Contradictory antitumor efficacies produced by the combination of DNA attacking drugs and polyamine antimetabolites

The antitumor effects of two polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), when combined with cis-diamminedichlroplatinum (CDDP) or mitomycin C (MMC), were studied using human gastric cancer cells xenotransplanted into nude mice. DFMO 1000 mg/kg and MGBG 50 mg/kg were given intraperitoneally for 6 successive days, while CDDP 3 mg/kg or MMC 2 mg/kg was given every second day. Although DFMO and MGBG plus MMC did suppress the tumor growth, the combination with CDDP led to no suppression, and rapid growth occurred after the cessation of therapy. The inhibition of tumoral DNA biosynthesis and a decline in polyamine levels, were also not observed. The polyamine antimetabolites when used with CDDP did not produce the desired antitumor efficacy, even though the platinum concentration in the tumor tissue was high. On the contrary, however, DFMO and MGBG when combined with MMC did suppress tumor growth, inhibited DNA biosynthesis, and tissue polyamine levels were low. These results suggest that though CDDP and MMC belong to a similar category of DNA attacking, bifunctional alkylating agents, the findings of these two drugs are contradictory. Here, the mechanism of action no doubt plays a contributory role.     

Contradictory antitumor efficacies produced by the combination of DNA attacking drugs and polyamine antimetabolites

The antitumor effects of two polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) and methylglyoxal-bis-guanylhydrazone (MGBG), when combined with cis-diamminedichlroplatinum (CDDP) or mitomycin C (MMC), were studied using human gastric cancer cells xenotransplanted into nude mice. DFMO 1000 mg/kg and MGBG 50 mg/kg were given intraperitoneally for 6 successive days, while CDDP 3 mg/kg or MMC 2 mg/kg was given every second day. Although DFMO and MGBG plus MMC did suppress the tumor growth, the combination with CDDP led to no suppression, and rapid growth occurred after the cessation of therapy. The inhibition of tumoral DNA biosynthesis and a decline in polyamine levels, were also not observed. The polyamine antimetabolites when used with CDDP did not produce the desired antitumor efficacy, even though the platinum concentration in the tumor tissue was high. On the contrary, however, DFMO and MGBG when combined with MMC did suppress tumor growth, inhibited DNA biosynthesis, and tissue polyamine levels were low. These results suggest that though CDDP and MMC belong to a similar category of DNA attacking, bifunctional alkylating agents, the findings of these two drugs are contradictory. Here, the mechanism of action no doubt plays a contributory role.     

Experimental chemo- and chemoendocrine therapy of human breast carcinomas serially transplanted into nude mice

Four human breast carcinoma strains serially transplanted into nude mice were used for the experimental chemotherapy and combination chemoendocrine therapy. Whereas three of these strains (MCF-7, Br-10, TM-61) possessed cytosol estrogen receptor (ERc) and were dependent on estradiol for the tumor growth, the other strain (MX-1) without ERc was hormone independent. For the chemotherapy, mitomycin C (MMC), adriamycin (ADM), cyclophosphamide (CPM) and 5-fluorouracil (5-FU) were administered 3 times every 4 days. To know the stability of ERc after chemotherapy, binding sites of ERc were measured 4 days after MMC administration at doses of 1, 2 and 4.5 mg/kg. For the chemoendocrine therapy, 1 or 2 mg/kg of MMC was administered once followed by treatment by tamoxifen (TAM). The effect of treatment was evaluated by T/C ratio of the tumor weight. MMC showed the most excellent antitumor effect and CPM and ADM showed a moderate effect. As ERc was found to be stable by MMC treatment, TAM was used after MMC, and this combination of MMC and TAM revealed an additive effect against ERc positive strains and no combination effect was observed in MX-1 without ERc. The dose response curves of 4 strains to MMC alone against 4 strains were made and the effect of combination chemoendocrine therapy was converted to the effect of MMC alone, showing the dose of MMC could be significantly reduced. Binding sites of ERc which were measured 4 days after MMC administration (1, 2 and 4.5 mg/kg) was found to be stable, suggesting TAM treatment after MMC might be reasonable. From these results, chemoendocrine therapy of MMC followed by TAM was considered to be beneficial modality for clinical treatment of the cytotoxic agent and increasing the antitumor effect.     

A novel anticancer treatment for xenoplanted human gastric cancer using polyamine antimetabolites in a low polyamine diet

The aim of the present study was to evaluate a new anticancer treatment for gastrointestinal cancer, using a combination of polyamine antimetabolites, an anticancer agent and a low-polyamine state. Two polyamine antimetabolites, given as either 40 mg/kg of methylglyoxal-bis-guanylhydrazone (MGBG) or ethylglyoxal-bis-guanylhydrazone (EGBG) and a normal diet (ND), or 20 mg/kg of each drug and a low polyamine diet (LPD), together with 1,000 mg/kg of alpha-difluoromethylornithine (DFMO) were administered ip to nude mice for six consecutive days. Mitomycin C (MMC) at 2 mg/kg was then given ip for 3 alternate days. The combination of MGBG or EGBG with DFMO plus MMC resulted in an enhanced antitumor efficacy on LPD. However, the combination which included EGBG was much more enhanced than that which included MGBG and there was no evidence of any tumor regrowth. Weight loss was minimal or nil in the mice given the combination with EGBG, but was evident in those given the combination with MGBG. These results led to the conclusion that in mice, the combined therapy of EGBG with DFMO plus MMC and LPD is a safe and effective regimen for the treatment of gastric cancer.     

A standardized method of using nude mice for the in vivo screening of antitumor drugs for human tumors

Human tumors transplanted into nude mice have long been used to assess the effectiveness of antitumor drugs and yet there is still no established standard method in preclinical practice for screening new antitumor drugs in vivo using nude mice. Thus, a cooperative study on the feasibility of a human tumor / nude mouse system for the in vivo screening of drugs was conducted by the Japanese Research Society for Chemosensitivity of Cancer. Two human stomach cancers, H-111 and SC-6-JCK, and one human colon cancer, Co-4, were transplanted serially into nude mice and used as gastrointestinal tract tumors with stable tumor growth. The appropriate dosage of six well-known antitumor drugs [mitomycin C (MMC), cyclophosphamide (CPA), nimustine hydrochloride 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU), cis-platinum (II) diaminodichloride (CDDP), adriamycin (ADM) and 5-fluorouracil (5-FU)] in human tumor-bearing nude mice was determined based on the maximum tolerance dose of the drug. The respective dosages were 6 mg/kg of MMC×1 (i.p.), 120 mg/kg of CPA×1 (i.p.), 30 mg/kg of ACNU×1 (i.p.), 8 mg/kg of CDDP×1 (i.p.), 8 mg/kg of ADM×1 (i.v.), and 50 mg/kg of 5-FU q4d×3 (i.p.). Three weeks after treatment, drug effectiveness was judged by the tumor growth inhibition rate. Treatment with these appropriate doses appeared to show the maximum effect of the respective drugs on the tumor-bearing nude mice. This standardized method using nude mice should contribute to the screening of new antitumor drugs against human tumors, especially those of the gastrointestinal tract. The antitumor activity of new drugs on human tumors in vivo may now be determined by comparison with that of well-known antitumor drugs on human tumor-bearing nude mice.Constituting The Japanese Research Society for Chemosensitivity of Cancer (JRSCC)Affiliated members of JRSCC (Chairman: Tatsuhei Kondo) are: NU; Nagoya University (Second department of Surgery) RIMDOU; Research Institute for Microbial Disease, Osaka University (Department of Surgery) KU; Keio University (Department of Surgery) RINMBHU; Research Institute for Nuclear Medicine and Biology, Hiroshima University (Department of Surgery) TH; Tenri Hospital (Thoracic Surgery) RITCTU; Research Institute for Tuberculosis and Cancer, Tohoku University (Department of Clinical Chemotherapy in Medicine)     

Combined therapy of polyamine antimetabolites and antitumor drugs for human gastric cancer xenotransplanted into nude mice

Antitumor therapies using polyamine antimetabolites combined with 1-(4-amino-2-methyl-5-pyrimidyl)methyl-3(2-chloroethyl)-3-nitrosourea (ACNU) or fluorinated pyrimidines for human gastric cancer xenotransplanted into nude mice were studied to determine inhibiting post-therapeutic regrowth of the tumor after cessation of antitumor treatments with polyamine antimetabolites alone. ACNU 20 mg/kg, fluorinated pyrimidine, 5-FU 52.8 mg/kg and 5'-deoxy-5-fluorouridine (5'-DFUR) 100 mg/kg as well as polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) 1000 mg/kg and methylglyoxal-bis-guanylhydrazone (MGBG) 50 mg/kg were given intraperitoneally for 5 successive days. When DFMO and MGBG were combined with ACNU, the post-therapeutic regrowth was definitely inhibited, while combined treatments with 5-FU or 5'-DFUR did not inhibit the regrowth. Post-therapeutic DNA biosynthesis was suppressed in mice given DFMO, MGBG plus ACNU. On the contrary, in mice treated with DFMO, MGBG plus 5-FU or 5'-DFUR, suppression of DNA biosynthesis was not observed. Tumor tissue spermine levels in the DFMO, MGBG plus 5-FU or 5'-DFUR group remained unchanged, compared to those in the DFMO + MGBG group. In mice given DFMO, MGBG plus ACNU, however, spermine levels were markedly depressed; and the ACNU alone depressed also the tissue spermine levels. These different results between nitrosourea and fluorinated pyrimidines may relate to mechanisms of action of these antitumor drugs.     

化疗药物对荷人胆管癌裸小鼠移植瘤的药效试验

目的：观察化疗药物对荷人胆管癌裸小鼠移植瘤的治疗效果。方法：采用人中分化胆管癌裸小鼠移植瘤模型。将45只荷人胆管癌裸小鼠分为各治疗组和对照组,裸小鼠治疗组每组5只,对照组10只。分组当天称鼠重,由尾静脉用药1次。给药剂量：丝裂霉素(MMC)4mg／kg,阿霉素(ADM)10mg／kg,长春新碱(VCR)0．20mg／kg,泰素(TAXOL)20mg/kg,顺铂(DDP)10mg／kg,环磷酰胺（CTX)120mg／kg,5-氟脲嘧啶(5-Fu)120mg/kg,NS为0．2mL／只。第21天处死裸小鼠,称鼠重,计算体重变化。治疗期间每周测肿瘤瘤径2次,计算相对肿瘤增殖率T／C(％)。结果：MMC,ADM,VCR,TAXOL,DDP和CTX组第21天相对肿瘤增殖率分别为：1％,23％,39％,47％,51％和86％,裸小鼠体重增加分别为：21％,0％,11％,1％,14％和8％。5-Fu组80％裸小鼠死亡,有药物毒性反应。结论：MMC,ADM,VCR,TAXOL,DDP对荷人中分化胆管癌裸小鼠的移植瘤有明显的抗癌作用,CTX无效。     

Combined therapy of polyamine antimetabolites and antitumor drugs for human gastric cancer xenotransplanted into nude mice

Antitumor therapies using polyamine antimetabolites combined with 1-(4-amino-2-methyl-5-pyrimidyl)methyl-3(2-chloroethyl)-3-nitrosourea (ACNU) or fluorinated pyrimidines for human gastric cancer xenotransplanted into nude mice were studied to determine inhibiting post-therapeutic regrowth of the tumor after cessation of antitumor treatments with polyamine antimetabolites alone. ACNU 20 mg/kg, fluorinated pyrimidine, 5-FU 52.8 mg/kg and 5′-deoxy-5-fluorouridine (5′-DFUR) 100 mg/kg as well as polyamine antimetabolites, alpha-difluoromethylornithine (DFMO) 1000 mg/kg and methylglyoxal-bis-guanylhydrazone (MGBG) 50 mg/kg were given intraperitoneally for 5 successive days. When DFMO and MGBG were combined with ACNU, the post-therapeutic regrowth was definitely inhibited, while combined treatments with 5-FU or 5′-DFUR did not inhibit the regrowth. Post-therapeutic DNA biosynthesis was suppressed in mice given DFMO, MGBG plus ACNU. On the contrary, in mice treated with DFMO, MGBG plus 5-FU or 5′-DFUR, suppression of DNA biosynthesis was not observed. Tumor tissue spermine levels in the DFMO, MGBG plus 5-FU or 5′-DFUR group remained unchanged, compared to those in the DFMO + MGBG group. In mice given DFMO, MGBG plus ACNU, however, spermine levels were markedly depressed; and the ACNU alone depressed also the tissue spermine levels. These different results between nitrosourea and fluorinated pyrimidines may relate to mechanisms of action of these antitumor drugs.     

Therapy of prostate carcinoma with polyamine synthesis inhibitors. I. Physiological and pathophysiological principles

The therapeutic concept of irreversible inhibition of both ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC) by alpha-difluoromethylornithine (DFMO) and methylglyoxal bis-guanylhydrazone (MGBG) is based on pathologic activities of these enzymes in tumor tissue. The polyamines putrescine, spermidine and spermine are measured in highest concentration in the prostate of both men and animals, with a significant increase of spermine in benign hyperplasia of the prostate. Patients with metastatic cancer of the prostate have elevated putrescine levels in the 24-hour urine. Treatment with 3 or 1% DFMO or 11 mg/kg MGBG in transplantable human and experimental cancer of the prostate demonstrated a significant anti-growth effect. A combination of DFMO and MGBG is tumor-destructive. The combination of 1% DFMO and 11 mg/kg MGBG distinctly reduces the activity of ODC and SAMDC and significantly lowers the levels of putrescine, spermidine and spermine in the tumor.     

Ornithine decarboxylase activity and polyamine levels in human thyroid tumor tissue

Production of polyamines such as putrescine (PUT), spermidine (SPD) and spermine (SPM) primarily from ornithine by ornithine decarboxylase (ODC) is correlated with cell proliferation. Polyamine levels and ODC activities were measured to determine the degree of biological malignancy in 186 thyroid tumor tissues. Carcinoma showed significantly higher ODC activity and higher levels of PUT, SPD and SPM than benign tumors. PUT levels showed 2.28 nmol/mg protein in anaplastic carcinoma, 0.66 in papillary carcinoma, 0.11 in follicular adenoma, 0.06 in adenomatous goiter and 0.04 in normal thyroid tissue. Anaplastic and papillary carcinomas showed higher PUT/SPD and SPD/SPM ratios than benign tumors. Poorly differentiated carcinoma showed significantly higher PUT level and PUT/SPD and SPD/SPM ratios than well differentiated carcinoma. No correlation was found among polyamine levels, ages and sex in papillary carcinoma. In female patients with papillary carcinoma, no significant difference in polyamine levels was observed between patients above and below 50 years old. These results suggest that ODC activity and polyamine levels may provide useful information to determine the degree of biological malignancy of thyroid tumors.     

Sensitivity of anticancer agents on human gastric cancers transplanted into nude mice

In the chemotherapy for gastric cancer, the most sensitive anticancer agent against individual tumors should be prescribed. The establishment of a sensitivity test using nude mice as anin vivo model is urgently awaited by clinicians and researchers alike. Seventy-three tumors derived from human gastric cancer were transplanted subcutaneously into nude mice and these mice were then treated intraperitoneally with anticancer agents. Mitomycin C (MMC), 5-fluorouracil (5-FU) and cyclophosphamide (CPM) were used. The doses given were 3 mg/kg of MMC, 75 mg/kg of 5-FU and 200 mg/kg of CPM. In 52 of the 73 cancers, chemosensitivity was evaluated by the microscopic changes in the tumors. The rate of positive sensitivity against gastric cancer was 44.2% in MMC, 34.6% in 5-FU and 30.8% in CPM, respectively. The sensitivity of each agent tested by this method indicated a good correlation with the clinical therapeutic effects. Our results suggest the feasibility of evaluation of the sensitivity of various agents from the microscopic changes on tumors transplanted into nude mice.     

Interferon alpha-2a shows antitumor activity in combination with 5-fluorouracil against human colon carcinoma xenografts: A study in reference to thymidylate synthetase activity inhibition

To clarify the mode of antitumor activity shown by a combination of recombinant human interferon alpha-2a (IFN) and 5-fluorouracil (5-FU), experimental therapy was performed on human colon carcinoma (Co-4) xenografts serially transplanted into nude mice, using IFN and 5-FU, either alone or in combination. IFN alone showed dose-dependent antitumor activity and 5-FU also revealed a moderate antitumor effect. Although IFN, given as 600,000 units/mouse daily sc×14, and 5-FU, given as 60 mg/kg q4d×3 ip, showed additive antitumor activity against Co-4, the thymidylate synthetase (TS) inhibition rate was unchanged in the tumors treated with the IFN/5-FU combination in comparison with those treated with 5-FU alone. This suggests that the antitumor activity of IFN and 5-FU in combination does not involve augmentation of the TS inhibition by 5-FU.     

Antitumor Effect of Irinotecan Hydrochloride (CPT-11) on Human Renal Tumors Heterotransplanted in Nude Mice

Background : There has been a paucity of antitumor drugs that are active against renal tumors. Irinotecan hydrochloride (CPT-11), a DNA topoisomerase type 1 inhibitor, has demonstrated antitumor activity against human tumors, however, no antitumor effect of CPT-11 on renal tumors has been reported. The antitumor effect of CPT-11 was investigated on 2 human renal tumors (OUR-10 and OUR-20) heterotransplanted into nude mice.
Methods : Tumor-bearing nude mice were given daily intraperitoneal injections of multiple anticancer drugs suspended in 0.2 ml_ of phosphate-buffered saline (PBS) 3 times at 3-day intervals. Control mice were injected with 0.2 mL of PBS. The antitumor effects were evaluated by calculating the T/C ratio (treated tumors/controls) of the tumor volume.
Results : Among the 10 anticancer drugs tested, 50 mg/kg of CPT-11 showed an active antitumor effect on OUR-20 (T/C ratio 34). However, all drugs tested on OUR-10 failed to show antitumor activity. Conclusion: Since CPT-11 was effective in 1 of 2 renal tumors examined without severe toxicity, this drug could be a candidate for chemotherapy of renal cell carcinoma.     

Combined cytotoxic and endocrine therapy for human breast carcinoma (Br-10) serially transplanted into nude mice

Cytotoxic and endocrine therapy on a human breast carcinoma (Br-10) serially transplanted into nude mice was given with reference to the sequence of drug administration. Mitomycin C (MMC) was combined with 2.5 mg/kg of tamoxifen (TAM). MMC was dissolved in 0.2 ml of physiological saline and administered intraperitoneally once weekly. TAM was dissolved in 0.1 ml of sesame oil and administered intramuscularly twice weekly. Both drugs were administered in the reverse sequence for 2 or 3 weeks. Cytosol estrogen receptor (ERc), nuclear estrogen receptor (ERn) and progesterone receptor (PgR), and³H-thymidine uptake labeling index (L.I.) were assayed after the treatment. When 1.5 mg/kg of MMC was combined with TAM, statistically significant differences were nil between the different sequential administrations. When the MMC administration was reduced to 0.75 mg/kg and 2 weeks, respectively, the MMC→TAM sequence was more effective than the reversed sequential administration. MMC preserved ERc and depressed L.I. to almost half of that of the control tumor. TAM generated the ER systems and slightly depressed L.I. These different modes of action between MMC and TAM on ER systems and L.I. may explain the antitumor effects of different sequential administrations.     

Experimental and clinical studies on a sensitivity test of anticancer agents by 3H-thymidine autoradiography using a human malignant tumor transplanted to nude mice

The 3H-thymidine uptake of human xenografts transplanted in nude mice and treated with various anticancer agents was studied by autoradiography and compared with the histological changes on the same specimen. One hundred and four human malignant tumors were transplanted into nude mice and treated with intraperitoneal administration of Mitomycin C (MMC) (3mg/kg), 5-Fluorouracil (5-FU) (25mg/kg X 3) and Cyclophosphamide (CPM) (80mg/kg), of which 97 cases were investigated. Autoradiographical evaluation was expressed as the inhibition rate of labeling index of the treated specimen in comparison with that of the control. Histological change was judged by Ohboshi and Shimosato's criteria. The rate of positive sensitivity was 65.5% in MMC, 34.9% in 5-FU and 51.8% in CPM by autoradiographical evaluation, while by histological evaluation 18.9%, 14.6% and 16.9%, respectively. From these results, it may be speculated that the autoradiographical evaluation of the tumor sensitivity against anticancer agents is more sensitive than the histological evaluation. As to MMC and CPM, statistically significant correlations were demonstrated between the results of this method and those of the experimental chemotherapy in accordance with the Battelle Columbus Laboratories Protocol using human malignant tumors serially transplanted into nude mice.     

The mechanism of hepatoprotection by epsilon aminocaproic acid and putrescine

Hepatic neutral serine proteases (including plasminogen activator) and ornithine decarboxylase (ODC) are induced by the hepatotoxin galactosamine (GALN). We examined the hepatoprotection conferred by epsilon-aminocaproic acid (EACA), a fibrinolytic inhibitor, putrescine (PUTR), the polyamine generated from ornithine by ODC, and alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. GALN, 450 mg/kg, was administered intraperitoneally to Wistar-Lewis rats (group I). Groups II, III, and IV were also given EACA (80 mg/kg), PUTR (0.3 mmol/kg), or DFMO (0.3 mmol/kg), respectively, 1 hour before and 3, 7, and 12 hours after GALN. Rats were killed 2 hours after an intraperitoneal dose of 3H-thymidine was administered, 30 or 45 hours after GALN. EACA and PUTR were effective protectants against necrosis as judged by enzymes and histologic findings. Neither increased thymidine incorporation above the levels seen with GALN only. DFMO offered no protection even though thymidine incorporation at 45 hours was increased. Both EACA and PUTR, which have similar chemical structures, possessed significant antiprotease activity in vitro, suggesting that they act by inhibiting toxin-induced neutral serine protease activity and not by accelerating regeneration.     

Effect of difluoromethylornithine on host and tumor polyamine metabolism during total parenteral nutrition

Clinical and experimental data suggest that erythrocyte (RBC) polyamine (PA) levels are markers of tumor proliferation during total parenteral nutrition (TPN). The purpose of this experiment was to determine whether the inhibition of PA synthesis during TPN was greater in tumors than in normal host tissue. Rats bearing a subcutaneous fibrosarcoma were randomized to receive a chow diet (n = 5), TPN (n = 5), or TPN + difluoromethylornithine (DFMO) (an irreversible inhibitor of ornithine decarboxylase (ODC), at 1000 mg/kg body wt/day n = 4) for 6 days by continuous central venous infusion. TPN + DFMO resulted in a higher plasma albumin level and lower tumor ODC activity compared with chow feeding or TPN. Liver ODC activity was similar for the chow fed, TPN, and TPN + DFMO groups. RBC putrescine, tumor putrescine, and tumor spermidine levels were significantly lower in the TPN + DFMO group compared with the chow fed and TPN groups. RBC spermidine, RBC spermine, and tumor spermine levels were significantly increased with TPN + DFMO compared with TPN alone. DFMO did not produce diarrhea or weight loss. Increased RBC spermidine may indicate a toxic effect of DFMO on the tumor, resulting in leakage of tumor spermidine into the extracellular space. The data suggest that DFMO during TPN can selectively inhibit tumor PA synthesis and may improve host utilization of nutrients.     

Experimental combination chemo-radiotherapy on human breast carcinoma (MX-1) transplanted into nude mice

Experimental combination chemo-radiotherapy of mitomycin C (MMC) and Linac irradiation was performed on human breast carcinoma transplanted into nude mice. The treatment was started on 2 wks. after tumor inoculations and the effects were evaluated by T/C ratio of the tumor weight. Cell kinetic analysis was studied by flow cytometry, 3H-thymidine uptake labeling index (L.I.) and mitotic index (M.I.) on 24 hrs. after treatments. Effect of MMC (0.5, 1 and 2 mg/kg) and irradiation (500, 1000 and 2000 rads/mouse) revealed exponential linear dose response curves against T/C ratio which was significantly correlated with L.I. In combination therapy, the synergistic action was observed when 500 rads/mouse and 1 mg/kg were combined, and the effect was found to be more excellent when the radiation was performed 24 hrs. before MMC administration than the reversed sequence. By MMC and radiation, 2n and 3n cells increased with decrease of 4n cells. Whereas no change of M.I. was observed, L.I. was depressed. Increased 3n cells with depressed L.I. was supposed to be caused by S phase prolongation. As this change was more remarkable by radiation, the combination therapy was thought to be more effective when the radiation was performed before MMC administration. This nude mice-human tumor system was thought to be useful to analyze the combination chemoradiotherapy.     

Novel therapy for the treatment of human carcinoid.

Development of effective treatment for patients with carcinoid tumors has been hampered by lack of an experimental model. The authors have established the only long-term cell line of a functioning human pancreatic carcinoid tumor (BON) that produces tumors in nude mice. In this study the authors examined the effect of three agents, alpha-interferon (IFN), a somatostatin analog, SMS 201-995 (SMS), and an inhibitor of polyamine biosynthesis, alpha-difluoromethylornithine (DFMO), on the growth of BON tumors. BON was implanted bilaterally as 3-mm2 pieces (subcutaneously [sc]) into male BALB/c nude mice. In the first study, 23 mice were randomized to four groups: control, IFN (1 x 10(6) units, sc, four times a day), IFN + SMS (300 micrograms/kg, intraperitoneally, three times a day), and IFN + 3% DFMO in drinking water. Treatments were initiated on day of tumor implantation. In the second study, mice were randomized to six groups: control, IFN, SMS, DFMO, IFN + SMS, IFN + DFMO, and IFN + SMS + DFMO. Treatments were started on day 15 after tumor implantation. Tumor area and body weights were measured weekly. In both studies mice were killed on day 28 after BON implantation and tumors removed, weighed, and analyzed for DNA and RNA content. In the first study, IFN either alone or in combination with SMS or DFMO suppressed BON tumor growth. When treatment was initiated after established tumor growth (study 2), however, the only effective treatments for suppression of growth of BON were IFN + DFMO and IFN + DFMO + SMS.(ABSTRACT TRUNCATED AT 250 WORDS)     

The modulation by L-leucovorin of 5-fluorouracil antitumor activity on human colon carcinoma cells in vitro and in vivo

We investigated the modulating effect of L-leucovorin (LV) on the antitumor effect of 5-fluorouracil (5-FU) against human colon carcinoma cells (C-1) in vitro and human colon carcinoma xenografts (Co-4) in nude mice. The modulating effect of LV on 5-FU reached an optimal concentration of 40–80 g/ml in vitro which was detected by a colorimetric MTT assay. An optimal dose of 200 mg/kg was also observed in the nude mouse system. The modulating effect of LV increased according to the increment of thymidylate synthetase inhibition in vivo. Since the pharmacokinetic pattern of LV in the nude mice administered LV at 200 mg/kg was similar to that in patients treated with LV at a dose of 100 mg/m², this clinical method of administration was thought to be adequate for modulating the antitumor activity of 5-FU against clinical colon carcinomas.