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PubMed2001

Effect of three flavonoids, 5,7,3',4'-tetrahydroxy-3-methoxy flavone, luteolin, and quercetin, on the stimulus-induced superoxide generation and tyrosyl phosphorylation of proteins in human neutrophil.

The effect of three flavonoids, 5,7,3',4'-tetrahydoxy-3-methoxy flavone (THMF), luteolin, and quercetin, on the stimulus-induced superoxide generation and tyrosyl phosphorylation of proteins in human neutrophils were investigated. When the cells were preincubated with these flavonoids, the superoxide generation induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) was significantly suppressed, showing a dependence on amounts of the flavonoid. The suppressing effect of the flavonoid was THMF > luteolin > quercetin. These flavonoids also suppressed the superoxide generation induced by phorbol 12-myristate 13-acetate. In this case also, THMF was more effective than luteolin and quercetin. On the other hand, the superoxide generation induced by arachidonic acid was markedly suppressed by quercetin. The suppressing effect was quercetin >> THMF > luteolin. THMF, luteolin, and quercetin significantly suppressed tyrosyl phosphorylation of 80.1-, 58.0-, and 45.0-kDa proteins in fMLP-treated human neutrophils. The suppression depended on the concentration of the flavonoids, and the inhibition of tyrosyl phosphorylation was in parallel to that of the fMLP-induced superoxide generation, respectively. While luteolin and quercetin showed a weak hemolytic activity at 2.5 mM, THMF showed almost no hemolytic activity even at 5 mM, suggesting an advantage of THMF for its clinical use.

Arachidonic Acid↗
PubMed1997

Flavone acetic acid stimulates nitric oxide and peroxynitrite production in subcutaneous mouse tumors.

Flavone acetic acid (FAA) has powerful anti-tumor activity against many types of solid murine tumors, but its biochemical mechanism of action is not understood. The present study examined the role of tumor vasculature and nitric oxide in mediating the anti-tumor effects of FAA. Athymic nude mice bearing subcutaneous RJ2-14 tumors were treated with a single dose of FAA, 200 mg/kg i.p., and euthanized at various times. Apoptosis within tumors was apparent during the first six hours of FAA treatment. We found that Type III, endothelial nitric oxide synthase (NOS) activity was significantly increased in tumors, but not in other tissues, as early as two hours after FAA dosing. FAA also stimulated the formation of the toxic peroxynitrite radical in tumors within two hours of treatment as assessed by immunostaining for nitrotyrosine. Staining was observed in dilated tumor vessels and surrounding tumor cells and correlated with the presence of apoptosis. Tumor endothelium may therefore be a critical target for FAA activity via stimulation of the nitric oxide pathway.

Adenocarcinoma↗
PubMed1998

Detection of benzodiazepine receptor ligands in small libraries of flavone derivatives synthesized by solution phase combinatorial chemistry.

Solution phase combinatorial synthesis of flavone derivatives and evaluation of their affinity for the central benzodiazepine receptors is described. The libraries preparation is simple and provides a convenient method for rapid compound generation and screening. Thirty one new compounds were obtained of which the most promising, as high affinity benzodiazepine receptor ligands, were 6-bromo-3'-fluoroflavone; 6,3'-dichloroflavone; 6-bromo-3'-chloroflavone and 6-chloro-3'-bromoflavone.

Animals↗
PubMed1994

Induction of multiple cytokine gene expression and IRF-1 mRNA by flavone acetic acid in a murine macrophage cell line.

Flavone-8-acetic (FAA) acid is a potential chemotherapeutic agent that has demonstrated strong immunomodulatory activity in murine model systems. The immunomodulatory activity of this drug in murine systems has been linked to its ability to rapidly induce cytokine gene expression in vivo and in mouse splenocytes ex vivo. We have now developed a tissue culture model for studying the molecular basis of induction of cytokine expression by FAA. Using the mouse macrophage cell line, ANA-1, we can demonstrate the direct induction of interferon beta (IFN beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF alpha), and interferon response factor-1 (IRF-1) mRNA expression following treatment with FAA. Furthermore, the induction of the IFN beta mRNA can occur in the absence of new protein synthesis. Nuclear run-on experiments indicate that at least part of the induction of IFN beta, IL-6, and TNF alpha mRNA occurs at the transcriptional level while the increase in IRF-1 mRNA appears largely post-transcriptional or due to the production of IFN beta protein. Additionally, experiments using agents that interfere with second messengers demonstrate that activation of the protein kinase C pathway is possibly involved in FAA gene induction. The use of this tissue culture model system should lead to a more complete understanding of the mechanisms involved in FAA-induced gene expression and help determine why this drug is inactive on human cells.

Adjuvants, Immunologic↗
PubMed1990

Combination of flavone acetic acid (FAA) with adriamycin, cis-platinum and difluoromethylornithine (DFMO) in vitro against human colon cancer cells.

Unresectable solid tumors in the metastatic stage are quite resistant to current chemotherapy and radiation therapy regimens. Flavone acetic acid (FAA) is a novel antitumor agent which appears to work through a different mechanism than the conventional chemotherapeutic agents. In preclinical studies it has shown effectiveness against a variety of transplantable murine and human tumors and appears to be solid tumor selective. It also has non-overlapping toxicities as compared to conventional agents. We therefore investigated FAA in vitro against human colon cancer cells and explored whether its effectiveness could be enhanced in combination with other agents such as adriamycin (ADR), cis-platinum (CP) and difluoromethylornithine (DFMO)--an inhibitor of polyamine biosynthesis. Addition of FAA for 24 hours in liquid media produced dose dependent growth inhibition. Using soft agar colony assay, growth was inhibited by 58% by 3mM FAA and only 1.4% by 0.375mM FAA. The combination of FAA and cis-platinum produced synergism at the lower doses tested. The combination of FAA and adriamycin produced antagonism at all doses tested and the combination of FAA with DFMO did not produce results significantly different from DFMO alone. We conclude that enhancement of FAA activity can be achieved in combination with conventional antitumor agents, but may be drug and dose specific.

Antineoplastic Agents↗
PubMed1990

Phase II trials with flavone acetic acid (NCS. 347512, LM975) in patients with advanced carcinoma of the breast, colon, head and neck and melanoma.

Phase II trials of flavone acetic acid have been performed in a total of 87 patients including 17 with advanced breast cancer, 23 with advanced colorectal cancer, 25 with advanced malignant melanoma and 22 with advanced head and neck cancer. Patients with colorectal cancer and melanoma had received no prior chemotherapy; in breast and head and neck cancer patients prior chemotherapy had been given with a median of 5 and 2 drugs respectively. The schedule used was a once-weekly regime, with a dose of 4.8 gms/m2 given as a 1 hour infusion, together with alkalinization (with i.v. sodium bicarbonate) given before and after FAA. Reassessment was performed after 6 weekly doses, although in 23 patients fewer than 6 doses were given, because of early disease progression in 15, and undue toxicity in 5. An additional 3 patients died within 72 hours of having received FAA and, although the precise cause of death in each case was not established, FAA toxicity could not be excluded. Treatment was generally manageable, the major manifestations of toxicity comprising uncomfortable warmth and flushes, nausea, diarrhoea, and visual complaints. Hypotension was also documented in 8 patients. No objective responses were seen in any of the patient sub-groups, although disease-stabilization was seen in 3 patients with breast cancer, 1 patient with advanced colorectal cancer, 2 patients with advanced melanoma and 4 patients with head and neck cancer. Further Phase II studies, using a higher dose of 8.6 gm/m2 over 6 hours once weekly, are currently in progress in Europe.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

The activity of flavone acetic acid (NSC 347512) on human colon cancer cells in vitro.

Flavone acetic acid (FAA) was incubated for 1 to 48 hr with 3 established human colon cancer cell lines endowed with distinct degrees of phenotypic properties. All 3 lines responded to FAA in almost identical fashion; when incubated with the drug for only 1 hr, an initial decrease in survival was observed for concentrations of 250 micrograms/ml but no further increments in cytotoxicity were elicited when the concentration of FAA was augmented. Increasing the length of treatment yielded relatively modest increments (about 1 log) in cell killing only after an interval of 48 hr and only at the highest concentration (1000 micrograms/ml). Because of these relatively poor cytotoxic effects and because the therapeutic range of FAA is so narrow, we conclude that this agent will not be a valuable contribution to the antitumor arsenal, at least for colon cancer.

Antineoplastic Agents↗
PubMed1986

Activity of flavone acetic acid (NSC-347512) against solid tumors of mice.

Flavone acetic acid (FAA) is a new antitumor agent that has recently entered Phase I clinical trials. In preclinical studies, we have found that FAA was broadly active against a variety of transplantable solid tumors of mice (colon #51, #07, #10, #26; pancreatic ductal adenocarcinomas #02 and #03; mammary adenocarcinoma #16/C/Adr; M5076 reticulum cell sarcoma and Glasgow's osteosarcoma). FAA was curative for colon adenocarcinoma #10 and pancreatic ductal adenocarcinoma #03. Thus, for the first time an agent has been identified with very broad, perhaps nearly universal solid tumor activity. FAA was also found to be orally active and stable in solution at 37 degrees C for 48 h. FAA was selectively cytotoxic in vitro for solid tumors over leukemias L1210 and P388 (in a soft-agar colony formation assay), thus correlating cellular selectivity in vitro with in vivo antitumor activity. The finding that FAA was active in vitro, established that the agent did not need metabolism (activation) outside the tumor cell. The main drawback of FAA was an unusual 'threshold' behavior in which only a narrow range of doses were active and splitting the dose markedly decreased activity.

Adenocarcinoma↗
PubMed1989

Pharmacodynamics and causes of dose-dependent pharmacokinetics of flavone-8-acetic acid (LM-975; NSC-347512) in mice.

Flavone acetic acid (FAA) is a novel antitumor agent with broad solid-tumor activity. However, this drug has shown a steep dose-response curve in preclinical trials, with a narrow sublethal window of efficacy. To investigate this threshold behavior, we studied various aspects of FAA pharmacology in mice after i.v. administration. Mice bearing advanced-stage s.c. colon 38 adenocarcinoma were treated at four dose levels (39, 65, 108 and 180 mg/kg), and only the highest dose produced significant antitumor activity, showing a steep dose-response curve. Using an HPLC assay, FAA pharmacokinetics in both plasma and tumors were found to be dose-dependent. As the dose increased, there was a decrease in both total body clearance and volume of distribution at steady state. The increase in tumor area under the curve (AUC) was more pronounced than the corresponding increase in plasma AUC, showing a better tumor exposure to FAA at high doses. The distribution of FAA in normal tissues showed a short-term retention in the liver and kidneys; low concentrations were observed in the heart, spleen, and brain, with some retention in the latter. The highest FAA concentrations were found in the gastrointestinal (GI) tract, mainly in the duodenum, suggesting an important biliary excretion of the drug. Various possible causes of FAA nonlinear pharmacokinetics were investigated. Serum protein binding was high (79%) and remained constant up to 100 micrograms/ml, but decreased thereafter at higher FAA concentrations, e.g., 76% at 500 micrograms/ml and 64% at 1,000 micrograms/ml. Urinary and biliary clearances were dose-dependent and decreased 5- and 9-fold, from the 39- to the 180-mg/kg dose levels, respectively. A direct assessment of FAA enterohepatic circulation using intercannulated mice showed that 27% of the plasma AUC was accounted for by enterohepatic circulation. FAA acyl glucuronide was identified as the major metabolite in mice and was found to contribute to the nonlinear pharmacokinetics due to its facile hydrolysis under physiological conditions, regenerating FAA. In conclusion, the steep FAA dose-response curve was found to be caused by dose-dependent pharmacokinetics in mice. The nonlinear pharmacokinetics of this drug was attributed to a dose-dependent decrease in both urinary and biliary clearances, concentration-dependent serum protein binding, enterohepatic circulation, and the instability of FAA acyl glucuronide under physiological conditions forming a futile cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗
PubMed1988

Dose-dependent pharmacokinetics of flavone acetic acid in mice.

The pharmacokinetics of the novel anticancer agent, flavone acetic acid (FAA) were investigated in Balb-c mice treated with i.v. doses of 100 mg/kg or 300 mg/kg, using an HPLC assay. The kinetics of disappearance from plasma was monoexponential and dose-dependent. After 100 mg/kg, the plasma peak level was 250 +/- 11 micrograms/ml, t1/2 was 0.5 h, and AUC was 309 micrograms/ml per h. After 300 mg/kg, the plasma peak level was 710 +/- 57 micrograms/ml, t1/2 was 2.1 h, and the area under the curve (AUC) 1771 micrograms/ml h. Mouse plasma protein binding of FAA was about 70%. As is the case with plasma, in all tissues analyzed, the FAA-AUC values were disproportinately greater after 300 mg/kg than after 100 mg/kg. The highest drug concentrations were found in the liver and small intestine; concentrations were intermediate in lung, heart, and spleen, and lowest in brain. Less than 5% of the FAA dose was eliminated as unchanged drug in the stool. Total excretion of FAA as unchanged drug in the urine collected up to 96 h after drug treatment corresponded to 75% and 60% of the i.v. doses of 100 and 300 mg/kg, respectively. A minor fraction of FAA dose, corresponding to 1% and 6% of the two doses, was eliminated in the urine as a FAA glucuronide or sulfate.

Animals↗
PubMed1988

Flavone acetic acid: a nonlinear pharmacokinetic model.

Flavone acetic acid pharmacokinetics were studied in 31 patients in a phase I clinical trial. The drug was given by i.v. infusions over 1, 1.5, 3, and 6 h at doses ranging from 0.5 to 6.4 g/m2. The pharmacokinetic parameters were determined according to a nonlinear model including Michaelis-Menten-type kinetics. The mean elimination half-life is 4.8 h and the mean volume of distribution of the central compartment, 7.61. Our model predicted a maximal tolerated dose (MTD) of 11.1 g/m2 on the basis of the "therapeutic window" concept, very close to the clinically observed MTD of 10 g/m2. This model is also operational when different protocols of inoculation are considered, such as a divided-dose schedule vs a unique infusion, and indicates that, at the MTD, injections should be made every 72 h to avoid drug accumulation.

Algorithms↗
PubMed1989

Influence of site on the chemosensitivity of transplantable murine colon tumours to flavone acetic acid (LM975, NSC 347512).

A number of experimental studies have demonstrated significant responses of s.c. solid tumours to flavone acetic acid (FAA). Clinical studies to date have been disappointing, with no objective responses being seen. The present study demonstrated that the tumour site is important for the anti-tumour action of FAA against two transplantable adenocarcinoma lines (MAC) in NMRI mice. Responses were achievable only when the tumours were implanted s.c. Ascitic or systemic tumours did not respond to FAA. Experimentally achievable plasma levels of FAA were not sufficient to induce significant cell kills in either MAC 15A or MAC 26 cell lines in vitro. A poor correlation exists between in vitro and in vivo responses, as the clonogenic assay could not predict the response of the solid MAC tumours grown s.c. The in vitro data indicated that the length of exposure to FAA was important, with long exposure times being necessary for cytotoxicity to develop, in these tumour cell lines. These studies imply that more than one mechanism is involved, and it is likely that the activity of FAA against s.c. tumours relies at least in part on a specific biological feature of tumours in this site. However, it may still be possible to achieve systemic tumour cell kill in vivo by increasing drug-exposure times.

Adenocarcinoma↗
PubMed1987

Flavone acetic acid (LM 975, NSC 347512). A novel antitumor agent.

Flavone acetic acid (FAA) is a synthetic flavonoid compound which has recently begun clinical trials as an antitumor agent based on its striking activity in solid tumor model systems. The pharmacologic behavior of FAA in animals appears to be predictive of both its cytotoxic efficacy and its toxicity to normal tissues (principally the central nervous system and gastrointestinal tract). The design and conduct of phase I studies in man are based upon these principles, with the goal of maximizing their safety and efficacy.

Animals↗
PubMed1989

Flavone 8-acetic acid: our current understanding of its mechanism of action in solid tumours.

Flavone 8-acetic acid (FAA) represents a novel chemical structure undergoing clinical trials as an anticancer drug. Its unusual properties tend to distinguish it from a conventional cytotoxic compound, particularly in the response of solid murine tumours; as a consequence, novel mechanisms of action are currently under investigation. In this review we summarised these mechanisms into one of the three categories (a) direct cytotoxicity, (b) biologic response modifier and (c) pharmacologic effector and considered the evidence for and against each. FAA is cytotoxic to tumour cells in vitro, but only at high concentrations and after long exposures. In vivo it is considerably more cytotoxic to the same cells, and it is unlikely that direct cytotoxicity alone can account for this difference. FAA stimulates NK cell activity, induces interferon alpha and synergises with interleukin 2 in the treatment of murine renal cancer. However, a definite link between immunomodulation and antitumour activity has still to be confirmed. Perhaps FAA's most unusual property is its ability to reduce tumour blood flow dramatically, which may provide the appropriate conditions for reactive chemistry to occur. Finally, a combination of the above mechanisms probably work together in producing the drug's unique spectrum of antitumour activity.

Adjuvants, Immunologic↗
PubMed1989

Flavone acetic acid (LM-975; NSC-347512) activation to cytotoxic species in vivo and in vitro.

Flavone acetic acid (FAA; LM 975; NSC 347512) is a new anticancer agent with unprecedented, broad antitumor activity in murine models. Although FAA is very effective in vivo against solid tumors, including colon 38 adenocarcinoma, it was not cytotoxic in vitro against colon 38 cells and human colon adenocarcinoma cells HCT116 at pharmacologically achievable concentrations and exposure times. For example, a concentration of 300 micrograms/ml for a 10-day exposure time was required to obtain less than 1 log cell kill. After the administration of an effective FAA dose (180 mg/kg, i.v.) to mice, plasma cytotoxicity against HCT116 cells attained a 2 log cell kill between 0.5 and 2 h, which decreased to 1 log cell kill at 4 h. No cytotoxicity was observed 6, 12 or 21 h after drug administration. The controls used comprised mouse plasma containing FAA concentrations similar to those assayed in the above plasma samples from in-vivo-dosed mice. These spiked plasma were not cytotoxic, indicating that other cytotoxic species, formed in vivo, were responsible for the increased cytotoxicity. Mouse hepatocytes co-cultured with HCT116 cells increased FAA cytotoxicity to 1 log cell kill at 30-100 micrograms/ml. The addition of phenobarbital-induced mouse liver supernatant S-9000xg also markedly increased FAA cytotoxicity to a 2 log cell kill at 300 micrograms/ml. We conclude that FAA can be activated both in vivo and in vitro to cytotoxic species that are more active than the parent compound.

Adenocarcinoma↗
PubMed1989

Could interspecies differences in the protein binding of flavone acetic acid contribute to the failure to predict lack of efficacy in patients?

We investigated the differences in plasma protein binding of flavone acetic acid (FAA) in mice and men in an attempt to explain the inter-species differences in response. In vitro data indicate both qualitative and quantitative differences in FAA protein binding: approximately 80% is bound in humans, with two different types of binding site identified; in mice, 70% is bound and only one binding site could be described. Protein binding is dose-dependent in both species. Plasma samples from 20 patients receiving FAA showed that most achieved levels that would be active in mice. We conclude that these differences in protein binding are insufficient to explain totally the observed differences in response.

Animals↗
PubMed1992

Nitric oxide: its production in host-cell-infiltrated EMT6 spheroids and its role in tumour cell killing by flavone-8-acetic acid and 5,6-dimethylxanthenone-4-acetic acid.

Flavone-8-acetic acid (FAA) and its more dose-potent analogue 5,6-dimethylxanthenone-4-acetic acid (5,6-MeXAA), appear to exert their antitumor effects through vascular and other host-mediated mechanisms and are known to induce the synthesis of nitric oxide by murine macrophages. We investigated the role of nitric oxide in the cytotoxic effects of these drugs in host-cell-infiltrated spheroids. EMT6 murine mammary adenocarcinoma cells were grown in culture to produce multicellular spheroids in vitro spheroids), which were then inoculated i.p. into mice. After 6 days the spheroids were removed ex vivo spheroids). Exposure to FAA (890 microM) and 5,6-MeXAA (80 microM) in vitro for 20 h increased nitrite concentrations to 6.7 and 9.7 nmol/spheroid, respectively, as compared with 0.7 nmol/spheroid in the absence of drug. FAA and 5,6-MeXAA did not increase nitrite production in in vitro spheroids in cells obtained by peritoneal lavage. However, mixed cultures of in vitro spheroids and peritoneal cells treated with 5,6-MeXAA produced nitrite (2.4 nmol/spheroid), indicating that interactions between host cells and tumour cells were important for induction. The effects of these drugs on ex vivo spheroids were prevented by co-incubation with NG-monomethyl-L-arginine, indicating that nitrite originated from the oxidation of L-arginine to nitric oxide. Cell sorting of disaggregated spheroids into EMT6 cells and Mac-1-positive macrophage populations indicated that both of these cell populations could be induced to synthesise nitric oxide by subsequent incubation with 5,6-MeXAA. Incubation of ex vivo spheroids with FAA and 5,6-MeXAA decreased the clonogenicity of EMT6 cells, and this effect was wholly (FAA) or partially (5,6-MeXAA) reversed by the presence of NG-monomethylarginine (250 microM). FAA and 5,6-MeXAA may therefore exert some of their cytotoxic effects on tumour cells through the production of nitric oxide.

Adenocarcinoma↗
PubMed1991

Plasma pharmacokinetics of the antitumour agents 5,6-dimethylxanthenone-4-acetic acid, xanthenone-4-acetic acid and flavone-8-acetic acid in mice.

Although the antitumour agent flavone-8-acetic acid (FAA) exhibits remarkable activity against murine solid tumours, its clinical use has a number of pharmacological drawbacks, including low dose potency and dose-dependent pharmacokinetics. Xanthenone-4-acetic acid (XAA) and its 5,6-dimethyl derivative (5,6-MeXAA) were synthesised during a search for better analogues of FAA. The maximal tolerated doses (MTDs) of 5,6-MeXAA, XAA and FAA in BDF1 mice were 99, 1,090 and 1,300 mumol/kg, respectively. At the MTD, 5,6-MeXAA displayed the following pharmacokinetic properties: maximal plasma concentration, 600 microM; mean residence time, 4.9 h; AUC, 2,400 mumol h 1-1; and volume of steady-state distribution, 0.2 l/kg. All compounds displayed nonlinear elimination kinetics at the MTD, but when the logarithm of the AUC was plotted against that of the delivered dose, the slope of the regression line for 5,6-MeXAA was found to be 1.2 as opposed to 1.4 for XAA and 1.98 for FAA. 5,6-MeXAA thus showed only a slight deviation from dose-independent kinetics. 5,6-MeXAA bound to plasma proteins in a manner similar to that exhibited by FAA, although the plasma concentration of free drug was lower for the former than for the latter. As a consequence, the calculated maximal free drug concentration for 5,6-MeXAA in plasma was 23 times lower than that for FAA.

Animals↗