Differential formation of beta-catenin/lymphoid enhancer factor-1 DNA binding complex induced by nitric oxide in mouse colonic epithelial cells differing in adenomatous polyposis coli (Apc) genotype
Jm. Mei et al., Differential formation of beta-catenin/lymphoid enhancer factor-1 DNA binding complex induced by nitric oxide in mouse colonic epithelial cells differing in adenomatous polyposis coli (Apc) genotype, CANCER RES, 60(13), 2000, pp. 3379-3383
increased cytoplasmic beta-catenin levels and the associated nuclear beta-c
atenin/T-cell factor (Tcf)-lymphoid enhancer factor (I,EF) complex formatio
n have been frequently found in colon cancer, In this context, overproducti
on of nitric oxide (NO) attributable to inflammatory stimuli in diseases su
ch as ulcerative colitis and Crohn's disease may contribute to colonic carc
inogenesis. Therefore, we examined the modulation by NO of cytoplasmic beta
-catenin levels and the formation of the nuclear beta-catenin/LEF-1 DNA bin
ding complex in conditionally immortalized mouse colonic epithelial cells t
hat differed in adenomatous polyposis coli (Apc) genotype, namely young adu
lt mouse colon (YAMC; Apc(+/+)) and immortal mouse colon epithelium (IMCE;
Apc-(Min/+)). Unlike most colon canter cell lines, this pair of cell lines
has either nondetectable or low basal level of beta-catenin when they are c
ultured under non-permissive and nonproliferative conditions. Using electro
phoretic mobility shift assays, se found that NO-releasing agents (E)-methy
l-2-[(E)-hydroxy- imino]-5-nitro-6-methoxy-3-hexeneamide and S-nitroso-N-ac
etylpenicillamine greatly enhanced the formation of beta-catenin/LEF-1 DNA
binding complex in a concentration- and time-dependent fashion in YAMC and
IMCE cells, Significantly, IMCE cells showed a markedly greater amount of n
uclear beta-catenin/LEF-1 DNA binding complex in response to NO. Super shif
t by anti-beta-catenin antibody confirmed the presence of beta-catenin in t
he complex. Western blot analysis of the soluble cytoplasmic fractions demo
nstrated that these NO donors caused differential accumulation of cytoplasm
ic beta-catenin in YAMC and LR ICE. In conclusion, this study indicates tha
t the defective beta-catenin degradation machinery attributable to Apc(Min/
+) mutation in LR;ICE cells not only affects basal levels but also contribu
tes to NO-induced dysregulation of cytoplasmic beta-catenin and nuclear bet
a-catenin/LEF-1 DNA binding complex formation.