Update of diagnostic and prognostic markers in cutaneous malignant melanoma

Molecular mechanisms and clinical implications of reversible protein S-glutathionylation

Sulfhydryl chemistry plays a vital role in normal biology and in defense of cells against oxidants, free radicals, and electrophiles. Modification of critical cysteine residues is an important mechanism of signal transduction, and perturbation of thiol-disulfide homeostasis is an important consequence of many diseases. A prevalent form of cysteine modification is reversible formation of protein mixed disulfides (protein-SSG) with glutathione (GSH). The abundance of GSH in cells and the ready conversion of sulfenic acids and S-nitroso derivatives to S-glutathione mixed disulfides suggests that reversible S-glutathionylation may be a common feature of redox signal transduction and regulation of the activities of redox sensitive thiol-proteins. The glutaredoxin enzyme has served as a focal point and important tool for evolution of this regulatory mechanism, because it is a specific and efficient catalyst of protein-SSG deglutathionylation. However, mechanisms of control of intracellular Grx activity in response to various stimuli are not well understood, and delineation of specific mechanisms and enzyme(s) involved in formation of protein-SSG intermediates requires further attention. A large number of proteins have been identified as potentially regulated by reversible S-glutathionylation, but only a few studies have documented glutathionylation-dependent changes in activity of specific proteins in a physiological context. Oxidative stress is a hallmark of many diseases which may interrupt or divert normal redox signaling and perturb protein-thiol homeostasis. Examples involving changes in S-glutathionylation of specific proteins are discussed in the context of diabetes, cardiovascular and lung diseases, cancer, and neurodegenerative diseases.

Bcl-2 expression is not associated with survival in metastatic cutaneous melanoma: a historical cohort study

Background

Programmed cell death (apoptosis) has been implicated in tumor development and may affect the metastatic potential of tumor cells. The role of bcl-2, a proto-oncogene that inhibits apoptosis, has been studied in several malignancies, including cutaneous melanoma (CM). The purpose of this study was to evaluate the immunohistochemical expression of bcl-2 in 35 regional lymph node, 28 subcutaneous and 17 visceral CM metastases, correlating the findings with patient survival.

Methods

In a historical cohort study patient survival was correlated with the expression of bcl-2 in regional lymph node, subcutaneous and visceral metastases of CM. Eighty slides containing surgical specimens from 50 patients diagnosed with stage III and IV CM, 28 male (56%) and 22 female (44%), were analyzed. Mean age at diagnosis was 43 years (16–74 years; median = 42 years). Mean Breslow depth was 5.01 mm (0.4–27.5 mm). The slides were submitted to immunohistochemical reaction using anti-bcl-2 monoclonal antibody and classified according to the degree of staining (< 5%; 5 to 50%; or > 50% of tumor cells stained). The relationship between bcl-2 protein expression and survival for each type of metastasis, gender and age at initial diagnosis was analyzed.

Results

Mean overall survival was 33.9 months after the diagnosis of the initial metastatic lesion (range: 0 to 131 months). Twenty-four out of 50 patients (48%) had died from CM by the end of the study period. bcl-2 expression was detected in 74.3, 85.7 and 82.4% of lymph node, subcutaneous and visceral metastases, respectively. After univariate and multivariate analyses, no correlation was found between positive bcl-2 expression and overall survival for the types of metastases evaluated.

Conclusion

The immunohistochemical expression of bcl-2 in metastasis alone is not a prognostic marker for CM.

Molecular diagnostics in melanoma

Molecular pathology is rapidly evolving, featuring continuous technologic improvements that offer novel clinical opportunities for the recognition of disease predisposition, for identifying sub-clinical disease, for more accurate diagnosis, for selecting efficacious and non-toxic therapy, and for monitoring of disease outcome. Currently, the identification and prognosis of primary cutaneous melanoma is based on histologic factors (tumor depth and ulceration) and clinical factors (number of lymph node and/or distant metastases). However, metastasis can occur in patients with thin melanomas, and sentinel lymph node biopsy does not identify all patients at risk for distant metastasis. New markers exist that correlate with melanoma progression, which may aid in melanoma identification, prognostication, and detection of minimal residual disease/early recurrence. Moreover, not many therapeutic options exist for melanoma as no regimen prolongs survival. Emerging data with investigational therapies suggest that certain markers might play a crucial role in identifying patients who will respond to therapy or show utility in the monitoring the response to therapy. Herein, molecular diagnostics that can potentially benefit the individual melanoma patient will be discussed.

Long term follow-up of c-myc, p53 and proliferation measurements in malignant melanoma

AIMS

We report a prospective study examining the prognostic significance of the c-myc oncoprotein, p53 tumour suppressor gene and proliferation rate measurements in malignant melanoma.

METHODS

Flow cytometry (FCM) was used to measure the expression of c-myc, p53 and proliferation parameters in patients who had received an injection of the thymidine analogue bromodeoxyuridine prior to surgery.

RESULTS

Sixty-seven patients had successful FCM measurements of the three parameters. c-myc was detected in 97% of patients with a median cell positivity of 62%. The median p53 positivity was 13%. The median potential doubling time (T(pot)) of the tumours wasf 9.4 days. In univariate analysis, each of the parameters showed an association with survival in metatstatic disease with rapid proliferation (p=0.006) or overexpression of c-myc (p=0.038) related to poor survival whereas increased positivity for p53 predicted better survival (p=0.013).

CONCLUSIONS

These data indicate that laser cytometric technology can be used to obtain quantitative data on oncoproteins expression and cell proliferation rates in clinical samples of malignant melanoma.

The role of Bcl-2 family members in the progression of cutaneous melanoma

The overwhelming problem of cutaneous melanoma is chemoresistance. Subversion of the biochemical changes that lead to chemoresistance intersects the apoptosis pathways. The mitochondrion has been a focal point of this intersection for the development of therapeutic strategies aimed at reducing the progression of melanoma. The Bcl-2 family of apoptotic regulators is arguably the most pivotal component to this mitochondrial response. The shear number of studies conducted on the relationship between melanoma and Bcl-2 members prompted us to evaluate the literature available and discern some rational utility of the data. We have found that there are striking inconsistencies for the expression of Bcl-2 family proteins with melanoma progression, particularly for Bcl-2. Roughly one-third of the data suggests an increase in Bcl-2 expression with advancing melanoma, while another third suggests a decrease. Furthermore, the remaining third found on the whole, a detectable level of Bcl-2 in all tissues of melanocytic origin. These discrepancies are difficult to rectify in light of the apparent success of recent clinical trials utilizing Bcl-2 antisense strategies. The general consensus in the literature is that pro-apoptotic Bax is decreased with melanoma progression while anti-apoptotic Bcl-xL and Mcl-1 appear to increase with progression. We suggest that the biochemical techniques being used for analysis present too great of a heterogeneity, which could be mitigated with more standard procedures and reagents. Finally the utility of 'multi-specific' antisense tactics could be a more effective way of targeting advanced melanoma disease.

Melanoma cutâneo: características clínicas, epidemiológicas e histopatológicas no Hospital Universitário de Brasília entre janeiro de 1994 e abril de 1999

FUNDAMENTOS: A incidência do melanoma cutâneo tem aumentado cerca de 4 a 6% anualmente. Esse tumor ocorre preferencialmente no sexo feminino, entre 30 e 79 anos de idade e predominantemente em indivíduos de cor branca. A forma anatomopatológica mais freqüente é a extensivo-superficial, e sua localização varia com o sexo. OBJETIVOS: O objetivo deste estudo foi avaliar as características clínicas, epidemiológicas e histológicas do melanoma cutâneo primário, no Hospital Universitário de Brasília, em um período de cinco anos. MATERIAL E MÉTODOS: Foi realizado estudo de revisão dos prontuários dos casos de melanoma cutâneo primário, do Hospital Universitário de Brasília, diagnosticados e tratados entre janeiro de 1994 e abril de 1999, totalizando 32 casos. Os pacientes foram analisados, caracterizando-se a distribuição do tumor por sexo, idade, cor da pele, topografia, sintomatologia, tipo de crescimento, nível de Clark, índice de Breslow e presença de metástases. A análise dos dados foi realizada por meio de estatística simples e pelo teste do qui-quadrado (chi2). RESULTADOS: Neste estudo há predomínio das lesões localizadas nos membros, correspondendo a 16 pacientes (50%). Em nove pacientes (45%) a forma primária era do tipo nodular, e 17 pacientes (58,6%) não apresentavam queixas. Pela correlação entre a presença ou não de metástases e o nível de Clark observou-se que os pacientes com nível de invasão até o subcutâneo (Clark V) apresentaram risco relativo de 2,94 (1,24<ic<6,99). CONCLUSÃO: O perfil clínico, epidemiológico e histológico do paciente portador de melanoma cutâneo primário do Hospital Universitário de Brasília entre janeiro de 1994 e abril de 1999 corresponde ao indivíduo do sexo feminino, idoso (de 61 a 80 anos), cor da pele branca, cuja lesão predomina nos membros, sendo mais freqüente o tipo de crescimento nodular e que não apresenta sintomas à época do diagnóstico.

Genotypic analysis of primary and metastatic cutaneous melanoma

Microdissection genotyping was performed on 16 cases of melanoma, including two cutaneous and one lymph node metastases. Three benign nevi were used as controls. Where possible, tumor was microdissected at several sites. Genotyping involved assessment of loss of heterozygosity [LOH]), which was accomplished using a panel of nine polymorphic tetranucleotide microsatellites. Polymerase chain reaction was performed on the normal tissue sample to establish microsatellite heterozygous status. Informative markers were then tested on microdissected lesional tissue and scored for the presence and extent of allelic imbalance (AI). Microsatellite informativeness varied from 33% to 66%. Benign nevi were without AI. All invasive melanomas manifested acquired allelic loss, which involved 75% or 100% of the markers shown to be informative for each subject. Eleven of 13 (84%) primary melanomas demonstrated intratumoral heterogeneity of AI consistent with development of tumor subclones with differing genotypic profiles within thin as well as thick melanomas. Although a consistent pattern did not emerge among the markers, LOH of 9p21 (D9S254) occurred in 60% (9/15) of the cases followed by 40% of cases displaying LOH of 1p34, p53, 10q (MXI1), and 10q23 (D10S520) and 25% with 5q21 (D5S 592) abnormalities. A third of the cases including the metastatic foci demonstrated two different patterns of AI affecting alternative alleles of the same genomic marker within different parts of the melanoma. Two melanomas in situ did not display LOH of any markers in the informative cases although the in situ component in the invasive tumors had allelic losses that were in part similar to the invasive areas. The results of this study support the expanded use of microdissection genotyping and explore other markers to define the unique mutational profile for malignant melanoma that may complement other histologic characteristics of melanoma.

Immunohistochemical markers of melanocytic lesions: a review of their diagnostic usefulness

We critically reviewed recent literature reports of 25 melanocytic immunohistochemical markers. This review organizes and summarizes the many new studies of old and novel melanocytic markers and identifies the most promising diagnostic immunohistochemical markers that can be used to distinguish melanocytic from nonmelanocytic lesions and benign melanocytic from malignant melanocytic lesions.

Expression of CD40, CD44, bcl-2 antigens and rate of cell proliferation on fine needle aspirates from metastatic melanoma

The clinical behaviour of melanoma is often unpredictable using clinical and histological criteria. Tumour cell markers related to cell cycle regulation, apoptosis, cell-cell interactions and cell proliferation might improve the possibility of predicting the clinical course of melanoma. The aim of the present study was to refine prognostic criteria by an immunocytochemical investigation of CD44, CD40, bcl-2 antigens and cell proliferation in tumour cells aspirated from metastases of malignant melanoma. CD40 is a cell surface receptor shown to be expressed by lymphomas as well as carcinomas, and is thought to play a central role in the process of tumour progression. CD44 is a transmembrane glycoprotein, which is involved in growth signal transmission of importance in the binding of tumour cells to endothelium, cell migration and enhancement of cell motility, which makes it of interest to study in relation to the metastasizing capacity of tumours. The bcl-2 protein is active in the process of programmed cell death (apoptosis) as an antiapoptotic agent and its expression may reflect tumour progression. Mean/median percentages of tumour cell positivity were 8.5/3.0 for CD40, 76.1/86.3 for CD44 and 7.4/3.3 for bcl-2. A significant correlation was observed between expression of apoptosis-associated bcl-2 antigen and overall survival (r = 0.33). The CD44 positive cell fraction was higher in patients with short overall survival than those with long survival but this difference was not statistically significant. The expression of CD40 did not correlate with overall survival. The mean/median proliferation fraction assessed by MIB-1 monoclonal antibody was 25.8/23.9 and showed a significant correlation with survival after diagnosis of melanoma metastasis (r = 0.32). Lack of bcl-2 expression and a high proportion of tumour cells expressing Ki-67 antigen are predictors of poor prognosis that are independent of the traditionally accepted Breslow's thickness of the primary melanomas.

Cysteine and indole derivatives as markers for malignant melanoma

Malignant melanoma is a skin tumour, which carries a very unfavourable prognosis. The early detection of a melanoma and even more its metastasis is of decisive importance for the survival prognosis of the patients. So there is always a desire for simple, economical and meaningful serological markers. From the cysteine- and indole-related derivatives, 5-S-cysteinyldopa (5-SCD) and 6-hydroxy-5-methoxy-indole-2-carboxylic acid (6H5MI2C) are the most important substances for this purpose. For 5-SCD, the sample pretreatment was carried out either by a manual extraction onto alumina, by an automated method onto boronic acid affinity gels or by an automated solid-phase extraction. For 6H5MI2C, liquid-liquid extractions or direct injection techniques were applied. The chromatographic analyses in the early years were mostly performed with GC-MS. Today HPLC is the nearly exclusively used separation technique. For HPLC, standard RP18 separating columns and usual compositions of eluents were applied. As detectors both the ECD and the FD showed a sufficient sensitivity and selectivity. 5-SCD and 6H5MI2C are very sensitive to light and oxidation. These properties must be taken into account in the complete analysis procedure, including the sample collection, otherwise false low values will result especially for plasma samples. For a critical discussion of the analytical methods and still more for the interpretation of the obtained results, the detailed analytical procedures must be considered. 5-SCD in plasma is one of the best markers of malignant melanoma. It shows an excellent specificity and also an adequate sensitivity in the metastatic melanoma stages. For the detection of primary melanomas and for urine instead of plasma samples, the sensitivity of 5-SCD is generally lower. Altogether, the sensitivity of this parameter is not yet sufficient. 6H5MI2C and other indole derivatives have been investigated far less than 5-SCD. 6H5MI2C correlates less clearly with the different stages of the melanoma and is therefore a less suitable marker. To improve the sensitivity of the findings, in future the investigations should be performed as multi-marker analysis with the simultaneous measurements of more than one marker substance in a given patient sample. Not only one measurement should be carried out per patient, it would be more meaningful to observe the patients with laboratory diagnostics in the follow-up.

Transcription factors and other dysregulated proteins in melanoma prognosis

Approximately one third of patients with cutaneous melanoma later develop a metastatic disease, having then an extremely poor rate of survival. Because of the highly unpredictable nature of melanomas, finding those patients who are likely to develop a metastatic disease and those patients who probably will survive is an ongoing challenge. The current "conventional" prognosticators, such as Breslow thickness, Clark level of invasion, and ulceration, cannot perfectly predict the clinical course of this disease at an individual level. Although the sentinel lymph node biopsy procedure and reverse transcription polymerase chain reaction techniques have significantly improved the staging of patients with melanoma, new molecular prognostic markers may help in selection of appropriate patients for strenuous adjuvant therapies and for randomized clinical trials. Furthermore, these markers also improve our basic understanding of the biology of cutaneous melanoma, potentially offering new targets for novel treatment strategies. This paper reviews the current literature on transcription factors and other dysregulated proteins involved in melanoma prognosis.

Update on genetic events in the pathogenesis of melanoma

Melanoma is the most common fatal malignancy among young adults, and its incidence and mortality continue to increase at an alarming rate. Epidemiologic studies have clearly demonstrated roles for genetic predisposition and sun exposure in melanoma development. In the past few years, substantial information has been added to the body of evidence suggesting that inherited and somatic genetic events contribute to the pathogenesis of melanoma. This review focuses on recent advances in the understanding of the genetic events, particularly aberration of cell cycle control and transcriptional control mechanisms, implicated in the pathogenesis of melanoma.

Structure, expression and chromosome mapping of MLZE, a novel gene which is preferentially expressed in metastatic melanoma cells

We isolated a novel gene, termed MLZE, from a B16-BL6 cDNA library after subtraction of B16-F10 mRNA. Expression levels of mouse MLZE (mMLZE) increased in accordance with metastatic ability of B16 melanoma sublines. Human homolog of mMlze (hMlze) contained one leucine zipper structure and two potential nuclear localizing signals. Northern blot analysis of multiple human tissues showed that hMLZE was expressed primarily in trachea and spleen. We mapped the hMLZE gene (by fluorescence in situ hybridization) to 8q24.1 - 2, which contains the c-myc gene and is often amplified in malignant melanoma. Immunohistochemistry revealed that the number of hMlze-positive cases was significantly larger in Clark levels III, IV and V melanomas (6 / 11 = 55%) than in Clark levels I and II melanomas (2 / 15 = 13%). In two cases of hMlze-positive melanomas, the strength of hMlze staining increased substantially in the deep component of the tumor. Considering that melanomas above Clark level II are more metastatic than those below Clark level III, these findings suggested that MLZE is one of the genes whose expression is upregulated during the course of acquisition of metastatic potential in melanoma cells.

Erythropoietin receptor expression in human melanoma cells

Erythropoietin is well known for its role in the control of erythropoiesis, where it acts by binding to its cognate receptor (EpoR) on the surface of erythroid progenitor cells. Here we present the novel finding that the EpoR is also expressed in cells of the melanocytic lineage. It is expressed in transformed cell lines established from normal melanocytes and also in established human melanoma cell lines derived from melanoma metastases, but not in normal primary human melanocytes. The analysis of individual subclones isolated from spontaneously transformed melanocytes revealed that approximately 50% of all the clones examined expressed the EpoR. Further analysis of the individual growth characteristics of EpoR-positive and EpoR-negative clones indicated that, under standard cell culture conditions, expression of the receptor did not affect cell growth. Expression of this receptor is consequently most likely driven by an event that is associated with, but not absolutely required for, the transformed phenotype. While the definite function of this receptor in melanoma cells is still unknown and additional studies are required, our findings support the hypothesis that the EpoR may serve as a progression marker for human melanoma. This observation might be useful in the early diagnosis of melanoma.