Chronic exendin-4 treatment prevents the development of cancer cachexia symptoms in male rats bearing the Yoshida sarcoma

Cancer cachexia is the syndrome of weight loss, loss of appetite, and wasting of skeletal muscle and adipose tissue experienced by many individuals with cancer. Currently, few effective treatment and prevention strategies are available for these patients, due in part to a poor understanding of the mechanisms contributing to cachexia. Insulin resistance has been associated with cancer cachexia in epidemiological, human, and animal research. The present experiment was designed to examine the ability of Exendin-4, a GLP-1 agonist and insulin sensitizing agent, to prevent the development of cachexia symptoms in male Sprague Dawley rats bearing the Yoshida sarcoma. Following tumor implantation or sham surgery, rats were treated daily with saline or Exendin-4 (3 μg/kg body weight/day) and were monitored for tumor growth and cachexia symptoms for 21-23 days. As a result of large variability in treatment effects, data were analyzed separately for animals with large and small tumors. Exendin-4 treatment reduced tumor growth and prevented the development of cancer cachexia symptoms in animals with small, but not large, tumors. In addition, insulin levels were preserved in Exendin-4-treated tumor-bearing animals. The results of this experiment demonstrate a novel preventative therapy for cancer cachexia and a novel use of Exendin-4. Further research is necessary to determine the mechanisms through which Exendin-4 exerts these potent effects.

[Antitumor activity and function of S-1, a new oral tegafur-based formulation]

TS-1 (S-1), developed by the scientific theory of both potentiating antitumor activity of 5-fluorouracil (5-FU) and reducing gastrointestinal toxicity induced by 5-FU, is a new oral formulation consisting of 1 M tegafur, 0.4 M gimeracil and 1 M oteracil potassium. We investigated the antitumor efficacy of S-1 alone and in combination with other cytotoxic anticancer drugs using subcutaneously or orthotopically implanted murine and human tumors in rodents. As a single agent, S-1 showed higher antitumor activity with its low intestinal toxicity compared to continuous venous infusion 5-FU, the most effective dosing method of 5-FU, and/or to clinically available oral fluoropyrimidines such as UFT, doxyfluridine and capecitabine on various murine tumors and human tumor xenografts. Especially, it was noteworthy that S-1 as a DPD-inhibitory fluoropyrimidine markedly affected human tumor xenografts with high expression levels of DPD on which other fluoropyrimidines showed a low antitumor activity. In combination with other anticancer drugs such as CPT-11 and taxanes, S-1 exercised synergistic antitumor efficacy not only on 5-FU-sensitive tumors with low expression levels of thymidylate synthase (TS) but also on 5-FU-resistant tumors with originally higher and/or elevated levels of TS expression. As one of the reasonable mechanism of antitumor synergism by the combination, CPT-11 and taxanes were found to reduce the expression of TS in human tumor resistant to 5-FU with high expression TS levels. Throughout our preclinical antitumor studies of S-1, alone and/or in combination with other anticancer drugs, it would be expected to contribute greatly to the treatment of cancer patients.

Preliminary study of the optimal dosing schedule for oral UFT/leucovorin chemotherapy

BACKGROUND

We evaluated the optimal dosage schedule for combined oral chemotherapy using uracil/tegafur (UFT) and leucovorin (LV) in Yoshida sarcoma-bearing rats.

MATERIALS AND METHODS

The antitumor activity and survival effect were compared between two schedules, thrice daily administration on 5 days of the week followed by 2 drug-free days (schedule A) and twice daily on 7 days of the week (schedule B).

RESULTS

Significant tumor growth inhibition and improved survival rate were seen with both schedules of the UFT/LV group as compared to their respective control groups. Tumor growth inhibition was significantly greater in schedule A than schedule B. The number of survivors on day 60 after the tumor inoculation was higher in schedule A although the survival rate did not differ significantly.

CONCLUSION

Administration of UFT/LV for 5 days of the week seemed to exhibit superior antitumor activity, with no increase in the incidence of adverse effects, as compared with the consecutive daily dosing schedule.

A Comparative Pharmacology Study Between the Intracolonic and Oral Routes of 5-FU Administration in a Colon Cancer-Bearing Yoshida Sarcoma Rat Model

We prepared a colon cancer-bearing Yoshida sarcoma rat model to examine the dose-response relationship of antitumor activity of intracolonically or orally administered 5-fluorouracil (5-FU; 45, 30, 20, 13, and 8 mg/kg). At doses of > or =20 mg/kg and > or =30 mg/kg, the 5-FU intracolonic and oral administration groups each showed a statistically significant difference in antitumor activity against the control group (P<0.05, Williams' test). A statistically significant dose-response relationship was noted in the two routes of administration, with an ED(50) value of 29 mg/kg. White blood cell count tended to decrease at high doses when 5-FU was administered intracolonically and showed a statistically significant decrease at doses of > or =30 mg/kg when 5-FU was administered orally. Regarding the time-course of body weight, even the 5-FU highest dose (45 mg/kg) intracolonic administration group showed no inhibited body weight increase compared to the control group. However, the 5-FU (> or =20 mg/kg) oral administration groups showed a statistically significant difference in body weight increase against the control group. These facts suggested that the intracolonic administration of 5-FU, while exhibiting more potent antitumor activity than that observed in oral administration, allows an extensive reduction in its toxicities compared to oral administration.

Inhibition of induced chemoresistance by cotreatment with (E)-5-(2-bromovinyl)-2'-deoxyuridine (RP101)

Induced chemoresistance leads to the reduction of apoptotic responses. Although several drugs are in development that circumvent or decrease existing chemoresistance, none has the potential to prevent or reduce its induction. Here, we present data from a drug that could perhaps fill this gap. Cotreatment of chemotherapy with (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU, RP101) prevented the decrease of apoptotic effects during the course of chemotherapy and reduced nonspecific toxicity. Amplification of chemoresistance genes (Mdr1 and Dhfr) and overexpression of gene products involved in proliferation (DDX1) or DNA repair (UBE2N and APEX) were inhibited, whereas activity of NAD(P)H: quinone oxidoreductase 1 (NQO1) was enhanced. During recovery, when treatment was with BVDU only, microfilamental proteins were up-regulated, and proteins involved in ATP generation or cell survival (STAT3 and JUN-D) were down-regulated. That way, in three different rat tumor models, the antitumor efficiency of chemotherapy was optimized, and toxic side effects were reduced. Because of these beneficial properties of BVDU, a clinical pilot Phase I/II study with five human tumor entities has been started at the University of Dresden (Dresden, Germany). So far, no unwanted side effects have been observed.

Effects of the phosphodiesterase-IV inhibitor EMD 95832/3 on tumour growth and cachexia in rats bearing the Yoshida AH-130 ascites hepatoma

Administration of the phosphodiesterase-IV inhibitor EMD 95832/3 (Merck KGaA, Darmstadt, Germany) to rats bearing the ascites hepatoma Yoshida AH-130, a highly cachectic tumour, could not prevent either the anorexia nor the massive weight loss (affecting both adipose and skeletal muscle tissues) present in the tumour-bearing animals. This compound did not have any effects on the fractional rates of protein turnover in skeletal muscle, and did not affect circulating triacylglycerols or lipoprotein lipase activity in adipose tissue. Although the administration of EMD 95832/3 did not influence tumour growth either, it did increase the number of tumour cells undergoing apoptosis. It is concluded that the drug is unable to reverse the cachectic state in this particular experimental tumour model.

A novel combretastatin A-4 derivative, AC7700, strongly stanches tumour blood flow and inhibits growth of tumours developing in various tissues and organs

In a previous study, we used subcutaneous LY80 tumours (a subline of Yoshida sarcoma), Sato lung carcinoma, and methylcholanthrene-induced primary tumours, to demonstrate that a novel water-soluble combretastatin A-4 derivative, AC7700, abruptly and irreversibly stopped tumour blood flow. As a result of this interrupted supply of nutrients, extensive necrosis was induced within the tumour. In the present study, we investigated whether AC7700 acts in the same way against solid tumours growing in the liver, stomach, kidney, muscle, and lymph nodes. Tumour blood flow and the change in tumour blood flow induced by AC7700 were measured by the hydrogen clearance method. In a model of cancer chemotherapy against metastases, LY80 cells (2x10(6)) were injected into the lateral tail vein, and AC7700 at 10 mg x kg(-1) was injected i.v. five times at intervals of 2 days, starting on day 7 after tumour cell injection. The number and size of tumours were compared with those in the control group. The change in tumour blood flow and the therapeutic effect of AC7700 on microtumours were observed directly by using Sato lung carcinoma implanted in a rat transparent chamber. AC7700 caused a marked decrease in the tumour blood flow of all LY80 tumours developing in various tissues and organs and growth of all tumours including lymph node metastases and microtumours was inhibited. In every tumour, tumour blood flow began to decrease immediately after AC7700 administration and reached a minimum at approximately 30 min after injection. In many tumour capillaries, blood flow completely stopped within 3 min after AC7700 administration. These results demonstrate that AC7700 is effective for tumours growing in various tissues and organs and for metastases. We conclude that tumour blood flow stanching induced by AC7700 may become an effective therapeutic strategy for all cancers, including refractory cancers because the therapeutic effect is independent of tumour site and specific type of cancer.

[Cytotoxicity of beta-lapachone, an naphthoquinone with possible therapeutic use]

beta-lapachone (beta-lap) is a lipophilic o-naphthoquinone isolated from the bark of the lapacho tree. Initial observations proved its capability for inhibiting growth of Yoshida tumor and Walker 256 carcinosarcoma. beta-Lap redox-cycling in the presence of reductants and oxygen yields "reactive oxygen species" (ROS: O2-, OH and H2O2) which cytotoxicity led to assume its role in beta-lap activity in cells. beta-Lap inhibited DNA synthesis in Trypanosoma cruzi as well as topoisomerases I and II, poly(ADP-ribose) polymerase (PARP) in different cells. These enzymes are essential for maintaining DNA structure. beta-Lap inhibited growth of a large variety of tumor cells including epidermoid laringeal cancer, prostate, colon, ovary and breast cancer and also different types of leukemia cells. Advances in knowledge of apoptosis ("programmed cell death") and necrosis provided useful information for understanding the mechanism of beta-lap cytotoxicity. Thiol-dependent proteases (Calpaine), kinases (e.g. c-JUN NH2-terminal kinase), caspases and nucleases are involved in beta-lap cytotoxicity. These enzymes activity, as well as ROS production by beta-lap redox-cycling, would be essential for beta-lap cytotoxicity. Diaphorase and NAD(P)H-quinone reductase, which catalyse beta-lap redox-cycling and ROS production, seem to play an essential role in beta-lap activity. On these grounds, clinical applications of beta-lap have been suggested.

D-24851, a novel synthetic microtubule inhibitor, exerts curative antitumoral activity in vivo, shows efficacy toward multidrug-resistant tumor cells, and lacks neurotoxicity

N-(pyridin-4-yl)-[1-(4-chlorbenzyl)-indol-3-yl]-glyoxyl-amid (D-24851) is a novel synthetic compound that was identified in a cell-based screening assay to discover cytotoxic drugs. D-24851 destabilizes microtubules and blocks cell cycle transition specifically at G2-M phase. The binding site of D-24851 does not overlap with the tubulin binding sites of known microtubule-destabilizing agents like vincristine or colchicine. In vitro, D-24851 has potent cytotoxic activity toward a panel of established human tumor cell lines including SKOV3 ovarian cancer, U87 glioblastoma, and ASPC-1 pancreatic cancer cells. In vivo, oral D-24851 treatment induced complete tumor regressions (cures) in rats bearing Yoshida AH13 sarcomas. Of importance is that the administration of curative doses of D-24851 to the animals revealed no systemic toxicity in terms of body weight loss and neurotoxicity in contrast to the administration of paclitaxel or vincristine. Interestingly, multidrug-resistant cell lines generated by vincristine-driven selection or transfection with the Mr 170,000 P-glycoprotein encoding cDNA were rendered resistant toward paclitaxel, vincristine, or doxorubicin but not towards D-24851 when compared with the parental cells. Because of its synthetic nature, its oral applicability, its potent in vitro and in vivo antitumoral activity, its efficacy against multidrug-resistant tumors, and the lack of neurotoxicity, D-24851 may have significant potential for the treatment of various malignancies.

Effect of consecutive lower-dose cisplatin in enhancement of 5-fluorouracil cytotoxicity in experimental tumor cells in vivo

It is known that cisplatin (CDDP) potentiates the cytotoxicity of 5-fluorouracil (5-FU), and that the biochemical mechanism is an increase in the intracellular reduced folate levels in the tumor cells. We investigated the effect of consecutive administration with lower-dose CDDP on intracellular accumulation of reduced folate and the activity of methionine synthase, a key enzyme in intracellular methionine synthesis. When CDDP (1 mg/kg) was administered i.p. to ascitic Yoshida sarcoma-bearing rats for 4 consecutive days, both the reduced folate levels and methionine synthase activity in the cells significantly increased, as the same as a single 5 mg/kg dose of CDDP. Furthermore, when Yoshida sarcoma-bearing rats were pre-treated with 1 mg/kg CDDP for 5 consecutive days, [14C]L-methionine incorporation into the isolated ascitic cells was significantly inhibited as compared to that in non-treated cells, suggesting that consecutive administration of lower-dose CDDP is capable of inducing the intracellular modulation of reduced folate levels and methionine synthase activity via inhibition of cellular uptake of methionine. In addition, 5-day administration of lower-dose (1 mg/kg) CDDP potentiated the antitumor effect of 5 mg/kg S-1, a new oral preparation of tegafur, given for 7 consecutive days, and this combined effect was almost similar to the antitumor effect of a combination of S-1 and a single conventional dose (5 mg/kg) of CDDP. Consecutive lower-dose CDDP also may be concluded to act as an important modulator of the enhancement of 5-FU cytotoxicity in experimental tumors.

Tempicol-3, a novel piperidine-N-oxide stable radical and antioxidant, with low toxicity acts as apoptosis inducer and cell proliferation modifier of Yoshida Sarcoma cells in vivo

The novel nitroxyl, Tempicol-3 (nitroxide-N-oxide) was synthesized and its capacity to act as a scavenger of hydroxyl radicals was tested. The concentration-dependent reducibility of this novel compound was also examined and compared with those of previously characterized nitroxides, Tempo and Tempace. The cytotoxicity of Tempicol-3 in vitro was measured by the modified tetrazolium assay (MTT), using, model cells for neoplastic phenotype (mouse NIH 3T3 fibroblast line). The ability of Tempicol-3 to act as an antitumor agent in vivo was also investigated in a pharmacological test, using rats bearing 3-day old Yoshida Sarcoma (promotion phase of the disease). Our results clearly indicated that Tempicol-3 acts as an effective and promising hydroxyl radical scavenger-antioxidant. Structure- and concentration-dependent bioreduction of Tempicol-3 by ascorbic acid may account for some of its biological effects, causing modulation of the antioxidant status of cells. The presence of one nitrone moiety per molecule of Tempicol-3 caused a significant decrease in nitroxide cytotoxicity as compared with Tempo, in vitro. The results clearly confirmed that the toxic effect could result either from the presence or structure of substituent(s) at position 4 of the free radical piperidine moiety. It can be stated that Tempicol-3 is a lowtoxicity nitroxide, which could be effective in providing antioxidative activity. We have also observed that lowtoxic Tempicol-3, at m.e.d. (minimal effective dose) suppressed tumorigenesis, acting as a cell proliferation modifier and apoptosis inducer in vivo. This work provides the base for further investigations on nitroxide-N-oxide derivatives since the serious question remains to be solved as to what is the molecular mechanism of action of the nitroxide-N-oxides.

Tissue distribution and biotransformation of potassium oxonate after oral administration of a novel antitumor agent (drug combination of tegafur, 5-chloro-2,4-dihydroxypyridine, and potassium oxonate) to rats

S-1, a new oral 5-fluorouracil (5-FU)-derivative antitumor agent, is composed of tegafur, 5-chloro-2,4-dihydropyridine, and potassium oxonate (Oxo). Oxo, which inhibits the phosphorylation of 5-FU, is added to reduce the gastrointestinal (GI) toxicity of the agent. In this study, we investigated the tissue distribution and the metabolic fate of Oxo in rats after oral administration of S-1. Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU, but little distributed to other tissues, including tumorous ones in which 5-FU was observed after oral administration of S-1. Plasma concentration-time profiles of Oxo and its metabolites after i.v. and oral administration of S-1 revealed that Oxo was mainly converted to cyanuric acid in the GI tract. Furthermore, the analysis of drug-related radioactivity in GI contents and in vitro studies suggested that Oxo was converted to cyanuric acid by two routes, the first being direct conversion by the gut flora in the cecum, and the second, conversion by xanthine oxidase or perhaps by aldehyde oxidase after degradation to 5-azauracil (5-AZU) by the gastric acid. These results indicate that, although a part of the administered Oxo was degraded in the GI tract, Oxo was mainly distributed to the intracellular sites of the small intestines in a much higher concentration than 5-FU and that little was distributed to other tissues, including tumors. We conclude that this is the reason why Oxo suppresses the GI toxicity of 5-FU without affecting its antitumor activity.

Lack of effect of the cytokine suppressive agent FR167653 on tumour growth and cachexia in rats bearing the Yoshida AH-130 ascites hepatoma

Daily s.c. administration of 6 mg/kg of FR167653 (an inhibitor of the synthesis of interleukin-1 and tumour necrosis factor-alpha) to rats bearing the ascites hepatoma Yoshida AH-130 (a highly cachectic tumour) did not prevent either the anorexia or the massive weight loss - affecting both adipose tissue and skeletal muscle - present in the cachectic animals. The compound did not affect the circulating levels of triacylglycerols or other metabolites such as glucose or lactate. Nor did the administration of FR167653 influence tumour growth. It is concluded that the drug is unable to reverse the cachectic state in this particular experimental tumour model.

Evidence for peroxidative oxidation of substituted piperidine nitroxides, acting as apoptosis inducers in Yoshida Sarcoma cells in vivo

The results presented herein clearly indicate that nitroxide derivatives--free radicals are effective as substrates for one-electron oxidation in the peroxidase cycle involving hydrogen peroxide, which have been the subject of considerable controversy. This oxidation is catalyzed enzymatically and it might occur in tumor cells (in vivo) where the level of ROS (H2O2 and O2.-) is increased. The result of this reaction involving hydrogen peroxide is the obligative formation of the oxo-ammonium cation involved in the superoxide dismutase-mimic reaction of nitroxides with superoxide and/or in reaction with H2O2 leading to superoxide formation and regeneration of the parent nitroxide molecule. The efficiency of this enzymatically catalyzed oxidation of nitroxide(s) depends on the structure of the substituent in position 4 of nitroxide ring as follows: -OCH3 > -NHCOCH3 > -NHCOCH2CH3. Notably, the reduced nitroxide salt was not substrate for peroxidatic oxidation clearly indicating the importance of the free radical moiety of the nitroxide molecule. These findings may have some relevance in the recent investigations of antioxidant properties/mechanisms of nitroxides. Based on these considerations we hypothesize that the administration of oxidizable free radical nitroxide compounds--antioxidants may be a useful strategy in the treatment and investigations of cancer diseases. An in vivo study ("Screening test of chemicals employing Yoshida Sarcoma animals") was carried out to verify whether the structure and/or the chain length of substituent of oxidizable nitroxide derivatives--antioxidants could influence their apoptotic activity. The results reported in this study are encouraging as we found a limited correlation between the molecular oxidative properties of nitroxides under study, their structure and antitumor (apoptotic) action. In conclusion, this work demonstrates that investigation of the structure-dependent oxidation of antioxidatively acting nitroxides can become a very important step in their future screening and selection for applications in vivo and in vitro.

The paradoxical apoptotic effects of novel nitroxide antioxidants on Yoshida sarcoma cells in vivo: a commentary

Here we show for the first time that the model nitroxide derivatives, free radical or its reduced piperidinium salt, suppressed cytotoxicity of ROS (O2 and H2O2) generated outside the cells (B14 line, model for neoplastic phenotype) in ***. The nitroxides prevented the decrease in the number of *** caused by exogenous O2- and H2O2 at concentrations which were not themselves cytotoxic. In the present study, we have also shown that a very substantial difference in the cell response occurred when the model rat tumor cells (Yoshida Sarcoma ascites) were treated in vivo with six novel synthesized nitroxide antioxidants. A number of tumor cells displayed morphological characteristics of apoptosis. This effect was comparable to those observed for other nitroxyls under similar experimental conditions. Since the increase in the ROS generation followed by apoptotic changes of nuclei is the consistent recent finding in various experimental models of apoptosis, one fundamental question was raised: why nitroxide antioxidants paradoxically act as apoptosis inducers in vivo? Taking together the results presented here and in our previous works, it seems reasonable to suggest that nitroxide-antioxidants improve the endogenous "antioxidants reserve" and action can induce a reductive stress as opposed to an oxidative stress, triggering a cascade of dose-dependent processes involving indirectly an antioxidant mechanism(s) and resulting in the apoptotic death of cancer cells in vivo. The SAR (structure activity relationship) revealed that either the substituent structure at 4-position of the nitroxide ring or its oxidation state are determinant for the degree of the observed differences in the apoptotic potency of nitroxide derivates in vivo.

[Tumor microcirculation and selective enhancement of drug delivery--clinical applications based on pathophysiological experiments]

Tumor tissue is composed of cancer cells (parenchyma) and tumor vessels (interstitium). Many investigators have pointed out that blood flow in tumors has a very inhomogenous distribution, and that this inhomogeneity in blood flow increases as tumors grew. This would be a certain cause of insufficient drug delivery to tumor tissues. Among the experimental evidence using Yoshida Sarcoma and Ascites Hepatomas, functional differences in microcirculation between tumor and normal tissues were found by Suzuki et al. (1977). Under hypertensive state induced by the continuous infusion of angiotensin II, tumor blood flow increased remarkably, while there was no change or decrease in blood flow in normal tissues such as the brain, bone marrow, liver and kidney. Moreover, the increase in blood flow in tumors was selective, as the mean blood pressure remained at the level of 150 mmHg. Increases were confirmed not only in many growing sites such as in the liver, muscle, subcutis, and even microfoci, but also in various kinds of xenografted human tumors and autochthonous tumors. Augmentation of the anti-tumor effects of angiotensin II-induced hypertension chemotherapy (IHC) for advanced gastric carcinoma was revealed in two randomized controlled trials (RCT-1 & 2) of collaborative study groups in Japan. The response rates were 42.9% vs 10.5% in RCT-1 and 31.3% vs 6.7% in RCT-2. The frequencies of toxicities were not statistically different. In the results of phase II studies from 1978 to 1994 (OPN-1) and 1995 to 1999 (OPN-2) for advanced gastric carcinoma (GC), the response rates were 37.9% and 35.7%. Down staging in which the conclusive stage score was lower than the score of the clinical stage, was observed in 8 out of 94 cases (19%) with primary lesions in total and in 30 patients (63%) receiving reduction surgery after IHC, since 1978. It is very important for exact evaluation after chemotherapy to understand or estimate the pathohistological changes in the tumor and its degenerated or repaired tissues, which present various clinical images. In the present study, the actual administered dose intensity of adriamycin (aDIadm) was 5.9 +/- 2.4 mg/sqm/w, and the ratio of aDIadm to the proposed DIadm of reported FAM/FAP schedules was 0.78 +/- 0.32. IHC with smaller DI could lead to a reduction in the accumulation of toxicities of anti-cancer drugs in the host. In conclusion, IHC might be applied to all kinds of tumors to enhance the chemotherapeutic effects through selective increase of drug delivery to tumors.

CHS 828, a novel pyridyl cyanoguanidine with potent antitumor activity in vitro and in vivo

A new class of recently discovered antineoplastic agents, the pyridyl cyanoguanidines, exert a potent antitumor activity in rodents after oral administration. Optimization in vitro and in vivo has resulted in the selection of the lead candidate CHS 828 (N-(6-chlorophenoxyhexyl)-N'cyano-N"-4-pyridylguanidine). CHS 828 was found to exert potent cytotoxic effects in human breast and lung cancer cell lines, with lesser effects on normal fibroblasts and endothelial cells. In a study using a panel of cell lines with different resistance patterns, the effects of CHS 828 showed a low correlation with the activity patterns of known anticancer agents, and no sensitivity to known mechanisms of multidrug resistance was observed. In nude mice bearing human tumor xenografts, CHS 828, at doses from 20 to 50 mg/kg/day p.o., inhibited the growth of MCF-7 breast cancer tumors and caused regression of NYH small cell lung cancer tumors. Oral administration of CHS 828 once weekly improved efficacy without increasing toxicity. CHS 828 was found to compare favorably with established chemotherapeutic agents such as cyclophosphamide, etoposide, methotrexate, and paclitaxel. In mice with NYH tumors, long-term survival (>6 months) was observed after treatment with CHS 828 was stopped. In conclusion, CHS 828 is an effective new antitumor agent, with a potentially new mechanism of action. CHS 828 is presently being tested in Phase I clinical trials in collaboration with the European Organization for Research and Treatment of Cancer.

[Problems and prospects for combined chemotherapy with 5-fluorouracil and low-dose cisplatin]

Recently, the efficacy of combined chemotherapy with 5-fluorouracil and low-dose cisplatin for advanced gastrointestinal cancer has been reported in Japan. However, this method has not become established, because the underlying logic is unclear and the quality of its clinical trials has been unsatisfactory. We suggest the mechanism for this depends not only on the action of CDDP as a modulator of 5-FU, but also on a mutual biochemical modulation in which 5-FU acts as a modulator of CDDP and enhances the effect of CDDP. We expect that numerous phase II studies and the accumulation of reliable data will lead to improvements.

Inhibitory effect of combined administration with CPT-11 and 5-fluorouracil in vitro and in vivo

Combined antitumor activity of CPT-11 and 5-fluorouracil (5-FU) was evaluated in a human cultured cell line derived from lung cancer. After 24 h culture with SN-38 followed by 5-FU 24 h, synergistic effect was observed in the cell line. In addition, the antitumor effect of this combination was studied in in vivo experiments using Donryu rat with Yoshida sarcoma cells. CPT-11 and 5-FU synergistically inhibited tumor growth. There was no significant increase of toxicity as assessed by the body weights. These results might support for the combination with 5-FU and CPT-11 in a chemotherapy for cancer.

Anticancer potential of N,N-diethylaminoethyl ethers of flavanone oximes: a comparison with mitoxantrone action on rat Yoshida sarcoma cells in vivo

This study was performed to evaluate the anticancer abilities of four biologically active N,N-diethylaminoethyl ethers of flavanone oximes against rat Yoshida Sarcoma cells in vivo, and to investigate the mechanism(s) involved. The effects were compared with those of anthraquinone drug (mitoxantrone) action. The presented results provide the first evidence that all the investigated substances induce programmed cell death (apoptosis) of Yoshida Sarcoma cells in vivo. On interpretative grounds, the administration of investigated flavanone derivatives in the promotion phase of the disease led to both growth inhibition (cell cycle perturbation) and apoptosis. A correlation was found between structure of the substituent(s) at B-ring of substances and the revealed anticancer activity. The data suggest that flavanone derivatives (oxime ethers) besides their antiradical, antioxidant and radioprotector properties observed before, may act as promising anticancer agents acting in the promotion phase of disease. This finding prompted us to consider the development of a new strategy: modulation of effects using combination therapy involving mitoxantrone and flavanone oximes.

Anticancer activity and toxicity of S-1, an oral combination of tegafur and two biochemical modulators, compared with continuous i.v. infusion of 5-fluorouracil

S-1 is an oral combined form of 1 M tegafur [a prodrug of 5-fluorouracil (5-FU)], 0.4 M 5-chloro-2,4-dihydroxypyridine (a reversible inhibitor of dihydropyrimidine dehydrogenase) and 1 M potassium oxonate (an inhibitor of orotate phosphoribosyltransferase). S-1 has been shown to exert a potent antitumor effect with low gastrointestinal toxicity in experimental tumor models. We have therefore compared the antitumor effect of oral S-1 with that of continuous infusion of 5-FU in rats bearing transplants of human and murine tumors. Almost complete inhibition of the tumor growth was obtained on 7 day schedules in Yoshida sarcoma-bearing rats by consecutive administration of 30 mg/kg/day of oral S-1 and 40 mg/kg/day infusion of 5-FU. However, a significant difference between the incidence of toxicities of S-1 and 5-FU, including body weight loss and diarrhea, was noted. The rats given the 5-FU infusion had marked weight loss and severe diarrhea, while those given oral S-1 had neither. Although about 50% inhibition of the tumor growth was attained with 15 mg/kg/day of oral S-1 and 30 mg/kg/day infusion of 5-FU in nude rats with xenografted human colon cancer (KM12C), the rate of body weight loss in the 5-FU-treated group was distinctly higher than in the S-1-treated group. The ratio of the 5-fluoronucleotide concentrations in gastrointestinal tissue to that in the tumor was lower in the S-1-treated rats than in the 5-FU-treated rats. In conclusion, the results suggest that oral S-1 might be more effective in the treatment of cancer patients than continuous infusion of 5-FU, from the standpoint of antitumor potency and toxicity.

Design and testing of a new cisplatin form using a base material by combining poly-D,L-lactic acid and polyethylene glycol acid against peritoneal metastasis

Microspheres containing cisplatin (CDDP) embedded in poly-d,l-lactic acid (PLA) and polyethylene glycol acid (CDDP-PPMS) were developed to improve treatment of malignant effusions. In vitro studies demonstrated that CDDP was released continuously for more than 4 weeks from CDDP-PPMS without initial burst. CDDP-PPMS was compared with CDDP aqueous solution (CDDP-SOL) by i.p. administration in rats for 1) tissue distribution, 2) toxicity and 3) therapeutic effects against Yoshida sarcoma. We found that the CDDP concentration in the omentum was maintained at a higher level than in the CDDP-SOL group, while the particles of CDDP-PPMS were observed in the stomata of the omentum by electron microscopy. Concentrations of CDDP in the lung, liver, kidney and blood were lower in the CDDP-PPMS group than in the CDDP-SOL group. All rats given CDDP-PPMS containing < or = 28 mg/kg were alive, whereas in the CDDP-SOL group, all rats given > or = 16 mg/kg died from side effects. The LD50 of CDDP-PPMS and CDDP-SOL were 32.8 and 14.8 mg/kg, respectively. The survival of rats with peritoneal metastasis was better in the CDDP-PPMS group than in the CDDP-SOL group.

[Invention of a tumor-selective 5-fluorouracil derivative named S-1 by biochemical modulation of 5-fluorouracil]

A new oral type of 5-fluorouracil (5-FU) derivative possessed of both potent antitumor activity and less gastrointestinal (GI) toxicity was investigated and developed in the form of a combination of tegafur (FT), a masked form of 5-FU, and its two peculiar biochemical modulators. One is 5-chloro-2,4-dihydroxypyridine (CDHP), a new potent inhibitor of 5-FU degradation in vivo, and another is potassium oxonate (Oxo), a characteristic inhibitor of 5-FU phosphorylation, which distributes much higher in GI tract after p.o. administration. 5-FU levels in blood of rats following administration of FT, were markedly elevated and persisted for a long-time by co-oral CDHP corresponding to over 0.4 molar ratio to FT, like the case in continuous infusion of 5-FU, which resulted in an augmentation of antitumor efficacy in Yoshida sarcoma-bearing rats, although severe GI toxicity simultaneously occurred. To reduce 5-FU-induced toxicities such as diarrhea and body weight loss and to maintain the augmented antitumor activity, 0.5 to 2 molar Oxo was orally given to rats with one molar FT plus 0.4 molar CDHP. As a result, both severe GI injury and body weight loss were markedly inhibited by coadministration of 0.5 to 1.0 molar Oxo while high antitumor efficacy (about 90% inhibition of tumor growth) was maintained. However, such almost complete antitumor effect was reduced to about 50% inhibition of tumor growth by over 2 molar Oxo combined with one molar FT plus 0.4 molar CDHP. Based on these results, a novel 5-FU derivative, named S-1, was composed of one molar FT, 0.4 molar CDHP and one molar Oxo. S-1 showed an antitumor activity over 3-fold stronger than UFT (one molar FT plus 4 molar uracil) against Yoshida sarcoma and Sato lung carcinoma in rats and human colon carcinoma (KM12C) xenografted in nude rats when its minimum toxic dose was administered. Co-oral Oxo also significantly reduced the incidence of diarrhea and stomatitis induced by administration of FT-CDHP in beagle dogs. These results suggest that high antitumor activity and less GI toxicity of S-1 was brought about by the elevation in blood and tumor tissues and by selective decrease of 5-fluoronucleotides, an active metabolite of 5-FU, in GI tract.

Doxorubicin and vincristine with methionine depletion contributed to survival in the Yoshida sarcoma bearing rats

Several anti-cancer agents show increased toxicity if administered with methionine-depleting total parenteral nutrition (Met-deplete TPN). Changes in the cell cycle due to Met-deplete TPN were investigated, and then the enhancement of the anti-tumor effects of serial combinations of doxorubicin (ADM), a drug acting on late S-G2 phase and vincristine (VCR), an antimitotic drug, under Met-deplete TPN was also examined in the tumor-bearing rats. According to the fraction of labeled mitosis, within 3 to 4 days after the introduction of Met-deplete TPN in the ascites type Yoshida sarcoma (YS) -bearing rats, the cell cycle of the tumor cells showed marked delay and the fraction of labeled mitosis decreased to less than 70%. However, this delay was recovered immediately after methionine infusion, with on increase in the labeled mitotic cell population. In the experiment using solid type YS-bearing rats, ADM was administered intraperitoneally under Met-deplete TPN for 8 days, followed by intraperitoneal VCR administration with methionine-containing TPN for 3 days, and then fed on solid food and water ad libitum until death. This serial combination of Met-deplete TPN with ADM and VCR resulted in marked suppression of the tumor and prolonged survival in comparison to the control groups with a significant difference (p < 0.001) (generalized Wilcoxon test).

Enhancement of therapeutic efficacy of bleomycin by incorporation into biodegradable poly-d,l-lactic acid

A new system for the delivery bleomycin (BLM) to target lesions was established by incorporating BLM into a small cylinder of a biodegradable polylactic acid (PLA) of low molecular weight. Cross-sectional analysis of the system (BLM-PLA) showed that BLM particles were uniformly enclosed in the PLA matrix. In vitro studies demonstrated that BLM was released continuously for more than 3 weeks from BLM-PLA immersed in saline. BLM-PLA was implanted subcutaneously into the backs of rats. A high concentration of BLM was maintained in the connective tissues near the implants for 2 weeks. In contrast, the level of BLM activity was low when a BLM solution (BLM-SOL) was administered subcutaneously by injection. The concentration of BLM in the abdominal lymph nodes was significantly higher following BLM-PLA implantation than following subcutaneous BLM-SOL injection. The inhibitory effects of BLM-PLA and BLM-SOL on tumor growth were compared with no treatment using a subcutaneously transplanted Yoshida sarcoma. The antitumor effect of BLM-PLA was significantly higher than that of BLM-SOL and no treatment. BLM-PLA also resulted in a more favorable distribution of BLM than BLM-SOL. Thus, BLM-PLA proved to be effective in controlling this experimentally transplanted tumor.

Increased growth and incidence of lymph node metastases due to the angiogenesis inhibitor AGM-1470

Using the rat tumour cell line LY80, a subline of Yoshida sarcoma, the effects of AGM-1470 on the growth of primary tumour and the incidence of regional lymph node metastasis were evaluated. AGM-1470 (30 mg kg(-1)) was administered subcutaneously or intravenously. Subcutaneous (s.c.) and intravenous (i.v.) injections were repeated for 8 days and 7 days respectively. Tumour growth of a primary region tended to be suppressed by AGM-1470. The s.c. tumours after sacrifice were much smaller in the AGM-1470-treated group (s.c. injection) than in the control groups. However, the growth of metastatic foci in the lymph nodes was prompted markedly by AGM-1470. All six of the AGM-1470-treated rats had developed swollen axillary lymph nodes and/or brachial lymph nodes on day 19 after tumour implantation (the 7th day after the last treatment) compared with one of six saline-injected rats and three of six vehicle-alone treated rats with swollen axillary lymph nodes. The weight of lymph nodes after sacrifice in the AGM-1470-treated rats was much heavier than that of the other two groups. Histological examination showed that in the AGM-1470-treated group, the cortex and the medulla of the axillary lymph nodes were almost entirely replaced by tumour cells while, in the vehicle alone group, a notable hyperplasia of the lymph nodes due to BT cell proliferation tended to be induced. In the saline group, although a slight hyperplasia of lymph nodes was observed, there were only a few lymph node metastases. In the case of i.v. injection of AGM-1470, similar results were obtained. It is thought that LY80 cells spread to regional lymph nodes at a comparatively early stage by some change or other in which AGM-1470 participated. From the present experiment, it is concluded that application of AGM-1470 alone to patients should be carried out with great caution.

Antitumor activity and low intestinal toxicity of S-1, a new formulation of oral tegafur, in experimental tumor models in rats

S-1, a new oral antitumor agent, is composed of 1-(2-tetrahydrofuryl)-5-fluorouracil (Tegafur, FT), 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo) in a molar ratio of 1:0.4:1. FT which is a masked compound of 5-fluorouracil (5-FU) acts as an effector, while both CDHP and Oxo which do not have antitumor activity themselves act as modulators. In this study, the antitumor activity and intestinal toxicity of S-1 were investigated using experimental tumor models in rats, and compared with those of other oral fluoropyrimidines, namely 5-FU, FT, FCD (1 M FT/0.4 M CDHP) and UFT (combination of FT and uracil). In rats bearing subcutaneous Yoshida sarcoma, S-1 inhibited tumor growth at the lowest dose (ED50 value: S-1 5, UFT 22, FT 82, FCD 5, and 5-FU 19 mg/kg per day), and induced the least host body weight suppression, leading to the highest therapeutic index (TI) (S-1 4.5, UFT 1.4, FT 1.8, FCD 2.0, and 5-FU 1.4). S-1 also showed a higher therapeutic effect than UFT against AH-130 and Sato lung carcinoma. After administration of S-1 and UFT at equitoxic doses, S-1 showed a higher and more prolonged concentration of 5-FU than UFT both in plasma (AUC0-infinity: S-1 28 nmolh/ml, UFT 15 nmol.h/ml) and in tumor tissue (AUC0-infinity: S-1 95 nmolh/g tissue, UFT 52 nmolh/g tissue), leading to a higher 5-FU level incorporated into the RNA fraction (F-RNA level) in tumor tissue (AUC0-24: S-1 7.0 nmolh/mg RNA, UFT 4.3 nmolh/mg RNA) and 5-8% higher thymidylate synthase (TS) inhibition in tumor tissue at every time-point through 24 h. Compared with other oral fluoropyrimidines after administration of the maximal tolerable dose (MTD), S-1 caused the lowest rates of intestinal toxicities, such as diarrhea and occult blood in feces. S-1 also showed a higher antitumor effect on Yoshida sarcoma implanted intracolonically than UFT at an equitoxic dose (tumor weight: S-1 64 +/- 30 mg, UFT 133 +/- 52 mg; P < 0.05). These results suggest that CDHP, which is a potent inhibitor of 5-FU degradation, increases the antitumor activity of FT, and that Oxo, which is an inhibitor of 5-FU phosphorylation, locally protects the gastrointestinal tract from 5-FU-induced toxicity without decreasing the antitumor activity.

Anticancer efficacy of methioninase in vivo

Therapeutics that are selective for cancer would have a high potential for efficacy. We have previously shown that the metabolic defect of enhanced methionine dependence is a broad cancer-selective target. Methionine depletion can completely arrest the growth of methionine-dependent tumor cells in vivo with a reversible pre-mitosis cell-cycle block. Dietary methionine depletion can partially arrest the growth of methionine-dependent rodent tumors in vivo. This report demonstrates that methioninase isolated from Pseudomonas putida can arrest rodent and human tumors in nude mice with no apparent toxic side effects. Methioninase injected i.p. arrested the growth of the Yoshida sarcoma in nude mice and greatly slowed the growth of the H460 human non-small-cell-lung carcinoma in nude mice. The effectiveness of methioninase against H460 was in contrast to 5-fluorouracil and vincristine, which were inactive against this tumor. The activity of the administered methioninase did not cause weight loss for up to 10 days treatment at 40-120 units/day indicating the possibility of low toxicity. In contrast, vincristine was highly toxic despite its ineffectiveness. Methioninase also induced a tumor-specific late cell-cycle block. The tumor-selective late cell-cycle block induced by methioninase should be able to be exploited to enhance the tumor specificity of antimitotic drugs and other agents in future experiments. Thus methioninase is a highly effective antitumor agent with a new tumor-selective mode of action with minimal toxicity, demonstrating potential clinical effectiveness against solid tumors.

[Experimental study of cisplatin microspheres incorporated in polylactic acid and polyethylene glycol acid on peritoneal carcinomatosis in rats]

Cisplatin incorporated into polylactic acid/polyethylene glycol acid blend polymeric microspheres was prepared as a dosage (CDDP-MS) by solvent evaporation method in oil-in-oil emulsion system. CDDP-MS and CDDP aqueous solutions (CDDP-SOL) were intraperitoneally administered to compare the tissue distribution of CDDP in 72 rats each. On 0.5, 1, 7, 14, 21 and 30 days, the omentum, lung, liver and kidney were removed, and the CDDP concentration was measured. The CDDP concentration of CDDP-MS group was maintained at a high level in the omentum for a long time. On the other hand, the CDDP level of the CDDP-MS group was low in the lung, liver and kidney, compared with the CDDP-SOL group. Additionally, acute toxicity of anticancer drug in CDDP-MS group was reduced, compared with CDDP-SOL. The effects of CDDP-MS, CDDP-SOL, empty-MS and non-therapy group on survival time were compared using intraperitoneally administered Yoshida sarcoma. The survival time in CDDP-MS, CDDP-SOL, non-therapy and empty-MS group were 43 +/- 24, 11.7 +/- 4.7, 9.8 +/- 1.1, and 7.8 +/- 1.1 days each. Consequently, it was suggested that CDDP-MS is useful as a tool in loco-regional chemotherapy using drug delivery system.

[Local chemotherapy by a sustained-release preparation with fibrin seal against the operative wound in head and neck cancer]

Fibrin seal has been used for hemostasis and sealing in operative field of tumors in the head and neck. The authors applied it for drug preparation and tried a local chemotherapy to treat residual and disseminated tumors of cellular level in the operative wound using 5-FU. The drug release rate in this therapy in vitro study was 50% after 24 hrs. When injected to rats bearing Yoshida sarcoma, it exhibited a marked antitumor effect compared to the control group given 5-FU alone. This therapy is easy to make the dosage adjustment and can apply drugs directly to the tumor residue at the high concentration. It will be clinically a useful adjuvant therapy for radiotherapy, surgery or chemotherapy.

Synthesis and antitumor activity of two ifosfamide analogs with a five-membered ring

Two ifosfamide (CAS 3778-73-2) analogs with a five-membered ring, i.e. the oxazaphospholidine derivatives 6 and 7, were synthesized and their cytotoxic activity in vitro, acute toxicity and antitumor activity in vivo determined in comparison with the oxazaphorinane ifosfamide 1. The observed low biological activity gives evidence that both, the six-membered oxazaphosphorinane ring and the two N-2-chloroethyl-side chains are necessary for the generation of the ultimate alkylator, i.e. the ifosfamide mustard 5.

Changes in folate concentration in Yoshida sarcoma after administration of leucovorin or cisplatin

Both leucovorin (LV) and cisplatin (cis-dichlorodiammine platinum II, CDDP) act as modulators of 5-fluorouracil (5-FUra) by increasing the intracellular concentration of reduced folate. We measured intracellular folate levels following the administration of LV or cisplatin in tumor-bearing rats to determine the optimal schedules for their use as 5-FUra modulators. Donryu rats were inoculated with Yoshida sarcoma cells on the right flank. Seven days after tumor inoculation, the animals were injected with LV or CDDP. The kinetic and dose-related changes in intracellular folate concentration were analyzed by means of a binding assay. Folate levels in the tumor tissues were significantly higher than baseline 1 and 2 h after administration of LV and remained significantly high until 8 h after administration. Folate levels in the tumor tissues were significantly higher than baseline 1 and 2 h after cisplatin administration, then decreased to a rather low level 8 h after, and to a significantly lower level than baseline 24 h after administration. The folate levels in the tumor tissue increased in proportion to the dose of LV, but did not increase when the dose of cisplatin was increased from 1 mg/kg to 8 mg/kg. Repeat high-dose administration of LV and repeat low-dose administration of cisplatin are advocated when they are used as modulators of 5-FUra.

Field bean protease inhibitor preparations, unlike methotrexate, can completely suppress Yoshida sarcoma tumor in rats

Protease inhibitor preparations (PIP) with antitryptic and antichymotryptic activities, isolated from field bean legume as well as doxorubicin and cyclophosphamide could effectively suppress the growth of Yoshida sarcoma ascites tumor cells transplanted in adult rats and prevent their death. As against this, methotrexate and heat-inactivated PIP were ineffective in such rats at varied doses of treatment tried. The percent survival of animals appeared to be related to the purity, treatment mode and the dose of PIP used. Zymographic analysis of the trypsin activated sarcoma cell homogenate revealed the presence of six protease bands in the molecular weight range of 51kD to 206kD. Prolonged interactions of such zymograms with protease inhibitors such as 20mM EDTA or 5mM diisopropyl flurophosphate (DIFP) or 400 micrograms/ml of PIP in reaction buffer indicated that these are not metalloproteases but serine proteases whose activities are inhibited by PIP and DIFP. Since proteases are involved in cell growth regulation and cell transformation, we hypothesize a positive relationship between the field bean protease inhibitor's blocking action on tumor cell proteases and its tumor suppressing activity.

[Innate resistance to thymidylate synthase inhibition after 5-fluorouracil treatment--a rationale of combined use of cisplatin and its optimal administration dose]

We examined the changes of the number of FdU MP binding sites of thymidylate thynthase (TS-BS) in Yoshida sarcoma after administration of 5-FU to the tumor bearing rats. We also investigated the optimal dose of CDDP for the increase of intracellular folate level. In the group received consecutive 7-days administration of UFT (U-7 group), total TS-BS was significantly increased compared with non-treatment group and the group received only UFT (U-1 group). For free TS-BS, however, there was no difference despite of UFT administration. Thymidylate synthase inhibition rate (TSIR) was, therefore, significantly high in U-7 group compared with U-1 group. It seemed necessary to take some counter measure for the induction of TS in the tumor tissue when 5-FU chemotherapy was performed. The optimal dose of CDDP as a modulator of 5-FU was 1 mg/kg in rat when it was estimated from the changes of intracellular folate levels after administration, which was less than the dose to reveal its own anticancer effect.

[The mechanism of potentiation of the antitumor effect of 5-fluorouracil by methionine-free intravenous amino acid solution (AO-90) in rats]

AO-90, a methionine-free intravenous amino acid solution (7.43%) showed to potentiate the antitumor effect of 5-fluorouracil (5-FU) when concomitantly used as the nitrogen source in total parenteral nutrition (TPN) in Yoshida sarcoma (YS)-bearing rats. In the present experiment, this potentiation mechanism was studied by determining the serum methionine level and tumor methylenetetrahydrofolate (CH2FH4) content in YS-bearing Donryu rats given AO-90 (nitrogen 0.73g/kg on the 1st day and 1.46g/kg for the remaining 6 days) by TPN for 1 week. The rats were subcutaneously inoculated with 10(4) YS cells in the dorsum 3 days before the start of TPN. Inhibition of thymidylate synthase activity in tumor tissue after dosing of AO-90 (nitrogen 0.68g/kg on the 1st day and 1.36 g/kg for the remaining 6 days) by TPN along with daily intraperitoneal dosing of 5-FU (10 mg/kg) was also evaluated with the inoculation of 10(6) tumor cells. The results were compared with those in tumor-bearing rats given TPN with a commercially available amino acid solution containing methionine. On day 5 of TPN, the tumor-bearing rats given AO-90 showed a significantly lower serum methionine level than the control rats: 101 +/- 11 mumol/l versus 29 +/- 14 mumol/l (p < 0.01); and a higher CH2FH4 content in tumor: 7.0 +/- 2.8 pmol/g protein versus 23.7 +/- 16.6 pmol/g protein (p < 0.05). Thymidylate synthase inhibition was 81.2 +/- 5.1% in the AO-90 group and 30.9 +/- 26.3% in the control group (p < 0.01). The results of the present study suggest that AO-90 potentiate the antitumor effect of 5-FU by biochemical modulation. AO-90 concomitantly given with 5-FU for 7 days was effective not only in the allogeneic tumor model, but also in WKAH and SHR rats previously inoculated with 10(6) of syngeneic KDH-8 hepatoma cells and SST-2 adenocarcinoma cells, respectively. Weight of SST-2 adenocarcinoma in SHR rats after the TPN period was significantly smaller in the AO-90 group than in the control rats given methionine-containing TPN and 5-FU: 2.66 +/- 0.91 versus 5.12 +/- 2.11 (p < 0.05).

Effects of fluidity and vesicle size on antitumor activity and myelosuppressive activity of liposomes loaded with daunorubicin

The effects of fluidity and vesicle size on the antitumor activity and myelosuppressive activity of liposomes loaded with daunorubicin, an anthracycline antitumor drug, were investigated in Yoshida sarcoma-bearing rats. Liposomes composed of egg phosphatidylcholine (EPC) or hydrogenated egg phosphatidylcholine (HEPC), cholesterol and dicetyl phosphate in a molar ratio of 5:4:1 were injected intravenously into rats 5 d after subcutaneous inoculation of Yoshida sarcoma. At non-effect dosage in free drug, HEPC-liposomes with a diameter of 58 or 142 nm showed the greatest inhibitory effect against Yoshida sarcoma among liposomes tested, whereas larger ones (272 nm) had weaker effect. Small EPC-liposomes (57 nm) had no effect. Larger HEPC-liposomes (especially 142 nm) greatly decreased the number of peripheral white blood cell compared with free drug at the same dose, indicating relatively strong myelosuppressive toxicity. However, small EPC- and HEPC-liposomes with a diameter of 57 and 58 nm, respectively, showed toxic effects comparable to that of free drug. Examination of the dose-dependency of therapeutic effects and toxicity indicated encapsulation of daunorubicin in the small HEPC-liposomes to enhance the therapeutic index about 3 times that of free drug. These findings indicate the possibility of using small HEPC-liposome as a drug carrier for targeting solid tumors.

Effects of a modified CMF treatment (cyclophosphamide, methotrexate and 5-fluorouracil) on hematopoietic tissues and Yoshida sarcoma in rats

Effects of a modified CMF treatment on hematopoietic tissue and an implanted tumor were studied in rats. The modification of the treatment refers to the application of cyclophosphamide 24 h after methotrexate and 5-fluorouracil. The study was done on Wistar rats bearing Yoshida sarcoma in the ascites form. The controls were a) untreated animals bearing the tumor or b) treated conventionally with the 3 cytostatics and c) tumor-free animals under either conventional treatment or d) modified treatment. We examined survival, the appearance of metastases, and the regeneration of hematopoietic tissues. Improved survival, the absence of metastases, and improved regeneration of hematopoietic tissues was observed when modified CMF treatment was applied. These results support the importance of sequencing cytostatic protocols for basic hematological determinants and anti-tumor activity.

3-Cyano-2,6-dihydroxypyridine (CNDP), a new potent inhibitor of dihydrouracil dehydrogenase

3-Cyano-2,6-dihydroxypyridine (CNDP) was identified as a potent inhibitor (IC50 value, 4.4 nM) of dihydrouracil dehydrogenase (DHUDase) [EC 1.3.1.2], a rate-limiting enzyme in 5-fluorouracil (5-FU) degradation. The inhibitory activity of CNDP was about 2,000 times that of uracil under our assay conditions. Kinetic analyses with partially purified enzyme from rat liver revealed that the mechanism of inhibition of DHUDase by CNDP was of mixed type with an inhibition constant (Ki) of 1.51 nM. CNDP had less effect on 5-FU phosphorylation than on 5-FU degradation. The inhibitory effect of CNDP on ribosylation of 5-FU was 600 to 1,000 times less than that on DHUDase. Moreover, CNDP did not inhibit uridine kinase, thymidine kinase, or pyrimidine phosphoribosyltransferase. Coadministration of CNDP with 1-ethoxymethyl-5-fluorouracil (EM-FU) to rats with Yoshida sarcoma elevated the level of 5-FU in both the blood and the tumor and enhanced the antitumor effect of EM-FU. These findings indicated that CNDP would be a useful chemical modulator in chemotherapy with 5-FU or its prodrugs.

Inhibition by oxonic acid of gastrointestinal toxicity of 5-fluorouracil without loss of its antitumor activity in rats

The possibility of decreasing the gastrointestinal (GI) toxic effects of 5-fluorouracil (5-FU) on the digestive tract such as its injury of cells and induction of diarrhea, without reducing its antitumor activity, was investigated in rats. Oxonic acid was found to inhibit the phosphorylation of 5-FU to 5-fluorouridine-5'-monophosphate catalyzed by pyrimidine phosphoribosyl-transferase in a different manner from allopurinol in cell-free extracts and intact cells in vitro. On p.o. administration of 5-FU (2 mg/kg) and a potent inhibitor of 5-FU degradation to Yoshida sarcoma-bearing rats, oxonic acid (10 mg/kg) was found to inhibit the formation of 5-fluorouridine-5'-monophosphate from 5-FU and its subsequent incorporation into the RNA fractions of small and large intestine but not of tumor and bone marrow tissues. This selective inhibition of 5-FU phosphorylation in the GI tract was due to the much higher concentrations of oxonic acid in GI tissues than in other tissues and the blood. On p.o. administration with the 5-FU derivative, UFT, which is a combined form of 1 M tegafur and 4 M uracil and usually administered p.o. to cancer patients in Japan, oxonic acid (10-50 mg/kg) markedly reduced injury of GI tissues and/or severe diarrhea without influencing the antitumor effect of UFT. These findings suggest that coadministration of oxonic acid suppresses the GI toxicity of 5-FU and its derivatives without affecting their antitumor activity and thus prolongs the life span of cancer-bearing rats.

[Experimental study on antitumor effect of cisplatin-microcapsule]

CDDP-microcapsule (CDDP-mc) was prepared in the search for method for administering anti-cancer agents and has been examined for its properties, vital reaction and antitumor effect. In the present study, the results of the examination and possibility of application of CDDP-mc are reported. 1) It took 48 hours for CDDP to be released from the microcapsule into saline. 2) CDDP-mc size is 80-200 microns, and it contains 0.645mg of CDDP per mg of microcapsule. It was available as a drug enabling us to introduce a high concentration of CDDP into tumor tissue. 3) The side effects of CDDP-mc on animals (rabbit and rat) were more limited than those of ordinary CDDP solution and slight, especially for intraperitoneal or local injection. Intraarterial infusion of CDDP-mc, however, causes transitory palsy of the treated lower extremity probably due to embolism. 4) Its intraperitoneal administration was much more effective than the ordinary CDDP solution against Yoshida's sarcoma implanted in rats. 5) The subcutaneous administration of CDDP-mc was more effective compared to ordinary solution of CDDP. 6) The above results suggested that CDDP-mc is clinically applicable to the treatment of ovarian cancer and uterine cancer when administered intraperitoneally and locally (intra-tumor).

Antitumor effect of a mycotoxin: rubratoxin B

The antitumor effect of rubratoxin B, a mycotoxin, has been studied. Yoshida ascites sarcoma cells, in vitro in contact for 30 min with the drug and injected immediately afterwards into young rats by the intraperitoneal route, produced the survival of 80% of the animals and the doubling of the median survival time of the rats developing neoplasia. In vivo administration of the drug by the intraperitoneal route 24 h after implantation of tumor cells determined the prolongation of median survival time; supplied by other routes both against T8 sarcoma of Guérin and Yoshida ascites sarcoma it was ineffective. The differences between in vitro and in vivo results can be explained by a rapid neutralization of the drug on behalf of the organism's enzymes or by being bound to proteins and peritoneal cells unlike tumor cells.

Metabolic response of AH13r rat tumours to cyclophosphamide as monitored by pO2 and pH semi-microelectrodes

The composition of the microenvironment has an important influence on the cellular response to cytotoxic agents. Using pH and pO2 semi-microelectrodes, we have monitored metabolic changes in AH13r rat tumours as a function of time after subcurative chemotherapy. Prior to therapy, tumours contained large areas considered hypoxic (mean pO2 approximately 4 mmHg) and are characterised by a marked accumulation of acidic metabolites (mean pH 6.65). Administration of cyclophosphamide (40 mg/kg body weight) resulted in tumour regression to 15% of pretreatment volumes and a growth delay of 12 days. Concomitant with volume reduction, tumours became reoxygenated (mean pO2 approximately 7 mmHg), with maximum values being reached within 2-4 days, paralleled by a shift of pH to more alkaline values (0.17 U on average). These changes coincided with the development of subtotal necrosis. During early tumour regrowth, the pH and pO2 histograms returned to control values. These data corroborate and extend the results of previous studies in which noninvasive techniques had been applied for the monitoring of treatment-induced metabolic changes in malignant tumours in vivo. In addition, these results support the notion that the effectiveness of anticancer therapy might be improved by selecting and scheduling therapeutic agents in consideration of physiological changes caused by preceding courses of treatment.

Schedule dependent inhibition of thymidylate synthase and tumor growth by 5-fluorouracil in Yoshida sarcoma bearing rats

Schedule dependent inhibition of thymidylate synthase (TS) and tumor growth by 5-fluorouracil (FUra) was examined in Yoshida sarcoma (YS) bearing Donryu rats. After implantation of YS cells (1 x 10(4), FUra (20 mg/kg/day) was continuously (group C) or daily bolus injection (group B) administered for 6 days. On day 7, tumor weight was 1.57 +/- 0.58 g in group C and 0.45 +/- 0.10 g in group B (P less than 0.01), free TS was 2.23 +/- 83 fmol/mg protein in group B and 96 +/- 55 fmol/mg protein in group C (P less than 0.05), and inhibition rate of TS was 88.3 +/- 5.3% in group C and 94.7 +/- 3.0% in group B (P less than 0.05). A significant correlationship was found between free TS and tumor weight (P less than 0.05). As the next step, continuous infusion (group C) or daily bolus injection (group B) for 6 days was started on day 5 after implantation of YS cells. The relative increase of tumor on day 9 was 256 +/- 111% in group C and 112 +/- 22.1% in group B (P less than 0.05). On day 11, total TS of the resected tumor was 650 +/- 153 fmol/mg protein in group C and 391 +/- 124 fmol/mg protein in group B (P less than 0.05), and inhibition rate of TS was 78.8 +/- 12.4% in group C and 84.4 +/- 8.6% in group B. Daily bolus injection of FUra causes a superior antitumor and antimetabolic effect. The schedule dependent cytotoxicity of FUra should be taken into account when a chemotherapeutic protocol is designed.

Anti-tumor properties of the organometallic complex cis-dimethylbis[sulfinylbis[methane]-S]platinum(II)

The water-soluble organometallic complex cis-[Pt(Me)2(Me2SO)2] (Me = methyl; Me2SO = dimethyl sulfoxide) (cis-dimethyl platinum(II); CDMP) was evaluated for its toxicity on the rat and for its efficacy against two tumors of this animal: the Yoshida ascites sarcoma and the T8 sarcoma of Guérin. The lethal dose for 50% of normal animals was 46.4 mg/kg; the predominant toxic effects were loss of weight, decrease in leukocytes and necrosis of the kidneys after i.v. or of the liver after i.p. administration. Doses of drug varying from 2 to 40 mg/kg were administered once by i.p., i.v., i.m. and intra-tumor (i.t.) route from 1 to 7 days after i.p. injection of 10(6) Yoshida ascites sarcoma cells and s.c. implantation of approximately 300 mg of T8 sarcoma of Guérin. The compound showed anti-tumor activity increasing both the average life span and survival of the rats. A comparison between the therapeutic properties of the title complex with those of cis-[PtCl2(NH3)2] (CDDP) reveals that cis-dimethyl platinum(II) exhibits the same anti-tumor activity associated with 6 times reduced toxicity.

Affinity of intraperitoneally injected activated carbon particles adsorbing mitomycin C to tumor surface of Yoshida sarcoma

A new dosage form of mitomycin C (MMC-CH) comprising 0.75 mg/ml of activated carbon particles adsorbing mitomycin C at 124 micrograms/mg and 7 micrograms/ml of mitomycin C in a free state was injected intraperitoneally to male rats of Donryu strain transplanted intraperitoneally with 10(7) cells/rat of Yoshida sarcoma 4 days before injection. The rats were subjected to autopsy within 60 min after injection. MMC-CH adhered selectively to the tumor surface of Yoshida sarcoma growing intraperitoneally rather than to the surface of organs such as small intestines which the surface cancer did not affect. Within 120 min after injection, mitomycin C concentration in the tissue samples was bioassayed. Intraperitoneally injected MMC-CH distributed high levels of mitomycin C to the tumor rather than to the unaffected organ located intraperitoneally. Animals killed by cancer after the treatment of MMC-CH were autopsied. Histological effects of MMC-CH were studied microscopically. Mitomycin C adsorbed on activated carbon particles induced degenerative changes in the tissues of tumors to which the activated carbon particles had adhered.

[Index of tumor response by in-vivo 31P-MRS--T1 effect as a new predicting index of therapeutic effects]

We observed the metabolism of the Yoshida sarcoma by in-vivo 31P-MRS, using two varieties of repetition time (TR), i.e., TR2s and TR10s. It was measured before the injection of 5FU and 4, 24, 48 hours after the injection. In the each time, PME/ATP ratio, intracellular pH, and TR10/TR2 ratio of PME which reflects the T1 value of PME, were calculated. TR10/TR2 ratio of PME decreased 4 and 24 hours after the injection of 5FU and recovered 48 hours after the injection to the same level before the injection. However decrease of PME/ATP ratio was not observed until 48 hours after the injection of 5FU, when apparent tumor regression appeared. These results suggested that the T1 value of PME decreased prior to the PME changes and when the PME decreased, the intracellular environment of PME recovered to the same state before the therapy. It was considered that the TR10/TR2 ratio of PME offers significant information different from the PME/ATP ratio. It is possible to use the TR10/TR2 ratio as a predicting index for the therapeutic effects.

[Antitumor activities of orally administered 7-con-0-methylnogarol (TUT-7)]

We estimated antitumor activity of TUT-7 following p.o. administration using animal tumor models and human tumor xenografts. In mouse L 1210 leukemia system, antitumor activity of TUT-7 administered orally was as good as that by i.v. administration. Treatment involving schedules of every 4-days or daily administration was much more effective than single treatment. Therapiotic indices of this compound administered both p.o. or i.v. routes, were better than that of adriamycin administered i.v.. TUT-7 showed antitumor activities against various mouse tumors (L 1210 leukemia, P 388 leukemia, colon 38 adenocarcinoma, B 16 melanoma), LX-1 human tumor xenografts, and Yoshida sarcoma in rat. Base on above results, we concluded that oral administration is one of the useful route of TUT-7 administration.

Synthesis, characterization and anti-tumour testing of some platinum(II) amine complexes containing 1,1- and 1,2-cyclobutanedicarboxylate ligands

A series of new platinum(II) amine complexes containing 1,1- and 1,2-cyclobutanedicarboxylate ligands, cis-[PtA2(1,1-CBDCA)] (A = RNH2, where R = C2H5, n-C3H7, n-C4H9, n-C5H11, n-C6H13, c-C3H5, c-C5H9, c-C6H11; A2 = ethylenediamine, 1,3-diaminopropane), cis-[PtA2(1,2-CBDCA)] (A = NH3, RNH2 where R = CH3, C2H5, n-C3H7, n-C4H9, c-C3H5) and trans-[Pt(NH3)2(1,1-CBDCAH)2] (CBDCA, CBDCAH = dianion and monoanion of the dicarboxylic acid, respectively) have been synthesized by an improved route. These complexes are stable in aqueous solution and show good aqueous solubility. The [Pt(c-C3H5NH2)2(1,1-CBDCA)] can be isolated in white, grey and blue forms. The grey and blue forms exhibit ESR signals analogous to the so-called platinum blues. The existence of the blue form in aqueous solution is time and temperature dependent. Several of the complexes have been tested against leukaemia L1210 in male BDF mice and activity appears to decrease with the increase in length of the aliphatic chain (or increase in size of the alicyclic ring) of the primary amine. The Yoshida lymphoscarcoma screen, usually insensitive to platinum drugs, was found to respond well to [Pt(n-C4H9NH2)2(1,1-CBDCA)] in 5-day subcutaneously implanted tumours in female Wistar rats.

[Synthesis and antitumor action of N,N-di(2-chlorethyl)-hydrazines of alpha-aminocarboxylic acid antimetabolites]

The N,N-di(2-chlorethyl)hydrazides of the following alpha-aminocarboxylic acid antimetabolites: methioninsulphoxide, ethionine, 2-, 3- and 4-fluorophenylalanine, 4-nitrophenylalanine and 2,2-dimethyl-thiazolidine-4-carboxylic acid were synthesized. Preliminary studies of the activity on experimental tumour models were carried out. It was shown that these compounds have a high antitumour effect (80-100%) on sarcoma Yoshida and carcinosarcoma Walker.