Toxicity and efficacy of lomustine and bevacizumab in recurrent glioblastoma patients

The combination of lomustine and bevacizumab is a commonly used salvage treatment for recurrent glioblastoma (GBM). We investigated the toxicity and efficacy of lomustine plus bevacizumab (lom-bev) in a community-based patient cohort and made a comparison to another frequently used combination therapy consisting of irinotecan plus bevacizumab (iri-bev). Seventy patients with recurrent GBM were treated with lomustine 90 mg/m² every 6 weeks and bevacizumab 10 mg/kg every 2 weeks. Toxicity was registered and compared to the toxicity observed in 219 recurrent GBM patients who had previously been treated with irinotecan 125 mg/m² and bevacizumab 10 mg/kg every 2 weeks. The response rate was 37.1% for lom-bev and 30.1% for iri-bev. Median progression-free survival (PFS) was 23 weeks for lom-bev and 21 weeks for iri-bev (p = 0.9). Overall survival (OS) was 37 weeks for lom-bev and 32 weeks for iri-bev (p = 0.5). Lom-bev caused a significantly higher frequency of thrombocytopenia (11.4% grade 3-4) compared to iri-bev (3.5% grade 3-4). Iri-bev patients had more gastrointestinal toxicity with regard to nausea, vomiting, diarrhea, constipation and stomatitis. Within the limitations of the study lom-bev is a well-tolerated treatment for recurrent GBM, although hematological toxicity may be a dose limiting factor. No significant differences between lom-bev and iri-bev were observed with regard to PFS or OS. The differences in toxicity profiles between lom-bev and iri-bev could guide treatment decision in recurrent GBM therapy as efficacy is equal and no predictive factors for efficacy exist.

Estrogen and soy isoflavonoids decrease sensitivity of medulloblastoma and central nervous system primitive neuroectodermal tumor cells to chemotherapeutic cytotoxicity

BACKGROUND

Our previous studies demonstrated that growth and migration of medulloblastoma (MB), the most common malignant brain tumor in children, are stimulated by 17β-estradiol. The growth stimulating effects of estrogens are mediated through ERβ and insulin-like growth factor 1 signaling to inhibit caspase 3 activity and reduce tumor cell apoptosis. The objective of this study was to determine whether estrogens decreased sensitivity of MB cells to cytotoxic actions of chemotherapeutic drugs.

METHODS

Using in vitro cell viability and clonogenic survival assays, concentration response analysis was used to determine whether the cytoprotective effects of estradiol protected human D283 Med MB cells from the cytotoxic actions of the MB chemotherapeutic drugs cisplatin, vincristine, or lomustine. Additional experiments were done to determine whether the ER antagonist fulvestrant or the selective ER modulator tamoxifen blocked the cytoprotective actions of estradiol. ER-selective agonists and antagonists were used to define receptor specificity, and the impacts of the soy-derived phytoestrogens genistein, daidzein, and s-equol on chemosensitivity were evaluated.

RESULTS

In D283 Med cells the presence of 10 nM estradiol increased the IC50 for cisplatin-induced inhibition of viability 2-fold from ~5 μM to >10 μM. In clonogenic survival assays estradiol decreased the chemosensitivity of D283 Med cells exposed to cisplatin, lomustine and vincristine. The ERβ selective agonist DPN and low physiological concentrations of the soy-derived phytoestrogens genistein, daidzein, and s-equol also decreased sensitivity of D283 Med cells to cisplatin. The protective effects of estradiol were blocked by the antiestrogens 4-hydroxytamoxifen, fulvestrant (ICI 182,780) and the ERβ selective antagonist PPHTP. Whereas estradiol also decreased chemosensitivity of PFSK-1 cells, estradiol increased sensitivity of Daoy cell to cisplatin, suggesting that ERβ mediated effects may vary in different MB celltypes.

CONCLUSIONS

These findings demonstrate that E2 and environmental estrogens decrease sensitivity of MB to cytotoxic chemotherapeutics, and that ERβ selective and non-selective inhibition of estrogen receptor activity blocks these cytoprotective actions. These findings support the therapeutic potential of antiestrogen adjuvant therapies for MB, and findings that soy phytoestrogens also decrease sensitivity of MB cells to cytotoxic chemotherapeutics suggest that decreased exposure to environmental estrogens may benefit MB patient responses to chemotherapy.

Effect of the spin-labelled 1-ethyl-1-nitrosourea on CCNU-induced oxidative liver injury

This study was carried out to determine the effects of 1-ethyl-3-[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)]-l-nitrosourea (SLENU), recently synthesised in our laboratory, and vitamin E as positive control on 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) - free radical induced oxidative injuries in the liver of mice. Specifically, alterations in malonyl dialdehyde (MDA) level and activities of some antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), were measured in liver homogenates from tumour-bearing C57 black mice after treatment with solutions of CCNU (30 mg/kg) and SLENU (100 mg/kg), both administered intraperitoneally. CCNU-induced increase in MDA level, SOD and CAT activities were suppressed by SLENU. The present results and those from a previous report demonstrated superoxide scavenging activities (SSA) of the nitrosourea SLENU and enabled us explain the protective effect of the spin-labelled nitrosourea on CCNU-induced oxidative stress in the liver of mice. This protective effect is through the scavenging of *O2- and by an increased production of *NO. Thus, a potential for developing new combination chemotherapy in cancer is seen.

MOPPEBVCAD Chemotherapy with Limited and Conditioned Radiotherapy in Advanced Hodgkin's Lymphoma: 10-Year Results, Late Toxicity, and Second Tumors

PURPOSE

MOPPEBVCAD (mechlorethamine, vincristine, procarbazine, prednisone, epidoxirubicin, bleomycin, vinblastine, lomustine, doxorubicin, and vindesine) chemotherapy with limited radiotherapy was devised in 1987 to reduce late toxicity and second tumor incidence while trying to improve effectiveness through increases of dose intensity and dose density. Late results, toxicity, and second tumor incidence were reviewed in all the patients treated.

EXPERIMENTAL DESIGN

The drugs of three previous alternating regimens [CAD (lomustine, melphalan, and vindesine), MOPP (mechlorethamine, vincristine, procarbazine, and prednisone), and ABV (doxorubicin, bleomycin, and vinblastine)] were intensified and hybridized, the cumulative dose of mechlorethamine was lowered, and irradiation was delivered to no more than two sites either bulky or partially responding to chemotherapy.

RESULTS

A total of 307 previously untreated advanced-stage patients underwent MOPPEBVCAD chemotherapy. Radiotherapy was delivered to 118 of 307 patients (38%). Remission was complete in 290 patients (94%). With a median follow-up of 114 months, 10-year overall, disease-free, and failure-free survival rates were 79%, 84%, and 71%, respectively. Forty-two patients relapsed and 60 died. The causes of death were Hodgkin's lymphoma in 36 patients, second neoplasms in 12, cardiorespiratory diseases in 4, pulmonary diseases in 2, and unknown in 6. Sixteen second tumors (of which nine were myelodysplasia and/or acute leukemia) were diagnosed in all. Outside this series of 307 patients, MOPPEBVCAD obtained complete responses in 12 of 15 relapsed and 9 of 9 refractory patients who had previously been treated with other regimens.

CONCLUSIONS

Clinical response and long-term results are very satisfactory, whereas the second tumor incidence was lower than would have been expected with MOPP analogues. Given its response/late toxicity balance, MOPPEBVCAD does not undermine the leading role of ABVD as first-line regimen but can be indicated as a very effective second-line conventional therapy.

The toxicological study of CCNU controlled release film in vivo

We planted the Lomustine (CCNU) controlled release films into normal mice, and after a period of time observed the effects of the films on the blood cells and the brain nerve cells of the mice. Compared with the traditional administration (PO), the results indicated that the planted CCNU controlled release film had less effects on the blood cells, and caused less harm to the brain nerve cells. So the conclusion was that the planted CCNU controlled release film had no significant acute arrest of bone marrow and neural toxicity.

Spin labeled antioxidants protect bacteria against the toxicity of alkylating antitumor drug CCNU

We have studied the toxic effect of the alkylating antitumor drug N'-cyclohexyl-N-(2-chloroethyl)-N-nitrosourea (lomustine, CCNU) on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) strains, alone and in presence of oxygen radical-scavenging substances [Vitamin E, stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TMPO), and spin labeled (nitroxyl free radical moiety containing) analogues of CCNU] and compared with that of the alkylating antitumor drug 5-(3,3-dimethyltriazene-1-yl)-imidazole-4-carboxamide (dacarbazine, DTIC). All spin labeled compounds tested were almost no toxic at doses of 50-500 microM/ml, whereas the alkylating antitumor drug CCNU showed toxicity in a dose dependent manner. Even low doses of spin labeled nitrosoureas provided protection against the toxicity caused by the antitumor drug CCNU alone. The lowest toxicity against E. coli and S. aureus were achieved when 500 microM/ml of CCNU was combined with 200 microM/ml of spin labeled nitrosourea N-[N'-(2-chloroethyl)-N'-nitrosocarbamoyl]-glycine amid of 2,2,6,6-tetramethyl-4-aminopiperidine-1-oxyl (SLCNUgly). A combination of TMPO with vitamin E completely abolished the toxicity of CCNU. Endogenous formation of oxygen radicals and their possible involvement in CCNU toxicity towards the bacteria strains tested have been also discussed.

Efficacy and toxicity of a CCNU-containing high-dose chemotherapy regimen followed by autologous hematopoietic cell transplantation in relapsed or refractory Hodgkin's disease

High-dose CBV (cyclophosphamide, carmustine, and etoposide) in combination with autologous HCT achieves survival rates of approximately 50% at 5 years in recurrent or refractory Hodgkin's disease (HD). However, carmustine (BCNU) dose-dependent pulmonary toxicity occurs in 20% to 30% of patients. A decreased incidence of interstitial pneumonitis as well as a possible benefit in efficacy has been reported with lomustine (CCNU) compared to BCNU in the standard dose setting. In a dose-escalation study, we substituted CCNU for BCNU in the CBV regimen for 16 patients with HD (n = 12) or non-Hodgkin's lymphoma (n = 4). Based on the promising results, an additional 47 consecutive patients with HD were treated with the following regimen: CCNU (15 mg/kg) orally on day -6, etoposide (60 mg/kg) intravenously on day -4, and cyclophosphamide (100 mg/kg) intravenously on day -2. Peripheral blood progenitor cells and/or bone marrow were infused on day 0. With a median follow-up for the surviving patients of 3.2 years (range, 0.8-9.9 years), the 3-year overall survival rate was 57% (CI, +/-15%), event-free survival was 52% (CI, +/-14%), and freedom from progression was 68% (CI, +/-14%). There were 21 deaths, 10 due to HD. Six patients died due to respiratory failure. Interstitial pneumonitis occurred in 63% of patients and could not be correlated with prior chest radiotherapy. This regimen demonstrated survival rates similar to those of historical studies that used the CBV regimen. However, the incidence of interstitial pneumonitis was in excess of expected.

Protection of hematopoietic cells from O(6)-alkylation damage by O(6)-methylguanine DNA methyltransferase gene transfer: studies with different O(6)-alkylating agents and retroviral backbones

Overexpression of O(6)-methylguanine DNA methyltransferase (MGMT) can protect hematopoietic cells from O(6)-alkylation damage. To identify possible clinical applications of this technology we compared the effect of MGMT gene transfer on the hematotoxicity induced by different O(6)-alkylating agents in clinical use: the chloroethylnitrosoureas ACNU, BCNU, CCNU and the tetrazine derivative temozolomide. In addition, various retroviral vectors expressing the MGMT-cDNA were investigated to identify optimal viral backbones for hematoprotection by MGMT expression. Protection from ACNU, BCNU, CCNU or temozolomide toxicity was evaluated utilizing a Moloney murine leukemia virus-based retroviral vector (N2/Zip-PGK-MGMT) to transduce primary murine bone marrow cells. Increased resistance in murine colony-forming units (CFU) was demonstrated for all four drugs. In comparison to mock-transduced controls, after transduction with N2/Zip-PGK-MGMT the IC50 for CFU increased on average 4.7-fold for ACNU, 2.5-fold for BCNU, 6.3-fold for CCNU and 1.5-fold for temozolomide. To study the effect of the retroviral backbone on hematoprotection various vectors expressing the human MGMT-cDNA from a murine embryonic sarcoma virus LTR (MSCV-MGMT) or a hybrid spleen focus-forming/murine embryonic sarcoma virus LTR (SF1-MGMT) were compared with the N2/Zip-PGK-MGMT vector. While all vectors increased resistance of transduced human CFU to ACNU, the SF1-MGMT construct was most efficient especially at high ACNU concentrations (8-12 microg/ml). Similar results were obtained for protection of murine high-proliferative-potential colony-forming cells. These data may help to optimize treatment design and retroviral constructs in future clinical studies aiming at hematoprotection by MGMT gene transfer.

PCV chemotherapy for recurrent glioblastoma multiforme

The authors evaluated response, time to progression (TTP), survival, prognostic factors, and toxicity in 63 patients with a recurrent glioblastoma multiforme treated with procarbazine, lomustine, and vincristine (PCV) chemotherapy. Complete and partial response was observed in two (3%) and five patients (8%). In 16 patients (25%), stable disease was observed. Median TTP and survival were 13 and 33 weeks. Age < 40 years and Karnofsky Performance Status > or = 90 were associated with longer TTP and survival. PCV treatment was generally well tolerated.

Bleomycin, lomustine, cyclophosphamide, vincristine, procarbazine and prednisone (BLEO-CCVPP) in patients with Hodgkin's disease who relapsed after radiotherapy alone: a long-term follow-up study of the Eastern Cooperative Oncology Group (E3481)

Thirty-three evaluable patients with Hodgkin's disease who failed radiotherapy were treated on this phase II study with bleomycin, lomustine, cyclophosphamide, vincristine, procarbazine and prednisone given every 28 days for a minimum of eight courses. Twenty-five patients (76%; 95% CI=55.6-87.1%) achieved a complete remission, the median duration of which cannot yet be determined, but the probability of remaining in continuous complete remission at 10 years is.64. The median survival from entry on this study for all evaluable patients is 10 years, and 12 patients were alive at the time of this analysis with a median follow-up for them of 15.5 years. Of the 22 patients who died, 11 died of progressive or recurrent Hodgkin's disease and 11 died of other causes including 7 second primary neoplasms and at least one myocardial infarction. Both are now well known late complications of Hodgkin's disease treatment.

OPP-EBV-CAD regimen as salvage treatment in advanced refractory or resistant multiple myeloma

With the aim of developing an effective therapy for heavily pretreated refractory MM outpatients, we evaluated the OPPEBVCAD regimen, a Hodgkin's disease-derived protocol that includes many drugs effective in MM administered in a sequential schedule. Twenty-two pts aged 42-72 years, with symptomatic highly-pretreated refractory (18 cases), or primary resistant MM (four cases. including two pts with plasma cell leukemia-PCL) received this therapy every 28 days (2-4 cycles, followed by a maintenance program). Therapeutic response (Chronic Leukemia-Myeloma Task Force criteria) and performance status (PS) and pain (W.H.O.) were evaluated. All of the pts were evaluable for response. There were 9 (40%) objective responses (OR: stabilization of blood counts and bone lesions, serum calcium normalization, 50% or more reduction in the concentration of serum monoclonal component (MC), 90% reduction in Bence-Jones proteinuria), 8 (36%) partial responses (PR: 25-50% reduction in serum MC), 1 no response or stable disease (NR), and 4 (18%) cases of progressive disease (PD). OR plus PR were 77%. Of the 4 primary resistant tumors (2 PCL and 2 MM), 2 achieved PR, 1 OR (a PCL case) and 1 progressed. Median survival was 15 months for responding pts (OR plus PR) and 4.5 months for non-responders (NR plus PD). PS and pain improved in 15 pts and did not change in 9. The most frequent side effects were cytopenias, with one drug related infective death. The OPPEBVCAD regimen proved to be an effective therapy for refractory relapsing or primary resistant MM: in responders (two-thirds of the pts), survival was prolonged by about 10 months. Its efficacy in anthracycline-treated pts, as well as the feasibility of using it on an outpatient basis without any continuous drug infusions, make this regimen a promising third line salvage therapy.

Lomustine and melphalan cannot be replaced by cyclophosphamide and etoposide without reducing efficacy in MOPPEBVCAD chemotherapy for advanced Hodgkin's disease

BACKGROUND AND OBJECTIVES

To evaluate the feasibility, toxicity and preliminary results of a potentially less toxic variant of the MOPPEBVCAD chemotherapy regimen for advanced Hodgkin's disease: MOPPEBVCyED, in which cyclophosphamide and etoposide replace lomustine and melphalan, respectively, with the remaining components being unaltered.

DESIGN AND METHODS

The study was multicenter, prospective and randomized, and enrolled 67 patients with newly diagnosed stage IIB, III, IV Hodgkin's disease (62 were expected on the grounds of statistical considerations). Radiotherapy was restricted to sites of bulky involvement or to areas that responded incompletely to chemotherapy. Median follow-up was 48 months.

RESULTS

Comparing MOPPEBVCAD vs. MOPPEBVCyED, the results were as follows: complete remissions 35/35 vs. 30/32 (plus one partial remission and one disease progression); relapses 5 vs. 8; deaths 2 (one of myelodysplasia) vs. 2; delivered mean dose intensity (DI): lomustine 0.79+/-0.67 vs. cyclophosphamide 0.82+/-0.32; melphalan 0.80+/-0.13 vs. etoposide 0.86+/-0.18; average DI of the 7 drugs common to both regimens 0.73+/-0.10 vs. 0.83+/-0.11; all 9 drugs 0.75+/-0.13 vs. 0.84+/-0.09 (p=0.002); projected 5-year failure-free survival 0.79 vs 0.62; second cancers, two myelodysplasias vs. one carcinoma of the kidney. Toxicities were not statistically different except for heavier thrombocytopenia being recorded with MOPPEBVCAD.

INTERPRETATION AND CONCLUSIONS

The higher cumulative and single drug DI recorded with MOPPEBVCyED may reflect better short-term tolerability, but it does not lead to better disease control. Its late toxicity may be expected to be lower in the future but at present it does not seem to be a sufficient reason to substitute MOPPEBVCyED for MOPPEBVCAD.

Sensitivity to DNA cross-linking chemotherapeutic agents in mismatch repair-defective cells in vitro and in xenografts

Together with tolerance to killing induced by methylating agents, loss of mismatch repair (MMR) has previously been found to be associated with hypersensitivity to the DNAcross-linking agent 1-(2-chloroethyl)-3-cyclohexyl-nitrosourea(CCNU) in several human tumor cell lines (Aquilina et al., 1998). Here, we have investigated whether MMR might act as an efficient repair pathway and provide protection against the clastogenicity induced by CCNU and whether the hypersensitivity of MMR-defective cells is extended to other cross-linking agents. An increase in cell killing and in the frequency of micronuclei was observed after CCNU exposure in 2 hPMS2-defective clones (clones 6 and 7) compared with the parental HeLa cells. Introduction of a wild-type copy of chromosome 7 in clone 7 led to re-expression of the hPMS2 protein and brought survival and chromosomal damage upon CCNU exposure to parental levels. Our data indicate that MMR protects against the clastogenic damage induced by this drug. The hPMS2-defective HeLa cells were also hypersensitive to killing by mitomycin C. Mitomycin C sensitivity was confirmed in an hMLH1-defective clone derived from Raji cells and in msh2-defective mouse embryo fibroblasts derived from knock-out mice. hPMS2-defective and parental HeLa cells were transplanted into nude mice, and the animals were treated with mitomycin C. While parental cell growth rate was unaffected, the growth of MMR-defective tumor was significantly reduced. Our results indicate that the in vitro hypersensitivity to mitomycin C conferred by loss of MMR is paralleled in vivo and may have implications for the chemotherapy of MMR-defective tumors.

Mismatch repair and p53 independently affect sensitivity to N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea

The contributions of defective mismatch repair (MMR) and the p53-response to cell killing by N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU) were evaluated. MMR defects were previously shown to be associated with CCNU sensitivity (G. Aquilina et al., Cancer Res., 58: 135-141, 1998). Unexpectedly, eight MMR-deficient variants of the A2780 human ovarian carcinoma cell line were 3-fold more resistant to CCNU than the MMR-proficient parental cells. The variants were members of a preexisting subpopulation of drug-resistant A2780 cells. In addition to deficient expression of the MMR protein hMLH1, an essential component of the hMutL alpha repair complex, the variants exhibited alterations in the expression of other genes that influence drug sensitivity. Although A2780 cells possess a wild-type p53 gene, all of the clones contained a heterozygous G to T tranversion at codon 172. This change resulted in a Val to Phe substitution and was associated with a constitutive production of high levels of p53, which was inactive as a transcriptional activator of bax and p21. The hMLH1/p53 defective variants displayed a less prominent cell cycle arrest and reduced apoptosis after CCNU treatment. In contrast, MMR-defective A2780 variants, which had a similar hMutL alpha defect but retained a wild-type p53, did exhibit the expected CCNU sensitivity. Expression of a dominant-negative p53val135 increased CCNU resistance of both MMR-proficient and MMR-deficient A2780 cells. Thus, defective MMR and p53 influence CCNU sensitivity in opposite directions. Their effects are independent, and sensitization by defective MMR does not require a functional p53 response.

Role of O6-methylguanine-DNA methyltransferase in the resistance of pancreatic tumors to DNA alkylating agents

Pancreatic adenocarcinomas rarely respond to radiation or chemotherapy, indicating that a large percentage of these tumors possess complex mechanisms of resistance. The failure of alkylating agents, such as carmustine [1,3-bis(2-chloroethyl)-1-nitrosourea; BCNU], lomustine [1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea; CCNU], and streptozotocin, to yield consistent therapeutic results further suggests that one of these mechanisms may be the high expression of O6-methylguanine-DNA methyltransferase (MGMT). All 12 human pancreatic ductal adenocarcinomas assayed for MGMT activity showed unusually high levels, implying that these malignancies are efficient in repairing genotoxic O6-alkylguanine lesions induced by methylating (streptozotocin) and 2-chloroethylating (BCNU and CCNU) chemotherapeutic genotoxic agents. Immunohistochemical analysis of an additional 15 pancreatic tumors showed that high levels of MGMT protein reside in the nucleus and the cytoplasm of malignant cells. Both nuclear and cytoplasmic staining were absent in hyperplastic duct epithelium, but staining was invariably present in moderate to highly dysplastic foci and especially strong in invasive components of the tumor. With the exception of lymphocytes that were MGMT positive, acinar, ductal, and islet cells did not stain for MGMT in histologically normal pancreata. These data indicate that MGMT activity is up-regulated in dysplastic epithelium, and its expression increases during tumor progression, reaching the highest levels in the invasive components of the tumor. Resistance of pancreatic tumor cells to alkylating agents was verified with four pancreatic tumor cell lines. CAPAN-2, CFPAC-1, PANC-1, and MIAPaCa-2, having MGMT levels of 1800, 987, 700, and 880 fmol/mg protein, respectively, were resistant to BCNU, but their resistance declined sharply following pretreatment with the MGMT inhibitor O6-benzylguanine (O6-BG). On the other hand, PANC-1 and MIAPaCa-2 could not be eradicated with N-methylnitrosourea (MNU) at concentrations as high as 2 mM, even when pretreated with O6-BG. These two lines were shown to be modified genetically in microsatellite sequences by MNU and are believed to have a defective mismatch repair system, which may explain their resistance to methylating agents. Failure of pancreatic tumors to respond to nitrosoureas is related to high levels of MGMT expression and in some cases to genomic instability. However, these tumors can be sensitized to chloroethylating drugs and eradicated following the elimination of MGMT activity by O6-BG or homologous MGMT inhibitors.

Induction of specific-locus and dominant lethal mutations in male mice by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)

1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) induced dominant lethal and specific-locus mutations in male mice. For both compounds the germ cell stage sensitive to the induction of dominant lethal mutations was dose dependent. A dose of 5 mg BCNU per kg b.wt. induced dominant lethal mutations primarily in spermatocytes, whereas higher doses of BCNU induced dominant lethals in spermatids and spermatocytes. Following doses of 5 and 10 mg CCNU per kg b.wt. dominant lethals were induced in spermatids and spermatocytes similar to the results for higher doses of BCNU. Higher dose exposure to BCNU and CCNU was associated with dominant lethals expressed as pre-implantation loss (reduction in total number of implants). In addition, higher doses of CCNU showed a cytotoxic effect in differentiating spermatogonia. Both compounds induced specific-locus mutations in post-spermatogonial germ cell stages of mice. However, CCNU increased also the specific-locus mutation frequency in spermatogonia in two out of three experiments. We conclude in analogy with criteria developed by IARC, that BCNU and CCNU are potential human mutagens.

Mutation spectra analysis suggests that N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea-induced lesions are subject to transcription-coupled repair in Escherichia coli

To determine the influence of some bacterial DNA repair pathways on the mutagenic and the lethal effects of N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU), pZ189 plasmids treated in vitro with 2 mM CCNU were transfected into Escherichia coli strains with different repair capacities (uvr+ada+ogt+, uvr-ada+ogt+, and uvr-ada-ogt-). Despite the differences in repair capacities, no statistically significant difference in survival and mutability was observed among the tested strains. One hundred and sixty-six CCNU-induced supF mutants were isolated and sequenced. All mutants were characterized by single base-pair substitutions, most of which (more than 96%) were GC-->AT transitions (the mutated G being almost exclusively preceded 5' by a purine). Mutation distribution was not random. Position 160 (5'-GGT-3', nontranscribed (NT) strand) was a uvr+ada+ogt(+)-specific hot-spot. Position 123 (5'-GGG-3', NT strand) was a common hot-spot but significantly more mutable in repair-proficient strains than in repair-deficient strains. Conversely, position 168 (5'-GGA-3', transcribed (T) strand) was significantly more mutable in repair-deficient strains than in repair-proficient strains. By applying a computer program for comparison of mutational spectra, we found that the uvr+ mutational spectrum was significantly different from those obtained in uvr- strains, whereas in the uvr- background, no difference was observed between mutation spectra in ada+ogt+ versus ada-ogt- strains. Our results are consistent with the hypothesis that O6-alkylguanine is responsible for most mutations observed in all strains. The results also indicate that excision repair modulates the distribution of GC-->AT transitions. The fact that mutations at G lesions on the T strand were significantly less frequent in uvr+ than in uvr- strains suggests that CCNU-induced premutational lesions are susceptible to strand-preferential repair in E. coli.

Mutational specificity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in Escherichia coli: comparison of in vivo with in vitro exposure of the supF gene

Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the supF gene of Escherichia coli were recovered from bacteria deficient in nucleotide excision repair and in DNA-alkyltransferase activity. Bacteria were exposed to 0.4 mM CCNU (in vivo supF mutagenesis), increasing the overall mutation frequency 15.7-fold above the spontaneous value. A total of 73 independent supF- mutants were sequenced. The resulting mutation spectrum was compared with those obtained in bacteria and mammalian cells following the classical shuttle-vector approach (in vitro supF mutagenesis). In vivo CCNU mutagenesis in E. coli yielded a large number of deletions (20/73), in agreement with mammalian data but distinct from in vitro bacterial spectra, which are almost exclusively composed of G:C-->A:T transitions. A substantial proportion (6/18) of CCNU-induced deletions (> 3 bp) involved repeated DNA sequences, suggesting a contribution of a slippage-misalignment process in the generation of this mutation class. Substitutions occurred primarily at G:C base pairs (44/53) and were predominantly G:C-->A:T transitions (39/53). This mutational change was attributed to the mispair potential of the O6-chloroethylguanine lesion with thymine. Most G:C-->A:T transitions (34/39) were located at three 5'-GG-3' hotspot sites (positions 123, 160, and 168). The distribution of hotspot sites for G:C-->A:T substitutions differed as a function of the in vivo or in vitro chemical modification of the supF-bearing plasmids and revealed significant differences in the DNA strand distribution of this mutational event. Our data suggest that the transcriptional status of the target gene has strong influence on the probability of O6-chloroethylguanine formation, reducing its incidence in the transcribed DNA strand.

Mutational fingerprint induced by the antineoplastic drug chloroethyl-cyclohexyl-nitrosourea in mammalian cells

Using the pZ189 shuttle vector approach, we determined two chloroethyl-cyclohexyl-nitrosourea (CCNU)-induced mutation spectra (3 and 6 mM) in African green monkey kidney cells (CV1). One hundred and twenty-one independent clones (101 CCNU induced, 45 at 3 mM and 56 at 6 mM; 20 spontaneous) showing functional inactivation of the supF gene were analyzed. One hundred and five plasmids (91 CCNU induced, 41 at 3 mM and 50 at 6 mM; 14 spontaneous), showing no large deletion/rearrangements, were sequenced. Ninety mutants (81 CCNU induced and 9 spontaneous) showed at least one mutation in the supF region. The analysis of the 122 CCNU-induced mutations (56 and 66 at 3 and 6 mM, respectively) revealed that: (a) the majority of the mutations were GC-targeted base pair substitutions; (b) AT-targeted mutations were significantly more frequent in the CCNU-induced (6 mM) than in the spontaneous mutational spectrum (P < 0.0006, Fisher's exact test); (c) mutational spectra obtained at 3 and 6 mM CCNU were significantly different (P < 0.008); (d) induced mutations were nonrandomly located in both spectra and generated either a common hot spot (position 123, 5'-GGG-3') or hot spots exclusive for each CCNU concentration (3 mM: position 159, 5'-AGG-3'; 6 mM: position 109, 5'-GGG-3'); (e) the occurrence of GC-->AT transitions was significantly different as a function of CCNU concentration (P < 0.02, Fisher's exact test), the mutated G being almost exclusively preceded by a purine (5'Pu G) at 6 mM and by either Pu or Py at 3 mM; and (f) by applying Calladine's rules, we found that sequences encompassing the three CCNU hot spots shared identical helix parameters for no more than 2 bp steps 5' (or 3 bp steps 3') to the mutated G. Our results are consistent with the hypothesis that O6-alkylguanine is responsible, either directly or indirectly, for the majority of GC-targeted mutations, while O4-alkylthymine and/or N3-alkyladenine are probably responsible for AT-targeted mutations. The results suggest also that, in CV1 cells, the efficiency of the repair mechanism(s) involved in the removal of O6-alkylguanine is influenced by the DNA sequence context. All of these factors determine the CCNU mutational fingerprint. CCNU has been implicated in the induction of therapy-related leukemias.(ABSTRACT TRUNCATED AT 400 WORDS)

Repair of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea-induced damage by mammalian cell extracts

The repair of damage induced by the alkylating antitumor drug 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) was investigated using an in vitro excision repair system. Hamster cell extracts prepared from the parental CHO-9 cell line and the ERCC1 mutant 43-3B were both proficient in the repair of CCNU-induced damage. The in vitro repair of CCNU damage was faster than the repair of UV damage and plasmid substrates were rapidly and efficiently incised after incubation with either CHO-9 or 43-3B extracts. 7-Methylguanine (7-meG) and 3-methyladenine (3-meA) glycosylases were active to a similar extent in the CHO-9 and 43-3B extracts. The data indicate that most damage induced by CCNU is repaired via the ERCC1-independent base excision repair pathway, initiating with removal of chloroethylated and hydroxyethylated bases by N-glycosylases. Yet, the sensitive phenotype of 43-3B cells suggests that the ERCC1 gene product is required for the removal of a small subset of CCNU-induced lesions that are important for drug cytotoxicity.

Chemosensitization of CCNU in KHT murine tumor cells in vivo and in vitro by the agent RB 6145 and its isomer PD 144872

The cytotoxicity and chemosensitizing potential of the nitrohetercyclic agent RB 6145 and its R enantiomer PD 144872 were determined in rodent tumor cells grown in tissue culture or as solid tumors. Using a clonogenic cell survival assay the degree of selective cytotoxicity of these bioreductive drugs was first determined in KHT/iv cells. Cells treated under hypoxic conditions were observed to be approximately 50-80-fold more susceptible to the action of RB 6145 or PD 144872 than were cells exposed under air. To assess the in vitro chemosensitizing potential of RB 6145 and PD 144872, doses of these agents which led to survival values between 0.5 and 1.0 under hypoxic conditions were administered, and were then combined concomitantly with variable doses of the nitrosourea CCNU. Exposure to the nitrosourea was for 1 h. The results showed that inclusion of either sensitizer enhanced the cell killing of the chemotherapeutic agent 2.4-2.6-fold. Subsequent experiments evaluated the therapeutic benefit of combining these bioreductive agents with CCNU in KHT sarcoma-bearing C3H/HeJ mice. When given at times ranging from 90 min before to 60 min after CCNU exposure, these bioreductive drugs increased the tumoricidal activity of the chemotherapeutic agent. Complete dose response curves combining RB 6145 and PD 144872 and a range of CCNU doses also were evaluated. The sensitizers (0.75 mmol/kg) were administered 30 min prior to the chemotherapeutic agent and survival of clonogenic tumor cells 22-24 h after treatment was used to assay tumor response.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of carbamoylated thiol conjugates as metabolites of the antineoplastic 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, in rats and humans

The metabolic fate of 1-(2-chloroethyl)-3-cyclohexyl)-nitrosourea (CCNU) in rats and humans was investigated with a view to characterizing the nature of the carbamoylating species released upon in vivo transformation of the drug. CCNU undergoes oxidation in vivo to afford 4-hydroxy and 3-hydroxy CCNU which, along with the parent drug, decomposes to the corresponding isocyanates. Although the highly reactive nature of the isocyanate species precludes their identification in vivo, their existence as electrophilic intermediates was detected in the likeness of trapped glutathione (GSH) and N-acetylcysteine (NAC) conjugates. Conjugated thiol metabolites were purified by HPLC from the bile and urine of CCNU-dosed rats, and the urine of a patient on CCNU therapy. The metabolites were identified by atmospheric pressure chemical ionization LC/MS and LC/MS/MS. In addition, LC/MS and LC/MS/MS spectra of synthesized authentic standards corroborated the identity of the metabolites. In rats, 4-hydroxycyclohexyl, 3-hydroxycyclohexyl, and cyclohexyl isocyanate were identified as their GSH conjugates in bile and NAC conjugates in urine. In the case of the patient, the NAC conjugates of 4-hydroxycyclohexyl and 3-hydroxycyclohexyl isocyanate were identified as urinary metabolites. The identification of GSH and NAC conjugates reported herein marks a significant advance in the assessment of the in vivo carbamoylating activity of CCNU and its phase I metabolites.

Depletion of O6-alkylguanine-DNA alkyltransferase correlates with potentiation of temozolomide and CCNU toxicity in human tumour cells

Temozolomide (8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4-(3H)-one) has shown promising activity in Phase I trials against some brain (glioma) and skin (melanoma, mycosis fungoides) cancers. Temozolomide and lomustine (CCNU) showed parallel toxicity in seven human tumour cell lines and this generally correlated (correlation coefficients 0.87 and 0.92 respectively) with the level of expression of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (ATase, EC 2.1.1.63). Pretreating cells with the ATase inhibitor, O6-benzylguanine (BG), potentiated cytotoxicity to a similar degree with both drugs, but did not sensitise a cell line (ZR-75-1) expressing very low levels of this protein. When BG pretreatment was combined with repeat doses of temozolomide a dramatic potentiation (300 fold) was seen in MAWI cells, which express high levels of ATase, but not in a cell line (U373) expressing lower levels of ATase. [14C]-labelled temozolomide uptake was similar in sensitive and resistant lines. Human ATase-cDNA transfected xeroderma pigmentosum (XP) fibroblasts were more resistant than XP control cells to temozolomide and the related chloroethylating agent mitozolomide and although BG completely suppressed ATase activity in these cells, resistance was still greater than in control cells.

Potentiation of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea's toxicity in vitro by two new bioreductive agents

Two new bioreductive compounds, 9-[3-(2-nitro-1-imidazolyl)propylamino]acridine hydrochloride (NLA-1) and 9-[2-(2-nitro-1-imidazolyl)ethylamino]acridine hydrochloride (NLA-2), which behave as hypoxic cytotoxins and radiosensitizers, have been investigated for potentiation of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea's (CCNU) cytotoxic activity in vitro using V-79 cells. The preincubation effect as well as conditions of coadministration of CCNU with each sensitizer have been examined. In this latter case, the median-effect analysis was applied to evaluate whether the phenomenon was additive or synergistic. A clonogenic assay was used to score survival. Both bioreductive compounds, even at very low concentrations, significantly enhance the cytotoxic activity of CCNU under conditions of hypoxic preincubation. The enhancement of CCNU cytotoxicity is dependent upon preincubation time and the concentrations of both CCNU and the specific bioreductive agent. Coincubation of cells under hypoxia with CCNU and each bioreductive agent led to some potentiation, but only at lower survival levels. No chemosensitization was observed under aerobic conditions with either sensitizer.

Synergistic effect of CCNU and bleomycin on human lymphocytes exposed at late G1 and G2 states of the cell cycle

The combined action of the antitumor antibiotic bleomycin and chloroethylnitrosourea (CCNU) was studied in human lymphocytes in vitro. All the experiments were carried out with 20 micrograms/ml bleomycin for a given treatment time. By adding 0.7 and 3.5 micrograms/ml CCNU at late G1-S phase we have demonstrated a considerable increase in both percent of aberrant cells and production of dicentrics and rings (5-fold, p less than 0.001). At late S-G2 the combined treatment led to a significant enhancement of breaks per cell (p less than 0.0001) and cells with more than 12 aberrations. A possible explanation could be the known repair-inhibitory potential of CCNU, but its pure clastogenic action still has to be considered. The results presented here point out the need for seeking chemotherapeutic regimens with reduced concentrations of the drugs in combination.

Nitrosoureas lomustine, carmustine and fotemustine induced hepatotoxic perturbations in rats: biochemical, morphological and flow cytometry studies

Chloroethylnitrosoureas are reactive compounds that are highly effective against malignant neoplasms in humans and animals. The most widely used nitrosoureas, lomustine and carmustine, are known to be hepatotoxic and to induce pericholangitis and intrahepatic cholestasis, which in the long term lead to cholangiolysis and biliary cirrhosis. However, the nitrosourea fotemustine has proved to be non-hepatotoxic at 20 mg/kg and 50 mg/kg. We have studied the effect of these three nitrosoureas on the cytotoxicity and cellular kinetics of rat liver cells. Lomustine and carmustine modify the proliferation index of liver cells in vivo: flow cytofluorometry showed that DNA cell distribution is quite similar for lomustine and carmustine, with subsequent accumulation of cells in G2 + M phase. 3 months later regressive morphological and cell cycle perturbations are noted for the lower dose of lomustine and carmustine. The most severe lesions are noted with lomustine (50 mg/kg). Fotemustine is not hepatotoxic and preferentially induces S phase perturbations. The more toxic nitrosoureas, lomustine and carmustine, induce comparable hepatocyte cell cycle alterations which differ from those induced by the less hepatotoxic nitrosourea fotemustine.

Radiotherapy alone versus combined chemotherapy and radiotherapy in nonresectable non-small-cell lung cancer: first analysis of a randomized trial in 353 patients

We report the results observed in a large, randomized study that compared the effects of radiotherapy alone (the standard therapy) with those of a combination of radiotherapy and chemotherapy in nonresectable squamous cell and large-cell lung carcinoma. The radiation dose was 65 Gy in each group, and chemotherapy included vindesine, cyclophosphamide, cisplatin, and lomustine. In this study, 177 patients received radiotherapy alone (group A), and 176 patients received the combined treatment (group B). The 2-year survival rate was 14% in group A and 21% in group B (P = .08). The distant metastasis rate was significantly lower in group B (P less than .001). Local control was poor in both groups (17% and 15%, respectively) and remained the major problem.

Salvage chemotherapy for non Hodgkin's lymphoma of unfavourable histology with a combination of CCNU and vinblastine

Twenty patients with relapsed or refractory, intermediate or high grade non Hodgkin's lymphoma were treated with a combination of CCNU and vinblastine. Complete responses occurred in four patients (20 per cent), partial responses in eight (40 per cent), for an overall response rate of 60 per cent. The regimen was more effective in patients with high grade lymphoma, absence of constitutional symptoms, better response to prior treatment. Duration of response was 4, 8, 16, 30 months for complete responders; 2, 2, 6, 6, 6, 8, 9, 14 months for partial responders. This combination regimen seems at least as effective as most of other regimens utilized in salvage treatment of non Hodgkin's lymphomas, with a very acceptable toxicity.

Vincristine infusion with CHOP-CCNU in diffuse large-cell lymphoma

Phase I and II trials of vincristine infusion have demonstrated the safety and efficacy of this approach in the treatment of patients with refractory non-Hodgkin's lymphoma. Subsequently, a trial was designed to evaluate this technique in untreated patients. Repeated 5-day infusions of vincristine 0.25 mg/m2 per day were incorporated into a CHOP-CCNU regimen and administered to 24 patients with advanced diffuse large-cell lymphoma. Objective responses occurred rapidly and were observed in 18 (75%) patients in whom 13 (54%) were complete. Toxicity was generally mild to moderate and neurotoxicity appeared to be no worse than typically observed with bolus vincristine. Complete responses have been durable in most patients and 10 (77%) of the complete responders have not relapsed. At this time, 9 (38%) of the total patients remain alive and without evidence of disease from 3.8 to 7.3 years from the start of treatment. One patient died of disseminated gastric cancer at 3.3 years from the start of therapy and there was no evidence of lymphoma at exploratory laparotomy. Infusion of vincristine may be safely incorporated into multiagent chemotherapy programs of the CHOP type for non-Hodgkin's lymphoma. Its potential for protracted nonmyelosuppressive cell kill would appear attractive in designing future trials for this disease.

Induction chemo-radiotherapy and maintenance alternating chemotherapy for small cell lung cancer

Seventy-four patients with small cell lung cancer (SCLC) entered a program consisting of induction with three courses of CAV (cyclophosphamide, doxorubicin and vincristine) in limited disease or two courses of CAV plus two courses of DDP-VP16 (cisplatin, etoposide) in extensive disease, followed by chest radiotherapy (45 Gy) and prophylactic brain irradiation (30 Gy) in responsive patients. Subsequently, patients with response or stable disease received maintenance therapy by alternating courses of CAV, DDP-VP16 and C'MP (CCNU, methotrexate, procarbazine) during 1 year or until relapse. Sixty-seven patients were evaluable. Among 24 patients with limited disease 7/23 (30%) showed complete response, 15/23 (65%) partial response and 1/23 (5%) stable disease. Among 50 patients with extensive disease 1/44 (2%) showed complete response, 21/44 (48%) partial response, 13/44 (30%) stable disease and 9/44 (20%) progressive disease. Actuarial median survival in all patients was 8 months, in responders 11 months, and in failures (stable plus progressive patients) 4 months. Median survival was 11 months in limited disease patients and 7 months in extensive disease patients. Six patients became long-term survivors (8%). Despite the maintenance therapy with three different alternating chemotherapy regimens, our results were not superior to those obtained by more conventional chemotherapy.

The hepatotoxicity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in rats. Ultrastructural evidence of a delayed microtubular toxicity

A few cases of liver involvement have been reported in patients receiving treatment with the antineoplastic nitrosourea CCNU. A single oral dose of 20 or 50 mg/kg CCNU in female Wistar rats induced an important increase in transaminases between day 2 and day 6, followed by a second, moderate increase between day 21 and day 28. Alkaline phosphatases and conjugated hyperbilirubinemia (threefold-increase) were noted for the two doses and were greater for the highest dose. Histological and ultrastructural studies disclosed hepatic lesions of two types: during the first phase of transaminase increase, inflammation of the portal tracts; during the second phase marked dilation of bile canaliculi and numerous filamentous bundles distributed at random throughout the liver cell cytoplasm like normal microtubules. Thus, CCNU induced pericholangitis and intrahepatic cholestasis with microtubular abnormalities. The long-term evolution of hepatic alterations revealed that in the 3rd month after a single oral dose of 20 mg/kg CCNU, lesions were persistent but stable; no reversibility was observed in the 3rd month after 50 mg/kg CCNU, and evolution towards cholangiolysis and biliary cirrhosis was noted. We suggest that CCNU causes a bimodal hepatotoxicity in rats: an early and prolonged ductal injury and a delayed anti-liver cell microtubule toxicity.

Effect of O6-methylguanine on DNA interstrand cross-link formation by chloroethylnitrosoureas and 2-chloroethyl(methylsulfonyl)methanesulfonate

Exposure of HT29 cells in culture to O6-methylguanine is known to result in a reduction in O6-alkylguanine-DNA alkyltransferase (AGT) activity and an enhancement of sensitivity to the cytotoxic effects of chloroethylating agents. Since cytotoxicity of these agents may be mediated by the formation of interstrand cross-links, alkaline elution analysis was performed on HT29 cells treated with 1-(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, and Clomesone [2-chloroethyl(methylsulfonyl)methanesulfonate] in the presence or absence of O6-methylguanine pretreatment to determine if the enhanced toxicity was due to an increase in the number of cross-links formed. Interstrand cross-linking by 1-(2-chloroethyl)-1-nitrosourea or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea was increased by pretreatment with 0.4 mM O6-methylguanine for 24 h. Cross-linking by Clomesone was observed only in cells exposed to 0.4 mM O6-methylguanine for 24 h prior to administration of the drug and for 12 h after administration, suggesting that the resynthesis of the AGT may prevent the cross-linking by Clomesone. Complete recovery of AGT activity after reduction to 20 to 30% of the basal level upon treatment with 0.4 mM O6-methylguanine required between 8 h and 15 h in both HT29 cells and in Raji cells which were also sensitized to 1-(2-chloro-ethyl)-3-cyclohexyl-1-nitrosourea by exposure to O6-methylguanine. These data suggest that the enhancement of chloroethylnitrosourea toxicity after treatment with O6-methylguanine may be related to an increase in the number of DNA cross-links and that the relatively rapid rate of AGT recovery plays a role in prevention of cross-links resulting from Clomesone.

CCNU-adriamycin association induces earlier and more severe nephropathy in rats

Adriamycin (ADR) has a broad spectrum of antitumoral activity but is ineffective against human brain tumors. However, such tumors can be sensitive to a combination of adriamycin and lipophilic antineoplastic agents such as the nitrosoureas. CCNU, a nitrosourea, induces cholestasis in the rat and ADR is predominantly excreted via the biliary route. We decided to investigate the effect of CCNU on the nephrotic syndrome induced by ADR. Female Wistar rats were injected with a single dose of 10 mg/kg ADR and 24 h later were force fed 20 mg/kg CCNU in a single dose. Animals were sacrificed 4, 8, 15, 21, 28 or 60 days after the injection of ADR. A high rate of fatality (60%) occurred after the 21st day of treatment. Biological changes (alkaline phosphatase, SGPT, bilirubin) and ultrastructural studies showed that CCNU and CCNU + ADR induced the same degree of cholestasis. With the administered dose, CCNU is not nephrotoxic, ADR induces a nephrotic syndrome and ADR + CCNU appeared more nephrotoxic. With ADR, visceral epithelial foot process fusion was seen on day 15 and tubulo-interstitial lesions and glomerulosclerosis on day 60. With ADR + CCNU fusion of the foot process was seen on day 4, glomerular vacuolation on day 8, tubulo-interstitial alterations on day 15 and glomerulosclerosis on day 60. For both ADR and ADR + CCNU wrinkling and thickening of the basement membrane of proximal tubular cells were seen on day 60. Lipid mesangial overload was seen with ADR and was more intense with ADR + CCNU on day 60. CCNU hepatoxicity modifies the excretion of ADR and the predominantly renal excretion of ADR seems to induce earlier renal alterations in ADR + CCNU-treated rats. This study supports the concept that lipid mesangial overload may play an important role in chronic progressive glomerulosclerosis and thus the ADR + CCNU combination appears to be an interesting model in which to study these relationships.

Sister chromatid exchange in human lymphocytes exposed to ascorbic acid and the cancer chemotherapeutic agent 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea

This study examines sister chromatid exchange (SCE) induction by ascorbate, a weak in vitro SCE inducer which acts through free radical intermediates, and low doses of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), a potent SCE inducer which acts primarily through DNA interstrand cross-links. A small dose-dependent increase in SCE was observed in human peripheral lymphocytes exposed to ascorbate in the 0.5-10 mM dose range for 59 hours, with significant slowing of cell cycle kinetics at concentrations at and above 5 mM. CCNU concentration was selected to approximate the maximal increase in SCE induced by ascorbate. SCE frequencies in cells exposed sequentially to both agents were not significantly different from expectations under an additivity-of-effect model based on SCE response to each agent individually. Despite clear differences in the types of lesions induced, ascorbate and CCNU appear to act independently to induce SCE in a manner consistent with, though not exclusive to, Painter's replicon cluster model.

Enhancement of toxicity from N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea in V79 spheroids by a nitrofuran

Hypoxic cell radiosensitizers enhance the cytotoxicity of several common chemotherapeutic agents in vitro and in vivo. Although this process has generally been called sensitization, few studies have documented true potentiation. We have used Chinese hamster V79 spheroids to study chemosensitization and fluorescence-activated cell sorting to specifically evaluate the roles of sensitizer binding and hypoxia in the effect. By using the median effect analysis to quantify the interactions of the agents, we conclude that marked potentiation can indeed be achieved. Somewhat greater potentiation was observed at increased depths within the spheroids, but the relative change was less than predicted on the basis of the decreasing oxygen tension. Further, increased toxicity did not necessarily lead to increased chemopotentiation, nor was potentiation directly related to the metabolism/binding of the nitrofuran. Thus, chemopotentiation is clearly a complicated process, highly dependent upon the sensitizer to antitumor drug ratio and the exposure conditions.

Studies on the mechanism of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)-induced hepatotoxicity. III. Ultrastructural characterization of bile duct injury

The antineoplastic nitrosourea CCNU is a known hepatotoxin which has been shown to cause hyperbilirubinemia and reduction in bile flow. We studied morphological alterations in the common bile duct and interlobular bile ducts at 6, 12, and 24 h in male rats given a single oral dose (50 mg/kg) of CCNU. The portal vein was perfused with 1.0% glutaraldehyde fixative. Portal areas and the common bile duct were selectively dissected and processed using standard methods for light and transmission electron microscopy. The epithelial cells of larger common bile duct and interlobular bile ducts showed increased rough endoplasmic reticulum, markedly increased free ribosomes, and mitochondrial degeneration at 6 and 12 h after CCNU. There was also bile imbibition and loss of microvilli, which increased in severity at 12 and 24 h. The interstitium showed infiltration by acute inflammatory cells and dilated capillaries at 6 h. By 24 h, degeneration of epithelial cells was extensive; cells became necrotic and sloughed into the duct lumen. The smaller bile ductules showed no significant degenerative changes; adjacent hepatocytes were unremarkable. Early CCNU injury appears localized in the large bile ducts and reflects inflammatory edema, bile stasis, and degeneration of epithelial cells. Our studies suggest that this ductal injury may reflect metabolism of CCNU to reactive species within the bile ducts.

Studies on the mechanism of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)-induced hepatotoxicity. II. Biochemical and morphological characterization of the injury and its prevention by phenobarbital

The present study characterizes the biochemical, morphological, and histological sites of CCNU-induced hepatotoxicity and investigates the effect of modifiers of drug metabolism on this toxicity. A single oral dose (100 mg/kg) of CCNU caused four- and ninefold increases in serum GOT and GPT respectively 48 h after administration in rats. A 25-fold rise in serum bilirubin, a total loss of bile flow, and a decrease in BSP clearance were also observed. Cytochrome P-450 content and EM-N-demethylase activity were significantly decreased to 88% and 66% of control values respectively. A histopathological time course study of CCNU-induced injury showed a progression of acute inflammation, edema, and fibrin deposition in portal areas over 24 h with necrosis and sloughing of bile duct epithelium at 24 and 36 h. Treatment of rats with PB (40 mg/kg/day for 4 days, i.p.) 24 h prior to CCNU administration protected against CCNU-induced hepatotoxicity. Thus, the levels of serum GOT, GPT, and bilirubin were only 2.5 and 4 times higher than in untreated or PB-treated controls. Histopathological examination also showed reduced severity of bile duct lesions in PB-pretreated animals. In rats receiving both PB and CCNU, bile flow was restored and BSP clearance was increased compared to the CCNU-treated rats. The mixed-function oxidase activity in PB + CCNU-treated rats was not significantly different from that in PB-treated controls. It is concluded that pretreatment of rats with PB can markedly suppress the hepatotoxic manifestations, including histopathological changes, the rise in serum bilirubin, and the cholestasis observed in CCNU-treated rats.

DNA adducts and DNA damage by antineoplastic and carcinogenic N-nitrosocompounds

Mechanisms of DNA adduct formation by antineoplastic 2-chloroethyl-N-nitrosoureas (CNUs) and of DNA damage induced by these compounds as well as by carcinogenic 2-hydroxyalkylnitrosamines are discussed. CNUs are monofunctional and bifunctional alkylating agents that form, in a quantitatively minor reaction, DNA-DNA crosslinks (XL). In vitro, by far the most abundant alkylation products of DNA are those resulting from 2-hydroxyethylation. The reaction sequence responsible for 2-hydroxyethylation comprises intermediate oxazolidine ring closure followed by generation of 2-hydroxyethylnitrosourea and ethylene oxide. Oxadiazolium intermediates have not been found to play a role. In contrast to the in vitro experiments, in vivo 2-hydroxyethyl adducts are formed to a much lesser extent und 2-chloroethyl adducts are predominant in rat kidney DNA. 2-Hydroxyethylation of phosphate groups introduces extreme instability into the sugar-phosphate backbone since the resulting phosphotriester rapidly breaks down through a dioxaphospholane ring intermediate. Measurements of DNA XL in target tumor tissue and in bone marrow provides a sensitive tool for evaluation in bone marrow provides a sensitive tool for evaluation of hormone-linked cytotoxic agents. The potent environmental carcinogen N-nitrosodiethanolamine (NDELA) has been found to be activated in the rat liver by a two-step metabolic transformation sequence involving alcohol dehydrogenase and, subsequently, sulfotransferase. Evidence for this mechanism is provided by measuring DNA single strand breaks in rat liver DNA and by studying the effect of various enzyme inhibitors on the extent of DNA damage induced in vivo by NDELA and its metabolites.

Sensitivity to DNA-damaging agents and mutation induction by UV light in UV-sensitive CHO cells

Three UV-sensitive (UVs) mutants isolated from a CHO cell line were analyzed for survival after exposure to H2O2, EMS, MMC, CCNU, X-rays and for mutation induction after UV-irradiation. The UVs mutants showed normal sensitivities to EMS and H2O2, whereas they were hypersensitive to the bifunctional alkylating agents MMC and CCNU and to hypoxic X-irradiation. Compared to parental cells, one of the UV-sensitive clones showed approximately 3- and 7-fold enhancement in the mutagenic response per unit UV dose for 6-thioguanine and ouabain resistance, respectively.

Effect of cell cycle position on the survival of 9L cells treated with nitrosoureas that alkylate, cross-link, and carbamoylate

The relationship between cell cycle position and cytotoxicity was studied in 9L rat brain tumor cells treated with nitrosoureas that, depending on their structures, can alkylate or alkylate and cross-link DNA and/or carbamoylate biomolecules. Because pure populations of G1-, S-, and G2-M-phase cells could not be obtained with the centrifugal elutriation methods used, drug sensitivity of cells in each phase of the cell cycle was estimated using a mathematical model that accounts for variation in enrichment of elutriated fractions. 1,3-Bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea, 1-(2-chloroethyl)-3-(2,6-dioxo-3-piperidyl)-1-nitrosourea, which alkylate and cross-link DNA and carbamoylate biomolecules, and 2-[3-(2-chloroethyl)-3-nitrosoureido]-D-glucopyranose (chlorozotocin), which alkylates and cross-links DNA but cannot carbamoylate biomolecules, killed more cells in G1 and G2-M phases than in S phase. N-Ethylnitrosourea, which alkylates and carbamoylates but does not form DNA interstrand cross-links, was more toxic to cells in S phase than in other phases. Cell kill caused by N,N'-bis(trans-4-hydroxycyclohexyl)-N-nitrosourea, a compound that carbamoylates only, increased progressively through the cell cycle from G1 to M. Nitrosoureas that cross-link DNA were more cytotoxic than nitrosoureas that do not cross-link DNA, although the latter had phase specificity. The results suggest that the increased sensitivity of G1- and G2-M-phase cells to chloroethylnitrosoureas is related to the formation of DNA interstrand cross-links.

Antineoplastic activity and toxicity of some alkylating cytostatics (cyclophosphamide, CCNU, cytostasan) encapsulated in liposomes in different murine tumour models

The encapsulation of Cyclophosphamide in MLV (PC:CH 1:1) revealed a total loss of antineoplastic activity in the P 388 tumour model compared to an equal dose of the free drug, though a moderate toxicity, registered as decrease of leukocyte and platelet counts, was still present. CCNU in liposomes of different size and composition showed in lower doses a diminished therapeutic effectiveness in the P388 or L 1210 leukaemia and the B 16 melanoma, while in higher doses toxic deaths occurring with the free drug could be prevented totally by using liposomes. Liposomal encapsulation also influenced body weight change and leukocyte counts, causing them to be less drastically reduced than with use of the free drug. The entrapment of Cytostasan, an N-lost derivative, had the same effect on the increase of lifespan of tumour-bearing animals (mammary carcinoma 1142 A) as equal doses of the free drug and caused only a slight improvement of toxicity. In general, liposomal encapsulation of alkylating cytostatics seems advantageous only for certain lipophilic drugs.

Karyometric, cytophotometric and histoenzymatic studies on neuroglia of rats treated with 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU/lomoustine)

CCNU is a cytostatic drug, a nitrosourea derivative, used--among others--in therapy of tumors of the central nervous system. Even if the drug is regarded safe for central and peripheral nervous systems, a possibility of harmful effects of CCNU on the central nervous system should be examined caused by the affinity of all nitrosourea derivatives to lipids. This has prompted us to study the drug effect on neuroglia cells in corpus callosum and gyrus cinguli. The drug was administered to rats by the intragastric route in four doses--one dose a week. Three doses of 2.5 mg each were followed by one dose of 5 mg. Some brains were isolated for the studies, and paraffin sections were prepared for karyometric as well as cytophotometric studies and for section staining according to Nissl and Klüver-Barrer techniques 8 days after the last dosage. Brains of other experimental rats served for preparing cryostat sections for demonstration of phosphatase and esterase activities. The studies, conducted after CCNU administration, documented a significant decrease in size of oligodendroglia nuclei and an increase in size of astroglia nuclei. DNA content of neuroglia nuclei was markedly decreased. Histoenzymatic changes in experimental animals were not very pronounced and included a slight increase in TPPase and nonspecific esterase activities as well as a decrease in ATPase activity. Despite the changes in neuroglia cells no damage to corpus callosum myelin sheaths was observed.

[Hepatotoxicity of (chloro-2-ethyl)-1-cyclohexyl-3-nitroso-1-urea (CCNU) in the rat]

Few cases of liver involvement have been reported in patients receiving treatment with CCNU. CCNU is an anti-tumoral agent used in the treatment of leukemia, Hodgkin's disease and bronchial or cerebral tumors. A single daily dose of 20 or 50 mg/kg CCNU in female Wistar rats induces an important increase of transaminases, reaching 10 times initial level between day 2 and day 6, followed by a second and moderate increase between day 21 and day 28. Three-fold increased alkaline phosphatases and conjugated hyperbilirubinemia were noted for the two doses, and was greater for the higher dose. Histological and ultrastructural studies showed two types of lesions: during the first phase of transaminase elevation, edema and inflammatory infiltration of the portal spaces; during the second phase of transaminases elevation, numerous bundles of pericanalicular microfilaments and severe dilation of the biliary tract. Hepatic cells had few alterations although some necrotic foci were observed, particularly at the higher dose. So CCNU induced an intrahepatic cholestasis with pericholangitis in the rat.