RUNX1T1 Is a Novel Metastasis-Associated Tumor Suppressor Gene in Pancreatic Endocrine Carcinomas
NA Hafez, L Turner, J Skaf, S McCarthy, NA Nasir, A Hakam, D Coppola, P Hodul, LK Kvols, A Nasir. Moffitt Cancer Center, Tampa, FL
Background: RUNX1T1 is a gene present on chromosome 8. It had been shown to play different and significant role when it changes biological phenotype.The t(8;21)(q22;q22) was described thoroughly in acute myelogenous leukaemia that resulted in the transcription factor fusion protein, RUNX1-RUNX1T1 (also known as AML1-ETO). RUNX1T1 role was not described in Pancreatic Endocrine Tumors (PETS).
Design: Five clinically-localized primary (CLP)-PETS from 5 adult patients and 6 well-differentiated (WD) metastatic primary (MP)-PECAs from 6 other adult patients were profiled on Affymetrix U133 2.0 gene chip. The data were RMA normalized and t-test was used to identify genes differentially expressed in MP-PECAs vs. CLP-PETs. This gene set was further refined by excluding those with a significant frequency of Type I errors. Published literature was reviewed to select 'candidate progression genes' for further validation on the original frozen PETs/PECAs and also on independent test sets of archival MP-PECAs and CLP-PETs, using qRT-PCR. For real time PCR, TaqMan assays specific for those genes were spotted on TaqMan Arrays (ABI). For real-time data normalization, IPO8 was tested and was found stable across samples and was hence used as the endogenous control gene.
Results: 217 transcripts were differentially expressed between MP-PECAs and CLP-PETs, using p-value <0.05 and fold-change values >1.5. Among those with a fold-change >2, several exhibited a high level of reliability, based on similar patterns of differential expression for multiple probe sets targeting the same mRNA. On microarray, RUNX1T1 was down regulated and directional in all studied tumors. It was 2 folds or more down regulated in MP-PECAs compared NMP-PETs on microarray. When RUNX1T1 expression in nucleic acid extracted from frozen samples was measured using TaqMan Arrays, it was found to be under-expressed in MP-PECAs relative to NMP-PETs by a factor of 5.84 with a P value of 0.008. We also found a similar trend of down-regulation of RUNX1T1 on archival tumor sets, but with less obvious fold change.
Conclusions: RUNX1T1 is a novel 'putative tumor suppressor gene' in sporadic primary WD-pancreatic endocrine carcinomas that had synchronous liver metastases at the time of its resection. Further studies are required to investigate the clinical utility of this gene as a progression biomarker in pancreatic endocrine tumors and for developing new molecular therapy for these aggressive tumors.
Category: Liver & Pancreas
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 241, Wednesday Morning