Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025202 (melanoma)
 69,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many tumors contain elevated levels of plasminogen activator and thus produce elevated levels of the protease plasmin in the milieu of the tumor. We have hypothesized, therefore, that it should be possible to prepare peptidyl prodrug derivatives of anticancer drugs that would be locally activated by tumor-associated plasmin. As an initial test of this hypothesis, we synthesized the peptidyl prodrugs of the anticancer drugs (alpha S, 5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (acivicin, AT-125) and N,N-bis(2-chloroethyl)-p-phenylenediamine (phenylenediamine mustard) by mixed anhydride coupling of the parent drug with the protected tripeptide, Boc-D-Val-Leu-Lys(Boc)-OH, followed by deprotection with trifluoroacetic acid. The prodrugs showed an increased selective in vitro cytotoxicity for Rous sarcoma virus transformed chicken embryo fibroblasts (which produce elevated levels of plasminogen activator) compared to nontransformed fibroblasts (which produce low levels of plasminogen activator). In the presence of the plasmin inhibitor, p-nitrophenyl p'-guanidinobenzoate at 2 micrograms/mL, the selectivity of the phenylenediamine mustard prodrug was reduced, but there was no effect on the cytotoxicity of the free drug. Furthermore, the prodrug analogue D-valylleucyl-D-lysylphenylenediamine mustard (in which L-Lys has been replaced by D-Lys) was inactive. Finally, the prodrug derivative of acivicin did not display selective toxicity for transformed cells when the cells were cultured in plasminogen-free medium. These results suggest that plasmin hydrolysis is necessary for the activation of the prodrugs. The prodrugs were tested in vivo for antitumor activity. The prodrug of acivicin, like acivicin itself, was inactive against the B16 melanoma, a murine tumor that produces high levels of plasminogen activator. This prodrug was active against the M5076 carcinoma, a tumor that displays only moderate levels of plasminogen activator; however, despite the fact that the prodrug was 2- to 3-fold less toxic on a molar basis than acivicin, there was no evidence of an increased therapeutic index. The prodrug of phenylenediamine mustard was also slightly less toxic than the parent drug, but again there was no evidence for an improved therapeutic index against the B16 tumor.
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PMID:Plasmin-activated prodrugs for cancer chemotherapy. 1. Synthesis and biological activity of peptidylacivicin and peptidylphenylenediamine mustard. 622 Oct 99

alpha-Melanocyte-stimulating hormone (alpha-melanotropin; alpha-MSH) is a linear tridecapeptide (Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) that reversibly darkens amphibian skins by stimulating melanomsome (pigment granule) dispersion within melanophores. By using a number of in vitro melanocyte assays, we have examined the conformational requirements for alpha-MSH activity. Synthesis of [half-Cys4,half-Cys10]-alpha-MSH, a cyclic, conformationally restricted, "isosteric" analogue of alpha-MSH, provided a melanotropin with a potency greater than 10,000 times that of the native hormone in stimulating frog (Rana pipiens) skin darkening. The cyclic analogue also showed substantially prolonged activity relative to the native hormone. [half-Cys4,half-Cys10]-alpha-MSH was approximately 30 times more potent than alpha-MSH in stimulating lizard (Anolis carolinensis) skin melanophores in vitro. By using a cell-free Cloudman S-91 mouse melanoma plasma membrane preparation, we found the cyclic analogue to be approximately 3 times as potent as the native hormone in stimulating adenylate cyclase activity. These results provide insight into the conformational requirements for biological activity of alpha-MSH, and the comparative conformational requirements of alpha-MSH at a number of pigment cell receptors.
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PMID:[half-Cys4,half-Cys10]-alpha-Melanocyte-stimulating hormone: a cyclic alpha-melanotropin exhibiting superagonist biological activity. 628 85

We have synthesized peptidyl prodrugs of doxorubicin (Dox) designed to be selective substrates of plasmin. Such prodrugs might be locally activated by the elevated levels of plasmin produced near many solid tumors under the action of tumor-associated plasminogen activators. One such prodrug, 3'-(D-Val-Leu-Lys)-Dox, was obtained via a mixed-anhydride coupling with isobutyl chloroformate between the protected peptide Fmoc-D-Val-Leu-N epsilon-Fmoc-Lys-OH and doxorubicin, followed by removal of the Fmoc groups with anhydrous ammonia. Compared to doxorubicin, the prodrug showed about a 7-fold improved selective cytotoxicity against chicken embryo fibroblasts transformed with the Rous sarcoma virus (which produce high levels of plasminogen activator) compared to normal cells (which produce low levels of plasminogen activator). However, the prodrug was a very poor plasmin substrate, and although in vivo tests against the murine B16 melanoma showed that the prodrug was active, the maximum T/C obtained was less than that achieved by doxorubicin even at 25 times the molar concentration of prodrug. Qualitatively similar results were obtained for a far more hydrophobic prodrug, 3'-(Boc-Val-Leu-Lys)-Dox. These results demonstrate that peptidyl prodrugs of doxorubicin designed as plasmin substrates are more selective anticancer agents in vitro than doxorubicin itself but that the bulky anthracycline moiety probably prevents efficient plasmin-catalyzed conversion to the active parent drug, so that, in their present form, these drugs are not potent enough to allow a determination as to whether or not they are more selective in vivo.
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PMID:Plasmin-activated prodrugs for cancer chemotherapy. 2. Synthesis and biological activity of peptidyl derivatives of doxorubicin. 630 53

The intraperitoneal (i.p.) injection of tuftsin, Thr-Lys-Pro-Arg, into C57BL/6 mice that were injected with B16/5B melanoma cells, resulted in a considerable suppression and elimination of solid tumor growth. While 100% of control animals exhibited tumor growth, 38% of the treated animals failed to show tumor formation for the duration of the experiment, 60-80 days. The octapeptide, tuftsinyltuftsin, was effective at 3 ng per mouse as was a dose of 2 and 20 micrograms per mouse. In each case there was a significant number of mice free of tumors. The octapeptide was also quite effective against L1210 cells resulting in the survival of 35-40% of the treated animals. The lethal effect of increased superoxide, O X 2, production by tuftsin treatment may explain the antineoplastic effect of the tetrapeptide. This may result not only from higher concentrations of O X 2 but also from the potentially lethal effects of H2O2 and OH X radical, both of which are products of O X 2 metabolism.
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PMID:The antineoplastic effects of tuftsin and tuftsinyltuftsin on B16/5B melanoma and L1210 cells. 632 37

Previous studies have shown that degradation of the acute phase reactant serum amyloid A (SAA) is mediated by enzymes on the plasma membrane of lymphocytes and monocytes. The responsible enzymes had properties of neutral elastases. The present investigations were conducted to explore whether human NK cells enriched by Percoll gradient centrifugation have similar activity and if so, whether the same or different enzyme classes are responsible for proteolysis as well as for tumor cell lysis. Accordingly, human NK cells were enriched on discontinuous Percoll gradients after which the cells were incubated either with SAA or with [3H] proline-labeled melanoma cells at various effector to target cell ratios. When SAA degradation was followed by SDS-polyacrylamide gel electrophoresis, NK fractions proved to be as effective in digesting the protein as unfractionated mononuclear leukocytes. To characterize the enzymes that may be involved in cytotoxicity on the one hand, and SAA degradation on the other, the NK fractions were treated with the following inhibitors: diisopropylfluorophosphate (DFP), soybean trypsin inhibitor, N-p-tosyl-L-lysine chloromethylketone (TLCK), the elastase inhibitors elastatinal, Ac-Ala-Ala-Pro-Val-CH2Cl, Meo-Suc-Ala-Ala-Pro-Val-CH2Cl, and an inhibitor of aryl sulfatase, Na2SO4. Preincubation of the cells with DFP or elastase inhibitors abolished their ability to hydrolyze SAA but did not affect their ability to kill tumor cells. On the other hand TLCK, a potent inhibitor of cytotoxicity, did not bring about any reduction in the proteolysis of SAA. DFP and Na2SO4 diminished cytotoxicity partially. Elimination of NK cells by sorting after incubation of lymphocytes with the monoclonal antisera Leu-7 and Leu-11 abolished cytotoxicity as well as proteolysis. The observations are compatible with the concept that NK cells carry several enzymes with different substrate specificities that may be involved in disparate cellular functions.
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PMID:Different enzyme classes associated with human natural killer cells may mediate disparate functions. 636 42

Different procedures for fixation and processing were evaluated in order to examine the antigenic profile of melanocytes and other epidermal cells for immunoelectron microscopy. For this purpose the monoclonal antibodies anti-HLA-A, B, C, anti-HLA-DR, anti-T6, and the melanoma-associated monoclonal antibody NKI /C-3 were used as markers. Fixation with periodate-lysine-paraformaldehyde yielded better antigenic and ultrastructural preservation than 3% paraformaldehyde or picric acid-paraformaldehyde did. Skin was further processed by five different methods: (a) 15-micron frozen sections; (b) 75-micron agar-embedded, tissue chopper sections; (c) 15-micron polyethylene glycol-embedded sections; (d) epidermal cells in suspension; and (e) epoxy sections (postembedding staining) were prepared for the immunoperoxidase procedure. Antigenicity was best preserved in the cell suspension method and somewhat less, but with a similar staining distribution, with the first three methods. Staining with the polyethylene glycol-embedded sections was only achieved if they were left free-floating in buffer; no staining was observed when the sections were mounted on glass slides and left to dry overnight at 37 degrees C. Epidermal cells remained unreactive in the postembedding method, even after etching. Ultrastructural preservation of the agar-embedded sections and the cells in suspension was superior to the other preembedding methods. Melanocytes mostly showed moderate staining for HLA-A, B, C and slight staining for the antigen that is recognized by NKI /C-3. The latter was further demonstrated on Langerhans cells and indeterminate cells which also expressed HLA-A, B, C, T6, and HLA-DR antigens.
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PMID:Methods in laboratory investigation. Immunoelectron microscopic methods for demonstration of antigens on normal human melanocytes and other epidermal cells. 642 21

The kinetics of the activation of plasminogen by tissue-type plasminogen activator were studied in the presence and the absence of CNBr-digested fibrinogen as a soluble cofactor. Michaelis-Menten kinetics applied and the kinetic parameters obtained were very similar to those previously reported for the activation in the presence of solid phase fibrin (Hoylaerts, M., Rijken, D. C., Lijnen, H. R., and Collen, D. (1982) J. Biol. Chem. 257, 2912-2919). The affinity of the enzyme for plasminogen dramatically increases in the presence of the soluble cofactor while the catalytic rate constant does not change significantly (KM drops from 83 to 0.18 microM and kcat increases from 0.07 to 0.28 s-1 for tissue-type plasminogen activator of melanoma origin). Fragments containing the lysine-binding sites of plasminogen compete with plasminogen for interaction with CNBr-digested fibrinogen. The dissociation constant of this interaction was found to be 4.5 microM for the high affinity lysine-binding site. No difference was found in the kinetic parameters for the activation of plasminogen by either tissue-type plasminogen activator of melanoma origin or by glycosylated forms of tissue-type plasminogen activator obtained by recombinant DNA technology. The present findings obtained in a homogenous liquid milieu support the previously proposed mechanism of the activation of plasminogen by tissue-type plasminogen activator in the presence of fibrin. This mechanism involves binding of both tissue-type plasminogen activator and plasminogen to fibrin.
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PMID:Kinetics of the activation of plasminogen by natural and recombinant tissue-type plasminogen activator. 653 96

Tissue plasminogen activator (t-PA) in plasma was separated from inhibitors by adsorption on lysine-Sepharose. It was then determined indirectly by measuring the plasmin generated from plasminogen with poly-lysine as stimulator, in a chromogenic, parabolic rate assay. The reaction proceeded with tissue plasminogen activator and plasmin(ogen) adsorbed on the gel, and followed the kinetics described for similar parabolic rate assays in soluble systems. The assay was standardized against melanoma plasminogen activator (m-PA) and had the sensitivity range of 0.001-0.020 IU (4-80 pg). Anti-m-PA IgG quenched the activity generated in plasma on venous occlusion and part of the activity in pre-occlusion plasma. The method was sensitive to purified urokinase. The basic plasma values in resting normal individuals were: mean 0.08, range 0.01-0.26 X 10(3) IU/l (n = 19), and after 20 min of venous occlusion: mean 2.48, range 0.24-4.34 X 10(3) IU/l (n = 10). The assay correlates well with a fibrin plate method, r = 0.96.
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PMID:A sensitive assay for tissue plasminogen activator activity in plasma, using adsorption on lysine-sepharose. 654 74

An acid-stable transforming growth factor (TGF) that interacts with epidermal growth factor (EGF) receptors and is structurally related to EGF was isolated from serum-free culture fluids of Snyder-Theilen feline sarcoma virus-transformed rat embryo (FeSV-Fre) cells. Purification of this EGF-like TGF (eTGF) was achieved by molecular filtration chromatography and successive reverse-phase high pressure liquid chromatography steps on octadecyl support eluted with acetonitrile and 1-propanol gradients, respectively. Rat eTGF consists of a 7.4-kD single polypeptide chain that co-migrates with biological activity in dodecyl sulfate-polyacrylamide electrophoresis gels. Like preparations of a related TGF from human melanoma cells (Marquardt, H., and Todaro, G.J. (1982) J. Biol. Chem. 257, 5220-5225), but unlike EGF from rat, human, or mouse, rat eTGF has phenylalanine and lacks methionine. However, the sequence of the first 30 amino acid residues in rat eTGF is H2N-Val-Val-Ser-His-Phe-Asn-Lys-Cys-Pro-Asp-Ser-His-Thr-Gln-Tyr-Cys-Phe-His-Gly - Thr-(x)-Arg-Phe-Leu-Val-Gln-Glu-Glu-(Lys)-(Lys)-, which is significantly (20% and 28%) homologous to the NH2-terminal region of mouse EGF and human EGF, respectively. In addition to eTGF, molecular filtration chromatography of acid-soluble extracts from medium conditioned by FeSV-Fre cells resolved a 14-kD transforming factor(s) apparently devoid of intrinsic mitogenic activity but able to elicit a strong anchorage-independent growth response in the presence of eTGF or EGF. These results show that: 1) a 7.4-kDa TGF structurally and functionally related to EGF has been isolated from FeSV-Fre cells and 2) the full anchorage-independent growth-promoting activity of medium conditioned by FeSV-Fre cells is due to the coordinate action of at least two types of factors, the 7.4-kDa eTGF and a second 14-kDa transforming factor(s).
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PMID:Epidermal growth factor-like transforming growth factor. I. Isolation, chemical characterization, and potentiation by other transforming factors from feline sarcoma virus-transformed rat cells. 660 68

Ac-[Nle4, D-Phe7]-alpha-MSH4-11-NH2 an octapeptide, is a melanotropin analogue (Ac-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-NH2), which is a superpotent agonist of frog and lizard skin melanocytes and mouse S 91 (Cloudman) melanoma cells. This melanotropin possesses ultraprolonged activity on melanocytes, both in vitro and in vivo, and the peptide is resistant to inactivation by serum enzymes. The tritium-labeled congener was prepared by direct incorporation of [3H]-labeled norleucine into the peptide. The melanotropic activity of the labeled peptide is identical to the unlabeled analogue. This labeled peptide should be useful for studies on the localization and characterization of melanotropin receptors.
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PMID:Synthesis of tritium labeled Ac-[Nle4, D-Phe7]-alpha-MSH4-11-NH2: a superpotent melanotropin with prolonged biological activity. 660 41


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