The tumor suppressor Wnt inhibitory factor 1 is frequently methylated in nasopharyngeal and esophageal carcinomas.
Aberrant activation of the wingless-type- (Wnt)-signaling pathway is common in many cancers including nasopharyngeal (NPC) and esophageal squamous cell (ESCC) carcinomas, both prevalent in Southern China and Southeast Asia. However, the molecular mechanism leading to this abnormality is still obscure. Wnt inhibitory factor-1 (WIF1) is a secreted antagonist of the Wnt pathway, and is recently shown to be inactivated by epigenetic mechanism in some tumors. Here, we examined whether WIF1 is also inactivated epigenetically in NPC and ESCC. With semiquantitative reverse transcription-PCR and methylation-specific PCR, we detected WIF1 downregulation or silencing in 6/6 of NPC and 12/19 of ESCC cell lines, which is well correlated with its methylation status. Methylation was further confirmed by high-resolution bisulfite genomic sequencing. Methylation was also frequently observed in a large collection of primary tumors of NPC (85%, 55/65) and ESCC (27%, 25/92), with WIF1 expressed and unmethylated in normal NPC and esophageal cell lines and normal tissues. Treatment of 5-aza-2'-deoxycytidine demethylated WIF1 and induced its expression in NPC and ESCC cell lines, highlighting a direct role of epigenetic inactivation. Ectopic expression of WIF1 in NPC and ESCC tumor cells resulted in significant inhibition of tumor cell colony formation, similar to TP53, and also significant downregulation of beta-catenin protein level in NPC cells. Thus, WIF1 functions as a tumor suppressor for both NPC and ESCC through suppressing the Wnt-signaling pathway, but is frequently silenced by epigenetic mechanism in a tumor-specific way. Our study indicates that epigenetic inactivation of WIF1 contributes to the aberrant activation of Wnt pathway and is involved in the pathogenesis of both tumors. WIF1 methylation could also serve as a specific biomarker for these tumors.
Chan
Stephen L
SL
Cancer Epigenetics Laboratory, State Key Laboratory in Oncology in South China, Department of Clinical Oncology, Sir YK Pao Center for Cancer, Hong Kong.
Cui
Yan
Y
van Hasselt
Andrew
A
Li
Hongyu
H
Srivastava
Gopesh
G
Jin
Hongchuan
H
Ng
Ka M
KM
Wang
Yajun
Y
Lee
Kwan Y
KY
Tsao
George S W
GS
Zhong
Sheng
S
Robertson
Keith D
KD
Rha
Sun Y
SY
Chan
Anthony T C
AT
Tao
Qian
Q
D048868:Adaptor Proteins, Signal Transducing / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D014408:Biomarkers, Tumor; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D000077209:Decitabine; D015536:Down-Regulation; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D051155:Wnt1 Protein / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D014408:Biomarkers, Tumor; D012097:Repressor Proteins; D025521:Tumor Suppressor Proteins; C485569:WIF1 protein, human; D051155:Wnt1 Protein; D000077209:Decitabine; D001374:Azacitidine