Promoter methylation regulates cadherin switching in squamous cell carcinoma.
Cadherins are cell adhesion molecules that modulate the epithelial phenotype and regulate tumor invasion. To identify the role of promoter methylation in regulating E-cadherin expression and in the "switching" of cadherins in oral squamous cell carcinoma (SCC), we studied 14 cell lines for cadherin expression. Immunoblotting revealed that only two (HOC-313 and HA-376) showed strong up-regulation of N-cadherin, and neither expressed E-cadherin. These results were confirmed by PCR. Furthermore, analysis of genomic DNA showed that the lack of E-cadherin expression in the two cell lines was not due to gene deletion. In both cell lines, methylation-specific PCR indicated extensive methylation of the 5' CpG island in the E-cadherin promoter. After treatment with a DNA methylation inhibitor (5-Aza-2-deoxycytidine), both immunoblotting and immunofluorescence staining showed that HA-376 cells newly expressed E-cadherin with a parallel decrease in their N-cadherin expression. Multiplex RT-PCR demonstrated that the down-regulation of N-cadherin mRNA was coordinately regulated with E-cadherin expression. Thus, methylation of the 5' CpG island in the E-cadherin promoter induces reciprocal expression of E- and N-cadherins in oral SCC by an unknown mechanism that appears to be mediated at the level of N-cadherin gene expression. These events may play an important role in the regulation of tumor cell mobility and invasion.
Oral Cancer Research Center, Department of Stomatology, University of California at San Francisco, San Francisco, CA 94143-0422, USA.
Qianming
Q
Chen
Galina
G
Lipkina
Qi
Q
Song
Randall H
RH
Kramer
D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000494:pharmacology; D015820:Cadherins / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D015536:Down-Regulation; D019085:Fluorescent Antibody Technique, Direct; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D009062:Mouth Neoplasms / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D000964:Antimetabolites, Antineoplastic; D015820:Cadherins; D012333:RNA, Messenger; D001374:Azacitidine