Cytotoxicity and sister chromatid exchanges induced in vitro by six anticancer drugs developed in the People's Republic of China

Growth inhibition in the Chinese hamster cell line V79 and in the human lymphoid cell line Raji and induction of sister chromatid exchange(s) (SCE) in V79 cells after treatment with six anticancer drugs [harringtonine (HRT), homoharringtonine (HHRT), camptothecin (CPT), hydroxycamptothecin (HCPT), lycobetaine (LBT), and oxalysine (OXL)] developed in the People's Republic of China were studied. OXL is a new antibiotic; all other drugs are plant extracts. All drugs caused a dose-dependent growth inhibition in both cell types, as evidenced by decreases in plating efficiencies of V79 cells and in viable cell counts of Raji. However, the degree of inhibition differed widely among the drugs. HRT, HHRT, CPT, and HCPT were the most potent growth inhibitors, LBT was next, and OXL was the least effective inhibitor. SCE analyses were made in V79 cells treated with a drug in the presence or absence of the metabolic activation system S9 mixture (S9 mix), except for the HRT assay in which the S9 mix was not used. CPT, HCPT, and LBT induced a dose-dependent increase in SCE frequencies, while HRT, HHRT, and OXL caused no SCE induction at any dose level used. CPT was the most powerful SCE inducer. HCPT induced SCE but at a much reduced rate when compared to that of CPT. LBT was a weak SCE inducer; SCE induction was seen only in cultures treated with 40 micrograms or more LBT/ml. Addition of the S9 mix did not alter SCE frequencies, indicating that the drugs were direct-acting agents. HRT and HHRT were highly toxic, but they induced no increases in SCE frequency, indicating that cytotoxicity of a compound does not necessarily correlate with SCE induction.

[Pharmacology of lycorine. 1) Effect on biliary secretion in the rat]

The Authors study pharmacological actions of lycorine, alkaloid of Lycoris radiata. On the basis that anti-inflammatory substances have a choleretic effect, the activity of lycorine on biliary secretion of rats has been investigated. Lycorine, at a dose of 1 mg/kg induces, in rats anaesthetized with urethane (1,2 g/kg i.m.), a marked choleretic effect. This experiment do not define the mechanism responsible for the observed choleresis.

Peptidyltransferase center of ribosomes. On the mechanism of action of alkaloid lycorine

The molecular mechanism of action of the alkaloid lycorine has been revised. According to our results, lycorine inhibits the binding of CACCA-Leu comes from Ac to the donor site of the peptidyltransferase center of wheat-germ ribosomes, whereas the transpeptidation reaction in the system with the minimal model donor is not inhibited. The equilibrium constant of CACCA-Leu comes from Ac to the donor site of 80 S ribosomes is measured.

Therapeutic activity of pretazettine, standard drugs, and the combinations on intraperitoneally implanted Lewis lung carcinoma in mice

Therapeutic effectiveness of pretazettine (PTZ) has been demonstrated in the intraperitoneally (i.p.) implanted Lewis lung carcinoma (LLC) in both syngeneic and allogeneic mice. The i.p. implanted LLC has been found to be sensitive to most standard drugs tested such as cyclophosphamide (CY), actinomycin D, 5-fluorouracil, methotrexate, 6-thioguanine and vincristine, in comparison to the subcutaneously (s.c.) or intravenously (i.v.) implanted LLC which was reported to be resistant to most standard drugs (s.c.-LLC) or resistant to actinomycin D, methotrexate and vincristine (i.v.-LLC). The effectiveness of PTZ was comparable to that of standard drugs in the i.p. implanted LLC system, and the combination therapy of PTZ with these standard drugs except vincristine was synergistically or additively effective. Also, the PTZ combination rescued the allogeneic mice from the risk of adverse (tumor-enhancing) effects of CY at moderate doses (25-50 mg/kg) given therapeutically.

Effect of narciclasine and puromycin on the synthesis of rapidly labelled RNA in excised salivary glands of Chironomus thummi

The effect on transcription of two protein synthesis inhibitors, narciclasine and puromycin, when applied in short periods of time to explanted salivary glands of Chironomus thummi, has been studied. Narciclasine (6 muM) enhances the uptake of uridine and stimulates the synthesis of giant-heterogeneous, pre-ribosomal (38 S) and low-molecular weight (4-5 S) RNA. However, puromycin (200 muM) inhibits uridine uptake and decrease selectively the synthesis of pre-rRNA, while transcription of low-molecular weight RNA is stimulated. These effects are compared with those previously found to be produced by other inhibitors of translation in this biological system.

Therapeutic activity of pretazettine on Ehrlich ascites carcinoma: adjuvant effect on standard drugs in ABC regimen

A narcissus alkaloid, pretazettine hydrochloride (PTZ), has been shown to be active against Ehrlich ascites carcinoma. The Ehrlich cells are more sensitive to PTZ in DBA/2 mice than in Swiss mice. The therapeutic activity of the individual standard drugs in ABC (adriamycin, BCNU, and cyclophosphamide) regimen against Ehrlich ascites carcinoma has been increased remarkably by the adjuvant therapy of PTZ following the preliminary use of standard drugs. The independent inhibitory action of PTZ on cellular protein synthesis in the presence of the DNA-binding agent has been demonstrated in KB-cell cultures. Adriamycin-pretreated KB cells are found to be more sensitive to PTZ than nontreated cells.

The influence of several anticancer agents on cell proliferation, differentiation and the cell cycle of murine erythroleukemia cells

The influence of homoharringtonine, hydroxycamptothecin and lycobetaine on the cell cycle progression of murine erythroleukemia cells was studied by using flow microfluorometry (FMF) technique and centrifugal elutriation to obtain specific fractions of the cell cycle. FMF histogram analysis showed that homoharringtonine could strongly arrest cells in the G1 phase of the immediate cell cycle. This effect was more pronounced and persisted longer with G1 cells than with S or G2 cells. Hydroxycamptothecin mainly delayed the progression of S cells of the subsequent cell cycle (daughter cells). Lycobetaine caused a marked accumulation of G2 cells. These 3 compounds possess a relatively specific action on cell progression through the cell cycle. Homoharringtonine and hydroxycamptothecin can inhibit the cell proliferation of murine erythroleukemia cells (MELC) at low concentrations (ng/ml) whereas lycobetaine, cantharidin and oxalysine are less potent. Among them only hydroxycamptothecin had a weak activity to induce MELC differentiation. These results may provide some basic knowledge for designing new protocols of the combination treatment of neoplastic diseases.

Pharmacological studies of lycorenine, an alkaloid of Lycoris radiata Herb.: II. Effects of blood pressure in rats and dogs and the mechanism of tachyphylaxis to the vasodepressor action of lycorenine in rats

Blood pressure responses to lycorenine were investigated in rats and dogs. Lycorenine (10--40 mg/kg p.o.) produced a decrease in blood pressure in conscious rats which was greater in hypertensive rats than in normotensive rats. In conscious dogs, lycorenine (5 or 10 mg/kg i.v.) produced rises in blood pressure and heart rate except for a few instances, while it produced a decrease in blood pressure in pentobarbital anesthetized dogs. Thus, there are species differences in cardiovascular effects of lycorenine between conscious rats and dogs. The development of tachyphylaxis to the vasodepressor actions of lycorenine and its related compounds was related to their alpha-adrenergic blocking activities at the time of the second injection in anesthetized rats. Desipramine which abolished or diminished the development of tachyphylaxis to the vasodepressor action of lycorenine (5 or 7.5 mg/kg i.v.), shortened the duration of its vasodepressor action and reduced its alpha-adrenergic blocking action. These results indicate that the development of tachyphylaxis to the vasodepressor action of lycorenine is ascribed to maintenance of its alpha-adrenergic blocking action.

Therapeutic activity of pretazettine on Rauscher leukemia: comparison with the related Amaryllidaceae alkaloids

Comparative studies on the cytotoxicity and antileukemic activity of limited numbers of Amaryllidaceae alkaloids with pretazettine, a narcissus alkaloid, have been performed on the systems of Rauscher virus-carrier cells and the leukemic mice. Only precriwelline, a stereochemical epimer of pretazettine, has been found to be therapeutically active as that of pretazettine. The natural precursors such as haemanthamine, crinamine and 6-hydroxycrinamide were also moderately active, but the artificial final product, tazettine, was confirmed to be inert. The structure-activity relationship of pretazettine or precriwelline has been partially analyzed. Also, the predominancy of antiviral activity relative to cytotoxicity of the alkaloids has been demonstrated when compared with some standard antileukemic drugs.

Pharmacological studies of lycorenine, an alkaloid of Lycoris radiata Herb.: Vasodepressor mechanism in rats

Vasodepressor mechanism of lycorenine (an alkaloid of Lycoris radiata Herb.) was investigated in anesthetized rats. Lycorenine (1--10 mg/kg i.v.) produced dose-related decreases in blood pressure and heart rate and tachyphylaxis developed with repeated injections. In the blood-perfused rat hindquarters, lycorenine (62.5--500 micrograms i.a.) produced dose-related decreases both in mean blood pressure and in perfusion pressure, and the lycorenine-induced decrease in perfusion pressure was abolished by phenoxybenzamine or hexamethonium. Lycorenine (more than 1 mg/kg i.v.) blocked the pressor response to sympathetic nerve stimulation, but failed to block the tachycardia induced by sympathetic nerve stimulation. Lycorenine (7.5 or 15 mg/kg i.v.) reduced the spontaneous splanchnic nerve activity. Lycorenine when given intracerebroventricularly produced decreases in blood pressure and heart rate only in large doses (over 500 micrograms). The maximal bradycardia induced by lycorenine was abolished by bilateral vagotomy. It is suggested that lycorenine may produce a decrease in blood pressure as the result of alpha-adrenergic blockade in conjunction with the reduction of the spontaneous sympathetic nerve activity, and produce bradycardia by modifying vagal activity.

Binding of [3H]narciclasine to eukaryotic ribosomes. A study on a structure-activity relationship

[3H]Narciclasine is a specific inhibitor of peptide bond formation on eukaryotic ribosomes and binds to 60-S ribosomal subunits. Binding of [3H]-narciclasine to yeast ribosomes is inhibited by many other inhibitors of peptide bond formation including anisomycin, several sequiterpene antibiotics (trichodermin, trichothecin, fusarenon X and verrucarin A) several Cephalotaxus alkaloids (harringtonine, homoharringtonine and isoharringtonine), several Amaryllidaceae alkaloids (pretazettine, haemanthamine, lycorine, pseudolycorine and dihydrolycorine) and the narciclasine derivatives trans-dihydronarciclasine, trans-dihydronarciclasine acetonide and isonarciclasine. Binding is also inhibited, although to a very small extent, by methylnarciclasine and cisdihydronarciclasine. In contrast, no inhibition of [3H]narciclasine binding was observed in the presence of certain other inhibitors of peptide bond formation including blasticidin S, gougerotin, sparsomycin and puromycin.

Antileukemic activity of ungeremine and related compounds. Preparation of analogues of ungeremine by a practical photochemical reaction

A number of alkoxypyrrolophenanthridinium salts and their analogues related to the antileukemic alkaloid ungeremine were prepared by a practical photochemical cyclization. The importance of the quaternary nitrogen atom and of alkoxy groups, the planarity of a molecule, and steric considerations relative to antileukemic activity are discussed.

Therapeutic activity of pretazettine, a narcissus alkaloid on Rauscher leukemia: comparison with tazettine and streptonigrin

The therapeutic activity of narcissus alkaloid pretazettine HC1 (PTZ) on established Rauscher leukemia has been demonstrated and compared with the isomer tazettine (TZ) and an antibiotic, streptonigrin (SN). PTZ and SN showed remarkable prolongation effect on the life span of the leukemic mice and the antiviral activity has been confirmed in mouse 3T3 cells infected with Rauscher virus. TZ showed no significant activity in the leukemic mice and was inhibitory to the virus growth in the cells at much higher doses than PTZ. It is suggested that the stereochemical rearrangement from PTZ to TZ inactivates the biological activity of PTZ.