Showing papers by "Japanese Foundation for Cancer Research published in 1990"

Decreased expression of DNA topoisomerase I in camptothecin-resistant tumor cell lines as determined by a monoclonal antibody.

Abstract: DNA topoisomerase I (topo I) has been identified as a principal target of a plant alkaloid camptothecin (CPT) and its derivative (CPT-11). The latter compound is expected to be a clinically useful antitumor agent. Three human tumor cell lines resistant to CPT (A549/CPT, HT-29/CPT, St-4/CPT) were isolated in vitro, and a murine tumor cell line resistant to CPT-11 (P388/CPT) was isolated in vivo by continuous exposure of the drugs. A549/CPT, HT-29/CPT, and St-4/CPT showed 1.8-, 6.9-, and 8.8-fold more resistance to CPT, and P388/CPT showed 45-fold more resistance to CPT than did the parental line. To examine the possible involvement of topo I in drug-resistant mechanisms, a monoclonal antibody was developed by using purified human topo I as antigen. The antibody T14C (immunoglobulin G1) recognized both human and murine topo I, as shown by Western blot analysis. By using this monoclonal antibody, cellular contents of topo I were examined in CPT-resistant tumor lines. Respective contents of topo I in HT-29/CPT, St-4/CPT, and P388/CPT were approximately 8-, 4-, and 3-fold less than those in their parental cell lines. A549/CPT, a weak CPT-resistant line, possessed amounts of topo I similar to those of the parental line. HT-29/CPT showed lower topo I activity than did the parental HT-29 in the nuclear extracts and in the hydroxylapatite column-eluted fractions. Purified topo I from HT-29 and HT-29/CPT showed similar catalytic activity when the same amounts of protein were used. These results indicate that the quantitative reduction of topo I content seems to be the most frequently occurring event in the development of resistance to camptothecin.

Elevated Expression of DNA Topoisomerase II in Camptothecin-resistant Human Tumor Cell Lines

Abstract: In a previous study, we established camptothecin (CPT)-resistant cell lines, A549/CPT and HT-29/CPT, from human lung cancer A549 and human colon cancer HT-29 A549/CPT was shown to express similar amounts of DNA topoisomerase I (topo I) as the parental line, and HT-29/CPT was shown to express lower amounts of topo I than its parental line DNA topoisomerases I and II are known to be functionally related In the present study, the possible alterations in topo II expression were examined in these human CPT-resistant lines In A549/CPT and HT-29/CPT, the cellular contents of topo II and its mRNA were elevated over that seen in each parental line Nuclear extracts from A549/CPT and HT-29/CPT showed higher topo II activity than those from the corresponding parental lines when the same amounts of nuclear protein were used Topo II was partially purified from HT-29 and HT-29/CPT by hydroxylapatite column chromatography, and the enzyme activities were compared HT-29/CPT showed higher topo II activity in the hydroxylapatite column-eluted fractions that HT-29 These results indicate the possible activation of topo II expression in the CPT-resistant cell lines

In vitro and in vivo release of soluble erbB-2 protein from human carcinoma cells.

Abstract: An enzyme-linked immunosorbent assay (ELISA) was developed to measure soluble erbB-2 protein in culture supernatants of various human cell lines and sera of patients suffering from recurrent breast carcinoma. Soluble erbB-2 protein was demonstrated in culture supernatants of cell lines that expressed high levels of erbB-2 protein as shown by western blot analysis of cell lysates. Increased levels of the protein, 40- to 190-fold higher than in healthy controls, were demonstrated in sera of 3 out of 12 patients with breast carcinomas. On immunohistological study of tumor tissues from 9 patients, high immune reaction with the anti-erbB-2 protein antibody was observed in 2 cases. These were two of the three patients who had elevated levels of erbB-2 protein in serum (a sample was not available from the third patient). These results raise the possibility that soluble erbB-2 protein level in serum can be used as an indicator for spread of carcinomas that overexpress erbB-2 protein.

Specialized localization of P-glycoprotein recognized by MRK 16 monoclonal antibody in endothelial cells of the brain and the spinal cord.

Abstract: This communication describes the cellular and ultrastructural localization in the central nervous system of P-glycoprotein (P-GP) recognized by a murine monoclonal antibody, MRK 16. At the ultrastructural level P-GP was strictly confined to the luminal surface of the endothelial cells which comprise the capillary vessels of the brain and the spinal cord. No P-GP was found in the endothelial cells of other organs. Our findings may be useful as a means to define the blood-brain barrier, and they imply that the blood-brain barrier is anatomically characterized by the presence of intercellular tight junctions between continuous nonfenestrated endothelial cells.

Modulation of multidrug resistance by verapamil or mdr1 anti-sense oligodeoxynucleotide does not change the high susceptibility to lymphokine-activated killers in mdr-resistant human carcinoma (LoVo) line.

Abstract: Two sublines were derived from the colon adenocarcinoma line LoVo, the first one was sensitive (LoVo/H) and the second one was made resistant to doxorubicin (LoVo/Dx). When tested for susceptibility to lysis by different types of immune effectors, LoVo/Dx appeared more sensitive than LoVo/H to the killing of CD3+CD5+CD16-, CD3- CD16+)-enriched lymphokine activated killers (LAK) or activated macrophages. In order to check whether this effect was due to different expression of glycoprotein P170 between the two LoVo sublines (30% vs. 90% of positive cells), a pharmacological and genetic modulation of P170 was carried out in LoVo cells. Treatment of LoVo/Dx with the calcium channel blocker verpamil (VRP), strongly impaired P170 function as evaluated by reduced Dx resistance, without affecting the lysability of LoVo/Dx cells by LAKs. Moreover, the significant inhibition of P170 expression resulting from the treatment of LoVo/Dx with mdr1 anti-sense olideoxynucleotide also failed to change the high lysability of LoVo/Dx by LAKs. These results, therefore, indicate that molecules other than P170 are involved in the increased lysis of LoVo/Dx subline by immune effectors and that down-regulation of the P170 expression or function will not reduce the potential effectiveness of cancer chemo-immunotherapy.

Effect of granulocyte colony-stimulating factor on neutropenia due to chemotherapy for non-Hodgkin's lymphoma.

Abstract: The authors administered recombinant human granulocyte colony-stimulating factor (rhG-CSF) to 16 patients with advanced non-Hodgkin's lymphoma treated with combination chemotherapy. Groups of three to five patients were treated with 50, 100, 200, and 400 micrograms/m2 per day of rhG-CSF by intravenous infusion for 14 days, beginning 3 days after chemotherapy. There was a strong linear relationship between the dose and the area under the curve over this dose range. The rhG-CSF was rapidly cleared from serum, with a mean half-life of 5.97 hours for the second phase (t1/2). In patients treated with a dose of more than 100 micrograms/m2 per day, the duration of neutropenia (P less than 0.01) and the duration of fever (P less than 0.05) were significantly decreased. The rhG-CSF was well tolerated and the only clinical observation that appeared relating to rhG-CSF administration was slight bone pain. This study strongly suggests that an optimum dose of rhG-CSF in patients after chemotherapy is 100 to 200 micrograms/m2. Our study shows that rhG-CSF is a clinically useful drug for patients treated with myelosuppressive chemotherapy.

Mouse-human chimeric antibody against the multidrug transporter P-glycoprotein.

Abstract: In an effort to devise an effective treatment for human drug-resistant cancers, we have generated a monoclonal antibody, MRK16, reactive to the multidrug transporter P-glycoprotein. The monoclonal antibody inhibited the growth of human drug-resistant tumor cells in a xenograft model, suggesting its potential usefulness in the immunotherapy of drug-resistant cancers. In this study, we have developed a recombinant chimeric antibody in which the antigen-recognizing variable regions of MRK16 are joined with the constant regions of human antibodies. When human effector cells were used, the chimeric antibody, MH162, was more effective in killing drug-resistant tumor cells than the all-mouse monoclonal MRK16. The chimeric antibody against the multidrug transporter P-glycoprotein will be a useful agent in immunotherapy of human drug-resistant cancers.

Kinetic analysis of 5-fluorouracil action against various cancer cells.

Abstract: Based on our recent kinetic analysis, which made it possible to distinguish between the cell-killing actions of cell cycle phase-specific and non-specific agents, we attempted to elucidate the actions of 5-fluorouracil (FUra) on three different cancer cell lines. By colony-forming assay, the concentrations of fluorouridine (FUrd), fluorodeoxyuridine (FdUrd) or FUra giving 90% cell kill (IC90) at various exposure times (texps) were obtained. With P388 cells, the curve of texps-IC90 for FUrd on a log-log scale was linear with a slope of — 1, which is typical for cell cycle phase-nonspecific agents. In contrast, the curve for FdUrd showed a much steeper slope than —1, which is characteristic for cell cycle phase-specific agents. We found that the curve for FUra was exactly the same as that for FUrd, indicating that the mode of FUra action on P388 leukemia is analogous to that of FUrd. Similar results were observed with human colon and renal cancer cell lines, HT-29 and KU-2, although when the cells were exposed to relatively low concentrations of FUra for a long time, a cell cycle phase-specific action became evident.

Monoclonal anti-P-glycoprotein antibody-dependent killing of multidrug-resistant tumor cells by human mononuclear cells.

Abstract: Mouse monoclonal antibodies (MRK16 and MRK17) against human multidrug-resistant cancer cell lines were tested for antibody-dependent cytotoxicity mediated by human blood mononuclear cells, using a 4-h 51Cr release assay. MRK16 (IgG2a isotype) was shown to be more effective than MRK17 (IgG1 isotype). Moreover, when four pairs of drug-resistant and their parent sensitive human cancer cells were tested for antibody-dependent cell-mediated cytolysis (ADCC) using MRK16, only the drug-resistant cell lines were susceptible to ADCC reaction. When highly purified lymphocytes (greater than 99%) and monocytes (greater than 97%) were isolated from blood mononuclear cells by centrifugal elutriation and adherence, MRK16 promoted both lymphocyte- and monocyte-mediated tumor cell killing, whereas MRK17 induced only a lymphocyte-mediated ADCC reaction. These results suggest that MRK16 of IgG2a subtype may be a useful therapeutic agent in eradication of drug-resistant cancer cells expressing P-glycoprotein through ADCC reaction.

Expression of a Mr 41,000 glycoprotein associated with thrombin-independent platelet aggregation in high metastatic variants of murine B16 melanoma.

Abstract: In the previous study, we generated a monoclonal antibody, 8F11, against NL-17, a high metastatic clone derived from a metastatic variant of murine colon adenocarcinoma 26.8F11 inhibited platelet aggregation induced by NL-17 and recognized a M r 44,000 membrane protein as antigen. In the present study, the reactivity of 8F11 to murine B16 melanoma and its metastatic variants was examined, and the antigen recognized by 8F11 on the cell surface was characterized. 8F11 was found to strongly react with 3 metastatic variants of B16 melanoma. In contrast, only slight reactivity was observed with parent B16 melanoma. The reactivity of the antibody to these cells was in the order B16F10 > B16BL-6 > B16F1 ≫ B16. Western blot analysis showed a M r 41,000 protein as the antigen recognized by 8F11 on the cell surface of B16F10 cells. The M r 41,000 antigen appeared to be a glycoprotein that bound to wheat germ agglutinin as has been observed for the M r 44,000 antigen of NL-17. To elucidate the functional role of the M r 41,000 antigen in B16 melanoma, platelet aggregation induced by B16 and B16F10 was compared. B16 was reported to stimulate platelet aggregation by the generation of thrombin, whereas B16F10 was found to activate platelet by at least 2 mechanisms: one dependent on thrombin and the other independent on thrombin. The activity of B16 and its metastatic variants to induce platelet aggregation in the presence of MD805, a synthetic antagonist of thrombin, well correlated with the reactivity of 8F11 to these cells. 8F11 blocked platelet activation by B16F10 under conditions preventing thrombin activity such as enzymatic formation of lysolecithin through the treatment of the cell surface with phospholipase A2 or in the presence of MD805. These data indicate that M r 41,000 glycoprotein recognized by 8F11 on metastatic variants of B16 melanoma is involved in the thrombin-independent platelet aggregation. A positive correlation was observed between the levels of M r 41,000 glycoprotein expression of B16 and its metastatic variants and their pulmonary metastasis after i.v. injection, suggesting M r 41,000 glycoprotein, as well as other factors reported previously, may play an important role in the hematogenous spread of B16 melanoma.

Low Metastatic Potential of Clone From Murine Colon Adenocarcinoma 26 Increased by Transfection of Activated c-erbB-2 Gene

Abstract: We investigated the effect of an activated c-erbB-2 gene (also known as ERBB2) on metastatic potential. The c-erbB-2 gene was activated by mutation of the valine at position 659 within the transmembrane domain to glutamic acid. The activated c-erbB-2 expression vector was transfected into low-metastatic-potential NL-4 cells, which were established from a metastatic variant of murine colon adenocarcinoma 26. All 10 clones produced lung metastases in BALB/c mice injected via the tail vein. Eight of the 10 clones expressed messenger RNA (mRNA) of activated c-erbB-2 and showed morphological alteration; seven of the eight produced significantly enhanced experimental metastatic activity compared with that of untransfected NL-4 or NL-4neo cells, and one had metastatic ability similar to that of NL-4 cells. Two clones did not express c-erbB-2 mRNA and did not show morphological alteration or highly metastatic phenotype. Five of the 10 clones subcutaneously implanted in the flank failed to produce metastasis in the lungs or other organs of the mice. The metastatic ability of the other five clones was not determined. These results indicate that the activated c-erbB-2 gene can enhance experimental but not spontaneous metastatic potential in NL-4 cells, suggesting participation of the gene in the metastatic process after initial arrest and lodgement in the capillary bed.

In vitro bone marrow purging of multidrug-resistant cells with a mouse monoclonal antibody directed against Mr 170,000 glycoprotein and a saporin-conjugated anti-mouse antibody.

Abstract: Selective elimination f multidrug resistance-positive cells (LoVo/Dx) was obtained by using the monoclonal antibody MRK 16, which recognizes a surface epitope of the M r 170,000 glycoprotein, and a sheep antimouse immunoglobulin antibody, conjugated to the ribosome-inactivating protein saporin 6. The killing was greatly decreased or even abolished by adding the monoclonal antibody at a 100-fold concentration. Both the MRK 16 and anti-mouse saporin 6 conjugate did not show any killing activity when they were used separately. In cell suspensions composed of 90% normal bone marrow cells and 10% multidrug resistance-positive cells, the monoclonal antibody MRK 16 followed by the anti-mouse immunotoxin caused the elimination of 99% multidrug resistance-positive cells, as revealed by immunofluorescence and immunocytochemistry as well as by a clonal assay. Human normal hematopoietic precursors (granulomonocytic colony-forming units, erythroid burst-forming units, and multipotent granulomonocytic, erythroid, and megakaryocytic-forming units) were not affected by the MRK 16 plus immunotoxin treatment. This technique might be suitable for ex vivo bone purging in an appropriate clinical setting, such as autologous bone marrow transplantation.

Antitumor activity of MST-16, a novel derivative of bis(2,6-dioxopiperazine), in murine tumor models.

Abstract: We studied the antitumor activity of newly synthesized bis(1-acyloxymethyl) derivatives of 4,4′-(1,2-ethanediyl)bis(2,6-piperazinedione) using i.p.-i.p. models of P388 leukemia and B16 melanoma. As a result, we found 4,4′-(1,2-ethanediyl)bis(1-isobutoxycarbonyloxymethyl-2,6-piperazinedione) (MST-16) to possess considerable therapeutic activity. MST-16 showed not only marked life-prolonging effects in both P388 leukemia- and B16 melanoma-bearing mice but also a greater therapeutic ratio than did its parent compounds, ICRF-154 and ICRF-159. Further studies revealed that MST-16 has considerable therapeutic activity against a number of other tumors such as ascitic forms of L1210 leukemia, colon 26 adenocarcinoma, and MH-134 hepatoma and solid forms of B16 melanoma, Lewis lung carcinoma, colon 38 adenocarcinoma, and M5076 fibrosarcoma. These results suggest that MST-16 is very promising as an antitumor agent.

Prediction of ACNU plasma concentration-time profiles in humans by animal scale-up.

Abstract: Plasma concentration-time profiles of nimustine hydrochloride, 1-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU), in the mouse, rat, rabbit, and dog were determined by high-performance liquid chromatographic analysis. The pharmacokinetic parameters for these four animal species and previously reported clinical data were analyzed for investigation of interspecies correlation. Loglog plots of body weight (W; kg) vs total plasma clearance (CLtot, p; ml/min) and steady-state distribution volume (Vd, ss; 1) for the four animal species were linear, with high correlation coefficients (r 0.996 for both parameters), despite the fact that the nonrenal clearance was >97% in these species. Linear regression on the plots excluding human data yielded allometric equations (CLtot,p=50.6 W0.957; Bd, ss=1.29 W1.03) that were extrapolated to predict ACNU pharmacokinetic parameters in humans. For both parameters, however, there were 3-fold differences between the predicted and observed parametric values. To investigate these discrepancies, we measured serum protein binding of ACNU in these animal species and in humans. The values of CLtot,p and Vd,ss were converted into those of CLu tot,p and Vd,u ss, which correspond to the parameters for unbound ACNU. In this case, correlation coefficients of the log-log plots excluding human data (CLu tot,p=71.7 W0.891; Bd,u ss=1.82 W0.966) were also high (r≥0.991). The extrapolated values vs those observed in a 70-kg human were the following: CLu tot,p, 3,160 vs 2,290 ml/min; Vd,u ss, 110 vs 1061. Thus, the animal data were successfully extrapolated to yield better predictions of human pharmacokinetic parameters if the analysis was based on the unbound plasma concentration of ACNU. In addition, the predicted plasma concentration-time profile for humans also showed good agreement with the observed ones. These results suggest the importance of measuring unbound fractions of drugs for more accurate prediction of human pharmacokinetic parameters by extrapolation of animal data to the human situation.

Postoperative adjuvant immunochemotherapy with mitomycin C, tegafur, PSK and/or OK-432 for gastric cancer, with special reference to the change in stimulation index after gastrectomy.

Abstract: In order to evaluate the efficacy of combined immunochemotherapy with mitomycin-C, tegafur, PSK and/or OK-432 as an adjunct for curatively resected gastric cancer, a prospective randomized controlled study using the envelope method was performed, in which 266 institutions from around Japan participated. The 3 year survival rates for all cases, and for ps(+)·n(+) cases, were insignificantly higher in the immunochemotherapy groups receiving PSK and/or OK-432 than in the control group. However, because 28.2 per cent of the cases were excluded from the final statistical analyses, the results of this study may have questionable statistical credibility. Changes in the stimulation index (SI) suggest that the administration of PSK may result in an inhibition of the immunosuppressive activity of cancer patients. The high SI group showed a significantly higher 4 year survival rate than the low SI group.

Antitumor activity of a derivative of mitomycin, 7-N-[2-[[2-(γ-l-glutamylamino)ethyl]dithio]ethyl]mitomycin C (KW-2149), against murine and human tumors and a mitomycin C-resistant tumor in vitro and in vivo

Abstract: The antitumor activity of a mitomycin derivative, 7-N-[2-[[2-(γ-glutamylamino)ethyl]dithio]ethyl]mitomycin C (KW-2149), was evaluated in murine and human tumor models, including a mitomycin C (MMC)-resistant tumor in vitro and in vivo. KW-2149 showed a profound effect against i.p. inoculated P388 leukemia on both a single and an intermittent administration schedule. Against s.c. implanted colon adenocarcinoma 38 (colon 38), KW-2149 was as effective as MMC in ILS% and in tumor growth inhibition on a single-administration schedule. Both compounds were similarly effective when an intermittent schedule was used. KW-2149 showed activity against human tumor xenografts and was effective in two of four non-small-cell lung carcinomas but was not effective against three gastric adenocarcinomas on the singleadministration regimen. The activity of KW-2149 against gastric adenocarcinoma was inferior to that of MMC on a single-administration schedule. However, the antitumor activity of KW-2149 was higher on an intermittent schedule than on a single-administration regimen. The antitumor activity of KW-2149 against human tumor xenografts was similar to that of MMC on an intermittent schedule, and the former drug was effective against both gastric adenocarcinomas and both non-small-cell lung carcinomas. KW-2149 was more effective than MMC against a subline of P388 leukemia that is resistant to MMC in vitro as well as in vivo.

Increased expression of the multidrug-resistance gene in undifferentiated sarcoma.

Abstract: We analyzed multidrug-resistance gene (mdr1 gene) expression in a patient with undifferentiated sarcoma of the liver using the cloned cDNA for the mdr1 gene. Tissue samples were available at the time of initial diagnosis and of two intracranial relapses after chemotherapy with a regimen including doxorubicin and teniposide. The level of mdr1 gene expression was increased sevenfold in the intracranial tumor at the time of first relapse and 11-fold at the second relapse. This case may be an example of acquired multidrug resistance associated with overexpression of the mdr1 gene.

[A phase III study of KRN 8601 (rhG-CSF) on neutropenia induced by chemotherapy for malignant lymphoma--a multi-institutional placebo controlled double-blind comparative study].

Abstract: The clinical usefulness of KRN 8601 (rhG-CSF) was evaluated in patients with neutropenia induced by chemotherapy for non-Hodgkin lymphoma in a double-blind study. The same chemotherapeutic regimens repeated for twice in 3 to 4 weeks interval. During the first cycle of chemotherapy, changes of leukopenia (neutropenia) were observed, and KRN 8601 at a dose of 75 micrograms/body or placebo was started to administer subcutaneously 72 hours after the termination of the second cycle and continued for 14 days. Elevations of nadirs of absolute neutrophil counts (ANC) and significant shorting of neutropenic periods of ANC below 2,000/mm3 were observed with patients given KRN 8601. KRN 8601 is significantly superior over placebo (p less than 0.0001), while overall safety evaluation showed no significant difference between the two groups. All the above results indicate that KRN 8601 is extremely usefull for the neutropenia induced by chemotherapy.

A benzophenazine derivative,N-β-dimethylaminoethyl 9-carboxy-5-hydroxy-10-methoxy-benzo[a]phenazine-6-carboxamide, as a new antitumor agent against multidrug-resistant and sensitive tumors

Abstract: NC-190, a benzophenazine derivative (N-β-dimethylaminoethyl 9-carboxy-5-hydroxy-10-methoxybenzo[a]phenazine-6-carboxamide), was effective against multidrug-resistant human and mouse tumor cells in vitro and in vivo. When vincristine (VCR)-resistant P388 leukemia-bearing mice were treated with an optimal dose of NC-190, four of six mice were cured, whereas treatment of mice with VCR resulted in only a marginal increase in life span. The compound also showed chemotherapeutic effect against Adriamycin-resistant P388 leukemia-bearing mice and was effective against various multidrug-resistant human and murine tumor cells in vitro. Its cytotoxicity to multidrug-resistant K562 cells was not enhanced by the addition of verapamil. The accumulation of NC-190 in multidrug-resistant K562 cells was slightly lower than that observed in sensitive K562 cells; the compound did not efficiently inhibit the binding of VCR to the plasma membrane of resistant cells, indicating that NC-190 has little affinity for P-glycoprotein. NC-190 inhibited the activity of DNA topoisomerase II. These observations suggest that NC-190 (1) is not transported out of resistant cells by P-glycoprotein and (2) inhibits DNA topoisomerase II activity in the cells, resulting in its likely effectiveness against various multidrug-resistant tumor cells.

Functional expression of microsomal and mitochondrial cytochrome P-450 (d and SCC) in COS-7 cells from cloned cDNA.

Abstract: Using full length cDNA introduced into COS-7 cells, two species of P-450 with entirely different physiological functions have been expressed in enzymatically active form. One is P-450d, which is known to reside in the microsomes of rat hepatocytes where it acts as a drug-metabolizing enzyme; the other is P-450(SCC), which catalyzes the conversion of cholesterol to pregnenolone in the rate-limiting reaction of steroidogenesis in mitochondria of adrenal cortex cells. Northern blot and immunoblot analyses revealed that the mRNA and protein of these P-450 species were efficiently produced in COS-7 cells. The protein contents amounted to nearly 0.1% of the total cell protein as estimated from immunoblotting and low temperature CO difference spectra. The subcellular localization of the products indicated that they were correctly sorted to the microsomes and mitochondria, respectively. We have succeeded in eliciting most of the activity of the expressed microsomal P-450d by reconstruction with NADPH-cytochrome P-450 reductase, while the optimal conditions for the mitochondrial enzyme in the COS cells remain to be studied. These results show the applicability of the COS-7 expression system to investigations of the functions of members of the P-450 superfamily whose cDNA has been newly isolated.

Menogaril, an anthracycline compound with a novel mechanism of action: cellular pharmacology.

Abstract: Menogaril, an anthracycline compound possessing a significant antitumor activity after both po and iv administration, has been introduced into clinical trials. However, its mechanism of action has not been clarified yet. This study revealed that its cytotoxicity correlated very well with the inhibition of macromolecular synthesis, indicating the involvement of interaction with DNA. The spectrophotometric study showed a weaker binding of this compound to calf thymus DNA when compared to that of doxorubicin (adriamycin). Despite the lower binding affinity of menogaril to DNA, pronounced DNA cleavage was observed in an intact cell system, indicating that the character of the interaction with DNA is different from intercalation. In contrast to doxorubicin, menogaril is extensively localized in the cytoplasm. The cytoplasmic localization prompted us to study its effect on cytoskeleton proteins. It was found that menogaril inhibited the initial polymerization rate of tubulin, indicating a possible contribution of this process to the overall cytotoxicity of menogaril.

Mechanism of tumor cell killing by HO-221, a novel antitumor compound

Abstract: The mechanism of tumor cell killing by HO-221, a novel benzoylphenylurea derivative that shows broad-spectrum antitumor activities, was studied. HO-221 strongly inhibited the activity of mammalian DNA polymerase α but not that of DNA polymerases β or γ. The inhibition was equivalent to that induced by aphidicolin and ara-CTP, which were selective inhibitors of the enzyme. Furthermore, the inhibition by HO-221 of DNA polymerase α was found to be non-competitive with respect to dCTP as a substrate, unlike that induced by aphidicolin and ara-CTP. The inhibition was reduced the addition of an excess of DNA polymerase α but not by excess amounts of activated DNA as a template primer. These results suggest that HO-221 inhibits the activity of DNA polymerase α by direct interaction with the enzyme in contrast to the impairment of template activity through intercalation into DNA induced by anthracycline compounds. On the other hand, HO-221 showed almost no effect on RNA polymerase activity, the reverse transcriptase activity of avian myeloblastosis virus or protein synthesis in a cell-free system. The flow-cytometry analysis revealed that HO-221 accumulated HL-60 cells in G1-S phases at a low concentration but increased the number of cells in the G1 phase at a higher concentration, stopping cell-cycle progression. The results suggest a correlation between cell-cycle progression and inhibition by HO-221 of DNA polymerase α, which plays a role in DNA replication during the S phase in living cells.

Epidermal growth factor prolongs survival time of tumor-bearing mice.

Abstract: We observed that human epidermal growth factor (hEGF) alone prolonged the survival time of mice bearing various murine syngeneic tumors as well as athymic nude mice bearing human xenografts. No changes in the subcutaneous solid tumor mass volume were observed. Prolongation of survival time by hEGF was observed in mice bearing murine epidermoid carcinoma (BSC) and human gastric carcinoma (KATO III), but not in murine epidermoid carcinoma (KLN205) or human epidermoid carcinoma (A431). Human tumor cells such as A431, KATO III, and murine tumor cells, KLN205, BSC had roughly 2 X 10(6), 3 X 10(4), 1.3 X 10(3) and 1 X 10(3) EGF receptors/cell, respectively. Although KLN205 and BSC tumor cells maintained nearly the same number of EGF receptors, the effects of hEGF were very different. Although A431 tumor cells had nearly 100 times more receptors than KATO III cells, the prolongation of survival time of mice bearing A431 by hEGF was no better than that of mice bearing KATO III. Accordingly, it appears that this prolongation of survival time by hEGF is independent of the number of EGF receptors on tumor cells. In addition, hEGF was shown to inhibit experimental pulmonary metastasis of murine BSC tumor, but was ineffective with murine KLN205 tumor. These results suggest that prolongation of survival time by hEGF may result from the inhibition of tumor cell metastasis and EGF may play a role in preventing the metastasis of certain malignant neoplasms unrelated to its effects through the EGF receptor on tumor cells.

Antitumor activity of T cells in lymphoid organs induced by interferon in tumor-bearing mice.

Abstract: Administration of human hybrid interferon-αA/D (IFN) for 5 consecutive days induced antitumor activity in spleen of Meth A fibrosarcoma-bearing mice 9–10 days after cessation of IFN administration. Antitumor activity assayed by the in vivo neutralization test was found in the spleen of responding mice but not in that of progressive mice. This activity was T-cell-dependent and tumor-selective. However, tumor-neutralizing activity was not found in spleen recovered as early as 3 days after cessation of IFN administration when many tumor cells are still surviving in tumor nodules and being attacked by the host. Instead, T-cell-dependent and tumor-selective tumor-neutralizing activity was found in the lymph node of tumor-bearing mice at this early stage. Furthermore, the tumor-neutralizing activity was already detected in the lymph nodes during the course of IFN administration, although there was no difference in the cell composition of the lymph nodes of IFN- and placebo-administered mice. Since IFN-...

Antitumor Activity of Host T and Non‐T Cells Recovered from Tumor Nodules after Interferon Therapy

Abstract: We examined the modification of host T cells of tumor nodules by interferon (IFN) therapy in mouse models. The host cells were recovered from regressing tumor nodules of mice at Day 13 after intradermal tumor inoculation at Day 0 and administration of 5 x 10(5) U/mouse/day IFN at Day 6 to Day 10. These host cells neutralized in vivo Meth A growth in a dose-dependent fashion. In vitro treatment of these cells with anti-Thy 1.2 monoclonal antibody and rabbit sera as a source of complement abrogated their tumor-neutralizing activity, but only partially, indicating that both T cells and non-T cells were involved in tumor neutralization. The finding that host cells from regressing tumor nodules of either Meth A or Meth 1, an antigenically distinct fibrosarcoma, neutralized both Meth A and Meth 1 tumors without much selectivity was consistent with possible non-T cell involvement. Most of these characteristics of host cells of regressing nodules of IFN-administered mice were also noted with host cells of progressing nodules of placebo-administered mice and there was no significant difference in neutralizing activity qualitatively or quantitatively between the two sources of host cells. There was no significant difference in host T and B cell numbers and compositions of regressing and progressing nodules either. These essentially negative findings raise the possibility, among others, that the primary target host cells to be modified by IFN were not T cells, although the therapeutic effect of IFN was dependent on the host T cells.

Inhibition of lung colonization of mouse colon 26 adenocarcinoma by recombinant mouse interferon β through a modification of platelet function

Abstract: Recombinant murine interferon beta (MuIFN-beta) given i.v. efficiently inhibited both pulmonary arrest and formation of lung colonies of NL-17, a highly metastatic variant of mouse colon adenocarcinoma 26. NL-17 was rather resistant to MuIFN-beta in vitro and was highly resistant to natural killer cells of mice even though they were treated in vivo with MuIFN-beta. Platelets isolated from MuIFN-beta-treated mice showed reduced aggregating activity induced by NL-17. Since lung colonization by NL-17 is influenced by platelet aggregation, the inhibition of colonization by MuIFN-beta could be partly mediated through modification of platelet function in vivo. The effect of MuIFN-beta on platelet function and its subsequent inhibition of lung colony formation give new insights into the action of recombinant MuIFN-beta.