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PubMedDate not supplied

Development of differential cytotoxic compounds containing nitrosourea and benzothiazine nucleus.

The in vivo activity of 4 new benzothiazinyl-nitrosourea compounds was investigated against Sarcoma-180 (S-180) and Ehrlich Ascitic Carcinoma (EAC) induced ascitic and solid tumors. EAC solid tumor was found to be the most sensitive, where one compound (no 4) inhibited tumor growth to only 3 per cent of the control value. All the 4 compounds tested were found to be toxicologically more selective than 5-fluorouracil and 6-mercaptopurine drugs. The reason for this selective toxicity may be attributed to the inhibition of isocyanate moiety in these compounds which causes toxicity to normal cells via a carbamoylation reaction. However, they may still remain potent, since they decompose into an alkylating carbonium species and a charge transfer complex which may interact with DNA via alkylation and intercalation reactions, respectively.

Animals↗
PubMed1975

Studies on recovery from chemically induced damage in mammalian cells.

The survival of plateau-phase or nondividing Chinese hamster ovary cells (in vitro) is reduced to a greater extent by treatments with nitrosourea compounds than are cells treated in the exponential phase of growth. The greatest decrease in the survival fraction occurred following treatments with 1-trans-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea where approximately 128 times more cells were killed in plateau phase than in the dividing state (at the 10 mug/ml-for-1-hr dose). Only 5 times more cells were killed in plateau phase than in exponential growth when cells were treated with 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. Cells treated with either nitrosourea compound failed to recover from potentially lethal damage and sublethal damage. The breakdown products of the nitrosourea compounds are known to inhibit DNA repair and may explain the failure of mammalian cells to recover from sublethal damage and potentially lethal damage induced by these chemicals. Both dividing and nondividing cells were able to recover from bleomycin-induced potentially lethal damage but not from sublethal damage. The recovery from bleomycin-induced potentially lethal damage by nondividing cells was twice as great as that exhibited by dividing cells; however, potentially lethal damage recovery was suffieiently high for cells in both growth states to conceal the true response to sublethal damage.

Animals↗
PubMed1982

PCNU: a new nitrosourea in clinical oncology.

PCNU is a new nitrosourea compound which has recently entered clinical trials. Preclinically it has been found to be effective against a variety of tumor models. Biochemically, PCNU was found to have optimal lipophilic, alkylating, and carbamoylating properties as compared to other nitrosourea agents. PCNU is able to diffuse into the CSF as demonstrated by pharmacokinetic studies. Clinical phase I studies indicate that the main toxicity is myelosuppression; nausea and vomiting were less frequently observed with PCNU than with other nitrosourea compounds. Human antitumor activity has been reported in a number of tumors, but most consistently in brain tumors. Phase II studies are now underway to confirm the antitumor activity of PCNU.

Animals↗
PubMed1983

[ACNU delivery to malignant tumor tissue and serum--route of administration and combined use of phenobarbital].

Since nitrosourea compounds as chemotherapeutic agent can cross the blood brain barrier, they are widely used in the treatment of malignant brain tumors. ACNU (3-[(4-amino-2-methyl-5-pyrimidinyl) methyl]-1-(2-chloroethyl)-1-nitrosourea hydrochloride) has become a popular agent, as it is water-soluble and has shown potent effectiveness for treating gliomas. Only a few studies have ever been reported concerning the pharmacokinetics of ACNU in human brain tumors. Intra-arterial administration of chemotherapeutic agents has recently been paid special attention, because it is expected to be more effective than intravenous administration. On the other hand, phenobarbital as an anticonvulsant, widely used in clinical management of malignant brain tumor patients has been reported to reduce the toxicity of nitrosourea compounds by induction of hepatic microsomal enzyme relating to their metabolism. In this report, malignant brain tumor patients were divided into two groups; ACNU was administered either by internal carotid or intravenous route. ACNU concentrations in blood or tumor tissue following the administration were serially compared between these two groups. Patients were also divided into another two groups; ACNU was administered in combination with or without phenobarbital. Between these two groups, ACNU in concentrations in blood were serially compared in order to detect the influence of phenobarbital. ACNU concentrations in tumor tissues were measured at 5, 10, 15, 20, 25, 30, (40, 45, 50), 60 minutes after intravenous (IV) or internal carotid arterial (ICA) administration of ACNU (2-3 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

Clinical toxicity of combined modality treatment with nitrosourea derivatives for central nervous system tumors.

Two nitrosourea compounds--1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)--have been used in the treatment of primary and metastatic brain tumors after operation and/or radiotherapy. Hematological and nonhematological toxicity were recorded in 272 patients treated between May 1973 and June 1978. BCNU was given to 135 patients (80 mg/m2 i.v. daily for 3 days) and CCNU was given to 137 patients (130 mg/m2 orally, single dose) every 8 weeks until progression of the primary disease process or for a total of 12 cycles. Radiation therapy (5500 +/- 500 rads in 6 to 7 weeks) was carried out after the first course of chemotherapy. BCNU and CCNU induced the same hematological and clinical toxicity. The bone marrow toxicity seemed to be dose-related, delayed, and cumulative. One case of acute nonlymphoblastic leukemia arising 2 months after the end of CCNU therapy is reported.

Bone Marrow Diseases↗
PubMedDate not supplied

MGMT- and P450 3A-inhibitors do not sensitize glioblastoma cell cultures against nitrosoureas.

UNLABELLED: AIM, MATERIAL AND METHODS: Using RT-PCR and immunohistochemistry the expression of cytochrome P450 was evaluated in a series of 22 glioblastomas and 4 anaplastic astrocytomas (WHO grade III). Since rat liver P450 can catalyze the denitrosation of the nitrosourea compound BCNU in vitro, cell culture experiments were performed to test a possible sensitizing effect of P450 3A inhibitors (tiamulin and ketoconazole) in BCNU treatment of glial tumor cells. O6-benzylguanine (BG), an inhibitor of the DNA repair enzyme O6-methylguanine-DNA-methyltransferase (MGMT), was used in parallel experiments, since MGMT is discussed as a main mechanism in nitrosourea resistance. RESULTS: RT-PCR reactions with primers designed according to the sequences for CYP1A1 and CYP2E1 were always positive, while those for CYP1A2 and CYP2D6 were negative. The strongest PCR products were detected with CYP3A primers, but CYP3A expression was heterogeneous within the tumor samples. Antibodies to human liver CYP3A4 stained a subfraction of tumor cells (18% of the cells in glioblastomas and 14% in grade III astrocytomas) and to some extend neurons in normal brain areas, while astrocytes were negative. For cell culture experiments with P450 3A and MGMT inhibitors, early passages of 3 glioblastomas, a late passage of an immortalized cell line derived from a reoccurring glioblastoma, and the human glioblastoma line LN405 were used. The sensitivity of the tumor cells for both nitrosourea compounds was very low, when low concentrations were applied (comparable to the achievable blood concentrations in glioma patients). Strong effects did only occur when the concentrations were raised 9-fold or 27-fold. CONCLUSION: In no case could a significant sensitizing effect of P450 3A- and MGMT inhibitors be demonstrated.

Antineoplastic Agents↗
PubMed1995

Quantitative DNA analysis of an intracerebrally transplanted brain tumour model after experimental chemotherapy with BCNU and CCNU.

In the present study we investigated the susceptibility of high passages of the rat glial transplantation tumour G-XIII to chemotherapy using nitrosourea compounds. We observed a significant increase in lifespan (ILS) of animals treated with BCNU (37%, p < 0.01) and CCNU (27%, p < 0.01). There were no difference in the efficiency between these two substances. Using a semi-quantitative score system no histopathological changes were observed which were associated with the response to therapy. The only predicative parameter in the present study was the quantitative DNA distribution pattern. There was a close correlation between treatment and the occurrence of unimodal DNA distribution patterns indicating clonal regrowth of recurrent tumours. Moreover, we also observed a correlation of the DNA distribution pattern of recurrent tumours with the result of experimental chemotherapy. Survival times of animals suffering from tumours containing unimodal DNA histogram was significantly longer than survival times of rats with multimodal DNA distribution, i.e. bimodal or broad DNA histograms. A unimodal, near-diploid stem line was only present in treated animals suggesting that these clones are more resistant against therapy using nitrosourea compounds. Our data indicate DNA cytophotometry as comprehensive tool for the monitoring of therapy response and the design of experimental chemotherapy using rat glial tumours.

Animals↗
PubMed1977

Antitumor effect of 1,1'-polymethylene-bis (1-nitrosourea) and related compounds.

Polymethylene-bis(1-nitrosourea), polymethylene-bis(1-nitroso-3-nitroguanidine), and polymethylene-bis(1-nitroso-p-toluenesulfonamide) derivatives were tested for antitumor effect against rat ascites hepatoma AH-13 and mouse leukemia L-1210. Bisnitrosoureas were effective against AH-13 and L-1210, bisnitrosoguanidines were effective against AH-13 alone, and bisnitrosotoluene-sulfonamides were ineffective against both tumor lines. Of all these compounds, 1,1'-ethylene-bis(1-nitrosourea) (EBNU) was the most effective. The antitumor effect of EBNU was compared with that of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). Intraperitoneal administration of EBNU according to the schedule, day 1, days 1 and 5, and days 1, 5, and 9 after intraperitoneal inoculation of L-1210 showed marked prolongation of host survival, although the effective doses used were a few times higher than those used in BCNU to obtain a similar effect. The minimum effective dose (MED) of EBNU on AH-13 cells was estimated as 1 mg/kg, which was 10 times less than that of BCNU, suggesting that EBNU was more effective than BCNU against AH-13.

Animals↗
PubMed1987

Influence of modes of ACNU administration on tissue and blood drug concentration in malignant brain tumors.

The water-soluble nitrosourea compound ACNU is also lipid-soluble at normal physiological pH levels. It lacks toxic effects on vision that nitrosoureas occasionally produce following intra-arterial administration. In 28 cases of both primary and secondary malignant brain tumors, ACNU was administered at surgery or angiography by three different modes: intravenous injection in Group I (10 cases), intra-arterial injection via the carotid artery in Group II (11 cases), and intra-arterial injection via the carotid artery after opening the blood-brain barrier (BBB) by means of mannitol in Group III (seven cases). Tumor tissue and blood samples were taken serially at various time intervals after ACNU injection, and ACNU was measured by high-performance liquid chromatography. The time-concentration curve for ACNU was calculated in each case by the two- and one-compartment open models for determination of ACNU levels in blood and tissue, respectively. Pharmacokinetic parameters including biological half-life, blood and tissue levels (0-t minutes and 0-infinity minutes), total plasma clearance, and distribution volume of the beta phase were compared. Statistical analysis of tissue ACNU levels at 0-t minutes revealed higher concentrations in Group III patients than in Groups II and I: levels in Group II were significantly higher than in Group I. Mean biological half-life was 30.3, 23.0, and 38.5 minutes in Groups I, II, and III, respectively. Levels of ACNU were significantly increased in tumor tissue as well as in peritumoral tissue in one Group III patient with multiple metastatic anaplastic adenocarcinoma. In this series, treatment of malignant brain tumor by intra-arterial administration of ACNU produced significantly higher tissue levels of ACNU than did the systemic intravenous route.

Adenocarcinoma↗
PubMed1989

Damage to DNA strand and the effects of anticancer drugs.

Cancer chemotherapy is, in a sense, similar to the treatment of infectious disease with antibiotics. The main mechanism of action is on DNA and its precursor, and in the process that anticancer drugs exert the effect on cancer cells, the cells always have abnormal metabolism or destruction of DNA. The main cellular target of most alkylating agents, or anticancer antibiotics is DNA, however, among the anticancer drug newly synthesized, there are some compounds which exert the action on DNA. Quinocarmycin, KT6149, which is a derivative of MMC, YM534, which possesses a platelet agglutinating activity, and MCNU, a nitrosourea compound were studied on the anticancer activity and on damage to DNA strand, and it was found that the lethal effect was deeply concerned with single strand scission of DNA.

Antineoplastic Agents↗
PubMed1980

Chemotherapy of pediatric posterior fossa tumors.

Results of chemotherapy of recurrent posterior fossa tumors in children are presented. Cerebellar astrocytoma, ependymoma, and brain stem glioma have all shown objectively determined responses to treatment with nitrosourea compounds (BCNU or CCNU). Medulloblastoma has shown objectively determined response to various chemotherapeutic agents; but in our experience the best responses have been obtained with a combination of a nitrosourea (CCNU), vincristine, and procarbazine. Although chemotherapy after recurrence has significantly prolonged the life of the patients, cure has not been achieved. Theoretical considerations regarding the failure of initial therapy and the inadequacy of subsequent chemotherapy are discussed.

Astrocytoma↗
PubMed1983

[Effects of phenobarbital on the metabolism of ACNU in vivo].

The nitrosourea compounds are often used in the treatment of patients with malignant brain tumors in combination with anticonvulsants, such as phenobarbital (PB). Since PB can induce hepatic microsomal enzyme--P 450 and degrade nitrosoureas in vivo, the effect of PB on tumoricidal activity in relation to toxicity of 3-[(4-amino-2-methyl-5-pyrimidinyl)-methyl]-1-(2-chloroethyl)-1-nitrosourea (ACNU) was studied using a rat brain tumor model. To determine toxicity, CD-Fisher rats were treated for 4 days with 19 and 38 mg/kg/day of PB (i.m), 0.4 and 0.7 g/kg/day of sodium valproate--SV (p.o), or 3 days with 50 mg/kg of phenytoin (i.v) prior to an administration of 47 mg/kg of ACNU (i.p). The mortality rate by the toxicity within 14 days after administration of ACNU was calculated in each group. The toxicity of ACNU was markedly reduced in PB pretreated rats compared with those without pretreatment or treated with SV or phenytoin. The tumoricidal activity of ACNU was evaluated in CD-Fisher rats with RG 12 brain tumors. Rats received 20 mg/kg ACNU after pretreatment with 19 mg/kg/day of PB (i.m) or 0.2 g/kg/day of SV (p.o) for 4 days. The mean survival days and the percentage increase in life span (%ILS) were compared in each group. Pretreatment with PB significantly reduced the tumoricidal activity of ACNU as compared with control without pretreatment (p less than 0.001) or pretreatment with SV (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Sensitivity difference of rat ascites hepatoma AH-13 and mouse leukemia L-1210 to nitrosourea derivatives.

The structure-activity relationship in different sensitivity of AH-13 and L-1210 to nitrosourea nad related derivatives was examined. N-Methyl-N-nitrosoureido derivatives, such as 1-methyl-1-nitrosourea (MNU) and 1, 1'-polymethylene-bis(3-substituted 3-nitrosourea), were inactive against AH-13 and slightly active against L-1210. On the contrary, 1, 1'-polymethylene-bis(3-substituted 1-nitrourea) derivatives were more active against AH-13 than against L-1210. The nitrosoureas which had bis(2-chloroethyl) group at the terminal were highly active against AH-13 and L-1210. One of denitrosated derivatives, 1, 1'-ethylene-bis[3-(2-chloroethyl)urea], was active against AH-13 alone. In addition, diisocyanates, nitrourea, ammonium carbamate, and 1-methyl-1-nitrourea, which are related to the nitrosourea compounds, were also tested for their activity against AH-13 and L-1210. Diisocyanates and nitrourea were active against AH-13 alone, while other compounds were all inactive.

Animals↗
PubMed1985

Decomposition reactions of (hydroxyalkyl) nitrosoureas and related compounds: possible relationship to carcinogenicity.

(Hydroxyalkyl)nitrosoureas and the related cyclic carbamates N-nitrosooxazolidones are potent carcinogens. The decompositions of four such compounds, 1-nitroso-1-(2-hydroxyethyl)urea (I), 3-nitrosooxazolid-2-one (II), 1-nitroso-1-(2-hydroxypropyl)urea (III), and 5-methyl-3-nitrosooxazolid-2-one (IV), in aqueous buffers at physiological pH were studied to determine if any obvious differences in decomposition pathways could account for the variety of tumors obtained from these four compounds. The products predicted by the literature mechanisms for nitrosourea and nitrosooxazolidone decompositions (which were derived from experiments at pH 10-12) were indeed the products formed, including glycols, active carbonyl compounds, epoxides, and, from the oxazolidones, cyclic carbonates. Furthermore, it was shown that in pH 6.4-7.4 buffer epoxides were stable reaction products. However, in the presence of hepatocytes, most of the epoxide was converted to glycol. The analytical methods developed were then applied to the analysis of the decomposition products of some related dialkylnitrosoureas, and similar results were obtained. The formation of chemically reactive secondary products and the possible relevance of these results to carcinogenesis studies are discussed.

Animals↗
PubMed1982

5-Fluorouracil, 1,3-bis(2-chloroethyl)-1-nitrosourea, and 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea: effect on the human granulopoietic system.

The reaction pattern of the normal (nonleukemic) human granulopoietic system to single-agent treatment with 5-fluorouracil (FUra) and to a combination of FUra with two nitrosoureas, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU), was studied serially by morphologic and in vitro culture methods. The granulopoietic toxicity of FUra was acute and rapidly (by day 21) reversible. In contrast, the toxicity of the combination regimens was long lasting. Evidence exists that an early toxicity (that of FUra) and a delayed toxicity (that of the nitrosourea) were overlapping. Toxicity of BCNU and MeCCNU was most pronounced at the level of in vitro colony-forming units of the granulopoietic system (G-CFUc). G-CFUc compartments of bone marrow and peripheral blood continued to be reduced in size at the time of recovery of the peripheral blood granulocyte count from nitrosourea-induced toxicity. This finding may be responsible for the cumulative toxicity to the human hematopoietic system that frequently has been observed after repeated administration of nitrosourea compounds.

Adult↗
PubMed1988

Increased O6-methylguanine-DNA methyltransferase activity and reduced mutability in 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2- chloroethyl)-3-nitrosourea-resistant HeLa S3 cells.

To clarify the involvement of O6-methylguanine (O6-MeG) in mutagenesis, we have been trying to isolate Mer+ cells from a HeLa S3 Mer- cell line, and to compare the mutation frequencies between the cell lines. We previously isolated the N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-resistant cells, MR10-1, from HeLa S3 Mer- cells. However, the MR10-1 cells still had only a little O6-MeG-DNA methyltransferase (MT) activity. In the present study, we have isolated two 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU)-resistant cells, ACr41 and ACr42, from the MR10-1 cells. The two ACr cells had increased MT activities. The ACr cells were also significantly more resistant to 1-(2-chloroethyl)-1-nitrosourea and slightly more resistant to MNNG than the MR10-1 cells. When the mutation frequencies were tested at the hypoxanthine-guanine phosphoribosyl transferase and ouabain loci in these cell lines, the two ACr cells were more resistant to the mutagenic effect of MNNG than the MR10-1 cells. These results show the linkage between the resistance to the cytotoxic effect of nitrosourea compounds and MT activity, and strongly support the hypothesis that O6-MeG is the main pre-mutagenic lesion induced by MNNG.

Antineoplastic Agents↗
PubMed1979

A simple method for producing different growth fractions in vitro for use in anti-cancer drug studies.

A simple technique has been used experimentally to produce in vitro Chinese hamster ovary cells with growth fractions ranging from 0 to 100%. Known numbers of exponentially growing and plateau-phase tissue culture cells were mixed in various proportions to yield the desired final growth fraction. Cells attach to the culture flask surface within 1 hr of mixing. Treatment at that time with the nitrosourea compounds, CCNU and MeCCNU, resulted in differential drug survival sensitivities that were dependent upon the growth fraction of the population treated.

Animals↗