Flavone Acetic Acid Research Articles

In vitro methods for screening agents with an indirect mechanism of antitumour activity: Xanthenone analogues of flavone acetic acid

Xanthenone-4-acetic acid (XAA) resembles flavone acetic acid (FAA) in its effects on solid tumours in mice. The activity of methyl-substituted XAA derivatives in vitro was determined using 18 h 51Cr-release assays, continuous exposure growth inhibition assays and stimulation of tumouricidal activity of cultured murine resident peritoneal macrophages. The macrophage assay identified the high biological activity and dose potency of 5-MeXAA in vivo, and was the most accurate in vitro predictor of the ability of congeners to induce either haemorrhagic necrosis of subcutaneous Lewis lung and colon 38 tumours or splenic natural killer activity. In vitro immune stimulation may be more appropriate than direct cytotoxicity for screening compounds with indirect mechanisms of antitumour activity.

Antitumor drug cross-resistance in vivo in a cisplatin-resistant murine P388 leukemia

Since 1978, over 50 clinically useful antitumor drugs or new candidate antitumor agents have been evaluated in vivo against cisplatin-resistant P388 leukemia (P388/DDPt) in our laboratories. Analysis of this data base has yielded insights into the cross-resistance, collateral sensitivity, and mechanisms of resistance of P388/DDPt. P388/DDPt was cross-resistant or marginally cross-resistant to eight agents [carmethizole.HCl, rhizoxin, dibromodulcitol, spirohydantoin mustard, hepsulfam, arabinosyl-5-azacytosine (ara-AC), tiazofurin, and deoxyspergualin]. Of these eight agents, the latter six have entered various phases of clinical trials. For these trials, it may be important to exclude or to monitor with extra care patients who have previously been treated with cisplatin. P388/DDPt was collaterally sensitive to six agents [fludarabine phosphate (2-F-ara-AMP), amsacrine (AMSA), mitoxantrone, etoposide (VP-16), batracylin, and flavone acetic acid] and, possibly, to two others (merbarone and echinomycin). These observations of collateral sensitivity suggest that a combination of cisplatin plus any one of these drugs might exhibit therapeutic synergism. Therapeutic synergism has been observed in animal models for combinations of cisplatin plus VP-16, AMSA, or mitoxantrone. The observation of collateral sensitivity for P388/DDPt to four agents (AMSA, mitoxantrone, merbarone, and VP-16) that have been reported to interact with DNA topoisomerase II suggests the possible involvement of the latter in cisplatin resistance. Both the increased sensitivity of P388/DDPt to these agents and a portion of its resistance to cisplatin could be the result of an increase in DNA topoisomerase II activity.

Anticoagulant treatment does not affect the action of flavone acetic acid in tumour-bearing mice

Flavone acetic acid (FAA) is a novel antitumour agent that has a profound effect on the vasculature in murine tumour models. Previously we have shown that FAA induces a coagulopathy and thrombocytopaenia in tumour-bearing mice, and the purpose of the present study was to determine the significance of the FAA-induced intravascular coagulation in the antitumour action of FAA. Several anticoagulant agents were tested for their effectiveness in altering ex vivo coagulation of murine plasma; heparin and ancrod were found to be most effective. These agents were administered to tumour-bearing mice prior to FAA and TNF treatment with little effect on the induced regrowth delay. However: the FAA-induced consumption of platelets in tumour-bearing mice was not blocked by anticoagulant treatment. These data suggest that platelet consumption occurs independently of the normal coagulation pathway, and further that fibrin deposition may not be a major factor in the antitumour action of FAA.

Selective induction of endothelial cell tissue factor in the presence of a tumour‐derived mediator: A potential mechanism of flavone acetic acid action in tumour vasculature

Flavone acetic acid (FAA) is a potentially useful anti-tumour agent which has been reported to induce changes in tumour vasculature, in particular loss of bloodflow. This led us to examine whether endothelium could be a cellular target of FAA action, with resultant modulation of cell-surface coagulant properties leading to activation of coagulation and blockade of tumour blood flow. Incubation of endothelium with FAA led to the expression of functional tissue factor on the cell surface, in a time-dependent and dose-dependent (half-maximal at 0.6-0.7 mg/ml) manner. Induction of tissue-factor activity resulted from de novo translation of the tissue factor message. To explain the selectivity of FAA's action on tumour vasculature in vivo, we considered its interaction with tumour-derived factors. Starting with serum-free FO-I-melanoma cell-conditioned medium, a co-factor enhancing FAA-mediated induction of endothelial tissue factor (FO-I factor) was partially purified by sequential ion exchange and reverse phase chromatography, followed by preparative SDS-PAGE. The FO-I factor migrates with an apparent Mr of approx. 20 to 25,000 on non-reduced SDS-PAGE, is sensitive to protease K, and augments the effect of FAA on endothelial-cell-tissue factor. This activity is not found in supernatants from non-neoplastically transformed cell lines. These data lead us to hypothesize that FAA exerts its action, at least in part, by promoting activation of coagulation on the endothelial surface, and this effect is selective for the tumour bed by virtue of its interaction with a tumour-derived factor. The interaction of FAA with host factors may be important for optimizing its therapeutic efficacy for a particular tumour.

Reactivity of flavone acetic acid and its acyl glucuronide

Reactivity of flavone acetic acid and its acyl glucuronide

Flavone acetic acid potentiates the induction of endothelial procoagulant activity by tumour necrosis factor

Treatment of human umbilical vein endothelial cells with flavone acetic acid (FAA) at 800 μg/ml for 4 h resulted in a 3–11-fold increase in procoagulant activity. This increase was due to enhanced tissue factor expression on the endothelial cell surface, as evidenced by the blocking of the enhanced clotting with antibody to tissue factor, by substitution of normal with factor VII deficient plasma, or by simultaneous treatment of the endothelial cells with cycloheximide or actinomycin D. FAA was not toxic to endothelial cell at concentrations up to 1.6 mg/ml over 4 h. Combined treatment with FAA and tumour necrosis factor α (TNF-α) (100 pg/ml) produced a 675-fold (range 160–1980) increase in tissue factor activity, compared to 5-fold and 50-fold increases for the individual agents respectively. Northern blotting of total RNA from cells treated with the combination of agents or either agent alone, followed by probing with a cDNA to human tissue factor demonstrated a synergistic increase in tissue factor mRNA after combination treatment. In vivo, the combination of FAA and TNF-α could be shown to induce greater growth delay in two murine tumours than would be predicted on the basis of the activity of either agent alone.

The relationship between tissue levels of flavone acetic acid (NSC 347512) and site dependent anti-tumour activity in murine colon tumours

Flavone acetic acid (FAA) is extremely active against subcutaneous transplantable tumours in mice, but disappointingly there has been no demonstrable clinical activity. Previous studies have shown that lung tumour deposits are less responsive than the same cells implanted subcutaneously. The aim of this study is to examine the tissue disposition of FAA in an attempt to explain this site-dependent activity. The data show clearly that FAA clearance curves are influenced by the presence of MAC 15A tumours growing either subcutaneously or systemically. The decreased clearance of FAA from MAC 15A tumour bearing animals does not however explain the resistance of lung deposits. Neither can this be explained by differences in metabolism in these different sites. Cytotoxic metabolites have not been detected either in vitro or in vivo and their role in the mechanism of action of FAA is questionable.

Natural killer (NK) and lymphokine activated killer (LAK) cell activity in patients (PTS) treated with favone acetic acid (FAA)

Natural killer (NK) cell activity was measured in nine patients with different solid tumors treated with flavone acetic acid (FAA). In three of them, NK cell activity was significantly increased, in two instances even after repeated courses of treatment. A significant increase in lymphokine activated killer (LAK) cell activity was also observed in three of four patients after in vivo treatment with FAA and in vitro incubation of lymphocytes with recombinant Interleukin-2. We observed some inter-individual variability in drug clearance, but no apparent correlation between drug plasma levels (neither peak nor AUC values) and the effects on NK and LAK activity.

Potential antitumor agents. 62. Structure-activity relationships for tricyclic compounds related to the colon tumor active drug 9-oxo-9H-xanthene-4-acetic acid

A series of tricyclic analogues of 9-oxo-9H-xanthene-4-acetic acid have been prepared and evaluated for their ability to cause hemorrhagic necrosis in subcutaneously implanted colon 38 tumors in mice, in an effort to extend the structure-activity relationships for this series. As was found previously with analogues of flavone-8-acetic acid (FAA) (Atwell et al. Anti-Cancer Drug Des. 1989, 4, 161), all electronic modifications of the XAA nucleus led to severe decreases or complete abolition of activity, suggesting narrow structure-activity relationships. Dipole moments for many of the compounds were computed, and the degree to which the molecular dipole moment lay out of the plane of the aromatic part of these molecules was found to be determined largely by the contributions from the acetic acid moiety relative to that from the tricyclic ring system. There did not appear to be any general relationship between the magnitude of the dipole moment and activity. However, for compounds containing the 9-carbonyl functionality, the orientation of the dipole vector may be of significance. In all compounds possessing an ether group peri to the acetic acid side chain, there was a close approach (ca. 2.4 A) between this and the side chain OH.

Phase I Clinical and Pharmacokinetic Trial of Flavone Acetic Acid

Flavone acetic acid is a synthetic benzopyrone derivative with an unknown mechanism of action. Thirty-eight patients (30 men and 8 women) were treated once a week for 4 weeks every 5 weeks with doses of flavone acetic acid ranging from 0.33 to 12.5 g/m2. At doses less than or equal to 3.9 g/m2, the drug was administered intravenously over 1 hour; at doses greater than or equal to 5.28 g/m2, the infusion period was lengthened to 6 hours. Treatment of all patients included hydration before and after treatment and alkalization to maintain urine pH at greater than or equal to 6.5. A dose-limiting toxic effect was hypotension at 10 g/m2. Pharmacokinetic studies revealed linear behavior in the eight patients studied, beginning at 3.9 g/m2. Peak plasma levels ranged from 125 to 630 micrograms/mL, with a mean terminal half-life of 22.4 hours. Immunologic monitoring was performed in three patients at 10 g/m2. A transient increase in CD16- and/or Leu-19-positive cells was noted in all three patients. In one patient, this increase correlated with a 10-fold increase in K562 cell killing. There were no objective tumor responses seen in this trial. The recommended phase II dose on this schedule is 8 g/m2. Further studies to elucidate the drug's mechanism of action and to define its immunologic properties are recommended.

Effect of environmental conditions (pH, oxygenation and temperature) on the cytotoxicity of flavone acetic acid and its dimethylaminoethyl ester

Bioflavonoids are known to inhibit enzymes in the glycolytic pathway and have been reported to decrease tumour blood flow. The antineoplastic capabilities of flavone acetic acid (FAA), dimethylaminoethyl-flavone-8-acetate (FAA ester) and quercitin (Q) as a function of pH, level of oxygenation and in conjunction with hyperthermia or SR-4233. In vitro, exposure of FSaIIC murine fibrosarcoma cells to various concentrations of FAA or FAA ester for 1 h demonstrated that both drugs were slightly more toxic toward hypoxic cells at 37 degrees C and pH 7.40 (but were somewhat less cytotoxic at pH 6.45 and 37 degrees C) than towards normally oxygenated cells. The cytotoxicity of FAA and FAA ester increased only minimally by concomitant treatment of cells at 42 degrees C or 43 degrees C. When temperatures of tumour-bearing mice anaesthetized with chloral hydrate and pentobarbital were measured both FAA (200 mg/kg) and Q (200 mg/kg) caused a more rapid drop in tumour versus core temperature, indicating a relative shutdown of tumour blood flow had been produced by these flavonoids. In Hoechst 33342 dye-defined subpopulations, both FAA and Q were only minimally cytotoxic in the subpopulation enriched in euoxic (bright) cells, producing surviving fractions of 0.70 and 0.29, respectively but were approximately 2-fold and 3-fold respectively more toxic towards the subpopulation enriched in hypoxic (dim) cells. When FAA preceded hyperthermia approximately a 3-4-fold increase in cell kill resulted from the combination in both subpopulations. Finally, when SR-4233, a selective hypoxic cell cytotoxic agent, was administered prior to FAA or Q and followed by hyperthermia the level of tumour cell killing increased so that the surviving fractions were 0.009 and 0.0055, respectively, in the dim cell subpopulation. These results indicate that FAA, FAA ester and Q may be most effectively used in a setting involving a combined modality regimen with a focus on the hypoxic tumour cell population.

Anti-tumour activity of flavone acetic acid (NSC 347512) in mice – influence of immune status

Flavone acetic acid (FAA) is a synthetic flavonoid with dramatic pre-clinical anti-tumour activity involving a vascular component in its mechanism but no clinical effects have been seen to date. As FAA also has immunomodulatory activity, immunological factors might explain differences in activity between mouse and man. This study examines the influence of host immune status on the anti-tumour activity of FAA. Two human colon tumour xenografts (COBA, HT-29) fail to respond to FAA in nude mice. The lack of activity of FAA against HT-29 xenografts cannot be explained on the basis of limited drug bioavailability as achievable plasma, and tumour levels of FAA are similar to those seen in sensitive murine colon tumours. The immune status of the host also influences the activity of FAA against two transplantable tumours of the mouse colon. Both these tumours are highly responsive to FAA in their normal NMRI hosts, but neither tumours exhibited significant growth delay in thymectomised NMRI or nude hosts. Histological examination of treated tumours revealed significant areas of haemorrhagic necrosis in all three hosts. These data suggest a clear immunological component in the mechanism of action of FAA which is separate from the previously described haemorrhagic necrosis.

Flavone acetic acid potentiates the induction of endothelial procoagulant activity by tumour necrosis factor : J.C. Murray, K.A. Smith, and D. Stern ∗. Endothelial Biology Group, CRC Gray Laboratory, PO Box 100, Mt. Vernon Hospital, Northwood, UK, and ∗Dept. of Physiology and Cellular Biophysics, Columbia University, N.Y., USA

Treatment of human umbilical vein endothelial cells with flavone acetic acid (FAA) at 800 &ml for 4 h resulted in a 3-H-fold increase in procoagulant activity. This increase was due to enhanced tissue factor expression on the endothelial cell surface, as evidenced by the blocking of the enhanced clotting with antibody to tissue factor, by substitution of normal with factor VII deficient plasma, or by simultaneous treatment of the endothelial cells with cycloheximide or actinomycin D. FAA was not toxic to endothelial cell at concentrations up to 1.6 mg/ml over 4 h. Combined treatment with FAA and tumour necrosis factor OL (TNF-a) (100 pg/ml) produced a 675fold (range 160-1980) increase in tissue factor activity, compared to S-fold and SO-fold increases for the individual agents respectively. Northern blotting of total RNA from cells treated with the combination of agents or either agent alone, followed by probing with a cDNA to human tissue factor demonstrated a synergistic increase in tissue factor mRNA after combination treatment. In viva, the combination of FAA and TNF-a could be shown to induce greater growth delay in two murine tumours than would be predicted on the basis of the activity of either agent alone.

Induction of natural killer activity by Xanthenone analogues of flavone acetic acid: Relation with antitumour activity

Flavone-8-acetic acid (FAA) induces haemorrhagic necrosis and tumour regression in experimental tumours and induces natural killer (NK) activity. Xanthenone-4-acetic acid (XAA) forms the basis of a series of analogues of FAA which vary in antitumour potency. FAA, XAA and 15 XAA derivatives were tested for their ability to induce either NK activity in mouse spleens or haemorrhagic necrosis in mouse colon 38 tumours. Some derivatives were active in both assays (one at a dose 8-fold lower than that of FAA). When both assays were quantitated, a significant correlation ( r = 0.85; P < 0.001) was found. NK assays could be useful in screening compounds such as FAA and XAA analogues which appear to mediate their antitumour activity by biological response modification. Since tumour necrosis may not be mediated directly by NK cells, FAA and active XAA derivatives may exert pleiotropic effects that include NK induction and tumour necrosis by acting on host cells to release cytokines.

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.

Flavone acetic acid--an interesting novel therapeutic agent or just another disappointment?

Flavone acetic acid--an interesting novel therapeutic agent or just another disappointment?

Antitumor activity of chemical modified natural compounds

Search of new activity substances starting from chemotherapeutic agents, continuously appears in international literature. Perhaps this search has been done more frequently in the field of antitumor chemotherapy on account of the unsuccess in saving advanced stage patients. The new point in this matter during the last decade was computer aid in planning more rational drugs. In near future "the accessibility of super computers and emergence of computer net systems, will open new avenues to rational drug design" (Portoghese, P. S., J. Med. Chem. 1989, 32, 1). Unknown pharmacological active compounds synthetized by plants can be found even without this electronic devices, as traditional medicine has pointed out in many countries, and give rise to a new drug. These compounds used as found in nature or after chemical modifications have produced successful experimental medicaments as FAA, "flavone acetic acid" with good results as inhibitors of slow growing animal tumors currently in preclinical evaluation for human treatment. In this lecture some international contributions in the field of chemical modified compounds as antineoplastic drugs will be examined, particularly those done by Brazilian researches.

The Effect of Therapy on Tumour Vascular Function

It has been established that malignant tissue as a consequence of abnormal morphogenesis has a structurally abnormal blood supply. These structural and as a consequence functional differences between normal and neoplastic vasculature provide a basis for selective modulation of tumour vascular function. Agents have been identified which can induce both irreversible and reversible effects on tumour blood flow. Hyperthermia, photodynamic therapy, tumour necrosis factor and flavone acetic acid are known to elicit most of their anti-tumour effect via irreversible changes in tumour vascular function. In addition to the extensive tumour cell kill and thus therapeutic potential provided by such chronic modulation of blood flow, acute transient changes in macroregional and microregional tumour blood flow could also play an important role if used appropriately with conventional therapies. The use of this latter type of modulation is discussed with reference to known examples of such 'vasoactive' compounds. It is also emphasized that blood flow changes induced in tumour tissue can be a 'double-edged sword' with detrimental consequences for therapeutic outcome if inappropriate changes are induced, for example, reductions in flow at the time of conventional radiotherapy or chemotherapy by agents not considered to be 'vasoactive'. To emphasize this point examples of blood flow modulation by pimonidazole and cis-platinum, agents that are used in conjunction with radiotherapy, are described.

Flavone Acetic Acid: Is Vascular Shutdown the Crucial Mechanism of Action

Flavone Acetic Acid: Is Vascular Shutdown the Crucial Mechanism of Action

Effects of Two Tumour Blood Flow Modifiers, Hydralazine and Flavone Acetic Acid, on KHT Tumours and Normal Tissues in Mice

Effects of Two Tumour Blood Flow Modifiers, Hydralazine and Flavone Acetic Acid, on KHT Tumours and Normal Tissues in Mice