TY - JOUR
T1 - Vitamin D receptor ligands, adenomatous polyposis coli, and the vitamin D receptor FokI polymorphism collectively modulate β-catenin activity in colon cancer cells
AU - Egan, Jan B.
AU - Thompson, Patricia A.
AU - Vitanov, Milen V.
AU - Bartik, Leonid
AU - Jacobs, Elizabeth T.
AU - Haussler, Mark R.
AU - Gerner, Eugene W.
AU - Jurutka, Peter
PY - 2010/4
Y1 - 2010/4
N2 - The activity of β-catenin, commonly dysregulated in human colon cancers, is inhibited by the vitamin D receptor (VDR), and this mechanism is postulated to explain the putative anti-cancer activity of vitamin D metabolites in the colon. We investigated the effect of a common FokI restriction site polymorphism (F/f) in the human VDR gene as well as the effect of anti-tumorigenic 1,25-dihydroxyvitamin D3 (1,25D) and pro-tumorigenic lithocholic acid (LCA) VDR ligands on β-catenin transcriptional activity. Furthermore, the influence of a major regulatory protein of β-catenin, the APC tumor suppressor gene, on VDR-dependent inhibition of β-catenin activity was examined. We report herein that β-catenin-mediated transcription is most effectively suppressed by the VDR FokI variant F/M4 when 1,25D is limiting. Using Caco-2 colorectal cancer (CRC) cells, it was observed that VDR ligands, 1,25D and LCA, both suppress β-catenin transcriptional activity, though 1,25D exhibited significantly greater inhibition. Moreover, 1,25D, but not LCA, suppressed endogenous expression of the β-catenin target gene DKK-4 independent of VDR DNA-binding activity. These results support β-catenin sequestration away from endogenous gene targets by 1,25D-VDR. This activity is most efficiently mediated by the FokI gene variant F/M4, a VDR allele previously associated with protection against CRC. Interestingly, we found the inhibition of β-catenin activity by 1,25D-VDR was significantly enhanced by wildtype APC. These results reveal a previously unrecognized role for 1,25D-VDR in APC/β-catenin cross talk. Collectively, these findings strengthen evidence favoring a direct effect on the Wnt-signaling molecule β-catenin as one anti-cancer target of 1,25D-VDR action in the colorectum.
AB - The activity of β-catenin, commonly dysregulated in human colon cancers, is inhibited by the vitamin D receptor (VDR), and this mechanism is postulated to explain the putative anti-cancer activity of vitamin D metabolites in the colon. We investigated the effect of a common FokI restriction site polymorphism (F/f) in the human VDR gene as well as the effect of anti-tumorigenic 1,25-dihydroxyvitamin D3 (1,25D) and pro-tumorigenic lithocholic acid (LCA) VDR ligands on β-catenin transcriptional activity. Furthermore, the influence of a major regulatory protein of β-catenin, the APC tumor suppressor gene, on VDR-dependent inhibition of β-catenin activity was examined. We report herein that β-catenin-mediated transcription is most effectively suppressed by the VDR FokI variant F/M4 when 1,25D is limiting. Using Caco-2 colorectal cancer (CRC) cells, it was observed that VDR ligands, 1,25D and LCA, both suppress β-catenin transcriptional activity, though 1,25D exhibited significantly greater inhibition. Moreover, 1,25D, but not LCA, suppressed endogenous expression of the β-catenin target gene DKK-4 independent of VDR DNA-binding activity. These results support β-catenin sequestration away from endogenous gene targets by 1,25D-VDR. This activity is most efficiently mediated by the FokI gene variant F/M4, a VDR allele previously associated with protection against CRC. Interestingly, we found the inhibition of β-catenin activity by 1,25D-VDR was significantly enhanced by wildtype APC. These results reveal a previously unrecognized role for 1,25D-VDR in APC/β-catenin cross talk. Collectively, these findings strengthen evidence favoring a direct effect on the Wnt-signaling molecule β-catenin as one anti-cancer target of 1,25D-VDR action in the colorectum.
KW - 1,25-dihydroxyvitamin D
KW - Colorectal cancer
KW - Lithocholic acid
KW - Single nucleotide polymorphisms
KW - Wnt signaling
UR - http://www.scopus.com/inward/record.url?scp=77951661630&partnerID=8YFLogxK
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U2 - 10.1002/mc.20603
DO - 10.1002/mc.20603
M3 - Article
C2 - 20043299
AN - SCOPUS:77951661630
SN - 0899-1987
VL - 49
SP - 337
EP - 352
JO - Molecular Carcinogenesis
JF - Molecular Carcinogenesis
IS - 4
ER -