Aberrant Expressions of AP-2α Splice Variants in Pancreatic Cancer

Objectives: The present study was conducted to evaluate the expression and function of AP-2 alpha isoforms in pancreatic ductal adenocarcinoma. Methods: The expression of AP-2 alpha was evaluated at the RNA level by reverse transcription-polymerase chain reaction and at the protein level by Western blotting and immunofluorescence. Its function as a transcription factor was evaluated in transient transfection experiments: DNA binding properties by electromobility shift assay and transactivation capabilities by luciferase assay. Results: Multiple alternative splicing events of AP-2 alpha messenger occurred in all human pancreatic cancer cell lines, including a novel isoform, termed variant 6, which was not present in HeLa cells. At the protein level, except for 1 cell line, all pancreatic cancer cell lines expressed high nuclear levels of AP-2 alpha. We also showed that AP-2 alpha expressed by the pancreatic cancer cell lines could bind its cognate recognition site and activate transcription. However, variant 6, although not able to activate transcription, did not act in a dominant negative manner when cotransfected with the full-length protein. Conclusions: Multiple isoforms of AP-2 alpha are highly expressed in pancreatic cancer cell lines including a new isoform, AP-2 alpha variant 6, which seems to be pancreatic cancer specific and is deprived of transcriptional activity.