Synthesis,photophysical properties and biological evaluation of β-alkylaminoporphyrin for photodynamic therapy

A series of β-alkylaminoporphyrins conjugated with different amines at β position (D1–D3) or with electron-donating and electron-withdrawing substituents at phenyl position (D4–D6) were synthesized. Their photophysical and photochemical properties, intracellular localization, photocytotoxicities in vitro and vivo were also investigated. All target compounds exhibited no cytotoxicities in the dark and excellent photocytotoxicities against HeLa cells. Among them, D6 showed the highest phototoxicity and the lowest dark toxicity, which was more phototoxic than Hematoporphyrin monomethyl ether (HMME). In addition, D6 exhibited best photodynamic antitumor efficacy on BALB/c nude mice bearing HeLa tumor. Therefore, D6 is a powerful and promising antitumor photosensitizer for photodynamic therapy.     

Significant antitumor effect of a synthetic lipid A analogue,DT-5461, on murine syngeneic tumor models

Summary The antitumor effect of a synthetic lipid A analogue, DT-5461, was investigated using syngeneic tumor models in mice. Intravenous injection of DT-5461 into mice transplanted with solid tumors of MethA fibrosarcoma, MH134 hepatoma, MM46 mammary carcinoma, Lewis lung carcinoma (3LL), and colon adenocarcinomas 26 and 38 resulted in significant reductions in the weight of all tumors except Colon 26, with marked hemorrhagic necrosis of tumor tissues. Efficacy was almost equal to that of anEscherichia coli-type synthetic lipid A (compound 506), and also to those of some chemotherapeutics including Adriamycin, mitomycin C, fluorouracil and cisplatin. Furthermore, DT-5461 was more effective than other immunotherapeutics, including picibanil (OK-432) and lentinan. However, its antitumor effects were inferior to those of Adriamycin or OK-432 against the malignant ascites caused by intraperitoneal inoculation with MethA or with MH134 cells; life span was not prolonged by either intraperitoneal or intravenous administration. In addition, although DT-5461 showed direct inhibitory effects on the in vitro growth of MethA or MH134, these were much weaker than those of Adriamycin. These findings clearly indicated that DT-5461 with systemic administration is a highly effective antitumor agent on solid tumors, and suggest that the antitumor effect of DT-5461 with potent necrotizing activity might derive from indirect mechanisms related to the activation of host immune systems and not to the weak direct cytotoxicity.     

Bacterial superantigens as anti-tumour agents: induction of tumour cytotoxicity in human lymphocytes by staphylococcal enterotoxin A

Summary Activation of lymphocytes by interleukin-2 (IL-2) induces lymphokine-activated killer (LAK) cells that show promising effects on tumour growth in clinical trials. We examined the effect of the superantigen staphylococcal enterotoxin A (SEA) on anti-tumour activity of freshly prepared human lymphocytes. Picomolar amounts of SEA rapidly induced cytotoxic activity against K562 and Raji cells as well as some natural-killer(NK)-resistant tumour cell lines. Cytotoxic activity was not dependent on target cell expression of either major histocompatibility complex (MHC) class I or II antigens as shown using mutated cell lines. Cell-sorting experiments showed that the activity was expressed by NK (CD5^–CD56⁺) as well as T (CD5⁺) cells, although the former contained the majority of cytotoxic activity. NK cells could not be directly activated by SEA. In contrast, SEA activated purified T cells to the same extent as in bulk cultures. It is suggested that SEA activation of NK cells is secondary to that brought about by lymphokines produced by T cells. Activation of LAK cells with SEA was comparable in magnitude as well as target cell spectrum to that of IL-2. In addition to the LAK-like cytotoxic activity induced by SEA, a superimposed cytotoxicity towards target cells expressing MHC class II antigens coated with SEA was observed. This staphylococcal-enterotoxin-dependent cell-mediated cytotoxicity (SDCC) was exclusively mediated by T cells. It is well established that MHC class II antigens function as receptors for staphylococcal enterotoxins on mammalian cells and that the complex between MHC class II antigen and — SEA apparently functions as a target structure for activated T cells with target cell lysis as a consequence. Activation of T lymphocytes with IL-2 also resulted in the capability to mediate SDCC. Staphylococcal enterotoxins represent a novel way of inducing anti-tumour activity in human lymphocytes, which could be of value in therapeutic applications.     

Denaturation level of DNA-Pt complexes evidenced by Tb3+ fluorescence enhancement and electric dichroism

The Tb³⁺ fluorescence is greatly enhanced, as a result of binding of various platinum coordination complexes to DNA, as compared to native DNA. The largest enhancement is observed for cis-Pt(NH₃)₂Cl₂ but the fluorescence intensity does not however reach the level attained for thermally denatured DNA. Diethylenetriamine-Pt(II) produces very little increase of Tb³⁺ fluorescence. The electric dichroism in the DNA absorption band drastically decreases upon binding of the various Pt compounds investigated except diethylenetriamine-Pt. The results are discussed in terms of the various modes of binding of Pt derivatives to DNA, particularly in relation to the level of denaturation of the double helix.     

A homopolymer of the potent antitumor drug 2′-deoxy-5-fluorouridylate

Poly(5-fluoro-2′-deoxyuridylic acid) was synthesized and its properties were compared with those of poly(dT) and poly(dU). It readily complexed with poly(dA). The 1:1 complex melted at about 20°C lower than poly(dA) · poly(dT). A triple-stranded helix, poly(dA)·2 poly(dF⁵U) was formed only in high salt (2.0 M NaCl).     

The mode of action of cytotoxic and antitumor 1-nitroacridines. I. The 1-nitroacridines do not exert their cytotoxic effects by physicochemical binding with DNA

The mode of action of cytotoxic and antitumor 1-nitroacridines and their isomeric derivatives was studied by comparing their effects in cell-free systems and towards cultured tumor HeLa cells, assuming that the nitroacridines considered exert cytotoxic effects by physicochemical binding with the DNA. All the nitroacridines impaired biosyntheses of DNA, RNA and protein in cultured HeLa cells and a causal relationship between nitroacridine inhibition of macromolecular biosyntheses and lethal effects of the agents appears likely. In cell-free systems, the nitroacridines bound with two independent sites on the DNA, forming complexes with enhanced resistance to DNA strand separation upon melting and inhibited the DNA polymerase reaction by altering activity of template and/or of enzyme. The 1-nitroacridines were poorly effective in cell-free systems and were the most potent inhibitors toward the growth of HeLa cells among the derivatives studied. It is concluded that the primary events responsible for cytotoxic effects of antitumor 1-nitroacridines and of their isomeric derivatives are different. The metabolic activation of 1-nitroacridines to more reactive intermediates which will attach to and alter the structure and/or function of DNA of sensitive cells is suggested.     

Carbon catabolite regulation of rebeccamycin production inSaccharothrix aerocolonigenes

Summary A new antitumor antibiotic named rebeccamycin was isolated from fermentations of an actinomycete,Saccharothrix aerocolonigenes. A defined medium was developed to study the regulation of synthesis of rebeccamycin byS. aerocolonigenes. In glucose medium formation of rebeccamycin was detected only after glucose was depleted. Examination of eleven different carbon sources revealed that carbon catabolite regulation is a major control mechanism for rebeccamycin production.     

Identification of indolepyruvic acid as an intermediate of rebeccamycin biosynthesis

Summary Experimental evidence is presented to demonstrate that indolepyruvic acid is an intermediate in the rebeccamycin biosynthetic pathway. [3-¹⁴C]Indolepyruvic acid was prepared and efficiently incorporated (8%) into rebeccamycin bySaccharothrix aerocolonigenes.     

Golgi apparatus respond to the antitumor sulfonylurea N-(4-methylphenylsulfonyl)-N′-(4-chlorophenyl)urea (LY 181984) in sulfonylurea-susceptible but not in resistant cell lines

Summary Cell lines susceptible or resistant to the active antitumor sulfonylurea [N-(4-methylphenylsulfonyl)-N-(4-chlorophenyl)-urea] (LY 181984) were treated with 100 M sulfonylurea for 1 or 3 h followed by monensin for 1 h. With cell lines where growth was inhibited by the active sulfonylurea, swollen Golgi apparatus cisternae following treatment were fewer and smaller than in untreated cells. Overall the volume of monensin-responsive trans cisternae was reduced by about 50% to 75% in cells lines where the antitumor sulfonylurea was growth inhibitory. The swelling response was unaffected by sulfonylurea in sulfonylurea-unresponsive cells. The antitumor-inactive sulfonylurea [N-(4-methylphenylsulfonyl)-N-(phenyl)urea] (LY 181985) was without effect on cisternal swelling with both susceptible and resistant cell lines. The results suggest a response of the trans Golgi apparatus to the active antitumor sulfonylurea that resulted in reduced acidification of the trans Golgi apparatus cisternae. This response appears to be restricted to susceptible cell lines where growth was inhibited by the active antitumor sulfonylurea but not in resistant cell lines where growth was unaffected by the active antitumor sulfonylurea.     

Analysis of effector T cells against the murine syngeneic tumor MethA in mice orally administered antitumor polysaccharide SPR-901

The growth of MethA tumor was significantly inhibited by oral administration of the -glucan SPR-901 in BALB/c (+/+) mice but not in nude mice. Mice treated orally with SPR-901 exhibited an augmentation of antigen-specific resistance against rechallenge with the tumor cells. The tumor-neutralizing activity of regional lymph node cells from MethA-bearing mice against the tumor was augmented by oral administration of SPR-901. The tumor-neutralizing activity of lymph node cells from SPR-901-treated mice mainly appeared in Lyt2+cells. Furthermore, lymphokine-activated killer activity of these cells was enhanced by administration of SPR-901. The antitumor effect of SPR-901 was abrogated in mice depleted of either L3T4+ or Lyt2+ cells, and in cyclosporin-A-treated mice. These results suggest that Lyt2+ cells are important effector cells in MethA-bearing mice orally adminstered SPR-901 and that functional exertion of both Lyt2+ and L3T4+T cells is necessary for the antitumor effect of orally administered SPR-901 in vivo.