Relationship between single nucleotide polymorphisms in the deoxycytidine kinase gene and chemosensitivity of gemcitabine in six pancreatic cancer cell lines

Background Single nucleotide polymorphisms （SNPs） in the deoxycytidine kinase （dCK） gene are associated with chemosensitivity to nucleoside analogs. 2＇,2＇-Difluoro 2＇-deoxycytidine （gemcitabine） is a first-line nucleoside analog drug in the treatment of pancreatic cancer. However, the association between SNPs in the dCK gene and chemosensitivity to gemcitabine has not been fully established. Therefore, the present study aimed to investigate the relationship between SNPs in the dCKgene and chemosensitivity to gemcitabine in human pancreatic cancer cell lines.Methods Seven SNPs in the dCK gene were sequenced in six human pancreatic cancer cell lines. The chemosensitivity of these six cell lines to gemcitabine were evaluated in vitro with a Cell Counting Kit-8 （CCK-8） test.Inhibition rates were used to express the chemosensitivity of pancreatic cancer cell lines to gemcitabine.Results The genotype of the A9846G SNP in the dCKgene was determined in six human pancreatic cancer cell lines.The cell lines BxPC-3 and T3M4 carried the A9846G SNP genotype AG, whereas cell lines AsPC-1, Mia PaCa2, SW1990 and SU86.86 carried the GG genotype. Cell lines with the AG genotype （BxPC-3 and T3M4） were more sensitive to gemcitabine compared with cell lines with the GG genotype （AsPC-1, Mia PaCa2, SW1990 and SU86.86） and significantly different inhibition rates were observed between cell lines carrying the AG and GG genotypes （P 〈0.01）.Conclusions Variants in the A9846G SNP of the dCK gene were associated with sensitivity to gemcitabine in pancreatic cancer cell lines. The dCK A9846G SNP may act as a genetic marker to predict chemotherapy efficacy of gemcitabine in pancreatic cancer.

Association of polymorphisms of cytosine arabinoside- metabolizing enzyme gene with therapeutic efficacy for acute myeloid leukemia

Background The cytosine arabinoside （Ara-C）-based chemotherapy is the major remedial measure for acute myeloid leukemia （AML）. Deoxycytidine kinase （DCK） and cytidine deaminase （CDA） are the key enzymes in the metabolism of Ara-C. Many single nucleotide polymorphisms （SNPs） and haplotypes of DCK and CDA, which contribute to susceptibility to Ara-C, have been identified in Africans and Europeans. However, there has been no report about the relation among three SNPs in DCK （rs115543896, rs72552079, and rs111454937） and two SNPs in CDA （rs2072671 and rs60369023）, and their clinical response to Ara-C for a Chinese population. In this study, we aimed to investigate whether these five SNPs are associated with the therapeutic outcomes of Ara-C-based chemotherapy regimens in patients with AML. Methods A total of 151 Chinese patients with AML were enrolled in our study. SNPs genotyping were performed using the MassARRAY system by means of the matrix-assisted laser desorption ionization-time of flight mass spectrometry （MALDI-TOF-MS） method. Results The results illustrated that DCKrs111454937 AA genotype was more frequent in patients with higher platelet count, and A allele frequency was significantly higher in the group 〈40 years, lower white blood cell （WBC） count patients group and the group with platelet counts 〉60xl0e/L. Meanwhile, both DCKrs72552079 TC （OR=1.225, 95% C1=1.225-9.851, P=0.0192） and CDArs60369023 GA （OR=9.851,95% C1=1.31-77.93, ,~=-0.0263） significantly improved Ara-C-based chemotherapy response. While DCKrs11554389 AA （OR=0.147, 95% CI=0.027-0.801, P=0.0267） was associated with the decrease of Ara-C-based chemotherapy response. Conclusion It is evident that the DCK and CDA polymorphisms might be the important markers for the AML patients＇ therapy outcomes in a Chinese population.

Development of gemcitabine-resistant patient-derived xenograft models of pancreatic ductal adenocarcinoma

Aim:Gemcitabine is a frontline agent for locally-advanced and metastatic pancreatic ductal adenocarcinoma(PDAC),but neither gemcitabine alone nor in combination produces durable remissions of this tumor type.We developed three PDAC patient-derived xenograft(PDX)models with gemcitabine resistance(gemR)acquired in vivo,with which to identify mechanisms of resistance relevant to drug exposure in vivo and to evaluate novel therapies.Methods:Mice bearing independently-derived PDXs received 100 mg/kg gemcitabine once or twice weekly.Tumors initially responded,but regrew on treatment and were designated gemR.We used immunohistochemistry to compare expression of proteins previously associated with gemcitabine resistance[ribonucleotide reductase subunit M1(RRM1),RRM2,human concentrative nucleoside transporter 1(hCNT1),human equilibrative nucleoside transporter 1(hENT1),cytidine deaminase(CDA),and deoxycytidine kinase(dCK)]in gemR and respective gemcitabine-naïve parental tumors.Results:Parental and gemR tumors did not differ in tumor cell morphology,amount of tumor-associated stroma,or expression of stem cell markers.No consistent pattern of expression of the six gemR marker proteins was observed among the models.Increases in RRM1 and CDA were consistent with in vitro-derived gemR models.However,rather than the expected decreases of hCNT1,hENT1,and dCK,gemR tumors expressed no change in or higher levels of these gemR marker proteins than parental tumors.Conclusion:These models are the first PDAC PDX models with gemcitabine resistance acquired in vivo.The data indicate that mechanisms identified in models with resistance acquired in vitro are unlikely to be the predominant mechanisms when resistance is acquired in vivo.Ongoing work focuses on characterizing unidentified mechanisms of gemR and on identifying agents with anti-tumor efficacy in these gemR models。

Attempts to remodel the pathways of gemcitabine metabolism: Recent approaches to overcoming tumours with acquired chemoresistance

Gemcitabine is a cytidine analogue frequently used in the treatment of various cancers.However,the development of chemoresistance limits its effectiveness.Gemcitabine resistance is regulated by various factors,including aberrant genetic and epigenetic controls,metabolism of gemcitabine,the microenvironment,epithelial-to-mesenchymal transition,and acquisition of cancer stem cell properties.In many situations,results using cell lines offer valuable lessons leading to the first steps of important findings.In this review,we mainly discuss the factors involved in gemcitabine metabolism in association with chemoresistance,including nucleoside transporters,deoxycytidine kinase,cytidine deaminase,and ATP-binding cassette transporters,and outline new perspectives for enhancing the efficacy of gemcitabine to overcome acquired chemoresistance.