Frequent inactivation of RUNX3 by promoter hypermethylation and protein mislocalization in oral squamous cell carcinomas.
OBJECTIVE
RUNX3 is a functionally important component in transforming growth factor-beta (TGF-beta) mediated signaling pathway. Epigenetic silencing expression of RUNX3, as well as aberrant cytoplasmic retention of RUNX3 protein are causally involved in gastric carcinogenesis. Here, we examined the expression of RUNX3 gene and protein in oral squamous cell carcinomas (OSCCs) and analyzed the methylation status of RUNX3 promoter region.


METHODS
About 10 normal oral mucosa and 30 OSCCs were collected to examine RUNX3 expression by RT-PCR analysis and immunohistochemistry assay using anti-RUNX3 monoclonal antibody R3-6E9. Methylation-specific PCR was carried out on the same specimens to analyze the methylation status of RUNX3 promoter. In addition, the stored paraffin-embedded specimens, including 40 oral leucoplakia (OLK) and 120 OSCCs, were examined by immunohistochemistry assay.


RESULTS
RUNX3 gene and protein were underexpressed in OSCCs due to promoter hypermethylation. Protein mislocalization occurred frequently. Both downregulation of RUNX3 protein expression (P = 0.001) and protein mislocalization (P = 0.001) were correlated with the differentiation grades in OSCCs.


CONCLUSIONS
RUNX3 plays an important role in oral carcinogenesis. It may be a useful diagnostic marker and a potential therapeutic target for OSCC.
Gao
Feng
F
State Key Laboratory for Dental Medicines and West China College of Stomatology, Sichuan University, No. 14 Sec. 3 Renminnan Road, Chengdu, Sichuan, People's Republic of China.
Huang
Canhua
C
Lin
Mei
M
Wang
Zhi
Z
Shen
Jun
J
Zhang
Haiyuan
H
Jiang
Lu
L
Chen
Qianming
Q
D001483:Base Sequence; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D050677:Core Binding Factor Alpha 3 Subunit / Q000235:genetics*; D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D015536:Down-Regulation; D005260:Female; D005784:Gene Amplification; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D011401:Promoter Regions, Genetic; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction
D050677:Core Binding Factor Alpha 3 Subunit; D017931:DNA Primers; D004273:DNA, Neoplasm; D012334:RNA, Neoplasm; C493729:Runx3 protein, human