Cytidine Deaminase as a Molecular Predictor of Gemcitabine Response in Patients with Biliary Tract Cancer

Allosteric and transport modulation of human concentrative nucleoside transporter 3 at the atomic scale

Nucleosides are important precursors of nucleotide synthesis in cells, and nucleoside transporters play an important role in many physiological processes by mediating transmembrane transport and absorption. During nucleoside transport, such proteins undergo a significant conformational transition between the outward- and inward-facing states, which leads to alternating access of the substrate-binding site to either side of the membrane. In this work, a variety of molecular simulation methods have been applied to comparatively investigate the motion modes of human concentrative nucleoside transporter 3 (hCNT3) in three states, as well as global and local cavity conformational changes; and finally, a possible elevator-like transport mechanism consistent with experimental data was proposed. The results of the Gaussian network model (GNM) and anisotropic network model (ANM) show that hCNT3 as a whole tends to contract inwards and shift towards a membrane inside, exhibiting an allosteric process that is more energetically favorable than the rigid conversion. To reveal the complete allosteric process of hCNT3 in detail, a series of intermediate conformations were obtained by an adaptive anisotropic network model (aANM). One of the simulated intermediate states is similar to that of a crystal structure, which indicates that the allosteric process is reliable; the state with lower energy is slightly inclined to the inward-facing structure rather than the expected intermediate crystal structure. The final HOLE analysis showed that except for the outward-facing state, the transport channels were gradually enlarged, which was conductive to the directional transport of nucleosides. Our work provides a theoretical basis for the multistep elevator-like transportation mechanism of nucleosides, which helps to further understand the dynamic recognition between nucleoside substrates and hCNT3 as well as the design of nucleoside anticancer drugs.

RRM1 Expression as a Prognostic Biomarker for Unresectable or Recurrent Biliary Tract Cancer Treated with Gemcitabine plus Cisplatin

The combination of gemcitabine plus cisplatin (GP) is regarded as a first-line treatment for patients with unresectable or recurrent biliary tract cancer (BTC). Several proteins including human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (DCK), cytidine deaminase (CDA), and ribonucleotide reductase subunit 1 (RRM1) are known to be involved in gemcitabine uptake and metabolism. This study was aimed to identify the predictive and prognostic values of these biomarkers in patients who treated with GP for advanced BTC. Tumor samples were obtained from 34 patients with unresectable or recurrent BTC who were treated with GP between August 2015 and February 2018. Intratumoral expression of hENT1, DCK, CDA and RRM1 was determined by immunohistochemistry and analyzed for association with chemotherapy response, progression-free survival (PFS) and overall survival (OS). Median OS was significantly longer in the RRM1-negative group than in the RRM1-positive (9.9 months vs. 5.9 months, p = 0.037). Multivariate adjustment analyses also demonstrated RRM1 expression as an independent prognostic factor for OS in patients treated with GP chemotherapy. Increased intratumoral expression of RRM1 on immunohistochemical staining may be a biomarker predicting poor survival in patients with GP chemotherapy for advanced BTC. Large-scale well-predefined prospective research is needed to validate the utility of biomarkers in clinical practice.

Current and New Biomarkers for Early Detection, Prognostic Stratification, and Management of Gallbladder Cancer Patients

Gallbladder cancer (GBC) is an aggressive disease that shows evident geographic variation and is characterized by a poor prognosis, mainly due to the late diagnosis and ineffective treatment. Genetic variants associated with GBC susceptibility, including polymorphisms within the toll-like receptors TLR2 and TLR4, the cytochrome P450 1A1 (CYP1A1), and the ATP-binding cassette (ABC) transporter ABCG8 genes, represent promising biomarkers for the stratification of patients at higher risk of GBC; thus, showing potential to prioritize cholecystectomy, particularly considering that early diagnosis is difficult due to the absence of specific signs and symptoms. Similarly, our better understanding of the gallbladder carcinogenic processes has led to identify several cellular and molecular events that may influence patient management, including HER2 aberrations, high tumor mutational burden, microsatellite instability, among others. Despite these reports on interesting and promising markers for risk assessment, diagnosis, and prognosis; there is an unmet need for reliable and validated biomarkers that can improve the management of GBC patients and support clinical decision-making. This review article examines the most potentially significant biomarkers of susceptibility, diagnosis, prognosis, and therapy selection for GBC patients, highlighting the need to find and validate existing and new molecular biomarkers to improve patient outcomes.

Predictive and Prognostic Properties of Human Equilibrative Nucleoside Transporter 1 Expression in Gemcitabine-Treated Pancreatobiliary Cancer: A Meta-Analysis

Purpose

Gemcitabine, the primary drug for the treatment of pancreatobiliary cancer (PBC), requires human equilibrative nucleoside transporter 1 (hENT1) to enter cells. High tumoral hENT1 expression has been linked with improved survival among patients with PBC treated with gemcitabine; however, this finding has been inconsistent, and studies used different expression assays.

Methods

Databases were reviewed for studies that examined hENT1 and clinical outcome in PBC. Of 307 publications, 34 studies were found that used immunohistochemistry (IHC) with one of eight anti–hENT1 antibody assays. Five studies were excluded for redundancy, and 29 studies underwent detailed review.

Results

On average, 51% of tumor samples had high hENT1 expression (range, 7% to 92%). Among studies that examined hENT1 expression and overall survival (OS), 58% (15 of 26 studies) showed an association between high tumoral hENT1 and improved OS for gemcitabine-treated patients. Among 10D7G2 antibody studies, 88% (seven of eight studies) demonstrated this association. Studies with other antibodies—in particular, SP120 (two of nine studies)—were less consistent. The ability to detect an association between improved OS and high hENT1 was antibody dependent (χ2 P = .0237). An association between high tumoral hENT1 expression and improved disease-free/progression-free survival (DFS/PFS) was demonstrated in 71% of studies (15 of 21 studies). Pooled hazard ratio (HR) analyses of all antibody studies demonstrated a link between high hENT1 tumor expression and improved OS (HR, 0.674; 95% CI, 0.509 to 0.893; P = .006) and DFS/PFS (HR, 0.740; 95% CI, 0.517 to 0.1.059; P = .10). This signal was stronger among studies that used the 10D7G2 antibody in comparison to those in which another antibody was used, with HRs of 0.488 (95% CI, 0.396 to 0.602; P < .001) and 0.410 (95% CI, 0.280 to 0.599; P < .001), respectively.

Conclusion

High tumoral hENT1 expression on IHC with 10D7G2 is a strong and reproducible prognostic marker for improved outcome among gemcitabine-treated patients with PBC.

CDA gene silencing regulated the proliferation and apoptosis of chronic myeloid leukemia K562 cells

Background

As a disease of hematopoietic stem cell, chronic myeloid leukemia (CML) possesses unique biological and clinical features. However, the biologic mechanism underlying its development remains poorly understood. Thus, the objective of the present study is to discuss the effect of cytidine deaminase (CDA) gene silencing on the apoptosis and proliferation of CML K562 cells.

Methods

CDA mRNA expression was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and enzymatic activity of CDA was measured by a nuclide liquid scintillation method. RT-qPCR and Western blot analysis were used to detect CDA mRNA and protein expression. Cell proliferation, apoptosis and cell cycle were measured by CCK-8 assay and flow cytometry. The expression of proteins relevant to cell proliferation, apoptosis and cell cycle was measured by Western blot analysis. Tumor xenografts were implanted in nude mice to verify the effect of CDA silencing on tumor growth in vivo.

Results

CML and AL patients showed increased mRNA expression and enzymatic activity of CDA. Compared with the blank group, the mRNA and protein expression of CDA in the shRNA-1 and shRNA-2 groups decreased significantly. As a result, the proliferation of K562 cells was inhibited after CDA silencing and the cells were mainly arrested in S and G2 phases, while the apoptosis rate of these cells was increased. In addition, CDA gene silencing in K562 cells led to down-regulated p-ERK1/2, t-AKT, p-AKT and BCL-2 expression and up-regulated expression of P21, Bax, cleaved caspase-3/total caspase-3 and cleaved PARP/total PARP. Finally, CDA gene silencing inhibited tumor growth.

Conclusion

Our study demonstrated that CDA gene silencing could inhibit CML cell proliferation and induce cell apoptosis. Therefore, CDA gene silencing may become an effective target for the treatment of leukemia.

Vitamin E Phosphate Nucleoside Prodrugs: A Platform for Intracellular Delivery of Monophosphorylated Nucleosides

Vitamin E phosphate (VEP) nucleoside prodrugs are designed to bypass two mechanisms of tumor resistance to therapeutic nucleosides: nucleoside transport and kinase downregulation. Certain isoforms of vitamin E (VE) have shown activity against solid and hematologic tumors and result in chemosensitization. Because gemcitabine is one of the most common chemotherapeutics for the treatment of cancer, it was used to demonstrate the constructs utility. Four different VE isoforms were conjugated with gemcitabine at the 5′ position. Two of these were δ-tocopherol-monophosphate (MP) gemcitabine (NUC050) and δ-tocotrienol-MP gemcitabine (NUC052). NUC050 was shown to be able to deliver gemcitabine-MP intracellularly by a nucleoside transport independent mechanism. Its half-life administered IV in mice was 3.9 h. In a mouse xenograft model of non-small cell lung cancer (NSCLC) NCI-H460, NUC050 at a dose of 40 mg/kg IV qwk × 4 resulted in significant inhibition to tumor growth on days 11–31 (p < 0.05) compared to saline control (SC). Median survival was 33 days (NUC050) vs. 25.5 days (SC) ((hazard ratio) HR = 0.24, p = 0.017). Further, NUC050 significantly inhibited tumor growth compared to historic data with gemcitabine at 135 mg/kg IV q5d × 3 on days 14–41 (p < 0.05). NUC052 was administered at a dose of 40 mg/kg IV qwk × 2 followed by 50 mg/kg qwk × 2. NUC052 resulted in inhibition to tumor growth on days 14–27 (p < 0.05) and median survival was 34 days (HR = 0.27, p = 0.033). NUC050 and NUC052 have been shown to be safe and effective in a mouse xenograft of NSCLC.

Overcoming tumor cell chemoresistance using nanoparticles: lysosomes are beneficial for (stearoyl) gemcitabine-incorporated solid lipid nanoparticles

Despite recent advances in targeted therapies and immunotherapies, chemotherapy using cytotoxic agents remains an indispensable modality in cancer treatment. Recently, there has been a growing emphasis in using nanomedicine in cancer chemotherapy, and several nanomedicines have already been used clinically to treat cancers. There is evidence that formulating small molecular cancer chemotherapeutic agents into nanomedicines significantly modifies their pharmacokinetics and often improves their efficacy. Importantly, cancer cells often develop resistance to chemotherapy, and formulating anticancer drugs into nanomedicines also helps overcome chemoresistance. In this review, we briefly describe the different classes of cancer chemotherapeutic agents, their mechanisms of action and resistance, and evidence of overcoming the resistance using nanomedicines. We then emphasize on gemcitabine and our experience in discovering the unique (stearoyl) gemcitabine solid lipid nanoparticles that are effective against tumor cells resistant to gemcitabine and elucidate the underlying mechanisms. It seems that lysosomes, which are an obstacle in the delivery of many drugs, are actually beneficial for our (stearoyl) gemcitabine solid lipid nanoparticles to overcome tumor cell resistance to gemcitabine.

Severe acute toxicity following gemcitabine administration: A report of four cases with cytidine deaminase polymorphisms evaluation

Gemcitabine (GCB) is a pyrimidine antimetabolite widely used in various solid tumors as a single agent or as a component of multidrug regimens. In the majority of patients, GCB is well tolerated, however life-threatening complications occasionally occur. The current report presents four cases of severe acute toxicity, which included two that were fatal, following administration of GCB alone or in combination with cisplatin. Of the four cases, in one, a Naranjo Adverse Drug Reaction Probability Score was definite, in two, probable and in one possible. To determine the potential causes of these toxicities, polymorphic variants of cytidine deaminase, the primary enzyme involved in the hepatic metabolism of GCB, were assessed. The homogeneous c.435TT variant was detected in one patient and a heterozygotic c.435CT variant in two, one of whom additionally harbored a heterozygotic c.79AC variant.

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.

[Chemotherapy for Biliary Tract Cancer]

The term of biliary tract cancer (BTC) refers to all tumors that arise from the biliary tract or the biliary drainage system, including the intra- and extra-hepatic bile ducts as well as the gallbladder. BTCs are aggressive tumors with limited treatment options and poor overall survival. Currently, surgery remains to be the only potentially curative treatment, and most patients develop recurrence. For advanced tumors, only limited effective treatment modalities exist today. Gemcitabine plus cisplatin is considered as a standard option for advanced biliary cancer. A randomized phase III trial (ABC-02 trial) showed superiority of gemcitabine plus cisplatin over gemcitabine alone. In that study, they showed that after a median follow-up of 8.2 months, the median overall survival was 8.1 months in the gemcitabine-only group and 11.7 months in the gemcitabine plus cisplatin group (p<0.001). However, while this is a definite advancement, a 3-month survival extension among patients with BTC is modest at best. Moreover, this regimen has not been compared head-to-head with other gemcitabine based combinations. Gemcitabine monotherapy, 5-fluorouracil plus leucovorin, and single-agent capecitabine are all reasonable options for patients with a borderline performance status. Recent advancements have provided new insight into the genomic landscape of BTCs, and thus, it remains unclear whether combined treatment with molecular targeted agents or other cytotoxic chemotherapeutic agents may also be effective against advanced BTC.