Biochemical modulation of 5-fluorouracil with leucovorin or delayed uridine rescue. Correlation of antitumor activity with dosage and FUra incorporation into RNA.

Two strategies for modulation of 5-fluorouracil (FUra) activity were compared in vivo in advanced murine CD8F1 breast tumors with regard to three parameters: chemotherapeutic activity, inhibition of thymidylate synthase (TSase) activity, and incorporation of FUra into RNA, (FU)RNA. Inhibition of TSase by FUra was modulated by leucovorin (LV), and the incorporation of FUra into RNA was increased by the administration of otherwise lethal doses of FUra followed by uridine "rescue". Thymidylate synthase activity was inhibited substantially (49%) by low-dose FUra at 25 mg/kg, but was not further enhanced (48%) by repeated daily treatments at the same dose (FUra25 x 4). Inhibition of TSase was somewhat enhanced (55%) by the addition of LV to FUra25 x 4, and a greater therapeutic effect was obtained with FUra25 x 4 + LV over FUra25 x 4 alone. FUra as a single agent at the maximum tolerated weekly dose of 100 mg/kg inhibited TSase activity 66-73%. This inhibition was further enhanced slightly by the addition of LV (71-82%), and its therapeutic efficacy was greater than with FUra25 x 4 with or without LV. However, in contrast to low dose FUra25 x 4, the antitumor effect of FUra100 was not enhanced by LV. (FU)RNA increased with FUra dose from 0.4 (FUra25) to 2.2 nmol/mg DNA (FUra100). At a very-high-dose of FUra (200-225 mg/kg) followed by uridine "rescue", TSase inhibition was not further enhanced, but both (FU)RNA (4.8 nmol/mg DNA) and the therapeutic efficacy were increased. Since TSase could not be further inhibited at doses above FUra100, the increased chemotherapeutic efficacy correlated with increased (FU)RNA.     

Diurnal variation in the therapeutic efficacy of 5-fluorouracil against murine colon cancer

Mice bearing the murine colon carcinomas Colon 38 or Colon 26 were treated with 5-fluorouracil (5 FU) (60 or 100 mg/kg, respectively) weekly for 4 weeks at 08.30 hr or at 18.30 hr. The antitumor effect of treatment at 08.30 hr was significantly better for both types of tumors, but most pronounced for Colon 38. Toxicity was evaluated after administration of 60 mg 5 FU/kg. No thrombocytopenia was observed. Leucopenia was observed after treatment at 18.30 hr. It is concluded that the therapeutic efficacy of 5 FU against murine colon cancer is higher when 5 FU is administered at 08.30 hr.     

奥沙利铂联合氟尿嘧啶和亚叶酸钙治疗晚期结直肠癌的疗效观察

目的探讨奥沙利铂、5-氟脲嘧啶和亚叶酸钙联合治疗晚期结直肠癌的疗效及不良反应。方法 40例晚期结直肠癌患者均采用奥沙利铂联合5-氟尿嘧啶和亚叶酸钙治疗,治疗方案为:奥沙利铂130mg/m2静脉滴注4h,第1天;亚叶酸钙200mg/m2静脉滴注2h,第1～5天(在静脉滴注5-氟尿嘧啶之前),5-氟尿嘧啶400mg/m2静脉滴注4～6 h,平均用药4周期,2周期后进行疗效评价。结果 40例晚期结直肠癌患者中,完全缓解(CR)4例(10%),部分缓解(PR)18例(45%),稳定(SD)10例(25%),进展(PD)8例(20%),总有效率(ORR)为55%。不良反应为厌食疲乏、皮肤色素沉着、神经毒性、手足综合症、腹泻、恶心呕吐、肝功损害、白细胞下降,多数患者能耐受。结论奥沙利铂联合5-氟尿嘧啶和亚叶酸钙治疗晚期结直肠癌的疗效肯定,毒副反应小,患者能耐受,值得推广。     

Levofolinate and fluorouracil combination therapy

Levofolinate and fluorouracil regimen (l-leucovorin and 5 fluorouracil regimen) is a biochemical modulation of 5 fluorouracil (5FU) by leucovorin (LV). In the USA and Europe d,l-LV and 5FU regimen is frequently administered for colorectal cancer treatment and recognized as the standard regimen. In Japan, multi-institutional clinical trials of l-leucovorin (l-LV), a bioactive diastereomer of leucovorin, and 5FU combination were conducted for the treatment of advanced gastrointestinal cancer with comparable results to the US/Europe data. This l-LV and 5FU regimen was approved in August 1999 for the indications of advanced gastric cancer and colorectal cancer. The dosage and administration is referred to the weekly method developed at RPMI. Recently, the irinotecan (CPT-11) or oxariplatin plus LV and 5FU combination showed higher antitumor activities than the LV and 5FU combination with increased progression-free survival. These regimens, however, are not yet properly established because clinical trial results with Japanese patients are not completed for agreement of the dosage and administration schedule. For the l-LV and 5FU regimen diarrhea and leukocytopenia, including grade 3 and higher, were reported as the major adverse events. Administration for eligible patients with periodical monitoring of diagnostic data is necessary.     

Intraperitoneal 5-fluoro-2′-deoxyuridine with escalating doses of leucovorin: Pharmacology and clinical tolerance

Summary In a preceding study, we established the tolerance and pharmacokinetic behavior of 5-fluoro-2-deoxyuridine (FdUrd) given by the intraperitoneal (IP) route. A dose of 3 g daily × 3 days was found satisfactory for Phase II study and exploration of biochemical modulation. Therefore, the current study was conducted to study the tolerance and pharmacokinetics of such a dose-schedule and route of FdUrd combined with escalating doses of leucovorin (LV). Fourteen patients were entered and 13 were evaluable for tolerance determination. Pharmacologic determinations of IP FdUrd and 5-Fluorouracil (FUra) derived from it and LV were obtained by HPLC methods on 11 occasions. Findings were compared with the preceding study of FdUrd alone. LV did not appear to alter the tolerance of IP FdUrd even in the four patients receiving the highest dose of LV (640 mg). Toxicities included nausea, vomiting, and rarely neutropenia and diarrhea. Pharmacokinetic parameters indicate a parallel rate of egress of FdUrd and LV from the peritoneal cavity. The pharmacologie advantage for FdUrd is at least 3 logs as previously reported and one log for LV. Evidence of antitumor effect was noted particularly among untreated patients with gastrointestinal primaries. We conclude that IP FdUrd 3 g and LV in doses of up to 640 mg x 3 days are well tolerated. Since FdUrd is more potent, has an even greater hepatic clearance and shows greater potential for modulation with LV than FUra, it may be the preferred fluoropyrimidine for subsequent studies via the IP route in the treatment of carcinomas with prominent peritoneal spread. The pharmacologie advantage for leucovorin is limited but it is a good marker for peritoneal clearance since it parallels FdUrd clearance.Abbreviations FdUrd 5-fluoro-2-deoxyuridine - FUra 5-fluorouracil - LV leucovorin or 6(R,S)-5-formyl tetrahydrofolate - IP intraperitoneal therapy - CHexUP cyclophosphamide - Hexalen^® 5-fiuorouracil, Platinol^® (cisplatin)     

Modulation of 5-fluorouracil host toxicity by 5-(benzyloxybenzyl)barbituric acid acyclonucleoside, a uridine phosphorylase inhibitor, and 2',3',5'-tri-O-acetyluridine, a prodrug of uridine

Administration of 200 mg/kg of 5-fluorouracil (FUra) to mice bearing human colon carcinoma DLD-1 xenografts resulted in 100% mortality. Oral administration of 2000 mg/kg of 2',3',5'-tri-O-acetyluridine (TAU), a prodrug of uridine, in combination with 120 mg/kg of 5-(benzyloxybenzyl)barbituric acid acyclonucleoside (BBBA), the most potent known inhibitor of uridine phosphorylase (UrdPase, EC 2.4.2. 3), 2 hr after the administration of the same dose of FUra completely protected the mice (100% survival) from the toxicity of FUra. This combination also reduced tumor weight by 67% compared with 46% achieved by the maximum tolerated dose (50 mg/kg) of FUra alone. Similarly, administration of BBBA plus TAU 1 hr before or 4 hr after the administration of FUra reduced the tumor weight by 53 and 37%, respectively. However, these schedules were less effective in protecting the host from the toxicity of FUra than when the treatment was carried out at 2 hr after FUra administration. TAU alone did not protect from FUra host toxicity. The efficiency of the BBBA plus TAU combination in rescuing from FUra host toxicities is attributed to the exceptional effectiveness of this combination in raising and maintaining higher plasma uridine concentrations than those achieved by TAU alone or by equimolar doses of uridine (Ashour et al., Biochem Pharmacol 51: 1601-1612, 1996). The present results suggest that the BBBA plus TAU combination can provide a better substitute for the massive doses of uridine required to achieve the high levels of uridine necessary to rescue or protect from FUra host toxicities without the toxic side-effects associated with such doses of uridine. The combination of TAU plus BBBA may also allow the escalation of FUra doses for better chemotherapeutic efficacy. Alternatively, the combination may be used as a rescue regimen in the occasional cases where cancer patients receive a lethal overdose of FUra.     

Biological activity of the potent uridine phosphorylase inhibitor 5-ethyl-2,2'-anhydrouridine

5-Ethyl-2,2'-anhydrouridine (ANEUR) proved to be a potent inhibitor of uridine phosphorylase isolated from sarcoma 180 cells with an apparent Ki (Ki(app) value of 99 nM. Coadministration of ANEUR with 5-fluorouridine (FUR) resulted in increased toxicity of FUR. The LD50 value of FUR alone was 9 mg/kg (when administered for 5 consecutive days) while the LD50 was 3 mg/kg when FUR was administered together with ANEUR in vivo. There was no significant difference in mean tumor weight on day 10 between control animals and animals treated with FUR (5 mg/kg/day for 3 days) or ANEUR (280 mg/kg/day for 3 days). When FUR was coadministered with ANEUR, mean tumor weight was 91% less than that of the untreated controls, showing that ANEUR, the potent URPase inhibitor, increases the antitumor effect of FUR.     

Retention of in vivo antipyrimidine effects of Brequinar sodium (DUP-785; NSC 368390) in murine liver, bone marrow and colon cancer

Brequinar sodium (DUP-785) is a potent inhibitor of the pyrimidine de novo enzyme, dihydroorotic acid dehydrogenase (DHO-DH). In order to determine whether in vitro data could be extrapolated to the in vivo situation we investigated antipyrimidine effects of DUP-785 in mice bearing colon cancer. Two tumor models were used, Colon 26 and Colon 38, resistant and moderately sensitive to DUP-785, respectively. DUP-785 at 50 mg/kg caused a depletion of plasma uridine in mice, and depleted tissue uridine levels in Colon 38 down to 10%, which was retained for several days; in Colon 26 the decrease was less and tissue uridine levels recovered rapidly. In livers of these mice no significant effect on uridine was observed. DUP-785 depleted UTP in bone marrow cells within 2 hr to 25% of control levels, after 4 days normal levels were found. In livers of both Balb-c mice (bearing Colon 26) and C57Bl/6 mice (bearing Colon 38) a small decrease of uridine nucleotide pools was found. In Colon 26 DUP-785 increased uridine nucleotide pools to 170% after 2 hr, at 1 day normal levels were observed, but after 2 days again an increase was found. In Colon 38 DUP-785 decreased the uridine nucleotide pool by 50% after 1 and 2 days. DUP-785 did not affect cytidine nucleotide pools of livers and of Colon 26 and Colon 38. The ratio between uridine nucleotides and cytidine nucleotides decreased from 2.2 to 0.90 in Colon 38, in the other tissues the decrease was less. DHO-DH was measured in bone marrow cells and Colon 26 and 38 before and after treatment. Basal levels of DHO-DH were 3 times higher in Colon 26 than in Colon 38. In treated tumors DHO-DH was initially inhibited by more than 90%, after 7 days enzyme activity in Colon 26 was 50% and in Colon 38 about 200% of basal levels. In bone marrow cells DHO-DH was also rapidly inhibited but recovered within 4 days. It is concluded that the retention of antipyrimidine effects of DUP-785 in Colon 38 were more pronounced than in Colon 26, which is in agreement with the better antitumor effect of DUP-785 in Colon 38.     

Modulation of fluorouracil antitumor activity by folic acid in a murine model system.

The biochemical basis for modulation of fluorouracil (FU) activity by leucovorin is elevation of the metabolite methylenetetrahydrofolate, which stabilizes the inhibitory ternary complex formed between thymidylate synthase and the active metabolite of FU, 5-fluorodeoxyuridylate. Folic acid, because it can also potentially be metabolized to methylenetetrahydrofolate, was evaluated for its ability to potentiate FU antitumor activity in a dietary folic acid restricted murine model. The plasma pharmacokinetics and tissue distribution of folic acid and all stable metabolites thereof were determined in the model to establish administration schedules. FU was administered to mice implanted subcutaneously with a mammary adenocarcinoma 4 hr after folic acid administration, when the metabolites, methylenetetrahydrofolate and tetrahydrofolate, were elevated maximally in both plasma and tumor tissue. While FU alone suppressed growth 25%, folic acid in combination with FU increased growth suppression to over 70%. These results indicate that folic acid is a potent modulator of FU activity and could be considered as an alternative to leucovorin in the clinical setting.     

Mitomycin C with weekly 24-h infusion of high-dose 5-fluorouracil and leucovorin in patients with biliary tract and periampullar carcinomas

We have reported a 33% partial response rate with acceptable toxicity using weekly 24-h infusion of high-dose 5-fluorouracil (5-FU) and leucovorin (LV) in patients with far advanced biliary tract cancers (BTC). In this study, we added mitomycin (MMC) to 5-FU and LV in an attempt to improve the response rate and survival. From July 1997 to September 1999, 25 chemotherapy-naive patients with pathology-proven far advanced BTC and periampullar cancers were enrolled. The regimen consisted of MMC 10 mg/m(2) every 8 weeks combined with 5-FU 2600 mg/m(2) and LV 150 mg at a schedule of 24-h infusion weekly for 6 weeks followed by a 2 week break. There were 10 males and 15 females with a median age of 57 years (range 40-76). The sites of primary tumor were 15 intrahepatic cholangiocarcinomas (CC), one perihilar CCs, three distal BTC, three gallbladder cancers (GB) and three periampullar cancers. A total of 148 sessions of chemotherapy were given with a mean of 8 (range 2-18). Nineteen patients were evaluable for response. The response rate was: 26% (five of 19) partial response, 42% (eight of 19) stable disease and 32% (six of 19) progressive disease. All of the patients were evaluable for toxicity. Toxicities more than grade III-IV were thrombocytopenia 16% (four of 25), leukopenia 12% (three of 25) and vomiting 4% (one of 25). There were four treatment-related deaths. The median time to disease progression was 3 months. The median survival was 6 months. A combination of MMC with weekly high-dose 5-FU and LV in patients with BTC did not improve the response rate, but produced more toxicity than weekly high-dose 5-FU and LV alone.     

Biweekly bolus 5-fluorouracil and leucovorin plus oxaliplatin in pretreated patients with advanced colorectal cancer: a dose-finding study

The primary objective of this study was to determine the maximum tolerable dose (MTD) and dose-limiting toxicity (DLT) for bolus 5-fluorouracil (5-FU) administered on a biweekly schedule and in combination with fixed doses of leucovorin (LV) and oxaliplatin. The secondary objectives were to evaluate the toxicity profile and antitumor activity of this regimen for pre-treated patients with advanced colorectal cancer. A total of 26 patients with documented fluoropyrimidine-resistant, advanced colorectal cancer were enrolled into this phase I study. Fixed dose of oxaliplatin (85 mg/m2) was delivered as an i.v. infusion over 2 h, followed by LV (20 mg/m2) and 5-FU bolus every 2 weeks. The starting dose of 5-FU was 600 mg/m2, which was then incremented by 100 mg/m2 for each dose level. The DLT was determined for the first two treatment cycles, while toxicity and efficacy were evaluated throughout treatment. Six dose levels were tested. The MTD of 5-FU was deemed to be 1000 mg/m2 since dose-limiting fatigue was noted for three of the five-patient cohort during the first two cycles of chemotherapy at dose level 6. The most frequent treatment-related toxicities during the study were neutropenia, vomiting, diarrhea, fatigue and neuropathy. In an intent-to-treat analysis, the objective response rate was 30.8% (95% confidence interval 11.8-49.8%) for the 26 patients. The combination of bolus 5-FU/LV and oxaliplatin every 2 weeks is a feasible and effective treatment at the recommended dosages. A phase II study, to more-precisely define activity and toxicity, is ongoing.     

Preclinical antitumor activity of 5-aza-2′-deoxycytidine agains human head and neck cancer xenografts

Summary The antitumor activity of 5-aza-2-deoxycytidine (5-aza-dCyd), a nucleoside analog, was established in human head and neck cancer xenografts, transplanted in nude mice. A significant response was noted in 3 of 5 lines, when the drug was injected intraperitoneally at a maximum tolerated dose of 2 mg/kg every four days for three doses. In two most sensitive lines 1 out of 6 tumors regressed completely. The antitumor activity of the drug may depend on the schedule used, as illustrated by the fact that just one of these two lines appeared to be sensitive when treated with low daily doses (0.25 mg/kg). One of the two sensitive lines also responded to the treatment with low daily doses (0.25 mg/kg). In two lines, 5-aza-dCyd showed equal or better antitumor activity when compared to the conventional drugs known to produce remissions in patients with head and neck cancer (cisplatin, methotrexate, bleomycin, 5-fluorouracil and cyclophosphamide). 5-Aza-dCyd is a drug with potential value in the chemotherapeutic treatment of patients with head and neck cancer.     

Phase II trial of uracil/tegafur (UFT) plus leucovorin in patients with advanced hepatocellular carcinoma

Although UFT 300 mg/m2/day and leucovorin 90 mg/day administered orally in divided doses administered every 8 hours for 28 days repeated every 35 days could be administered safely to patients with advanced hepatomas and good performance status, this combination and schedule has limited activity in treating advanced hepatoma.Background/purpose: Biochemical modulation of 5-fluorouracil has yielded higher response rates in hepatoma when compared to treatment with 5-fluorouracil as a single agent, although the impact on survival has been negligible. This study was conducted to determine the activity and evaluate the toxicity of uracil and tegafur in a 4:1 molar concentration ratio (UFT; Bristol-Myers Squibb, Wallingford, CT) plus oral calcium leucovorin in the treatment of patients with advanced hepatocellular carcinoma (hepatoma).Patients and methods: Sixteen patients with advanced measurable hepatocellular carcinoma were enrolled onto the trial. All patients had a Karnofski performance status 60%, platelet count 75,000/L, total bilirubin 2.0× institutional upper limit of normal but otherwise normal liver and kidney function profile and bidimensionally measurable disease by CT or ultrasound examination. None of these patients received prior cytotoxic chemotherapy or radiation therapy for advanced disease. Fourteen patients received 300 mg/m2/d UFT plus 90 mg/d leucovorin administered orally in divided daily doses every 8 hours for 28 days repeated every 35 days. Two patients registered for the trial but did not receive study medication. Objective tumor response, the primary purpose of this trial, was evaluated after two courses of therapy. Other end-points included toxicity, time to progression, and overall survival.Results: Fourteen patients were evaluable for response and toxicity, respectively. No complete or partial responders were observed in this trial. Three patients had stable disease lasting 17 to 22 weeks. Toxicity was mild with severe (grade 3 or 4) liver pain, diarrhea, anorexia/nausea, fatigue, dyspnea, hyperbilirubinemia, anemia, and edema seen in 3 (21%), 2 (14%), 3 (21%), 2 (14%), 1 (7%), 1 (7%), 1 (7%) and 1(7%) patients, respectively. The most frequent grade 1 and 2 toxic effects included fever of unknown origin, dyspnea, nausea, vomiting and diarrhea.Conclusion: UFT 300 mg/m2/d plus oral leucovorin 90 mg/d administered for 28 days did not demonstrate antitumor activity against advanced hepatomas. Further treatment using this regimen is not recommended for this disease.     

Aegle marmelos (L.) Correa inhibits the proliferation of transplanted Ehrlich ascites carcinoma in mice

The anticancer effect of hydroalcoholic extract of Aegle marmelos (AME) was studied in the Ehrlich ascites carcinoma bearing Swiss albino mice. The spatial effect of various AME administration schedules showed that six-day administration increased the survival of tumor bearing mice. The best antineoplastic action of AME was obtained when AME administered through intraperitoneal route than the oral route at equimolar dose. Administration of AME once daily for six consecutive days to the tumor bearing mice caused a dose dependent remission of the tumor at 400 mg/kg body weight, where the greatest antitumor effect was observed and the higher doses showed toxic manifestations. A 24-d lengthening in life span was observed in EAC animals treated with 400 mg/kg AME. This dose of 400 mg/kg was considered as the best dose, where the animals survived up to 43 d post-tumor-cell inoculation as against no survivors in the saline treated control group. The antitumor activity when tested for different schedules for triple administrations, the best effect was observed for 1-2-3, followed by 1-3-5 and 1-5-9 days, respectively. Stage specific evaluation of AME inhibited the increase in body weight gain in animals due to tumor development during early stages only. The AME treatment resulted in a dose dependent elevation in the median survival time (MST) and average survival time (AST) up to 400 mg/kg AME and decline thereafter. The effective dose of 400 mg of AME is 1/6th of the LD50 dose, which increased the MST and AST up to 29 and 27 d, respectively. The acute toxicity study of AME showed that the drug was non-toxic up to a dose of 1750 mg/kg b. wt. The LD10 and LD50 was found to be 2000 and 2250 mg/kg.     

A phase II pilot study of high-dose 24-hour continuous infusion of 5-FU and leucovorin and low-dose PALA for patients with colorectal cancer: A Southwest Oncology Group study

PURPOSE: The purpose of this phase II multi-institutional study was to define the efficacy and toxicity of infusional 5-FU in combination with PALA and leucovorin in patients with advanced colorectal cancer. PATIENTS AND METHODS: Patients were required to have histologically confirmed colorectal cancer with distant metastases. The treatment regimen consisted of 5-FU 2600 mg/m(2) as a 24-hours continuous infusion given once a week, concurrently with leucovorin (LV) at 500 mg/m(2) as a 24-hour continuous infusion. PALA was administered 24 hours prior to 5-FU/LV at a dose of 250 mg/m(2) iv over 15 minutes weekly. Patients were continued on the assigned treatment regimen until progression of disease, unacceptable toxicity, or the patient declined further therapy. RESULTS: This study accrued 28 patients and all were eligible and evaluable for toxicity. Four patients had inadequate assessment of response and are considered non-responders. There was one complete response and five partial responses for an overall response rate of 6/28 or 21% (95% confidence interval 8-41%). Estimated median survival was 17.4 months (95% confidence interval 13.3-20.5 months). One patient died of a treatment related infection. This patient also had grade 4 diarrhea and vomiting. CONCLUSION: The combination of 5-FU, leucovorin, and PALA in the doses and schedule used here, produces a response rate similar to other modulated schedules of 5-FU with similar survival and toxicity profiles.     

氧代赖氨酸与5—FU联合治疗肿瘤的实验研究

氧代赖氨酸(I-677)的抗肿瘤作用是由于影响蛋白质的生物合成,本文将它与一些已知的影响核酸代谢的抗肿瘤药物用于联合治疗。发现与5-FU合用时能提高疗效。单用氧代赖氨酸(400mg/kg)ip 2次,或5-FU(25m/kg)ip 3次,对肉瘤37无抑制作用,合用时则产生显著的抑制效果。     

雷公藤内酯醇联合5-氟尿嘧啶对结肠癌的作用研究

目的研究雷公藤内酯醇（TPL）与5-氟尿嘧啶（5-Fu）联合应用对结肠癌细胞增殖、凋亡及瘤体生长的影响并观察其在结肠癌化疗中的毒副作用。方法常规培养HT-29细胞，应用四甲基偶氮唑蓝比色法、流式细胞术检测TPL、5-FU联合应用对人结肠癌细胞增殖和凋亡的影响；中效原理评价两药的联合作用；建立裸鼠荷人结肠癌动物模型，分别及联合应用0．25mg／（kg·d）TPL和12mg／（kg·d）5-FU对其进行治疗，观察荷瘤裸鼠一般情况、瘤体的生长及化疗毒副作用。结果（1）TPL和5-FU分别及联合应用，在一定浓度范围内对结肠癌细胞有明显的增殖抑制和诱导凋亡作用，并且联合用药作用明显强于单独用药，48h凋亡率高达（41．71±1．38）％；（2）TPL和5-Fu单独应用均可抑制结肠癌瘤体的生长，肿瘤抑制率分别为78．53％、84．16％；2者联合应用时作用更为明显，肿瘤抑制率达96．78％；（3）整个化疗过程中除偶尔出现全身散在红斑、丘疹外，未见明显造血系统、肝肾功能损害等毒副作用。结论TPL与5-Fu联合应用比单独应用对结肠癌细胞株增殖抑制作用更强；TPL与5-FU在小剂量联合应用时协同抑制肿瘤细胞增殖，抑制瘤体生长，并能促进结肠癌细胞凋亡，在体外实验中毒副作用小。     

~(19)F体内核磁共振技术观测5-氟尿嘧啶在小鼠植入肿瘤中的摄取与代谢

应用体内１９ＦＮＭＲ谱观察并定量评价了５－氟尿嘧啶（５－ＦＵ）在荷Ｓ１８０瘤和Ｂ１６瘤小鼠肿瘤内的摄取和代谢动力学过程．５－ＦＵ２００ｍｇ·ｋｇ－１ｉｖ后，药物在Ｓ１８０和Ｂ１６瘤内的主要产物为其活性产物氟代核苷／核苷酸（ＦＮＵＣ），同时可检测到少量的降解产物α－氟－β－丙氨酸（ＦＢＡＬ）和α－氟－β－脲基丙酸（ＦＵＰＡ）．在Ｓ１８０瘤内，５－ＦＵ摄取，消除以及ＦＮＵＣ的生成有较大的个体变异，５－ＦＵ的消除半衰期ｔ１／２ｋｅ为４１．５－８４．８ｍｉｎ，ＦＮＵＣ生成ｔ１／２ｒ为２６．０－９１．９ｍｉｎ．当甲氨蝶呤（ＭＴＸ）与５－ＦＵ合用时，５－ＦＵ在Ｓ１８０瘤内的活化代谢过程明显加快，ｔ１／２ｋｅ缩短为２９．９－４３．４ｍｉｎ，ＦＮＵＣ的生成速率显著提高，生成量增加．５－ＦＵ在Ｂ１６瘤内的摄取及代谢过程的个体波动较小，其ｔ１／２ｋｅ为３９±５ｍｉｎ，ＦＮＵＣ的生成ｔ１／２ｒ为６０±７ｍｉｎ，在Ｂ１６瘤内，ＭＴＸ的合用不能明显加快５－ＦＵ转化为ＦＮＵＣ的反应，也不改变５－ＦＵ在瘤内的消除模式．上述结果表明，５－ＦＵ对肿瘤的化疗作用与肿瘤灌注５－ＦＵ在瘤组织内的摄取和活化代谢过程密切相关，亦可受到合用药物的影响．     

Modulation of high-dose methotrexate toxicity by a non-toxic level of 5-fluorouracil

High-dose methotrexate (MTX) toxicity is reduced by a non-toxic dose of 5-fluorouracil (FU) when these agents are used in combination. Changes in the hematopoietic system (platelets, erythrocytes, leukocytes, hemoglobin, and hematocrit), ileal tissue, body weight, and mean survival were used as parameters to assess toxicity. For all parameters studied, there were no significant differences between the scheduling of MTX (245 mg/kg) after a priming dose of FU (25 mg/kg), simultaneous MTX and FU, FU alone, and control. However, sequential treatment with MTX followed by FU, and MTX alone resulted in: a marked decrease in the hematopoietic parameters; significant morphological changes in ileal tissue; a reduction of body weight; and increased mortality of animals. Hence, this study suggests that FU, a cytotoxic agent, may protect against MTX toxicity and improve its therapeutic index when FU administration precedes MTX or when these agents are given simultaneously.     

Antitumor activity of N-phosphonacetyl-L-aspartic acid in combination with nitrobenzylthioinosine

N-Phosphonacetyl-L-aspartic acid (PALA) resistance may be due to the ability of tumor cells to utilize preformed circulating pyrimidine nucleosides, thereby overcoming the block of de novo pyrimidine biosynthesis which PALA causes. To test this hypothesis we examined the effects of PALA and nitrobenzylthioinosine (NBMPR) alone and in combination on B16 melanoma cells in vitro using a clonogenic assay and in vivo using growth delay. In medium containing purine and pyrimidine nucleosides at a final concentration of 28 microM, exposure to PALA (100 microM) alone or to NBMPR (10 microM) alone for periods up to 72 hr did not result in any cytotoxicity. However, exposures to PALA (100 microM) plus NBMPR (10 microM) resulted in a decrease in clonogenic survival to 0.011 at 72 hr. In medium without nucleosides, PALA (100 microM) exposure for 72 hr caused a similar decrease in survival to 0.015, whereas NBMPR (10 microM) had no effect on survival. The addition of uridine resulted in a concentration-dependent reversal of the cytotoxic effects of PALA. C57 Bl female mice bearing B16 melanoma were treated intraperitoneally daily for 4 days with PALA, the phosphate of NBMPR (NBMPR-P), or PALA plus NBMPR-P. PALA, 300 mg/kg daily X 4, resulted in a 6-day tumor growth delay but NBMPR-P, 100 mg/kg daily X 4, had no effect. PALA, 150 mg/kg daily X 4, plus NBMPR, 50 or 100 mg/kg daily X 4, resulted in a 6-day tumor growth delay also. These studies demonstrate that: (1) circulating pyrimidine nucleosides are determinants of the cytotoxic effects of PALA; (2) in vitro PALA and NBMPR combine to cause significant cytotoxicity whereas either agent alone has no effect; (3) in vivo the combination of PALA and NBMPR-P results in the same antitumor affect as PALA alone at twice the dose; and (4) due to an increase in animal toxicity, no therapeutic advantage could be demonstrated for the combination over PALA alone in vivo. We conclude that the cytotoxic effect of PALA is modulated by the levels of the preformed circulating nucleosides and that combining PALA with an inhibitor of salvage pyrimidine uptake would not increase the therapeutic efficacy of PALA because of an increase in toxicity.