RESUMO
OBJECTIVES: The antioxidant status of cancer cells is an important factor in tumor invasion and metastases. This study investigated whether metastatic cancer cells derive beneficial antioxidant protection from ascitic fluid and are rendered resistant to oxidative stress in the form of a chemically generated free radical insult. METHODS: Human gastric carcinoma (KATO-III) and ovarian adenocarcinoma (SKOV-3) cell lines were cultured and incubated for 24 h with (1) M199 medium; (2) M199 + 20% fetal calf serum (FCS); (3) malignant ascites. All cells were exposed to a hydroxyl radical-generating system for 1 h. Cellular lipid peroxidation was assessed by measuring malondialdehyde (MDA) in cell suspensions. Glutathione (GSH) levels in cell pellet were measured in SKOV-3 cells after 0, 24, 48, and 72 h of incubation with buthionine sulphoximine (BSO). CD44 gene expression of cancer cells was analyzed by Northern blotting. RESULTS: The results showed that the cancer cells were rendered resistant to oxidative stress and with upregulated CD44 gene expression by components of malignant ascites. CONCLUSIONS: These findings suggest that malignant ascites increases the antioxidant ability of cancer cells and the potential of adhesion and invasion. Thus, determination of the nature of these putative tumor-protective components of ascites may provide targets for therapeutic intervention.