Deoxycitidine kinase is associated with prolonged survival after adjuvant gemcitabine for resected pancreatic adenocarcinoma

Understanding the Conundrum of Pancreatic Cancer in the Omics Sciences Era

Pancreatic cancer (PC) is an increasing cause of cancer-related death, with a dismal prognosis caused by its aggressive biology, the lack of clinical symptoms in the early phases of the disease, and the inefficacy of treatments. PC is characterized by a complex tumor microenvironment. The interaction of its cellular components plays a crucial role in tumor development and progression, contributing to the alteration of metabolism and cellular hyperproliferation, as well as to metastatic evolution and abnormal tumor-associated immunity. Furthermore, in response to intrinsic oncogenic alterations and the influence of the tumor microenvironment, cancer cells undergo a complex oncogene-directed metabolic reprogramming that includes changes in glucose utilization, lipid and amino acid metabolism, redox balance, and activation of recycling and scavenging pathways. The advent of omics sciences is revolutionizing the comprehension of the pathogenetic conundrum of pancreatic carcinogenesis. In particular, metabolomics and genomics has led to a more precise classification of PC into subtypes that show different biological behaviors and responses to treatments. The identification of molecular targets through the pharmacogenomic approach may help to personalize treatments. Novel specific biomarkers have been discovered using proteomics and metabolomics analyses. Radiomics allows for an earlier diagnosis through the computational analysis of imaging. However, the complexity, high expertise required, and costs of the omics approach are the main limitations for its use in clinical practice at present. In addition, the studies of extracellular vesicles (EVs), the use of organoids, the understanding of host-microbiota interactions, and more recently the advent of artificial intelligence are helping to make further steps towards precision and personalized medicine. This present review summarizes the main evidence for the application of omics sciences to the study of PC and the identification of future perspectives.

Hyperthermia improves gemcitabine sensitivity of pancreatic cancer cells by suppressing the EFNA4/β-catenin axis and activating dCK

Background

Previously, our investigations have underscored the potential of hyperthermia to improve the therapeutic efficacy of gemcitabine (GEM) in pancreatic cancer (PC). Nonetheless, the precise underlying mechanisms remain elusive.

Methods

We engineered two GEM-resistant PC cell lines (BxPC-3/GEM and PANC-1/GEM) and treated them with GEM alongside hyperthermia. The impact of hyperthermia on the therapeutic potency of GEM was ascertained through MTT assay, assessment of the concentration of its active metabolite dFdCTP, and evaluation of deoxycytidine kinase (dCK) activity. Lentivirus-mediated dCK silencing was further employed to validate its involvement in mediating the GEM-sensitizing effect of hyperthermia. The mechanism underlying hyperthermia-mediated dCK activation was explored using bioinformatics analyses. The interplay between hyperthermia and the ephrin A4 (EFNA4)/β-catenin/dCK axis was investigated, and their roles in GEM resistance was further explored via the establishment of xenograft tumor models in nude mice.

Results

Hyperthermia restored dCK expression in GEM-resistant cell lines, concurrently enhancing GEM sensitivity and fostering DNA damage and cell death. These observed effects were negated by dCK silencing. Regarding the mechanism, hyperthermia activated dCK by downregulating EFNA4 expression and mitigating β-catenin activation. Overexpression of EFNA4 activated the β-catenin while suppressing dCK, thus diminishing cellular GEM sensitivity-a phenomenon remediated by the β-catenin antagonist MSAB. Consistently, in vivo, hyperthermia augmented the therapeutic efficacy of GEM on xenograft tumors through modulation of the ephrin A4/β-catenin/dCK axis.

Conclusion

This study delineates the role of hyperthermia in enhancing GEM sensitivity of PC cells, primarily mediated through the suppression of the EFNA4/β-catenin axis and activation of dCK.

PTEN deficiency facilitates gemcitabine efficacy in cancer by modulating the phosphorylation of PP2Ac and DCK

Gemcitabine is a nucleoside analog that has been successfully used in the treatment of multiple cancers. However, intrinsic or acquired resistance reduces the chemotherapeutic potential of gemcitabine. Here, we revealed a previously unappreciated mechanism by which phosphatase and tensin homolog (PTEN), one of the most frequently mutated genes in human cancers, dominates the decision-making process that is central to the regulation of gemcitabine efficacy in cholangiocarcinoma (CCA). By investigating a gemcitabine-treated CCA cohort, we found that PTEN deficiency was correlated with the improved efficacy of gemcitabine-based chemotherapy. Using cell-based drug sensitivity assays, cell line-derived xenograft, and patient-derived xenograft models, we further confirmed that PTEN deficiency or genetic-engineering down-regulation of PTEN facilitated gemcitabine efficacy both in vitro and in vivo. Mechanistically, PTEN directly binds to and dephosphorylates the C terminus of the catalytic subunit of protein phosphatase 2A (PP2Ac) to increase its enzymatic activity, which further dephosphorylates deoxycytidine kinase (DCK) at Ser⁷⁴ to diminish gemcitabine efficacy. Therefore, PTEN deficiency and high phosphorylation of DCK predict a better response to gemcitabine-based chemotherapy in CCA. We speculate that the combination of PP2A inhibitor and gemcitabine in PTEN-positive tumors could avoid the resistance of gemcitabine, which would benefit a large population of patients with cancer receiving gemcitabine or other nucleoside analogs.

Barriers and opportunities for gemcitabine in pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDA) has become one of the leading causes of cancer-related deaths across the world. A lack of durable responses to standard-of-care chemotherapies renders its treatment particularly challenging and largely contributes to the devastating outcome. Gemcitabine, a pyrimidine antimetabolite, is a cornerstone in PDA treatment. Given the importance of gemcitabine in PDA therapy, extensive efforts are focusing on exploring mechanisms by which cancer cells evade gemcitabine cytotoxicity, but strategies to overcome them have not been translated into patient care. Here, we will introduce the standard treatment paradigm for patients with PDA, highlight mechanisms of gemcitabine action, elucidate gemcitabine resistance mechanisms, and discuss promising strategies to circumvent them.

Potential role of CMPK1, SLC29A1, and TLE4 polymorphisms in gemcitabine-based chemotherapy in HER2-negative metastatic breast cancer patients: pharmacogenetic study results from the prospective randomized phase II study of eribulin plus gemcitabine versus paclitaxel plus gemcitabine (KCSG-BR-13-11)

Background

In this study, we evaluated the association between genetic polymorphisms of 23 genes associated with gemcitabine metabolism and the clinical efficacy of gemcitabine in breast cancer patients.

Patients and methods

This prospective, pharmacogenetic study was conducted in cooperation with a phase II clinical trial. A total of 103 genetic polymorphisms of the 23 genes involved in gemcitabine transport and metabolism were selected for genotyping. The associations of genetic polymorphisms with overall survival, progression-free survival (PFS), and 6-month PFS were analyzed.

Results

A total of 91 breast cancer patients were enrolled in this study. In terms of 6-month PFS, rs1044457 in CMPK1 was the most significant genetic polymorphism [55.9% for CT and TT and 78.9% for CC, P < 0.001, hazard ratio (HR): 4.444, 95% confidence interval (CI): 1.905-10.363]. For the rs693955 in SLC29A1, the median duration of PFS was 5.4 months for AA and 10.5 months for CA and CC (P = 0.002, HR: 3.704, 95% CI: 1.615-8.497). For the rs2807312 in TLE4, the median duration of PFS was 5.7 months for TT and 10.4 months for CT and CC (P = 0.005, HR: 4.948, 95% CI: 1.612-15.190). In survival analysis with a multi-gene model, the TT genotype of rs2807312 had the worst PFS regardless of other genetic polymorphisms, whereas the CA genotype of rs693955 or the CT genotype of rs2807312 without the AA genotype of rs693955 had the best PFS compared with those of other genetic groups (P < 0.001).

Conclusions

Genetic polymorphisms of rs1044457 in CMPK1, rs693955 in SLC29A1, and rs2807312 in TLE4 were significantly associated with the 6-month PFS rate and/or the duration of PFS. Further studies with a larger sample size and expression study would be helpful to validate the association of genetic polymorphisms and clinical efficacy of gemcitabine.

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This is the largest pharmacogenetic study of gemcitabine-based breast cancer treatment in a prospective clinical trial.

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Several genetic polymorphisms in CMPK1, SLC29A1, and TLE4 were associated with 6-month PFS rate and the duration of PFS.

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The result of this study may contribute to the personalized treatment of breast cancer.

Roles for hENT1 and dCK in gemcitabine sensitivity and malignancy of meningioma

Background

High-grade meningiomas are aggressive tumors with high morbidity and mortality rates that frequently recur even after surgery and adjuvant radiotherapy. However, limited information is currently available on the biology of these tumors, and no alternative adjuvant treatment options exist. Although we previously demonstrated that high-grade meningioma cells were highly sensitive to gemcitabine in vitro and in vivo, the underlying molecular mechanisms remain unknown.

Methods

We examined the roles of hENT1 (human equilibrative nucleoside transporter 1) and dCK (deoxycytidine kinase) in the gemcitabine sensitivity and growth of meningioma cells in vitro. Tissue samples from meningiomas (26 WHO grade I and 21 WHO grade II/III meningiomas) were immunohistochemically analyzed for hENT1 and dCK as well as for Ki-67 as a marker of proliferative activity.

Results

hENT1 and dCK, which play critical roles in the intracellular transport and activation of gemcitabine, respectively, were responsible for the high gemcitabine sensitivity of high-grade meningioma cells and were strongly expressed in high-grade meningiomas. hENT1 expression was required for the proliferation and survival of high-grade meningioma cells and dCK expression. Furthermore, high hENT1 and dCK expression levels correlated with stronger tumor cell proliferative activity and shorter survival in meningioma patients.

Conclusions

The present results suggest that hENT1 is a key molecular factor influencing the growth capacity and gemcitabine sensitivity of meningioma cells and also that hENT1, together with dCK, may be a viable prognostic marker for meningioma patients as well as a predictive marker of their responses to gemcitabine.

Human equilibrative nucleoside transporter-1 and deoxycytidine kinase can predict gemcitabine effectiveness in Egyptian patients with Hepatocellular carcinoma

Background

Several biomarkers of gemcitabine effectiveness have been studied in cancers, but less so in hepatocellular carcinoma (HCC), which is identified as the fifth most common cancer worldwide. Investigation of human equilibrative nucleoside transporter‐1 (HENT‐1) and deoxycytidine kinase (DCK), genes involved in gemcitabine uptake and metabolism, can be beneficial in the selection of potential cancer patients who could be responding to the treatment.

Aim

To study HENT‐1 and DCK gene expression in HCC patients with different protocols of treatment.

Methods

Using real‐time PCR, we analyzed expression levels of HENT‐1 and DCK genes from peripheral blood samples of 109 patients (20 controls & 89 HCC patients) between March 2015 and March 2017. All the 89 HCC patients received the antioxidants selenium (Se) and vitamin E (Vit.E) either alone (45 patients) or in combination with gemcitabine (24 patients) or radiofrequency ablation (RFA) (20 patients).

Results

There was a significant increase in HENT‐1 expression levels in HCC patients treated with Se and Vit.E alone as compared to controls (P ˂ .0001), while there was no significant difference between HCC patients treated with gemcitabine or RFA as compared to controls. In contrast, expression of DCK was significantly increased in all groups of HCC patients as compared to controls (P ˂ .0001).

Conclusions

HENT‐1 and DCK mRNA expressions are important markers of HCC and for GEM effect and GEM sensitivity in patients with HCC. This could be beneficial in the selection of HCC patients sensitive to gemcitabine to avoid subjecting resistant patients to unnecessary chemotherapy.

Human equilibrative nucleoside transporter-1 (hENT1) and ribonucleotide reductase regulatory subunit M1 (RRM1) expression; do they have survival impact to pancreatic cancer?

Backgrounds/Aims

Gemcitabine is still one of adjuvant options in chemotherapeutic agent for pancreatic ductal adenocarcinoma (PDAC). Integral membrane transporter protein and intracellular enzymes including human equilibrative nucleoside transporter 1 (hENT1), deoxycytidine kinase (dCK), ribonucleotide reductase (RR) M1, and M2 are known as important factors for chemosensitivity of gemcitabine. We aimed to investigate the correlation between these key molecules and 5-year actual survival in PDAC patients.

Methods

The expression of intratumoral hENT1, dCK, RRM1, and RRM2 was assessed immunohistochemically in 160 PDAC patients underwent surgical resection. Association between clininopathologic factors, immunohistochemical results, and overall survival were analyzed.

Results

Adjuvant chemotherapy including concurrent chemoradiotherapy was not associated with overall survival (HR, 0.92; 95% CI, 0.65-1.31; p=0.658). High hENT1 expression group did not show statistical survival difference, compared with all others (HR, 1.16; 95% CI, 0.82-1.65, p=0.396). Gemcitabine therapy and high hENT1 group was compared with all other patients, and no difference in overall survival was identified (HR, 0.99; 95% CI, 0.68-1.42; p=0.940). And, gemcitabine therapy and high hENT1 group did not differ statistically from gemcitabine therapy and low hENT1 expression (HR, 0.92; 95% CI, 0.55-1.56; p=0.764). The intensity of dCK, RRM1, and RRM2 expression was not associated with overall survival (p=0.413, p=0.138 and p=0.061) in univariate analysis.

Conclusions

The expression of hENT1, dCK, RRM1 and RRM2 may not be associated with overall survival for patients with pancreatic cancer on gemcitabine adjuvant therapy. These proteins and other factors that may interact with or confound these results should be investigated in the near future.

Role of Damage DNA-Binding Protein 1 in Pancreatic Cancer Progression and Chemoresistance

Damaged DNA-binding protein 1 (DDB1) recruits nucleotide excision pathway proteins to form the UV-damaged DNA-binding protein complex and is required for DNA repair. DDB1 was reported to participate in apoptosis and chemoresistance regulation in several cancers. However, little is known about the function of DDB1 in pancreatic adenocarcinoma (PDAC). In this study, we reported that DDB1 functions as a tumor-promoting factor in PDAC by regulating cancer cell proliferation, epithelial-mesenchymal transition (EMT) and chemoresistance. Compared to normal pancreatic tissues, PDAC tissues had high expression levels of DDB1, and this high expression was positively correlated with poor prognosis. Furthermore, reductions in cell proliferation and EMT were observed in DDB1-deficient PDAC cell lines. Intriguingly, we also found that abrogation of DDB1 expression increased PDAC cell sensitivity to gemcitabine (GEM). Mechanistically, DDB1 knockdown was associated with an increase in deoxycytidine kinase expression in vivo and in vitro. In summary, our work demonstrated that DDB1 promotes PDAC progression and chemoresistance and may serve as a potential predictive marker and therapeutic target for PDAC treatment.

New era for pancreatic endoscopic ultrasound: From imaging to molecular pathology of pancreatic cancer

With recent advances in molecular pathology and the development of new chemotherapy regimens, the knowledge of the molecular alterations of pancreatic ductal adenocarcinoma (PDAC) is becoming appealing for stratifying patients for prognosis and response to a defined treatment. Archival formalin-fixed, paraffin-embedded samples are a useful source of genomic deoxyribonucleic acid; nevertheless, most studies employed formalin-fixed, paraffin-embedded samples deriving from surgical specimens, which are therefore representative of <20% of PDAC patients. Indeed, the development of a reliable methodology for endoscopic ultrasound-guided tissue acquisition, stabilization, and analysis is crucial for the development of molecular markers for clinical use in order to achieve “personalized medicine”. With the development of new needles, this technique is able to retrieve a high quantity and quality of PDAC tissue that can be used not only for diagnosis but also for mutational and transcriptome evaluations and for the development of primary cell or tissue cultures. In the present editorial, we discuss the current knowledge regarding the use of endoscopic ultrasound as a tool to obtain samples for molecular analyses, its possible pitfalls, and its use for the development of disease models such as xenografts or organoids.

Concentration changes in gemcitabine and its metabolites after hyperthermia in pancreatic cancer cells assessed using RP-HPLC

Background

Gemcitabine (2′,2′-difluoro-2′-deoxycytidine;dFdC) is a first-line chemotherapy drug for pancreatic cancer. Recently, a synergistic anti-tumor treatment of dFdC and hyperthermia has achieved good clinical results, but there are few reports on the molecular mechanism influenced by hyperthermia. This study is an initial exploration of the effects of hyperthermia on changes in the concentration of dFdC and its metabolites in pancreatic cancer cells. The aim is to provide a theoretical basis for clinical detection and pharmacokinetic research.

Methods

PANC-1 cells at logarithmic growth phase were used as the experimental object. The MTT assay was performed to determine the half maximal inhibitory concentration (IC₅₀) of dFdC. After PANC-1 cells were cultured in DMEM medium containing IC₅₀dFdC and treated with hyperthermia at 41 °C or 43 °C, changes in the concentration of dFdC, 2′,2′-difluorodeoxyuridine (dFdU) and difluorodeoxycytidine triphosphate (dFdCTP) in the cells were tested using an optimized reverse phase high-performance liquid chromatography (RP-HPLC) protocol.

Results

We found that 41 °C and 43 °Chyperthermia gave rise to a decrease in dFdC and dFdU content. At 41 °C, the levels respectively fell to 9.28 and 30.93% of the baseline, and at 43 °C, to 24.76 and 57.80%, respectively. The dFdCTP content increased by 21.82% at 41 °C and 42.42% at 43 °C.

Conclusion

The two heat treatments could alter the mechanism of dFdC metabolism in PANC-1 cells. The effect of 43 °C hyperthermia is more significant. Our observations may be instrumental to explaining the higher anti-tumor efficacy of this combination therapy.

Molecular and cellular mechanisms of chemoresistance in pancreatic cancer

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the most chemoresistant cancers, and current therapies targeting cancer-associated molecular pathways have not given satisfactory results, owing in part to rapid upregulation of alternative compensatory pathways. Most of the available treatments are palliative, focussing on improving the quality of life. At present, available options are surgery, embolization, radiation, chemotherapy, immunotherapy and use of other more targeted drugs. In this review, we describe the cellular and molecular effects of current chemotherapy drugs such as gemcitabine, FOLFIRINOX (5-fluorouracil [5-FU], oxaliplatin, irinotecan, and leucovorin) and ABRAXANE (nab-Paclitaxel), which have shown a survival benefit, although modest, for pancreatic cancer patients. Nevertheless, gemcitabine remains the standard first-line option for advanced-stage pancreatic cancer patients and, as resistance to the drug has attracted an increasing scientific interest, we deliberate on the main intracellular processes and proteins vital in acquired chemoresistance to gemcitabine. Lastly, our review examines various microenvironmental factors capable of instigating PDAC to develop resistance to chemotherapeutic drugs.

The Role of Platelet-Derived ADP and ATP in Promoting Pancreatic Cancer Cell Survival and Gemcitabine Resistance

Platelets have been demonstrated to be vital in cancer epithelial-mesenchymal transition (EMT), an important step in metastasis. Markers of EMT are associated with chemotherapy resistance. However, the association between the development of chemoresistance, EMT, and the contribution of platelets to the process, is still unclear. Here we report that platelets regulate the expression of (1) human equilibrative nucleoside transporter 1 (hENT1) and (2) cytidine deaminase (CDD), markers of gemcitabine resistance in pancreatic cancer. Human ENT1 (hENT1) is known to enable cellular uptake of gemcitabine while CDD deactivates gemcitabine. Knockdown experiments demonstrate that Slug, a mesenchymal transcriptional factor known to be upregulated during EMT, regulates the expression of hENT1 and CDD. Furthermore, we demonstrate that platelet-derived ADP and ATP regulate Slug and CDD expression in pancreatic cancer cells. Finally, we demonstrate that pancreatic cancer cells express the purinergic receptor P2Y₁₂, an ADP receptor found mainly on platelets. Thus ticagrelor, a P2Y₁₂ inhibitor, was used to examine the potential therapeutic effect of an ADP receptor antagonist on cancer cells. Our data indicate that ticagrelor negated the survival signals initiated in cancer cells by platelet-derived ADP and ATP. In conclusion, our results demonstrate a novel role of platelets in modulating chemoresistance in pancreatic cancer. Moreover, we propose ADP/ATP receptors as additional potential drug targets for treatment of pancreatic cancer.

DCK expression, a potential predictive biomarker in the adjuvant gemcitabine chemotherapy for biliary tract cancer after surgical resection: results from a phase II study

The role of adjuvant therapy following resection of biliary tract cancer (BTC) remains unclear. We therefore evaluated the feasibility and toxicity of adjuvant gemcitabine in patients with BTC. This clinical phase II trial was an open-label, single center, single-arm study. Within 8 weeks after gross complete resection of BTC, patients were started on intravenous infusions of gemcitabine 1000 mg/m² over 30 min on days 1, 8, and 15 of every 28-day cycle. Intratumoral expression of cytidine deaminase (CDA), human equilibrative transporter-1 (hENT1), deoxycytidine kinase (dCK) and ribonucleotide reductase subunit 1 (RRM1) was measured by immunohistochemistry. This study enrolled 72 patients with BTC (26 with gallbladder cancer, 33 with extrahepatic cholangiocarcinoma, and 13 with intrahepatic cholangiocarcinoma). The 2-year recurrence-free survival (RFS) rate was 43% (95% CI, 33–57%). Multivariable analysis showed that DCK expression, vascular invasion, and lymph node metastasis were significantly associated with RFS. Twenty-one (31.8%) were positive for DCK immunoreactivity. The median RFS was 34.95 months for DCK-positive patients, compared with 11.41 months for DCK-negative patients. Although the primary hypothesis of this study, defined as a 2-year RFS of 60%, was not met, intratumoral DCK expression was significantly associated with RFS in patients with resected BTC treated with postoperative gemcitabine chemotherapy. Future randomized controlled trials are warranted.

Prognostic Implications of Expression Profiling for Gemcitabine-Related Genes (hENT1, dCK, RRM1, RRM2) in Patients With Resectable Pancreatic Adenocarcinoma Receiving Adjuvant Chemotherapy

OBJECTIVES

The aim of this study was to examine the relevance of expression profiling of 4 genes involved in the action of gemcitabine among patients with pancreatic ductal-cell adenocarcinoma (PDAC).

METHODS

A group of 100 patients who underwent pancreatic resections for PDAC and received adjuvant chemotherapy with gemcitabine between 2007 and 2010 was identified. Expression of mRNAs for human equilibrative nucleoside transporter 1 (hENT1), ribonucleotide reductase subunits (RRM1, RRM2), and deoxycytidine kinase (dCK) was examined by quantitative real-time polymerase chain reaction, normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and dichotomized into groups of low and moderate/high expression levels grouped by tertiles.

RESULTS

Significantly better median survival times were found for high/moderate expression levels of hENT1 (27.9 vs 12.4 months, P = 0.001) and dCK (19.7 vs 10.5 months, P = 0.003), as well as low expression of RRM1 (23.4 vs 11.4 months, P = 0.027). A Cox proportional hazards model identified low expression of hENT1 (hazard ratio [HR], 3.38; 95% confidence intervals [CI], 2.28-10.50) and dCK (HR, 2.24; 95% CI, 1.63-3.39), and high/moderate levels of RRM1 (HR, 1.65; 95% CI, 1.23-2.45) as negative prognostic factors.

CONCLUSIONS

Expression of hENT, RRM1, and dCK genes provides important prognostic information for PDAC patients treated with adjuvant gemcitabine.

Vasohibin 2 reduces chemosensitivity to gemcitabine in pancreatic cancer cells via Jun proto-oncogene dependent transactivation of ribonucleotide reductase regulatory subunit M2

Background

Vasohibin 2 (VASH2) has previously been identified as an agiogenenic factor and a cancer related protein. Here we investigated the association of VASH2 expression and chemoresistance in pancreatic cancer.

Methods

Immunohistochemical staining for VASH2 was performed on 102 human pancreatic cancer samples. Pancreatic cancer cell line models exhibiting overexpression or knockdown of VASH2 were generated. Gene expression analyses were carried out to determine genes differentially regulated by VASH2. Putative transcription factors that are downstream mediators of gene expression regulated by VASH2 were queried bioinformatically. Dual-luciferase reporter assays and ChIP assays were performed to confirm transactivation of target genes following VASH2 overexpression or knockdown.

Results

VASH2 protein expression was higher in human pancreatic cancer than in paired adjacent tissues and elevated VASH2 levels were associated with gemcitabine chemoresistance. In cell line models of pancreatic cancer, VASH2 expression induced gemcitabine chemoresistance in vitro and in vivo. It was discovered that expression of ribonucleotide reductase regulatory subunit M2 (RRM2) is regulated by VASH2; immunohistochemical analysis demonstrated a positive association of VASH2 expression and RRM2 expression in human pancreatic cancer tissues. Bioinformatics analyses revealed that induction of the Jun proto-oncogene (JUN) by VASH2 is responsible for upregulation of RRM2 expression; this JUN-dependent regulation of RRM2 by VASH2 was confirmed by chromatin immunoprecipitation and dual luciferase reporter assays, which demonstrated that JUN directly binds with the RRM2 promoter to activate transcription.

Conclusions

These data suggest that VASH2 reduces the chemosensitivity to gemcitabine in pancreatic cancer cells via JUN-dependent transactivation of RRM2.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0619-6) contains supplementary material, which is available to authorized users.

New frontiers in the treatment of colorectal cancer: Autophagy and the unfolded protein response as promising targets

Colorectal cancer (CRC), despite numerous therapeutic and screening attempts, still remains a major life-threatening malignancy. CRC etiology entails both genetic and environmental factors. Macroautophagy/autophagy and the unfolded protein response (UPR) are fundamental mechanisms involved in the regulation of cellular responses to environmental and genetic stresses. Both pathways are interconnected and regulate cellular responses to apoptotic stimuli. In this review, we address the epidemiology and risk factors of CRC, including genetic mutations leading to the occurrence of the disease. Next, we discuss mutations of genes related to autophagy and the UPR in CRC. Then, we discuss how autophagy and the UPR are involved in the regulation of CRC and how they associate with obesity and inflammatory responses in CRC. Finally, we provide perspectives for the modulation of autophagy and the UPR as new therapeutic options for CRC treatment.

Precision Medicine and Pancreatic Cancer: A Gemcitabine Pathway Approach

OBJECTIVES

There is a need for validated predictive markers of gemcitabine response to guide precision medicine treatment in pancreatic cancer. We previously validated human equilibrative nucleoside transporter 1 as a predictive marker of gemcitabine treatment response using Radiation Therapy Oncology Group 9704. Controversy exists about the predictive value of gemcitabine metabolism pathway biomarkers: deoxycytidine kinase (DCK), ribonucleotide reductase 1 (RRM1), RRM2, and p53R2.

METHODS

Radiation Therapy Oncology Group 9704 prospectively randomized 538 patients after pancreatic resection to receive either 5-fluorouracil or gemcitabine. Tumor DCK, RRM1, RRM2, and p53R protein expressions were analyzed using a tissue microarray and immunohistochemistry and correlated with treatment outcome (overall survival and disease-free survival) by unconditional logistic regression analysis.

RESULTS

There were 229 patients eligible for analysis from both the 5-fluorouracil and gemcitabine arms. Only RRM2 protein expression, and not DCK, RRM1, or p53R2 protein expression, was associated with survival in the gemcitabine treatment arm.

CONCLUSIONS

Despite limited data from other nonrandomized treatment data, our data do not support the predictive value of DCK, RRM1, or p53R2. Efforts should focus on human equilibrative nucleoside transporter 1 and possibly RRM2 as valid predictive markers of the treatment response of gemcitabine in pancreatic cancer.

Drug metabolism and pancreatic cancer

Pancreatic cancer remains a fatal disease in the majority of patients. The era of personalized medicine is upon us: customizing therapy according to each patient's individual cancer. Potentially, therapy can be targeted at individuals who would most likely have a favorable response, making it more efficacious and cost effective. This is particularly relevant for pancreatic cancer, which currently portends a very poor prognosis. However, there is much to be done in this field, and more studies are needed to bring this concept to reality.

dCK Expression and Gene Polymorphism With Gemcitabine Chemosensitivity in Patients With Pancreatic Ductal Adenocarcinoma: A Strobe-Compliant Observational Study

The aim of this study was to investigate the relationship of deoxycytidine kinase (dCK) protein expression and gene single-nucleotide polymorphisms to gemcitabine chemosensitivity in patients with pancreatic ductal adenocarcinoma (PDAC).In total, 54 patients with resectable PDAC, who received postoperative gemcitabine-based therapy, were enrolled in this study, from January 2011 to April 2013. The dCK protein expression was measured retrospectively by immunohistochemistry. Furthermore, 5 single-nucleotide polymorphisms (C1205T, A9846G, A70G, C356G, and C364T) of the dCK gene were detected in PDAC cells by PCR amplification and sequencing.The dCK protein expression was found to be negatively correlated with age (P = 0.006), but correlated positively with overall survival (OS) (P = 0.000) and disease-free survival (DFS) (P = 0.003). The A9846G AA genotype in the dCK gene was significantly associated with reduced mortality compared with AG and GG genotypes. The OS and DFS were longer in patients with the A9846G AA genotype than the AG and GG genotypes. In univariate and multivariate analyses, we found that the dCK protein expression and A9846G genotype were significant predictors of both OS and DFS.Our study suggests that the dCK protein expression and A9846G genotype may act as prognostic biomarkers in identifying patients who are likely to benefit from postoperative gemcitabine therapy in PDAC.

International Association of Pancreatology (IAP)/European Pancreatic Club (EPC) consensus review of guidelines for the treatment of pancreatic cancer

BACKGROUND

Pancreatic cancer is one of the most devastating diseases with an extremely high mortality. Medical organizations and scientific societies have published a number of guidelines to address active treatment of pancreatic cancer. The aim of this consensus review was to identify where there is agreement or disagreement among the existing guidelines and to help define the gaps for future studies.

METHODS

A panel of expert pancreatologists gathered at the 46th European Pancreatic Club Meeting combined with the 18th International Association of Pancreatology Meeting and collaborated on critical reviews of eight English language guidelines for the clinical management of pancreatic cancer. Clinical questions (CQs) of interest were proposed by specialists in each of nine areas. The recommendations for the CQs in existing guidelines, as well as the evidence on which these were based, were reviewed and compared. The evidence was graded as sufficient, mediocre or poor/absent.

RESULTS

Only 4 of the 36 CQs, had sufficient evidence for agreement. There was also agreement in five additional CQs despite the lack of sufficient evidence. In 22 CQs, there was disagreement regardless of the presence or absence of evidence. There were five CQs that were not addressed adequately by existing guidelines.

CONCLUSION

The existing guidelines provide both evidence- and consensus-based recommendations. There is also considerable disagreement about the recommendations in part due to the lack of high level evidence. Improving the clinical management of patients with pancreatic cancer, will require continuing efforts to undertake research that will provide sufficient evidence to allow agreement.

MicroRNA-100 and microRNA-21 as markers of survival and chemotherapy response in pancreatic ductal adenocarcinoma UICC stage II

Background

Pancreatic ductal adenocarcinoma (PDAC) remains a highly chemoresistant tumor entity for which no reliable molecular targets exist to predict or influence the success of chemotherapy. Recently, we identified a panel of microRNAs associated with induced gemcitabine chemoresistance in human PDAC cell lines. This clinical study evaluates these microRNAs and associated molecular markers as prognostic markers of outcome in 98 PDAC patients Union Internationale Contre le Cancer (UICC) stage II undergoing curative surgery with adjuvant gemcitabine chemotherapy. The primary end points of this study are recurrence-free survival and overall survival.

Results

Poor response to chemotherapy was significantly correlated to overexpression of microRNA-21 (p = 0.029), microRNA-99a (p = 0.037), microRNA-100 (p = 0.028), and microRNA-210 (p = 0.021) in tissue samples of PDAC patients UICC stage II. Upregulation of these microRNAs was associated with a significantly shorter overall survival and recurrence-free survival (p < 0.05). Overexpression of phosphatase and tensin homolog (PTEN) (p = 0.039) and low expression of multidrug resistance (MDR)-1 (p = 0.043) and breast cancer resistance protein (BCRP)-1 (p = 0.038) were significantly correlated to improved response to adjuvant chemotherapy. Adjuvant gemcitabine treatment (p < 0.0001) and low tumor grading (p = 0.047) were correlated to better outcome. MicroRNA-100, microRNA-21, and its targets PTEN and MDR-1 were independent factors of survival in multivariate analysis.

Conclusions

Multivariate survival analyses identified microRNA-21 and microRNA-100 as unfavorable prognostic factors in resected and adjuvant treated PDAC UICC stage II patients.

Long-term survivors after pancreatectomy for cancer: the TNM classification is outdated

BACKGROUND

According to knowledge, patients with resectable pancreatic adenocarcinoma (PA) should receive adjuvant gemcitabine-based chemotherapy. Thus, the tumour node metastasis (TNM) classification is not used to determine post-operative treatment but rather only to establish patient prognosis. However, the TNM classification does not include strong factors influencing survival, such as perineural invasion or margin status. This study compared the survival of patients with very similar tumours.

METHODS

From 1997 to 2007, 118 patients underwent pancreatectomy for PA. Twenty-six patients (22%) had long-term survival (>5 years; LTS group). According to the major prognostic factors of PA, we matched (1:1) patients in the LTS group with patients who did not have long-term survival (<5 years; control group).

RESULTS

Surprisingly, we did not have any difficulty identifying patients to include in the control group. Consequently, no differences were noted between patients of the LTS group when compared with patients of the control group according to major prognostic factors and the TNM classification. Three patients (12%) in the LTS group had positive margin status, and two patients (8%) had positive lymph node status. Unsurprisingly, the median survival for the control group versus the LTS group was 16 months versus not reached (P < 0.01).

CONCLUSION

The lack of difficulty in matching the two groups confirmed that patients of the LTS group did not have an exclusive tumour pattern. TNM classification is outdated because it did not influence adjuvant therapies and did not include two crucial factors: tumour biology and tumour response to chemo/radio therapies.

Management of metastatic pancreatic cancer: Current treatment options and potential new therapeutic targets

Pancreatic ductal adenocarcinoma is a malignancy with a poor prognosis, with the majority of patients diagnosed with advanced disease on presentation. Treatment options remain limited with little progress over the last 40 years. This review will focus on the current management of metastatic pancreatic ductal adenocarcinoma, with a discussion of new and future treatment strategies based on an improved understanding of tumour biology and mechanisms of pathogenesis.

Novel developments in the use of antimetabolites

Antimetabolites are the most widely used and most efficacious group of anticancer drugs. Antimetabolites are also the oldest rationally designed anticancer drugs, targeted against RNA and DNA, and can, therefore, be considered as the first generation of targeted drugs. Unfortunately, resistance often develops, leading to the design of new antimetabolites, which either have a novel mechanism of action, bypass resistance or in combination enhance the effect of other drugs, such as another antimetabolite, other DNA, or protein kinase targeted anticancer drugs. Several novel antimetabolites are in clinical development. The cytidine-analog fluorocyclopentenylcytosine (RX-3117) is active in gemcitabine-resistant tumors and is activated by uridine-cytidine-kinase, can be incorporated into RNA and DNA and can downregulate DNA-methyltransferase-1. TAS-114 is a new generation dUTPase inhibitor. dUTPase normally prevents incorporation of dUTP and of the 5FU-nucleotide FdUTP into DNA. However, inhibition of dUTPase will enhance their incorporation, thereby increasing thymine-less cell-death. The formulation TAS-102 (trifluorothymidine and thymidine-phosphorylase-inhibitor) acts by incorporation into DNA and has shown efficacy in tumors progressing on 5FU therapy. Gemcitabine and cytarabine prodrugs were tested in model systems and have entered clinical evaluation. The elaidic-acid prodrugs of gemcitabine (CP-4126, CO101) and cytarabine (elacytarabine) failed in randomized Phase III studies. Two other gemcitabine prodrugs LY2334737 (gemcitabine with a valproic acid at the 5'-position) and NUC1031 (a 5'-arylphosphoamidate prodrug, with a side-chain at the 5'-phosphate) are in early clinical development. In summary, several novel antimetabolites show promise in clinical development, either because of a novel mechanism of action, or clever combination or by innovative prodrug design.

Biomarkers for pancreatic cancer: Recent achievements in proteomics and genomics through classical and multivariate statistical methods

Pancreatic cancer (PC) is one of the most aggressive and lethal neoplastic diseases. A valid alternative to the usual invasive diagnostic tools would certainly be the determination of biomarkers in peripheral fluids to provide less invasive tools for early diagnosis. Nowadays, biomarkers are generally investigated mainly in peripheral blood and tissues through high-throughput omics techniques comparing control vs pathological samples. The results can be evaluated by two main strategies: (1) classical methods in which the identification of significant biomarkers is accomplished by monovariate statistical tests where each biomarker is considered as independent from the others; and (2) multivariate methods, taking into consideration the correlations existing among the biomarkers themselves. This last approach is very powerful since it allows the identification of pools of biomarkers with diagnostic and prognostic performances which are superior to single markers in terms of sensitivity, specificity and robustness. Multivariate techniques are usually applied with variable selection procedures to provide a restricted set of biomarkers with the best predictive ability; however, standard selection methods are usually aimed at the identification of the smallest set of variables with the best predictive ability and exhaustivity is usually neglected. The exhaustive search for biomarkers is instead an important alternative to standard variable selection since it can provide information about the etiology of the pathology by producing a comprehensive set of markers. In this review, the most recent applications of the omics techniques (proteomics, genomics and metabolomics) to the identification of exploratory biomarkers for PC will be presented with particular regard to the statistical methods adopted for their identification. The basic theory related to classical and multivariate methods for identification of biomarkers is presented and then, the most recent applications in this field are discussed.

Do hENT1 and RRM1 predict the clinical benefit of gemcitabine in pancreatic cancer?

Gemcitabine is a nucleoside analog that is indicated in the treatment of pancreatic cancer. In order to provide a better use of this drug, the search for immunohistological markers is a hot topic in the field of pancreatic cancer. In particular, the use of nucleoside transporter hENT1 and the intracellular target of gemcitabine RRM1 are current subjects for discussion. We have analyzed the majority of studies of hENT1 and RRM1 on pancreatic cancer, and will discuss the further directions that might be followed in order to integrate these proteins in routine clinical practice. The data that is currently available would benefit from the completion of well-designed randomized trials in order to confirm the clinical value of hENT1 and RRM1 as biomarkers in pancreatic cancer patients.

A meta-analysis of gemcitabine biomarkers in patients with pancreaticobiliary cancers

OBJECTIVES

The objective of this study was to summarize all clinical studies evaluating the prognostic role of gemcitabine (GEM) metabolic genes in pancreaticobiliary (PB) cancer patients receiving GEM therapy in the neoadjuvant, adjuvant, or palliative settings.

METHODS

Meta-analyses were performed to calculate the pooled hazard ratios for each gene by each clinical outcome (overall survival [OS], disease-free survival [DFS], and progression-free survival) using a random-effects approach.

RESULTS

The search strategy identified 16 eligible studies, composed of 632 PB patients total, with moderate quality. Compared with low expression, pooled hazard ratios for OS of hENT1, dCK, RRM1, RRM2, and DPD were 0.37 (95% confidence interval [CI], 0.28-0.47), 0.40 (95% CI, 0.20-0.80), 2.21 (95% CI, 1.12-4.36), 2.13 (95% CI, 1.00-4.52), and 1.91 (95% CI, 1.16-3.17), respectively. A similar trend was observed for each of these biomarkers in DFS and progression-free survival prognostication. Subgroup analyses for hENT1 showed a comparable survival correlation in the adjuvant and palliative settings.

CONCLUSIONS

High expression of hENT1 in PB cancer patients receiving GEM-based adjuvant therapy is associated with improved OS and DFS and may be the best examined prognostic marker to date. Evidence for other biomarkers is limited by a small number of publications investigating these markers.

Metabolomics strategy reveals subpopulation of liposarcomas sensitive to gemcitabine treatment

Unlike many cancers that exhibit glycolytic metabolism, high-grade liposarcomas often exhibit low 2[18F]fluoro-2-deoxy-D-glucose uptake by positron emission tomography (PET), despite rapid tumor growth. Here, we used liquid chromatography tandem mass spectrometry to identify carbon sources taken up by liposarcoma cell lines derived from xenograft tumors in patients. Interestingly, we found that liposarcoma cell lines consume nucleosides from culture media, suggesting nucleoside salvage pathway activity. The nucleoside salvage pathway is dependent on deoxycytidine kinase (dCK) and can be imaged in vivo by PET with 1-(2'-deoxy-2'-[18F]fluoroarabinofuranosyl) cytosine (FAC). We found that liposarcoma cell lines and xenograft tumors exhibit dCK activity and dCK-dependent FAC uptake in vitro and in vivo. In addition, liposarcoma cell lines and xenograft tumors are sensitive to treatment with the nucleoside analogue prodrug gemcitabine, and gemcitabine sensitivity is dependent on dCK expression. Elevated dCK activity is evident in 7 of 68 clinical liposarcoma samples analyzed. These data suggest that a subpopulation of liposarcoma patients have tumors with nucleoside salvage pathway activity that can be identified noninvasively using [18F]-FAC-PET and targeted using gemcitabine.

SIGNIFICANCE

Patients with high-grade liposarcoma have poor prognoses and often fail to respond to chemotherapy. This report identifies elevated nucleoside salvage activity in a subset of liposarcomas that are identifiable using noninvasive PET imaging with FAC and that are sensitive to gemcitabine. Thus, we suggest a new treatment paradigm for liposarcoma patients that uses [18F]-FAC-PET in the clinic to delineate gemcitabine responders from nonresponders.

Adjuvant pharmacotherapy in the management of elderly patients with pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth or fifth leading cause of death from cancer in Western industrialized countries. Surgical resection is the only chance of cure, but only 15-20 % of cases are potentially resectable at presentation, and despite complete resection, the overall prognosis remains relatively poor. Adjuvant therapy has modestly improved cure rates. The majority of patients with pancreatic cancer are over the age of 65 years. But this age group is underrepresented within clinical trials, and it is unknown whether older patients achieve similar results to younger ones in terms of survival and treatment tolerance. In addition, there are no clinical trials dedicated to the elderly. Retrospective studies coming from the non-resectable setting provide some understanding on outcomes in older patients with PDAC. To date, we can reasonably argue that selected elderly patients with PDAC can benefit from curative surgery and postoperative chemotherapy as do their younger counterparts, without a significant increase in morbidity and mortality. Gemcitabine should be preferred to 5-fluorouracil on the basis of a better risk-benefit balance.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Prognostic predictive values of gemcitabine sensitivity-related gene products for unresectable or recurrent biliary tract cancer treated with gemcitabine alone

BACKGROUND

Gemcitabine is a pyrimidine nucleoside analog that is a commonly used chemotherapeutic agent for unresectable or recurrent biliary tract cancer (BTC). Several molecules involved in gemcitabine metabolism, including human equilibrative nucleoside transporter (hENT1), deoxycytidine kinase (dCK), and ribonucleotide reductase subunit M1 (RRM1), have been investigated as predictive biomarkers of gemcitabine efficacy, mostly in pancreatic cancer. The aim of this study is to clarify which biomarker is the most reliable among hENT1, dCK, and RRM1 to predict survival in patients with advanced BTC treated with gemcitabine alone.

METHODS

The analysis was performed on samples from 28 patients with unresectable or recurrent BTC who were treated with gemcitabine alone as first-line therapy. The starting date of overall survival (OS) and progression-free survival (PFS) was defined as the date of first treatment with gemcitabine. Intratumoral hENT1, dCK, and RRM1 expressions were examined by immunohistochemistry.

RESULTS

The expressions of hENT1, dCK, and RRM1 had no significant relationships with age, gender, primary tumor site, recurrence/unresectable, or histological type. Among the three molecules, only hENT1 expression was a significant factor affecting OS and PFS in univariate analysis; OS was 11.4 months for high hENT1 expression versus 5.7 months for low, P = 0.0057; PFS was 7.7 months for high versus 2.5 months for low, P = 0.0065. Multivariate analyses also identified hENT1 expression as an independent predictive factor for OS.

CONCLUSIONS

hENT1 is the most reliable predictive marker of survival in patients with advanced BTC treated with gemcitabine.

Clinicopathological significance of deoxycytidine kinase expression in esophageal squamous cell carcinoma

Deoxycytidine kinase (dCK) mediates the rate-limiting catabolic step in the activation of gemcitabine. Gemcitabine is a key drug for pancreatic and biliary tract cancer. However, gemcitabine is not widely used for esophageal squamous cell carcinoma (ESCC). In this study, we analyzed the expression of dCK in ESCC and evaluated the possibility of gemcitabine treatment for ESCC. In total, 76 ESCC patients who underwent esophagectomy between 1990 and 2008 were analyzed. dCK expression was analyzed immunohistochemically using tissue microarray and compared to the clinocopathological characteristics of the patients. Results identified 41 patients positive for dCK and 35 patients negative for dCK. A significant association was observed between dCK expression and gender (P=0.01), whereas the remaining factors were not associated with dCK expression. Prognosis of the patients with a high dCK expression was significantly worse than that of the patients with a low dCK expression (P=0.022). Furthermore, dCK expression was an independent prognostic factor regarding cause-specific prognosis (risk ratio, 2.2; P=0.031). In conclustion, the results of the present study suggested that dCK expression is a prognostic factor of the ESCC patients.

Human equilibrative nucleoside transporter 1 and Notch3 can predict gemcitabine effects in patients with unresectable pancreatic cancer

Background:

Pancreatic ductal carcinoma (PDC) is one of the most lethal human carcinomas. Expression patterns of some genes may predict gemcitabine (GEM) treatment efficacy. We examined predictive indicators of survival in GEM-treated patients by quantifying the expression of several genes in pre-treatment endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) samples from patients with PDC.

Methods:

The expressions of human equilibrative nucleoside transporter 1 (hENT1), deoxycitidine kinase, ribonucleoside reductase 1, ribonucleoside reductase 2 and Notch3 in EUS-FNA tissue samples from 71 patients with unresectable PDC were quantified using real-time reverse transcription–polymerase chain reactions and examined for correlations with GEM sensitivity.

Results:

The log-rank test detected no significant differences in overall survival between GEM-treated patients with low and high mRNA levels of all genes examined. However, low Notch3 mRNA expression was significantly associated with longer overall survival in a multivariate analysis for survival (P=0.0094). High hENT1 expression level was significantly associated with a longer time to progression (P=0.039). Interaction tests for GEM administration and hENT1 or Notch3 mRNA expression were statistically significant (P=0.0054 and 0.0047, respectively).

Conclusion:

hENT1 and Notch3 mRNA expressions in EUS-FNA specimens were the key predictive biomarkers of GEM effect and GEM sensitivity in patients with unresectable PDC.

dNTP Supply Gene Expression Patterns after P53 Loss

Loss of the transcription factor p53 implies mRNA losses of target genes such as the p53R2 subunit of human ribonucleotide reductase (RNR). We hypothesized that other genes in the dNTP supply system would compensate for such p53R2 losses and looked for this in our own data and in data of the Gene Expression Omnibus (GEO). We found that the de novo dNTP supply system compensates for p53R2 losses with increases in RNR subunit R1, R2, or both. We also found compensatory increases in cytosolic deoxycytidine kinase (dCK) and thymidine kinase 1 (TK1) and in mitochondrial deoxyguanosine kinase (dGK), all of the salvage dNTP supply system; in contrast, the remaining mitochondrial salvage enzyme thymidine kinase 2 (TK2) decreased with p53 loss. Thus, TK2 may be more dedicated to meeting mitochondrial dNTP demands than dGK which may be more obligated to assist cytosolic dNTP supply in meeting nuclear DNA dNTP demands.

Systemic therapies for pancreatic cancer--the role of pharmacogenetics

Effective systemic treatment of pancreatic cancer remains a major challenge, with progress hampered by drug resistance and treatment related toxicities. Currently available cytotoxic agents as monotherapy or in combination have provided only a modest survival benefit for patients with advanced disease. Disappointing phase III results with gemcitabine-based combinations in patients with advanced pancreatic cancer might be related to poor efficacy of systemic therapies in unselected patients. Future research strategies should prioritize identification of predictive markers through pharmacogenetic investigations. The individualization of patient treatment through pharmacogenetics may help to improve outcome by maximizing efficacy whilst lowering toxicity. This review provides an update on the pharmacogenetics of pancreatic cancer treatment and its influence on treatment benefits and toxicity.

Systemic therapies for pancreatic cancer--the role of pharmacogenetics

Effective systemic treatment of pancreatic cancer remains a major challenge, with progress hampered by drug resistance and treatment related toxicities. Currently available cytotoxic agents as monotherapy or in combination have provided only a modest survival benefit for patients with advanced disease. Disappointing phase III results with gemcitabine-based combinations in patients with advanced pancreatic cancer might be related to poor efficacy of systemic therapies in unselected patients. Future research strategies should prioritize identification of predictive markers through pharmacogenetic investigations. The individualization of patient treatment through pharmacogenetics may help to improve outcome by maximizing efficacy whilst lowering toxicity. This review provides an update on the pharmacogenetics of pancreatic cancer treatment and its influence on treatment benefits and toxicity.

Levels of gemcitabine transport and metabolism proteins predict survival times of patients treated with gemcitabine for pancreatic adenocarcinoma

BACKGROUND & AIMS

Patients who undergo surgery for pancreatic ductal adenocarcinoma (PDAC) frequently receive adjuvant gemcitabine chemotherapy. Key determinants of gemcitabine cytotoxicity include the activities of the human equilibrative nucleoside transporter 1 (hENT1), deoxycytidine kinase (dCK), and ribonucleotide reductase subunit 1 (RRM1). We investigated whether tumor levels of these proteins were associated with efficacy of gemcitabine therapy following surgery.

METHODS

Sequential samples of resected PDACs were retrospectively collected from 434 patients at 5 centers; 142 patients did not receive adjuvant treatment (33%), 243 received adjuvant gemcitabine-based regimens (56%), and 49 received nongemcitabine regimens (11%). We measured protein levels of hENT1, dCK, and RRM1 by semiquantitative immunohistochemistry with tissue microarrays and investigated their relationship with patients' overall survival time.

RESULTS

The median overall survival time of patients was 32.0 months. Among patients who did not receive adjuvant treatment, levels of hENT1, RRM1, and dCK were not associated with survival time. Among patients who received gemcitabine, high levels of hENT1 and dCK were significantly associated with longer survival time (hazard ratios of 0.34 [P < .0001] and 0.57 [P = .012], respectively). Interaction tests for gemcitabine administration and hENT1 and dCK status were statistically significant (P = .0007 and P = .016, respectively). On multivariate analysis of this population, hENT1 and dCK retained independent predictive values, and those patients with high levels of each protein had the longest survival times following adjuvant therapy with gemcitabine.

CONCLUSIONS

High levels of hENT1 and dCK in PDAC predict longer survival times in patients treated with adjuvant gemcitabine.

New biomarkers and targets in pancreatic cancer and their application to treatment

Late diagnosis of pancreatic ductal adenocarcinoma (pancreatic cancer) and the limited response to current treatments results in an exceptionally poor prognosis. Advances in our understanding of the molecular events underpinning pancreatic cancer development and metastasis offer the hope of tangible benefits for patients. In-depth mutational analyses have shed light on the genetic abnormalities in pancreatic cancer, providing potential treatment targets. New biological studies in patients and in mouse models have advanced our knowledge of the timing of metastasis of pancreatic cancer, highlighting new directions for the way in which patients are treated. Furthermore, our increasing understanding of the molecular events in tumorigenesis is leading to the identification of biomarkers that enable us to predict response to treatment. A major drawback, however, is the general lack of an adequate systematic approach to advancing the use of biomarkers in cancer drug development, highlighted in a Cancer Biomarkers Collaborative consensus report. In this Review, we summarize the latest insights into the biology of pancreatic cancer, and their repercussions for treatment. We provide an overview of current treatments and, finally, we discuss novel therapeutic approaches, including the role of biomarkers in therapy for pancreatic cancer.

The MUC4 mucin mediates gemcitabine resistance of human pancreatic cancer cells via the Concentrative Nucleoside Transporter family

The fluorinated analog of deoxycytidine, Gemcitabine (Gemzar), is the main chemotherapeutic drug in pancreatic cancer, but survival remains weak mainly because of the high resistance of tumors to the drug. Recent works have shown that the mucin MUC4 may confer an advantage to pancreatic tumor cells by modifying their susceptibility to drugs. However, the cellular mechanism(s) responsible for this MUC4-mediated resistance is unknown. The aim of this work was to identify the cellular mechanisms responsible for gemcitabine resistance linked to MUC4 expression. CAPAN-2 and CAPAN-1 adenocarcinomatous pancreatic cancer (PC) cell lines were used to establish stable MUC4-deficient clones (MUC4-KD) by shRNA interference. Measurement of the IC50 index using tetrazolium salt test indicated that MUC4-deficient cells were more sensitive to gemcitabine. This was correlated with increased Bax/BclXL ratio and apoptotic cell number. Expression of Equilibrative/Concentrative Nucleoside Transporter (hENT1, hCNT1/3), deoxycytidine kinase (dCK), ribonucleotide reductase (RRM1/2) and Multidrug-Resistance Protein (MRP3/4/5) was evaluated by quantitative RT-PCR (qRT-PCR) and western blotting. Alteration of MRP3, MRP4, hCNT1 and hCNT3 expression was observed in MUC4-KD cells, but only hCNT1 alteration was correlated to MUC4 expression and sensitivity to gemcitabine. Decreased activation of MAPK, JNK and NF-κB pathways was observed in MUC4-deficient cells, in which the NF-κB pathway was found to have an important role in both sensitivity to gemcitabine and hCNT1 regulation. Finally, and in accordance with our in vitro data, we found that MUC4 expression was conversely correlated to that of hCNT1 in tissues from patients with pancreatic adenocarcinoma. This work describes a new mechanism of PC cell resistance to gemcitabine, in which the MUC4 mucin negatively regulates the hCNT1 transporter expression via the NF-κB pathway. Altogether, these data point out to MUC4 and hCNT1 as potential targets to ameliorate the response of pancreatic tumors to gemcitabine treatment.

DCK is frequently inactivated in acquired gemcitabine-resistant human cancer cells

Although gemcitabine is the most effective chemotherapeutic agent against pancreatic cancer, a growing concern is that a substantial number of patients acquire gemcitabine chemoresistance. To elucidate the mechanisms of acquisition of gemcitabine resistance, we developed gemcitabine-resistant cell lines from six human cancer cell lines; three pancreatic, one gastric, one colon, and one bile duct cancer. We first analyzed gemcitabine uptake using three paired parental and gemcitabine resistant pancreatic cancer cell lines (PK-1 and RPK-1, PK-9 and RPK-9, PK-59 and RPK-59) and found that uptake of gemcitabine was rapid. However, no DNA damage was induced in resistant cells. We further examined the microarray-based expression profiles of the cells to identify genes associated with gemcitabine resistance and found a remarkable reduction in the expression of deoxycytidine kinase (DCK). DCK is a key enzyme that activates gemcitabine by phosphorylation. Genetic alterations and expression of DCK were studied in these paired parental and derived gemcitabine-resistant cell lines, and inactivating mutations were found only in gemcitabine-resistant cell lines. Furthermore, siRNA-mediated knockdown of DCK in the parental cell lines yielded gemcitabine resistance, and introduction of DCK into gemcitabine-resistant cell lines invariably restored gemcitabine sensitivities. Mutation analyses were expanded to three other different paired cell lines, DLD-1 and RDLD-1 (colon cancer cell line), MKN-28 and RMKN-28 (gastric cancer cell line), and TFK-1 and RTFK -1 (cholangiocarcinoma cell line). We found inactivating mutations in RDLD-1 and RTFK-1 and decreased expression of DCK in RMKN-28. These results indicate that the inactivation of DCK is one of the crucial mechanisms in acquisition of gemcitabine resistance.

Regulation of deoxycytidine kinase expression and sensitivity to gemcitabine by micro-RNA 330 and promoter methylation in cancer cells

Deoxycytidine kinase (dCK) is essential for phosphorylation of natural deoxynucleosides and analogs, such as gemcitabine and cytarabine, two widely used anticancer compounds. Regulation of dCK is complex, including Ser-74 phosphorylation. We hypothesized that dCK could be regulated by two additional mechanisms: micro-RNA (miRNA) and promoter methylation. Methylation-specific PCR (MSP) revealed methylation of the 3' GC box in three out of six cancer cell lines. The 3' GC box is located at the dCK promoter region. The methylation status was related to dCK mRNA expression. TargetScan and miRanda prediction algorithms revealed several possible miRNAs targeting dCK and identified miR-330 (micro-RNA 330) as the one conserved between the human, the chimpanzee, and the rhesus monkey genomes. Expression of miR-330 in various colon and lung cancer cell lines, as measured by QRT-PCR, varied five-fold between samples and correlated with in-vitro gemcitabine resistance (R = 0.82, p = 0.04). Exposure to gemcitabine also appeared to influence miR-330 levels in these cell lines. Furthermore, in our cell line panel, miR-330 expression negatively correlated with dCK mRNA expression (R = 0.74), suggesting a role of miR-330 in post-transcriptional regulation of dCK. In conclusion, the 3' GC box and miR-330 may regulate dCK expression in cancer cells.

Synthesis and in vitro evaluation of novel lipophilic monophosphorylated gemcitabine derivatives and their nanoparticles

Gemcitabine hydrochloride (HCl) is approved for the treatment of a wide spectrum of solid tumors. However, the rapid development of resistance often makes gemcitabine less efficacious. In the present study, we synthesized several novel lipophilic monophosphorylated gemcitabine derivatives, incorporated them into solid lipid nanoparticles, and then evaluated their ability to overcome major known gemcitabine resistance mechanisms by evaluating their in vitro cytotoxicities in cancer cells that are deficient in deoxycytidine kinase (dCK), deficient in human equilibrative nucleoside transporter (hENT1), over-expressing ribonucleotide reductase M1 subunit (RRM1), or over-expressing RRM2. In dCK deficient cells, the monophosphorylated gemcitabine derivatives and their nanoparticles were up to 86-fold more cytotoxic than gemcitabine HCl. The majority of the gemcitabine derivatives and their nanoparticles were more cytotoxic than gemcitabine HCl in cells that over-expressing RRM1 or RRM2, and the gemcitabine derivatives in nanoparticles were also resistant to deamination by deoxycytidine deaminase. The gemcitabine derivatives (in nanoparticles) hold a great potential in overcoming gemcitabine resistance.

New strategies and designs in pancreatic cancer research: consensus guidelines report from a European expert panel

Although the treatment of pancreatic ductal adenocarcinoma (PDAC) remains a huge challenge, it is entering a new era with the development of new strategies and trial designs. Because there is an increasing number of novel therapeutic agents and potential combinations available to test in patients with PDAC, the identification of robust prognostic and predictive markers and of new targets and relevant pathways is a top priority as well as the design of adequate trials incorporating molecular-driven hypothesis. We presently report a consensus strategy for research in pancreatic cancer that was developed by a multidisciplinary panel of experts from different European institutions and collaborative groups involved in pancreatic cancer. The expert panel embraces the concept of exploratory early proof of concept studies, based on the prediction of response to novel agents and combinations, and randomised phase II studies permitting the selection of the best therapeutic approach to go forward into phase III, where the recommended primary end point remains overall survival. Trials should contain as many translational components as possible, relying on standardised tissue and blood processing and robust biobanking, and including dynamic imaging. Attention should not only be paid to the pancreatic cancer cells but also to microenvironmental factors and stem/stellate cells.