Modulation of mitogen-activated protein kinases by 6-nitro-7-hydroxycoumarin mediates apoptosis in renal carcinoma cells

6-Nitro-7-hydroxycoumarin has previously been shown to be a selective anti-proliferative agent capable of activating p38, stress-activated protein kinase (SAPK) and mitogen-activated protein (MAP) kinase in the human renal cell carcinoma cell line, A-498. Here, the role of p38 MAP kinase was further investigated in relation to its participation in 6-nitro-7-hydroxycoumarin induced apoptosis. 6-Nitro-7-hydroxycournarin was shown to alter cell cycle progression, leading to the appearance of a sub-G, peak, containing hypodiploid DNA, accompanied by increases in both poly(ADP-ribose)polymerase cleavage and decreased expression of cyclin D1. Drug treatment also lead to a rise in the expression in the cyclin-dependent kinase inhibitor, p21(WAFI/CIPl), and the appearance of inter-nucleosomal DNA cleavage and morphological changes, consistent with apoptotic cell death. Using a p38 MAP kinase inhibitor, SB203580, caused expression of p21(WAFI/CIPl) to be suppressed and both cleaved poly(ADP-ribose)polymerase and the numbers of apoptotic cells were decreased. In summary, this study shows the participation of p38 MAP kinase in 6-nitro-7-hydroxycoumarin induced apoptosis of A-498 cells and suggests that targeting of p38 may represent a novel mechanism to inhibit renal cell carcinoma and that coumarin type drugs require further investigation as potential anticancer agents directed against renal cell carcinoma. (C) 2003 Elsevier B.V. All rights reserved.