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

Summary 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 difluoromethyornithine (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.     

Enhanced Uptake of [3H] Spermidine by 9L Rat Brain Tumors After Direct Intratumoral Infusion of Inhibitors of Enzymes of the Polyamine Biosynthetic Pathway

We have been exploring the feasibility of delivering ionizing radiation to brain tumor cells by using tritium labeled polyamines. Polyamines are taken up preferentially by dividing cells and form noncovalent bonds with DNA. Their uptake can be enhanced by drugs which deplete endogenous polyamines. To test this in vivo, 9L cells were implanted in the striatal region of the brain in male Fisher 344 rats. Osmotic pumps containing trace amounts of [³H] spermidine or [³H] putrescine with either difluoromethylornithine or combinations of 3 inhibitors of enzymes of the polyamine biosynthetic pathway were implanted subcutaneously and were connected to intratumoral cannulas. After 14–16 days the brains were removed and sliced in the coronal plane. The diameters of the tumors were measured and tumor tissue was dissected from each slice, weighed and lysed for scintillation counting. It was found that difluoromethylornithine enhanced the uptake of [³H] putrescine while a combination of inhibitors of enzymes of the polyamine biosynthetic pathway enhanced the uptake of [³H] putrescine and [³H] spermidine producing a localized region of radioactivity in the 9L tumor. It is estimated that if the [³H] polyamines were at higher specific activity (commercially available), instead of the trace dose given here, the [³H] polyamine uptake would be sufficient to kill 9L tumor cells within a 2 to 3 week period.     

人早幼粒白血病细胞移植瘤株的建立及其实验治疗

将人早幼粒白血病细胞(HL-60)移植裸鼠皮下,形成了实体型移植瘤(HL-60X)。瘤株已传7代,成瘤率达100％。用该移植瘤模型初步观察到,多胺生物合成抑制剂二氟甲基乌氨酸(DFMO)、阿霉素、及两种药物联合使用,对肿瘤生长有抑制作用。抑制率分别为:55％、65％、99.4％。DFMO组对动物体重略有影响,阿霉素组则不明显。瘤组织病理检查表明,除程度不同的瘤细胞坏死外,对HL-60具有诱导分化作用。用药后肿瘤组织再次接种裸鼠,未见成瘤。实验结果说明,DFMO有增强阿霉素的抗癌作用。     

A phase II study of α-difluoromethylornithine (DFMO) for the treatment of metastatic melanoma

Difluoromethylornithine (DFMO) is an irreversible enzyme-activated inhibitor of ornithine decarboxylase, a key enzyme in polyamine synthesis. We have screened for potential anti-cancer activity of DFMO using a clonogenic assay, which suggested that melanoma might have sensitivity to this agent. Accordingly, we have performed a phase II trial of DFMO (2 g/m² po q 8 h) in 24 patients, 21 of whom were evaluable for response. One patient achieved a complete response of a large subcutaneous mass for 11 months. Although stabilization is frequently difficult to measure, seven patients appeared to stabilize previously active disease, with a median duration of response of eight weeks. Toxicity was significant and DFMO was discontinued in five patients due to side effects — hearing loss alone in four and hearing loss associated with thrombocytopenia in the fifth patient. Hearing changes occurred in ten patients. Other side effects were mild. These data indicate that DFMO as a single agent may be an effective therapy for melanoma. A phase II trial of DFMO in previously untreated patients using a different schedule to decrease hearing loss is warranted. Additionally, several in vitro and animal models suggest that DFMO plus interferon are synergistic, and this combination might be used for a clinical trial as well.     

A Precolumn Derivatization High-Performance Liquid Chromatographic (HPLC) Procedure for the Quantitation of Difluoromethylornithine in Plasma

Pharmaceutical Research -     

African trypanosome infections of the nervous system: Parasite entry and effects on sleep and synaptic functions

The extracellular parasite Trypanosoma brucei causes human African trypanosomiasis (HAT), also known as sleeping sickness. Trypanosomes are transmitted by tsetse flies and HAT occurs in foci in sub-Saharan Africa. The disease, which is invariably lethal if untreated, evolves in a first hemo-lymphatic stage, progressing to a second meningo-encephalitic stage when the parasites cross the blood–brain barrier.     

Potentiation of naphthoxyloside cytotoxicity on human tumor cells by difluoromethylornithine and spermine-NONOate

Here we demonstrate a synergistic and tumor selective cytotoxic effect by combined treatment with naphthoxylosides, polyamine synthesis inhibitor, and polyamine based nitric oxide (NO) donor, using in vitro human tumor models. We have earlier reported that heparan sulfate priming naphthoxyloside, 2-(6-hydroxynaphthyl)-O-beta-D-xylopyranoside, which inhibits growth of human tumor cells in vitro and in vivo models, undergoes NO dependent cleavage and accumulates in the nuclei of tumor cells. Polyamine depletion using alpha-difluoromethylornithine (DFMO) increases both the number of NO sensitive sites in heparan sulfate and uptake of the polyamine based NO donor, spermineNONOate, thereby enhancing formation of growth-inhibitory NO induced heparan sulfate products with specific cytotoxic effect on tumor cells. We also show that peracetylation of xylosides doubles the antiproliferative effect towards human cancer cells by making these compounds more permeable to the cells.     

INHIBITORY EFFECT OF DEMO ON THE GROWTH OF TRANSPLANTED HUMAN COLON CANCER IN NUDE MICE

A human colon cancer cell line Hce- 8693 was heterotransplanted in nude mice. Polyamine blosythesis Inhibitor a- dlfiuoromethylomithine (DFMO ) show a marked reproducible inhibition in this model. The size and weight of transplanted tumor In DFMO group were smaller than those of the control group and the average inhibition rate was 72.8% (P < 0.001) . DFMO showed higher tumor inhibitory rate than 5-Fu (35. 4%) (P<0. 001) . Furthermore. DFMO demonstrated less severe bone marrow inhibition in the nude mice than 5-Fu (20. 0% Vs 53. 2%. P<0. 001) .There was no synergistic action in these two drugs at the experimental dose. The concentration of putrescine and spermidine in the plasma and tumor tissue in the DFMO group were 70% lower than those of the control group (P<0. 001) . These results indicate that the anti-tumor effect of DFMO might be explained by the inhibition of polyamine biosynthesis and this study provides an experimental basis for future clinical application of DFMO.