Cell surface antigens of human melanocytes and melanoma. Expression of adenosine deaminase binding protein is extinguished with melanocyte transformation

Effect of transplanted cells with CD184 and CD26 expressions and reconstitution of CD3+ lymphocyte population on long-term survival after autologous hematopoietic stem cell transplantation for multiple myeloma

Autologous hematopoietic stem cell transplantation (auto-SCT) is the recommended treatment for responding patients with multiple myeloma (MM). However, we do not know the risk factors influencing long-term survival without progression after auto-SCT. Therefore, this prospective study aimed to investigate the influence of transplanted cells with cluster of differentiation (CD)184+ expression, CD26+ lymphocytes and monocytes, and reconstitution of CD3+ lymphocytes on overall survival (OS) and progression-free survival (PFS) after auto-SCT in MM. Forty-eight patients with MM underwent auto-SCT at our center from 2011 to 2013. The numbers of CD184+ cells, CD26+ lymphocytes, and CD26+ monocytes were measured in the harvested material. In addition, the number of lymphocyte subpopulations (CD3+ lymphocytes, helpers, suppressors, natural killer (NK), cytotoxic NK, and B lymphocytes) was measured in peripheral blood during regeneration after auto-SCT. Flow cytometry was performed in both cases. The median OS was 92 months. Our analysis revealed a statistically significant effect of the number of transplanted CD184+ cells on OS and a statistically significant correlation between PFS and the number of transplanted CD184+ cells and reconstitution of CD3+ lymphocytes. In conclusion, our study showed that the increasing numbers of transplanted CD184+ cells, CD26+ lymphocytes, and CD26+ monocytes augmented the risk of death.

The role of Dipeptidyl Peptidase-4 in cutaneous disease

Dipeptidyl peptidase-4 (DPP4) is a multifunctional, transmembrane glycoprotein present on the cell surface of various tissues. It is present in multiple molecular forms including cell surface and soluble. The role of DPP4 and its inhibition in cutaneous dermatoses have been a recent point of investigation. DPP4 exerts a notable influence on T-cell biology, the induction of skin-specific lymphocytes, and the homeostasis between regulatory and effector T cells. Moreover, DPP4 interacts with a broad range of molecules, including adenosine deaminase, caveolin-1, CXCR4 receptor, M6P/insulin-like growth factor II-receptor and fibroblast activation protein-α, triggering downstream effects that modulate the immune response, cell adhesion and chemokine activity. DPP4 expression on melanocytes, keratinocytes and fibroblasts further alters cell function and, thus, has crucial implications in cutaneous pathology. As a result, DPP4 plays a significant role in bullous pemphigoid, T helper type 1-like reactions, cutaneous lymphoma, melanoma, wound healing and fibrotic disorders. This review illustrates the multifactorial role of DPP4 expression, regulation, and inhibition in cutaneous diseases.

The potential role of adenosine signaling in the pathogenesis of melanoma

Melanoma cancer cell proliferation, motility, invasion, and tumor growth is affected by the adenosine pathway that consists of adenosine-synthesizing enzymes, receptors, and their respective agonists/antagonists. Accumulating evidence suggests that ischemia and inflammation, two conditions associated with melanoma, display dysregulated adenosine metabolism, which implicates it as the mechanism responsible for the pathogenesis of melanoma, thereby resulting in advanced diagnosis and therapy. Suppression of adenosine signaling by inhibiting adenosine receptors or adenosine-generating enzymes (CD39 and CD73) on melanoma cells presents a novel therapeutic target for patients with melanoma. This review summarizes the role of adenosine signaling in the pathogenesis of melanoma to advance its understanding and hence improve therapeutics and management.

Inosine strongly enhances proliferation of human C32 melanoma cells through PLC-PKC-MEK1/2-ERK1/2 and PI3K pathways

Malignant melanoma is the most deadly type of skin cancer. The lack of effective pharmacological approaches for this tumour can be related to the incomplete understanding of the pathophysiological mechanisms involved in melanoma cell proliferation. Adenosine has growth-promoting and growth inhibitory effects on tumour cells. We aimed to investigate effects of adenosine and its metabolic product, inosine, on human C32 melanoma cells and the signalling pathways involved. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and bromodeoxyuridine (BrdU) proliferation assays were used to evaluate adenosine, adenosine deaminase and inosine effects, in the absence or presence of adenosine receptor (AR), A3 AR and P2Y1 R antagonists and PLC, PKC, MEK1/2 and PI3K inhibitors. ERK1/2 levels were determined using an ELISA kit. Adenosine and inosine levels were quantified using an enzyme-coupled assay. Adenosine caused cell proliferation through AR activation. Adenosine deaminase increased inosine levels (nanomolar concentrations) on the extracellular space, in a time-dependent manner, inducing proliferation through A3 AR activation. Micromolar concentrations of inosine enhanced proliferation through A3 AR activation, causing an increase in ERK1/2 levels, and P2Y1 R activation via ENT-dependent mechanisms. We propose the simultaneous activation of PLC-PKC-MEK1/2-ERK1/2 and PI3K pathways as the main mechanism responsible for the proliferative effect elicited by inosine and its significant role in melanoma cancer progression.

Mutation-specific RAS oncogenicity explains NRAS codon 61 selection in melanoma

NRAS mutation at codons 12, 13, or 61 is associated with transformation; yet, in melanoma, such alterations are nearly exclusive to codon 61. Here, we compared the melanoma susceptibility of an NrasQ61R knock-in allele to similarly designed KrasG12D and NrasG12D alleles. With concomitant p16INK4a inactivation, KrasG12D or NrasQ61R expression efficiently promoted melanoma in vivo, whereas NrasG12D did not. In addition, NrasQ61R mutation potently cooperated with Lkb1/Stk11 loss to induce highly metastatic disease. Functional comparisons of NrasQ61R and NrasG12D revealed little difference in the ability of these proteins to engage PI3K or RAF. Instead, NrasQ61R showed enhanced nucleotide binding, decreased intrinsic GTPase activity, and increased stability when compared with NrasG12D. This work identifies a faithful model of human NRAS-mutant melanoma, and suggests that the increased melanomagenecity of NrasQ61R over NrasG12D is due to heightened abundance of the active, GTP-bound form rather than differences in the engagement of downstream effector pathways.

SIGNIFICANCE

This work explains the curious predominance in human melanoma of mutations of codon 61 of NRAS over other oncogenic NRAS mutations. Using conditional "knock-in" mouse models, we show that physiologic expression of NRASQ61R, but not NRASG12D, drives melanoma formation.

CD26/DPPIV down-regulation in endometrial stromal cell migration in endometriosis

OBJECTIVE

To test the hypothesis that endometrial stromal cells (ESCs) in endometriosis exhibit increased cell motility under hypoxia.

DESIGN

Prospective case-control study.

SETTING

University research laboratory.

PATIENT(S)

Women with endometriosis (n = 18) or benign gynecological disease (n=19).

INTERVENTION(S)

Eutopic ESCs were cultured under normoxia (20% O2) or hypoxia (6.5% O2), and migration and invasion capacity assayed, with pathway-focused polymerase chain reaction (PCR) array and ELISAs performed. CD26/dipeptidyl peptidase IV (DPPIV) expression was determined by flow cytometric analysis and enzymatic activity assay. The ESCs supplemented with Diprotin A (CD26 inhibitor), stromal cell-derived factor-1α, or AMD3100 (C-X-C motif receptor 4; CXCR4 blocker) were assayed for their migratory potential.

MAIN OUTCOME MEASURE(S)

Endometrial stromal cell migration and invasion under hypoxia.

RESULT(S)

Endometriotic ESCs showed significantly higher migration and invasion through collagen gels under hypoxia compared with nonendometriotic ESCs. The PCR array revealed down-regulation of the migration inhibitor CD26/DPPIV and up-regulation of angiogenic factors (vascular endothelial growth factor A, C-X-C motif Ligand 6; CXCL6) in endometriotic ESCs under hypoxia. The CD26/DPPIV surface expression and activity as well as angiogenic protein secretions suggested that the molecular mechanisms underlying aberrant migratory and angiogenic behavior in endometriotic ESCs. A combinatorial treatment with diprotin A and stromal cell-derived factor-1α effectively enhanced migration and invasion preferentially in endometriotic ESCs cultured hypoxically.

CONCLUSION(S)

Loss of CD26/DPPIV under hypoxia and the subsequent increase in migratory and angiogenic factors may favor conditions for lesion development in endometriosis.

Serum activity of DPPIV and its expression on lymphocytes in patients with melanoma and in people with vitiligo

Background

Dipeptidyl peptidase IV, a multifunctional serine protease, is implicated in regulation of malignant transformation, promotion and further progression of cancer, exerting tumor-suppressing or even completely opposite - tumor-promoting activities.

The aim of present research was to determine the serum DPPIV activity, as well as the percentages of CD26+ lymphocytes, CD26+ overall white blood cells and the mean fluorescence intensity of CD26 expression on lymphocytes in patients with melanoma, people with vitiligo and in healthy controls.

Methods

The activity of DPPIV in serum was determined by colorimetric test. Expression of DPPIV (as CD26) on immunocompetent peripheral white blood cells was done using flow cytometry analysis.

Results

Data from our study show for the first time statistically significant decrease: in the serum DPPIV activity, in the percentage of CD26+ overall white blood cells and in the percentage of lymphocytes in patients with melanoma in comparison to healthy control people. In addition, significantly lower serum DPPIV activity was found in the group of patients with melanoma in relation to people with vitiligo too.

Conclusion

This study indicates the need for exploring the cause and the importance of the disturbances in the serum DPPIV activity and in the CD26 expression on immunocompetent cells in complex molecular mechanisms underlying the development and progression of melanoma.

Potential of soluble CD26 as a serum marker for colorectal cancer detection

Colorectal cancer is characterized by a low survival rate even though the basis for colon cancer development, which involves the evolution of adenomas to carcinoma, is known. Moreover, the mortality rates continue to rise in economically transitioning countries although there is the opportunity to intervene in the natural history of the adenoma–cancer sequence through risk factors, screening, and treatment. Screening in particular accounted for most of the decline in colorectal cancer mortality achieved in the USA during the period 1975-2000. Patients show a better prognosis when the neoplasm is diagnosed early. Among the variety of screening strategies, the methods range from invasive and costly procedures such as colonoscopy to more low-cost and non-invasive tests such as the fecal occult blood test (guaiac and immunochemical). As a non-invasive biological serum marker would be of great benefit because of the performance of the test, several biomarkers, including cytologic assays, DNA and mRNA, and soluble proteins, have been studied. We found that the soluble CD26 (sCD26) concentration is diminished in serum of colorectal cancer patients compared to healthy donors, suggesting the potential utility of a sCD26 immunochemical detection test for early diagnosis. sCD26 originates from plasma membrane CD26 lacking its transmembrane and cytoplasmic domains. Some 90%–95% of sCD26 has been associated with serum dipeptidyl peptidase IV (DPP-IV) activity. DPP-IV, assigned to the CD26 cluster, is a pleiotropic enzyme expressed mainly on epithelial cells and lymphocytes. Our studies intended to validate this test for population screening to detect colorectal cancer and advanced adenomas are reviewed here.

Downregulation of Signaling-active IGF-1 by Dipeptidyl Peptidase IV (DPP-IV)

Functioning as an extracellular protease, dipeptidyl peptidase IV (DPP-IV) preferentially cleaves the peptide bond after the penultimate proline residue. We report here that DPP-IV cleaves the first two amino acids from insulin-like growth factor 1 (IGF-1), revealed by mass spectrometry. The kinetic parameters of the proteolytic cleavage indicate that this reaction is physiologically relevant. Interestingly, truncated IGF-1 is less potent than the full-length protein in activating the IGF-1R, but binds more readily to IGF-binding protein 3 (IGFBP3). Quantitative RT-PCR showed that the level of DPP-IV mRNA is dramatically lower in lung squamous cell carcinoma tissues than in adjacent nonneoplastic lung tissues. However, this reduction was not observed in lung adenocarcinoma tissues. Our study suggests a possible link between IGF-1 and DPP-IV in cancer development in a specific tumor niche. A DPP-IV-related pathway may be important in mitigating IGF-1 signaling. Consequently, a robust IGF signaling pathway may accelerate early carcinogenesis in environments lacking DPP-IV.

On the origin of serum CD26 and its altered concentration in cancer patients

Dipeptidyl peptidase IV (DPP-IV), assigned to the CD26 cluster, is expressed on epithelial cells and lymphocytes and is a multifunctional or pleiotropic protein. Its peptidase activity causes degradation of many biologically active peptides, e.g. some incretins secreted by the enteroendocrine system. DPP-IV has, therefore, become a novel therapeutic target for inhibitors that extend endogenously produced insulin half-life in diabetics, and several reviews have appeared in recent months concerning the clinical significance of CD26/DPP-IV. Biological fluids contain relatively high levels of soluble CD26 (sCD26). The physiological role of sCD26 and its relation, if any, to CD26 functions, remain poorly understood because whether the process for CD26 secretion and/or shedding from cell membranes is regulated or not is not known. Liver epithelium and lymphocytes are often cited as the most likely source of sCD26. It is important to establish which tissue or organ is the protein source as well as the circumstances that can provoke an abnormal presence/absence or altered levels in many diseases including cancer, so that sCD26 can be validated as a clinical marker or a therapeutic target. For example, we have previously reported low levels of sCD26 in the blood of colorectal cancer patients, which indicated the potential usefulness of the protein as a biomarker for this cancer in early diagnosis, monitoring and prognosis. Through this review, we envisage a role for sCD26 and the alteration of normal peptidase capacity (in clipping enteroendocrine or other peptides) in the complex crosstalk between the lymphoid lineage and, at least, some malignant tumours.

Lymphatic-specific expression of dipeptidyl peptidase IV and its dual role in lymphatic endothelial function

Lymphatic vessels play an important role in the maintenance of tissue fluid homeostasis and in the transport of immune cells to lymph nodes, but they also serve as the major conduit for cancer metastasis to regional lymph nodes. However, the molecular mechanisms regulating these functions are poorly understood. Based on transcriptional profiling studies of cultured human dermal lymphatic (LEC) versus blood vascular endothelial cells (BEC), we found that dipeptidyl peptidase IV (DPPIV) mRNA and protein are much more strongly expressed by cultured lymphatic endothelium than by blood vascular endothelium that only expressed low levels of DPPIV in culture. The enzymatic cleavage activity of DPPIV was significantly higher in cultured LEC than in BEC. Differential immunofluorescence analyses of human organ tissue microarrays for DPPIV and several vascular lineage-specific markers revealed that DPPIV is also specifically expressed in situ by lymphatic vessels of the skin, esophagus, small intestine, breast and ovary. Moreover, siRNA-mediated DPPIV knockdown inhibited LEC adhesion to collagen type I and to fibronectin, and also reduced cell migration and formation of tube-like structures. These results identify DPPIV as a novel lymphatic marker and mediator of lymphatic endothelial cell functions.

Comprehensive expression profiling of tumor cell lines identifies molecular signatures of melanoma progression

BACKGROUND

Gene expression profiling has revolutionized our ability to molecularly classify primary human tumors and significantly enhanced the development of novel tumor markers and therapies; however, progress in the diagnosis and treatment of melanoma over the past 3 decades has been limited, and there is currently no approved therapy that significantly extends lifespan in patients with advanced disease. Profiling studies of melanoma to date have been inconsistent due to the heterogeneous nature of this malignancy and the limited availability of informative tissue specimens from early stages of disease.

METHODOLOGY/PRINCIPLE FINDINGS

In order to gain an improved understanding of the molecular basis of melanoma progression, we have compared gene expression profiles from a series of melanoma cell lines representing discrete stages of malignant progression that recapitulate critical characteristics of the primary lesions from which they were derived. Here we describe the unsupervised hierarchical clustering of profiling data from melanoma cell lines and melanocytes. This clustering identifies two distinctive molecular subclasses of melanoma segregating aggressive metastatic tumor cell lines from less-aggressive primary tumor cell lines. Further analysis of expression signatures associated with melanoma progression using functional annotations categorized these transcripts into three classes of genes: 1) Upregulation of activators of cell cycle progression, DNA replication and repair (CDCA2, NCAPH, NCAPG, NCAPG2, PBK, NUSAP1, BIRC5, ESCO2, HELLS, MELK, GINS1, GINS4, RAD54L, TYMS, and DHFR), 2) Loss of genes associated with cellular adhesion and melanocyte differentiation (CDH3, CDH1, c-KIT, PAX3, CITED1/MSG-1, TYR, MELANA, MC1R, and OCA2), 3) Upregulation of genes associated with resistance to apoptosis (BIRC5/survivin). While these broad classes of transcripts have previously been implicated in the progression of melanoma and other malignancies, the specific genes identified within each class of transcripts are novel. In addition, the transcription factor NF-KB was specifically identified as being a potential "master regulator" of melanoma invasion since NF-KB binding sites were identified as consistent consensus sequences within promoters of progression-associated genes.

CONCLUSIONS/SIGNIFICANCE

We conclude that tumor cell lines are a valuable resource for the early identification of gene signatures associated with malignant progression in tumors with significant heterogeneity like melanoma. We further conclude that the development of novel data reduction algorithms for analysis of microarray studies is critical to allow for optimized mining of important, clinically-relevant datasets. It is expected that subsequent validation studies in primary human tissues using such an approach will lead to more rapid translation of such studies to the identification of novel tumor biomarkers and therapeutic targets.

Loss of dipeptidyl peptidase IV immunostaining discriminates malignant melanomas from deep penetrating nevi

The deep penetrating nevus is a rare variant of benign melanocytic nevus with histologic features mimicking vertical growth phase, nodular malignant melanoma. In this study, we expand on the search for new complementary discriminating markers by analyzing a selection of both cell cycle-related factors, such as retinoblastoma protein and phospho-retinoblastoma protein Ser795 as indicators for retinoblastoma protein activation/inactivation status, and invasion-related factors, such as matrix metalloproteinase-1, matrix metalloproteinase-2, membrane-type matrix metalloproteinase-1 and integrin beta3. MIB-1/Ki-67 was analyzed as an example for a common proliferation marker. Dipeptidyl peptidase IV/CD26 was analyzed as a marker affecting both proliferation and invasion of malignant melanocytic tumors. Semiquantitative assessment of both immunolocalization and immunoreactivity of retinoblastoma protein and phospho-retinoblastoma protein Ser795, MIB-1/Ki-67, matrix metalloproteinase-1, matrix metalloproteinase-2, membrane-type matrix metalloproteinase-1 and integrin beta3 revealed no consistent differences between deep penetrating nevi (n=14) and matched cases of nodular malignant melanomas (n=10). Matrix metalloproteinase-1 and matrix metalloproteinase-2 immunostaining of some deep penetrating nevi even exceeded that of nodular malignant melanomas. Membrane-type matrix metalloproteinase-1 expression scores of nodular malignant melanomas were higher than those of deep penetrating nevi, which was, however, not significantly discriminative. In contrast, immunostaining of dipeptidyl peptidase IV was significantly discriminative due to a consistent lack of dipeptidyl peptidase IV-expression in nodular malignant melanomas. These results add evidence that among the selected markers supposed to be relevant for melanoma progression the presence of dipeptidyl peptidase IV can be used to support diagnosis of deep penetrating nevi in doubtful cases. As loss of dipeptidyl peptidase IV may also be causally linked to the transition of invasive to metastatic phenotypes, the molecular mechanisms downstream of dipeptidyl peptidase IV deserve to be studied in more detail in future investigations.

Dipeptidyl Peptidase Inhibits Malignant Phenotype of Prostate Cancer Cells by Blocking Basic Fibroblast Growth Factor Signaling Pathway

Dipeptidyl peptidase IV (DPPIV) is a serine protease with tumor suppressor function. It regulates the activities of mitogenic peptides implied in cancer development. Progression of benign prostate cancer to malignant metastasis is linked to increased production of basic fibroblast growth factor (bFGF), a powerful mitogen. In this study, using in vitro model system we show that DPPIV loss is associated with increased bFGF production in metastatic prostate cancer cells. DPPIV reexpression in prostate cancer cells blocks nuclear localization of bFGF, reduces bFGF levels, inhibits mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK)1/2 activation, and decreases levels of urokinase-type plasminogen activator, known downstream effectors of bFGF signaling pathway. These molecular changes were accompanied by induction of apoptosis, cell cycle arrest, inhibition of in vitro cell migration, and invasion. Silencing of DPPIV by small interfering RNA resulted in increased bFGF levels and restoration of mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK)1/2 activation. These results indicate that DPPIV inhibits the malignant phenotype of prostate cancer cells by blocking bFGF signaling pathway.

Clinical and oncologic implications in epigenetic down-regulation of CD26/dipeptidyl peptidase IV in adult T-cell leukemia cells

CD26/dipeptidyl peptidase IV (DPPIV), a T-cell-activation antigen, is a 110-kD type II surface glycoprotein expressed on various types of normal cells. CD26/DPPIV is considered a multifunction housekeeping protein. Malignant cells often show altered CD26/DPPIV expression or no CD26/DPPIV expression, thus suggesting a useful marker for assessing some T-cell malignancies. In this study, cell surface protein and messenger RNA expression profiles for CD26/DPPIV were examined in 49 patients with adult T-cell leukemia (ATL), 10 carriers of human T-lymphotropic virus I (HTLV-I), and 4 HTLV-I-infected cell lines to assess the utility of CD26/DPPIV expression as a useful molecular marker for ATL pathology. In contrast to normal lymphocytes, ATL cells and HTLV-I-infected cell lines apparently down-regulated or completely lost the CD26/DPPIV antigen. Furthermore, the positive rate and antigen density for CD26/DPPIV in ATL cells gradually declined along with the advancement of ATL stage. Analysis of genomic DNA and the CD26/DPPIV transcript showed that CD26- ATL cells possessed faintly detected transcripts of the gene that were aberrantly methylated at the CpG islands within the promoter region in parallel with the advancement of ATL, a finding supported by a rescue experiment for transcript reexpression using 5-azacytidine as demethylation agent. Moreover, there was no relationship between loss of CD26/DPPIV and HTLV-I tax expression. These results indicate that ATL cells down-regulate CD26 antigens by means of epigenetic machinery and that this antigen abnormality is a useful molecular marker for the pathology of ATL.

Dipeptidyl peptidase IV in tumor progression

Dipeptidyl peptidase IV (DPPIV) is a 110-kDa glycoprotein with ubiquitous expression. Several recent studies have shown that DPPIV affects tumor progression in several human malignancies. We found that ovarian carcinoma cell lines with higher DPPIV expression showed less invasive potential. Furthermore, introduction of DPPIV cDNA into SKOV3 cells (SKDPIV), derived from serous cystadenocarcinoma showing little DPPIV expression, caused a significant decrease in both migration and invasive potential. In addition, nude mice inoculated with SKDPIV cells showed significantly less peritoneal dissemination and longer survival time than those inoculated with parental or vector-transfected cells. We further examined the mechanisms of anti-invasive ability of DPPIV. The expression of E-cadherin was positively correlated with DPPIV expression among five independent ovarian carcinoma cell lines. The SKDPIV cells showed enhanced expression of E-cadherin with a cellular morphological change from a fibroblastic and motile phenotype to an epithelial phenotype compared to parental and MOCK cells. In addition, matrix metalloproteinase 2 (MMP-2) and membrane type 1 matrix metalloprotease (MT1-MMP), which are important markers associated with invasive and metastatic potential, were remarkably reduced in SKDPIV cells. In contrast, tissue inhibitors of matrix metalloproteinases (TIMPs) were enhanced by DPPIV transfection. These findings imply that DPPIV may functionally suppress peritoneal dissemination and progression of ovarian carcinoma by regulating the expression levels of several molecules associated with carcinoma cell invasion and progression.

FAPalpha, a surface peptidase expressed during wound healing, is a tumor suppressor

Fibroblast activation protein-alpha (FAP) is a cell surface serine protease expressed at sites of tissue remodeling in embryonic development. FAP is not expressed by mature somatic tissues except activated melanocytes and fibroblasts in wound healing or tumor stroma. FAP expression is specifically silenced in proliferating melanocytic cells during malignant transformation. To study the role of FAP as a tumor suppressor, the gene for mouse fap was cloned and mutated at the catalytic domain (FAP serine mutant, FSM). We found that expression of FAP or FSM at physiologic levels in mouse melanoma cells abrogated tumorigenicity. Remarkably, the mutant form FSM lacking specific serine protease activity was a more potent tumor suppressor. Tumor rejection was not due to adaptive immune responses because RAG1-/- mice challenged with melanoma cells expressing either FAP or FSM were not tumorigenic. In in vitro assays, FAP or FSM expression restored contact inhibition, led to cell cycle arrest at G0/G1 phase, and increased susceptibility to stress-induced apoptosis. Cell death in FAP+ or FSM+ melanoma cells was readily triggered by depletion of survival factors from the media, leading to subsequent activation of caspases via the intrinsic pathway. These results show that expression of FAP is a tumor suppressor that abrogates tumorigenicity through regulation of cell growth and survival.

Adenosine down-regulates the surface expression of dipeptidyl peptidase IV on HT-29 human colorectal carcinoma cells: implications for cancer cell behavior

Dipeptidyl peptidase IV (DPPIV) is a multifunctional cell-surface protein that, as well as having dipeptidase activity, is the major binding protein for adenosine deaminase (ADA) and also binds extracellular matrix proteins such as fibronectin and collagen. It typically reduces the activity of chemokines and other peptide mediators as a result of its enzymatic activity. DPPIV is aberrantly expressed in many cancers, and decreased expression has been linked to increases in invasion and metastasis. We asked whether adenosine, a purine nucleoside that is present at increased levels in the hypoxic tumor microenvironment, might affect the expression of DPPIV at the cell surface. Treatment with a single dose of adenosine produced an initial transient (1 to 4 hours) modest (approximately 10%) increase in DPPIV, followed by a more profound (approximately 40%) depression of DPPIV protein expression at the surface of HT-29 human colon carcinoma cells, with a maximal decline being reached after 48 hours, and persisting for at least a week with daily exposure to adenosine. This down-regulation ofDPPIV occurred at adenosine concentrations comparable to those present within the extracellular fluid of colorectal tumors growing in vivo, and was not elicited by inosine or guanosine. Neither cellular uptake of adenosine nor its phosphorylation was necessary for the down-regulation of DPPIV. The decrease in DPPIV protein at the cell surface was paralleled by decreases in DPPIV enzyme activity, binding of ADA, and the ability of the cells to bind to and migrate on cellular fibronectin. Adenosine, at concentrations that exist within solid tumors, therefore acts at the surface of colorectal carcinoma cells to decrease levels and activities of DPPIV. This down-regulation of DPPIV may increase the sensitivity of cancer cells to the tumor-promoting effects of adenosine and their response to chemokines and the extracellular matrix, facilitating their expansion and metastasis.

Role for dipeptidyl peptidase IV in tumor suppression of human non small cell lung carcinoma cells

Lung cancer is the leading cause of cancer death. Lung cancers produce a variety of mitogenic growth factors that stimulate tumor cell proliferation and migration. The cell surface protease, dipeptidyl peptidase IV (DPPIV), is involved in diverse biologic functions, including peptide-mediated cellular growth and differentiation. DPPIV is expressed in various normal tissues, including lung tissue, and its expression is lost in many types of human cancers. DPPIV expression and its enzymatic activity are detected in normal bronchial and alveolar epithelium but different histologic subtypes of lung carcinomas lose DPPIV expression. To investigate the role of DPPIV in lung carcinoma, we examined the expression of DPPIV at both mRNA and protein levels in non small cell lung cancer (NSCLC) cell lines and normal human bronchial epithelial cells. DPPIV expression was detectable in normal lung epithelial cells, but was absent or markedly reduced in all NSCLC cell lines at both mRNA and protein levels. Restoration of DPPIV expression in NSCLC cells resulted in profound morphologic changes, inhibition of cell proliferation, anchorage-independent growth, in vitro cell migration and tumorigenicity in nude mice. DPPIV reexpression also correlated with increased p21 expression, leading to induction of apoptosis and cell cycle arrest in G1 stage. These effects were accompanied by increased expression of cell surface proteins, fibroblast-activating protein (Fapalpha) and CD44 that are associated with suppression of tumor growth and metastasis. Thus, DPPIV functions as a tumor suppressor, and its downregulation may contribute to the loss of growth control in NSCLC cells.

Cell surface adenosine deaminase binds and stimulates plasminogen activation on 1-LN human prostate cancer cells

Adenosine deaminase (ADA) is expressed intracellularly by all cells, but in some tissues, it is also associated with the cell surface multifunctional glycoprotein CD26/dipeptidyl peptidase IV. By modulating extracellular adenosine, this "ecto-ADA" may regulate adenosine receptor signaling implicated in various cellular functions. CD26 is expressed on the surface of human prostate cancer 1-LN cells acting as a receptor for plasminogen (Pg). Since ADA and Pg bind to CD26 at distinct but nearby sites, we investigated a possible interaction between these two proteins on the surface of 1-LN cells. Human ADA binds to CD26 on the surface 1-LN cells and immobilized CD26 isolated from the same cells with similar affinity. In both cases, ADA binding is diminished by mutation of ADA residues known to interact with CD26. ADA was also found to bind Pg 2 in the absence of CD26 via the Pg kringle 4 (K4) domain. In the presence of 1-LN cells or immobilized CD26, exogenous ADA enhances conversion of Pg 2 to plasmin by 1-LN endogenous urinary plasminogen activator (u-PA), as well as by added tissue Pg Activator (t-PA), suggesting that ADA and Pg bind simultaneously to CD26 in a ternary complex that stimulates the Pg activation by its physiologic activators. Consistent with this, in melanoma A375 cells that bind Pg, but do not express CD26, the rate of Pg activation was not affected by ADA. Thus, ADA may be a factor regulating events in prostate cancer cells that occur when Pg binds to the cell surface and is activated.

Increased adhesion potency of ovarian carcinoma cells to mesothelial cells by overexpression of dipeptidyl peptidase IV

Dipeptidyl peptidase IV (DPPIV), cell surface peptidase, works as an adhesion molecule as well as an enzyme. To investigate the role of DPPIV as an adhesion molecule of ovarian carcinoma cells to mesothelial cells, ovarian carcinoma (SKOV3 and NOS4) cells were transfected with a sense and an antisense cDNA coding human DPPIV. The adhesion potency of these transfected cells to fibronectin- and collagen-coated plates and mesothelial cells were examined with or without fibronectin. Flow cytometry and immunohistochemistry demonstrated DPPIV in ovarian carcinoma cells. The adhesion rate of DPPIV-transfected SKOV3 (SKDPIV) cells to fibronectin-coated plates was significantly higher than SKOV3 cells, while there was no difference in the adhesion rate to non-coated plates between SKDPIV and SKOV3 cells. The adhesion rates of vector-transfected SKOV3 (SKpcDNA) cells to coating and noncoating plates were similar to those of SKOV3 cells. SKDPIV cells showed twofold adhesion potency to mesothelial cells compared to SKOV3 cells. Furthermore, an addition of soluble fibronectin resulted in a dose-dependent increase in the adhesion rate of SKDPPIV cells, but not in either SKOV3 or SKpcDNA cells. Antisense-transfected NOS4 cells decreased the adhesion potency compared to NOS4 and vector-transfected NOS4 cells. In conclusion, ovarian carcinoma cells express DPPIV and adhere to human mesothelial cells in part by DPPIV. This adhesion mechanism of DPPIV is mediated by immobilized and soluble fibronectin.

Fibroblast activation protein: differential expression and serine protease activity in reactive stromal fibroblasts of melanocytic skin tumors

Growth and metastasis of solid neoplasms require the recruitment of a supporting tumor stroma. A highly consistent trait of tumor stromal fibroblasts in most epithelial cancers is the induction of fibroblast activation protein (FAP), a member of the serine protease family. Recently it was demonstrated that FAP has both dipeptidyl peptidase and collagenolytic activity capable of degrading gelatin and type I collagen. In this study, we describe the expression and enzyme activity of FAP in benign and malignant melanocytic skin tumors. FAP-positive fibroblasts were detected immunohistochemically in the reactive stroma of all melanocytic nevi tested. In primary and metastatic melanomas an upregulation of FAP expression in the reactive mesenchyme could be observed. Whereas 30% of the nevi revealed additional FAP expression on subsets of melanocytic cells, melanoma cells from primary and metastatic melanomas were FAP negative. This may indicate a possible role for FAP in the control of tumor cell growth and proliferation during melanoma carcinogenesis. Consistent with this in vivo expression pattern FAP enzyme activity could be detected by a specific immunocapture assay in extracts of melanocytic nevi and melanoma metastases, whereas no significant activity was detectable in normal adult skin. Strong protein expression of FAP was observed in patterned structures restricted to a subset of the melanoma metastases. Our findings that these FAP-positive structures showed no overlap with endothelial cell surface markers, nor with various melanoma antigens, suggest that FAP is a marker for specific stromal-cell-derived patterns in cutaneous melanoma metastases.

Cell-surface proteolysis, growth factor activation and intercellular communication in the progression of melanoma

Normal skin architecture and melanocyte function is maintained by a dynamic interplay between the melanocytes themselves, the epithelial cells between which they are interspersed, and their microenvironment. The microenvironment consists of the extracellular matrix, fibroblasts, migratory immune cells, and neural elements supported by a vascular network, all within a milieu of cytokines, growth factors, and bioactive peptides as well as proteolytic enzymes. Cells interact with the microenvironment via complex autocrine and paracrine mechanisms. Proteolytic enzymes in melanoma may activate or release growth factors from the microenvironment or act directly on the microenvironment itself, thereby facilitating angiogenesis or tumor cell migration. This review summarizes recent findings regarding the expression, structure and function of proteolytic enzymes at or near the cell surface in cell-cell and cell-stroma interactions during melanoma progression. Cell-surface (membrane) peptidases are a multi-functional group of ectoenzymes that have been implicated in the control of growth and differentiation of many cellular systems. The potential, but yet speculative, role of other membrane-bound molecules, such as multifunctional surface proteins with adhesion and protease activity (ADAM gene family) or the ephrin/Eph receptor protein kinases in the pathogenesis of melanoma are discussed.

Dipeptidyl peptidase IV (DPPIV) inhibits cellular invasion of melanoma cells

Dipeptidyl peptidase IV (DPPIV) is a 110-kD, trans-membrane, ectoenzyme, with ubiquitous expression. DPPIV has numerous functions including involvement in T-cell activation, cell adhesion, digestion of proline containing peptides in the kidney and intestines, HIV infection and apoptosis, and regulation of tumorigenicity in certain melanoma cells. Constitutively expressed on numerous epithelial cell types, DPPIV is often disregulated in a variety of human malignancies. The most striking evidence of DPPIV down-regulation is found in transformed melanocytes. where nearly 100% of melanomas lack DPPIV expression. We have identified DPPIV as a gene that can alter the invasive potential of a number of melanoma cell lines. By transfecting the full-length cDNA of DPPIV, we have established stable melanoma cell lines that express comparable levels of the DPPIV protein as normal epidermal melanocytes. Matrigel invasion assays were utilized to study the effects of DPPIV expression on the invasive potential of these cells. The parental and vector transfectants readily migrated across the Matrigel while the invasiveness of DPPIV transfected cells was reduced by greater than 75%. The effects on cellular invasion are not attributed to overall growth characteristics, as both DPPIV expressing and non-expressing cells behave comparably in culture. We have also constructed mutants of DPPIV that lack either the extra-cellular serine protease activity or the six amino acid cytoplasmic domain. Both mutants were stably expressed in melanoma cells. Matrigel invasion assays performed with cells expressing the two mutant forms of the protein revealed phenotypic effects similar to wild type function. In this study. we have demonstrated that expression of a proteolytically active form of the DPPIV protein inhibits the invasiveness of malignant melanoma cell lines lacking endogenous DPPIV expression. Furthermore, we have shown that neither the protease activity nor the cytoplasmic domain of DPPIV is required for its anti-invasive activity.

Hepatocyte growth factor and melanoma: gene transfer studies in human melanocytes

Hepatocyte growth factor (HGF), a fibroblast-derived protein that affects the growth, motility and differentiation of epithelial cells, is a mitogen for human melanocytes and has recently been implicated as an important factor for the development and dissemination of melanomas. To better define the possible role of HGF in the multi-step progression from melanocyte to melanoma cell, we used retrovirus-mediated gene transfer to introduce the gene encoding human HGF into normal human melanocytes, thus causing these cells to produce a growth factor they do not normally express and creating a new autocrine loop as sometimes occurs in melanoma cells. Cells were transduced with an efficiency of 6%, and the modified cells synthesized and secreted significant levels of HGF (6.6 ng/10(7) cells per 24 h) in vitro. Cells expressing HGF had a higher rate of proliferation when compared with unmodified cells and formed large, dense, melanin-positive colonies on a plastic surface. Immunostaining showed HGF-positive melanocytes with varying levels of expression, and HGF protein was detected throughout the whole cell. Although proliferation of HGF-expressing melanocytes was enhanced, they failed to form colonies in a soft agar assay. These results suggest that expression of HGF, by virtue of its ability to enhance proliferation and cell clustering, may play a role in the multi-step process of transformation, but an autocrine signal of HGF alone is not sufficient for malignant transformation.

A role for dipeptidyl peptidase IV in suppressing the malignant phenotype of melanocytic cells

Dipeptidyl peptidase IV (DPPIV) is a cell surface peptidase expressed by normal melanocytes, epithelial cells, and other cells. Malignant cells, including melanomas and carcinomas, frequently lose or alter DPPIV cell surface expression. Loss of DPPIV expression occurs during melanoma progression at a stage where transformed melanocytes become independent of exogenous growth factors for survival. Tetracycline-inducible expression vectors were constructed to express DPPIV in human melanoma cells. Reexpressing DPPIV in melanoma cells at or below levels expressed by normal melanocytes induced a profound change in phenotype that was characteristic of normal melanocytes. DPPIV expression led to a loss of tumorigenicity, anchorage-independent growth, a reversal in a block in differentiation, and an acquired dependence on exogenous growth factors for cell survival. Suppression of tumorigenicity and reversal of a block in differentiation were dependent on serine protease activity, assessed using mutant DPPIV molecules containing serine-->alanine substitutions. Surprisingly, dependence on exogenous growth factors was not dependent on serine protease activity. Reexpression of either wild-type or mutant DPPIV rescued expression of a second putative cell surface serine peptidase, fibroblast activation protein alpha, which can form a heterodimer with DPPIV. This observation suggests that rescue of fibroblast activation protein alpha may play a role in regulating growth of melanocytic cells. These results support the view that downregulation of DPPIV is an important early event in the pathogenesis of melanoma.

Expression of CD26/dipeptidyl-peptidase IV in benign and malignant pigment-cell lesions of the skin

The T-cell activation antigen CD26 or dipeptidyl-peptidase IV (DPP-IV) belongs to a group of membrane-bound proteases that are variably expressed by melanoma cell lines. In vitro studies have suggested that loss of CD26 is associated with tumour progression. To correlate its expression with the histological stage of tumour progression of malignant melanoma (MM), we studied the distribution of CD26/DPP-IV in paraffin sections of a series of 110 benign and malignant pigment-cell lesions of the skin using a cocktail of anti-CD26 monoclonal antibodies and the three-step ABC method. Only two of 44 benign lesions focally expressed CD26 in their junctional compartment. In MM, expression of CD26 was not related to any of the known histological prognostic factors, but was associated with the stage of tumour progression; thus, CD26 was expressed in the situ or invasive radial growth phase in 34% of MM, whereas only 12% of MM expressed CD26 in the vertical growth phase. No CD26 expression occurred in metastatic melanomas. These data suggest that this proteinase plays a part in the early invasion of MM. Thus, CD26 may serve in the binding to, and enzymatic degradation, components of the extracellular matrix of the papillary dermis. Loss of CD26 in the vertical growth phase may contribute to the insufficient inactivation of regulatory peptides and unlimited action of growth factors.

Altered Regulation of Cell Surface Peptidases in Human Cholesteatoma

Cholesteatoma is a destructive process involving an accumulation of desquamated keratin arising from squamous epithelium that pathologically has invaded the middle ear or mastoid process. The clinical hallmarks of cholesteatomas, namely invasion of healthy tissues, migration, unrestrained proliferation, aggressiveness, recidivism, and uncoordinated differentiation predict the existence of defects in the normal biology and biochemistry of the cellular constituents that compose a cholesteatoma, as well as in the cellular interactions between these cells, the surrounding normal tissue, and the host. In the current report, we analyzed 11 cholesteatomas and matched healthy tissue for altered expression in four different cell surface peptidases, aminopeptidase A, aminopeptidase N, dipeptidyl peptidase IV, and neutral endopeptidase. We suggest that peptidases may modulate cell growth and differentiation by inactivating stimulatory signals (or conversely, by activating inhibitory signals).

Melanoma cells and normal melanocytes share antigens recognized by HLA-A2-restricted cytotoxic T cell clones from melanoma patients

HLA-A2-restricted, CD3+, CD8+, alpha/beta+ cytotoxic T cell (CTL) clones were isolated from peripheral blood (PBL) or tumor infiltrating lymphocytes (TIL) of two HLA-A2+ melanoma patients (9742 and 5810), to evaluate the possible recognition of autologous melanoma and of allogeneic HLA-A2-matched normal melanocytes. These CTL clones lysed not only fresh and cultured autologous melanoma cells, but also allogeneic HLA-A2+, but not HLA-A2-, normal melanocytes. The lysis of autologous neoplastic cells and of melanocytes could be inhibited by an anti-HLA-A2 monoclonal antibody (mAb). Lysis of the normal melanocytes was not dependent on the presence of human or fetal calf serum in the culture medium. HLA-A2-restricted CTL clones recognized not only proliferating melanocytes cultured in complete melanocyte medium, but also melanocytes made quiescent by culture for up to 6 d in a basal medium devoid of exogenous factors such as phorbol ester (O-tetradecanoyl phorbol 13-acetate [TPA]), epidermal growth factor, insulin, and pituitary extracts. Analysis of specificity of four CTL clones (A75, A83, A94, and 119) from patient 9742, performed on a panel of 39 targets, indicated that the three HLA-A2-restricted CTL (A75, A83, and A94) lysed all but one of nine allogeneic melanomas expressing the HLA-A2 molecule with no reactivity on nine HLA-A2- allogeneic melanomas. Only a few instances of borderline reactivity were seen by the same effectors on 21 targets of nonmelanocyte lineage, including 12 carcinomas of different histology, four Epstein-Barr virus-transformed B cells (lymphoblastoid cell lines [LCL]), including the autologous LCL, four lines of normal fibroblasts, and normal kidney cells. Lack of reactivity on allogeneic targets of nonmelanocyte lineage occurred in spite of expression of HLA-A2 on 14 of these targets as determined by conventional tissue typing and cytofluorimetric analysis with four different anti-HLA-A2 mAb. These data indicate that tissue-related antigens can be expressed on normal and neoplastic cells of the melanocyte lineage and can be recognized in association with HLA-A2 by CTL clones from melanoma patients.

A marker for neoplastic progression of human melanocytes is a cell surface ectopeptidase

Adenosine deaminase binding protein (ADAbp) is a cell surface glycoprotein that is expressed by normal melanocytes but not by melanoma, the malignant counterpart. ADAbp is specifically downregulated during malignant transformation of melanocytes. Recently, we have developed a system that progressively transforms melanocytes in vitro in defined steps. Transduction with v-Ha-ras oncogene followed by long-term culture leads to a cell phenotype and genotype that specifically mimics human melanoma. Loss of ADAbp expression occurred concomitantly with the emergence of growth factor independence and appearance of specific chromosomal abnormalities. The cellular function of ADAbp has not been defined. To characterize ADAbp, the mature 110-kD form was purified from human kidney. Five tryptic peptides from purified human ADAbp revealed 100% homology to a serine protease, human dipeptidyl peptidase IV (DPP IV), also known as CD26. DPP IV activity was detected in lysates from human melanocytes and renal carcinoma cells but not melanoma cells, and DPP IV activity could be specifically isolated from melanocytes by binding to ADA or to S27 monoclonal antibody against ADAbp. These findings show that ADAbp is a cell surface ectopeptidase that is tightly regulated during neoplastic transformation of melanocytes.

Distribution of adenosine deaminase binding protein in normal and malignant tissues of the gastrointestinal tract studied by monoclonal antibodies

A mouse monoclonal antibody V-715 was raised against fresh colon cancer tissues. Biochemical analysis elucidated that the antigen defined was adenosine deaminase binding protein (ADBP). In colon cancer cell lines, V-715 was positive in 8 out of 16 differentiated cancers and in 2 out of 8 poorly differentiated cancers. In frozen sections, ADBP was expressed in 17 out of 33 differentiated colon cancers, but none of 4 poorly differentiated colon cancers. In normal colon, the expression was observed in epithelium. In gastric cancers, ADBP was expressed in 10 out of 15 differentiated cancers, but weakly or only heterogenously expressed in 2 out of 8 poorly differentiated cancers. In normal gastric mucosa, ADBP was mainly detected in the foveolar epithelium, but was weakly or not expressed in the deep gastric glands. Carcinoid tumors and malignant lymphoma of the stomach did not express ADBP. These results suggest that ADBP may act as a marker of enterocytic differentiation in normal and neoplastic gastrointestinal cells, and might be exploitable in clinical and pathological diagnosis of gastrointestinal cancers.

Molecular genetics of human malignant melanoma

Due to a variety of known and unknown control mechanisms, the human genome is remarkably stable when compared to most other species. The long latency periods of most solid tumors, during which the cell undergoes malignant transformation, are presumably due to this stability. The molecular basis responsible for the induction of genetic instability and the resultant biological characteristics manifest in tumor populations is not well understood. The discovery of both oncogenes and tumor suppressor genes, however, has placed the phenomenon of human genome stability on a more solid conceptual footing. These types of genes clearly place multiple barriers to oncogenic transformation, and traversing these barriers apparently requires both time and the accumulation of genetic defects that cannot be corrected. The evolution of neoplasias can, therefore, be predicted to be due to: (1) consistent and progressive loss of tumor suppressor genes; (2) gene amplification, resulting in the over-expression of proteins that aid in tumor progression; (3) gene mutation, which alters the orderly biochemistry of the normal cell; (4) genes that allow a cell like the melanocyte to escape the confining nature of the epidermis and to invade through the dermis into the circulatory and lymphatic systems in order to disseminate itself to other organs (e.g., proteolytic enzymes, enzyme inhibitors, integrins, metastases genes, chemotactic factors etc.); (5) factors, perhaps such as TGF beta 2, that may impact negatively on MHC antigens and confuse host defense mechanisms; and (6) S.O.S.-type genes, which may be expressed as a direct response to the accumulating damage in an attempt to correct the damage, but that may then become part of the problem instead of the solution. The extraordinary plasticity and instability of the genome of a melanoma cell suggests an inordinate amount of genetic flux. In addition to activating and inactivating various genes, this constant shuffling and rearranging of the genome in neoplasms such as MM may be constantly altering gene dose. Cytogenetic and molecular biological studies have been the Rosetta stone for understanding the etiological relevant genetic events in human cancers. Genetic alterations fundamental to the pathology of MM have begun to be defined. Studies designed to understand these perturbations at the biochemical and organismic level are underway.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigens of melanocytes and melanoma

Melanoma is a valuable model to study phenotypic traits that are regulated during cell differentiation and malignant transformation. Melanoma cells display extensive phenotypic and antigenic heterogeneity. Studies of this attribute have provided insight into events that take place during normal melanocyte differentiation and give clues to traits that contribute to malignancy. It is possible that the phenotypic and genotypic heterogeneity present among melanoma cells within a single lesion includes a subset of cells with traits that favor tumor progression and metastasis. This review discusses the identification and characterization of antigens expressed by melanoma cells and their potential contribution to melanocyte differentiation and malignant transformation.

Human melanoma: development and progression

Clinical and histopathological evidence suggests that melanoma develops in a sequence of steps, progressing from benign proliferative lesions, to primary melanomas that do not show evidence for metastasis, to invasive primary lesions, and to metastases. This review focuses on the experimental studies examining the phenotypic characteristics of cultured primary melanoma cells as they relate to cells from non-malignant nevi and metastases. Genetic, biologic, and immunologic criteria have been established to distinguish melanocytes from different steps of tumor development. These include non-random chromosomal abnormalities, expression of melanocyte- and melanoma-specific antigens, requirements for exogenous growth factors, production of endogenous growth factors, and expression of receptors for growth factors. The transformation of melanocytes and nevus cells with viral oncogenes has facilitated studies on the malignant phenotype. Variants have been developed through successive selections from primary melanoma cell populations that have one or several characteristics of metastatic cells. The study of melanocytes isolated from various stages of tumor development and the generation of cell variants with specific properties should enable a long-term search for the molecular mechanisms of melanoma development and progression.

Adenosine deaminase complexing protein (ADCP) expression and metastatic potential in prostatic adenocarcinomas

The expression of the adenosine deaminase complexing protein (ADCP) was investigated by immunohistochemistry in the normal and hyperplastic human prostate, in 30 prostatic adenocarcinomas, and in seven human prostatic adenocarcinoma cell lines grown as xenografts in athymic nude mice. In the normal and hyperplastic prostate, ADCP was localized exclusively in the apical membrane and the apical cytoplasm of the glandular epithelial cells. In prostatic adenocarcinomas, four distinct ADCP expression patterns were observed: diffuse cytoplasmic, membranous, both cytoplasmic and membranous, and no ADCP expression. The expression patterns were compared with the presence of metastases. We found an inverse correlation between membranous ADCP immunoreactivity and metastatic propensity. Exclusively membranous ADCP immunoreactivity occurred only in non-metastatic tumours. In contrast, the metastatic tumours showed no or diffuse cytoplasmic ADCP immunoreactivity. This suggests that immunohistochemical detection of ADCP might predict the biological behaviour of prostatic cancer. However, the occurrence of membranous ADCP immunoreactivity in the xenograft of a cell line (PC-EW), derived from a prostatic carcinoma metastasis, indicates that not only the tendency to metastasize modulates ADCP expression.

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.

Bowes human melanoma cell line. An immunocytochemical study

Bowes human melanoma cell line was investigated immunocytochemically to localize S-100 protein, HMB-45 and intermediate filament proteins. The majority of the cells showed strong positive staining with antibodies directed against S-100 protein, HMB-45 and vimentin filaments. Antibodies directed against the other cytoskeletal proteins failed to show any reactivity. These findings suggest that this transformed cell line does not dedifferentiate in culture and continues to express the specific antigens of human melanoma cells. Thus, Bowes cell line provides a useful model for studying the cellular biology and pathology of malignant melanoma.

Transformation of human kidney proximal tubule cells by ras-containing retroviruses. Implications for tumor progression

Normal human kidney proximal tubule cells into which a ras oncogene was inserted undergo a series of transformation-related alterations that are characteristic of renal carcinomas. These include changes in morphology, growth potential, anchorage dependence, antigen expression, growth factor production, and chromosomal stability. Further, there are spontaneous progressive alterations in vitro in the karyotype and antigenic profile of the transformed cells. Cytogenetic analyses suggest that alterations of chromosome 21 may play an early and pivotal role in the development of transformed proximal tubule cells.