Flavone Acetic Acid Research Articles

Haematological effects in mice of the antitumour agents xanthenone-4-acetic acid, 5,6-methyl-xanthenone-4-acetic acid and flavone acetic acid

Treatment of C57Bl/6 x DBA/2 mice with the maximal tolerated dose of flavone-8-acetic acid (FAA, 1300 mumol/kg), xanthenone-4-acetic acid (XAA, 1090 mumol/kg), or its dose-potent derivative 5,6-dimethyl-xanthenone-4-acetic acid (5,6-MeXAA, 100 mumol/kg) resulted within 24 h in a dramatic reduction in the number of circulating lymphocytes, an elevation in haemoglobin concentrations and a reduction in platelet numbers. Neutrophil counts either remained unchanged or were slightly elevated. All three compounds caused a marked loss of cells in the thymus. Examination of histological sections of thymus at 48 h following treatment with XAA revealed a selective depletion of cortical thymocytes and no effects on the epithelium or other thymic structures. A transient decrease in cell numbers was seen in the spleen and femoral bone marrow, with recovery to normal levels occurring within 3 days. The number of haemopoietic stem cells, colony-forming units in culture (CFU-c), in the femoral bone marrow increased after drug administration despite the occurrence of a decrease in the overall number of cells in the femur. In contrast to the increase in CFU-c numbers seen in vivo, 2 h exposure of bone-marrow cells to FAA, XAA or 5,6-MeXAA in vitro resulted in a decrease in the surviving fraction of CFU-c. The results are consistent with the hypothesis that the in vivo haematological effects of these compounds are indirect, perhaps being mediated through the induction of cytokines, and contrast with the haematological effects of conventional antitumour agents. The biochemical and haematological effects are unlikely to be the cause of the acute toxicity observed for these compounds.

Induction of hypoxia in the KHT sarcoma by tumour necrosis factor and flavone acetic acid.

The interaction of FAA or TNF with radiation was studied in the murine KHT sarcoma. When used alone both agents showed a dose- and time-dependent toxicity towards the tumour cells and significantly reduced tumour blood flow within 1 h of treatment. When used in combination with radiation, both TNF and FAA caused an increase in the fraction of hypoxic cells in the KHT tumour. This was assessed by an in vivo/in vitro clonogenic assay and by a comparison with the radioprotection provided by clamping tumours prior to and during irradiation. When TNF was given at a dose of 2.5 X 10(5) U/kg an increase in tumour hypoxia was seen after 30 min. Close to 100% radiobiological hypoxia was reached by 1 h after treatment, lasting for up to 16 h. Doses of TNF below 0.25 X 10(5) U/kg did not induce levels of hypoxia comparable to clamping when administered 3 h prior to irradiation. Similarly, FAA produced a rapid increase in tumour hypoxia: a dose of 200 mg/kg induced close to 100% radiobiological hypoxia when give 1 h prior to irradiation. Complete tumour hypoxia was still apparent 18 h after treatment with FAA. Administered doses of FAA below 100 mg/kg did not produce close to 100% radiobiological hypoxia when administered 3 h prior to irradiation.

Differential efficacy of flavone acetic acid against liver versus lung metastases in a human tumour xenograft

A human ovarian carcinoma, IGROV-1, was xenografted into different sites (i.p., s.c., i.v., and intrasplenically) in nude athymic female mice to investigate the pattern of antitumour efficacy of FAA and compare it to that of doxorubicin and cisplatin, two established cytotoxic drugs. Ascitic and lung-growing tumours totally failed to respond to FAA, whereas s.c. and liver-growing tumours were significantly growth inhibited. This pattern of activity differs from that achieved by the two conventional cytotoxic drugs, which were active against the IGROV-1 tumour growing in all of the tested sites. These studies indicate that cytotoxicity is not the major determinant of FAA antitumour efficacy even against human tumour xenografts. Moreover, the dramatic difference between the sensitivity of lung and liver tumour colonies demonstrates the great importance of the site of tumour growth for FAA efficacy.

The Effect of Combining Flavone Acetic Acid and Hyperthermia on the Growth of a C3H Mammary Carcinomain Vivo

The Effect of Combining Flavone Acetic Acid and Hyperthermia on the Growth of a C3H Mammary Carcinoma<i>in Vivo</i>

Early Spatial and Temporal Changes in Tumour Perfusion after Administration of Flavone Acetic Acid

Early Spatial and Temporal Changes in Tumour Perfusion after Administration of Flavone Acetic Acid

Necrosis in non-tumour tissues caused by flavone acetic acid and 5,6-dimethyl xanthenone acetic acid

Necrosis in non-tumour tissues caused by flavone acetic acid and 5,6-dimethyl xanthenone acetic acid

Flavone acetic acid suppresses human peripheral blood lymphocyte and human colonic lamina propria lymphocyte DNA synthesis

Flavone 8-acetic acid (FAA) is a new experimental antitumor drug with activity against various murine and human solid tumors in vitro and in vivo. We previously demonstrated that FAA suppressed the growth of a human colon cancer cell line (HCT-116). In this study we investigated the effect of FAA on human peripheral blood (PBL) and human colonic lamina propria lymphocyte (LPL) DNA synthesis. Our results show that FAA inhibited DNA synthesis in PBL and LPL in a dose-dependent fashion. In addition, FAA inhibited the activity of the intracellular enzyme, ornithine decarboxylase (ODC), in stimulated PBL and LPL. FAA did not inhibit phorbol ester (PDB) and calcium ionophor(ionomycin)-stimulated LPL DNA synthesis. These results suggest that FAA alters DNA synthesis of human peripheral and colonic mucosal lymphocytes. We postulate that FAA may affect the human peripheral and mucosal immune system.

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.

The use of vascularised spheroids to investigate the action of flavone acetic acid on tumour blood vessels

EMT6 multicellular spheroids were introduced into the peritoneal cavities of mice and allowed to become vascularised, resulting in solid spherical tumours. The necrotic cores of the initially avascular spheroids were replaced by vascularised tumour tissue but the outer zones of the spheroids failed to become vascularised. The presence of both vascular and avascular components in each spheroid allowed the role of the vasculature in the antitumour action of flavone acetic acid (FAA) to be determined. Eighteen hours after treatment with FAA 0.8 mmol kg-1, the vascularised core became necrotic and haemorrhagic, while the outer avascular zone remained viable. Tumour cells which were infiltrating superficial sub-mesothelial fat did not become necrotic despite the presence of numerous thrombi in associated vessels. Injection of two fluorescent vascular markers, the first (Hoechst 33342) together with FAA, and the second (10-nonyl acridine orange) 4 h later, demonstrated that there is a marked loss of blood flow in the spheroids. These results provide further evidence that FAA kills blood vessel-dependent tumour cells by interrupting the tumour blood supply.

Flavone acetic acid antitumour activity against a mouse pancreatic adenocarcinoma is mediated by natural killer cells.

Flavone acetic acid (FAA) is one of the most active antitumour agents against mouse solid tumours. A number of reports favour the hypothesis that FAA could behave as a biological response modifier; in fact FAA stimulates natural killer (NK) cells, induces secretion of type I interferon and synergizes with interleukin-2 to increase NK/lymphokine-activated killer (LAK) activity in vivo. However, there is no conclusive evidence that the antitumour activity of FAA is mediated via the modulation of NK/LAK cells. The present study was designed to evaluate whether the reported activation of NK cells is instrumental in FAA antitumour activity. FAA (180 mg/kg, i.v. on days 3, 7 and 11 after tumour implant) was significantly effective in inhibiting the subcutaneous growth of the pancreatic adenocarcinoma PAN/03 in C57/Bl mice. After 132 days the number of tumour-free survivors was 36%, whereas in the control group receiving no treatment, or in the group of mice treated with 10 micrograms/mouse of alpha-asialo-GM1 the value was only 0 or 6.7%, respectively. The combination of FAA and alpha-asialo-GM1 resulted in only 6% tumour-free mice. In parallel experiments, splenocytes and peritoneal cells from C57/B1 mice were tested in a standard cytotoxicity NK assay. While animals treated with FAA showed a significant increase in NK activity, those injected with alpha-asialo-GM1 had very low levels, and the combined treatment of FAA and alpha-asialo-GM1 resulted in a lower or similar NK activity compared to that in untreated mice. The fact that the abrogation of the NK-stimulating effect of FAA is accompanied by a lack of anti-tumour activity indicates that, at least in this experimental model, FAA is likely to act via an immunomodulatory mechanism.

Interaction between flavone acetic acid (LM-975, NSC 349512) and radiation in Glasgow's osteogenic sarcoma in vivo

Flavone acetic acid (FAA) is a new anticancer agent in Phase II trials in Europe. In preclinical testing FAA showed broad activity against murine solid tumors and minimal activity against murine leukemias. Our interest in studying the combination of FAA and radiation was based on two of its biological effects which might modify radiation damage. First, FAA depletes ATP and inhibits macromolecular synthesis which are needed to repair radiation-induced DNA strand breaks; and second, inhibition of tumor blood flow by FAA could lead to radiobiological hypoxia. Various schedules of FAA (170 mg/kg I.V.) (n = 9, SF = 0.44) and radiation (10 Gy) (n = 9, SF = 0.37) were investigated against s.c. implanted Glasgow osteogenic sarcoma. In the same model we studied both the kinetics of ATP depletion by 31P-Nuclear Magnetic Resonance Spectroscopy and the repair of radiation induced single and double strand breaks by alkaline elution. The combined response was not significantly different from log-additive when radiation was given 24, 5 or 1 hr before FAA. When FAA was given immediately before radiation an increase in tumor response, significantly different from log-additive ( p = 0.03) was observed. This enhancement disappeared when radiation was delayed for between 1 and 48 hr after FAA. While decreased ATP levels and increased response to radiation occurred within minutes after FAA administration, no effect of FAA at either 180 or 200 mg/kg was observed on the repair of radiation induced single or double strand breaks (10 and 50 Gy, respectively; 5 hr after FAA) in spite of significant ATP depletion in the tumors.

Recombinant interleukin-2 (rIL-2) with flavone acetic acid (FAA) in advanced malignant melanoma: a phase II study

Recombinant interleukin 2 (rIL-2) and flavone acetic acid (FAA) were used to treat 34 patients with progressing metastatic melanoma. Five patients had solely non-visceral disease and the median number of organ sites involved was two. Five doses of rIL-2 were given, the first dose intrasplenically via a femoral artery catheter with a further dose 4 h later i.v. and the other doses i.v. on alternate days. The rIL-2 dose was 11 x 10(6) Cetus units m-2; the day before rIL-2, FAA (4.8 G m-2) was given as a 6 h i.v. infusion, in order to enhance further killer cell activity. A total of three courses at 21-day intervals was planned and 74 courses in all were given. Despite the high dose of rIL-2 and the potential overlapping toxicity affecting blood pressure with the addition of FAA, side-effects were generally mild. There were only five episodes of grade 4 toxicity: one of ventricular tachycardia and four other episodes of transient biochemical or haematological disturbance. Grade 3 hypotension or hypertension occurred on 22 courses but again was transient. No patient required intensive care facilities. Five patients had tumour response, one being complete. Responses occurred in pulmonary and hepatic metastases, but mainly in non-visceral sites. Eleven patients remain alive at 6-17 months and in five there is no relapse or progression of disease. Despite the impressive results in animal tumour models, the addition of FAA to rIL-2 in the present study has not markedly improved results over rIL-2 alone.

Light-Induced Breakdown of Flavone Acetic Acid and Xanthenone Analogues in Solution

Light-Induced Breakdown of Flavone Acetic Acid and Xanthenone Analogues in Solution

Flavone acetic acid distribution in human malignant tumors

The pharmacokinetics of flavone acetic acid (FAA) after a dose of 4.8 mg/m2 given i.v. over 1 h was investigated in 13 patients with different solid tumors. The mean volume of distribution and clearance were 52 +/- 4 l/m2 and 2.6 +/- 0.2 l/h x m2, respectively. A tumor or metastasis biopsy was obtained from six patients 2 h after the end of infusion. Tumor FAA levels ranged from 39.6 to 148.8 micrograms/g and were similar to those obtained after a therapeutic i.v. dose of 200 mg/kg FAA in animals bearing Pan/03 tumor, which is very sensitive to the drug. Although FAA tumor concentration could be detected only during one interval and we therefore cannot draw a definitive conclusion, differences in the agent's antitumor activity in mice and patients (i.e. very active in the former and inactive in the latter) are apparently not due to discrepancies in drug distribution and pharmacokinetics.

Recombinant interleukin-2 (rIL-2) with flavone acetic acid (FAA) in advanced malignant melanoma: immunological studies

Natural killer (NK) cell activity and lymphokine activated killer (LAK) cell cytotoxicity were measured in patients receiving recombinant interleukin 2 (rIL-2) and flavone acetic acid (FAA) for treatment of progressing metastatic melanoma. NK activity was increased in 23 of 26 patients and LAK activity induced in 13 of 26 patients. However, levels of cytotoxicity in the present study were not significantly greater than a previous study using rIL-2 alone. LAK cell precursors demonstrated by in vitro incubation of pretreatment lymphocytes with IL-2 and subsequent cytotoxicity were no different in the patients compared to normal controls. Analysis of cell surface phenotypes failed to reveal any significant changes in the cell populations examined, including IL-2R and Leu 19. Although five patients had tumour response, one being complete, there was no correlation with the immunological parameters examined.

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)

Flavone acetic acid and plasma protein binding

Both the capacity of healthy human, cancer patient, and mouse plasma proteins to bind flavone acetic acid (FAA) and the qualitative differences in the plasma protein-binding site were studied. The binding capacity of plasma proteins for FAA was saturated within the therapeutic range in both species. The binding of FAA to plasma protein was significantly greater in both healthy human and cancer patient plasma than in mouse plasma. Plasma from patients with cancer bound on the average less FAA than did healthy patient plasma. The concentration of albumin in the plasma varied between healthy humans, cancer patients, and mice, being 5.3 +/- 0.7, 4.7 +/- 0.8, and 3.9 +/- 0.3 g/100 ml, respectively. The protein binding of FAA was found to be dependent on the plasma albumin concentration, but albumin concentration alone was not adequate for the accurate prediction of the percentage of FAA protein bound. Scatchard plots indicated that healthy human plasma had a greater number of high-affinity binding sites than did mouse plasma. FAA binds at the indolebenzodiazepine binding area on albumin and can be displaced from this site by salicylic acid and clofibric acid, but only at supratherapeutic concentrations. Our results indicate that alterations in plasma albumin could contribute to a variable effect with FAA. Therefore, the influence of serum albumin concentration and the nonlinearity of FAA protein binding should be considered in assessment of the appropriateness of a dose schedule for FAA.

Role of T cells and tumour necrosis factor in antitumour activity and toxicity of flavone acetic acid

To investigate the importance of natural killer (NK) and T cells in the inhibition of tumour growth by flavone acetic acid (FAA), colon 26 murine carcinoma was grafted subcutaneously in euthymic and athymic mice. FAA was active in euthymic but not in athymic mice (ratio between tumour weight in treated vs. control animals [T/C], 27% and 92%, respectively). NK cell activity was increased in both mouse strains, indicating a lack of major involvement of this lymphocyte population in FAA efficacy. In euthymic mice tumour-specific T cells were activated, and after in vivo depletion of lymphocyte subpopulations (L3T4 and Lyt2), tumour inhibition by FAA was abrogated (T/C %, 88%). Antitumour efficacy of FAA was also reduced when the treatment was followed by injection of antitumour necrosis factor alpha (TNFα) antibodies. FAA toxicity depended on tumour weight at the time of treatment: 200 mg/kg caused 0 and 100% mortality in mice bearing tumour nodules under 50 and over 300 mg, respectively. When anti-TNFα antibodies were given after FAA treatment, the toxicity was greatly reduced ( 3 14 mice died compared with 10 15 ).

Flavone acetic acid induces a coagulopathy in mice.

The effects of flavone acetic acid (FAA) on the coagulation properties of plasma from tumour-bearing and non-tumour-bearing mice have been investigated. The study was carried out primarily on CBA mice and the CaNT tumour, although substantiating data are included for two other tumours grown in the WH strain. FAA was injected at a range of single doses up to a maximum of 300 mg kg-1, and clotting properties of the plasma were measured in vitro at various times after FAA administration. Platelet numbers and the concentration of fibrin degradation products (FDP) in the plasma were also determined. Following a dose of 300 mg kg-1, the clotting times were significantly reduced at 15-30 min in both tumour-bearing and non-tumour-bearing mice of both strains. Detailed studies on coagulation in the CBA strain (+/- CaNT tumour) indicate that in tumour-bearing animals the initial decrease in clotting time is followed 4-6 h later by an increase in clotting time, thrombin time and FDP levels. Platelet counts of tumour-bearing mice also decreased significantly over this period. Similar experiments in non-tumour-bearing mice did not show these late effects. All the data from the coagulation tests on mice with CaNT tumours are consistent with the hypothesis that intravascular coagulation occurs following treatment with FAA, and that vascular occlusion in tumours, as a results of FAA-induced coagulopathy, may contribute to tumour regression.

Vascular collapse after flavone acetic acid: A possible mechanism of its anti-tumour action

Flavone acetic acid (FAA, LM 975) causes regression and growth retardation in several solid murine tumours. The mechanism of action is unknown, although various lines of evidence suggest an indirect cytotoxic effect. We have carried out preliminary studies on the effect of FAA on relative blood flow in six experimental murine tumours using 86RbCl extraction. We have also measured growth delay after treatment with the same dose of FAA ( 200 mg/kg). The data show that the drug induces a drop in tumour perfusion within 6 h of treatment in all of the tumours, and that this can be correlated with the growth delay measured. We conclude that vascular collapse may be an important component of the action of this drug, and that further investigation of this phenomenon is warranted.