Aminoflavone (AF;
NSC 686288, AFP464, NSC710464) is a new anticancer
drug that has recently entered phase II clinical trials. It has demonstrated antiproliferative effects in MCF-7 human
breast cancer cells mediated by the
aryl hydrocarbon receptor (AhR). AF also exhibits noteworthy evidence of antitumor activity in vitro and in vivo against neoplastic cells of renal origin. AF treatment of sensitive renal cells, in contrast to resistant cells, promotes the induction of
CYP1A1, the covalent binding of AF-reactive intermediates and apoptosis. Based on this evidence, the aim of this study was to evaluate the role of AhR, the main transcriptional regulator of
CYP1A1, in the antiproliferative effects of AF in human
renal cancer cells. AF-cytoxicity in human renal cell lines and a
renal cancer cell strain was assessed by MTS assay in the presence or absence of an Ahr inhibitor.
Drug-induced AhR nuclear translocation was evaluated by western blotting of AhR in cytosolic and nuclear fractions and by measuring
xenobiotic response element-driven
luciferase activity. Apoptosis induced by the
drug was evaluated by
4,6-diamidino-2-phenylindole and
acridine orange/
ethidium bromide staining and by measuring phosphorylated P53 (p-P53) and P21 levels,
caspase 3 activation and
poly(ADP-ribose) polymerase cleavage. AF inhibited cell growth in a dose-dependent manner in TK-10, Caki-1, SN12-C and A498 human renal cells but not in ACHN cells. The antiproliferative effect of AF was abrogated by pre-incubation of TK-10, Caki-1 and SN12-C cells with the AhR antagonist, α-naphthoflavone. AF treatment also induced apoptosis in TK-10, Caki-1 and SN12-C cells, which was not observed in ACHN cells. AF induced time-dependent AhR nuclear translocation and AhR transcriptional activity in sensitive
renal cancer cell lines. A renal cell strain derived from a human papillary
tumor also showed sensitivity to AF, as well as AhR pathway activation and
drug-induced apoptosis. AhR translocation could be included as a marker of sensitivity to AF in sensitive renal
tumor cells of different histological origin, in ongoing phase II clinical trials.