Gemcitabine chemoresistance and molecular markers associated with gemcitabine transport and metabolism in human pancreatic cancer cells

Abstract

To identify predictive molecular markers for gemcitabine resistance, we investigated changes in the expression of four genes associated with gemcitabine transport and metabolism during the development of acquired gemcitabine resistance of pancreatic cancer cell lines. The expression levels of human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (dCK), RRM1, and RRM2 mRNA were analysed by real-time light cycler-PCR in various subclones during the development of acquired resistance to gemcitabine. Real-time light cycler-PCR demonstrated that the expression levels of either RRM1 or RRM2 progressively increased during the development of gemcitabine resistance. Expression of dCK was slightly increased in cells resistant to lower concentrations of gemcitabine, but was decreased below the undetectable level in higher concentration-resistant subclones. Expression of hENT1 was increased in the development of gemcitabine resistance. As acquired resistance to gemcitabine seems to correlate with the balance of these four factors, we calculated the ratio of hENT1 Â dCK/RRM1 Â RRM2 gene expression in gemcitabine-resistant subclones. The ratio of gene expression decreased progressively with development of acquired resistance in gemcitabine-resistant subclones. Furthermore, the expression ratio significantly correlated with gemcitabine sensitivity in eight pancreatic cancer cell lines, whereas no single gene expression level correlated with the sensitivity. These results suggest that the sensitivity of pancreatic cancer cells to gemcitabine is determined by the ratio of four factors involved in gemcitabine transport and metabolism. The ratio of the four gene expression levels correlates with acquired gemcitabine-resistance in pancreatic cancer cells, and may be useful as a predictive marker for the efficacy of gemcitabine therapy in pancreatic cancer patients.

Epigenetic markers for chemosensitivity and chemoresistance in pancreatic cancer—A review

“…26 Nakano et al analyzed that the ratio of hENT1ÂdCK/RRM1ÂRRM2 expression decreased progressively with the development of acquired resistance in gemcitabine-resistant PC cell lines. 37 Nakahira et al reported that transfection of RRM1 siRNA resulted in >90% suppression of RRM1 messenger RNA (mRNA) and protein that was accompanied by a significantly reduced gemcitabine chemoresistance in human PC cell lines. Moreover, a clinical study with 18 recurrent PC patients treated by gemcitabine showed that patients with high RRM1 levels had diminished survival after …”

RRM2 (ribonucleotide reductase M2)

“…This results illustrated that expression ratio significantly correlated with gemcitabine sensitivity in eight pancreatic cancer cell lines, whereas no single gene expression level correlated with the sensitivity, indicating that the sensitivity of pancreatic cancer cells to gemcitabine is dependent on the ratio of four factors involved in gemcitabine transport and metabolism. On the one hand, the ratio of the four gene expression associated with acquired gemcitabine-resistance in pancreatic cancer cells (Nakano et al, 2007). Moreover, Duxbury et al, showed that small interfering RNA targeting RRM2 enhanced chemosensitivity to gemcitabine in pancreatic adenocarcinoma (Duxbury et al, 2004), suggesting its role as an attractive target for pancreatic cancer.…”

“…Moreover, they identified RRM2 as a biomarker for the chemo-preventive effect of NS-398 in pancreatic cancer cells (Youns et al, 2011). Previous study illustrated that over-expression of RRM2 was associated with resistance to gemcitabine in pancreatic cancer (Nakano et al, 2007). In this study the expression level of RRM2 was analysed by q-PCR in different subclones during the development of acquired resistance to gemcitabine.…”

Effect of arenobufagin on human pancreatic carcinoma cells

“…However, the response ratio of PDAC to gemcitabine in clinical research is <25%, and those patients showing initial response generally develop drug resistance during therapy (6,7). The development of rapid resistance to gemcitabine may be due to either stem-like subpopulations of tumor cells, which have innate resistance to chemotherapy, or be caused by molecular changes in cancer cells, such as alternations of transport and metabolism of gemcitabine or the upregulation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) or the DNA repair pathway (8)(9)(10)(11)(12). In addition to monotherapy, there are clinical treatments with gemcitabine in combination with other biological or chemotherapeutical targeted agents, such as the epidermal growth factor receptor (EGFR) inhibitors erlotinib, tipifarnib and gefitinib (13,14), but the combinations are limited, with unsatisfactory efficacy.…”