Cancer induction in the DMBA hamster cheek pouch: a modified technique using a promoter.

OBJECTIVE: To evaluate a modified method of carcinogenesis induction using the 9,10-dimethyl-1,2-benzanthracene (DMBA) sustained-release suture technique followed by arecaidine promotion in the hamster cheek pouch model. STUDY DESIGN: Prospective, controlled animal study. METHODS: Number 3-0 cotton sutures were impregnated with DMBA and coated with silicone elastomer. These sutures were placed in the cheek pouch of Syrian hamsters in the submucosal space to a length of approximately 1.5 cm. The suture placement was confirmed every 2 weeks and replaced if lost. After 12 weeks, the DMBA-coated sutures were removed. The cheek pouches were everted and painted with a solution of arecaidine three times weekly for up to an additional 4 weeks or until the tumor reached a size of 100 mm2. RESULTS: We placed sutures in 165 Syrian hamster cheek pouches. Of these, 133 hamsters (80.6%) produced squamous cell carcinomas that reached a size of 100 mm2 and then were randomly selected for treatment in a new drug trial. Twenty-six hamsters (15.8%) were found dead and 6 (3.6%) were killed because of severe inflammation. CONCLUSIONS: The DMBA hamster cheek pouch model is a reliable and efficient animal model for inducing squamous cell carcinoma and can be used to study upper aerodigestive tract tumors.

Rationale for intralesional valrubicin in chemoradiation of squamous cell carcinoma of the head and neck.

OBJECTIVES/HYPOTHESIS: With some advanced squamous cell carcinomas (SCCs) of the head and neck, chemoradiation therapy may obviate the need for surgical intervention. However, both modalities are known to produce organ toxicities, and tumor insensitivity remains problematic. Thus there is a clear need for the development of new treatment strategies. Accordingly, preclinical studies to evaluate the use of valrubicin, a contact-safe, mechanistically novel antitumor agent, combined with low-dose radiation for the therapy of SCC have been conducted. METHODS: The comparative in vitro antitumor activities of valrubicin with or without irradiation versus cisplatin were evaluated using human-derived sensitive and cisplatin-resistant SCC cell lines. A hamster cheek pouch model of SCC was used to assess the efficacy of weekly intratumoral valrubicin injections with and without concurrent low-dose irradiation. RESULTS: Valrubicin cytotoxicity was found to be comparable in both sensitive and platinum-resistant cell lines and superior to cisplatin. The addition of minimally cytotoxic cell irradiation (300-450 cGy) resulted in prolonged G2/M cell cycle arrest and a supraadditive increase in apoptotic cell death. In hamsters, once a week x 3 intratumoral drug injections (3, 6, or 9 mg) were growth inhibitory; however, when valrubicin (6 mg) was combined with minimally cytotoxic irradiation (150, 250, or 350 cGy) significant tumor shrinkage was observed. CONCLUSIONS: Valrubicin produces supra-additive effects against SCC when combined with low-dose irradiation. This effect appears to correlate with the ability of valrubicin, a cytoplasmic-localizing drug, to inhibit protein kinase C. Therapeutic use of valrubicin against SCC could provide for reduced radiation doses with consequent improved efficacy and reduction in host toxicity.

Effect of aliphatic side-chain substituents on the antimalarial activity and on the metabolism of primaquine studied using mitochondria and microsome preparations.

The substitution of two deuterium atoms on the alpha-carbon of the primaquine side chain was found to produce a sevenfold decrease in the rate of conversion of primaquine to carboxyprimaquine by enzymatic oxidative deamination, but the deuterium substitution was found to have no significant effect on the in vitro antimalarial activity or on in vitro hepatocyte toxicity. Placing a single methyl group on the alpha-carbon was found to produce only a slight decrease in the rate of oxidative deamination. Although metabolic attack occurred adjacent to either the aniline nitrogen or the aliphatic amine, metabolic attack occurred primarily adjacent to the more basic nitrogen at the 1'-position, even when this position bore a methyl substituent. Primaquine, the alpha-dideutero analogue, and the alpha-methyl analogue were all found to have about the same in vitro antimalarial activity as determined in the liver hepatocyte assay.

Thermospray mass spectroscopy/high performance liquid chromatographic identification of the metabolites formed from arteether using a rat liver microsome preparation.

Thermospray LC/MS methods with internal standardization were developed for the quantification of the antimalarial arteether and six of its metabolites at the 1-10 micrograms/ml level in liver microsome preparations without the use of solvent extraction. The thermospray mass spectra of arteether and most of its metabolites exhibited strong [M + NH4]+ and [M - OR]+ peaks arising from the molecular ion adduct and the loss of the alkoxy or hydroxy group of the side chain. In addition to the six metabolites for which authentic reference standards were available, three additional metabolites were detected. The major metabolites of arteether were found to be dihydroartemisinin, deoxydihydroartemisinin, 3-hydroxydeoxydihydroartemisinin, two isomers of hydroxyarteether, and 3-hydroxydeoxyarteether. Deoxyartheether was not found at significant concentrations in the microsome preparation.