Dietary induction of NQO1 increases the antitumour activity of mitomycin C in human colon tumours in vivo

The bioreductive antitumour agent, mitomycin C (MMC), requires activation by reductive enzymes like NAD(P)H:quinone oxidoreductase 1 (NQO1). We used a novel approach to increase MMC efficacy by selectively inducing NQO1 in tumour cells in vivo. CD-1 nude mice were implanted with HCT116 cells, and fed control diet or diet containing 0.3% of the NQO1 inducer, dimethyl fumarate (DMF). The mice were then treated with saline, 2.0, 3.5 or 2.0 mg kg⁻¹ MMC and dicoumarol, an NQO1 inhibitor. The DMF diet increased NQO1 activity by 2.5-fold in the tumours, but had no effect in marrow cells. Mice given control diet/2.0 mg kg⁻¹ MMC had tumours with the same volume as control mice; however, mice given DMF diet/2.0 mg kg⁻¹ MMC had significantly smaller tumours. Tumour volumes in mice given DMF/2.0 mg kg⁻¹ MMC were similar to those in mice given control diet/3.5 mg kg⁻¹ MMC. Tumour inhibition was partially reversed in mice given DMF/2.0 mg kg⁻¹ MMC and dicoumarol. DMF diet/2.0 mg kg⁻¹ MMC treatment did not increase myelosuppression and did not produce any organ toxicity. These results provide strong evidence that dietary inducers of NQO1 can increase the antitumour activity of bioreductive agents like MMC without increasing toxicity.

Clinical applications of quinone-containing alkylating agents

Quinone-containing alkylating agents are a class of chemical agents that have received considerable interest as anticancer drugs. These agents contain a quinone moiety that can be reduced and an alkylating group that can form covalent bonds with a variety of cellular components. The oxidation state of the quinone element can modulate the activity of the alkylating element, and reduction of the quinone is required for activation of the alkylating activity of many of these agents. The quinone element may also contribute to the cytotoxic activity of quinone-containing alkylating agents through the formation of reactive oxygen species during redox cycling. The natural product, mitomycin C, has been the most widely used quinone-containing alkylating agent in the clinic, but other quinone-containing alkylating agents like porfiromycin, diaziquone, carbazilquinone, triaziquone and EO9 have also been used in the clinic for the treatment of cancer. In addition, many other quinone-containing alkylating agents have been tested in preclinical studies and the development of new agents is being actively pursued. This chapter describes the current and past clinical uses of these agents in the treatment of cancer and discusses new agents that are currently in clinical trials.

A CD36 synthetic peptide inhibits bleomycin-induced pulmonary inflammation and connective tissue synthesis in the rat

Transforming growth factor (TGF)-beta1 is an important regulator of inflammation and fibrosis. TGF-beta1 is usually secreted as a biologically latent protein called latent TGF-beta1 (L-TGF-beta1). L-TGF-beta1 has no biologic effect unless L-TGF-beta1 is converted to its active form. Using a well-recognized model of lung injury induced by the antineoplastic antibiotic bleomycin (Blm), we demonstrated that 7 d after intratracheal Blm administration, total lung TGF-beta was maximally increased. This induction was due to TGF-beta1 production by alveolar macrophages that, when explanted, generated increased quantities of L-TGF-beta1 complexed with the glycoprotein thrombospondin (TSP)-1. The TSP-1/L-TGF-beta1 complex was associated with CD36, a receptor for TSP-1. The association of TSP-1/L-TGF-beta1 to CD36 was critical for plasmin-mediated release of mature TGF-beta1. In this paper we show that, compared with administration of Blm by itself, when a synthetic peptide of CD36 between amino acids 93 and 110 is given concomitantly with Blm to rats, alveolar macrophages generate markedly less active TGF-beta1, the rats gain weight more rapidly, and there is less inflammation, collagen I and III, and fibronectin synthesis. These findings demonstrate a novel in vivo mechanism of activation of L-TGF-beta1 in lung injury and the importance of alveolar macrophage- derived active TGF-beta1 in the pathogenesis of pulmonary inflammation and fibrosis.

Functional status of the immune system after chronic administration of 2'-deoxycoformycin in the BB rat

Insulin-dependent diabetes mellitus (IDDM) is caused by autoimmune destruction of pancreatic beta cells with the primary mechanism being cell mediated. The BB rat develops insulitis and IDDM with many features analogous to the disease in man. In previous studies we reported that weekly administration of 2'-deoxycoformycin (dCF) for four months reduces significantly the incidence of IDDM in the BB rat by 70%, and that the animals remain free of diabetes for a minimum of two months after drug withdrawal. Since the diabetes-prone BB rat is lymphopenic, with a reduction of both CD4 and CD8 cells, the continuous failure of dCF treated animals to develop diabetes may have been due to generalized immunosuppression. To test this possibility, the ability of dCF treated diabetes-free BB rats to mount an immune response after challenge with Ovalbumin was examined five months after drug withdrawal. The results showed that the post-immunization levels of total IgG and specific IgG in these animals did not differ from those observed in non-dCF treated controls nor those of control diabetes-resistant non-lymphopenic BB rats. Moreover, FACS analysis indicated no change in the percentages of total numbers of CD4+ or CD8+ cells between the two groups of animals. Histological assessment of the pancreata of the post-dCF treated animals showed varying degrees of mononuclear cell infiltrates in the islets. These data demonstrate that treatment by dCF is not permanent, and may require intermittent or continuous administration to prevent development of diabetes. Further studies are needed to determine the mechanism of action of dCF in this model of IDDM.

Enhanced cytotoxicity of mitomycin C in human tumour cells with inducers of DT-diaphorase

DT-diaphorase is a two-electron reducing enzyme that activates the bioreductive anti-tumour agent, mitomycin C (MMC). Cell lines having elevated levels of DT-diaphorase are generally more sensitive to MMC. We have shown that DT-diaphorase can be induced in human tumour cells by a number of compounds, including 1,2-dithiole-3-thione. In this study, we investigated whether induction of DT-diaphorase could enhance the cytotoxic activity of MMC in six human tumour cell lines representing four tumour types. DT-diaphorase was induced by many dietary inducers, including propyl gallate, dimethyl maleate, dimethyl fumarate and sulforaphane. The cytotoxicity of MMC was significantly increased in four tumour lines with the increase ranging from 1.4- to threefold. In contrast, MMC activity was not increased in SK-MEL-28 human melanoma cells and AGS human gastric cancer cells, cell lines that have high base levels of DT-diaphorase activity. Toxicity to normal human marrow cells was increased by 50% when MMC was combined with 1,2-dithiole-3-thione, but this increase was small in comparison with the threefold increase in cytotoxicity to tumour cells. This study demonstrates that induction of DT-diaphorase can increase the cytotoxic activity of MMC in human tumour cell lines, and suggests that it may be possible to use non-toxic inducers of DT-diaphorase to enhance the efficacy of bioreductive anti-tumour agents.

A three-year programme in oral diagnosis and treatment planning. A model using an interdisciplinary teaching team

Diagnosis and treatment planning are considered to be the basis for successful clinical dentistry, however, these skills are difficult to teach and evaluate. At the Department of Diagnosis and Treatment Planning, Tel Aviv University Dental School, a 3-year teaching programme has been developed. The goals of the programme are to teach a systematic pattern of data collection from history, clinical examination, imaging modalities and models, and to use this data to identify the patient's problems and to arrive at a final diagnosis, to develop a treatment plan, taking into account all relevant information, and to consult experts when needed, to train in case presentation, and to deal with peer response. The program includes 20 h of lectures and 30 h of exercises in the 4th year, developing at least 8 full treatment plans per student in the fifth year, a 1 30-min weekly panel seminar during the final year, and a final integrative examination at the end of the 6th year.

Induction of DT-diaphorase by 1,2-dithiole-3-thiones in human tumour and normal cells and effect on anti-tumour activity of bioreductive agents

DT-diaphorase is a two-electron-reducing enzyme that is an important activator of bioreductive anti-tumour agents, such as mitomycin C (MMC) and EO9, and is inducible by many compounds, including 1,2-dithiole-3-thiones (D3Ts). We showed previously that D3T selectively increased DT-diaphorase activity in mouse lymphoma cells compared with normal mouse marrow cells, and also increased MMC or EO9 cytotoxic activity in the lymphoma cells with only minor effects in the marrow cells. In this study, we found that D3T significantly increased DT-diaphorase activity in 28 of 38 human tumour cell lines representing ten tissue types with no obvious relationships between the tumour type, or the base level of DT-diaphorase activity, and the ability of D3T to increase the enzyme activity. Induction of DT-diaphorase activity in human tumour cell lines by 12 D3T analogues varied markedly with the D3T structure. D3T also increased DT-diaphorase activity in normal human bone marrow and kidney cells but the increases were small in these cells. In addition, D3T increased the level of enzyme activity in normal human lung cells. Pretreatment of human tumour cells with D3T analogues significantly increased the cytotoxic activity of MMC or EO9 in these cells, and the level of enhancement of anti-tumour activity paralleled the level of DT-diaphorase induction. In contrast, D3T did not effect the toxicity of EO9 in normal kidney cells. These results demonstrate that D3T analogues can increase DT-diaphorase activity in a wide variety of human tumour cells and that this effect can enhance the anti-tumour activity of the bioreductive agents MMC and EO9.

Expression of p53 predicts treatment failure in aggressive non-Hodgkin's lymphomas

Approximately 50% of patients with aggressive non-Hodgkin's lymphomas (NHL) achieve a complete remission (CR) and cure with combination chemotherapy. The International Index is a useful clinical measure that predicts the patients' tolerance of therapy and likelihood of achieving CR, but it is not a direct measure of chemosensitivity. In this study we have investigated the predictive value of the tumor suppressor gene, p53, as a biological marker for response to treatment in the aggressive NHL. A retrospective study was carried out on 50 patients with aggressive NHL who were treated with CHOP chemotherapy. Treatment outcome was correlated with the expression of p53 in the lymphoma, as measured by routine immunohistochemistry using the monoclonal antibody Do-7. Forty percent of the lymphomas had >5% of the cells staining positively for p53 and this finding correlated significantly with response to treatment. Fifty percent of patients with p53 positive tumors achieved a CR versus 77% of patients with p53 negative tumors. In addition, the relapse rate and time to relapse were significantly different in the two groups. In the p53 positive group, 60% of patients relapsed in a median time of 6 months, whereas 26% of the p53 negative group relapsed with the time to relapse being >22 months. The overall survival of the p53 positive group (17 months) was significantly shorter than that of p53 negative group (>24 months). These results suggest that the immunohistochemical assessment of p53 is a simple and important prognostic measure for patients with aggressive NHL who are treated with CHOP chemotherapy.

Induction of DT-diaphorase in cancer chemoprevention and chemotherapy

DT-diaphorase (EC 1.6.99.2) is a flavoprotein that catalyses two-electron reduction of quinones, quinone imines, and nitrogen oxides. It is a Phase II detoxifying enzyme that can detoxify chemically reactive metabolites, and may be important in an early cellular defense against tumorigenesis. DT-diaphorase is also an activating enzyme for bioreductive antitumor agents like mitomycin C (MMC) and EO9. DT-diaphorase is induced in many tissues by a wide variety of compounds including dithiolethiones and isothiocyanates. Dithiolethiones are chemoprotective agents against a variety of chemical carcinogens in animal models, and the dithiolethione analogue, oltipraz, is currently in Phase I and Phase II clinical chemoprevention trials. Similarly, the isothiocyanate derivative, sulforaphane, blocks the formation of carcinogen-induced mammary tumors in rats. The low toxicity of these inducers of DT-diaphorase makes them suitable for use as chemopreventive agents in high-risk individuals. Cells with elevated DT-diaphorase levels are generally more sensitive to bioreductive antitumor agents. Thus, we suggested that the antitumor efficacy of bioreductive agents can be enhanced by selective induction of DT-diaphorase in tumor cells compared with normal cells. We showed that 1,2-dithiole-3-thione (D3T) can increase the level of DT-diaphorase activity and the cytotoxic activity of bioreductive agents in mouse lymphoma cells without increasing these activities in normal mouse marrow cells. D3T also increased DT-diaphorase activity in 24 of 33 human tumor cell lines representing nine tissue types with no obvious relationships between the tumor type, or the base level of DT-diaphorase activity, and the ability to increase enzyme activity. A series of dithiolethione analogues and dietary components were also shown to be good inducers of DT-diaphorase in human tumor cells. D3T increased DT-diaphorase activity in normal human bone marrow and kidney cells but the increases were small in these cells. Combination treatment with D3T and EO9 increased cell kill in HL-60 human leukemia cells compared with EO9 alone, but had no effect on EO9 toxicity in normal human kidney cells. Similarly, D3T increased tumor cell kill by EO9 in H661 human lung cancer cells and by MMC in T47D human breast cancer cells. Thus, inducers of DT-diaphorase may play an important role in cancer chemoprevention programs and may also be useful in enhancing the antitumor efficacy of bioreductive agents.

A novel system of human submandibular/sublingual saliva collection

The assessment of submandibular/sublingual (sm/sl) saliva is a procedure of increasing significance. However, the collection of these fluids by traditional techniques is difficult and therefore often neglected. To collect sm/sl saliva, we have assembled a novel, universal system consisting of four parts-collecting tubing, a buffering chamber, a storing tube, and a suction device. Submandibular/sublingual saliva samples were collected from ten healthy and ten xerostomic individuals. The system showed intra-examiner reproducibility of 0.92 for healthy and 0.89 for xerostomic subjects, and inter-examiner reproducibility of 0.93 for normal subjects and 0.80 for xerostomic individuals. The flow rates obtained by the present collecting set-up were similar to those measured by all known previous methods that were published during the last 40 years. The system was also efficient, in that more than 90% of the fluid that entered the system was eventually collected in the storing tube for analysis. The system appears to collect relatively pure sm/sl fluids, since contamination of the collected sample by a stimulant solution swabbed repeatedly over the tongue during saliva collection was minimal. The system is reliable, safe, practical, and comfortable for the patient.

P53, MDM-2, BAX and BCL-2 and drug resistance in chronic lymphocytic leukemia

Most antitumor agents exert their cytotoxic effect through the induction of apoptosis, and this process may be mediated through an elevation in p53 protein, with a subsequent increase in bax and decrease in bcl-2. p53 also increases mdm-2 expression and mdm-2 may then bind and inactivate p53. Cells from 31 patients with chronic lymphocytic leukemia (CLL) were treated in vitro with 2-chlorodeoxyadenosine (CdA), arabinosyl-2-fluoroadenine (F-ara-A), or chlorambucil (CLB) and drug sensitivity measured using the MTT assay. The protein levels of bax and bcl-2 were measured in CLL cells from 25 patients, and were found to be higher in leukemic cells than in normal B cells. The bcl-2 levels varied three-fold, the bax levels fifteen-fold, and the bax:bcl-2 ratios ranged from 0.44 to 2.91. The expression of mdm-2 mRNA was measured in CLL cells from 28 patients and was found to vary twenty-fold. However, no correlation was observed between drug sensitivity to CdA, F-ara-A, or CLB and the cellular levels of mdm-2 mRNA, or the protein levels of bax or bcl-2, or the bax:bcl-2 ratio. Treatment of CLL cells having wild type p53 with CdA, F-ara-A or CLB produced an increase in p53 protein and mdm-2 mRNA. This was not observed in cells having a p53 mutation, and these cells were highly resistant to both CLB and the nucleoside analogs. In contrast to the nucleoside analogs and CLB, dexamethasone and vincristine had no effect on mdm-2 mRNA levels. Treatment of CLL cells containing a wild type p53 gene with CdA, F-ara-A, or CLB, did not produce any consistent changes in bax or bcl-2. Thus, CdA, F-ara-A and CLB appear to act in CLL cells through a p53-dependent pathway, whereas this does not occur with dexamethasone or vincristine. The cellular levels of mdm-2, bcl-2, bax or the bax:bcl-2 ratios are not predictive indicators of clinical sensitivity in CLL, but an increase in mdm-2 levels after drug treatment is indicative of p53 function in these cells.

Immunotherapy for insulin-dependent diabetes mellitus in the "BB" rat

We have previously reported that weekly administration of the adenosine deaminase inhibitor, 2'-deoxycoformycin (dCF), reduces the incidence of insulin-dependent diabetes mellitus (IDDM) in the BB Wistar rat, and this effect is likely due to immunosuppression by dCF. In the present study, we examined the effect of altering the dose and scheduling of dCF on prevention of IDDM in the BB rat. When rats were treated from day 25 of age with 2.5, 4, or 10 mg of dCF/kg/week, the percentage of diabetes-free animals at 120 days of age was 40, 60, and 80% respectively, compared with 10% for control animals, demonstrating increased protection against IDDM with increased dCF dose. Histological assessment of the pancreata from animals that became diabetic revealed a marked mononuclear infiltrate and a loss of positive staining for beta cell granules. In contrast, pancreata from animals that remained diabetes-free appeared normal. Protection against IDDM by dCF was time dependent and only occurred if treatments were initiated by day 30 of age. In addition, the protective effect persisted after drug withdrawal. Further studies are required to determine the optimum duration of therapy with dCF to prevent IDDM and to examine the immunological mechanism responsible for this effect.

In vitro cytotoxicity of 2-chlorodeoxyadenosine and chlorambucil in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is most commonly treated with the alkylating agent chlorambucil (CLB), although the nucleoside analogs, fludarabine (Flu) and 2-chlorodeoxyadenosine (CdA), are also effective in this disease. In this study, we investigated the in vitro cytotoxicity of CdA and CLB in CLL cells from 12 patients in vitro. Treatment with CLB for 6 h, followed by CdA for 18 h, resulted in 2.3- to 7.5-fold synergistic cytotoxicity in leukemic cells from 10 patients and an additive effect in cells from two patients. In general, synergy was greatest in patients who were sensitive to CLB or CdA, and could be enhanced by increasing the concentrations of CLB or CdA. Synergy was only observed if the cells were treated with CLB prior to CdA. Synergy could not be explained by an increase in the incorporation of CdA into DNA, or by the inhibition of repair of CLB-induced DNA crosslinks by CdA. In contrast to CLL cells, treatment of human marrow in vitro with CLB and CdA resulted in a low level of synergy for CFU-GM cells, and additive cell kill in erythroid progenitors. Thus, treatment with CdA and CLB can produce selective synergistic cell kill in CLL cells, and combination therapy may improve the therapeutic index of these agents in chemosensitive patients.

Chlorambucil in chronic lymphocytic leukemia: mechanism of action

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries but the clinical presentation and rate of disease progression are highly variable. When treatment is required the most commonly used therapy is the nitrogen mustard alkylating agent, chlorambucil (CLB), with or without prednisone. Although CLB has been used in the treatment of CLL for forty years the exact mechanism of action of this agent in CLL is still unclear. Studies in proliferating model tumor systems have demonstrated that CLB can bind to a variety of cellular structures such as membranes, RNA, proteins and DNA; however, DNA crosslinking appears to be most important for antitumor activity in these systems. In addition, a number of different mechanisms can contribute to CLB resistance in these tumor models including increased drug metabolism, DNA repair and CLB detoxification resulting from elevated levels of glutathione (GSH) and glutathione S-transferase (GST) activity. However, unlike tumor models in vitro, CLL cells are generally not proliferating and studies in CLL cells have raised questions about the hypothesis that DNA crosslinking is the major mechanism of antitumor action for CLB in this disease. CLB induces apoptosis in CLL cells and this appears to correlate with the clinical effects of this agent. Thus, alkylation of cellular targets other than DNA, which can also induce apoptosis, may contribute to the activity of CLB. Alterations in genes such as p53, mdm-2, bcl-2 and bax which control entry into apoptosis may cause drug resistance. Loss of wild-type p53 by mutation or deletion occurs in 10 to 15% of CLL patients and appears to correlate strongly with poor clinical response to CLB. The induction of apoptosis by CLB is paralleled by an increase in P53 and Mdm-2 but this increase in not observed in patients with p53 mutations indicating that with high drug concentrations CLB can produce cell death through P53 independent pathways. The level of Mdm-2 mRNA in the CLL cells is not a useful predictor of drug sensitivity. In addition, although Bax and Bcl-2 are important regulators of apoptosis and the levels of these proteins are elevated in CLL cells compared with normal B cells, the levels of Bax and Bcl-2, or the Bax:Bcl-2 ratio, are not important determinants of drug sensitivity in this leukemia. Finally, whereas CLB and nucleoside analogs may produce cell death in CLL by a P53 dependent pathway other agents, such as dexamethasone or vincristine, may act through P53-independent pathways.

Induction of DT-diaphorase by 1,2-dithiole-3-thione and increase of antitumour activity of bioreductive agents

Bioreductive antitumour agents are an important new class of anticancer drugs that require activation by reduction. The two-electron reducing enzyme, DT-diaphorase, has been shown to be an important activating enzyme for the bioreductive agents, mitomycin C (MMC) and EO9. Incubation of L5178Y murine lymphoma cells in vitro with 1,2-dithiole-3-thione (D3T) increased the level of DT-diaphorase activity in these cells 22-fold. In contrast, D3T had no effect on the DT-diaphorase level in normal mouse bone marrow cells. Combination therapy with D3T and MMC or EO9, produced a 2- or 7-fold enhancement, respectively, of the cytotoxic activity of these antitumour agents in L5178Y cells. By comparison, D3T did not enhance the activity of MMC in marrow cells and produced only a small increase in EO9 cytotoxicity in these cells. The DT-diaphorase inhibitor, dicoumarol, inhibited the effect of D3T on the antitumour activity of the bioreductive agents, supporting the proposal that the enhanced anticancer activity was due to the elevated enzyme level. These findings suggest that D3T, or other inducers of DT-diaphorase, could be used to enhance the antitumour efficacy of bioreductive antitumour agents.

Comparison of antitumor activities of 2-chlorodeoxyadenosine and 9-beta-arabinosyl-2-fluoroadenine in chronic lymphocytic leukemia and marrow cells in vitro

The in vitro antitumor activities of the nucleoside analogs, 2-chlorodeoxyadenosine (CdA) and 9-beta-arabinosyl-2-fluoroadenine monophosphate (Flu), and the alkylating agent, chlorambucil (CLB), were compared in leukemic cells from 28 patients with chronic lymphocytic leukemia (CLL). On a molar basis, the median sensitivities of the cells to these agents were CLB > CdA > Flu. CLL cells from 90% of the patients had similar relative orders of sensitivities to CdA and Flu, while cells from 10% of the patients showed differential sensitivities to these agents. There was no relationship between the sensitivities of the cells to the nucleoside analogs and sensitivity to CLB. CdA and CLB produced similar toxicities to human marrow progenitor cells in vitro, while Flu was less toxic to these cells. An 18 h exposure to CdA produced significantly greater cell kill of both CLL and marrow progenitor cells than an equivalent 2 h treatment; however, the difference in cytotoxicity was greater for the tumor cells resulting in a higher therapeutic index with the 18 h treatment. The intracellular accumulation of drug varied 5-fold for CdA, with the major metabolite being CdAMP, and 15-fold for Flu, with the major metabolite being F-ara-ATP. However, the accumulation of CdA, Flu or their metabolites did not predict for drug sensitivity. These studies suggest that CdA and Flu cross-resistance cannot be assumed in all CLL patients. The therapeutic effectiveness of CdA may be enhanced by use of a prolonged, low-dose drug regimen.

Induction of DT-diaphorase by doxorubicin and combination therapy with mitomycin C in vitro

Mitomycin C (MMC) is a bioreductive antitumor agent that is activated by NADPH:cytochrome P450 reductase (EC 1.6.2.4) and NAD(P)H:(quinone acceptor) oxidoreductase (EC 1.6.99.2) (DT-diaphorase). DT-diaphorase is a two-electron reducing enzyme that is induced by a variety of chemicals, including quinones. Doxorubicin (DOX) is an anthraquinone antitumor agent that has been used clinically with MMC for combination chemotherapy in breast cancer. In this study, we investigated whether DOX could selectively induce DT-diaphorase in tumor cells and whether combining this agent with MMC in an appropriate schedule could produce synergistic antitumor activity. Treatment of EMT6 murine mammary tumor cells with DOX resulted in a 40% increase in DT-diaphorase activity in these cells, but had no effect on this enzyme in murine bone marrow cells. Combination therapy with DOX and MMC produced a 1.4-fold level of synergistic cell kill in the tumor cells, but a similar level of synergy was also observed in normal bone marrow cells. Thus, DOX can selectively induce elevated levels of DT-diaphorase in tumor cells; however, the synergy observed by combining this agent with MMC appears to be unrelated to the induction of DT-diaphorase.

Deposition of transforming growth factor-beta in the marrow in myelofibrosis, and the intracellular localization and secretion of TGF-beta by leukemic cells

The marrows of 10 patients with hematologic malignancies were examined by immunohistochemistry using anti TGF-beta antibody, CC(1-30), which detects secreted TGF-beta, and compared with four normal marrows. TGF-beta was not demonstrated in marrows with a normal level of reticulin fibrosis; however, TGF-beta was observed within collagen in marrows having collagen fibrosis or increased reticulin fibrosis. The extent of TGF-beta deposition paralleled the severity of fibrosis (P < .0001), and occurred even with normal or reduced numbers of megakaryocytes. Using another TGF-beta antibody, LC(1-30), which detects intracellular TGF-beta, TGF-beta was detected by immunofluorescence in discrete sites in the cytoplasm of immature and mature myeloid and large granular lymphocytic leukemia cells. These sites colocalized with areas detected by an anti-granule antibody (D545) suggesting that TGF-beta was stored in granules. However, neither the TGF-beta mRNA content nor the degree of TGF-beta secretion by these leukemic cells correlated with the extent of TGF-beta deposition in the marrow. Thus, TGF-beta deposition in marrow may contribute to myelofibrosis, but the source of this cytokine in the absence of megakaryocytes requires further study.

The prevalence of oral cancer in relation to the ethnic origin of Israeli Jews

Smoking, alcohol, and familial background are considered major cofactors in the cause of oral cancer. The purpose of the present study was to determine the relationship between ethnic origin and oral cancer in the Israeli Jewish Population. Data were collected during the years 1970 to 1980 from 342 dental records of patients in Israeli hospitals. Results showed a male/female ratio of 2:1. Of 264 patients with clearly determined ethnic origin, 72% were Ashkenazi, 15% Sephardi, and 13% Eastern ethnic origin. The relative prevalence showed that the risk of the Ashkenazi group to develop oral cancer was at least twice as high as the other two ethnic groups. The increase in occurrence of oral cancer with age in each ethnic group was highly significant (p < 0.001). The most common type of malignancy was squamous cell carcinoma (95%) with 99% of this malignancy occurring in patients in their sixth and seventh decade. A significant (p < 0.02) relationship between site of involvement and ethnic origin was also noted. The tongue was the leading site in the Ashkenazi and Sephardi groups, whereas the lip and alveolar ridges were the most affected sites in the Eastern ethnic group.

Combination therapy with nucleoside analogs and alkylating agents

The nucleoside analog, 2'-deoxycoformycin (dCF), and the alkylating agents, chlorambucil (CLB) and cyclophosphamide, are effective agents in the treatment of chronic B cell leukemias and lymphomas. The cyclophosphamide analog, 4-hydroperoxycyclophosphamide (4-HC), generates the same active metabolite as cyclophosphamide in cells and has been used extensively for bone marrow purging in vitro. We have observed that deoxyadenosine (dAdo) plus dCF (dAdo/dCF) inhibit the repair of x-irradiation-induced and bleomycin-induced DNA damage in vitro, and that this results in either synergistic or additive cytotoxicity, respectively. In the present study we examined whether dAdo/dCF, can enhance the antitumor activity of CLB and 4-HC in chronic lymphocytic leukemia (CLL) cells in vitro. CLL cells were treated with CLB for 6 hr and then with dAdo/dCF for 18 hr and cytotoxicity was measured by the MTT assay. Synergy was observed between CLB and dAdo/dCF in CLL cells from 2 patients, with synergy increasing as the CLB dose was raised. In contrast, similar treatment of human bone marrow cells resulted in little or no synergistic cell kill. Treatment of CLL cells from 2 patients with 4-HC for 30 min followed by dAdo/dCF for 18 hr resulted in little synergistic cytotoxicity, although this drug combination did produce an additive cell kill. Thus, combination therapy with nucleoside analogs and alkylating agents may be useful for improving treatment of CLL.

Chlorambucil induced apoptosis in chronic lymphocytic leukemia (CLL) and its relationship to clinical efficacy

Chlorambucil induced apoptosis was measured in CLL cells treated with clinically achievable drug doses in vitro. While spontaneous apoptosis occurred in CLL cells incubated in vitro in the absence of drug, the level of apoptosis, as measured by the extent of DNA fragmentation, was greater in cells treated with chlorambucil. In addition, macrophages were shown to engulf drug treated CLL cells in vitro. To determine if chlorambucil can also induce apoptosis in vivo, CLL cells were isolated from patients before treatment and at intervals after clinical therapy with chlorambucil (0.9 mg/kg given over 3 days). Apoptosis was measured in these cells immediately after isolation and following incubation in vitro for 72 hr. No apoptotic changes were detected in cells immediately after isolation either before or after clinical treatment. In contrast, apoptosis was observed in cells that were incubated ex vivo for 72 hr, and the level of apoptosis was greater in cells that were isolated after chlorambucil treatment compared with cells obtained prior to therapy. The increased apoptosis observed in CLL cells ex vivo after therapy was related to the fall in the patient's lymphocyte count. In general, a large increase in apoptosis ex vivo after treatment was followed by a significant decrease in the patient's lymphocyte count. Thus, chlorambucil may produce its antitumor effect in CLL by inducing apoptosis-associated membrane changes that result in rapid clearance of the apoptotic cells by the immune system.

Activity of 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin in sensitive and resistant L5178Y lymphoblasts in vitro

An L5178Y murine lymphoblast cell line resistant to 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin (MRA-CN), L5178Y/MRA-CN, was isolated and characterized. L5178Y/MRA-CN cells were 9.6-fold resistant to MRA-CN compared with parental cells. The resistant cell line also displayed 2-fold resistance to 3'-(4-morpholinyl)-3'-deaminoadriamycin but was not cross-resistant to Adriamycin or chlorambucil. Uptake of MRA-CN was slightly reduced in the resistant cells compared to sensitive cells, but the distribution of the drug within the cells was unchanged. DNA interstrand cross-linking by MRA-CN was not significantly different in the sensitive and resistant cell lines, but MRA-CN was slightly less effective in inhibiting both DNA and RNA synthesis in L5178Y/MRA-CN cells compared with parental cells. NADPH cytochrome P-450 reductase activity was increased in L5178Y/MRA-CN cells compared to parental cells, while the activity of DT-diaphorase was decreased in the resistant cells. The levels of glutathione and glutathione S-transferase activity were increased in the resistant cells compared to sensitive cells; however, pretreatment of L5178Y/MRA-CN cells with buthionine sulfoximine to reduce the glutathione level did not reverse the resistance of these cells to MRA-CN. MRA-CN induced DNA fragmentation that was characteristic of apoptosis in both L5178Y and L5178Y/MRA-CN cells at equitoxic drug concentrations. However, apoptosis occurred more rapidly in L5178Y/MRA-CN cells compared with parental cells. Thus, MRA-CN induces apoptosis in L5178Y cells, and this effect may be important for the anti-tumor activity of this agent. In contrast, DNA interstrand cross-linking does not appear to be the primary mechanism responsible for the cytotoxicity of MRA-CN in these cells.

Prevention of insulin-dependent diabetes mellitus by 2'-deoxycoformycin in the BB Wistar rat

The effect of the adenosine deaminase (ADA) inhibitor 2'-deoxycoformycin (dCF) on the development of insulin-dependent diabetes mellitus (IDDM) was assessed in the BB Wistar rat. Sixty-one male rats were treated from days 30 to 120 with 0, 0.5, 1.0 or 1.5 mg dCF/kg/week. The incidence of IDDM was 78% in the controls and was significantly (P < 0.01) decreased in rats receiving 1.5 mg dCF/kg/week (32%), but not in rats receiving lower doses of the drug. However, for those rats that became diabetic the mean time to the development of IDDM was unchanged in animals receiving dCF compared with control. dCF treatment did not produce significant weight loss in the animals or gross changes in the thymus, spleen or kidneys. Although the protective effect of dCF against IDDM was likely produced by immunosuppression, the different dCF dosages had similar effects on ADA suppression in spleen or thymus and on dATP accumulation in these organs.

Electrophysiological studies of color processing in human visual cortex

Electrophysiological recordings from human visual cortex were carried out with electrodes chronically implanted in 13 patients for localization of an epileptogenic focus. Visual evoked potentials (VEPs) elicited by red or blue checkerboard stimuli were recorded using an adaptation stimulus-test stimulus design in which color was the most salient feature. A "significant color effect," defined as a statistically significant effect of the adaptation stimulus on test stimulus VEPs evoked by the same or a different color, was determined for various cortical regions: medial lingual gyrus, 20%; lateral lingual gyrus, 38%; posterior fusiform gyrus, 50%; anterior fusiform gyrus, 0%; inferior temporal gyrus, 5%; occipital pole, 30%; lateral surface of non-visual cortex, 6%; inferior parietal and temporal cortex, 5%. The time course of the significant color effects suggests that wave length-selective neuronal activity occurs initially at the first stage of cortical processing in the medial lingual gyrus, followed by progressively later activation of the lateral lingual gyrus, the posterior fusiform gyrus, and the inferior temporal gyrus. In two patients, stimulation of the lateral lingual and fusiform gyri elicited color sensations in the contralateral half-field, whereas stimulation of the medial lingual and cuneate gyri evoked retinotopically appropriate quadrantic "shimmering" devoid of color. These results suggest that a region of inferior occipital cortex, primarily the posterior portion of the fusiform gyrus, is involved in color perception and may be homologous with area V4 in monkeys. There is also a region of dorsolateral surface cortex which exhibits a fairly high percentage of significant color effects and when stimulated may evoke sensations of color. This region may be the same as the dorsolateral region thought to be involved in selective attention to color.

Role of NAD(P)H:(quinone acceptor) oxidoreductase (DT-diaphorase) in activation of mitomycin C under acidic conditions

The quinone antitumor agent mitomycin C is preferentially toxic to some cells under hypoxic and acidic conditions. The two-electron reducing enzyme DT-diaphorase may be a major contributor to mitomycin C activation under aerobic conditions, but its role in drug activation under hypoxic and acidic conditions is unclear. In this study, we observed that mitomycin C produced increased DNA cross-linking and cytotoxicity in Chinese hamster ovary cells at pH 6.6, compared with pH 7.2, under aerobic conditions, but drug activity was similar at these pH values under hypoxic conditions. The DT-diaphorase inhibitor dicoumarol completely inhibited the enhanced activity of mitomycin C at acidic pH under aerobic conditions but had no effect on DNA cross-linking or cytotoxicity under hypoxic conditions. These finding suggest that the enhanced activity of mitomycin C at acidic pH, in air, is due to increased drug activation by DT-diaphorase. However, the role of DT-diaphorase in activating mitomycin C under hypoxic conditions appears to be limited, even at acidic pH.

Role of transforming growth factor-beta in chronic lymphocytic leukemia

TGF-beta is an important immunoregulator as it suppresses proliferation and function of B- and T-lymphocytes. In the present study we have examined the cellular localization and secretion of TGF-beta in B-cells from normal donors and patients with CLL and have assessed the influence of TGF-beta 1 on DNA synthesis in these cells. Using anti-LC(1-30)--a polyclonal anti-TGF-beta 1 antibody--TGF-beta was localized to discrete sites within the cytoplasm of both normal and malignant lymphocytes. These areas co-localized with areas detected by an antigranule antibody (D545), suggesting that TGF-beta may be stored within cytoplasmic secretory vesicles. Both normal B- and CLL cells contained low or undetectable levels of TGF-beta mRNA and secreted low and equivalent amounts of TGF-beta. Compared to untreated cells, DNA synthesis was reduced by TGF-beta 1 to a mean +/- S. E. of 0.84 +/- 0.07 in CLL cells and this was significantly less (p < 0.001) than that observed in normal B-cells (mean +/- S. E. of control, 0.12 +/- 0.02). In 3 of the 18 patients, TGF-beta 1 stimulated DNA synthesis. The reduced inhibition of leukemic cell DNA synthesis by TGF-beta 1 in CLL may provide these cells with a growth or survival advantage over normal lymphocytes and contribute to their selective accumulation.

Inhibition of repair of bleomycin-induced DNA strand breaks by 2'-deoxycoformycin and its effect on antitumor activity in L5178Y lymphoblasts

We have observed previously that treatment of plateau-phase L5178Y murine lymphoblasts in vitro with 2'-deoxycoformycin plus deoxyadenosine (dCF/dAdo) can inhibit the repair of X-irradiation-induced DNA single-strand breaks (SSB) in these cells and that this effect is associated with synergistic cell kill. In this study we examined the effect of a combination treatment of plateau-phase L5178Y cells with bleomycin (BLM) plus dCF/dAdo. Incubation of BLM-treated cells with dCF/dAdo resulted in significant inhibition of the repair of BLM-induced DNA SSB. However, an additive, but not a synergistic, increase in cell kill was observed when cells were treated with a combination of BLM plus dCF/dAdo.

Induction of apoptosis in CD4+ prolymphocytic leukemia by deoxyadenosine and 2'-deoxycoformycin

The leukemic cells of a patient with CD4+ prolymphocytic leukemia were treated in vitro with 5 microM deoxyadenosine and 60 microM 2'-deoxycoformycin (dCF), an inhibitor of adenosine deaminase (ADA). Following treatment, the leukemic cell dATP level increased to 378 pmol/10(6) cells on day 3, after which the level plateaued. Apoptosis was apparent following 4 h of incubation, and by day 8 34% of the chromatin was fragmented. Apoptosis also occurred in control cells, but to a lesser extent than in drug-treated cells. When the patient was treated with dCF, 4 mg/M2 i.v. the leukemic cell ADA activity was inhibited 24 h following treatment, and the lymphocyte dATP content increased to 303 pmol/10(6) cells by day 6. The lymphocyte count fell 60% in 1 week, but during this time there was no evidence of apoptosis in these cells. Thus, if dCF induces apoptosis in vivo, the effete cells may be rapidly cleared from the circulation and thus elude detection.

Antiproliferative properties of aminosteroid antioxidants on cultured cancer cells

The antiproliferative properties of three 21-aminosteroid antioxidants (lazaroids), 21-[4-[5,6-bis(diethylamino)-2-pyridinyl]-1- piperazinyl]-16 alpha-methylpregna-1,4,9(11)triene-3,20-dione, hydrochloride (U74500A), 21-[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piper- azinyl]-pregna-1,4,9(11)-triene-3,20-dione, monomethanesulfonate (U74389F), 2H-1-benzopyran-6-ol, 2-[[4-[3-(ethylamino)-2-pyridinyl]-1-piperzinyl]methyl]-3,4- dihydro-2,5,7,8-tetramethyl-, (Z)-2-buten dioate (U78518F), on human breast cancer cells are described. U74500A inhibited cell proliferation in a dose-dependent manner with IC50 values of approximately 1.7 and 1.2 microM when cells were exposed to the drug for 3 and 5 days, respectively. The non-steroid antioxidants, alpha-tocopherol and nordihydroguaiaretic acid, showed weak or no activity at the same dose range. All three lazaroids inhibited, dose dependently, the proliferation of mouse lymphocytes but only at IC50 values ranging between 20-30 microM. The specificity of action was studied by including other steroids: progesterone, testosterone and hydrocortisone. Both sex hormones stimulated cell proliferation at low (less than 10(-5) M) concentrations but inhibited at higher doses with IC50 values of 26 (progesterone) and 80 (testosterone) microM. Hydrocortisone (IC50 0.17 microM), on the other hand, inhibited cell proliferation by 70% over a wide range of doses. Human breast cancer cells appear to have a greater sensitivity than the mouse lymphocytes to lazaroids. The antiproliferative effects of lazaroids in cancer cells may be, at least in part, due to an interaction with glucocorticoid receptors.

Role of NAD(P)H:(quinone acceptor) oxidoreductase (DT-diaphorase) in activation of mitomycin C under hypoxia

The role of the two-electron reducing enzyme DT-diaphorase in the activation of mitomycin C under hypoxic conditions was investigated. Mitomycin C activity was compared in L5178Y murine lymphoblasts, which have low levels of DT-diaphorase activity, and L5178Y/HBM10 cells, which have elevated levels of enzyme activity. The cytotoxic and DNA cross-linking activities of mitomycin C were greater in L5178Y/HBM10 cells than in L5178Y cells. In L5178Y/HBM10 cells, dicoumarol, an inhibitor of DT-diaphorase, decreased cell kill and DNA cross-linking by mitomycin C in air but had no significant effect on these activities under hypoxia. By comparison, in L5178Y cells, dicoumarol had no effect on drug activity under either aerobic or hypoxic conditions. A model for the activation of mitomycin C by both one-electron and two-electron reduction is proposed. Our findings suggest that two-electron reduction by DT-diaphorase has only a limited role in the activation of mitomycin C under hypoxic conditions, although this enzyme appears to be an important contributor to drug activation under aerobic conditions.

Role of glutathione and glutathione S-transferase in chlorambucil resistance

A chlorambucil (CLB)-resistant cell line, N50-4, was developed from the established mouse fibroblast cell line NIH 3T3, by multistep drug selection. The mutant cells exhibited greater than 10-fold resistance to CLB. Alterations in GSH and glutathione S-transferase (GST) were found in CLB-resistant variants. A 7-10-fold increase in cellular GSH content and a 3-fold increase in GST activity were detected in N50-4 cells, compared with parental cells, as determined by enzymatic assays. An increase in steady state levels of the GST-alpha isozyme mRNA was found in the CLB-resistant cells, as analyzed by Northern blotting. No GST gene amplification or rearrangement was shown by Southern blot analysis. To test the relative roles of GSH and GST in CLB resistance, a number of GSH- and GST-blocking agents were used. The CLB toxicity was significantly enhanced in N50-4 cells by administration of either the GSH-depleting agent buthionine sulfoximine or the GST inhibitors ethacrynic acid or indomethacin. The resistance to CLB cytotoxicity in N50-4 cells, however, was still significantly higher than that of parental cells. The resistance of N50-4 cells to CLB was almost completely abolished by combination pretreatment yielding both GSH depletion and GST inhibition. The results indicate that both increased cellular GSH content and increased GST activity play major roles in CLB resistance in N50-4 mutant cells.

Factors influencing the inhibition of repair of irradiation-induced DNA damage by 2'-deoxycoformycin and deoxyadenosine

Permeabilized L5178Y cells were used to investigate the mechanism underlying inhibition of the repair of irradiation-induced DNA strand breaks by 2'-deoxycoformycin combined with deoxyadenosine. Permeabilized cells repaired DNA strand breaks as effectively as did intact cells, and at deoxyadenosine concentrations that produced similar levels of deoxyadenosine triphosphate (dATP), repair of DNA strand breaks was inhibited by 2'-deoxycoformycin plus deoxyadenosine to a comparable extent in both types of cells. Accompanying the increase in intracellular dATP produced by 2'-deoxycoformycin combined with deoxyadenosine was a fall in levels of deoxythymidine triphosphate (dTTP), deoxyguanosine triphosphate (dGTP), and deoxycytidine triphosphate (dCTP). The addition of dTTP, dGTP, and dCTP reversed the inhibition of DNA repair by 2'-deoxycoformycin plus deoxyadenosine, although the level of dATP was not affected. Reducing the phosphorylation of deoxy-adenosine to dATP by the addition of adenosine prevented the decrease in levels of dTTP, dGTP, and dCTP and the inhibition of DNA repair by 2'-deoxycoformycin and deoxyadenosine. In contrast, increasing the intracellular levels of dATP by the addition of 2'-deoxycoformycin together with dATP, deoxyadenosine diphosphate (dADP), or deoxyadenosine monophosphate (dAMP) had no effect on the levels of the other deoxynucleotide triphosphates and did not inhibit DNA repair. Moreover, DNA repair was not inhibited by the breakdown products of deoxyadenosine, adenine, or deoxyribose. These results suggest that inhibition of the repair of irradiation-induced DNA strand breaks by 2'-deoxycoformycin combined with deoxyadenosine requires the phosphorylation of deoxyadenosine and involves alterations in the levels of deoxynucleotide triphosphates.

Mechanisms for the modulation of alkylating activity by the quinone group in quinone alkylating agents

Previous studies have demonstrated that the quinone group may play an important role in modulating the alkylating activity of quinone alkylating agents. Introduction of a quinone moiety markedly increased the alkylating activity and cytotoxic activity of the model quinone alkylating agents benzoquinone mustard and benzoquinone dimustard. However, the cytotoxic and DNA-damaging activity of benzoquinone mustard was considerably greater than that of benzoquinone dimustard. In this study, we have investigated the role of the quinone group as a modulator of alkylating activity in these antitumor agents, using extracellular assays to eliminate differences due to cellular drug uptake and metabolism. Evidence was obtained that the alkylating activities of both benzoquinone mustard and benzoquinone dimustard were enhanced by reduction of the quinone group. In addition, when these agents were reduced, they displayed equal alkylating activity. This finding suggests that the difference in the activity of these agents in cells is not due to intrinsic differences in alkylating activities of the activated forms of these agents. Electrochemical studies revealed that benzoquinone dimustard has a lower redox potential than benzoquinone mustard and, thus, is less easily reduced. Inactivation and spectroscopic studies suggested that a major reason for the differences in activity between benzoquinone mustard and benzoquinone dimustard may be the rapid inactivation of the dimustard before its reduction. This effect may be enhanced by the lower redox potential of benzoquinone dimustard, compared with benzoquinone mustard. These findings support the hypothesis that the quinone group can modulate the alkylating activity of quinone alkylating agents; however, the mechanisms by which this modulation occurs may vary for different antitumor agents.

Mechanisms of resistance to chlorambucil in chronic lymphocytic leukemia

The postulated biochemical mechanisms responsible for clinical resistance to chlorambucil (CLB) in chronic lymphocytic leukemia (CLL) have been examined. The total sulfhydryl, non-protein-bound sulfhydryl, protein-bound sulfhydryl (PSH) and glutathione (GSH) levels, in addition to glutathione S-transferase (GST) activities, were measured in the leukemic cells of 18 CLL patients. In addition, the formation and repair of DNA cross-links were measured following incubation of the cells with 100 microM chlorambucil in vitro. These parameters were then correlated with the subsequent clinical responses of the patients, as measured by the percent fall in lymphocyte count 3 weeks following 0.9 mg/kg chlorambucil. No correlations were observed between any of the individual parameters and clinical response, although a slight positive correlation was observed between the PSH:GSH ratio and clinical response. These findings suggest that multiple mechanisms may contribute to CLB-resistance in CLL.

Activity of quinone alkylating agents in quinone-resistant cells

The role of the quinone group in the antitumor activity of quinone alkylating agents, such as mitomycin C and 2,5-diaziridinyl-3,5-bis(carboethoxyamino)-1,4-benzoquinone, is still uncertain. The quinone group may contribute to antitumor activity by inducing DNA strand breaks through the formation of free radicals and/or by influencing the alkylating activity of the quinone alkylators. The cytotoxic activity and DNA damage produced by the model quinone alkylating agents, benzoquinone mustard and benzoquinone dimustard, were compared in L5178Y murine lymphoblasts sensitive and resistant to the model quinone antitumor agent, hydrolyzed benzoquinone mustard. The resistant cell lines, L5178Y/HBM2 and L5178Y/HBM10, have increased concentrations of glutathione and elevated catalase, superoxide dismutase, glutathione S-transferase, and DT-diaphorase activity. L5178Y/HBM2 and L5178Y/HBM10 cells were 7.4- and 8.5-fold less sensitive to benzoquinone mustard and 1.7- and 4.3-fold less sensitive to benzoquinone dimustard, respectively, compared with sensitive cells, but showed no resistance to the non-quinone alkylating agent, aniline mustard. The formation of DNA double strand breaks by benzoquinone mustard was reduced by 2- and 8-fold in L5178Y/HBM2 and L5178Y/HBM10 cells, respectively, while double strand break formation by benzoquinone dimustard was reduced only in the L5178Y/HBM10 cells. The number of DNA-DNA cross-links produced by benzoquinone mustard was 3- and 6-fold lower, and the number produced by benzoquinone dimustard was 35% and 2-fold lower in L5178Y/HBM2 and L5178Y/HBM10 cells, respectively, compared with L5178Y parental cells. In contrast, cross-linking by aniline mustard was unchanged in sensitive and resistant cells. Dicoumarol, an inhibitor of DT-diaphorase, increased the cytotoxic activity of both benzoquinone mustard and benzoquinone dimustard in L5178Y/HBM10 cells. This study provides evidence that elevated DT-diaphorase activity in the resistant cells contributes to resistance to benzoquinone mustard and benzoquinone dimustard, possibly by decreasing the formation of the semiquinone intermediates of these agents. The altered reduction of the quinone groups in the resistant cells may be responsible for the decreased DNA-DNA cross-linking and lowered induction of DNA strand breaks by the quinone alkylating agents. These findings demonstrate that the quinone group can modulate the activity of quinone alkylating agents. The study also suggests that the semiquinone intermediates of benzoquinone mustard and benzoquinone dimustard may be the active alkylating species of these two agents.

Glutathione S-transferase activity, sulfhydryl group and glutathione levels, and DNA cross-linking activity with chlorambucil in chronic lymphocytic leukemia

Glutathione (GSH) levels and glutathione S-transferase (GST) activities were measured in the leukemia cells of 12 patients with chronic lymphocytic leukemia. Both were correlated with prior clinical exposure to alkylating agents and with DNA cross-link formation by chlorambucil in these cells in vitro. No correlation was observed between prior exposure to alkylating agents and GSH level or GST activity. An inverse correlation was observed between GST activity and cross-linking by chlorambucil, which was enhanced if both GST activity and GSH level were related to cross-linking. These findings suggest that the combination of GST and GSH protects the DNA of leukemia cells from chlorambucil, but the role of this combination in clinical resistance remains to be determined.

Uptake and binding of 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin and 3'-(4-morpholinyl)-3'-deaminoadriamycin in L5178Y lymphoblasts in vitro

3'-(3-Cyano-4-morpholinyl)-3'-deaminoadriamycin (CMA) and 3'-(4-morpholinyl)-3'-deaminoadriamycin (MA) are analogues of Adriamycin, with altered cytotoxic activity. CMA is 100- to 1500-fold more cytotoxic than Adriamycin and possesses unique DNA crosslinking activity. Intact MA does not crosslink DNA and has a cytotoxicity equivalent to Adriamycin, but it retains its activity in anthracycline-resistant cells. In this study, uptake and binding of [3H]CMA and [3H]MA in L5178Y lymphoblasts were examined. Both CMA and MA were rapidly taken up by cells at 37 degrees C and concentrated almost exclusively in the nucleus. All of the intracellular MA was TCA-soluble, but only 45% of this drug effluxed from the cells by 4 hr. More than 50% of CMA in the cells was TCA-insoluble, and approximately 40% effluxed from the cells by 4 hr through loss of the TCA-soluble fraction. CMA differed from other alkylating agents in that more than 97% of the bound drug was associated with DNA. The bound drug was partially lost from the DNA by a process that may have involved DNA repair.

Characterization of the DNA-DNA cross-linking activity of 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin

3'-(3-Cyano-4-morpholinyl)-3'-deaminoadriamycin (CMA) is a highly potent analogue of the antitumor agent, Adriamycin (ADR), being up to 1500 times more cytotoxic both in vivo and in vitro. In contrast to ADR, CMA, and 5-imino-3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin (ICMA) have been shown to possess alkylating activity, as seen by their ability to produce DNA-DNA cross-links in human and murine tumor cells and in isolated lambda-phage DNA. We have compared the pharmacological activities of CMA, ICMA, and the alkylating agent, chlorambucil (CHL), in order to determine the roles of intercalation, the quinone ring, and DNA base composition, in cross-linking by CMA. CMA was 27-and 1000-fold more active than ICMA and CHL, respectively, in cross-linking DNA in L5178Y cells. In addition, the maximum level of cross-linking in L5178Y cells was reached more rapidly with CMA than with CHL, and the CMA cross-links were removed faster and more efficiently by these cells. CMA was 26- and 450-fold more active than ICMA and CHL, respectively, in producing DNA cross-links in isolated lambda-phage DNA. In contrast, the alkylating activity of CMA was only 6-fold greater than CHL, as measured by the ability of the drugs to bind to the nucleophile, p-nitrobenzyl pyridine. CMA was a better DNA intercalator than ICMA, whereas CHL did not intercalate. In addition, the intercalating agent, ethidium bromide, inhibited the cross-linking activity of CMA, but not that of CHL, suggesting that intercalation contributed to the cross-linking activity of CMA. CMA produced an increasing level of cross-linking, but showed no difference in intercalation, with isolated DNA of increasing G-C content, suggesting a preference for alkylating G-C bases. Both the cross-linking and intercalating, but not the alkylating, activities of CMA and ICMA were decreased by the reducing agent, sodium borohydride, providing additional evidence that the intercalative interaction of the ADR analogues with DNA contributes to their DNA cross-linking activity. Thus, alterations to the quinone group may effect the intercalating activity of these analogues and may contribute to the difference in cross-linking activity between CMA and ICMA.

Increased sensitivity of quinone resistant cells to mitomycin C

L5178Y cells resistant to the model quinone antitumor agent, hydrolyzed benzoquinone mustard, were four-fold more sensitive to mitomycin C compared to parental cells. Mitomycin C also produced increased DNA-DNA crosslinking in these cells compared to parental L5178Y cells, but did not induce DNA double strand breaks in either cell line. The resistant cells have a 24-fold increased level of DT-diaphorase activity, an enzyme that produces two electron reduction of quinone groups. Dicoumarol, an inhibitor of DT-diaphorase, significantly inhibited crosslinking and cytotoxicity by mitomycin C in the quinone resistant cells. These findings suggest that DNA-DNA cross-linking may be a major contributor to mitomycin C cytotoxic activity in L5178Y cells, and that the hydroquinone of mitomycin C may play a major role in the crosslinking activity of this agent.

Enhanced cytotoxicity and inhibition of DNA damage repair in irradiated murine L5178Y lymphoblasts and human chronic lymphocytic leukemia cells treated with 2'-deoxycoformycin and deoxyadenosine in vitro

The effects of irradiation were evaluated in L5178Y lymphoblasts treated with the adenosine deaminase inhibitor, 2'-deoxycoformycin, and deoxyadenosine. A synergistic antitumor effect was observed in resting cells between irradiation and 2'-deoxycoformycin/deoxyadenosine, with the dose required to reduce the surviving cell fraction to 0.1 being 25% lower than predicted for an additive effect. Synergy was enhanced with increasing deoxyadenosine concentration or with increasing radiation dose. When cells were treated with 2'-deoxycoformycin/deoxyadenosine for 1 h prior to irradiation, synergy was increased by prolonging postirradiation drug treatment. With 4-h postirradiation exposure to drug, varying the preirradiation incubation time did not affect synergy. In contrast, only a small enhancement of antitumor activity was observed in irradiated proliferating cells treated with 2'-deoxycoformycin/deoxyadenosine. Incubation of resting cells with 2'-deoxycoformycin/deoxyadenosine resulted in inhibition of the rate and extent of repair of radiation-induced DNA single strand breaks and an increase in dATP, but had no effect on NAD or ATP. With removal of drug, the dATP level fell rapidly and DNA repair resumed. Repair of DNA single strand breaks was more rapid in proliferating cells than in resting cells and was minimally affected by 2'-deoxycoformycin/deoxyadenosine, although the accumulation of dATP in these cells was 2-fold greater than in resting cells. The repair of DNA single strand breaks in chronic lymphocytic leukemia cells was as rapid as for proliferating L5178Y cells, but repair was significantly inhibited by 2'-deoxycoformycin/deoxyadenosine. These results suggest that 2'-deoxycoformycin/deoxyadenosine can function as a radiosensitizer, and this effect is associated with the cellular accumulation of dATP and inhibition of repair of DNA single strand breaks.

Characterization of L5178Y murine lymphoblasts resistant to quinone antitumor agents

The exact contribution of the quinone group to the activity of quinone antitumor agents remains uncertain. Two L5178Y murine lymphoblastic cell lines resistant to the model quinone antitumor agent, hydrolyzed benzoquinone mustard, and one partial-revertant cell line were isolated and characterized. The antitumor activity of hydrolyzed benzoquinone mustard has been shown previously to be due to its ability to induce free radical mediated DNA strand breaks. Resistant cells were obtained by growing a cloned L5178Y parental cell line in media containing increasing concentrations of hydrolyzed benzoquinone mustard. L5178Y/HBM2 cells were selected from L5178Y cells growing in media containing 0.2 mM drug, while L5178Y/HBM10 cells were selected from cells growing in media containing 1.0 mM drug. The L5178Y/HBMR cells were obtained by growing L5178Y/HBM10 cells in media without hydrolyzed benzoquinone mustard. The resistant cell lines, L5178Y/HBM2 and L5178Y/HBM10, were 2.5- and 6-fold less sensitive, respectively, to hydrolyzed benzoquinone mustard compared to parental cells, and this was accompanied by a decrease in the formation of DNA single and double strand breaks by this drug. The partial-revertant cell line, L5178Y/HBMR was 2.9-fold less sensitive to hydrolyzed benzoquinone mustard compared to parental cells. Drug uptake appeared to be lower in the resistant cells compared to parental cells. The resistant cells had a slightly elevated level of superoxide dismutase activity compared to parental cells, but there was no increase in the mRNA for superoxide dismutase nor any amplification of the gene for this enzyme. Intracellular catalase activities of the L5178Y/HBM2 and L5178Y/HBM10 cells were elevated by 1.25- and 2.6-fold, respectively, and the increased enzyme activity in the L5178Y/HBM10 cells appeared to result from a 3.6-fold increase in mRNA for this enzyme. Glutathione peroxidase activity was slightly elevated in L5178Y/HBM2 cells, but was unchanged in the other resistant cells. The L5178Y/HBM2 and L5178Y/HBM10 cells showed increased concentrations of glutathione and elevated levels of glutathione transferase activity. The resistant cell lines also had DT-diaphorase activity that was 3- and 24-fold higher in L5178Y/HBM2 and L5178Y/HBM10 cells, respectively, compared to sensitive cells. However, cytochrome P-450 reductase activity and the ratio of reduced to oxidized pyridine nucleotides was unchanged in the resistant cell lines. The partial-revertant cell line, L5178Y/HBMR, showed approximately the same level of resistance to hydrolyzed benzoquinone mustard as the L5178Y/HBM2 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin and structural analogues on DNA in HT-29 human colon carcinoma cells

The potent Adriamycin (ADR) analogue, 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin (CMA), produces DNA-DNA cross-links in human and murine tumor cells. The cellular pharmacology of CMA, its derivative, 5-imino-3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin (ICMA), 3'-(4-morpholinyl)-3'-deaminoadriamycin (MA), and ADR was evaluated in HT-29 human colon carcinoma cells to determine the structural requirements for the cross-linking activity of CMA, and the role of this activity in the antitumor effect of this agent. CMA was 50-fold more cytocidal than ICMA to HT-29 cells, 300-fold more toxic than MA, and 150-fold more potent than ADR. Both CMA and ICMA produced DNA-DNA cross-links in HT-29 cells but, consistent with its reduced cytotoxicity, the imino derivative was 30-fold less active than CMA. No DNA-DNA cross-links were observed with MA or ADR. CMA also showed cross-linking activity in isolated HT-29 nuclei, indicating that cytoplasmic activation was not required for this effect. Both CMA and ICMA produced cross-links in isolated lambda-phage DNA with CMA being 40-fold more active than the imino derivative, and this activity was unchanged in the presence or absence of a reducing agent. While MA and ADR produced DNA strand breaks in HT-29 cells, this damage was not observed with CMA and ICMA. This study indicates that the potent antitumor activity of CMA may be related to its ability to induce DNA cross-links, which can occur without the need for metabolic activation. The cyanide group appears to be essential for cross-linking and the quinone group may also be involved, but by a mechanism unrelated to its reduction.

Cellular pharmacology of 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin and structural analogues in human colon carcinoma HT-29 cells in vitro

The new Adriamycin (ADR) analogue, 3'-(3-cyano-4-morpholinyl)-3'-deaminoadriamycin (CMA), is the most potent anthracycline yet developed. The cellular pharmacology of CMA and 3'-(4-morpholinyl)-3'-deaminoadriamycin (MA), and their 5-imino derivatives, ICMA and IMA, were compared with ADR in a human colon carcinoma (HT-29) cell line in vitro. In a soft agar clonogenic assay, the order of antitumor activity was CMA greater than ICMA greater than ADR greater than MA greater than IMA, for both 2- and 24-h drug exposure periods, indicating a requirement for the cyanide group and an intact quinone ring for the potent antitumor effect of CMA. The cellular uptake of CMA was 2-fold less than that of MA, although, consistent with its greater nuclear binding, the degree of efflux of CMA was less than that of MA. The order of cytotoxicity of the analogues correlated approximately with their effects on cellular DNA synthesis, indicating that this feature may contribute to the antitumor effect. Using isolated nuclei, the order of inhibition of DNA transcription by the analogues was CMA greater than MA greater than ADR, which was similar to their nuclear affinities, suggesting that their effects on cellular nucleic acid synthesis were due to a direct interaction of drug with DNA. However, CMA did not appear to differ from the other drugs in its base specificity as all the analogues preferentially inhibited Escherichia coli RNA polymerase activity directed by poly(dAdT).poly(dAdT) compared to poly(dGdC).poly(dGdC).

Induction of DNA strand breaks in chronic lymphocytic leukemia following treatment with 2'-deoxycoformycin in vivo and in vitro

Four patients with refractory chronic lymphocytic leukemia were treated with the adenosine deaminase inhibitor, 2'-deoxycoformycin, and initially received 4 mg/m2 i.v. weekly. Clinical responses to therapy varied: Patient A had a minimal response; whereas Patient D showed an 85% decrease in lymphocyte count at 2 wk; and Patients B and C had intermediate responses. The pretreatment mononuclear cell adenosine deaminase activities, which ranged from 1.6 to 44.6 nmol adenosine/h/10(6) cells, decreased to approximately 1 nmol adenosine /h/10(6) cells 24 h following 2'-deoxycoformycin, and increased to 15 to 50% of the pretreatment activity prior to the second drug treatment. The clinical response to 2'-deoxycoformycin was unrelated to the pre- or posttreatment adenosine deaminase activities or to the rate of return of enzyme activities following treatment. The plasma deoxyadenosine levels and the leukemic cell dATP concentrations rose slightly with therapy, but there was no correlation between the magnitude of increase and clinical response. No significant levels of DNA strand breaks were observed in the leukemic cells following treatment, although the NAD levels decreased slightly in two patients. When peripheral mononuclear cells from the patients and two controls were incubated in vitro for 24 h with 2'-deoxycoformycin and increasing concentrations of deoxyadenosine, a concentration-dependent increase in dATP and decrease in NAD were observed in both the patients and normals. The normal cells, and cells from two patients, developed a significant number of DNA strand breaks. However, there was no relationship between the formation of DNA breaks and the degree of accumulation of dATP or depletion of NAD, or between any of these changes and subsequent clinical responses to 2'-deoxycoformycin. Based on this study, it appears that the antitumor activity of 2'-deoxycoformycin in chronic lymphocytic leukemia is unrelated to the induction of DNA strand breaks or to changes in the levels of dATP or NAD in the leukemic cells.

Effects of 3'-(4-morpholinyl)-3'-deaminodaunorubicin,3'- (4-methoxy-1-piperidinyl)-3'-deaminodaunorubicin and daunorubicin on nuclear and polysomal RNA synthesis in human colon carcinoma cells in vitro

The sugar amine modified anthracyclines, 3'-(4-morpholinyl)-3'-deaminodaunorubicin (MD) and 3'-(4-methoxy-1-piperidinyl)-3'-deaminodaunorubicin (MEO), are 10-fold more potent than daunorubicin (DAU) as inhibitors of RNA synthesis in human colon carcinoma (HT-29) cells in vitro, although they are 10-fold less cytocidal. In this study, HT-29 cells were exposed for 2 h to 5 X 10(-8) M MD or MEO, or 5 X 10(-7) M DAU; under these conditions total RNA synthesis is decreased by each drug by 50%, whereas cell viability is reduced more than 99% by DAU, but less than 10% by MD and MEO. Following the 2-h exposure, the cellular content of DAU was 2-4-fold greater than that of MEO and MD, respectively. All three drugs had a similar inhibitory effect on the different nuclear RNA fractions and preferentially reduced nucleolar RNA synthesis (44-49% inhibition) compared to heterogeneous RNA synthesis (5% inhibition). Polysomal RNA synthesis was inhibited to a greater degree than nuclear RNA synthesis by all the anthracyclines, and non-poly RNA synthesis was decreased by 50-60% and poly(A) RNA synthesis by 30%. When treated cells were incubated in drug-free medium for 2 h, RNA synthesis returned to 80% of the pretreatment level in MD and DAU treated cells, but by less than 10% in cells treated with MEO, and this difference was due to the more rapid cellular efflux of MD and DAU versus MEO. Thus, MD and MEO are inherently more potent inhibitors than DAU of RNA synthesis in HT-29 cells, but their reduced cytotoxicity cannot be attributed to differing effects on nucleolar or heterogeneous RNA synthesis, the nucleocytoplasmic transport of RNA, or the rate of return of RNA synthesis following drug treatment.

The retrocuspid papillae in Israeli Jews

The prevalence of an anatomic variation, called retrocuspid papilla, was determined in Israeli Jews. The distribution of the retrocuspid papillae, according to two age groups, and symmetry within the dental arch and in relation to ethnic origin were examined. Results showed that retrocuspid papillae were observed in 38.5% of the young group and in 11.3% of the adult group. Greater occurrence of bilateral than unilateral retrocuspid papillae was observed in each age group and in both sexes. No significant ethnic trend was found when the prevalence of retrocuspid papillae was examined in relation to the ethnic origin of the study sample.