Effects of modulation of basic fibroblast growth factor on tumor growth in vivo.

BACKGROUND: Recombinant human basic fibroblast growth factor (rHu-bFGF) is known to stimulate proliferation in some tumor cells and to modulate tumor vascularization. PURPOSE: The purpose of this study was to examine the possible role of this agent in the development of tumors. The study was designed to determine the effects of modulating bFGF activity in vivo in tumor models from cell lines with different responses to bFGF and with different content and receptor levels of bFGF. METHODS: Two tumor cell lines (human DLD-2 colon carcinoma and rat C6 glioma) were characterized for bFGF content and bFGF receptor levels by Western blot analysis in cultured cells and by studies of [125I]rHu-bFGF binding to sections from xenografts grown in nude mice. Tumor cell proliferation was monitored after treatment with rHu-bFGF or the DG2 or DE6 IgG monoclonal antibody to rHu-bFGF in culture and in vivo. RESULTS: C6 cells exhibited 7800 high-affinity receptors for rHu-bFGF per cell (dissociation constant [Kd] = 46 pM), while DLD-2 cells lacked high-affinity receptors. rHu-bFGF stimulated [3H]thymidine uptake by C6 cells, but the addition of DG2 IgG prevented this stimulation; rHu-bFGF had no effect on [3H]thymidine incorporation by DLD-2 cells. C6 cells had higher levels of immunoreactive bFGF than did DLD-2 cells. The xenografts from both cell lines exhibited high-affinity [125I]rHu-bFGF binding that was concentrated on vascular-like structures. rHu-bFGF at a dosage of 0.25 mg/kg given intraperitoneally daily for 18 days caused a twofold increase in DLD-2 tumor weight but had little effect on the growth of C6 xenografts. In contrast, daily intravenous injections of DG2 IgG given to mice had no effect on DLD-2 tumor growth but reduced growth of C6 tumors by approximately 30%--a statistically significant difference. CONCLUSIONS: The addition of exogenous rHu-bFGF or of a neutralizing antibody resulted in significant alterations in tumor growth in vivo, which were specific for tumor type and bFGF characteristics. While some of these effects may be mediated by the bFGF-responsive endothelial cells of the tumor vasculature (DLD-2 colon carcinoma), others may result from inhibition of bFGF-dependent tumor cell proliferation (C6 glioma). IMPLICATIONS: Studies that measure tumor blood flow are necessary to confirm that these effects are mediated by changes in tumor vasculature.

Synthesis and biological evaluation of 2-styrylquinazolin-4(3H)-ones, a new class of antimitotic anticancer agents which inhibit tubulin polymerization.

A novel series of 2-styrylquinazolin-4(3H-ones which inhibited tubulin polymerization and the growth of L1210 murine leukemia cells was discovered. Extensive structure-activity relationship studies suggest that the entire quinazolinone structure was required, but activity was further enhanced by halide or small hydrophobic substituents at position 6. These analogues did not substantially interfere with the binding of radiolabeled colchicine, vinblastine, or GTP to tubulin and weakly stimulated GTP hydrolysis uncoupled from polymerization. Several analogues have shown in vivo tumor growth inhibitory activity in the L1210 leukemia model, with the lead compound 5o exhibiting good antitumor activity against murine solid tumors as well as human tumor xenografts.

Effects of plasma protein binding displacement on the pharmacokinetics, tissue and tumor concentrations and efficacy of brequinar, a highly protein-bound antitumor agent.

Brequinar is a developmental antitumor agent which is highly bound to plasma proteins. The effects of plasma protein binding displacement on brequinar pharmacokinetics, tissue distribution, tumor distribution and antitumor efficacy were evaluated. Sodium salicylate and ibuprofen increased the percentage of free brequinar in serum in vitro, in proportion to their added concentrations. Sodium salicylate also altered the pharmacokinetics of i.v. brequinar in rats when adminstered i.v. or p.o. at 10- or 50-fold higher doses than brequinar. At the highest salicylate/brequinar dose ratio, significant increases were observed for terminal half-life, mean residence times in the body and tissues, systemic clearance, distribution clearance, the volume of the central compartment and volume of distribution at steady state. Neither salicylate nor ibuprofen increased brequinar concentrations in lung and muscle specimens from rats, 4 or 24 hr after dosing. Tumor, lung and muscle brequinar concentrations in mice were also unaffected by coadministered sodium salicylate, 4 or 24 hr after a single i.v. brequinar dose. In rats infused for 48 hr with brequinar or brequinar plus salicylate, salicylate increased the percentage of free brequinar in plasma and lungs, but total brequinar concentrations were reduced. Antitumor efficacy was evaluated by measuring the survival times of mice implanted with L1210 leukemia cells. Salicylate-treated mice had a similar brequinar dose/response profile as mice not coadministered salicylate. Ibuprofen also did not increase brequinar's antitumor potency.

Cytotoxicity of synthetic racemic ptilocaulin: a novel cyclic guanidine.

(+)-Ptilocaulin, a novel cyclic guanidine extracted from the Caribbean sponge Ptilocaulis aff. P. Spiculifer, is reported to have broad spectrum antimicrobial activity in vitro as well as in vitro activity against L1210 murine leukemia. To more fully evaluate this compound as an anticancer agent, the in vitro cell growth inhibitory potencies of synthetic racemic ptilocaulin and ten clinical anticancer drugs were determined and compared in 16 different normal and transformed human and murine cell populations. Potency, expressed as the 50% inhibitory concentration (IC50), was determined by a tetrazolium reduction (MTT) assay. Ptilocaulin showed a fairly broad spectrum of in vitro activity against colon and mammary adenocarcinomas, melanomas, leukemias, transformed fibroblasts and normal lymphoid cells (IC50s 0.05- greater than 10 micrograms/ml). This activity was comparable to that of many of the clinical drugs, including vinca alkyloids, antibiotics, alkylators and antimetabolites. Cell viability was affected only after a 72 hr exposure to the compound. In a clonogenic assay, cytocidal effects were observed after 24-72 hr exposures to 10 x IC50 concentrations of ptilocaulin, as evidenced by failure of cells to resume growth after removal of the compound. Cytostatic effects were observed at less than or equal to IC50 concentrations, as evidenced by resumption of growth to near-control levels after removal of the compound. Ptilocaulin was toxic at 50 and 25 mg/kg in an in vivo L1210 tumor model and was ineffective at lower concentrations (T/Cs 100-112%). In vivo studies in a more sensitive tumor system are recommended but are limited by the lack of availability of sufficient quantities of the compound.

Activity of a novel 4-quinolinecarboxylic acid, NSC 368390 [6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinolinecarb oxylic acid sodium salt], against experimental tumors.

A novel, substituted 4-quinolinecarboxylic acid (NSC 339768) demonstrated antitumor activity against L1210 leukemia and B16 melanoma in the National Cancer Institute's Developmental Therapeutics Program. An extensive analogue synthesis program was initiated; over 200 derivatives were synthesized and tested for anticancer activity. One of these compounds, 6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinolinecarboxylic acid sodium salt, NSC 368390 (DuP-785), was selected for further investigation because of its efficacy against a spectrum of human solid tumors and its water solubility. In initial studies with L1210 leukemia, the compound caused an increase in life span of greater than 80%. The activity was schedule dependent, and the compound was equally efficacious when administered i.p., i.v., s.c., or p.o. In tests against human tumors xenografted under the renal capsule of nude mice, NSC 368390 when injected i.p. in doses of 20-40 mg/kg daily for 9 days inhibited the growth of the MX-1 breast, LX-1 lung, BL/STX-1 stomach, and CX-1 colon carcinomas by greater than 90%. NSC 368390 also inhibited the growth of three distinct human colon carcinomas, the HCT-15, clone A, and DLD-2 tumors, growing s.c. in nude mice. An i.p. dose of 25 mg/kg given daily for 9 days inhibited the growth of the DLD-2 colon cancer by 98%. 1-beta-D-Arabinofuranosylcytosine and Adriamycin were ineffective, and fluorouracil was only moderately effective against these colon tumors. Because of its good activity against human colon tumors and other human carcinomas and its water solubility, NSC 368390 (DuP-785) is being developed as a Phase 1 anticancer agent.