Loss of the eukaryotic initiation factor 3f in pancreatic cancer

Abstract

Aberrant regulation of the translation initiation is known to contribute to tumorigenesis. eIF3 plays an important role in translation initiation. eIF3f is the p47 subunit of the eIF3 complex whose function in cancer is not clear. Initial studies from our group indicated that eIF3f expression is decreased in pancreatic cancer. Overexpression of eIF3f induces apoptosis in pancreatic cancer cells. The eIF3f gene is located at chromosome band region 11p15.4. Loss of 11p15.4 is a common event in many tumors including pancreatic cancer. In order to investigate the molecular mechanism of the decreased expression of eIF3f in pancreatic cancer, we performed loss of heterozygosity (LOH) analysis in 32 pancreatic cancer specimens using three microsatellite markers encompassing the eIF3f gene. We showed that the prevalence of LOH ranged from 71% to 93%. We also performed eIF3f gene copy number analysis using quantitative real time PCR to further confirm the specific allelic loss of eIF3f gene in pancreatic cancer. We demonstrated a statistically significant decrease of eIF3f gene copy number in pancreatic tumors compared with normal tissues with a tumor/normal ratio of 0.24. Furthermore, RNA in situ hybridization and tissue microarray immunohistochemistry analysis demonstrated that eIF3f expression is significantly decreased in human pancreatic adenocarcinoma tissues compared to normal pancreatic tissues. These data provides new insight into the understanding of the molecular pathogenesis of eIF3f during pancreatic tumorigenesis.

Figure 1

Representative examples of LCM in pancreatic cancer and normal tissues captured on the caps and the remaining tissues. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Figure 2

A representative example of the genotyping profile at the D11S1338 locus. The electropherograms show the disappearance of one allele peak area in pancreatic cancer tissue.

Figure 3

Decreased eIF3f gene copy number in pancreatic cancer specimens. Laser captured microdissected pancreatic cancer tissues were collected and genomic DNAs were isolated. Relative eIF3f gene copy number was analyzed by quantitative real time PCR. The numbers are expressed as a ratio of eIF3f gene copy number over β-actin gene. We analyzed 10 normal samples and 12 pancreatic cancer tissues in triplicate.

Figure 4

eIF3f mRNA is decreased in pancreatic cancer. RNA in situ hybridization was performed in normal and pancreatic cancer tissue specimens. eIF3f sense probe was served as negative control. The positive signal is shown in blue. The slides were counterstained with methylene green. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

Figure 5

eIF3f protein is decreased in pancreatic cancer. Immunohistochemistry was performed on a pancreatic cancer tissue microarray using eIF3f antibody. Representative immunohistochemistry analysis of eIF3f protein in normal pancreas and different stages of pancreatic cancer tissues were shown. Magnification: 400×. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]