Immunohistochemical detection of antigen in human primary and metastatic melanomas by the monoclonal antibody 140.240 and its possible prognostic significance

Molecular Profile, Tissue Distribution and Prognostic Evaluation of a Human Melanoma-Carcinoma Antigen Recognized by the Murine Monoclonal Antibody B1.1

Using the murine monoclonal antibody (MoAb) B1.1 we have analyzed the immunochemical profile and the tissue distribution of a human melanoma associated antigen (MAA) carrying an epitope shared by the 180 kd CEA. Results of this study have demonstrated that the epitope expressed by the MAA is carried by a distinct set of molecules of 110-140 kd. Similarly to the 180 kd CEA molecules synthesized by carcinomas, the expression of the melanoma associated CEA like components (MA-CEA) is upregulated by IFN-α. The tissue distribution of MA-CEA is not restricted to malignant primary and metastatic melanocytic lesions but is found also at low levels in 64% of benign nevi. No circulating CEA was found in patients bearing widespread metastatic disease of MA-CEA positive lesions.

Preliminary clinical evaluation of stage I melanoma patients bearing MoAb Bl. l positive lesions has not shown a significative prognostic association of this phenotypic marker with clinical course of the disease.

Biomarkers: the useful and the not so useful--an assessment of molecular prognostic markers for cutaneous melanoma

Among individuals with localized (Stage I-II) melanoma, stratifying patients by a number of phenotypic variables (e.g., depth of invasion, ulceration) yields a wide range of 10-year melanoma-specific survival rates. With the possible exception of Ki-67, no molecular assessment is routinely used. However, there have been a tremendous number of studies assessing protein expression by immunohistochemistry toward the goal of better prediction of recurrence. In a previous systematic review, which required publication of multivariable prognostic models as a strict inclusion criterion, we identified 37 manuscripts that collectively reported on 62 proteins. Data for 324 proteins extracted from 418 manuscripts did not meet our inclusion criteria for that study, but are revisited here, emphasizing trends of protein expression across either melanocytic lesion progression or gradations of tumor thickness. These identified 101 additional proteins that stratify melanoma, organized according to the Hanahan and Weinberg functional capabilities of cancer.

The melanoma tumor antigen, melanotransferrin (p97): a 25-year hallmark – from iron metabolism to tumorigenesis

Melanotransferrin (MTf) or melanoma tumor antigen p97 is a transferrin (Tf) homolog that is found predominantly bound to the cell membrane via a glycosyl phosphatidylinositol anchor. The molecule is a member of the Tf superfamily and binds iron through a single high-affinity iron(III)-binding site. Since its discovery on the plasma membrane of melanoma cells, the function of MTf has remained intriguing, particularly in relation to its role in cancer cell iron transport. In fact, considering the crucial role of iron in many metabolic pathways, e.g., DNA synthesis, it was important to understand the function of MTf in the transport of this vital nutrient. MTf has also been implicated in diverse physiological processes, such as plasminogen activation, angiogenesis and cell migration. However, recent studies using a knockout mouse and post-transcriptional gene silencing have demonstrated that MTf is not involved in iron metabolism, but plays a vital role in melanoma cell proliferation and tumorigenesis. In this review, we discuss the possible biological functions of MTf, particularly in relation to cancer.

The soluble form of the membrane-bound transferrin homologue, melanotransferrin, inefficiently donates iron to cells via nonspecific internalization and degradation of the protein

Melanotransferrin (MTf) is a membrane-bound transferrin (Tf) homologue found particularly in melanoma cells. Apart from membrane-bound MTf, a soluble form of the molecule (sMTf) has been identified in vitro[Food, M.R., Rothenberger, S., Gabathuler, R., Haidl, I.D., Reid, G. & Jefferies, W.A. (1994) J. Biol. Chem.269, 3034-3040] and in vivo in Alzheimer's disease. However, nothing is known about the function of sMTf or its role in Fe uptake. In this study, sMTf labelled with 59Fe and 125I was used to examine its ability to donate 59Fe to SK-Mel-28 melanoma cells and other cell types. sMTf donated 59Fe to cells at 14% of the rate of Tf. Analysis of sMTf binding showed that unlike Tf, sMTf did not bind to a saturable Tf-binding site. Studies with Chinese hamster ovary cells with and without specific Tf receptors showed that unlike Tf, sMTf did not donate its 59Fe via these pathways. This was confirmed by experiments using lysosomotropic agents that markedly reduced 59Fe uptake from Tf, but had far less effect on 59Fe uptake from sMTf. In addition, an excess of 56Fe-labelled Tf or sMTf had no effect on 125I-labelled sMTf uptake, suggesting a nonspecific interaction of sMTf with cells. Protein-free 125I determinations demonstrated that in contrast with Tf, sMTf was markedly degraded. We suggest that unlike the binding of Tf to specific receptors, sMTf was donating Fe to cells via an inefficient mechanism involving nonspecific internalization and subsequent degradation.

The iron metabolism of neoplastic cells: alterations that facilitate proliferation?

For many years it has been known that neoplastic cells express high levels of the transferrin receptor 1 (TfR1) and internalize iron (Fe) from transferrin (Tf) at a tremendous rate. Considering the high requirement of neoplastic cells for Fe, understanding its metabolism is vital in terms of devising potential new therapies. Apart from TfR1, a number of molecules have been identified that may have roles in Fe metabolism and cellular proliferation. These molecules include transferrin (Tf), the oestrogen-inducible transferrin receptor-like protein, transferrin receptor 2 (TfR2), melanotransferrin (MTf), ceruloplasmin, and ferritin. In the present review these latter molecules are discussed in terms of their potential functions in tumour cell Fe metabolism and proliferation. Further studies are essential to determine the specific roles of these proteins in the pathogenesis of cancer.

The membrane-bound transferrin homologue melanotransferrin: roles other than iron transport?

Melanotransferrin (MTf) is a membrane-bound transferrin (Tf) homologue that is found at high levels in melanoma cells. MTf has many characteristics in common with serum Tf and previous studies have shown that it can bind Fe. This has led to speculation that MTf may be involved in Fe transport. Because Fe is required for a variety of metabolic reactions including ATP and DNA synthesis, MTf could play a role in proliferation. However, recently it has been shown that MTf plays very little role in Fe uptake by melanoma cells, and unlike other Fe transport molecules (e.g. the transferrin receptor), its expression is not controlled by Fe. In the present review the function of MTf is discussed in relation to data suggesting other roles apart from Fe uptake.

The role of the membrane-bound tumour antigen, melanotransferrin (p97), in iron uptake by the human malignant melanoma cell

Melanotransferrin (MTf) is a membrane-bound transferrin (Tf) homologue with several characteristics in common with serum Tf. MTf is found at high levels in melanoma cells and previous studies have shown that MTf can bind Fe. In addition, Chinese hamster ovary cells transfected with MTf transport Fe from 59Fe-citrate at greater rates than control cells. However, the role of MTf in the Fe uptake process of human melanoma cells remains unknown. In the present study we have characterized the role of MTf in Fe uptake by SK-Mel-28 melanoma cells in order to understand its function. Initial studies examined whether modulation of intracellular Fe levels using the Fe chelator desferrioxamine (DFO) or the Fe donor ferric ammonium citrate (FAC) could change MTf mRNA levels. In contrast to transferrin receptor (TfR) mRNA that increased after exposure to DFO and decreased after incubation with FAC, there was no change in MTf mRNA levels. In addition, compared to control cells, there was no alteration of 125I-labelled anti-MTf mAb-binding in cells exposed to DFO or FAC, suggesting no change in the number of MTf sites. Further studies examined the ability of DFO and FAC to modulate Fe uptake from 59Fe-citrate which is bound by MTf. In contrast to the effect of DFO or FAC at increasing and decreasing Fe uptake from 59Fe-Tf, respectively, DFO had no influence on 59Fe-citrate uptake, whereas FAC markedly increased it. Collectively, these studies suggest that MTf is not regulated in a manner similar to the TfR in response to cellular Fe levels. MTf can be removed from the membrane by phosphatidylinositol-specific phospholipase C (PtdIns-PLC). Preincubation of melanoma cells with PtdIns-PLC reduced anti-MTf mAb binding to 3% of the control, while PtdIns-PLC only slightly reduced 59Fe uptake from 59Fe-citrate. These results suggest that MTf played only a minor role in Fe uptake from 59Fe-citrate by these cells. The expression of MTf mRNA (poly A+) was also examined in 50 human tissues and found to be markedly different to Tf mRNA or TfR mRNA. Surprisingly, MTf mRNA expression was widespread in normal tissues, and was observed at its highest levels in the salivary gland. In contrast to expectations, MTf mRNA expression was generally greater in adult than fetal tissues.

Phenotypic cytoskeletal heterogeneity in melanoma, a challenge to the surgical pathologist evaluating a poorly differentiated neoplasm: an illustrative case

Characterization of poorly differentiated neoplasms can be a challenging task for the surgical pathologist. It is essential that the entire spectrum of immunomorphologic findings of various tumors be recognized to avoid improper characterization of a given neoplasm, which may in turn adversely affect patient management. Tumor characterization is complicated by the immunomorphologic transformations that malignant cells may undergo by virtue of which they may depart from expression of expected features and acquire new, unexpected characteristics. Traditionally, amelanotic melanomas have been difficult to characterize because of the diversity of their light microscopic morphology (epithelioid, spindle, and combined varieties). As a result, several other neoplasms are usually considered in the differential diagnosis. This report describes a primarily spindle-cell amelanotic melanoma that created a diagnostic dilemma, which could only be resolved by combining the information obtained from extensive evaluation by means of several diagnostic techniques. This case also stresses the phenotypic heterogeneity of the cytoskeleton of malignant melanomas and therefore their varied immunomorphologic characteristics.

Antigen dynamics in melanocytic and nevocytic melanoma oncogenesis: anti-ganglioside and anti-ras p21 antibodies as markers of tumor progression

Based on melanoma pathogenesis, phenotypic dynamics in pigment cell tumor progression detected with 11 MoAb have been defined. Anti-melanosomal A4F11 antibody reacts with every type of pigment cell tumor tested except for a few specimens. TNKH1 and anti-K.1.2 antibodies recognize nevocytic benign to premalignant tumors. HLA-DR, A.1.43, and A.10.33 antigens are expressed in advanced melanomas. Staining with anti-ganglioside GM3 and GD3 antibodies, M2590 and 4.2, respectively, reveals that most pigment cell tumors express gangliosides GM3 and GD3. But A2B5 antibody, which detects some polysialogangliosides such as GQ1C, reacts with highly progressed melanoma cells. Anti-ras p21 antibodies, RASK-3 and RASK-4, react with malignant melanomas and their premalignant lesions. These findings suggest the following: A4F11 is a universal marker of pigment cell tumors. TNKH1 and anti-K.1.2 antibodies might not be markers of melanocytic tumors but of nevocytic benign to premalignant tumors. Melanoma cells express gangliosides GM3 and GD3 as common pigment cell antigens and synthesize aberrant polysialogangliosides. Anti-ganglioside MoAb, including A2B5, are possible markers of the level of malignancy in melanoma cells like anti-A.1.43 and anti-A.10.33 antibodies. Enhanced ras p21 expression already appears on premalignant pigment cells.

Oncofetal antigen in Xiphophorus detected by monoclonal antibodies directed against melanoma-associated antigens

Monoclonal antibodies (MAbs) directed against Xiphophorus melanoma cells were developed and tested by indirect immunofluorescence and immunoperoxidase staining for reactivity with a panel of 15 allogeneic tissues and 12 allogeneic cell lines. The reactivity of such MAbs was restricted to melanoma cells from tumor biopsies and melanoma-derived cell lines. In addition, all embryonic cells of all histiotypes from developmental stages later than mid-organogenesis and from corresponding short term in vitro cultures reacted with these MAbs. In contrast, normal tissues and organs from adult fish displayed no reactivity, thus implying that the melanoma-associated antigens detected by the MAbs described are oncofetal antigens.

Immunohistochemical phenotyping of human solid tumors with monoclonal antibodies in devising biotherapeutic strategies

A panel of 14 monoclonal antibodies (MoAbs) (4 raised against breast cancer, 6 against colon cancer and 4 against melanoma) were used to phenotype frozen sections of tumor biopsies obtained from 110 patients, by avidin-biotin-peroxidase complex techniques. We observed heterogeneity of antigen expression among the multiple metastatic lesions of single patients, as well as among tumor lesions from different patients with similar tumor histotypes. A wide range of cross-reactivity of anti-(breast-carcinoma) and anti-(colon-carcinoma) MoAbs with other carcinoma histotypes and limited reactivity with melanoma and sarcoma was detected. Some of our anti-melanoma MoAbs were also found to cross-react with selected carcinomas. Nine of the 14 MoAbs most reactive with carcinomas of diverse histotypes have been identified. A mixture or 'cocktail' of different MoAbs could be selected for each individual patient in order to achieve binding of MoAbs with most, if not 100% of tumor cells. This study illustrates the approach that we have taken to individualize the cocktail of MoAbs for the development of patient-specific therapeutic immunoconjugates.

Recognition of malignant melanoma by monoclonal antibody HMB-45. An immunohistochemical study of 200 paraffin-embedded cutaneous tumors

Antibodies to S-100 protein have been used widely as markers of malignant melanoma, despite abundant evidence that they are non-specific for this neoplasm. Hence, alternatives to these reagents are desirable in diagnostic dermatopathology. We evaluated the characteristics of a new monoclonal antibody (HMB-45) which does have putative specificity for melanoma, and compared it with a polyclonal anti-S-100 reagent in immunohistochemical staining of 67 melanomas of the skin and 133 non-melanomatous cutaneous neoplasms. All specimens were formalin-fixed and paraffin-embedded, and were studied with the avidin-biotin-peroxidase complex technique. HMB-45 labelled 62 of 67 melanomas, while anti-S-100 recognized all tumors of this type. On the other hand, S-100 also was expressed by 15 of the non-melanocytic neoplasms, all 133 of which were HMB-45-negative. The only cases of melanoma that were missed by the latter reagent were of the spindle-cell type. Hence, HMB-45 was 100% specific and 93% sensitive, relative to a diagnosis of malignant melanoma in paraffin sections. Epithelioid and small-cell neoplasms are reliably recognized by this antibody, but it would appear that spindle-cell melanomas must be detected by other immunohistochemical means.