P16

文字方塊: Replicative Senescence
 
                         

                               

P16

 
 


 

 

 

 

 

The p16(INK4A)/CDKN2A (p16) tumor suppressor gene is known to be inactivated in up to 98% of human pancreatic cancer specimens. Chemically induced pancreatic tumors in Syrian golden hamsters have been demonstrated to share many morphological and biological similarities with human pancreatic tumors and represent a potentially suitable model for the evaluation of therapies targeting p16. The purpose of this study was to evaluate primary hamster pancreatic tumor specimens for potentially inactivating p16 alterations. Tumors were induced with N-nitroso-bis-(2-oxopropyl) amine, followed by two cycles of augmentation pressure, and were harvested on day 100. Foci of tumor cells were identified by light microscopy after staining with hematoxilyn and eosin, and corresponding tumor tissues were excised for DNA extraction. The techniques of multiplex real-time PCR, direct sequencing, and methylation-specific PCR were used to evaluate 30 tumor specimens for homozygous deletions, mutations, and aberrant methylation of 5' CpG islands, respectively. Homozygous deletions were identified in 11 of 30 (36.7%) specimens, mutations were identified in 4 of 30 (13.3%) specimens, and aberrant methylation of 5' CpG islands was found in 14 of 30 (46.7%) specimens. The overall frequency of p16 alterations was 93.3% (28 of 30 specimens) and the majority of changes (83.3%) were noted to be secondary to methylation or homozygous deletion. The four mutations significantly impaired cyclin-dependent kinase 4 inhibitory activity, and two resulted in perturbation of the global structure of P16 protein. These findings indicate that p16 inactivation is a common event in chemically induced hamster tumors, and that this animal model is appropriate for comparative studies evaluating pancreatic cancer therapeutic strategies targeting p16.