Antioxidant defense mechanisms of human mesothelioma and lung adenocarcinoma cells

Abstract

The development of drug resistance of tumors is multifactorial and still poorly understood. Some cytotoxic drugs generate free radicals, and, therefore, antioxidant enzymes may contribute to drug resistance. We investigated the levels of manganese superoxide dismutase (Mn SOD), its inducibility, and its protective role against tumor necrosis factor-alpha and cytotoxic drugs (cisplatin, epirubicin, methotrexate, and vindesin) in human pleural mesothelioma (M14K) and pulmonary adenocarcinoma (A549) cells. We also studied other major antioxidant mechanisms in relation to oxidant and drug resistance of these cells. A549 cells were more resistant than M14K cells toward both oxidants (hydrogen peroxide and menadione) and all the cytotoxic drugs tested. M14K cells contained higher basal Mn SOD activity than A549 cells (28.3 +/- 3.4 vs. 1.8 +/- 0.3 U/mg protein), and Mn SOD activity was significantly induced by tumor necrosis factor-alpha only in A549 cells (+524%), but the induction did not offer any protection during subsequent oxidant or drug exposure. Mn SOD was not induced significantly in either of these cell lines by any of the cytotoxic drugs (0.007-2 microM, 48 h) tested when assessed by Northern blotting, Western blotting, or specific activity. A549 cells contained higher catalase activity than M14K cells (7.6 +/- 1.3 vs. 3.6 +/- 0.5 nmol O(2). min(-1). mg protein(-1)). They also contained twofold higher levels of glutathione and higher immunoreactivity of the heavy subunit of gamma-glutamylcysteine synthetase than M14K cells. Experiments with inhibitors of gamma-glutamylcysteine synthetase and catalase supported our conclusion that mechanisms associated with glutathione contribute to the drug resistance of these cells.

Bone Marrow Chemoprotection without Compromise of Chemotherapy Efficacy in a Rat Brain Tumor Model

“…Brain tumor chemotherapy may be improved by reducing the systemic toxicities of chemotherapy, to reduce the incidence of severe side effects and dose reduction, or even allow dose escalation. Chemoprotection can be provided by exogenous sulfur-containing chemoprotective agents (thio, thiol, and thioether compounds), which act to detoxify agents through antioxidant and free radical scavenging activity (Cotgreave, 1997;Jarvinen et al, 2000), and other mechanisms (Gamcsik et al, 1997;Links and Lewis, 1999).…”

A new approach to the toxicity testing of carbon-based nanomaterials—The clonogenic assay

“…Transformed cell lines such as A549 cells are frequently referred to as being more resistant to toxic insults compared to cells derived from normal tissue, possibly due to higher glutathione and catalase antioxidant activities (Järvinen et al, 2000;Russo et al, 1986). Therefore, in addition to the A549 cell line, the clonogenic assay was also carried out on the normal bronchial epithelial cell line BEAS-2B.…”

Manganese superoxide dismutase is increased in the airways of smokers' lungs

“…A total of 50 mg of cell protein per lane was applied to a 12% SDS-PAGE and the gel was electrophoresed as previously described [18]. The blotted membrane was incubated with the antibody to CuZnSOD (diluted 1:10,000), MnSOD (diluted 1:10,000) or to ECSOD (diluted 1:2,500) followed by an anti-rabbit antibody conjugated to horseradish peroxidase (dilution 1:30,000; Amersham, Freiburg, Germany).…”