RT Journal Article
SR Electronic
T1 Exon 11 Skipping of E-Cadherin RNA Downregulates Its Expression in Head and Neck Cancer Cells
JF Molecular Cancer Therapeutics
JO Mol Cancer Ther
FD American Association for Cancer Research
DO 10.1158/1535-7163.MCT-11-0248
A1 Sharma, Sanjai
A1 Liao, Wei
A1 Zhou, Xiaofeng
A1 Wong, David T.W.
A1 Lichtenstein, Alan
YR 2011
UL http://mct.aacrjournals.org/content/early/2011/08/26/1535-7163.MCT-11-0248.abstract
AB E-cadherin is an important tumor suppressor gene whose expression is lost when cells acquire a metastatic phenotype. We analyzed the role of E-cadherin missplicing as a mechanism of its downregulation by analyzing a misspliced E-cadherin transcript that lacks exon 11 of this gene. This results in a frameshift and a premature termination codon that targets this transcript for degradation. Tumor tissues, including breast (20%, n = 9), prostate (30%, n = 9) and head and neck (75%, n = 8) cancer, express the exon 11-skipped transcripts (vs. nonmalignant controls) and its levels inversely correlate with E-cadherin expression. This is a novel mechanism of E-cadherin downregulation by missplicing in tumor cells, which is observed in highly prevalent human tumors. In the head and neck cancer model, nontumorigenic keratinocytes express exon 11–skipped splice product two- to sixfold lower than the head and neck tumor cell lines. Mechanistic studies reveal that SFRS2 (SC35), a splicing factor, as one of the regulators that increases missplicing and downregulates E-cadherin expression. Furthermore, this splicing factor was found to be overexpressed in 5 of 7 head and neck cell lines and primary head and neck tumors. Also, methylation of E-cadherin gene acts as a regulator of this aberrant splicing process. In 2 head and neck cell lines, wild-type transcript expression increased 16- to 25-folds, whereas the percentage of exon 11-skipped transcripts in both the cell lines decreased five- to 30-folds when cells were treated with a hypomethylating agent, azacytidine. Our findings reveal that promoter methylation and an upregulated splicing factor (SFRS2) are involved in the E-cadherin missplicing in tumors. Mol Cancer Ther; 10(9); 1751–9. ©2011 AACR.