AKAP12/Gravin is inactivated by epigenetic mechanism in human gastric carcinoma and shows growth suppressor activity.
AKAP12/Gravin, one of the A-kinase anchoring proteins (AKAPs), functions as a kinase scaffold protein and as a dynamic regulator of the beta2-adrenergic receptor complex. However, the biological role of AKAP12 in cancer development is not well understood. The AKAP12 gene encodes two major isoforms of 305 and 287 kDa (designated AKAP12A and AKAP12B, respectively, in this report). We found that these two isoforms are independently expressed and that they are probably under the control of two different promoters. Moreover, both isoforms were absent from the majority of human gastric cancer cells. The results from methylation-specific PCR (MSP) and bisulfite sequencing revealed that the 5' CpG islands of both AKAP12A and AKAP12B are frequently hypermethylated in gastric cancer cells. Treatment with DNA methyltransferase inhibitor and/or histone deacetylase inhibitor efficiently restored the expression of AKAP12 isoforms, confirming that DNA methylation is directly involved in the transcriptional silencing of AKAP12 in gastric cancer cells. Hypermethylation of AKAP12A CpG island was also detected in 56% (10 of 18) of primary gastric tumors. The restoration of AKAP12A in AKAP12-nonexpressing cells reduced colony formation and induced apoptotic cell death. In conclusion, our results suggest that AKAP12A may function as an important negative regulator of the survival pathway in human gastric cancer.
Choi
Moon-Chang
MC
National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul National University College of Medicine, 28 Yongon-dong, Chongro-gu, Seoul 110-799, Korea.
Jong
Hyun-Soon
HS
Kim
Tai Young
TY
Song
Sang-Hyun
SH
Lee
Dong Soon
DS
Lee
Jung Weon
JW
Kim
Tae-You
TY
Kim
Noe Kyeong
NK
Bang
Yung-Jue
YJ
D054758:A Kinase Anchor Proteins; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D008934:Mitogens / Q000037:antagonists & inhibitors / Q000235:genetics*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology
D054758:A Kinase Anchor Proteins; C491162:AKAP12 protein, human; D018797:Cell Cycle Proteins; D017931:DNA Primers; D008934:Mitogens; D020033:Protein Isoforms