Expression of epidermal growth factors and apoptosis markers in pancreatic ductal adenocarcinoma

Effect of arenobufagin on human pancreatic carcinoma cells

Pancreatic carcinoma (PC) is a deadly form of cancer with poor overall survival. Currently, chemotherapy such as gemcitabine and 5-fluorouracil (5-FU) are the most popular medications that can improve survival, but rapid drug-resistance makes the search for more effective drugs urgent. Upon looking for natural components to treat PC, it was found that arenobufagin, a cardiac glycosides-like compound, showed significant effects on the gemcitabine-resistant pancreatic carcinoma cell line Panc-1 and the gemcitabine-sensitive cell line ASPC-1 at nanomolar concentrations. The present study used MTT and clonogenic survival assays to examine survival and proliferation, and western blotting to assess changes in the associated mitogen activated protein kinase and phosphoinositide 3-kinase pathways and expression of apoptosis-related proteins. The current study also detected the cell cycle by flow cytometry. Arenobufagin inhibited cell survival and proliferation, decreased the phosphorylation of key downstream proteins of K-Ras, including protein kinase B and extracellular signal related kinase, induced cell cycle G2/M phase arrest and apoptosis, and downregulated the level of phosphorylated epidermal growth factor receptor. Notably, the present data also showed that arenobufagin can enhance the sensitivity of PC cells to gemcitabine and 5-FU. In conclusion, arenobufagin could enhance the effect of gemcitabine and 5-FU on PC cells by targeting multiple key proteins. Therefore, arenobufagin has potential as anadjuvant therapy for the treatment of PC.

Deregulation of miR-146a expression in a mouse model of pancreatic cancer affecting EGFR signaling

Aberrant expression of microRNAs (miRNAs) plays important roles in the development and progression of pancreatic cancer (PC). Expression analysis of miR-146a in human PC tissues showed decreased expression in about 80% of samples compared to corresponding non-cancerous tissue. Moreover, expression of miR-146a in eight PC cell lines, and in pancreatic tissues obtained from transgenic mouse models of K-Ras (K), Pdx1-Cre (C), K-Ras;Pdx1-Cre (KC) and K-Ras;Pdx1-Cre;INK4a/Arf (KCI), showed down-regulation of miR-146a expression in KCI mice which was in part led to over-expression of its target gene, epidermal growth factor receptor (EGFR). Treatment of PC cells with CDF, a novel synthetic compound, led to re-expression of miR-146a, resulting in the down-regulation of EGFR expression. Moreover, re-expression of miR-146a by stable transfection or treatment with CDF in vivo (xenograft animal model) resulted in decreased tumor growth which was consistent with reduced EGFR, ERK1, ERK2, and K-Ras expression. Further knock-down of miR-146a in AsPC-1 cells led to the up-regulation of EGFR expression and showed increased clonogenic growth. In addition, knock-down of EGFR by EGFR siRNA transfection of parental AsPC-1 cells and AsPC-1 cells stably transfected with pre-miR-146a resulted in decreased invasive capacity, which was further confirmed by reduced luciferase activity in cells transfected with pMIR-Luc reporter vector containing miR-146a binding site. Collectively, these results suggest that the loss of expression of miR-146a is a fundamental mechanism for over-expression of EGFR signaling and that re-expression of miR-146a by CDF treatment could be useful in designing personalized strategy for the treatment of human PC.

Evaluation of phosphatidylinositol-3-kinase catalytic subunit (PIK3CA) and epidermal growth factor receptor (EGFR) gene mutations in pancreaticobiliary adenocarcinoma

BACKGROUND

Phosphatidylinositol-3-kinase (PI3K) activation involves the epidermal growth factor receptor (EGFR) and plays an important role in cell survival signaling in pancreaticobiliary cancer. EGFR gene mutations have been correlated with clinical response to EGFR inhibitors in patients with advanced non-small cell lung cancer. This study examined the prevalence of PIK3CA and EGFR mutations in pancreaticobiliary cancer where erlotinib, an EGFR inhibitor, is approved for therapy.

METHODS

Thirty patients who underwent pancreatectomy for pancreaticobiliary carcinoma were identified. Genomic DNA was extracted from formalin fixed paraffin embedded tumor and adjacent normal tissue, and exons 9 and 20 (for the PIK3CA gene) and exons 18-21 (for the EGFR gene) were amplified by PCR and sequenced. Literature review on EGFR and/or PIK3CA mutations in pancreaticobiliary adenocarcinomas was conducted.

RESULTS

No mutations in either PIK3CA or EGFR genes were identified. The study identified one synonymous single nucleotide polymorphism (SNP) (rs1050171) in the coding region of EGFR. A previously unreported change, suspected to be a SNP, was observed in intron 18 of EGFR (IVS18+15, C>T). Review of the literature showed EGFR mutation rate of 2% and 10.5% in pancreatic and biliary tract carcinomas, respectively. PIK3CA mutations were found in 3.6% and 11.7% of pancreatic and biliary tract carcinomas, respectively.

CONCLUSIONS

A low prevalence of EGFR or PIK3CA mutations exists in pancreatic cancer (<5%), indicating that mutation screening may not be as useful in determining prognosis or response to targeted inhibition.