Faculty Bibliography

A critical requirement to use tumor antigens as vaccines is that they stimulate CD8+ T cell responses. In this study, we tested the ability of a shed, polyvalent, melanoma antigen vaccine to induce such responses to the melanoma-associated antigens, MAGE-3 and MART-1/Melan-A. Fifteen HLA-A2+ patients with resected malignant melanoma were immunized to the vaccine sc every 2-3 weeks x 4, and monthly thereafter. CD8+ T cells in peripheral blood reacting to HLA-A2 restricted epitopes on MAGE-3 (FLWGPRALV) and/or MART-1/Melan-A (AAGIGILTV) were quantitated directly using a filter spot assay at baseline and following 4 immunizations. Vaccine immunization induced CD8+ T cells reacting specifically to one or both of these antigens in 9 (60%) patients. These cells were CD8+ and HLA-A2 restricted, as reactivity was abrogated by monoclonal antibodies to CD8 and to class I HLA, but not by anti-CD4. The CD8+ T cells were specifically directed to these antigens, as they did not react to the same targets pulsed with a control HLA-A2 restricted peptide recognized by T cells. All responding patients remained recurrence-free during a follow-up of 12-21 months, whereas melanoma recurred within 3-5 months in non-responders. The differences in outcome were unrelated to differences in disease-severity or overall immunological competence between CD8+ T cell responders and non-responders. These results demonstrate that a polyvalent vaccine can stimulate a CD8+ T cell response to MAGE-3 and MART-1/Melan-A in humans, and suggest that the responses are protective and surrogate markers of vaccine efficacy. (C) American Society of Clinical Oncology 1997

Evidence suggests that the plasminogen activators (PAs), in particular urokinase-type PA (uPA), play a pivotal role in tumor invasion and metastasis. We studied the contribution of the PAs to the malignant phenotype through the chemical induction of melanocytic neoplasms in uPA-deficient mice. Primary tumors were induced and promoted concurrently in 35 uPA-/- deficient and 35 uPA+/+ wild-type mice using a single application of 7,12-dimethylbenz(a)anthracene followed by repetitive applications of croton oil. Animals were sacrificed at 60-day intervals for 1 year. At necropsy, the four largest pigmented lesions in each animal were excised, characterized histologically, and evaluated microscopically for evidence of invasion. The regional lymph nodes, lungs, and solid abdominal visceral organs were sectioned and examined microscopically for evidence of metastatic disease. Cellular blue nevi were induced in 100% of uPA-/- and uPA+/+ promoted animals. Although a reduction in the radial and vertical progression of these lesions was noted in the uPA-deficient mice compared with the wild-type group, more than 95% of cellular blue nevi induced in both groups of animals invaded the underlying tissues. These lesions did not metastasize to the regional lymph nodes. Malignant melanoma arose in 5 of 35 (14.3%) of promoted wild-type mice. These tumors were locally aggressive, produced tissue-type PA, but were not metastatic to the regional nodes, lungs, or abdominal viscera. These results indicate that the invasive capability of melanocytic lesions may depend more on tissue-type PA than uPA activity. No melanomas were induced in the uPA-/- mice. The resistance of the uPA -/- strain to melanoma induction suggests that uPA contributes to malignant progression. We propose that the absence of uPA negatively affects tumorigenesis by decreasing the liberation and availability of growth factors such as basic fibroblast growth factor

Most cell types express transforming growth factor-beta (TGF-beta) as a large latent TGF-beta complex that must be converted to an active form before TGF-beta can interact with cell surface TGF-beta receptors. This conversion involves the release of mature TGF-beta from the complex by disrupting noncovalent interactions between mature TGF-beta and its propeptide, latency associated peptide. A critical step in regulating TGF-beta effects may be the activation of the large latent TGF-beta complex. Activation of the complex can be achieved by chemical and enzymatic treatments, or by various cell systems. We have identified that coculturing bovine endothelial and smooth muscle cells generates active TGF-beta. Coculture activation of the large latent TGF-beta complex occurs through a plasmin-dependent mechanism that requires concentration of reactants on the cell surface and/or extracellular matrix. The mechanism of latent TGF-beta activation self-regulates through effectors of plasmin generation

An oligodeoxyribonucleotide 5'-d(CTCATGAPATTCC), in which G(AP) denotes N-(guanin-8-yl)-1-aminopyrene, the C8-guanine adduct of reductively activated 1-nitropyrene, was synthesized and characterized by polyacrylamide gel electrophoresis, absorption and fluorescence spectroscopy, circular dichroism, and thermal melting studies. Polyacrylamide gel electrophoresis showed slower mobility of the adducted oligonucleotide in single-stranded form compared to its unmodified counterpart, as expected. In duplex form, however (with a deoxycytidine opposite the adduct), the adducted 11mer migrated faster than the parent duplex. Absorption and fluorescence studies indicated significant interaction of the aminopyrene residue with the DNA bases in the modified 11mer. The spectroscopic data also suggested the presence of one or more conformers in which the aminopyrene residue is quasi-intercalative, as well as one(s) in which the aminopyrene is externally bound. Thermodynamic parameters for the helix-to-coil transitions for the 11mer duplex were determined. The difference in free energy (delta delta G degree) between the unmodified and modified sequences was relatively small (approximately 1.2 kcal/mol). Circular dichroism spectra indicated the presence of essentially B-form DNA. The energy minimizations suggested that the most stable conformers shared a common feature: displacement of the modified guanine from the double helix. In the global minimum, the aminopyrene residue was inserted in the helix in the site of displaced guanine. In other low energy structures, the aminopyrene was also displaced towards the minor groove (in addition to guanine), or partly inserted and partly in the groove. More conventional structures were also encountered, with anti-guanine within the helix and aminopyrene in the major groove, or syn-guanine within the helix, and aminopyrene in the minor groove. Such structures were 12-20 kcal/mol less stable than the global minimum, however. The C8-guanine adduct of aminopyrene thus appears to perturb the B-DNA structure to a greater extent than do the adducts of less bulky amines such as aminofluorene and 4-aminobiphenyl.

Screening of random oligonucleotide libraries with SELEX [systematic evolution of ligands by exponential enrichment; Tuerk, C., & Gold, L. (1990) Science 249, 595-510] has emerged as a powerful method for identifying high-affinity nucleic acid ligands for a wide range of molecular targets, Nuclease sensitivity of unmodified RNA and DNA, however, imposes considerable restrictions on their use as therapeutics or diagnostics. Modified RNA in which pyrimidine 2'-hydroxy groups have been substituted with 2'-amino groups (2'-aminopyrimidine RNA) is known to be substantially more resistant to serum nucleases, We report here on the use of SELEX to identify high-affinity 2'-aminopyrimidine RNA ligands to a potent angiogenic factor, basic fibroblast growth factor(bFGF). High-affinity ligands with the same consensus primary structure have been isolated from two independent libraries of approximately 6 x 10(14) molecules containing 30 or 50 randomized positions. Compared to unmodified RNA with the same sequence, 2'-aminopyrimidine ligands are at least 1000-fold more stable in 90% human serum. The sequence information required for high-affinity binding to bFGF is contained within 24-26 nucleotides. The minimal ligand m21A (5'-GGUGUGUGGAAGACAGCGGGUGGUUC-3'; G = guanosine, A = adenosine, C = 2'-amino-2'-deoxycytidine, U = 2'-amino-2'-deoxyuridine, and C = 2'-amino-2'-deoxycytidine or deoxycytidine) binds to bFGF with an apparent dissociation constant (K-d) of (3.5 +/- 0.3) x 10(-10) M at 37 degrees C in phosphate-buffered saline (pH 7.4). Dissociation of m21A from bFGF is adequately described with a first-order rate constant of (1.96 +/- 0.08) x 10(-3) s(-1) (t(1/2) = 5.9 min). The calculated value for the association rate constant (k(on) = k(off)/K-d) was 5.6 x 10(6) M(-1) s(-1). Highly specific binding of m21A to bFGF was observed: binding to denatured bFGF, five proteins from the FGF family (acidic FGF, FGF-4, FGF-5, FGF-6, and FGF-7), and four other heparin binding proteins is substantially weaker under the same conditions with K-d(bFGF)/K-d(protein) values ranging from (4.1 +/- 1.4) x 10(-2) to > 10(-6). Heparin but not chondroitin sulfate competed for binding of m21A to bFGF. In cell culture, m21A inhibited [I-125]bFGF binding to both low-affinity sites (ED(50) approximate to 1 nM) and high-affinity sites (ED(50) approximate to 3 nM) on CHO cells expressing transfected FGF receptor-1. Basic FGF-dependent migration of bovine aortic endothelial cells as well as bFGF-induced proliferation of human umbilical vein endothelial cells was also inhibited by m21A in a concentration-dependent manner with ED(50) values of 50-100 nM. The 2'-aminopyrimidine RNA ligand m21A therefore represents a useful lead compound in our efforts to develop potent oligonucleotide-based angiogenesis antagonists

Transforming growth factor-beta (TGF-beta) is secreted by most cells as a biologically inactive complex, called the large latent TGF-beta complex. The complex is comprised of latent TGF-beta binding protein (LTBP) and latent TGF-beta, which is mature TGF-beta associated noncovalently with its amino-terminal propeptides. LTBP is disulfide-linked to the amino-terminal propeptide of latent TGF-beta. Active TGF-beta is generated by release of TGF-beta from the complex. Generation of active TGF-beta by macrophages has been reported, but the activation mechanism has not been described. Latent TGF-beta activation by macrophages was characterized using serum-free cultures of resident and thioglycollate-elicited murine peritoneal macrophages that were either unstimulated or LPS-stimulated in vitro. Serum-free conditioned medium was assayed for TGF-beta using a quantitative luciferase-based bioassay. LPS-stimulated thioglycollate-elicited macrophages activated endogenous latent TGF-beta, whereas non-LPS-stimulated thioglycollate-elicited and resident macrophages generated undetectable levels of TGF-beta. Latent TGF-beta activation required plasmin and urokinase (uPA), uPA binding to the uPA receptor, interaction with the cation-independent mannose 6-phosphate/insulin-like growth factor type II receptor, tissue type II transglutaminase, and LTBP. A time-course analysis of latent TGF-beta activation revealed that maximal TGF-beta was generated after 24 h (25 +/- 5 pg/ml). TGF-beta formed within the initial 24 h modulated the plasminogen activator system by down-regulating uPA, suggesting that TGF-beta temporally modulated its own formation by regulating cell-associated uPA

This article discusses the diagnosis and management of pigmented lesions of the hand, especially the nail bed

The diagnosis of malignant melanoma is based on clinical grounds and a properly performed biopsy, preferably excision, so that the type of melanoma and the thickness can be assessed by methods described by Clark and Breslow. These facilitate clinical and pathologic staging. Excisions with conservative margins for thin lesions (less than 1.0 mm in thickness) and more extensive margins for thicker lesions are appropriate. The issue of elective lymph node dissection is controversial. Most authors agree it is not indicated for lesions less than 1.0 mm thick and may offer little advantage for lesions greater than 4.0 mm thick. Several retrospective studies show a survival advantage in patients with 'intermediate' thickness melanomas who may have occult nodal metastases. However, there are prospective randomized clinical trials supporting the concept that positive lymph nodes are a manifestations of systemic disease, and survival is equivalent in patients who have subsequent therapeutic lymph node dissections. A procedure using intraoperative lymphatic mapping and selective lymphadenectomy may identify those patients who are likely to benefit from lymphadenectomy