence markers of a poor clinical outcome. In this study, we used the detection of MART-1 and tyrosinase (TYR) mRNA with a quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay to identify circulating melanoma cells. Blood samples were obtained from 35 patients with metastatic melanoma before, during and after treatment with interleukin-2, interferon-alpha and cisplatin. In addition, MART-1 and TYR protein was identified by immunohistochemistry in consecutive biopsies from 15 of the patients. Analysis of three daily blood samples for 3 days demonstrated that four out of 11 patients examined were negative for both markers on all occasions, and two patients were positive for both markers on all occasions but one. The remaining five patients showed sporadic low positive results for one or the other of the two markers. By comparing the immunohistochemistry results from consecutive biopsies with the RT-PCR results, we demonstrated that patients with MART-1 and TYR protein in their tumour cells had circulating MART-1 and TYR mRNA in 77% and 54% of the cases, respectively. During treatment, the majority of patients who were positive for MART-1 and TYR mRNA converted to being negative. However, these conversions did not significantly correlate with objective response. The presence of TYR mRNA in one of the first two samples showed a trend towards being an independent prognostic factor for poor survival.

Evaluation of standard tyrosinase RT-PCR in melanoma patients by the use of the LightCycler™ system

Background: Haematogenous spread influences outcome in melanoma patients. The clinical relevance of detecting circulating melanoma cells in peripheral blood by tyrosinase mRNA RT-PCR is, however, questioned as rates of positivity considerably vary between studies. Standard tyrosinase-nested RT-PCR was here compared with a real-time PCR technique. Methods: Forty-three blood samples from 20 stage III–IV melanoma patients were analyzed. Mononuclear cells were isolated using a Ficoll Hypaque gradient technique. Total RNA extracted by the acid guanidinum thiocyanate-phenol-chloroform method was reverse transcribed using random hexamers or specific primers. Standard tyrosinase-nested PCR was performed on Touchdown™ machine (Hybaid) and real-time PCR on a LightCycler™ instrument (Roche). Results: Only two samples from stage IV patients (one from random hexamers, one from antisense primers) were found tyrosinase positive with a 100% agreement between the two PCR techniques. A 10-fold dilution of the first-round products improved the PCR kinetic and the final amount of amplified product of positive samples, but not the rate of positivity. Conclusions: Efficiency of the PCR reaction can be monitored in an online fashion by the LightCycler™ instrument allowing technical improvements. However , tyrosinase mRNA RT-PCR cannot be yet considered as a useful technique in the monitoring of melanoma patients.

Detection of circulating melanoma cells in peripheral blood by a two-marker RT-PCR assay.

The aim of this study was to develop a highly sensitive two-marker assay for the detection of circulating melanoma cells in patients' blood using a reverse transcriptase-polymerase chain reaction (RT-PCR). We analysed the usefulness of two different sets of markers: tyrosinase and MUC-18 (TYR/MUC-18), and tyrosinase and MART 1 (TYR/MART 1). Total cellular RNA was isolated from 337 blood samples from 80 melanoma patients at different stages of the disease. All patients had undergone primary surgery. Assay sensitivity and specificity were confirmed using three different melanoma cell lines and two different fibroblast lines. In addition, blood from 47 healthy subjects and 10 patients with non-melanoma cancer was used as a negative control. We found that two-marker analysis is more accurate than the single tyrosinase assay. The frequency of melanoma cell detection in patients' blood was about 10% higher when the TYR/MART 1 two-marker assay was used. Using this assay we did not find any statistical correlation between the molecular markers and the UICC stage of disease or the Breslow thickness or Clark level of the primary melanoma. The frequency of melanoma cell detection with the TYR/MUC-18 two-marker assay was even higher than the TYR/MART 1 assay, but unfortunately the MUC-18 transcript was also present in about 20% of healthy subjects. Therefore we do not recommend the use of MUC-18 as a standard value marker.

Morphologically intact melanoma cells may be detected in peripheral blood of melanoma patients.

The detection of circulating melanoma cells has been the subject of numerous investigations in recent years. We developed a cellular approach to identifying circulating melanoma cells in peripheral blood using immunomagnetic cell sorting. The examination covered 205 blood samples from 155 melanoma patients and 30 samples from healthy persons and nonmelanoma patients. After density gradient centrifugation, the interphase was incubated with the 9.2.27 antibody. Positive cells were labeled with magnetic microbeads and enriched by immunomagnetic cell sorting. Cells were stained using an alkaline phosphatase-anti-alkaline phosphatase assay and examined by light microscopy. In spiking experiments, melanoma cells seeded at a concentration of one melanoma cell per milliliter of whole blood could be detected reliably. Circulating melanoma cells were not found in 30 controls, nor were 9.2.27-positive cells found in 41 patients with primary malignant melanoma. In patients with regional lymph node metastases and disseminated disease, circulating 9.2.27-positive cells could be detected in 3 of 29 patients (10%) and 13 of 85 patients (15%) examined, respectively. We conclude that immunomagnetic cell sorting is a promising method with high sensitivity and specificity. The method is not suitable for early detection of metastases but is a valuable tool for further investigating the biological characteristics of circulating melanoma cells.

Detection of neoplastic cells in blood of miniature pigs with hereditary melanoma

Tyrosine, a key enzyme of melanin biosynthesis, is widely used as a specific marker for the detection of dissemination or metastatic melanoma cells in peripheral blood and other tissues like lymph node or bone marrow, which are normally tyrosinase negative. The amplification of tyrosinase-specific mRNA by means of RT-PCR is a sensitive technique capable of detecting a single tumour cell in 5&amp;ndash;10 ml of whole blood. We have utilised this method to analyse the peripheral blood of laboratory miniature pigs with advanced cutaneous melanoma for the presence of tumor cells. This highly invasive hereditary malignancy can serve as an experimental model for the study of melanoma development and dissemination. For amplification of porcine gene, oligonucleotide primers derived from the sequence of human tyrosinase were used. These primers amplified fragment of the predicted length and restriction enzyme digestion confirmed their homology with the sequences of human tyrosinase gene. After the second round of amplification, tyrosinase could be detected up to the amount of 1 &amp;times; 10&lt;sup&gt;&amp;ndash;5&lt;/sup&gt; &amp;micro;g of total RNA isolated from porcine melanoma per 1 &amp;micro;g of control RNA. Blood samples from eight animals with advanced melanoma and from five non-melanoma control animals were examined for tyrosinase expression. Tyrosinase mRNA was detected in five samples from animals with malignant melanoma. Non-melanoma control animals gave negative results.