Biomedical subjects

Ross O Meyers

Publications and source records attributed to Ross O Meyers.

4 recordsLinked to original sources

PubMed2006

Cytotoxic activity of Apomine is due to a novel membrane-mediated cytolytic mechanism independent of apoptosis in the A375 human melanoma cell line.

Apomine, a novel bisphosphonate ester, has demonstrated anticancer activity in a variety of cancer cell lines; however, its mechanism of cytotoxicity is not well understood. Previous work has demonstrated that Apomine induces cell death by activation of caspase-3 in several cancer cell types. However, we have demonstrated that Apomine induces cell death in the A375 human melanoma cell line through a novel membrane-mediated mechanism that is independent of caspase-3 activation. This mechanism of membrane lysis may apply to other bisphosphonates and may be an important mechanism for overcoming resistance to apoptosis. Interestingly, Apomine-mediated cell death in the A375 and UACC 3093 human melanoma cell lines is also independent of N-Ras farnesylation, which was a previously described mechanism of action for Apomine in other cancer cell types. These data suggest that Apomine induces cell death through a novel plasma membrane-mediated cytolytic pathway, independent of caspase-3 activation and N-Ras farnesylation.

Antineoplastic Agents↗

PubMed2006

Preclinical antitumor activity, pharmacokinetics and pharmacodynamics of imexon in mice.

Imexon, a novel pro-oxidant, thiol-binding agent, is currently in phase I/II clinical trials in patients with advanced solid tumors. The aim of this study was to characterize the preclinical pharmacology of imexon in vivo. We investigated the anticancer activity of imexon in several cancer cell lines grown as xenografts in severe combined immunodeficient mice. Imexon was active against both hematologic and solid tumor types. The maximally tolerated dose, at the selected dosing schedule, was 150 mg/kg. Using the maximally tolerated dose of imexon, we sought to identify a potential pharmacodynamic biomarker to monitor the mechanistic effect systemically. As imexon binds cellular thiols in vitro, thiol depletion by imexon in vivo was evaluated as a potential biomarker. Following a single 150 mg/kg dose of imexon by intraperitoneal injection, glutathione levels decreased by 40% at 3 h in mouse erythrocytes. In mouse plasma, imexon treatment led to a significant decrease in cystine levels 2-4 h after drug administration. Notably, by this time, free imexon plasma levels were nondetectable. By investigating the pharmacokinetics of imexon, we also found that imexon undergoes rapid clearance from plasma in a dose-independent fashion with a half-life of 12-15 min. In summary, imexon is active against several cancer types in vivo. Imexon also decreases circulating thiols and exhibits dose-independent pharmacokinetics in mice. Plasma cystine levels may represent a biomarker of imexon activity in vivo.

Animals↗

PubMed2005

Cytotoxic lignans from Larrea tridentata.

Six lignans, including the cyclolignan 3,4'-dihydroxy-3',4'-dimethoxy-6,7'-cyclolignan, were isolated from the flowering tops of Larrea tridentata. Additionally the flavanone, (S)-4',5-dihydroxy-7-methoxyflavanone, was isolated for the first time from L. tridentata or any member of the family Zygophyllaceae. All of the compounds were assessed for their growth inhibitory activity against human breast cancer, human colon cancer and human melanoma cell lines. The lignans had IC50 values of 5-60 microM with the linear butane-type lignans being the most potent, and it was found that colon cancer cells were the least sensitive cell type tested. The relative potency of linear butane type lignans against human breast cancer appears to correlate positively with the number of O-methyl groups present on the molecule.

Antineoplastic Agents, Phytogenic↗

PubMed2002

Nordihydroguaiaretic acid: hepatotoxicity and detoxification in the mouse.

Larrea tridentata (Moc & Sess) Cov. (Zygophyllaceae) is an ethnobotanically important plant found in the American Southwest and northern Mexico. Although numerous beneficial effects have been attributed to this plant, several case reports have demonstrated high doses of Larrea-containing herbals induce hepatotoxicity and nephrotoxicity in humans. Nordihydriguaiaretic acid (NDGA) is a lignan found in high amounts (up to 10% by dry weight) in the leaves and twigs of L. tridentata. Previously, NDGA has been shown to induce cystic nephropathy in the rat, however, no reports have been made concerning this compound's hepatotoxic potential. Here, we report that intraperitoneal administration of NDGA is lethal in the mouse (LD(50)=75 mg/kg). Administration is associated with a time and dose-dependent increase in serum alanine aminotransferase levels, which suggest liver damage. Indeed, freshly isolated mouse hepatocytes are more sensitive to NDGA than human melanoma cells. Furthermore, we have identified glucuronidation as a potential detoxification mechanism for NDGA. Both mono and diglucuronide conjugates of NDGA are formed after intravenous dosing. The monoglucuronide is also formed after incubation of NDGA with human hepatic microsomes; suggesting that glucuronide conjugation is important in the metabolism of NDGA by humans. In summary, this report indicates that NDGA may contribute to the hepatotoxicity of L. tridentata and provides preliminary information on NDGA metabolism.

Alanine Transaminase↗