Immunohistochemical expression of cyclooxygenase-2 (COX-2) in oral nevi and melanoma

BACKGROUND

Cyclooxygenase-2 (COX-2) catalyses the conversion of arachidonic acid to prostaglandin, and its overexpression has been demonstrated in different malignant tumors, including cutaneous melanoma. However, no data about the expression of this protein in oral melanocytic lesions are available to date. The aim of this study was to evaluate the immunohistochemical expression of COX-2 in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions.

METHODS

COX-2 was evaluated by immunohistochemistry in 49 oral melanocytic lesions, including 36 intramucosal nevi and 13 primary oral melanomas, and in four cutaneous nevi and eight melanomas.

RESULTS

All cases of oral and cutaneous melanomas were positive for COX-2. On the other hand, all oral and cutaneous melanocytic nevi were negative.

CONCLUSION

COX-2 is highly positive in oral melanomas and negative in oral nevi and might represent a useful marker to distinguish melanocytic lesions of the oral cavity.

Dysregulation of redox-state-regulating enzymes in melanocytic skin tumours and the surrounding microenvironment

AIMS

To investigate redox-regulating enzymes that may have a special role in melanoma pathogenesis due to continuous exposure to microenvironment-produced and ultraviolet radiation-induced oxidative stress.

METHODS AND RESULTS

We assessed immunohistochemically the expression of antioxidant enzymes peroxiredoxins (Prxs) I-IV, sulfiredoxin (Srx) and redox-regulated proto-oncogene DJ-1 in material consisting of 30 benign naevi, 14 lentigo malignas and 67 malignant melanomas. Evaluation of immunostaining was performed with special attention paid to protein expression in different tumour compartments. In particular, the expression patterns of nuclear Prx I and Prx II and cytoplasmic DJ-1 were decreased significantly in melanomas compared with dysplastic and benign naevi. In multivariate analysis, several prognostic factors were identified: Prx III expression in the cytoplasm of stromal fibroblasts was associated with shortened melanoma-specific survival [hazard ratio (HR) 6.730; 95% confidence interval (CI) 1.579-28.689], while cytoplasmic Prx IV expression in endothelial cells (HR 6.563; 95% CI 1.750-24.620) and Srx expression in the cytoplasm of keratinocytes (HR 6.988; 95% CI 1.559-31.324) were associated with better prognosis independently of ulceration, thickness of melanoma or its diagnostic type.

CONCLUSIONS

Redox-regulating enzymes have the potential to serve as novel prognostic factors and targeting them may offer new therapeutic options in malignant melanoma.

Identification of small-molecule inhibitors of autotaxin that inhibit melanoma cell migration and invasion

Autotaxin (ATX) is a prometastatic enzyme initially isolated from the conditioned medium of human melanoma cells that stimulates a myriad of biological activities, including angiogenesis and the promotion of cell growth, survival, and differentiation through the production of lysophosphatidic acid (LPA). ATX increases the aggressiveness and invasiveness of transformed cells, and ATX levels directly correlate with tumor stage and grade in several human malignancies. To study the role of ATX in the pathogenesis of malignant melanoma, we developed antibodies and small-molecule inhibitors against recombinant human protein. Immunohistochemistry of paraffin-embedded human tissue shows that ATX levels are markedly increased in human primary and metastatic melanoma relative to benign nevi. Chemical screens identified several small-molecule inhibitors with binding constants ranging from nanomolar to low micromolar. Cell migration and invasion assays with melanoma cell lines show that ATX markedly stimulates melanoma cell migration and invasion, an effect suppressed by ATX inhibitors. The migratory phenotype can be rescued by the addition of the enzymatic product of ATX, LPA, confirming that the observed inhibition is linked to suppression of LPA production by ATX. Chemical analogues of the inhibitors show structure-activity relationships important for ATX inhibition and indicate pathways for their optimization. These studies suggest that ATX is an approachable molecular target for the rational design of chemotherapeutic agents directed against malignant melanoma.

mTOR is activated in the majority of malignant melanomas

The objective of this study was to determine whether activation of the kinase mammalian target of rapamycin (mTOR) is associated with human melanoma. We found moderate or strong hyperphosphorylation of ribosomal protein S6 in 78/107 melanomas (73%). In contrast, only 3/67 benign nevi (4%) were moderately positive, and none were strongly positive. These data indicate that mTOR activation is very strongly associated with malignant, compared to benign, melanocytic lesions. Next, we tested six melanoma-derived cell lines for evidence of mTOR dysregulation. Five of the six lines showed persistent phosphorylation of S6 after 18 hours of serum deprivation, and four had S6 phosphorylation after 30 minutes of amino-acid withdrawal, indicating inappropriate mTOR activation. The proliferation of three melanoma-derived lines was blocked by the mTOR inhibitor rapamycin, indicating that mTOR activation is a growth-promoting factor in melanoma-derived cells. mTOR is directly activated by the small guanosine triphosphatase Ras homolog enriched in brain (Rheb), in a farnesylation-dependent manner. Therefore, to investigate the mechanism of mTOR activation, we used the farnesyl transferase inhibitor FTI-277, which partially blocked the growth of three of the six melanoma cell lines. Together, these data implicate activation of mTOR in the pathogenesis of melanoma, and suggest that Rheb and mTOR may be targets for melanoma therapy.

Oncogenic PIK3CA mutations occur in epidermal nevi and seborrheic keratoses with a characteristic mutation pattern

Activating mutations of the p110 alpha subunit of PI3K (PIK3CA) oncogene have been identified in a broad spectrum of malignant tumors. However, their role in benign or preneoplastic conditions is unknown. Activating FGF receptor 3 (FGFR3) mutations are common in benign skin lesions, either as embryonic mutations in epidermal nevi (EN) or as somatic mutations in seborrheic keratoses (SK). FGFR3 mutations are also common in low-grade malignant bladder tumors, where they often occur in association with PIK3CA mutations. Therefore, we examined exons 9 and 20 of PIK3CA and FGFR3 hotspot mutations in EN (n = 33) and SK (n = 62), two proliferative skin lesions lacking malignant potential. Nine of 33 (27%) EN harbored PIK3CA mutations; all cases showed the E545G substitution, which is uncommon in cancers. In EN, R248C was the only FGFR3 mutation identified. By contrast, 10 of 62 (16%) SK revealed the typical cancer-associated PIK3CA mutations E542K, E545K, and H1047R. The same lesions displayed a wide range of FGFR3 mutations. Corresponding unaffected tissue was available for four EN and two mutant SK: all control samples displayed a WT sequence, confirming the somatic nature of the mutations found in lesional tissue. Forty of 95 (42%) lesions showed at least one mutation in either gene. PIK3CA and FGFR3 mutations displayed an independent distribution; 5/95 lesions harbored mutations in both genes. Our findings suggest that, in addition to their role in cancer, oncogenic PIK3CA mutations contribute to the pathogenesis of skin tumors lacking malignant potential. The remarkable genotype-phenotype correlation as observed in this study points to a distinct etiopathogenesis of the mutations in keratinocytes occuring either during fetal development or in adult life.

Expression of dicarbonyl/L-xylulose reductase (DCXR) in human skin and melanocytic lesions: morphological studies supporting cell adhesion function of DCXR

BACKGROUND

It has been proposed that dicarbonyl/L-xylulose reductase (DCXR) is increased in prostate cancer. Also, when compared with normal skin, a virtual northern blot shows increased expression of DCXR in melanomas.

METHODS

We investigated DCXR expression in a tissue microarray, with 20 benign and 33 malignant melanocytic lesions and possible colocalization of DCXR with cell adhesion molecules using double immunofluorescence/confocal microscopy in normal human skin.

RESULTS

Most nevi expressed DCXR in the cytoplasmic membrane, but some melanomas (20-30%) showed loss of membranous expression with inappropriate cytoplasmic or nuclear expression. Perinuclear Golgi expression was found in primary (14%) and metastatic (32%) melanomas showing dishesive growth pattern. Overall, the intensity of expression was stronger in nevi compared with melanomas (p < 0.005). In normal skin, DCXR was colocalized with E-cadherin and beta-catenin at the intercellular membranes of keratinocytes and with CD31 at the intercellular junctions of endothelial cells. DCXR was localized in the cytoplasmic membrane of normal melanocytes.

CONCLUSIONS

These findings indicate that decreased membranous expression of DCXR with altered subcellular localization appears to be associated with malignant progression of melanocytic lesions. We show for the first time the expression of DCXR in normal keratinocytes, melanocytes and endothelial cells.

Expression of cyclo-oxygenase-2 in macrophages associated with cutaneous melanoma at different stages of progression

The biological significance of the almost constant presence of macrophages in the tumoral microenvironment is an issue debated by several authors. The major difficulty in understanding the role played by tumor-associated macrophages (TAMs) in tumor progression is due to the contrasting effects of TAMs found in different studies. In addition, there is a limited information on which of the many biological activities expressed by TAMs are critical in inducing stimulatory or inhibitory effect on tumor growth. The aim of our study was: (a) to explore to what extent cyclo-oxygenase-2 (COX-2) in TAMs associated with human melanoma is expressed at different stages of tumor progression; and (b) to explore whether COX-2 expression in TAMs is stimulated by melanoma cells. In order to answer this question, we determined COX-2 positive TAMs associated with cutaneous melanocytic nevi, in situ, invasive and metastatic melanoma. In addition, we investigated whether COX-2 is expressed in peritoneal thioglycollate-elicited macrophages after co-cultivation with murine B16 melanoma cells. We found that COX-2-positive TAMs, as revealed by immunohistochemical analysis, were rare in common nevi and "dysplastic nevi", but present in a high percentage in in situ and thin melanoma. COX-2-positive TAMs were also found in more advanced tumors and metastatic melanoma, although at a significantly lower percentage in these latter. The in vitro protocol revealed that COX-2 was expressed in peritoneal macrophages upon contact with B16 murine melanoma cells, but not with normal murine fibroblasts. On the whole, the results of in vivo and in vitro studies suggest that COX-2 expressed in TAMs appears to act as an effective biomarker of melanoma progression, and melanoma cells themselves might stimulate COX-2 in macrophages.

Fatty acid synthase expression in cutaneous melanocytic neoplasms

Mammalian fatty acid synthase is a multifunctional enzyme complex involved in de novo synthesis of saturated fatty acids, and inhibitors of fatty acid synthase are being evaluated as potential therapeutic agents. Increased fatty acid synthase expression has been demonstrated in subsets of malignancies, including colon, breast, endometrium, prostate and ovarian carcinomas, and recently malignant melanomas. We evaluated the immunohistochemical expression of fatty acid synthase in 155 cutaneous melanocytic lesions. They included 30 congenital nevi, 19 compound nevi, 40 Spitz nevi, 48 primary melanomas, and 18 metastatic melanomas. Fatty acid synthase expression was stronger in malignant melanomas in comparison to conventional nevi and Spitz nevi, and was the highest for metastatic melanoma. Of the primary malignant melanomas, mean fatty acid synthase scores were significantly greater for Clark levels IV and V compared to Clark levels I and II (P<0.001). In addition, melanomas with Breslow thickness 0.75-1.50 mm and >1.50 mm showed significantly higher mean fatty acid synthase scores compared with those with Breslow thickness <0.75 mm (P=0.013 and <0.001, respectively). Of interest, congenital melanocytic nevi also showed strong fatty acid synthase expression, similar to that seen in metastatic melanoma. This may represent persistence of or regression to a fetal phenotype since normal fetal tissues are known to express high levels of fatty acid synthase.

Expression of activated TrkA protein in melanocytic tumors: relationship to cell proliferation and clinical outcome

We evaluated expression of activated nerve growth factor receptor tyrosine kinase (p-TrkA) by immunohistochemical analysis in 152 primary and 64 metastatic human melanoma biopsy specimens and 8 nevi. Membranous, cytoplasmic, and/or nuclear expression of p-TrkA was seen in 54.6% of primary melanomas and 30% of metastases. Membranous p-TrkA was detected in 21.7% of primary and 14% of metastatic melanomas and cytoplasmic immunoreactivity in 28.9% of primary tumors and in 22% of metastases. Significantly fewer metastases than primary tumors expressed nuclear p-TrkA (16% vs 39.5%; P = .006). A significantly higher percentage of nodular than superficial spreading melanomas expressed membranous (40% vs 11%; P < .0001) p-TrkA. Nevi expressed no membranous or cytoplasmic p-TrkA; 63% showed nuclear reactivity. p-TrkA expression varied significantly with thickness of primary tumors (lower expression in thinner lesions: membranous, P = .004; cytoplasmic, P = .001; nuclear, P = .031). An association between ulceration and membranous (P = .054), cytoplasmic (P < .0001), and nuclear (P = .022) p-TrkA expression was found. Membranous p-TrkA significantly predicted decreased overall survival (P = .002). A significant association between membranous p-TrkA and cyclin A (P = .004) and Ki-67 (P < .0001) and between cytoplasmic p-TrkA and cyclin A (P < .0001), Ki-67 (P = .004), and cyclin D3 (P = .027) was found. p-TrkA had no effect on MAPK(ERK1/2) activation. A significant inverse association between cytoplasmic beta-catenin and cytoplasmic p-TrkA levels (P = .006) and between nuclear p-TrkA and cytoplasmic E-cadherin (P = .022) was seen. We present the first evidence of a role for TrkA activation in a subset of melanomas as a predictor of an aggressive phenotype and poor outcome.

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.

Expression of 12-lipoxygenase as a biomarker for melanoma carcinogenesis

12-Lipoxygenase (12-LOX), through its metabolite 12( )-hydroxyeicosatetraenoic acid [12( )-HETE], has been demonstrated to play a pivotal role in experimental melanoma invasion and metastasis, and 12-LOX expression may be important in early human melanoma carcinogenesis. We have studied the differences in 12-LOX protein expression during the progression of melanoma from human melanocytic cells to benign and dysplastic naevi to malignant metastatic disease. 12-LOX expression was determined in normal human skin melanocytes and in melanocytes found in compound naevi, dysplastic naevi and melanomas using a platelet-type 12-LOX antibody with a diaminobenzidine immunoperoxidase system detection system and was quantified using the analysis software NIH Image 1.62. Mean cellular pixel densities for 12-LOX staining ( = 50 cells/histological type) were unchanged in compound naevi ( = 0.14) and were increased in dysplastic naevi and melanomas compared with normal skin melanocytes ( = 0.03 and = 0.01, respectively). Similarly, melanomas had higher levels of expression compared with dysplastic naevi ( = 0.03). 12-LOX expression was significantly different between compound naevus and dysplastic naevus melanocytes ( = 0.01). These data suggest that 12-LOX may be an important novel marker for cancer progression within the melanoma system, and therefore could be a useful biomarker and therapeutic target for melanoma chemoprevention.

[Significance of human telomerase RNA expression in situ in malignant melanoma]

By using the method of hybridization in situ, human telomerase RNA(hTR) are detected in 36 cases of malignant melanoma tissue, 16 cases of nevocellular nevus and 12 cases of normal skin. Results showed that the positive expression percentage of hTR in malignant melanoma, nevocellular nevus and normal skin was 86.3%, 6.26% and 12.7%, respectively. The positive expression percentage of hTR in malignant melanoma was significantly higher than that of nevocellular nevus and normal skin(P < 0.01). Meanwhile, the positive expression intensity of hTR in metastatic malignant melanoma is frequently stronger than that of original malignant melanoma(P < 0.05). The results suggest that hTR might indirectly reflect the telomerase activity, and be used as a new marker for diagnosis of malignant melanoma and metastasis prediction.

Quantitative in situ evaluation of telomeres in fluorescence in situ hybridization-processed sections of cutaneous melanocytic lesions and correlation with telomerase activity

BACKGROUND

Telomere length is correlated with cellular ageing and immortalization processes. In some human cancers telomere length measurement has proved to be of diagnostic and prognostic value. Results comparable with the traditional terminal restriction fragment length determination by Southern blotting have been obtained in metaphase and interphase cells in some studies by fluorescence in situ hybridization (FISH) analysis; FISH additionally allows for the quantification of telomeres at the cellular level.

OBJECTIVES

In this study, 32 melanocytic lesions were analysed by FISH, aiming at investigating possible telomere differences among various benign and malignant lesions and correlation with telomerase activity (TA) level.

METHODS

FISH was performed on paraffin sections from six common naevi, eight Spitz naevi, 12 melanomas, six melanoma metastases and nine control samples of normal skin. Telomere mean maximum diameter (Feret max), area and number per nuclear area were calculated by image analysis on fluorescent images elaborated through KS400 and in situ imaging system (ISIS) for FISH analysis programs. Mean TA level was also calculated in all lesions and correlated with telomere parameters.

RESULTS

Telomere number per nuclear area was significantly lower in melanomas and metastases than in benign common and Spitz naevi and in control skin (7 small middle dot24 +/- 3.3; 6.11 +/- 3 vs. 14.46 +/- 5.6; 16.92 +/- 7.8; and 12.59 +/- 3.4, respectively; P < 0 .001). No significant differences were found for the other telomere parameters. In common and Spitz naevi, telomere number was positively correlated with Feret max (P = 0.046 and P < 0.0001, respectively). TA was significantly higher in melanomas and metastases than in the other groups (70.18 +/- 25.2; 105.07 +/- 30 vs. 2.16 +/- 2.4; 2 .99 +/- 2.1; 2 +/- 1.2, respectively; P< or = 0. 001) and it was inversely correlated with telomere number per nuclear area in melanomas (P = 0.0041). No other significant correlations were found.

CONCLUSIONS

Encouraging results have been obtained from quantitative telomere evaluation in the diagnosis of melanocytic lesions, although an analysis of a larger number of cases would be necessary to provide more reliable data. An extreme shortening of some telomeres probably results in the decrease of telomeric signals and the lower mean number of detectable telomeres in melanomas and metastases. In melanomas, telomere number per nuclear area is also inversely correlated with TA levels. Quantitative FISH of melanocytic lesions could give more specific information at the cellular level in telomere and telomerase fields of investigation.

Nevus cells in lymph nodes: an association with congenital cutaneous nevi

It is known that collections of nevus cells can occur in the collagenous framework of lymph nodes excised for a variety of reasons. These can be difficult to distinguish from nodal deposits of metastatic cancer but attention to cytologic detail, the distribution of the cells, and their immunohistochemical profile usually lead to a satisfactory conclusion. From another perspective, the mechanism by which nevus cells are deposited in lymph nodes has been a source of interest and controversy. Theories in this regard include embolic transfer of cells from cutaneous nevi to corresponding regional nodes and an aberration in the embryologic migration of melanocytes in utero. There have been tentative indications in the literature of a potential link between the presence of nevus cells in lymph nodes and cutaneous nevi in corresponding catchment areas of skin. In the course of evaluating sentinel lymph nodes from patients with melanoma, we noted a significant association between the presence of nodal nevi and cutaneous nevi in corresponding regional zones of skin (Fischer's exact test, p = 0.021). The link with cutaneous nevi of congenital type was even stronger (Fischer's exact test, p = 0.008). This consolidates previous sporadic reports of such an association and through further scrutiny may help shed light on the mechanism by which nodal and congenital cutaneous nevi are linked.

Telomerase activity and expression of apoptosis and anti-apoptosis regulators in the progression pathway of human melanoma

The stages defining the progression pathway of human melanoma are atypical nevi, the precursor lesions and risk markers of melanoma, melanoma in situ and melanoma in the radical growth phase (RGP), which represent the early stages of melanoma development, and primary melanoma in the vertical growth phase (VGP) and melanoma in the metastatic growth phase (MGP), which are the advanced stages of the disease. Unlike cells obtained from VGP and MGP melanomas, which can be established as cell lines, cells derived from atypical nevi, melanoma in situ, and RGP melanoma cannot be propagated in vitro. Thus, information regarding molecular markers that may be differentially expressed in the early versus the advanced stages of this disease can only be obtained from the analysis of specimens. Since activation of telomerase and deregulation of apoptosis contribute to the pathogenesis of a significant number of human malignancies, we conducted a study, using nevus and melanoma specimens, to determine at what stage in the progression pathway of melanoma, telomerase activity can first be detected, and whether concordant with telomerase activation, one might observe a stage-specific switch from expression of promoters to inhibitors of apoptosis. The findings described here, demonstrate telomerase activity in some but not all MGP melanomas and not in any of the preceding pathological stages, and no apparent imbalance between pro- and anti-apoptotic markers in telomerase-positive MGP melanomas compared to telomerase-negative nevi and telomerase-negative VGP and MGP melanomas.

Expression of the inducible isoform of nitric oxide synthase in pigment cell lesions of the skin

Nitric oxide (NO) is a small molecule produced during the conversion of L-arginine to L-citrulline by NO synthase (NOS). Several isoforms of NOS exist, of which the Ca2+-independent, inducible NOS (iNOS or NOS2) is most prominently expressed by macrophages. iNOS activity and increased levels of iNOS have been found in various tumours and tumour cell lines but not in normal tissues; however, the precise role of NO in tumour progression has yet to be elucidated. We studied the expression of iNOS in paraffin sections of 41 benign naevi and 52 primary malignant melanomas (MM) of the skin, as well as in 13 metastatic MM. In addition, nitrotyrosine, indicative of NO production and formation of peroxynitrite, was studied in frozen sections of 13 naevi and 30 MM. Virtually all naevi expressed iNOS, but very few expressed nitrotyrosine, indicating either that iNOS in naevi is functionally inactive, or that naevus cells lack reactive oxygen radicals and thus do not form peroxynitrite. Normal melanocytes in adjacent uninvolved skin were unreactive for both markers. In MM, iNOS was most frequently expressed in the 'pure' and 'invasive' radial growth phase (RGP), whereas expression in the vertical growth phase (VGP) and metastatic phase occurred only in 76% of cases; moreover, in these latest phases of tumour progression, iNOS staining was weak and focal. We conclude that iNOS is expressed de novo in most benign pigment cell lesions. In MM (iNOS-generated) NO appears to play an important part in the early steps of invasion (i.e. the 'invasive' RGP), where it may stimulate neo-angiogenesis and may be a prerequisite for further tumour progression; this view is also supported by the finding of iNOS in the associated blood vessels in the papillary dermis. Finally, our data suggest that (iNOS-generated) NO plays a less significant part in the VGP and in metastatic melanoma.

Increase in telomerase activity during progression of melanocytic cells from melanocytic naevi to malignant melanomas

During successive cell divisions of mortal cells the length of the telomeres (TTAGGG repeats in vertebrates) at the end of chromosomes decreases. It has been suggested that this process is responsible for cellular senescence. Expression of the ribonucleoprotein telomerase appears to prevent shortening of telomeres in germ-line cells and cancer cells. The purpose of this study was to investigate telomerase activity in melanocytic lesions and its possible role in the multi-step tumor progression model of malignant melanoma. To quantify the level of telomerase activity both in cultured cells and in fresh tissue samples the TRAP (telomeric repeat amplification protocol) ELISA was used. Eight cell lines of malignant melanoma, 3 primary cultures of fibroblasts, 36 melanocytic naevi, 5 atypical melanocytic naevi, 3 Spitz's naevi, 31 primary malignant melanomas and 13 metastases of malignant melanomas were investigated. Also 34 samples of skin (22 samples of perilesional skin and 12 samples of normal skin) were analysed. In our experiments all melanoma cell lines were strongly positive, whereas in fibroblasts telomerase activity could not be detected. Of the primary melanomas and metastatic melanomas, 90.3% and 92.3%, respectively, were strongly positive, and of the atypical melanocytic naevi, 80% were positive. Of the 36 common melanocytic naevi only 10 (27.7%) expressed weak telomerase activity and of the 34 samples of human skin, 4 (11.7%) expressed very weak telomerase activity. Our results indicate that telomerase activity increases from benign melanocytic naevi to atypical naevi and further to malignant melanoma and metastatic melanoma cells, and therefore may play a role in tumour initiation and progression.

Tyrosinase immunoreactivity in formalin-fixed, paraffin-embedded primary and metastatic melanoma: frequency and distribution

Monoclonal antibody T311 specifically detects tyrosinase protein expression. Tyrosinase-derived peptides are recognized by CD8+ T-cells and applied in immunotherapy. We examined formalin-fixed paraffin-embedded tissue of 50 melanoma (primary n=31, metastatic n=19) and 41 control cases (junctional, dermal, compound, Spitz, Reed, balloon-cell nevi) by immunochemistry using the alkaline phosphatase-anti-alkaline phosphatase method after antigen retrieval. Staining with mAb T311 showed a sensitivity of 94% for melanoma with a very high specificity for melanocytic cells. Immunopositivity (94% of melanomas overall) correlated inversely with clinical stage: clinical stage I and stage II showed 100%, stage III and stage IV 86% immunoreactivity each. Staining changed from an exclusively homogeneous pattern in early stages to a more heterogeneous pattern in later stages. Melanocytic control tissue like nevi of different subtypes all showed weak to moderate, homogeneous immunoreactivity with polarity towards the epidermis. RT-PCR ELISA analysis of short-term melanoma cell cultures displayed mRNA expression in only half of the originally immunopositive tumors only, suggesting rapid mRNA expression loss in culture. mAb T311 allows detection of melanoma-associated tyrosinase protein expression and thus profiling of melanomas using routine archival tissue suited for immunotherapy approaches involving tyrosinase derived epitopes.

Immunohistochemical studies of beta-hexosaminidase in neoplastic and normal tissues with monoclonal antibodies

A total of 87 human specimens with 10 histological types of primary neoplasm were studied immunohistochemically with monoclonal antibodies specific for beta-hexosaminidase (Hex). High levels of Hex were found in malignant neoplasms of the skin, cervix, colorectum and in benign as well as neoplastic plasma cells, while no activity was detected in normal epidermis, normal colorectal epithelium or benign naevi. The strongest immunohistochemical reaction was revealed in tumor cells of malignant melanoma. Adenomas and adenocarcinomas of the colorectum showed high levels of Hex with a basal pattern of immunoreactivity more frequent in the tumor cells of adenocarcinomas than adenomas. Fibroblasts and macrophages in the tumors often disclosed immunoreactivity. In most of the sections (including those from plasma cell neoplasms), 7E4 antibody showed low immunoreactivity compared to 2E3, except for non-neoplastic plasma cells, which were as a rule positive with 7E4 and largely negative with 2E3 antibody. This result probably indicated different isoenzymes in benign and neoplastic plasma cells.

Biochemical analysis of metastasis-related Ax actin in B16 mouse melanoma cells after chemical reversional modulation and of tumor progression-related A' actin in the ontogeny of human malignant melanoma

To examine the correlation between tumor metastasis and Ax actin in mouse melanoma and between tumor progression and A'.actin in human melanoma and further to investigate whether or not it is a generally existing principle, we studied the effects of reversion agents, which distinctly decrease metastatic ability of melanoma cells, on the appearance of Ax actin. Will an induced decrease in metastasis of established highly metastatic B16-F10 mouse melanoma cells cause the appearance of Ax actin? We also examined the appearance of A' actin in eight human benign pigment cell tumors and nine human malignant melanoma tissues or cells in relation to tumor progression. In vitro treatment of B16-F10 cells with each of these agents suppressed metastatic ability of the cells injected intravenously into syngenic mice; however, none of the treated cells represented Ax actin in vitro. These results suggest that the appearance of Ax actin may be a result of long-term tumor cell progression leading to changes in gene level, but because the treatments with these agents were only carried out over a short period, they could not effect changes in gene level; thus, Ax actin appearance remained unchanged. Appearance of A' actin was detected only in human benign pigment cell tumors such as nevus cell nevi, but not in malignant melanomas, which were also formed in a long period of tumor progression in vivo. These results suggest that A' actin is a clinically useful marker to determine the prognosis and level of tumor progression of human pigment cell tumors.

Patterns of staining for neurone specific enolase in benign and malignant melanocytic lesions of the skin

Neurone specific enolase (NSE) is a useful marker for melanoma independent of the criterion of melanogenesis. A range of benign and malignant melanocytic skin lesions has been studied to assess the diagnostic potential of staining for NSE. The detailed features of the presence and distribution of NSE in 47 skin lesions are presented. These include 3 junctional, 7 compound, 15 intradermal and 8 SPitz naevi; 6 superficial type, 2 lentigo maligna and 6 nodular melanomata. A progressive increase of staining for NSE from benign to malignant is seen. Spitz naevi could easily be differentiated from melanoma. An advantage of this stain is the simultaneous demonstration of the innervation of these lesions. We conclude that NSE is a useful aid to the diagnosis and assessment of melanocytic skin tumours and may prove of value in clarifying the nature of these enigmatic lesions.

Enolase isoenzymes in benign and malignant melanocytic lesions

The distributions of the alpha, beta and gamma subunits of enolase were studied in 34 melanocytic lesions using the peroxidase-antiperoxidase (PAP) technique. Melanocytes in benign neoplasms stained moderately strongly for both alpha enolase and gamma enolase but staining for beta enolase was consistently negative. Staining for alpha enolase was always stronger than that for gamma enolase. There are some indications that with increasing degrees of dedifferentiation there was a reduction of gamma enolase activity, least differentiated cells being completely negative. Ocular melanomata showed similar changes to those seen in the skin. The enolase isoenzyme composition of tumour extracts was assessed biochemically on a limited number of cases and these results are discussed in relationship to the immunohistochemical studies.

Decreased collagenase production by regional fibroblasts cultured from skin of a patient with connective tissue nevi of the collagen type

A 10-yr-old female presented with cerebriform tumors covering the plantar surfaces of both feet. Histologically, the lesions consisted of thick collagen fibers and the content of collagen per surface area of skin was increased about 8-fold. Examination of the collagen by SDS-polyacrylamide gel electrophoresis, after limited pepsin proteolysis, showed that the lesions consisted almost exclusively of type I collagen, the predominant collagen type in human skin. Thus, a diagnosis of connective tissue nevi of the collagen type was made. Fibroblast cultures were established from the affected and normal-appearing areas of the skin, and examined for the rate of collagen synthesis, production of collagenase and growth kinetics of the cells. Cell cultures derived from the lesion and from control skin synthesized procollagen at the same rate and in a normal type I/type III procollagen ratio. However, the production of enzymatically active and immunologically detectable collagenase was reduced by 70-82% in the cultures derived from the lesion as compared to controls (p less than 0.005). Fibroblasts derived from the lesions also displayed a mean population doubling time of 1.17 +/- 0.08 days compared to 1.83 +/- 0.24 and 1.92 +/- 0.09 days for control cell strains and cells derived from normal skin of the patient, respectively (p less than 0.025). These results suggest that the excessive deposition of collagen in this case may have resulted from decreased local degradation of collagen. Enhanced proliferative capacity of the regional fibroblasts may have contributed to the accumulation of collagen in these lesions.

Proteolytic enzymes and plasminogen activator in melanoma

Proteolytic activities were measured in extracts of human skin melanoma, lymphatic metastasis and in nonmalignant naevi by using various proteinase substrates as well as plasminogen activator assay. pH-optima for hydrolysis of various proteinase substrates by these tumors were found to be essentially the same as in healthy human skin. Melanoma extracts were found to especially readily hydrolyze N-alpha-benzoyl-DL-arginine beta-naphthylamine (BANA) at pH 5.8 in the presence of 1 mmol/l dithiothreitol and EDTA (cathepsin B1-like enzyme) as well as histones and p-tosyl-L-arginine methyl ester (TAME) at pH 7.5, and showed increased capacity to activate plasminogen when compared to nonmalignant naevus. The possible role of proteinases in malignant melanoma is discussed.

Eruptive naevi: report of two cases, with enzyme histochemical, light and electron microscopical findings

The cases of two young adults with widespread multiple eruptive naevi are described. In the first patient, more than 100 lesions appeared during a period of 6 months. Young lesions were small flesh-coloured telangiectatic papules; older lesions were larger and verrucose with histological features of cellular naevi. In the second patient, a great number of lentigines developed in the course of 2 years. Light and electron microscopy showed that giant melanosomes were present within the lesions. The plasma level of beta-MSH-like immuno-reactivity was normal.

Enzymes of carbohydrate metabolism in naevoid basal-cell epithelioma

The activities of 27 enzymes of carbohydrate metabolism and the proportions of lactate dehydrogenase isoenzymes were determined in epidermis, in superficial epitheliomas and in several solid tumours biopsied from a patient with basal-cell naevus syndrome. The activity patterns varied from that of normal epidermis to that found in basal-cell epitheliomas. Thickened epidermis, superficial epitheliomas and some of the solid tumours presented an intermediate pattern. Histologically similar lesions sometimes differed markedly in their enzyme activities.

The tyrosinases of normal and diseased human skin (naevi, malignant melanoma, vitiligo)

Extracts of healthy and diseased skin in vitiligo, naevi and malignant melanoma were electrophoresed on polyacrylamide gel. Melanin bands were visualized on the gel by Dopa reaction. The tyrosinases found in malignant melanoma were also present in naevocellular naevi. Additional dopa melanin bands were observed. Some bands which were not related to the presence of melanocytes varied with the level of the melanogenetic activity in the individual patients.

Tyrosinase activity in three types of the malignant melanoma: superficial spreading melanoma, lentigo maligna melanoma and nodular melanoma

Quantitative differences in the tyrosinase activity are found at the three types of malignant melanoma of Clark and Mihm by the combined 3,4-dihydroxyphenylalanine-premelanin-reaction. Only a very small activity is present in the junction nevus. In the superficial spreading melanoma the tyrosinase activity is clear, but limited. The lentigo maligna melanoma shows an increased pigmentation. The topmost activity after incubation however is present in the nodular melanoma.