Detection of melanoma cells in peripheral blood by means of reverse transcriptase and polymerase chain reaction

Serum S-100b protein as a prognostic marker in malignant cutaneous melanoma

PURPOSE

To evaluate whether S-100B protein in serum is an independent prognostic marker in malignant melanoma.

MATERIALS AND METHODS

S-100B protein in serum was analyzed in 1,007 consecutive patients with histologically verified cutaneous malignant melanoma. At the time of blood sampling, 876 patients were in clinical stage I, 35 were in stage II, and 96 were in stage III. The serum concentrations of S-100B protein were measured by a luminescence immunoassay (LIA).

RESULTS

The mean serum concentration of S-100B protein was significantly related to clinical stage, with the lowest level in stage I and the highest in stage III. In a multivariate analysis, S-100B protein levels in serum showed the strongest prognostic impact of the factors analyzed with respect to disease-specific survival in clinical stages II to III, followed by clinical stage. Serum S-100B protein was not a significant independent prognostic factor in clinical stage I, where tumor thickness showed the strongest relation to melanoma-specific survival, followed by ulceration and satellites.

CONCLUSION

This investigation contains the largest material of patients so far analyzed with the new LIA assay of S-100B protein in serum and confirms that S-100B protein in serum is correlated with clinical stage and is an independent prognostic marker in clinical stages II and III.

Evaluation of the use of tyrosinase-specific and melanA/MART-1-specific reverse transcriptase-coupled--polymerase chain reaction to detect melanoma cells in peripheral blood samples from 299 patients with malignant melanoma

BACKGROUND

There is a current need for a reliable prognostic marker for melanoma patients, particularly those with stage 2 and stage 3 disease, so that adjuvant therapies can be directed appropriately.

OBJECTIVES

To establish whether or not the use of tyrosinase-specific or melanA/MART-1-specific reverse transcriptase-coupled-polymerase chain reaction (RT--PCR) of peripheral blood cells detects preclinical disease progression in patients with malignant melanoma.

METHODS

Two hundred and ninety-nine patients with melanoma in clinical stages 1--4 were observed in this study. Samples were obtained sequentially from 153 of these patients at 4-week intervals over a period of up to 2 years and correlated with clinical evidence of disease activity. Tyrosinase and melanA/MART-1 amplicons were analysed by agarose gel electrophoresis and Southern blot hybridization subsequent to a single round of amplification.

RESULTS

We demonstrated a statistically significant increase in tyrosinase RT--PCR positivity with advancing stage of melanoma progression. The percentage tyrosinase positivity in 910 samples tested was: stage 1, 135 samples, 34% positive; stage 2, 196 samples, 51% positive; stage 3, 423 samples, 50% positive; and stage 4, 156 samples, 65% positive. The positivity rate for individual patients tested sequentially was higher if only one positive test was required to label a patient positive, at 42%, 65%, 82% and 81% for patients in stages 1--4, respectively. However, we did not find a clear pattern of conversion from negativity to positivity in patients who progressed during the study from stage 2 to stage 3 or stage 3 to stage 4, and found no clear evidence of increased positivity rates in the 6-week period following melanoma-related surgery in patients with stage 3 and 4 disease. The positivity rate for melanA/MART-1 was lower for both patients and samples, and no melanA/MART-1-positive sample was negative for tyrosinase.

CONCLUSIONS

We conclude that the presence of circulating tyrosinase-positive cells as detected by this method appears to be a discontinuous rather than a continuous phenomenon, even in patients with stage 4 disease. For this reason the assay cannot be recommended as a method of sequentially monitoring individual patients in a clinical setting.

Clinical significance of circulating cancer cells in peripheral blood detected by reverse transcriptase-polymerase chain reaction in patients with breast cancer

Detection of breast cancer micrometastases based on specific genetic markers may provide useful information to justify appropriate therapeutic strategies. We examined the presence of a carcinoembryonic antigen (CEA) messenger RNA(mRNA) in the peripheral blood of 32 patients with varying stages of breast cancers by means of the reverse transcriptase-polymerase chain reaction (RT-PCR) assay prior to and after the curative operation. CEA mRNA were detected in the peripheral blood samples from 12 (38%) out of 32 breast cancer patients prior to surgery. Among 12 CEA mRNA-positive patients prior to surgery, 4 (33.3%) relapsed from breast cancer within 2 years after surgery. Moreover, CEA mRNA was detected in the peripheral blood samples obtained prior to surgery in 3 out of 11 patients (27.2%) with a stage I disease. One out of three of these patients had a relapse in lung. There were four patterns of CEA mRNA expression, ( +, + ), (+, -), (-, + ), and (-, -) in the pre- and post-operative blood samples. In 12 CEA mRNA-positive patients submitted to surgical resection of the primary tumor, persistence of CEA mRNA expression was observed in five patients (+, +) within a month after surgical treatment. Three out of these 5 patients (60%) relapsed from breast cancer within 2 years after surgery. In 7 other patients (+, -), CEA mRNA expression was not detected within a month after tumor removal, and recurrence occurred in 1 out of the 7 patients (14%) within 2 years after surgery. In 19 patients, CEA mRNA expression was not detected in pre- or post-operative blood samples (-, -). There was a patient whose blood sample was negative for CEA mRNA before the operation, but changed to show a positive result after surgery (-,+). No recurrence was found in 20 of CEA mRNA-negative patients prior to surgery (-, +), (-, -). This study suggested that the presence of CEA mRNA expression in preoperative peripheral blood sample represent the progression of the disease, especially the risk of hematogenous metastasis in the patients in spite of their clinical stage, and the presence of CEA mRNA in the postoperative blood sample may represent the evidence of a residual disease. Thus consideration might be given for adding combined multi-modal therapy.

Does intensive histopathological workup by serial sectioning increase the detection of lymph node micrometastasis in patients with primary cutaneous melanoma?

Various histopathological techniques have been developed in order to improve the detection of micrometastasis in the regional lymph nodes of patients with malignant melanoma. Our standard histopathological examination of lymph nodes included haematoxylin and eosin (H & E) staining and immunohistochemistry (IH) using antibodies to HMB-45 and S-100 proteins of three paraffin sections at one level. In addition, lymph nodes were examined by molecular biological methods using tyrosinase reverse transcription-polymerase chain reaction (RT-PCR). In this study, we investigated the use of step sections and IH in lymph nodes regarded as negative by standard histopathology but positive by tyrosinase RT-PCR, suggesting the presence of tumour cells. In a series of 76 consecutive patients with stage I and II cutaneous melanoma, a total of 156 regional lymph nodes were examined by H & E staining, IH and tyrosinase RT-PCR. All lymph nodes were bisected along their long axis for separate evaluation. In 21 patients, at least one lymph node in the regional nodal basin reported as tumour-negative by standard histopathology was demonstrated to express tyrosinase (total number of nodes = 33). These 33 lymph nodes were re-examined by H & E and IH at 10 additional levels of the paraffin block. Only one lymph node from one patient had occult melanoma cells in deeper levels detected exclusively by IH. Six out of 20 patients with positive findings exclusively on tyrosinase RT-PCR developed tumour recurrences during a median follow-up of 34 months. We therefore conclude that additional step sectioning with IH does not significantly increase the detection of tumour-positive lymph nodes. Patients with melanoma cells detected exclusively by RT-PCR, however, were shown to be at increased risk for tumour recurrence.

Molecular quantification and mapping of lymph-node micrometastases in cervical cancer

BACKGROUND

A proportion of patients with cancer and lymph nodes negative on histology will develop recurrence. Reverse-transcriptase PCR (RT-PCR) is a highly sensitive method for detection of lymph-node micrometastases, but accurate quantitative assessment has been difficult.

METHODS

We studied primary tumours and 156 lymph nodes from 32 patients with cervical cancer (stage IA2, IB1, and IB2) and 32 lymph nodes from nine patients with benign disease. A fully quantitative, real-time RT-PCR assay was used to document absolute copy numbers of the epithelial marker cytokeratin 19. Primers and probe were designed not to amplify either of the two cytokeratin 19 pseudogenes.

FINDINGS

All primary tumours and histologically involved lymph nodes (six) had more than 106 copies of cytokeratin 19 mRNA per microg total RNA. Expression of cytokeratin 19 (up to 1.1 x 10(5) copies per microg RNA) was detected in 66 (44%) of 150 histologically uninvolved lymph nodes, and in nodes from 16 of 32 patients with cervical cancer. 15 of these 16 patients with evidence of micrometastases had the highest cytokeratin 19 transcription level in a first lymph-node drainage station (three obturator, six internal, and six external iliac node). Transcription of cytokeratin 19 was found at a low level in just one of 32 lymph nodes obtained from nine patients with benign disease. Median copy number of cytokeratin 19 transcription was significantly higher (>10(3) copies) in association with adverse prognostic features.

INTERPRETATION

The results suggest that about 50% of early-stage cervical cancers shed tumour cells to the pelvic lymph nodes. The amount of cytokeratin 19 expression was related to clinicopathological features. Further studies are required to document the clinical implications of molecular micrometastases.

Reverse transcriptase polymerase chain reaction (RT-PCR) detection of melanoma-related transcripts in the peripheral blood and bone marrow of patients with malignant melanoma. What have we learned?

The detection of circulating tumor cells (CTC) and bone marrow micrometastases (BMM) by reverse transcriptase polymerase chain reaction (RT-PCR) may help predict recurrence and survival in malignant melanoma (MM). Since the appearance of the original article by Smith et al. in 1991 (Lancet 338:1227), several groups have attempted the detection of CTC and BMM in MM using RT-PCR for melanocytic specific markers, mainly tyrosinase mRNA. Most studies show that tyrosinase is not present in the PB and BM of control individuals without MM. The PCR positivity rates in MM are extremely variable, ranging from 0% to 100%. There was a correlation between RT-PCR and stage in some but not all of the studies. These disparate findings could in part be explained by differences in RNA extraction and blood separation techniques, to unrecognized contamination leading to false positive results, or differences in patient selection. Despite these discrepancies, we and others have shown that RT-PCR for tyrosinase mRNA in PB is able to predict overall survival (OS) and disease-free survival (DFS) in a statistically significant manner. In AJCC stage II-IV patients rendered surgically free of disease, we found that blood tyrosinase positivity was an independent predictor of OS and DFS. We also found that BM tyrosinase positivity is an independent predictor of DFS in the same group of patients. RT-PCR may help identify subgroups of patients at high risk for early relapse for more aggressive adjuvant therapy. Large prospective studies and interlaboratory quality assurance initiatives are necessary to confirm the accuracy and prognostic value of these RT-PCR assays.

Prognosis of metastatic melanoma: no correlation of tyrosinase mRNA in bone marrow and survival time

Recent publications suggest that tyrosinase mRNA in blood as well as in bone marrow is detectable only in a subgroup of patients with metastatic melanoma. This would imply that tyrosinase mRNA is of limited value as a tumor marker. We addressed the question of whether patients with metastatic melanoma and RT-PCR-detectable tyrosinase mRNA in blood or bone marrow have a different prognosis than tyrosinase mRNA-negative patients. Twenty melanoma patients with widespread clinical metastases were enrolled; the survival time after first diagnosis of visceral metastases was correlated to tyrosinase mRNA presence in blood and bone marrow samples. The time of survival of eight patients with metastatic melanoma and detectable tyrosinase mRNA in either blood or bone marrow was not different from the prognosis of 12 patients without detectable tyrosinase mRNA in either blood or bone marrow. Detection of tyrosinase mRNA in blood or bone marrow samples of melanoma patients with advanced disease seems to have no substantial relevance for survival time and outcome of disease. In this constellation, detection of tyrosinase mRNA by RT-PCR is not a valid tumor marker. Nevertheless, tyrosinase positivity in bone marrow in earlier tumor stages might indicate increased risk for the development of distant metastases. This should be addressed in further studies.

The clinical utility of multimarker RT-PCR in the detection of occult metastasis in patients with melanoma

Cutaneous melanoma is characterized by a high propensity for metastasis. Currently, surgical intervention remains the mainstay of therapy. This approach has proven most beneficial when the diagnosis is of early stage primary lesions. Likewise, patients undergoing resection for a solitary site of metastasis have shown a survival advantage. Identification of metastatic disease depends predominantly on radiographic techniques requiring the presence of significant tumor burdens for successful imaging. However, at that time, the role of surgery and/or biochemotherapy may be of limited value. Techniques to identify minimal disease states may permit more accurate assessment of prognosis. The detection of occult tumor cells by RT-PCR in the blood, lymph nodes, and bone marrow of melanoma patients provides one such approach to monitor tumor progression. Single-marker RT-PCR has been used as one such approach but is noted to have limitations in sensitivity and specificity based on the heterogeneity of tumor marker expression among tumors as well as within an individual tumor lesion or among multiple lesions in individual patients. We employed a multimarker reverse transcriptase polymerase chain reaction assay that demonstrates improved sensitivity over a single-marker approach. Currently, the consequences of detecting systemic subclinical metastasis remain unknown pending longer-term follow-up. The detection of occult melanoma cells using molecular techniques in conjunction with known clinicopathologic prognostic factors may provided a novel and efficient approach in monitoring tumor progression and further identify high-risk patients diagnosed early in the disease course.

The clinical relevance of molecular staging for melanoma

The presence of metastatic disease in the regional nodal basin is the most important prognostic indicator for patients with malignant melanoma. The metastatic status of the sentinel lymph node (SLN), defined as the first node in the basin to drain a primary tumor, has been shown to represent that of the entire basin. Since routine histologic examination of lymph nodes often underestimates the presence of micrometastatic disease, a more sensitive assay for detecting tumor cells is needed. We have previously shown that a molecular assay based on the reverse transcriptase polymerase chain reaction (RT-PCR) was able to define a population of patients at higher risk for both recurrence and death, compared with routine H&E histology. Recently, we have compared "molecular staging" of patients by RT-PCR with conventional S-100 immunohistochemistry (IHC) staining of the SLNs. In these studies, SLN specimens were bivaled, and half of each specimen was examined by routine histology, including both H&E and S-100 IHC. The other half of each specimen was analyzed by a nested RT-PCR assay. H&E histology alone detected metastatic disease in 36 of 233 (16%) patients tested. Serial sectioning and IHC detected micrometastatic disease in another 16 patients, thus increasing the proportion of patients with nodal disease to 22%. RT-PCR detected micrometastatic disease in 114 of 181 patients who were negative by conventional methods, further increasing the proportion of patients with evidence of nodal disease to 70% overall. The clinical significance of these findings is still uncertain. The value of additional therapy (including elective lymph node dissection and interferon therapy) for patients who are positive only by the molecular method is currently being investigated by the national multi-center Sunbelt Melanoma Trial.

Predictive laboratory diagnostics in oncology utilizing blood-borne cancer cells--current best practice and unmet needs

The aim of laboratory diagnostics in oncology is to improve the clinical outcome of cancer by allowing earlier detection. Molecular knowledge of cancer should increase the number of risk and prognostic factors and will allow development of methods for detection and elimination of even very small tumors. Thus, the race for the specific tumor antigen in peripheral blood and the race for the blood-borne cancer cell happened simultaneously. The direct detection of the cells which have the highest probability to harbor all the properties mandatory to be life-threatening, conceivably metastatic, would be the most promising way to find the target structure of malignancy. Methods applying enrichment techniques based on density, morphology, tissue specific protein and tumor-associated protein detection enabled multi-parametric analysis of those blood-borne cancer cells. In exemplary studies it was demonstrated that the count of cell clusters positive for the tissue-specific proteins cytokeratin and prostate-specific antigen (PSA) from the peripheral blood of prostate cancer patients and a combination of a tissue-specific protein, a oncogenic receptor protein cytokeratin and p185(c-erbB-2) from the peripheral blood of breast cancer patients is related to the stage of the diseases. Breast cancer patients who presented with cytokeratin/p185(c-erbB-2) positive cell clusters showed a decrease of those cells under adriamycin adjuvant therapy. Nevertheless, additional molecular markers are required to characterize the functional properties of blood-borne cancer cells. Therefore, the genome of the cells can be investigated using a procedure for indirectly detecting aberrations of defined gene locations, i.e. multiplex microsatellite polymerase chain reaction. Up to now, the methods applied to the separation of blood-borne cancer cells are time-consuming and rather expensive. They consist of an initial enrichment step of density gradient centrifugation or buffy coat preparation followed by a specific isolation step using superparamagnetic microbeads coupled to antibodies, filter techniques or multi-parametric flow cytometry. Novel technologies have to be applied using miniaturization, integration and parallel-processing techniques based on those used in the computer industry to overcome the drawbacks.

Biological behaviour and clinical implications of micrometastases

BACKGROUND

The most important prognostic determinant in cancer is the identification of disseminated tumour burden (metastases). Micrometastases are microscopic (smaller than 2 mm) deposits of malignant cells that are segregated spatially from the primary tumour and depend on neovascular formation (angiogenesis) to propagate.

METHODS

The electronic literature (1966 to present) on micrometastases and their implications in malignant melanoma and epithelial cancers was reviewed.

RESULTS

Immunohistochemical techniques combined with serial sectioning offer the best accuracy for detection of nodal micrometastases. Molecular techniques should be reserved for blood samples or bone marrow aspirates. Detection of micrometastases in regional lymph nodes and/or bone marrow confers a poor prognosis in epithelial cancers. The concept of sentinel node biopsy combined with serial sectioning and dedicated screening for micrometastases may improve staging procedures. Strategies against angiogenesis may provide novel therapies to induce and maintain micrometastatic dormancy.

CONCLUSION

The concept of micrometastases has resulted in a paradigm shift in the staging of epithelial tumours and our overall understanding of malignant processes.

Role of RT-PCR tyrosinase detection in the monitoring of patients with advanced metastatic melanoma

In recent studies a new method has been proposed to detect circulating melanoma cells in the peripheral blood of patients, based on the amplification of the mRNA for tyrosinase, an enzyme involved in melanin biosynthesis that is expressed only by melanocytic cells. The sensitivity and clinical relevance of this method are still controversial. In the present study, 596 blood samples from 186 melanoma patients at various clinical tumour stages, together with samples from 25 healthy volunteers, were analysed with the aim of investigating the value of tyrosinase detection in predicting melanoma recurrence. We suggest a possible role for this marker in the monitoring of melanoma patients after the excision of regional lymph node metastases, and provide evidence that tyrosinase is related to the status of disease in advanced metastatic patients. Moreover, chemotherapy administration appeared to influence tyrosinase determination and may explain the discrepancies in the reported percentages of positive samples.

Quantification of Melanoma Cell-specific MART-1 mRNA in Peripheral Blood by a Calibrated Competitive Reverse Transcription-PCR

Background: Reverse transcription-PCR (RT-PCR) amplification of melanoma cell-specific mRNA can detect melanoma cells in the peripheral blood of patients with malignant melanoma. We present a method to quantify mRNA coding for the melanoma-specific melanoma antigen recognized by T cells #1 (MART-1) in RNA isolated from peripheral blood.

Methods: To establish a calibration curve, we measured the concentration of MART-1 mRNA in SK-MEL-28 melanoma cells grown in vitro by competitive RT-PCR. Serial dilutions of these cells were used as calibrators in the assay. The assay was conducted by adding a fixed amount of a RNA internal standard to RNA isolated from either peripheral blood or the calibrators before RT-PCR amplification with MART-1 primers in a nested PCR design. The amount of MART-1 mRNA in blood samples was calculated from the calibration curve.

Results: Addition of melanoma cells grown in vitro to blood from healthy donors demonstrated that the method can detect a single SK-MEL-28 melanoma cell in 1 mL of blood (1.5 × 10−21 mol MART-1 mRNA/mL). MART-1 mRNA was observed in 4 of 12 blood samples from patients with malignant melanoma, at concentrations of 3–18 × 10−21 mol MART-1 mRNA/mL of blood. No MART-1 mRNA was detected in blood samples from 25 controls without malignant melanoma. Intra- and interassay CVs were 15% (n = 12; mean = 44 × 10−21 mol MART-1 mRNA/mL) and 33% (15 samples analyzed in two different analytical runs; mean = 30 × 10−21 mol MART-1 mRNA/mL), respectively.

Conclusions: Our method is the first competitive RT-PCR assay for quantification of melanoma cells in blood samples that compensates for the variation of both the reverse transcription and PCR reactions. The method allows the inclusion of control samples for continuous quality assessment.

No correlation of tyrosinase mRNA in bone marrow with prognosis of metastatic melanoma

BACKGROUND

Recent publications suggest that tyrosinase mRNA in blood as well as in bone marrow is detectable only in a subgroup of patients with metastatic melanoma.

OBJECTIVE

We addressed the question, whether patients with metastatic melanoma and with RT-PCR-detectable tyrosinase mRNA in blood or bone marrow have a different prognosis compared to tyrosinase mRNA-negative patients.

METHODS

20 melanoma patients with widespread clinical metastases were enrolled and the survival time after first diagnosis of visceral metastases was correlated to tyrosinase mRNA presence in blood and bone marrow samples.

RESULTS

The time of survival of 8 patients with metastatic melanoma and detectable tyrosinase mRNA in either blood or bone marrow was not different from the prognosis of 12 patients without detectable tyrosinase mRNA in either blood or bone marrow.

CONCLUSION

Although based on a limited number of patients our results suggest that detection of tyrosinase mRNA in blood or bone marrow samples of melanoma patients with advanced disease seems to have no substantial relevance for survival time and outcome of disease. For this purpose, detection of tyrosinase mRNA by RT-PCR is not a valid tumor marker. Nevertheless, tyrosinase positivity in bone marrow in earlier tumor stages might indicate increased risk for the development of distant metastases. This should be addressed in further studies.

Detection of tumor circulating cells by cytokeratin 20 in the blood of patients with endometrial carcinoma

BACKGROUND

Cytokeratins are constituents of the intermediate filaments of epithelial cells which are expressed in various combinations depending on the epithelial type and the degree of differentiation. Using the reverse transcriptase-polymerase chain reaction technique (RT-PCR) we recently demonstrated that: (1) Cytokertin 20-the most recent discovered cytokeratin-is expressed in endometrial carcinoma tumors but not in the endometrium of patients with benign diseases, and (2) CK-20 is not expressed in blood cells. The aim of this study is to examine whether CK-20 expression in blood can be used as a biomarker for the detection of the dissemination of malignant cells in patients treated for endometrial carcinoma.

METHODS

In the present study, we have used RT-PCR to determine the expression of CK-20 in the peripheral blood of the following groups: (1) preop new diagnosed patients (n = 20), (2) patients with no clinical evidence of disease following completion of definitive treatment (n = 33; 17 at low risk; 16 at high risk), (3) patients with recurrent disease (n = 6), and (4) a control group of healthy subjects (n = 16). RNA was extracted from cell pellets and analysed by RT-PCR using primers for CK-20.

RESULTS

Of the 20 patients of the first group 7 (35%) were CK-20 positive. Of the 33 patients of the second group 17 (51%) were CK-20 positive. Subdivision of this group showed that 9 of 17 (53%) were positive in the low-risk subgroup, and 8 of 16 (50%) were positive in the high-risk subgroup. All 6 patients with recurrent disease were positive, and all subjects in the control group were negative.

CONCLUSION

These results indicate that RT-PCR of CK-20, because of its high sensitivity, is a potential biomarker for detecting metastasis in blood samples of patients with endometrial carcinoma.

Serological markers for melanoma

We present a review of current literature concerning the significance of serological markers in melanoma patients. Results for cytokines, cytokine receptors, cell adhesion molecules, S100 protein, melanoma inhibitory activity, tissue-specific reverse transcription-polymerase chain reaction, neurone-specific enolase, lipid-bound sialic acid and melanin metabolites such as 5-S-cysteinyldopa and 6-hydroxy-5-methoxyindole-2-carboxylic acid are discussed. For most of these substances, serum levels are more pronounced in the more advanced stages of disease. Therefore, these markers seem to have no place in the early detection of melanoma. On the other hand, sensitivity in the advanced stages of disease seems to be < 100%, compromising their use as a new staging procedure. Some markers show promising results as a possible prognostic factor in the early detection of disease progression or in the prediction of therapy outcome. If confirmed by further studies, this could direct future therapeutic strategies and could help to select patients who would benefit most from more aggressive (adjuvant) therapies. In addition, the study of some of these substances could add to the knowledge of tumour biology and immunology.

Molecular and prognostic classification of advanced melanoma: a multi-marker microcontamination assay of peripheral blood stem cells

The presence or absence of melanoma cells in human peripheral blood has recently been shown to be associated with disease prognosis, including overall survival. The detection of tyrosinase mRNA-positive circulating melanoma cells by reverse transcription-polymerase chain reaction (RT-PCR) has been limited to disseminated tumours expressing measurable amounts of this melanocyte-specific enzyme. To biologically classify both melanotic and amelanotic melanomas and to evaluate the clinical and prognostic relevance of tumour cell microcontamination, we examined autologous peripheral blood stem cell (PBSC) harvests from patients with advanced malignant melanoma prior to dose-escalated chemotherapy. To assay heterogeneous melanoma cell antigen expression, we developed a highly sensitive RT-PCR using four melanoma- and one tumour-associated antigen as molecular markers. Expression of the melanocyte-associated transcripts of tyrosinase, MART1/Melan-A, tyrosinase-related protein-1 (TRP-1) and tyrosinase-related protein-2 (TRP-2) as well as the tumour-specific transcript of MAGE-3 was analysed by RT-PCR in PBSC harvests from 31 patients. Seven of the 31 PBSC harvests tested positive for one or more molecular markers: two patients for tyrosinase only, and one patient for MAGE-3 only, one patient for tyrosinase and MAGE-3, one for tyrosinase and MART1/Melan-A, and two patients for tyrosinase, MART1/Melan-A, TRP-2 and MAGE-3. mRNA-positive patients exhibited a significantly impaired overall survival (P = 0.0032), with a median survival of 3 months as opposed to 10 months in PBSC mRNA-negative patients. In conclusion, the use of this multiple-marker microcontamination assay allowed for molecular and prognostic classification of advanced malignant melanoma.

Molecular detection and characterisation of circulating tumour cells and micrometastases in solid tumours

The detection and molecular characterisation of circulating tumour cells (CTC) and micrometastases may have important prognostic and therapeutic implications. Because their numbers are very small, these tumour cells are not easily detected using conventional methods. In the last decade, numerous groups have attempted to detect occult tumour cells in solid malignancies using the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). These assays were in the vast majority directed against tissue-specific markers. PCR was shown to be superior to conventional techniques in detecting occult tumour cells allowing the identification of one malignant cell mixed with 1-10 million normal cells. In some tumours like melanoma and prostatic carcinoma, tissue-specific transcripts were detected with high specificity in the blood of patients with localised and advanced disease. In some reports, PCR was shown to be a strong predictor of poorer outcome. However, due to the many limitations of PCR (e.g false-positives), many groups are developing new approaches for the detection of occult tumour cells. The most attractive technique involves immunomagnetic isolation of CTC and micrometastases prior to downstream analysis. The tumour-rich magnetic fraction can be subjected to RT-PCR, immunocytochemistry and in situ hybridisation. This will lead to better quantification and molecular characterisation of these tumour cells. In conclusion, the molecular detection and characterisation of occult tumour cells offer a great opportunity for better stratifying patients with solid tumours and for developing new prognostic markers and targeted therapies.

Quantitative Analysis of Tyrosinase Transcripts in Blood

Background: Tyrosinase is an enzyme unique to pigment-forming cells. Methods using this transcript for detection of melanoma cells in blood have given divergent results. Quantitative analytical procedures are therefore needed to study the analytical performance of the methods.

Methods: Mononucleated cells were isolated by Percoll centrifugation. RNA was isolated by each of three methods: UltraspecTM-II RNA isolation system, FastRNATM GREEN Kit, and QIAamp RNA Blood Mini Kit. cDNA was synthesized using random hexamer primers. A tyrosinase-specific product of 207 bp was amplified by PCR. As an internal standard (and competitor) we used a 207-bp cDNA with a base sequence identical to the tyrosinase target except for a 20-bp probe-binding region. The PCR products were identified by 2,4-dinitrophenol (DNP)-labeled probes specific for tyrosinase (5′DNP-GGGGAGCCTTGGGGTTCTGG-3′) and internal standard (5′DNP-CGGAGCCCCGAAACCACATC-3′) and quantified by ELISA.

Results: The calibration curves were linear and had a broad dynamic measuring range. A detection limit (2 SD above zero) of 48 transcripts/mL of blood was obtained from a low control. The analytical imprecision was 50% and 48% at concentrations of 1775 and 17 929 transcripts/mL (n = 12 and 14, respectively). With the cell line SK-Mel 28 added to blood and RNA extracted with the Ultraspec, Fast RNA, and QIAamp RNA methods, we found (mean ± SD) 1716 ± 1341, 2670 ± 3174, and 24 320 ± 5332 transcripts/mL of blood. Corresponding values were 527 ± 497, 2497 ± 1033, 14 930 ± 1927 transcripts/mL of blood when the cell line JKM86-4 was added. One high-risk patient was followed by repeated analysis of tyrosinase transcripts in blood. The melanoma marker 5-S-cysteinyldopa in serum and urine was within reference values, but tyrosinase mRNA was slightly increased (120–168 transcripts/mL of blood). The tyrosinase mRNA increased to 1860 transcripts/mL concomitant with the increase in 5-S-cysteinyldopa; later a spleen metastasis was found.

Conclusions: The results obtained with different RNA extraction methods illustrate the importance of quantitative methods for validation of methods. The use of QIAamp RNA improved the extraction efficiency considerably. Data from a case study suggest the assay is suitable in the follow-up of patients with high risk of developing metastases.

Limitations of the nested reverse transcriptase polymerase chain reaction on tyrosinase for the detection of malignant melanoma micrometastases in lymph nodes

The specificity and sensitivity of the nested reverse transcriptase polymerase chain reaction (RT-PCR) on tyrosinase was studied, for the detection of micrometastases of malignant melanoma. The specificity was assessed in the blood of six healthy donors, four patients with non-melanoma cancers of which one patient was treated with granulocyte-colony stimulating factor. Lymph nodes of nine patients without malignant melanoma were tested and four cell lines of various other tumours. Six of the nine non-melanoma lymph nodes were positive in this assay. The sensitivity was tested in a spike experiment in vitro, using a melanoma cell line. The detection limit was ten melanoma cells per 10(7) peripheral blood lymphocytes.

Human melanocytes and melanomas express novel mRNA isoforms of the tyrosinase-related protein-2/DOPAchrome tautomerase gene: molecular and functional characterization

We previously reported that a melanoma antigen, recognized by tumor-specific cytotoxic T lymphocytes, was encoded by intron sequences retained in a partially spliced transcript of the tyrosinase-related protein-2/DOPAchrome tautomerase gene. At difference with the mRNA encoding tyrosinase-related protein-2, this anomalous transcript was not expressed in melanocytes. This study examined whether neoplastic and/or normal cells of the melanocytic lineage could express additional forms of tyrosinase-related protein-2 mRNA. Screening of a melanoma-derived cDNA library with a tyrosinase-related protein-2 probe allowed identification of two novel isoforms. The first, tyrosinase-related protein-2-long tail, corresponds to the dominant transcript detected on melanomas and melanocytes by northern blot analysis. Tyrosinase-related protein-2-long tail is identical to the tyrosinase-related protein-2-encoding published cDNA sequence except for an extended 3'-untranslated region and is originated by alternative polyadenylation. This novel 3'-untranslated region contains an alternatively spliced, tyrosinase-related protein-2 last exon in the second isoform (tyrosinase-related protein-2-8b). The protein encoded by tyrosinase-related protein-2-8b is identical to tyrosinase-related protein-2 in its first 460 amino acids but possesses a different carboxyl-terminus devoid of transmembrane domain. Tyrosinase-related protein-2-long tail exhibited DOPA-chrome tautomerase activity, when transiently transfected into COS-7 cells. On the contrary, no detectable activity was exhibited by tyrosinase-related protein-2-8b. Reverse transcription-polymerase chain reaction analysis indicated that tyrosinase-related protein-2-long tail and tyrosinase-related protein-2-8b are expressed by tyrosinase-related protein-2-positive melanomas and normal melanocytes. Moreover all cell lines positive for tyrosinase-related protein-2 isoforms expressed tyrosinase and, all but one, tyrosinase-related protein-1. These data show that the human tyrosinase-related protein-2/DOPAchrome tautomerase gene can yield different isoforms by alternative poly(A) site usage or by alternative splicing. The pattern of expression of these isoforms suggest that they might play a part in the normal pathway of melanin biosynthesis.

gp100 mRNA is more sensitive than tyrosinase mRNA for RT-PCR amplification to detect circulating melanoma cells in peripheral blood of melanoma patients

Two different melanocyte-specific mRNAs are studied as markers for circulating melanoma cells in vitro using the human melanoma cell line G361 and in vivo using blood samples from Japanese melanoma patients at different clinical stages. These mRNAs encode tyrosinase, the most essential enzyme for melanin synthesis, and gp100, a melanosomal matrix glycoprotein recognized by monoclonal antibody HMB-45. We used reverse-transcription polymerase chain reaction (RT-PCR) to detect tyrosinase mRNA and gp100 mRNA in peripheral blood. Since melanocytes would not normally be present in peripheral blood, the detection of those transcripts should indicate the presence of circulating melanoma cells. RT-PCR detection of these two mRNAs was highly sensitive and specific. Our in vitro study showed that as few as 10 melanoma cells in 0.125 ml normal blood could be detected. In in vivo study, 130 blood samples from 55 melanoma patients gave positive and variably sensitive results, whereas no samples from healthy controls or patients with other cancers gave positive results. Tyrosinase mRNA was not detected in any of the melanoma patients. gp100 mRNA was detected in 12 of 55 melanoma patients, in none of five stage I patients (0%), in four of 26 stage II patients (15.4%), in one of six stage III patients (16. 7%) and in seven of 18 stage IV patients (38.9%). Thus gp100 mRNA is a more sensitive marker for detecting circulating melanoma cells compared with tyrosinase mRNA.

Clinical relevance of molecular staging for melanoma: comparison of RT-PCR and immunohistochemistry staining in sentinel lymph nodes of patients with melanoma

OBJECTIVE

To determine the clinical significance of a molecular assay based on the reverse transcriptase polymerase chain reaction (RT-PCR) for the presence of micrometastatic melanoma cells in sentinel lymph nodes (SLNs).

SUMMARY BACKGROUND DATA

Routine histologic examination of lymph nodes often underestimates the presence of micrometastatic disease. The authors have previously shown that an RT-PCR assay designed to detect melanocyte-specific expression of the tyrosinase gene could be used to define a population of patients at higher risk for both recurrence and death compared with routine hematoxylin and eosin (H&E) histology. In this study, the authors used the tyrosinase RT-PCR assay in a patient population examined by a more detailed histologic analysis, including S-100 immunohistochemistry.

METHODS

Patients underwent lymphatic mapping and SLN biopsy. SLN specimens were bivalved, and half of each specimen was serially sectioned and examined by routine H&E histology and S-100 immunohistochemistry. The other half of each specimen was analyzed by a nested RT-PCR assay.

RESULTS

Hematoxylin and eosin histology detected metastatic disease in 36 (16%) of the 233 patients tested. S-100 immunohistochemistry detected micrometastatic disease in another 16 patients, and 114 (63%) of 181 patients with histology-negative nodes had positive findings on RT-PCR. There were significant differences between PCR-positive and PCR-negative patient groups in Breslow thickness, Clark level, and the presence of ulceration of the primary tumor, factors that have been shown to correlate with recurrence and survival.

CONCLUSIONS

These results suggest that RT-PCR can increase the sensitivity of detection of metastatic melanoma cells in SLNs over the current standard methods, including H&E histology and S-100 immunohistochemistry. Further long-term follow-up is needed to detect actual differences in recurrence and overall survival.

High percentage of false-positive results of cytokeratin 19 RT-PCR in blood: a model for the analysis of illegitimate gene expression

Cytokeratin 19 (CK19) RT-PCR is widely used in order to detect circulating tumor cells in peripheral blood and bone marrow. However, increasing amounts of information support the fact that it is also associated with a high percentage of false-positive results. In our study, we not only managed to demonstrate the significant limitations of this method, but were also able to clarify the reasons behind these limitations. We developed a completely novel RT-PCR for CK19 and sequenced an intron at nucleotide (nt) 980 of the CK19 mRNA to exclude DNA contamination. Tumor dilution experiments were performed in order to analyze the specificity and sensitivity of the method. Control experiments using the blood of healthy donors were performed. Tumor cell dilution experiments gave a detection limit of one tumor cell. If tumor cells were mixed with an equal volume of pure mononuclear cells, the detection limit was 1 tumor cell in 10(5) mononuclear cells. RT-PCR of mononuclear cells from healthy blood donors gave false-positive results in 29% of the cases. We conclude that a significant decrease in the sensitivity of CK19 RT-PCR occurs if it is performed in blood cells and that the illegitimate CK19 gene expression in normal cells can lead to false-positive results. These limitations have to be taken into account if RT-PCR is to be used for the detection of tumor cells either in blood or in bone marrow in clinical practice.

Melanin binds reversibly to thermostable DNA polymerase and inhibits its activity

We found that both RNA and cDNA preparations derived from melanocytes contain a RT-PCR inhibitor that copurified with nucleic acids. Investigation of the candidate inhibitor melanin revealed that it potently blocks PCR at concentrations below 200 ng/ml, whereas 100 microg/ml melanin was required to inhibit reverse transcription. Melanin and thermostable DNA polymerase preferentially formed a distinct complex with reduced migration velocity as compared to pure polymerase in nondenaturating polyacrylamide gel electrophoresis. The inhibition of the enzyme by melanin could be reversed by diluting solutions of preformed complexes or by adding excess amounts of other proteins such as bovine serum albumin or dry milk. Our findings demonstrate that melanin is a potent inhibitor of thermostable DNA polymerase in vitro and that the inhibitory effect is conferred by a direct and reversible polymerase-melanin interaction.

Detection of circulating tumor cells in patients with non-small cell lung cancer undergoing lobectomy by video-assisted thoracic surgery: a potential hazard for intraoperative hematogenous tumor cell dissemination

OBJECTIVE

We prospectively tested whether circulating tumor cells can be found in the preoperative, intraoperative, and postoperative peripheral blood of patients with resectable non-small cell lung cancer who undergo video-assisted lobectomy.

METHODS

We assayed for carcinoembryonic antigen messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction in the peripheral blood taken before, during, just after the completion of the lobectomy and then 2 to 3 weeks, and again 5 to 6 weeks, after the operation in 29 patients with pathologic stage I non-small cell lung cancer who underwent video-assisted lobectomy. We also analyzed the prognostic value of carcinoembryonic antigen mRNA expression pattern in an additional 57 patients with stage I non-small cell lung cancer, whose blood samples were previously assayed for carcinoembryonic antigen mRNA.

RESULTS

Of the 29 patients, the preoperative blood samples from 18 patients were negative for carcinoembryonic antigen mRNA. Of these 18 patients, 16 (89%) had positive test results during operation, although the remaining 2 patients (11%) consistently showed negative test results. The occurrence of this change from negative to positive tests results for carcinoembryonic antigen mRNA during video-assisted lobectomy was significantly higher than in patients who underwent open lobectomy in a previous study (18 of 35 patients; 51%; P <.001). In the 57 patients with stage I cancer whose blood samples were previously assayed for carcinoembryonic antigen mRNA, patients with persistently positive test results for carcinoembryonic antigen mRNA before and during operation had a significantly shorter survival when compared with those patients whose test results were persistently positive.

CONCLUSIONS

Video-assisted lobectomy, as compared with open lobectomy, for non-small cell lung cancer may increase the risk of seeding tumor cells into the circulation during operation.

RT-PCR-based detection of occult disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. An overview

Despite recent progress in early detection and local curative therapy, patients with primary epithelial cancer quite frequently relapse with incurable metastasis. Early disseminated tumor cells that may be seminal for distant failure and are undetectable by current diagnostic methods have been identified by immunocytochemical techniques in bone marrow of cancer patients using monoclonal antibodies against cytokeratins. Recently, promising new molecular approaches, namely, reverse transcriptase--polymerase chain reaction (RT-PCR) assays, have been suggested as a potential technique for the detection of minimal residual tumor burden by targeting mRNA transcribed from epithelial genes in bone marrow, peripheral blood, or lymph nodes. Several studies using RT-PCR thus far indicate a highly sensitive and specific staging tool, although the prognostic value is still controversial. However, limitations may arise from ectopic expression of marker mRNA in hematopoietic cells and deficient expression in circulating tumor cells. The present review focuses on the relevant literature and demonstrates the range of current applications of RT-PCR-based assays for detecting disseminated tumor cells in peripheral blood and bone marrow of patients with solid tumors. We will both summarize technical evaluations of published molecular approaches and discuss the widely disparate results on PCR findings in clinical studies.

Molecular diagnostic tests in the diagnosis and management of thyroid carcinoma

The application of molecular analysis of gene expression to clinical tissue samples represents one of the most exciting new areas in "translational" thyroid cancer research. Current data suggest that molecular diagnostic assays may improve the sensitivity and accuracy of fine needle aspiration of thyroid nodules, fine needle aspiration of metastases, and detection of recurrent disease in peripheral blood samples. It is likely that at least some of these tests will become useful adjuncts in the diagnostic armamentarium of clinical endocrinologists in the future.

Melanoma. A multidisciplinary approach for the general surgeon

Advances in the understanding of the biology and treatment of melanoma have moved the care of melanoma patients into an increasingly multidisciplinary environment. Surgeons must understand these advances because they will often be responsible for directing the overall care of these patients. Most patients with melanomas more than 1 mm in diameter and no evidence of metastatic disease should be offered SLNB to more accurately stage them and direct decisions about participation in postoperative adjuvant therapy trials. Until the results of the MSLT are known, the effect of SLNB and ELND on outcome remains unknown. SLNs should be analyzed with serial sectioning and immunohistochemistry to avoid missing micro-metastatic disease. Based on the results of the ECOG-1684 trial, the FDA approved IFN-alpha 2b for the adjuvant treatment of melanoma patients with thick primary tumors (> 4 mm) or resected nodal disease. IFN-alpha 2b treatment is expensive and potentially toxic. The data from ECOG-1684 do not support the use of IFN-alpha 2b in patients with node-negative disease. In light of the ECOG-1690 trial results, the role of high-dose IFN-alpha 2b in the management of patients with resected nodal disease is considerably less clear. Any recommendations for treatment with high-dose IFN-alpha 2b should be made only after weighing the costs, side effects, and potential benefits for individual patients. Numerous, less toxic, promising, adjuvant immunotherapeutic strategies have been developed and are being tested in multicenter, prospective, randomized trials. These strategies include GMK, PMCV, and Melacine. If the results of any of these trials show a survival advantage compared with placebo or equivalent survival compared with IFN-alpha 2b, these immunotherapeutic agents will become the adjuvant treatment of choice for patients with resected high-risk melanoma. RT-PCR detection of tyrosinase in SLNs can identify patients with submicroscopic nodal disease who may be at increased risk for recurrence or death from melanoma. An ongoing, prospective, randomized trial will determine whether patients with histologically negative but RT-PCR-positive SLNs will benefit from lymphadenectomy or adjuvant IFN-alpha 2b therapy. RT-PCR can also identify minimal residual disease in peripheral blood and bone marrow from patients with high-risk melanoma, but RT-PCR analysis of peripheral blood and bone marrow is still experimental, and procedural details need to be standardized and prospectively validated in large patient groups before its use can be considered the standard of care.

Examination of regional lymph nodes by sentinel node biopsy and molecular analysis provides new staging facilities in primary cutaneous melanoma

Histopathologic parameters of the primary tumor, such as Breslow's tumor thickness and Clark's level of invasion are the current basis for prognostic classifications of primary cutaneous melanoma. Once patients develop regional node metastasis, histopathologic features of the primary melanoma no longer contribute significantly to survival prediction. In this tumor stage, the extent of lymph node involvement is the main prognostic factor. This study addresses the question whether application of a highly sensitive molecular biology assay for detection of submicroscopic melanoma cells in sentinel lymph nodes may be suitable to improve melanoma staging. One hundred and sixteen patients with primary cutaneous melanoma with a total of 214 sentinel lymph nodes were enrolled. Sentinel lymph nodes were analyzed by histopathology including immunohistochemistry and by reverse transcription-polymerase chain reaction for tyrosinase. Patients were examined for tumor recurrences during a follow-up period of 19 mo (median). Disease-free survival probabilities were calculated and independent prognostic factors were determined by multivariate analysis. Using histopathology, micrometastatic nodal involvement was detected in 15 patients (13%). Of the 101 patients with histopathologically negative sentinel lymph nodes, 36 were reclassified by positive tyrosinase reverse transcription-polymerase chain reaction and 65 patients were still negative by reverse transcription-polymerase chain reaction. Recurrences were observed in 23 (20%) of 116 patients. These tumor recurrences were demonstrated in 10 patients (67%) with histopathologically positive sentinel lymph nodes, in nine patients (25%) with submicroscopic tumor cells detected by reverse transcription-polymerase chain reaction, and in four patients (6%) negative by both methods. The differences in recurrence rates were statistically significant (p = 0.01). In a multivariate analysis, histopathologic and reverse transcription-polymerase chain reaction status of the sentinel lymph node were demonstrated to be the only significant prognostic factors for predicting disease-free survival. Tyrosinase reverse transcription-polymerase chain reaction for the detection of minimal residual melanoma in sentinel lymph nodes is a powerful tool to determine patients who are at increased risk for subsequent metastasis. Moreover, a group of patients with high tumor thickness was identified by negative reverse transcription-polymerase chain reaction to be at low risk for recurrent disease. These data may have an impact on future tumor classifications of primary cutaneous melanoma.

Correlation of positive RT-PCR for tyrosinase in peripheral blood of malignant melanoma patients with clinical stage, survival and other risk factors

The clinical value of the reverse transcription polymerase chain reaction (RT-PCR) assay for tyrosinase in peripheral blood of melanoma patients is still under debate. A total of 212 blood samples from 212 melanoma patients in all clinical stages (AJCC) were examined. Erythrocytes were lysed prior to RNA extraction by phenol precipitation from 2.7 ml of blood. cDNA for tyrosinase PCR was synthesized using random hexamers. Positive tyrosinase RT-PCR results were obtained in 11% of 106 stage I patients, 18% of 56 stage II patients, 31% of 26 stage III patients and 67% of 24 stage IV patients. After a median follow-up of 36 months (range 26-41), stage III patients with positive RT-PCR for tyrosinase had a shortened disease-free interval as compared to negative patients (P < 0.01). In stage IV patients, median overall survival was 8 months in case of a positive RT-PCR in contrast to 12 months in case of a negative test. While univariate analysis showed sex and primary tumour location associated with positive RT-PCR, multiple regression analysis revealed clinical stage and detection of tyrosinase transcripts in peripheral blood as best prognostic factors. Hazard ratios for disease-free survival were 19.7 (confidence interval (CI) 8.53-45.5, P = 0.0001) for metastatic vs primary disease and 2.96 (CI 1.49-5.89, P = 0.002) for positive vs negative tyrosinase RT-PCR. The corresponding hazard ratios for overall survival were 97.0 (CI 12.7-741, P = 0.0001) and 4.33 (CI 1.69-11.1, P= 0.002). Our results emphasize the importance of tyrosinase RT-PCR testing in peripheral blood.

Sentinel node biopsies in melanoma patients: a protocol for accurate, efficient, and cost-effective analysis by preselection for immunohistochemistry on the basis of Tyr-PCR

BACKGROUND

Immunohistochemistry (IHC) of serial sectioning is considered the gold standard for detection of melanoma activity in sentinel node (SN) biopsies. However, this is cost and labor intensive. In contrast, tyrosinase reverse transcription-polymerase chain reaction (RT-PCR) is simple and quick, but it is hampered by its extreme sensitivity. This study was performed to test whether a strategy that combines the two methods, using tyrosinase RT-PCR to preselect nodes for IHC, could be accurate and cost effective.

METHODS

In 36 patients, SNs were identified by scintigraphy and patent blue uptake. Of each SN, one cross section was analyzed first by hematoxylin and eosin staining. Next, all nodes were examined by serial sectioning and IHC of one-half and tyrosinase RT-PCR of the other. Before comparison, all results were documented in a blinded manner. Material costs and workload estimates were noted per SN.

RESULTS

Fifty-five SNs were retrieved from the 36 patients. Hematoxylin and eosin staining of the first cross section revealed tumor positivity in 3 patients (6 SN). Tyrosinase RT-PCR was positive in 11 of the remaining 33 patients (19 of 49 SN). Of these same 11 patients, only 5 were shown to have tumor-positive SNs by using IHC on serial sections (7 SN). All these nodes had been positive for tyrosinase on PCR. For IHC, an average of 40 sections were prepared and examined per SN at a cost of $200(U.S.)/SN. In contrast, routine tyrosinase RT-PCR costs $37(U.S.)/SN, and takes 5% of the time necessary for IHC. A strategy including hematoxylin and eosin staining on the first cross section, followed by tyrosinase RT-PCR on half of each negative (half) node, could preselect nodes to be taken through serial sectioning. In these series, such a strategy would have prevented serial sectioning and IHC of 30 SN from 22 patients. Apart from a considerable gain in efficiency, this would have reduced material costs by a minimum of $6000 (U.S.). This discrepancy would be even higher if work intensity of analysts and pathologists were considered.

CONCLUSIONS

In routine analysis of SN biopsies in melanoma patients, tyrosinase RT-PCR can be used effectively to preselect nodes for further IHC of serial sections. This method seems both time and cost effective.

Molecular detection of low-level disease in patients with cancer

The accurate detection of low-level disease in patients with cancer is essential to improve the staging of disease and consequently to define appropriate treatment strategies. Most methods currently used for staging are based on imaging studies and histological and immunocytochemical analysis of tissues such as bone marrow aspirates, or antibody assays for marker proteins secreted into the circulation. These methods have limited sensitivity. However, assays for nucleic acid-based markers may be valuable tools for the sensitive detection, assessment, and monitoring of disease status in asymptomatic cancer patients. Application of these methods may allow the early detection of cancer, when the tumour burden is smaller and the disease potentially more curable. The last decade has seen the application of polymerase chain reaction (PCR)-based methods to the detection of tumour in a wide variety of compartments, including peripheral blood, bone marrow, lymph nodes, urine, sputum, faeces, pancreatic juice, and more recently plasma. Molecular detection of disease by PCR has targeted DNA and RNA markers, including mutations, microsatellites, and tissue-specific gene expression. It is likely that these molecular methods will provide important clinical information, though their current clinical utility remains unclear. The current status of nucleic acid-based assays for the detection and assessment of disease status in the management of patients with solid tumours is reviewed.

Detection of circulating tumour cells in patients with breast or ovarian cancer by molecular cytogenetics

Detection of micrometastases in patients with solid tumours may aid the establishment of prognosis and development of new therapeutic approaches. This study was designed to investigate the presence and frequency of tumour cells in the peripheral blood (PB) of patients with breast or ovarian cancer by using a combination of magnetic activated cell sorting (MACS) and fluorescence in situ hybridization (FISH). Separated tumour cell and PB-samples from 48 patients (35 breast cancers, 12 ovarian tumours, one uterine sarcoma) were analysed for the presence of numerical aberrations of chromosomes 7, 12, 17 and 17 q11.2-q12. Twenty-five patients had primary disease and 23 had relapsed. The technique allows the detection of one tumour cell in 106 normal cells. Circulating tumour cells were detected in 35/48 cases (17 patients had relapsed and 13 primary carcinoma with lymph node or solid metastases) by the expression of anti-cytokeratin and the presence of numerical chromosomal abnormalities. PB-tumour cells of patients with a primary carcinoma and without solid metastases had a significantly lower percentage of chromosomal aberrations, especially for chromosome 12 (P = 0.035; P = 0.038) compared to those with relapsed disease and solid metastases. Detection and quantification of minimal residual disease may monitor the response to cytotoxic or hormonal therapy and may identify women at risk of relapse.

Tyrosinase gene expression in clear cell sarcoma indicates a melanocytic origin: insight from the first reported canine case

The aim of this study was to characterize a metastasizing soft tissue tumor in a dog, which clinically, grossly and histologically showed a close resemblance to human clear cell sarcoma, a soft tissue variant of malignant melanoma. Ultrastructurally, melanosomes were found, indicating a melanocytic origin of the tumor. Using reverse-transcription polymerase chain reaction, expression of the gene encoding tyrosinase was determined in tumor cells. With this first case of canine clear cell sarcoma, as well as the earlier report from our laboratory on amelanotic melanomas in the cat, we demonstrate that expression of the tyrosinase gene may occur in a broader range of less differentiated melanocytic tumors in different species, including man.

Melanoma-inhibiting activity (MIA) mRNA is not exclusively transcribed in melanoma cells: low levels of MIA mRNA are present in various cell types and in peripheral blood

The detection of minimal amounts of melanoma cells by tyrosinase reverse transcription polymerase chain reaction (RT-PCR) is seriously hampered by false negative reports in blood of melanoma patients with disseminated melanoma. Therefore, additional assays which make use of multiple melanoma markers are needed. It has been shown that introduction of multiple markers increases the sensitivity of detection. Melanoma inhibitory activity (MIA) is one such melanoma-specific candidate gene. To test the specificity of MIA PCR, we performed 30 and 60 cycles of PCR with two different sets of MIA specific primers on 19 melanoma and 16 non-melanoma cell lines. MIA mRNA was detected in 16 out of 19 melanoma cell lines and in seven out of 16 non-melanoma cell lines after 30 cycles of PCR. However, MIA mRNA could be detected in all cell lines after 60 cycles of PCR. Also, in 14 out of 14 blood samples of melanoma patients, five out of six blood samples of non-melanoma patients and in seven out of seven blood samples of healthy volunteers, MIA mRNA was detected after 60 cycles of PCR, whereas no MIA PCR product could be detected in any of the blood samples after 30 cycles of PCR. We conclude that low levels of MIA transcripts are present in various normal and neoplastic cell types. Therefore, MIA is not a suitable marker gene to facilitate the detection of minimal amounts of melanoma cells in blood or in target organs of the metastatic process.

Detection of melanoma micrometastases in the sentinel lymph node and in nonsentinel nodes by tyrosinase polymerase chain reaction

The aim of our study was to investigate the metastatic pathways of melanoma cells in sentinel and other regional lymph nodes. The term "sentinel lymph node" means that the first lymph node of the draining site of a primary tumor is never bypassed in malignant melanoma. In this case lymph node dissection would be necessary only when melanoma cells are detected in the sentinel node. Tyrosinase reverse transcriptase-polymerase chain reaction was applied to search for metastatic melanoma in the sentinel lymph node and in further lymph nodes of a complete lymph node basin in patients who underwent lymph node dissection. In 24 patients with malignant melanoma the draining site of the tumor was marked by lymphoscintigraphy and by intraoperative injection of patent blue V in the area around the primary tumor. The lymph nodes of the affected basin were excised and prepared for histopathologic, immunohistochemical, and molecular biologic examinations. Regarding the sentinel lymph node, 10 of 24 patients showed morphologic evidence for metastases, three additional patients showed only tyrosinase transcripts. In 11 of these 13 cases we found one or more nonsentinel lymph nodes with morphologically detectable melanoma cells and/or tyrosinase mRNA. Interestingly, in seven of 24 patients a positive tyrosinase reverse transcriptase-polymerase chain reaction was received in nonsentinel lymph nodes, whereas the sentinel lymph node was negative, not only for all histologic examinations but also by tyrosinase reverse transcriptase-polymerase chain reaction. In five of seven patients of the latter group, gp100 reverse transcriptase-polymerase chain reaction was carried out, showing also gp100 mRNA in nonsentinel lymph nodes only. Our data indicate that the concept of the sentinel lymph node may miss micrometastases. Whether such micrometastases cause a recurrence or a metastasis of malignant melanoma, or can be destroyed by the immune system, remains to be clarified.

Isolated organ perfusion does not result in systemic microembolization of tumor cells

BACKGROUND

Isolated organ perfusion with hyperthermia and melphalan with or without tumor necrosis factor-alpha has been effectively used to treat regionally confined, unresectable malignancies of both the limb and liver. Many patients, however, will eventually relapse at distant sites. We used reverse transcription-polymerase chain reaction (RT-PCR) to determine whether significant tumor microembolization occurs in patients undergoing isolated limb perfusion (ILP), isolated hepatic perfusion (IHP), or hepatic resection.

METHODS

Primers specific for the human tyrosinase gene or carcinoembryonic antigen gene were designed for RT-PCR to screen melanoma or colon adenocarcinoma, respectively. RNA from human melanoma lines (Pmel and 1286) and human colon adenocarcinoma lines (H508 and HT29) were used to generate positive control cDNA. Normal human blood was inoculated with tumor cells at concentrations that ranged from 10(-2) to 10(5) tumor cells/ml of blood to define the sensitivity. Systemic and perfusate blood samples were drawn from 15 patients (8 patients underwent IHP, 5 patients underwent ILP, and 2 patients underwent resection) before the start of the operation, immediately before and during the perfusion, and postoperatively. Mononuclear cell fractions were separated from the blood samples and RNA was extracted for the RT-PCR assay. Standard primers for human beta-actin were used to confirm that cDNA was generated after the RT reaction.

RESULTS

RT-PCR assay sensitivity was determined to be 10 tumor cells/ml of whole blood. Of the 8 IHP patients, 6 had colon metastases and 2 had ocular melanoma metastases to the liver. All 5 ILP patients had in transit melanoma of the extremity. Two patients with colon metastases to the liver were found to have resectable disease. There were no detectable circulating tumor cells in the systemic circulation either preoperatively or postoperatively in all 15 patients that were screened.

CONCLUSIONS

RT-PCR is a highly sensitive method of detecting tumor cells in perfusate or blood. Manipulation of the limb or liver followed by resection or isolated hyperthermic perfusion does not cause detectable release of circulating tumor cells. The late development of distant metastases observed in many of these patients does not correlate with the ability to measure circulating tumor cells during regional therapy.

Prognostic significance of occult metastases detected by sentinel lymphadenectomy and reverse transcriptase-polymerase chain reaction in early-stage melanoma patients

PURPOSE

Detection of micrometastases in the regional tumor-draining lymph nodes is critical for accurate staging and prognosis in melanoma patients. We hypothesized that a multiple-mRNA marker (MM) reverse transcriptase-polymerase chain reaction (RT-PCR) assay would improve the detection of occult metastases in the sentinel node (SN), compared with hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC), and that MM expression is predictive of disease relapse.

PATIENTS AND METHODS

Seventy-two consecutive patients with clinical early-stage melanoma underwent sentinel lymphadenectomy (SLND). Their SNs were serially sectioned and assessed for MAGE-3, MART-1, and tyrosinase mRNA expression by RT-PCR, in parallel with H&E staining and IHC, for melanoma metastases. MM expression in the SNs was correlated with H&E and IHC assay results, standard prognostic factors, and disease-free survival.

RESULTS

In 17 patients with H&E- and/or IHC-positive SNs, 16 (94%) expressed two or more mRNA markers. Twenty (36%) of 55 patients with histopathologically negative SNs expressed two or more mRNA markers. By multivariate analysis, patients at increased risk of metastases to the SN had thicker lesions (P =.03), were 60 years of age or younger (P <.05), and/or were MM-positive (P <.001). Patients with histopathologically melanoma-free SNs who were MM-positive, compared with those who were positive for one or fewer mRNA markers, were at increased risk of recurrence (P =.02). Patients who were MM-positive with histopathologically proven metastases in the SN were at greatest risk of disease relapse (P =. 01).

CONCLUSION

H&E staining and IHC underestimate the true incidence of melanoma metastases. MM expression in the SN more accurately reflects melanoma micrometastases and is also a more powerful predictor of disease relapse than are H&E staining and IHC alone.

Quantitative Reverse Transcription-PCR Assay with an Internal Standard for the Detection of Prostate-specific Antigen mRNA

Background: Circulating prostate cells can be detected with a reverse transcription-PCR (RT-PCR) assay for prostate-specific antigen (PSA) mRNA. We have developed a new quantitative RT-PCR method for measuring PSA mRNA.

Methods: The method uses a PSA-like internal standard (IS) mRNA that is added into the sample at the beginning of the RNA extraction and coamplified by RT-PCR with the PSA in the sample. After PCR amplification, the IS and PSA products are selectively detected by hybridization in a microtitration plate using probes labeled with fluorescent europium chelates.

Results: The method was validated with PSA and IS mRNAs and PSA-expressing cells to obtain a detection limit of 50 PSA mRNA copies (i.e., signal 2 times the mean of zero signal), linearity up to 106 copies, and detection of a single PSA-expressing cell. In preliminary evaluations, 60% (n = 10) of the prostate cancer patients with skeletal metastases gave results above the detection limit (500 PSA mRNA copies in 5 mL of blood). The total number of PSA copies ranged from 900 ± 200 to 44 100 ± 4900 (mean ± SD) in the samples, corresponding to ∼1–100 PSA-expressing cells in 5 mL of blood. In the controls (n = 34), none of the healthy females and 2 of 19 healthy males had detectable PSA mRNA [700 ± 100 and 2000 ± 900 (mean ± SD) PSA mRNA copies in 5 mL of blood for the 2 males].

Conclusions: The assay provides sensitive and quantitative detection of PSA mRNA expression from blood samples and can be used to establish the clinically significant number of PSA mRNA copies in prostate cancer.

Molecular detection of tumour DNA in serum and peritoneal fluid from ovarian cancer patients

We have analysed DNA extracted from the serum and peritoneal fluid of 20 ovarian cancer patients for the presence of tumour-specific genetic alterations. The 20 patients included six with stage Ia disease. Using six polymorphic microsatellite loci we were able to detect novel alleles or loss of heterozygosity in 17/20 serum samples and 12/19 peritoneal fluid samples. Tumour-specific abnormalities were detected in the serum of all but one of the stage Ia cases. Half of the occurrences of loss of heterozygosity identified in primary tumour material were detectable in the serum samples. Novel alleles indicative of microsatellite instability were found in 3/6 patients with stage Ia disease but in only 1/14 of patients with more advanced disease. One of the eight patients in the control group displayed abnormalities in her serum DNA. The ease with which tumour-specific alterations were detected in serum and peritoneal samples from ovarian cancer patients, using a panel of only six polymorphic microsatellite markers on four chromosomes, suggests that molecular detection methods could prove useful in the staging, monitoring and screening of this disease.

MART-1 is expressed less frequently on circulating melanoma cells in patients who develop distant compared with locoregional metastases

PURPOSE

Polymerase chain reaction (PCR) with tyrosinase and with MART-1 permits detection of small numbers of circulating melanoma cells (CMCs) in patients who have undergone surgical resection of localized disease. In a previous study, we showed that PCR with MART-1 had sensitivity and specificity similar to those of PCR with tyrosinase in terms of detection of CMCs but that PCR with MART-1 seemed to identify a different but overlapping subgroup of patients. In the current study, we examined the utility and prognostic significance of PCR with tyrosinase and with MART-1.

PATIENTS AND METHODS

We analyzed the prognostic significance of the patterns of expression of tyrosinase and MART-1 in 186 patients followed sequentially before and after surgical removal of American Joint Committee on Cancer stage I, II, or III melanoma.

RESULTS

PCR with tyrosinase and with MART-1 in the first 3 months after surgery identified 68.5% of 73 patients who developed recurrence in the 2-year period after surgery. Approximately 35% of patients with positive tests remained disease-free at 2-year follow-up. We found that patients with disseminated recurrence had a significantly lower incidence of MART-1-positive CMCs (16%) than of tyrosinase-positive CMCs (63%). Patients with locoregional metastases had CMCs that expressed tyrosinase and MART-1 at similar rates. These differences in expression of the markers in patients with disseminated recurrence were also associated with a much lower disease-free survival, in those who had CMCs that were positive for tyrosinase but negative for MART-1. The reverse applied in those with locoregional disease.

CONCLUSION

These findings suggest that PCR with MART-1 and with tyrosinase identifies subgroups of patients who develop disseminated or locally recurrent metastases. We hypothesize that immune responses against MART-1 may reduce the establishment of disseminated metastases.