Expression of tyrosinase, MIA and MART-1 in sentinel lymph nodes of patients with malignant melanoma

Skin layer-specific Melan-A expression during progression of human cutaneous melanoma: implications for diagnostic applications of the marker

Melan-A is widely used in the diagnostics of human melanoma. The immunogenicity of this glycoprotein makes it a potential target in immunotherapy and several authors have suggested its potential as a prognostic factor. Up to now there has been no clear direct evidence of changes of Melan-A expression during the progression of melanoma. We have performed objective immunohistochemical assessment of the expression of Melan-A in benign naevi and melanomas at different stages of progression. Our results show a complex pattern of changes in the expression of Melan-A in melanomas depending on the location of melanoma cells within individual skin layers. The expression of the antigen during tumour progression significantly decreases for melanoma cells located in the granular/spinous layer (r=-0.94, P=0.02) and increases for the papillary layer (r=0.99, P=0.002) and reticular layer (r=0.89, P=0.04). It should also be emphasized that from the Clark II level of progression the melanomas can be detected with high sensitivity and specificity using a simple cut-off test based on the determination of Melan-A expression in tumour cells located within the papillary layer.

Prospective Multi-Institutional Study of Reverse Transcriptase Polymerase Chain Reaction for Molecular Staging of Melanoma

Purpose

To evaluate the prognostic significance of molecular staging using reverse transcriptase polymerase chain reaction (RT-PCR) in detecting occult melanoma cells in sentinel lymph nodes (SLNs) and circulating bloodstream.

Patients and Methods

In this multicenter study, eligibility criteria included patient age 18 to 71 years, invasive melanoma ≥ 1.0 mm Breslow thickness, and no clinical evidence of metastasis. SLN biopsy and wide excision of the primary tumor were performed. SLNs were examined by serial-section histopathology and S-100 immunohistochemistry. A portion of each SLN was frozen for RT-PCR. In addition, RT-PCR was performed on peripheral-blood mononuclear cells (PBMCs). RT-PCR analysis was performed using four markers: tyrosinase, MART1, MAGE3, and GP-100. Disease-free survival (DFS), distant–DFS (DDFS), and overall survival (OS) were analyzed.

Results

A total of 1,446 patients with histologically negative SLNs underwent RT-PCR analysis. At a median follow-up of 30 months, there was no difference in DFS, DDFS, or OS between the RT-PCR–positive (n = 620) and RT-PCR–negative (n = 826) patients. Analysis of PBMC from 820 patients revealed significant differences in DFS and DDFS, but not OS, for patients with detection of more than one RT-PCR marker in peripheral blood.

Conclusion

In this large, prospective, multi-institutional study, RT-PCR analysis on SLNs and PBMCs provides no additional prognostic information beyond standard histopathologic analysis of SLNs. Detection of more than one marker in PBMC is associated with a worse prognosis. RT-PCR remains investigational and should not be used to direct adjuvant therapy at this time.

Diagnostic molecular markers in thyroid cancer

The use of molecular assays to analyze clinical tissues in the diagnosis and management of thyroid cancer, similar to other tumors, will likely allow for more accurate characterization of the aggressiveness of individual tumors and may allow for the early diagnosis of recurrence. The application of these methods to thyroid nodules and nodal metastases is less encumbered by difficulties arising from amplification of transcripts in non-thyroid cells. For these tissues, these assays are likely to be used clinically in the near-future. New data arising from cDNA arrays identifying novel markers of malignancy or tumor aggressiveness make this a growing area of interest. The use of molecular assays in diagnosing distant metastases is more problematic due to issues with ectopic expression of either full length or splice variants of genes thought to be thyroid-specific. Assay quantitation is a complex problem owing to variability in the level of expression of "housekeeping" genes and the variety of phlebotomy and RT-PCR methods reported. Additional research in this area is clearly required before a recommendation can be given regarding clinically applicability of these tests.

Pathologic assessment of melanoma sentinel nodes: a role for molecular analysis using quantitative real-time reverse transcription-PCR for MART-1 and tyrosinase messenger RNA

PURPOSE

Molecular analysis of melanoma sentinel nodes (SN) is sensitive, but poorly specific because metastases cannot be distinguished from benign nevus inclusions (BNI). We investigated whether quantitative reverse transcription-PCR (RT-PCR) detection of MART-1 and tyrosinase mRNAs could improve this specificity and contribute to SN assessment.

EXPERIMENTAL DESIGN

Two hundred twenty SNs from 95 melanoma patients analyzed by extensive immunohistopathology and real-time quantitative RT-PCR.

RESULTS

Using histopathology, SNs and patients were allotted to three diagnostic groups: (a) metastasis positive, (b) BNI positive, and (c) melanocyte-free. Median MART-1 and tyrosinase mRNA levels in SNs were significantly different in patients with metastasis compared with patients with BNIs (P < 0.05) and patients without melanocytic lesions (P < 0.001). However, a "gray-zone" was observed where distinction, based on mRNA levels, could not be made between the three groups. For both genes, the highest mRNA level recorded in each RT-PCR-positive patient was positively correlated with Breslow's tumor thickness. For SNs with metastases, tumor burden was significantly correlated to the mRNA level. Using the presence of a MART-1 RT-PCR signal to detect patients with metastases, a sensitivity of 100% and a negative predictive value of 100% were achieved when extensive immunohistology was used as reference.

CONCLUSIONS

Quantitative RT-PCR MART-1 and tyrosinase mRNA analysis cannot be used alone for SN diagnosis because of its poor specificity for melanoma metastasis. However, in approximately one third of cases without RT-PCR evidence of MART-1 expression, extensive histopathologic SN investigation is not necessary, thus substantially reducing the cost of SN analysis. The level of melanocyte-associated mRNA is associated with both tumor thickness and tumor burden as measured histopathologically, suggesting that this may be of prognostic value.

Quantification of melanoma mRNA markers in sentinel nodes: pre-clinical evaluation of a single-step real-time reverse transcriptase-polymerase chain reaction assay

Although reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of melanocyte-associated mRNA can detect sentinel node melanoma metastases, most published assays are semi-quantitative methods of unknown sensitivity and precision, unsuitable for clinical use. We describe a single-step real-time quantitative RT-PCR assay for MART-1 and tyrosinase mRNAs, suitable for sentinel node analysis in a clinical setting. Using serial dilutions of melanoma cell line SK-MEL-28 RNA in water as a calibrator, we obtained linear calibration curves covering the range 0.5 to 10,000 arbitrary units (SK-MEL-28 melanoma cell equivalents). The sensitivity limit was 0.32 (MART-1) and 5 (tyrosinase) arbitrary units. Analytical imprecision was between 11% and 34%. MART-1 PCR efficiency was unaffected when samples were diluted with negative lymph node RNA rather than water, whereas tyrosinase PCR efficiency was halved. To evaluate the clinical suitability of our assay, we quantified melanocyte mRNAs in sentinel nodes with histologically verified micrometastases (n = 10) and benign nevus inclusions (n = 10), and in sentinel nodes without evidence of intranodal melanocytes (n = 10). We found significant differences in median melanocyte-derived mRNA levels comparing the three types of lymph nodes, suggesting that this quantitative molecular protocol may increase assay precision and be useful for the clinical evaluation of sentinel nodes.

Detection of Melanoma Cells in Sentinel Lymph Nodes by Reverse Transcriptase-Polymerase Chain Reaction: Prognostic Significance

BACKGROUND

Recently reverse transcriptase-polymerase chain reaction (RT-PCR) has been proposed as a new sensitive method for the detection of submicroscopic melanoma nodal metastases. Sentinel lymph node (SLN) status is considered the most important prognostic factor for melanoma patients. Thus, in recent years, melanoma research has been focused on identifying new molecular markers of micrometastases.

METHODS

In this study, 129 SLNs were collected and analyzed by RT-PCR for tyrosinase and melanoma inhibitory activity (MIA) messenger RNA (mRNA) expression. RESULTS from PCR analysis were then compared with those obtained by hematoxylin and eosin and immunohistochemistry and related to progression of disease.

RESULTS

MIA gene expression was positive by RT-PCR in 27% of the tyrosinase-positive SLNs. When the correlation between tyrosinase and/or MIA mRNA expression and disease-free survival was evaluated by the Kaplan-Meier exact test, there was a statistically significant correlation between simultaneous tyrosinase and MIA gene expression in SLNs and progression of disease.

CONCLUSIONS

RT-PCR analysis for both MIA and tyrosinase mRNA may identify a subset of melanoma patients with a worse prognosis whom the routine methods, such as histology and immunohistochemistry, fail to identify because of the poor sensitivity of these methods.

Lineage infidelity of MDA-MB-435 cells: expression of melanocyte proteins in a breast cancer cell line

The origin of cell lines is critical in defining cell type-specific biological functions. Several reports suggested that the MDA-MB-435 cell line, a cell line extensively used for studying breast cancer biology, has a gene expression pattern most compatible with melanocyte origin. However, we demonstrate that MDA-MB-435 cells express breast-specific or epithelial-specific markers. Also, MDA-MB-435 cells were induced to express breast differentiation-specific proteins and secrete milk lipids as observed in other well-established breast cancer cell lines. Notably, MDA-MB-435 cells also expressed melanocyte-specific proteins as did another highly aggressive breast cancer cell line. MDA-MB-435 xenograft tissue sections stained entirely positive for epithelium-specific markers but only partially positive for melanocyte-specific markers. Thus, MDA-MB-435 is most likely a breast epithelial cell line that has undergone lineage infidelity.

RNA-transfected CD40-activated B cells induce functional T-cell responses against viral and tumor antigen targets: implications for pediatric immunotherapy

Vaccination with antigen-presenting cells (APCs) engineered to mimic mechanisms of immune stimulation represents a promising approach for cancer immunotherapy. Dendritic cell vaccines have entered phase 3 testing in adult malignancies, but such vaccines in children have been limited. We demonstrate that CD40-activated B cells (CD40-B) transfected with RNA may serve as an alternative vaccine that can be generated from small blood volumes regardless of patient age. CD40-B from pediatric patients are efficient APCs and can be loaded with RNA as an antigenic payload, permitting simultaneous targeting of multiple antigenic epitopes without the necessity of HLA matching. For viral and tumor antigens, CD40-B/RNA technology induced cytotoxic T lymphocytes (CTLs) from adults and children, which could be identified with peptide/major histocompatibility complex (MHC) tetramers. These CTLs secreted interferon-gamma (IFN-gamma) and killed targets in an MHC-restricted fashion. For pooled neuroblastoma RNA and autologous neuroblastoma RNA, CTLs that lysed neuroblastoma cell lines, including CTLs specific against the widely expressed tumor-antigen survivin, were generated. These findings support a novel platform for tumor-specific vaccine or adoptive immunotherapies in pediatric malignancies.

Tyrosinase RT-PCR as a Supplement to Histology for Detecting Melanoma and Nevus Cells in Paraffin Sections of Sentinel Lymph Nodes

The detection of tyrosinase mRNA in sentinel lymph nodes (SLNs) by reverse transcription polymerase chain reaction (RT-PCR) is a sensitive indicator for the presence of melanoma or nevus cells, but it does not enable a distinction between both. We have established an efficient method for extraction and reverse transcription of tyrosinase mRNA from paraffin sections that permits the close correlation of the RT-PCR results with (immuno)histologic findings in adjacent sections. One hundred fifty-three SLNs and 6 non-SLN specimens originating from 92 melanoma and 4 nonmelanoma patients were studied to test the reliability of this approach. The predictive value of positive RT-PCR results was 0.98 for the presence of melanoma or nevus cells; the corresponding negative predictive value was 0.83. Furthermore, the detection rate of tyrosinase mRNA significantly correlated with tumor burden. Among the 33 melanoma-positive SLNs without nevus cells, positive RT-PCR results were obtained in all specimens with extended peripheral (S2) or deeply invasive (S3) micrometastases but in only 46% of the cases with few localized melanoma cells in the subcapsular zone (S1). Routine (immuno)histologic evaluation alone had missed microclusters of melanoma cells in one SLN and small nevus cell aggregates in six other SLNs. They were detected only during microscopic reexamination caused by a positive RT-PCR result. We conclude that histology and immunohistochemistry remain the indispensable gold standard for the identification of melanoma and nevus cells in SLNs. Additional molecular analyses using adjacent paraffin sections may further improve the diagnostic accuracy by sensitizing and guiding the microscopist's attention.

Pathology of malignant melanoma

Understanding the fundamental aspects of the pathology of melanoma is crucial for the surgeon to deliver optimal care to the patient with melanoma. Pathology provides diagnostic data, offers prognostic information, and, to a large extent, directs management. This article reviews several aspects of the pathology of melanoma, with special relevance to the surgeon, including benign clinicopathologic simulators of melanoma, fundamental concepts of the pathology of melanoma, histopathologic prognostic factors of melanoma, approach to lymph nodes, and implications of the revised staging system.

Survivin, bcl-2, bax, and bcl-X gene expression in sentinel lymph nodes from melanoma patients

PURPOSE

The expression of apoptosis-related genes, such as survivin, bcl-2, bcl-X, and bax, has been evaluated by reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemistry in sentinel lymph nodes (SLNs) from melanoma patients and then correlated to the outcome of patients.

PATIENTS AND METHODS

Thirty-six SLNs were examined. After RNA extraction, an RT-PCR followed by Southern blot hybridization was performed to detect survivin, bcl-2, bcl-X, and bax mRNA. bcl-2, survivin, and bax gene expression was evaluated, whenever possible, also by immunohistochemistry at the protein level.

RESULTS

We found a significant correlation (P <.005) between survivin expression and outcome of patients; in fact, 61.5% of patients expressing survivin gene progressed or died because of the disease, whereas 38.5% are currently disease-free. Among patients negative for survivin expression, 100% are disease-free after a median follow-up time of 52.9 months. We did not find a significant correlation between bcl-2, bax, and bcl-X gene expression and outcome of patients. In fact, these genes were found equally expressed in patients with disease progression and in disease-free patients.

CONCLUSION

Our findings show a variable expression of apoptosis-related genes in SLNs of melanoma patients; more interestingly, we found that survivin expression correlates to outcome of patients in a statistically significant way, whereas the expression of other genes, such as bcl-2, bax, and bcl-X, did not seem to correlate to progression of disease. We suggest that the detection of survivin gene expression by RT-PCR in SLNs may be a useful prognostic indicator.