Measurement of dicumarol-sensitive NADPH: (menadione-cytochrome c) oxidoreductase activity results in an artifactual assay of DT-diaphorase in cell sonicates

Purified DT-diaphorase can be assayed as either dicumarol-inhibitable NAD(P)H:menadione oxidoreductase or dicumarol-inhibitable NAD(P)H:dichlorophenolindophenol reductase. Both of these methods have been utilized to assay DT-diaphorase activity in tissue and cell homogenates. When DT-diaphorase activity was measured as dicumarol-inhibitable NADPH:dichlorophenolindophenol reductase in sonicates of two cell lines previously shown to not have any measurable activity of this enzyme, no enzymatic activity was detected. However, when the water-soluble bisulfite addition product of menadione was used as the electron acceptor, an artifactual activity for DT-diaphorase was detected in these cell lines. When another cell line was assayed utilizing menadione bisulfite, an apparent activity of about three times that found with dichlorophenolindophenol was measured, and thus, may overestimate DT-diaphorase activity in cells having activity. When menadione was used in place of menadione bisulfite, an artifactual DT-diaphorase activity was also detected, but was about one-half that obtained with menadione bisulfite. Polarographic determinations of the midpoint potentials for menadione and menadione bisulfite indicated that the latter compound was easier to reduce and may account for the greater apparent DT-diaphorase activity measured with this compound.

Overexpression of the multidrug resistance genes mdr1, mdr3, and mrp in L1210 leukemia cells resistant to inhibitors of ribonucleotide reductase

L1210 MQ-580 is a murine leukemia cell line resistant to the cytotoxic activity of the alpha-(N)-heterocyclic carboxaldehyde thiosemicarbazone class of inhibitors of ribonucleotide reductase. The line is cross-resistant to etoposide, daunomycin, and vinblastine. L1210 MQ-580 cells expressed 8-fold resistance to 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP), a relatively newly developed inhibitor of ribonucleotide reductase. The accumulation of [14C]3-AP by L1210 MQ-580 cells was 5- to 6-fold less than by parental L1210 cells. An increased rate of efflux of 3-AP was responsible for the lower steady-state concentration of 3-AP in resistant cells. In reverse transcription-polymerase chain reaction assays, L1210 MQ-580 cells were found to overexpress the multidrug resistance genes mdr1, mdr3, and mrp, but not the mdr2 gene, compared with parental L1210 cells. Measurement of the steady-state concentration of doxorubicin, a potential substrate for both the mdr and mrp gene products, demonstrated that L1210 MQ-580 cells accumulated 4-fold less anthracycline than parental cells. These findings indicate that drug efflux is a major determinant of the pattern of cross-resistance of L1210 MQ-580 cells. To extrapolate these observations to the human homologues of the mdr1, mdr3, and mrp murine genes, the effects of 3-AP were measured in L1210/VMDRC0.06 and NIH3T3 36-8-32 cells transfected with human MDR1 and MRP cDNAs, respectively. The transfectants were 2- to 3-fold resistant to the cytotoxic effects of 3-AP and accumulated less [14C]3-AP than their parental mock-transfected counterparts. Moreover, the cytotoxic activity of 3-AP was significantly greater in two double mrp gene knockout cell lines than in parental W 9.5 embryonic stem cells. Thus, the results suggest that 3-AP is a substrate for both the P-glycoprotein and MRP and that baseline MRP expression has the capacity to exert a protective role against the toxicity of this agent.

Clonal variability in beta-globin mRNA content in an interleukin-3-dependent bone marrow cell line transfected with the erythropoietin receptor before and after stimulation with erythropoietin

Unexpected clonal variability was observed in the content of beta-globin mRNA in erythropoietin receptor (EpoR)-transfected Ba/F3 cells before and after exposure to erythropoietin (Epo). Of 11 clones selected by virtue of G418 resistance and positive EpoR expression, 5 clones showed high levels of beta(major)-globin mRNA before Epo exposure, with subsequent Epo treatment causing little or no increase in globin mRNA. Five clones had undetectable levels of globin mRNA before Epo stimulation, and they did not accumulate globin mRNA when exposed to Epo, exhibiting resistance to the differentiation inducing action of Epo. Only one clone exhibited the expected phenotype, a low level of globin mRNA before exposure to Epo, and a significant Epo-dependent accumulation of globin mRNA. Phosphorylation of tyrosyl residues of the EpoR, Stat5, and JAK2 occurred upon Epo stimulation in clones representing each category. Furthermore, electrophoretic mobility shift assays using a Stat5 consensus sequence showed a difference in the nuclear binding component among these clones. These findings indicate that (1) the attainment of EpoR+ Ba/F3 clones with the anticipated sensitivity to both the growth and differentiation inducing actions of Epo is a rare event and (2) STAT5 transcription factors were differently activated by Epo in clones that differed in sensitivity to Epo.

Altered efflux properties of mouse leukemia L1210 cells resistant to 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone

A mouse leukemia L1210 cell line, denoted MQ-580, that was selected for resistance to the ribonucleotide reductase inhibitor, 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone (MAIQ), in addition to having altered properties at the ribonucleotide reductase site had other alterations that contributed to its resistant phenotype; these included the expression of p-glycoprotein and the multi-drug resistance associated protein (MRP). The efflux of rhodamine 123 (Rh-123) or daunomycin (Dau) was greatly increased in MQ-580 cells compared to parental wild-type (WT) cells. The effluxes of Rh-123 and Dau were ATP- and temperature-dependent. The p-glycoprotein inhibitors, verapamil, cyclosporin A and reserpine blocked the efflux of both Rh-123 and Dau. In contrast, the inhibitors of MRP, MK571, BSO-treatment, arsenite and genistein did not block the efflux of either Rh-123 or Dau from MQ-580 cells. These findings suggest that the p-glycoprotein is the major transporter involved in effluxing Rh-123 and Dau from MQ-580 cells.

Induction of the differentiation of HL-60 promyelocytic leukemia cells by vitamin E and other antioxidants in combination with low levels of vitamin D3: possible relationship to NF-kappaB

Epidemiological studies have provided evidence that diets rich in antioxidant nutrients may reduce the risk of cancer. To evaluate the possibility that dietary phytochemicals with antioxidant potential would create an environment capable of affecting the differentiation of HL-60 leukemia cells, we measured the effects of vitamin E and other dietary antioxidants on the differentiation produced by low levels of vitamin D3 and analogs thereof. Vitamin E succinate and other antioxidant compounds (ie butylated hydroxyanisole, beta-carotene and lipoic acid) used alone had no significant effect on the differentiation of HL-60 cells; however, these agents markedly increased the differentiation produced by vitamin D3. Previous studies from this laboratory have shown that a sequence-specific antisense phosphorothioate oligonucleotide to the Rel A subunit of NF-kappaB enhanced the differentiation of HL-60 cells produced by several inducing agents. Consistent with these observations, vitamin E succinate caused a marked reduction in the nuclear content of NF-kappaB both in the presence and absence of vitamin D3. These findings suggest that NF-kappaB may be a factor in regulating the differentiation of myeloid leukemia cells. The results also indicate that combinations of vitamin D3 and analogs thereof with dietary antioxidants may be useful in overcoming the differentiation block present in acute promyelocytic leukemia cells.

Chemotherapy as an adjunct to radiation in the treatment of squamous cell carcinoma of the head and neck: results of the Yale Mitomycin Randomized Trials

PURPOSE

Two consecutive randomized trials were run at our institution using the bioreductive alkylating agent mitomycin as an adjunct to radiation therapy in an effort to improve outcome in patients with squamous cell carcinoma of the head and neck.

METHODS

Between 1980 and 1992, two consecutive randomized trials using mitomycin (trial 1) and mitomycin with dicumarol (trial 2) as an adjunct to radiation therapy in patients with squamous cell carcinoma of the head and neck were conducted at our institution. The patients were stratified by intent of therapy, extent of disease, and primary tumor site. Within each strata, patients were randomized to receive radiation therapy with or without mitomycin (trial 1) or mitomycin/dicumarol (trial 2).

RESULTS

A total of 203 patients were enrolled onto both trials, 195 of whom were eligible for analysis. Patients were equally balanced with respect to sex, age, extent of disease, primary site, radiation dose, and total duration of radiation treatment. Hematologic toxicities were more frequently noted in the drug-treated arms, but were acceptable with no drug-related treatment deaths. Nonhematologic toxicities were acceptable and not significantly different between the two arms. As of September 1995, with a median follow-up of 138 months, a statistically significant benefit occurred in the mitomycin arms with respect to cause-specific survival (0.74 +/- 0.05 v 0.51 +/- 0.05; P = .005), local recurrence-free survival (0.85 +/- 0.04 v 0.66 +/- 0.05; P = .002), and local regional recurrence-free survival (0.76 +/- 0.05 v 0.54 +/- 0.05; P = .003). No statistically significant difference in overall survival was obtained (0.48 +/- 0.05 mitomycin arms v 0.42 +/- 0.05 radiation alone).

CONCLUSION

The bioreductive alkylating agent mitomycin is a safe and effective adjunct to radiation therapy in the treatment of squamous cell carcinoma of the head and neck. The statistically and clinically significant improvement in local regional relapse and cause-specific survival obtained support the use of mitomycin as an adjunct to radiation therapy in the management of squamous cell carcinoma of the head and neck.

Induction of the differentiation of HL-60 promyelocytic leukemia cells by curcumin in combination with low levels of vitamin D3

Previous studies have shown that an antisense phosphorothioate oligonucleotide to the Rel A subunit of NF- kappa B, as well as vitamin E and related antioxidants, significantly enhanced the differentiation of HL-60 leukemia cells when combined with low levels of 1 alpha, 25-dihydroxyvitamin D3 (vitamin D3) an effect accompanied by a marked inhibition of the transcription factor, NF-kappa B. Curcumin, a potent inhibitor of tumor promotion and of tumor cell growth, has also been shown to have antioxidant properties and to inhibit NF-kappa b. to ascertain whether curcumin would also enhance the differentiation of HL-60 leukemia cells produced by vitamin D3, presumably by interfering with NF- kappa B activity, the effects of curcumin on the differentiation of HL-60 cells produced by low levels of vitamin D3 were measured. Curcumin used alone did not produce a significant degree of differentiation of HL-60 cells; however, this agent markedly enhanced the expression of differentiation markers induced by low levels of vitamin D3. Curcumin also increased the differentiation of HL-60 cells when combined with vitamin D analogues (1,25-dihydroxy-16-ene-23-yne vitamin D3 and 1,25-dihydroxy-16-ene vitamin D3) that share the receptor binding properties of vitamin D3, whereas as vitamin D analogue (1,25-dihydroxy-16,23-diene vitamin D3) that caused significant calcium mobilization, but was less effective than vitamin d3 in binding the receptor, did not cause the differentiation of HL-60 cells in the presence or absence of curcumin. Several dietary compounds structurally related to curcumin (i.e., caffeic acid, chlorogenic acid, and ferulic acid) did not increase the differentiation of HL-60 cells produced by vitamin D3. However, the more lipophilic ethyl of ferulic and caffeic acid were capable of inducing the differentiation of HL-60 cells, as well as enhancing the maturation produced by vitamin D3. Curcumin caused a marked reduction in NF-kappa B activity in nuclear extracts of HL-60 cells exposed to this agent in the presence or absence of vitamin D3, supporting the possibility that NF-kappa B may be a factor in the regulation of the state of differentiation of leukemia cells.

The response of IL-3 dependent B6SUtA bone marrow cells to both erythropoietin and chemical inducers of differentiation

To develop cell lines which respond to both a physiological cytokine and chemical agents by the induction of differentiation pathway, factor dependent B6SUtA murine bone marrow cells were transfected with the erythropoietin receptor (EpoR). Clones were obtained that exhibited different sensitivities to erythopoietin (Epo), with one clone exhibiting erythroid differentiation in response to Epo, while in another Epo acted as a proliferation stimulus. Moreover, parental B6SUtA cells were sensitive to the initiation of differentiation by butyrate, diazepam and hemin. Thus, B6SUtA cells appear to represent a unique model to dissect the signaling molecules involved in the growth and differentiation pathways employed by Epo and non-physiological chemicals.

Double knockout of the MRP gene leads to increased drug sensitivity in vitro

Overexpression of the multidrug resistance-associated protein (MRP) gene has been implicated in the resistance of tumor cell lines to a wide array of chemotherapeutic agents, but its normal physiological function(s) remains unknown. We have compared the sensitivity to chemotherapeutic drugs and toxins of wild-type W9.5 embryonic stem cells (ES) and of single and double MRP gene knockout cells derived therefrom. MRP expression was totally abrogated in the double knockout cell line and partially abrogated in the single knockout cell line. Reverse transcription-PCR analyses demonstrated that the MDR1, MDR2, and MDR3 genes were not expressed in either wild-type or MRP knock-out cells. The cytotoxic activities of etoposide, teniposide, vincristine, doxorubicin, daunorubicin, and sodium arsenite were significantly greater in double knockout cells than in parental wild-type ES cells; single knockout ES cells displayed an intermediate level of sensitivity. In contrast, no difference in sensitivity to colchicine and 1-beta-D-arabinofuranosylcytosine existed between the cell lines. Etoposide accumulation in double knockout ES cells was 2-fold higher than in wild-type ES cells. These findings indicate that baseline MRP expression has the capacity to exert a protective role against the toxicity of multiple chemotherapeutic agents and natural toxins.

Microtubule-dependent multilobular organization of the nucleus in sensitive and multidrug-resistant L0 leukemia cells

The relationship between the nuclear morphology and the microtubular organization of L100 and L1000 cells, two vincristine-induced multidrug resistant human acute lymphocytic leukemia cell lines, was examined and compared to that of L0 parental cells. The L0 parental cells contained a round nucleus and the microtubules were evenly distributed throughout the cytoplasm. In contrast, the microtubules of the L100 and L1000 cells were localized between the lobular structures of a multilobulated nucleus. Disassembly of microtubules in L100 and L1000 cells by colchicine resulted in the loss of the multilobulated morphology of the nucleus. While the total cellular content of tubulin of L0 and L100 cells was similar, the content of microtubules of L100 cells was only 55% of that observed in L0 cells. Two, 28 kDa (pI 6.9) and 31 kDa (pI 4.4), microtubule-associated proteins were found to be overexpressed in L100 and L1000 cells. The results indicate that the multilobulated nuclear morphology of L100 and L1000 cells is dependent upon the unique and intact organization of the microtubules; the distinct organization of the microtubules and the multilobular nuclear morphology of the two resistant cell lines may be due to the differential expression of specific microtubule-associated proteins.

Bioactivation of mitomycin antibiotics by aerobic and hypoxic Chinese hamster ovary cells overexpressing DT-diaphorase

DT-Diaphorase catalyzes a two-electron reduction of mitomycin C (MC) and porfiromycin (POR) to reactive species. Many cell lines that overexpress DT-diaphorase and are sensitive to the mitomycins are protected from the aerobic cytotoxicity of these drugs by the DT-diaphorase inhibitor dicumarol. The cytoprotective properties of this relatively non-specific inhibitor, however, vanish under hypoxic conditions. To ascertain the role of DT-diaphorase in mitomycin bioactivation and cytotoxicity in living cells, a rat liver DT-diaphorase cDNA was transfected into Chinese hamster ovary cells. MC was equitoxic to the parental cells under oxygenated and hypoxic conditions. In contrast, POR was less toxic than MC to these cells under aerobic conditions, but significantly more toxic than MC under hypoxia. Two DT-diaphorase-transfected clones displayed increases in DT-diaphorase activity of 126- and 133-fold over parental cells. The activities of other oxidoreductases implicated in mitomycin bioreduction were unchanged. MC was more toxic to both DT-diaphorase-transfected lines than to parental cells; the toxicity of MC to the transfected lines was similar in air and hypoxia. POR was also more toxic to the DT-diaphorase-elevated clones than to parental cells under oxygenated conditions. Under hypoxia, however, the toxicity of POR to the transfected clones was unchanged from that of parental cells. The findings implicate DT-diaphorase in mitomycin bioactivation in living cells, but suggest that this enzyme does not contribute to the differential toxicity of MC or POR in air and hypoxia.

Synthesis and biological activity of 3- and 5-amino derivatives of pyridine-2-carboxaldehyde thiosemicarbazone

A series of 3- and 5-alkylamino derivatives, as well as other structurally modified analogues of pyridine-2-carboxaldehyde thiosemicarbazone, have been synthesized and evaluated as inhibitors of CDP reductase activity and for their cytotoxicity in vitro and antineoplastic activity in vivo against the L1210 leukemia. Alkylation of 3- and 5-amino-2-(1,3-dioxolan-2-yl)pyridines (1, 2) resulted in corresponding 3-methylamino, 5-methylamino, 3-allylamino, 5-ethylamino, 5-allylamino, 5-propylamino, and 5-butylamino derivatives (5, 6, and 11-15), which were then condensed with thiosemicarbazide to yield the respective thiosemicarbazones (7, 8, and 16-20). Oxidation of 3,5-dinitro-2-methylpyridine (21) with selenium dioxide, followed by treatment with ethylene glycol and p-toluenesulfonic acid, produced the cyclic ethylene acetal, 23. Oxidation of 2-(1,3-dioxolan-2-yl)-4-methyl-5-nitropyridine (26) with selenium dioxide, followed by sequential treatment with sodium borohydride, methanesulfonyl chloride, and morpholine afforded the morpholinomethyl derivative 30. Catalytic hydrogenation of 23 and 30 with Pd/C yielded the corresponding amino derivatives 24 and 31. Catalytic hydrogenation of 5-cyano-2-methylpyridine (33) with Raney nickel, followed by treatment with acetic anhydride, gave the amide derivative 35. N-Oxidation of 35, followed by rearrangement with acetic anhydride, produced the acetate derivative, 5-[(acetylamino)methyl]-2-(acetoxymethyl)pyridine (37). Repetition of the N-oxidation and rearrangement procedures with compound 37 yielded the diacetate derivative 39. Condensation of compounds 24, 31, and 39 with thiosemicarbazide afforded the respective 3,5-diaminopyridine-, 4-(4-morpholinylmethyl)-5-aminopyridine-, and 5-(aminomethyl)pyridine-2-carboxaldehyde thiosemicarbazones (25, 32, and 40). The most biologically active compounds synthesized were the 5-(methylamino)-, 5-(ethylamino)-, and 5-(allylamino)pyridine-2-carboxaldehyde thiosemicarbazones (8, 17, and 18), which were potent inhibitors of ribonucleotide reductase activity with corresponding IC50 values of 1.3, 1.0, and 1.4 microM and which produced significant prolongation of the survival time of L1210 leukemia-bearing mice, with corresponding optimum % T/C values of 223, 204, and 215 being obtained when administered twice daily for six consecutive days at dosages of 60, 80, and 80 mg/kg, respectively.

Spectrophotometric assay for processes involving changes in hydrogen ion concentration in aqueous solution

A strategy for the design of simple colorimetric assays to follow any process that involves the net generation or consumption of hydrogen ions in aqueous solutions over the pH range of 3-10 is described. This procedure relies upon the measurement of the change in absorption when a weakly or moderately buffered solution of a pH indicator is subjected to a small change in pH. Buffers and indicators are chosen with closely matching pKa values. The versatility of this type of assay technique is illustrated using three examples.

Detection of in vivo differentiation of murine WEHI-3B D+ leukemia cells transfected with the lac-Z marker gene using two-color flow cytometry

The in vivo induction of the differentiation of murine WEHI-3B D+ myelomonocytic leukemia cells was measured by flow cytometry, simultaneously staining leukemia cells for the marker exogenous beta-galactosidase and for differentiation by the antigen Mac-1 (CD11b/CD18). The WEHI-3B D+ leukemia cells were transfected with the E. coli lac-Z gene by electroporation and subclones that constitutively expressed high levels of the lac-Z gene product beta-galactosidase were established. Flow cytometric analyses of cells in the peritoneal cavities of mice bearing leukemia cells showed that cells continued to express beta-galactosidase for at least 14 days, and they were distinguishable from host-derived cells in vivo by their expression of the transfected gene. Simultaneous determination of the beta-galactosidase activity and Mac-1 content of cells in the peritoneal cavities of mice revealed that administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) to the mice enhanced the expression of Mac-1 antigen by beta-galactosidase-positive cells. The results demonstrate that G-CSF may have clinical potential as a therapeutic differentiating agent, and that flow cytometric analysis provides a useful in vivo system to evaluate the therapeutic potential of agents capable of inducing terminal differentiation.

Antitumor 2-(aminocarbonyl)-1,2-bis(methylsulfonyl)-1-(2-chloroethyl)- hydrazines

Several 2-(aminocarbonyl)-1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydr azi nes were synthesized and primarily evaluated for antitumor activity against the murine L1210 leukemia. All of the compounds tested were capable of producing "cures" of mice bearing this tumor. One of the most active agents of this class, 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)- 2(-)[[2-chloroethyl)-amino]carbonyl]hydrazine, was further evaluated against a spectrum of transplanted murine and human solid tumors. Pronounced activity was found against all of the tumors including the murine B16F10 melanoma, M109 lung carcinoma, M5076 reticulum cell sarcoma, and the human LX-1 lung carcinoma. The activities observed compared favorably with those of the established antitumor drugs, cyclophosphamide, mitomycin C, and the nitrosoureas, evaluated concomitantly.

Differential toxicity of mitomycin C and porfiromycin to aerobic and hypoxic Chinese hamster ovary cells overexpressing human NADPH:cytochrome c (P-450) reductase

Purified NADPH:cytochrome c (P-450) reductase (FpT; NADPH-ferrihemoprotein oxidoreductase, EC 1.6.2.4) can reductively activate mitomycin antibiotics through a one-electron reduction to species that alkylate DNA. To assess the involvement of FpT in the intracellular activation of the mitomycins, transfectants overexpressing a human FpT cDNA were established from a Chinese hamster ovary cell line deficient in dihydrofolate reductase (CHO-K1/dhfr-). The parental cell line was equisensitive to the cytotoxic action of mitomycin C under oxygenated and hypoxic conditions. In contrast, porfiromycin was considerably less cytotoxic to wild-type parental cells than was mitomycin C in air and markedly more cytotoxic under hypoxia. Two FpT-transfected clones were selected that expressed 19- and 27-fold more FpT activity than the parental line. Levels of other oxidoreductases implicated in the activation of the mitomycins were unchanged. Significant increases in sensitivity to mitomycin C and porfiromycin in the two FpT-transfected clones were seen under both oxygenated and hypoxic conditions, with the increases in toxicity being greater under hypoxia than in air. These findings demonstrate that FpT can bioreductively activate the mitomycins in living cells and implicate FpT in the differential aerobic/hypoxic toxicity of the mitomycins.

Differentiation of immortal cells inhibits telomerase activity

Telomerase, a ribonucleic acid-protein complex, adds hexameric repeats of 5'-TTAGGG-3' to the ends of mammalian chromosomal DNA (telomeres) to compensate for the progressive loss that occurs with successive rounds of DNA replication. Although somatic cells do not express telomerase, germ cells and immortalized cells, including neoplastic cells, express this activity. To determine whether the phenotypic differentiation of immortalized cells is linked to the regulation of telomerase activity, terminal differentiation was induced in leukemic cell lines by diverse agents. A pronounced downregulation of telomerase activity was produced as a consequence of the differentiated status. The differentiation-inducing agents did not directly inhibit telomerase activity, suggesting that the inhibition of telomerase activity is in response to induction of differentiation. The loss of telomerase activity was not due to the production of an inhibitor, since extracts from differentiated cells did not cause inhibition of telomerase activity. By using additional cell lineages including epithelial and embryonal stem cells, down-regulation of telomerase activity was found to be a general response to the induction of differentiation. These findings provide the first direct link between telomerase activity and terminal differentiation and may provide a model to study regulation of telomerase activity.

Synthesis and antitumor activity of 4- and 5-substituted derivatives of isoquinoline-1-carboxaldehyde thiosemicarbazone

Various substituted isoquinoline-1-carboxaldehyde thiosemicarbazones (12 compounds) have been synthesized and evaluated for antineoplastic activity in mice bearing the L1210 leukemia. Condensation of 4-bromo-1-methylisoquinoline (4) with ammonium hydroxide, methylamine, ethylamine, and N-acetylethylenediamine gave the corresponding 4-amino, 4-methylamino, 4-ethylamino, and 4-N-(acetylethyl)amino derivatives, which were then converted to amides and subsequently oxidized to aldehydes followed by condensation with thiosemicarbazide to yield thiosemicarbazones 8a-c, 9a-c, and 16. Nitration of 4, followed by oxidation with selenium dioxide, produced aldehyde 18, which was then converted to the cyclic ethylene acetal 19. Condensation of 19 with morpholine followed by catalytic reduction of the nitro group and treatment with thiosemicarbazide afforded 5-amino-4-morpholinoisoquinoline-1-carboxaldehyde thiosemicarbazone (22). N-Oxidation of 1,5-dimethylisoquinoline, followed by rearrangement with acetic anhydride, gave, after acid hydrolysis, 1,5-dimethyl-4-hydroxyisoquinoline, which was converted to its acetate and then oxidized to yield 4-acetoxy-5-methylisoquinoline-1-carboxaldehyde (32). Sulfonation of 1,4-dimethylisoquinoline, followed by reaction with potassium hydroxide, acetylation, and oxidation, gave 5-acetoxy-4-methylisoquinoline-1-carboxaldehyde (40). Condensation of compounds 32 and 39 with thiosemicarbazide afforded the respective 4- and 5-acetoxy(5- and 4-methyl)thiosemicarbazones 33 and 40, which were then converted to their respective 4- and 5-hydroxy derivatives 34 and 41 by acid hydrolysis. The most active compounds synthesized were 4-aminoisoquinoline-1-carboxaldehyde thiosemicarbazone (9a) and 4-(methylamino)isoquinoline-1-carboxaldehyde thiosemicarbazone (9b), which both produced optimum % T/C values of 177 against the L1210 leukemia in mice when used at a daily dosage of 40 mg/kg for 6 consecutive days. Furthermore, when 9a was given twice daily at a dosage of 40 mg/kg for 6 consecutive days, a T/C value of 165 was obtained and 60% of the mice were 60-day long-term survivors.

Increased rate of adenosine triphosphate-dependent etoposide (VP-16) efflux in a murine leukemia cell line overexpressing the multidrug resistance-associated protein (MRP) gene

WEHI-3B/NOVO is a cloned murine leukemia cell line selected for resistance to novobiocin that is cross-resistant to the cytotoxic action of etoposide (VP-16) and to a lesser extent to a variety of other topoisomerase II (topo II)-reactive drugs. We have reported previously (Cancer Res. 52: 2782-2790, 1992) that WEHI-3B/NOVO cells exhibit a pronounced decrease in VP-16 induced DNA-topo II cross-link formation compared to the parental WEHI-3B/S cell line in intact cells, in the absence of a significant difference in the P4 unknotting activity of topo II assayed in nuclear extracts. Because the pattern of cross-resistance was suggestive of a topo II-mediated mechanism, we have ascertained whether a change in topo II can account for the multidrug-resistant phenotype of WEHI-3B/NOVO cells. No differences existed between WEHI-3B/S and WEHI-3B/NOVO cells in topo II mRNA and protein levels, as well as in the amount of topo II associated with the nuclear matrix. Neither sensitive nor resistant cells expressed detectable levels of the MDR1 gene; however, VP-16 accumulation in WEHI-3B/NOVO cells was 3-4-fold less than that present in WEHI-3B/S cells, whereas doxorubicin accumulation was the same in both cell lines. Over the first 60 s, no difference existed in the rate of uptake of VP-16 between parental and resistant cells; however, beyond the first 60 s of incubation, [3H]VP-16 accumulated to a greater extent in parental sensitive cells. Thus, an increased rate of efflux of VP-16 was responsible for the lower steady-state concentration of the drug in resistant cells. The efflux Km for VP-16 in WEHI-3B/NOVO cells was 254.7 microM and the Vmax was 10.4 pmol/s/10(7) cells. In the presence of the inhibitors of energy metabolism, sodium azide and deoxyglucose, the efflux of VP-16 was markedly inhibited; readdition of glucose restored the original efflux rate. Northern blot analyses using the human 10.1 probe for the 3'-terminal region of the multidrug-resistance protein (MRP) cDNA revealed a mRNA species of approximately 6 kb in WEHI-3B/NOVO cells but not in WEHI-3B/S cells. Overexpression was associated with amplification of the cognate gene. To ascertain whether the overexpressed gene in WEHI-3B/NOVO cells was the murine MRP or a different member of the same superfamily of ATP-binding ABC cassette transporters, a 341-bp MRP cDNA probe was generated from a murine genomic library.(ABSTRACT TRUNCATED AT 400 WORDS)

The role of DNA ploidy in the differentiation of WEHI-3B D- leukemia cells transfected with the granulocyte colony-stimulating factor receptor gene

Granulocyte colony-stimulating factor (G-CSF) exerts various biological effects through occupancy of its receptor (G-CSFR). WEHI-3B D- myelomonocytic leukemia cells do not express the G-CSFR, do not respond to G-CSF or to retinoic acid by the induction of granulocytic maturation, contain a near tetraploid content of DNA, and form tightly aggregated colonies. However, they still maintain the capacity to differentiate since they respond to vitamin D3 by the formation of mature cells. Transfection of the G-CSFR gene into WEHI-3B D- cells resulted in three major changes. G-CSFR-expressing clones (a) acquired the capacity to respond to the differentiation-inducing properties of G-CSF and retinoic acid, (b) formed colonies which exhibited a dispersed phenotype, and (c) exhibited near diploid DNA ploidy. In contrast, WEHI-3B D- cells transfected with vector alone behaved like parental WEHI-3B D- cells. The findings imply that the near diploid phenotype is required for WEHI-3B D- leukemia cells to respond to certain inducers of differentiation.

Preferential kill of hypoxic EMT6 mammary tumor cells by the bioreductive alkylating agent porfiromycin

Hypoxic cells in solid tumors represent a therapeutically resistant population that limits the curability of many solid tumors by irradiation and by most chemotherapeutic agents. The oxygen deficit, however, creates an environment conducive to reductive processes; this results in a major exploitable difference between normal and neoplastic tissues. The mitomycin antibiotics can be reductively activated by a number of oxidoreductases, in a process required for the production of their therapeutic effects. Preferential activation of these drugs under hypoxia and greater toxicity to oxygen-deficient cells than to their oxygenated counterparts are obtained in most instances. The demonstration that mitomycin C and porfiromycin, used to kill the hypoxic fraction, in combination with irradiation, to eradicate the oxygenated portion of the tumor, produced enhanced cytodestructive effects on solid tumors in animals has led to the clinical evaluation of the mitomycins in combination with radiation therapy in patients with head and neck cancer. The findings from these clinical trials have demonstrated the value of directing a concerted therapeutic attack on the hypoxic fraction of solid tumors as an approach toward enhancing the curability of localized neoplasms by irradiation.