Fractional incorporation of [3H]thymidine and DNA specific activity as assays of inhibition of tumour growth

Effects of ruthenium complexes on experimental tumors: irrelevance of cytotoxicity for metastasis inhibition

A series of 18 ruthenium(III) complexes, structurally related to the selective antimetastatic drug Na[trans-RuCl4(DMSO)Im], and characterized by the presence of sulfoxide and nitrogen-donor ligands were tested on TLX5 lymphoma and some of them on MCa mammary carcinoma to evaluate the dependence of the degree of cytotoxicity and of antimetastatic activity on the chemical properties. In vitro cytotoxicity is present only at high concentrations (> 10(-4) M), depends upon lipophilicity and is markedly affected by the presence of 5% serum or plasma samples in the culture medium. The comparison of the effects on in vitro cytotoxicity with in vivo antitumor and antimetastatic action points out that these compounds reduce metastasis formation by a mechanism unrelated to a direct tumor cell cytotoxicity. If on one hand Na[trans-RuCl4(TMSO)Iq], the compound that shows the most potent in vitro cytotoxic effects, is the least effective against metastases, on the other Na[trans-RuCl4(DMSO)Im], the compound that better reduces metastasis formation, is rather devoid of cytotoxic effects on tumor cells kept in vitro. In particular, Na[trans-RuCl4(DMSO)Im] seems to distinguish between artificially induced metastases and spontaneous metastases and reduces only the former by a cytotoxic mechanism. Out of all the tested compounds, with the exception of Na[trans-RuCl4(DMSO)Ox], Na[trans-RuCl4(DMSO)Im] is confirmed to be the most selective antimetastatic agent of the group.

Antimetastatic action and toxicity on healthy tissues of Na[trans-RuCl4(DMSO)Im] in the mouse

The ruthenium-dimethylsulfoxide complex Na(trans-RuCl4(DMSO)Im] was given i.v. to mice bearing MCa mammary carcinoma and its effects on tumor growth and on healthy host tissues were studied by macroscopic examination of primary tumor growth, by survival time, and by histological analysis using light microscopy and SEM. Either by means of vivo-vivo bioassays or by microscopic examination it appeared that the growth of lung tumors was markedly reduced, whereas the growth of the i.m. primary tumor was much less affected. These effects account for the prolongation of survival time and for the cure rate observed. The favourable effect on survival time was also influenced by the lack of significant cytotoxicity for normal tissues such as lung and kidney epithelia, muscle and liver cells, splenocytes and bone marrow. It thus appears that the selective interaction with tumor cells in the lungs cannot simply be attributed to a selectively higher localization of the compound at this site, nor to a modification of the histological structure of primary tumor. These results highlight the pharmacologic properties of this compound for the control of solid tumor metastases, an effect that was shown to be similarly exerted on advanced tumor metastases.

Effects of endotoxin in mice bearing solid metastasizing tumors and treated with lysozyme hydrochloride

The effects of the i.v. administration of endotoxin (6.25-50 micrograms/mouse on day 13 after tumor implantation) in mice treated orally with lysozyme hydrochloride (100 mg/kg on days 5-12 from tumor implantation) were examined using Lewis lung carcinoma in the C57Bl mouse and MCa mammary carcinoma of CBA mice. On primary tumor growth, endotoxin alone causes a dose-dependent and statistically significant reduction with a nadir on day +2 from endotoxin treatment. Combined with lysozyme, endotoxin causes an effect independent of the dose used, corresponding to the effect caused by endotoxin alone at the dose of 25 micrograms/mouse. No tumor regression was recorded in any of the treated groups. Endotoxin is virtually devoid of effects at the metastatic level. In the same conditions, lysozyme causes a reduction of primary tumor growth and a more pronounced inhibition of lung metastasis formation as expected from its already reported effects. The antitumor activity of endotoxin, unlike lysozyme, can be ascribed to tumor hemorrhagic necrosis due to tumor necrosis factor (TNF) production, as determined in tumor homogenates. Endotoxin does not increase the antitumor effects in mice treated with lysozyme, as expected from the data obtained with the more immunogenic SA1 sarcoma, although lysozyme increased the mitogenic response to ConA of ex vivo isolated splenocytes, in vitro cultured in the presence of IL-2.

Antineoplastic activity and toxicity of an organometallic complex of ruthenium(II) in comparison with cis-PDD in mice bearing solid malignant neoplasms

The antineoplastic activity of an organometallic complex of ruthenium(II), [cis-RuCl2(DMSO)4]o, has been examined in comparison with that of cis-PDD, using three metastasizing tumors of the mouse: Lewis lung carcinoma, B16 melanoma and MCa mammary carcinoma. [cis-RuCl2(DMSO)4]o significantly reduces primary tumor growth in all the tumors tested, and its activity is similarly pronounced at three different dosages in mice bearing Lewis lung carcinoma. On the contrary, the survival time of animals having i.v. or i.m. tumor implants are only moderately increased, and also in the case of combined treatments with surgery. The antineoplastic activity of cis-PDD appears to be less pronounced than that of [cis-RuCl2(DMSO)4]o, and is limited to mice bearing B16 melanoma, which, among the three tumors used, appears to be naturally more responsive to cis-PDD and [cis-RuCl2(DMSO)4]o. The use of [cis-RuCl2(DMSO)4]o appears advantageous over that of cis-PDD since, unlike cis-PDD, its antineoplastic effects have been obtained at dosages with reduced host toxicity, indicated by the absence of significant hematological toxicity and toxicity for normal proliferating tissues.

Assessment of antimetabolite cytotoxicity: a comparison of clonogenic assays and tritiated deoxyuridine incorporation

A comparison has been made between the cloning capacity and changes in tritiated deoxyuridine (6-[3H]-UdR) incorporation of L1210 (murine leukaemia) and PMC-22 (human melanoma) cells treated with methotrexate (MTX), 5-fluorouracil (5-FU) and cytosine arabinoside (ARA-C). The labelling-cloning relationship was poor, with brief drug exposure times, but improved progressively after drug treatment of 1 cell-cycle time's duration. Labelling changes resulting from short-term exposure to drug (several hours) provided poor predictions of the cytotoxicity resulting from longer drug exposure.

Effects of cancer chemotherapeutic agents on testicular DNA synthesis in the rat. Evaluation of a short-term test for studies of the genetic toxicity of chemicals and drugs in vivo

Changes in the rate of testicular DNA synthesis in the rat were studied at various times after single doses of 12 cancer chemotherapeutic agents. The animals were given intravenous injections of [14C]thymidine and [3H]thymidine 24 and 3 h, resp., before they were killed. By combining measurements of the free serum radioactivity and the testicular incorporation of the differentially labelled precursor, different response patterns were obtained for agents with different modes of action. The DNA-damaging agents cyclophosphamide, chlorambucil, thio-TEPA, busulphan, CCNU and procarbacine, after some delay, caused a decrease of testicular thymidine incorporation and a corresponding increase of free serum radioactivity. The non-DNA-damaging agents 5-fluorouracil, methotrexate, hydroxyurea and cytosine arabinoside had a rapid effect on testicular thymidine incorporation and produced diverse response patterns different from that of the DNA-damaging agents. Actinomycin D and also vinblastine caused changes in testicular thymidine incorporation and showed response patterns different from those of the other agents. These results show that simple measurements of testicular DNA synthesis may provide useful information for the evaluation of genotoxic effects of chemical compounds and may help one to distinguish between DNA-damaging agents and metabolic inhibitors of DNA synthesis.

Effects of intestinally absorbed thymidine on tritiated thymidine utilization

Experimental evidence presented suggests that [3H]TdR can be rapidly and efficiently transported from the intestine to the systemic circulation. This pathway for thymidine transport may be physiologically important since administration of cold thymidine in the drinking water enhances the utilization of a parenterally injected dose of [3H]TdR in several body tissues of the mouse.

Evaluation of single-agent therapy in human colorectal tumour xenografts

The response of 6 human colorectal tumour xenografts to 7 cytotoxic agents have been established. Tumour responses have been quantified by growth inhibition, and the time taken for 3H-thymidine fractional incorporation (TFI) to recover to the control value after treatment. The chemosensitivity of each tumour line to a spectrum of agents was individual, and no pattern of response which would allow prediction of individual agent efficacy was apparent. Cyclophosphamide, methyl-CCNU and 5-fluorouracil produced marked growth inhibition in individual tumour lines, whereas actinomycin-D, cis-dichlorodiammine platinum, doxorubicin and pentamethylmelamine showed little activity. Data presented agree with clinical evaluation for single-agent therapy. The uptake and incorporation of radiolabelled 5-fluorouracil into 4 tumour lines is reported. No marked differences between 3 FU-insensitive lines and 1 sensitive line have been observed.