MicroRNA-200b and -301 are associated with gemcitabine response as biomarkers in pancreatic carcinoma cells.

Chemotherapy resistance (congenital or acquired) is one of the principal challenges for the treatment of pancreatic carcinoma. Recent evidence has demonstrated that epithelial to mesenchymal transition (EMT) is associated with chemoresistance in pancreatic carcinoma cells. However, the molecular mechanism underlying the development of chemoresistance remains unknown, and limited therapeutic options are available. Therefore, to anticipate individual chemosensitivity or acquired chemoresistance for patients with pancreatic carcinoma, predictive biomarkers are urgently required. Extensive evidence suggests that microRNAs (miRNAs) serve a crucial role in regulating EMT. The aim of this study was to examine the potential role of miRNA (miR)­200b and miR­301 in predicting the chemo­responses to treatment for pancreatic carcinoma. The present results demonstrate that miR­200b expression predicted chemo­sensitivity and may have potential as a biomarker. In six different pancreatic carcinoma cell lines (Capan­1, Capan­2, Panc­1, MIAPaCa­2, BxPC­3 and PL45 cells), the expression of miR­200b correlated positively with chemosensitivity. Moreover, the enhanced expression of miR­200b increased chemosensitivity and induced mesenchymal to epithelial transition. Conversely, miR­301 modulated gemcitabine resistance and induced EMT through the downregulation of cadherin 1 expression. In addition, gemcitabine­resistant cells (Capan­2 and Panc­1) exhibited upregulated miR­301 expression and downregulated gemcitabine­induced apoptosis. In summary, these two miRNAs may serve roles as biomarkers in pancreatic carcinoma, miR­200b expression may predict chemosensitivity, and elevated miR­301 expression may have potential applications in the prediction of acquired gemcitabine resistance.

MicroRNA-301b promotes cell invasiveness through targeting TP63 in pancreatic carcinoma cells.

Recent studies have demonstrated that deregulated microRNA (miR) expression is implicated in the development of human cancers. In the aberrant miR expression, miR-301 is upregulated in cancers, such as pancreatic, colorectal and oral carcinoma. Based on this evidence, we investigated the contribution of miR-301 to pancreatic carcinoma and the novel target genes of miR-301 in pancreatic carcinoma. In this study, we analyzed the effects of enforced and inhibited expression of miR-301b expression in the Panc-1 and BxPC-3 cell lines. MiR-301b expression levels were associated with cell invasiveness in both cell lines. Additional experiments indicated that miR-301b influences invasiveness through CDH1. Moreover microRNA target search algorithms and experimental strategies suggested that miR-301b suppressed TP63 expression as a novel target of miR-301b. Remarkably, miR-301b was also found to be associated with NF-κB activity in both cell lines. In summary, overexpressed miR-301b may suppress TP63 expression and contributes to promote cell invasiveness and to enhance gemcitabine resistance in pancreatic carcinoma cells. Thus, miR-301b may have potential as a novel therapeutic target for cancer treatment due to its stimulatory effects on cell invasiveness.

Tetrahydrouridine inhibits cell proliferation through cell cycle regulation regardless of cytidine deaminase expression levels.

Tetrahydrouridine (THU) is a well characterized and potent inhibitor of cytidine deaminase (CDA). Highly expressed CDA catalyzes and inactivates cytidine analogues, ultimately contributing to increased gemcitabine resistance. Therefore, a combination therapy of THU and gemcitabine is considered to be a potential and promising treatment for tumors with highly expressed CDA. In this study, we found that THU has an alternative mechanism for inhibiting cell growth which is independent of CDA expression. Three different carcinoma cell lines (MIAPaCa-2, H441, and H1299) exhibited decreased cell proliferation after sole administration of THU, while being unaffected by knocking down CDA. To investigate the mechanism of THU-induced cell growth inhibition, cell cycle analysis using flow cytometry was performed. This analysis revealed that THU caused an increased rate of G1-phase occurrence while S-phase occurrence was diminished. Similarly, Ki-67 staining further supported that THU reduces cell proliferation. We also found that THU regulates cell cycle progression at the G1/S checkpoint by suppressing E2F1. As a result, a combination regimen of THU and gemcitabine might be a more effective therapy than previously believed for pancreatic carcinoma since THU works as a CDA inhibitor, as well as an inhibitor of cell growth in some types of pancreatic carcinoma cells.

Hydroxyurea decreases gemcitabine resistance in pancreatic carcinoma cells with highly expressed ribonucleotide reductase.

OBJECTIVES: This study aimed to determine whether the treatment of pancreatic carcinoma can be defined on the basis of the expression of genes involved in gemcitabine metabolism and whether combination treatment is more effective than conventional treatment. METHODS: Four pancreatic carcinoma cell lines (Panc-1, MIAPaCa-2, BxPC-3, and Capan-2) were used to determine the patterns of gemcitabine-metabolizing genes and mesenchymal marker gene expressions using quantitative real-time polymerase chain reaction. Chemosensitivity and cell proliferation were measured using colorimetric assay. Gemcitabine was combined with hydroxyurea or small interfering RNA targeting ribonucleotide reductase to assess changes in chemoresistance. RESULTS: Panc-1 and MIAPaCa-2 cell lines were profoundly chemoresistant and expressed genes corresponding to cells with distinct mesenchymal phenotypes. In addition, Panc-1 highly expressed ribonucleotide reductase and showed a 4-fold increase in gemcitabine sensitivity after treatment with hydroxyurea. CONCLUSIONS: Combination treatment tailored to cells with highly expressed ribonucleotide reductase was more effective than treatment with gemcitabine alone. Moreover, phenotype and gemcitabine metabolism may independently confer chemoresistance.