Enhancement of the antitumour activity of 5-fluorouracil (5-FU) by inhibiting dihydropyrimidine dehydrogenase activity (DPD) using 5-chloro-2,4-dihydroxypyridine (CDHP) in human tumour cells

Design, synthesis, and evaluation of JTE-013 derivatives as novel potent S1PR2 antagonists for recovering the sensitivity of colorectal cancer to 5-fluorouracil

Targeting sphingosine-1-phosphate receptor 2 (S1PR2) has been proved as a promising strategy to reverse 5-fluorouracil (5-FU) resistance. Here, we report the discovery of the novel JTE-013 derivative compound 37 h as a more effective S1PR2 antagonist to reverse 5-FU resistance in SW620/5-FU and HCT116^DPD cells than JTE-013 and previously reported compound 5. Compound 37 h could effectively bind S1PR2 and reduce its expression, thus leading to decreased expression of JMJD3 and dihydropyrimidine dehydrogenase (DPD), while also increasing the level of H3K27me3 to decrease the degradation of 5-FU and thereby increase its intracellular concentration in SW620/5-FU, HCT116^DPD, and L02 cells. Furthermore, compound 37 h showed good selectivity to other S1PRs and normal colon cell line NCM460. Western blot analysis demonstrated that compound 37 h could abrogate the FBAL-stimulated upregulation of DPD expression by S1PR2. Importantly, compound 37 h also showed favorable metabolic stability with a long half-life (t_1/2) of 7.9 h. Moreover, compound 37 h significantly enhanced the antitumor efficacy of 5-FU in the SW620/5-FU animal model. Thus, the JTE-013-based derivative compound 37 h represents a promising lead compound for the development of novel 5-FU sensitizers for colorectal cancer (CRC) therapy.

Dihydropyrimidine Dehydrogenase-Mediated Resistance to 5-Fluorouracil: Mechanistic Investigation and Solution

5-Fluorouracil (5-FU) is one of the most widely used chemotherapeutics for the treatment of cancers associated with the aerodigestive tract, breast, and colorectal system. The efficacy of 5-FU is majorly affected by dihydropyrimidine dehydrogenase (DPD) as it degrades more than 80% of administered 5-FU into an inactive metabolite, dihydrofluorouracil. Herein we discuss the molecular mechanism of this inactivation by analyzing the interaction pattern and electrostatic complementarity of the DPD-5-FU complex. The basis of DPD overexpression in cancer cell lines due to significantly distinct levels of the miRNAs (miR-134, miR-27b, and miR-27a) compared to normal cells has also been outlined. Additionally, some kinases including sphingosine kinase 2 (SphK2) have been reported to correlate with DPD expression. Currently, to address this problem various strategies are reported in the literature, including 5-FU analogues (bypass the DPD-mediated inactivation), DPD downregulators (regulate the DPD expression levels in tumors), inhibitors (as promising adjuvants), and formulation development loaded with 5-FU (liposomes, nanoparticles, nanogels, etc.), which are briefly discussed in this Review.

Drug Resistance in Colorectal Cancer: From Mechanism to Clinic

Colorectal cancer (CRC) is one of the leading causes of death worldwide. The 5-year survival rate is 90% for patients with early CRC, 70% for patients with locally advanced CRC, and 15% for patients with metastatic CRC (mCRC). In fact, most CRC patients are at an advanced stage at the time of diagnosis. Although chemotherapy, molecularly targeted therapy and immunotherapy have significantly improved patient survival, some patients are initially insensitive to these drugs or initially sensitive but quickly become insensitive, and the emergence of such primary and secondary drug resistance is a significant clinical challenge. The most direct cause of resistance is the aberrant anti-tumor drug metabolism, transportation or target. With more in-depth research, it is found that cell death pathways, carcinogenic signals, compensation feedback loop signal pathways and tumor immune microenvironment also play essential roles in the drug resistance mechanism. Here, we assess the current major mechanisms of CRC resistance and describe potential therapeutic interventions.

Design, synthesis and biological evaluation of sphingosine-1-phosphate receptor 2 antagonists as potent 5-FU-resistance reversal agents for the treatment of colorectal cancer

5-Fluorouracil (5-FU) and its prodrugs are the essential clinical drugs for colorectal cancer (CRC) treatment. However, the drug resistance of 5-FU has caused high mortality of CRC patients. Thus, it is urgent to develop reversal agents of 5-FU resistance. Sphingosine-1-phosphate receptor 2 (S1PR2) was proved to be a potential target for reversing 5-FU resistance, but the activity of known S1PR2 antagonists JTE-013 were weak in 5-FU-resistant cell lines. To develop more potent S1PR2 antagonists to treat 5-FU-resistant cancer, a series of JTE-013 derivatives were designed and synthesized. The most promising compound 40 could markedly reverse the resistance in 5-FU-resistant HCT116 cells and 5-FU-resistant SW620 cells via inhibiting the expression of dihydropyrimidine dehydrogenase (DPD). The key was that compound 40 with improved pharmacokinetic properties significantly increased the inhibitory rate of 5-FU in the SW620/5-FU cells xenograft model with no observable toxicity by inhibiting the expression of DPD in tumor and liver tissues. Altogether, these results suggest that compound 40 may be a promising drug candidate to reverse 5-FU resistance in the treatment of CRC.

Phase I study of DFP-11207, a novel oral fluoropyrimidine with reasonable AUC and low Cmax and improved tolerability, in patients with solid tumors

5-fluorouracil (5-FU) and 5-FU derivatives, such as capecitabine, UFT, and S-1, are the mainstay of chemotherapy treatment for gastrointestinal cancers, and other solid tumors. Compared with other cytotoxic chemotherapies, these drugs generally have a favorable safety profile, but hematologic and gastrointestinal toxicities remain common. DFP-11207 is a novel oral cytotoxic agent that combines a 5-FU pro-drug with a reversible DPD inhibitor and a potent inhibitor of OPRT, resulting in enhanced pharmacological activity of 5-FU with decreased gastrointestinal and myelosuppressive toxicities. In this Phase I study (NCT02171221), DFP-11207 was administered orally daily, in doses escalating from 40 mg/m2/day to 400 mg/m2/day in patients with esophageal, colorectal, gastric, pancreatic or gallbladder cancer (n = 23). It was determined that DFP-11207 at the dose of 330 mg/m2/day administered every 12 hours was well-tolerated with mild myelosuppressive and gastrointestinal toxicities. The pharmacokinetic analysis determined that the 5-FU levels were in the therapeutic range at this dose. In addition, fasted or fed states had no influence on the 5-FU levels (patients serving as their own controls). Among 21 efficacy evaluable patients, 7 patients had stable disease (33.3%), of which two had prolonged stable disease of >6 months duration. DFP-11207 can be explored as monotherapy or easily substitute 5-FU, capecitabine, or S-1 in combination regimens.

5-fluorouracil and other fluoropyrimidines in colorectal cancer: Past, present and future

5-Fluorouracil (5-FU) is an essential component of systemic chemotherapy for colorectal cancer (CRC) in the palliative and adjuvant settings. Over the past four decades, several modulation strategies including the implementation of 5-FU-based combination regimens and 5-FU pro-drugs have been developed and tested to increase the anti-tumor activity of 5-FU and to overcome the clinical resistance. Despite the encouraging progress in CRC therapy to date, the patients' response rates to therapy continue to remain low and the patients' benefit from 5-FU-based therapy is frequently compromised by the development of chemoresistance. Inter-individual differences in the treatment response in CRC patients may originate in the unique genetic and epigenetic make-up of each individual. The critical element in the current trend of personalized medicine is the proper comprehension of causes and mechanisms contributing to the low or lack of sensitivity of tumor tissue to 5-FU-based therapy. The identification and validation of predictive biomarkers for existing 5-FU-based and new targeted therapies for CRC treatment will likely improve patients' outcomes in the future. Herein we present a comprehensive review summarizing options of CRC treatment and the mechanisms of 5-FU action at the molecular level, including both anabolic and catabolic ways. The main part of this review comprises the currently known molecular mechanisms underlying the chemoresistance in CRC patients. We also focus on various 5-FU pro-drugs developed to increase the amount of circulating 5-FU and to limit toxicity. Finally, we propose future directions of personalized CRC therapy according to the latest published evidence.

5-Fluorouracil-based adjuvant chemotherapy improves the clinical outcomes of patients with lymphovascular invasion of upper urinary tract cancer and low expression of dihydropyrimidine dehydrogenase

Lymphovascular invasion (LVI) by urothelial carcinoma of the upper urinary tract (UC-UUT) is associated with an unfavorable prognosis. However, a high proportion of patients with UC-UUT are unable to receive the recommended doses of cisplatin-based adjuvant chemotherapy due to advanced age or renal dysfunction resulting from nephroureterectomy. Tegafur-uracil is an oral form of 5-fluorouracil whose efficacy is influenced by the activities of enzymes associated with its metabolism, such as dihydropyrimidine dehydrogenase (DPD), orotatephosphoribosyltransferase (OPRT) and thymidylate synthase (TS). The aim of the present study was to investigate the efficacy of adjuvant 5-fluorouracil chemotherapy for UC-UUT with LVI, and to assess the expression of enzymes associated with 5-fluorouracil metabolism as promising biomarkers of therapy efficacy. The present study retrospectively investigated 52 cases of UC-UUT. Following nephroureterectomy, tegafur-uracil was administered to 15 out of 30 patients with LVI who were not eligible for cisplatin-based adjuvant chemotherapy. Levels of DPD, OPRT and TS expression in tumor specimens were determined by reverse transcription-quantitative polymerase chain reaction, and their associations with the efficacy of adjuvant 5-fluorouracil chemotherapy were analyzed. The levels of DPD, OPRT and TS expression were not associated with pathological factors or outcome, although a higher expression of TS was associated with a poorer outcome. Adjuvant 5-fluorouracil chemotherapy significantly improved the outcome of patients with lower DPD expression. However, the levels of OPRT and TS expression did not influence therapeutic efficacy. Adjuvant 5-fluorouracil chemotherapy appears to be effective for lymphovascular-invasive UC-UUT in patients with lower DPD expression.

Drug metabolizing enzymes and their inhibitors' role in cancer resistance

Despite continuous research on chemotherapeutic agents, different mechanisms of resistance have become a major pitfall in cancer chemotherapy. Although, exhaustive efforts are being made by several researchers to target resistance against chemotherapeutic agents, there is another class of resistance mechanism which is almost carrying on unattended. This class of resistance includes pharmacokinetics resistance such as efflux by ABC transporters and drug metabolizing enzymes. ABC transporters are the membrane bound proteins which are responsible for the movement of substrates through the cell membrane. Drug metabolizing enzymes are an integral part of phase-II metabolism that helps in the detoxification of exogenous, endogenous and xenobiotics substrates. These include uridine diphospho-glucuronosyltransferases (UGTs), glutathione-S-transferases (GSTs), dihydropyrimidine dehydrogenases (DPDs) and thiopurine methyltransferases (TPMTs). These enzymes may affect the role of drugs in both positive as well negative manner, depending upon the type of tissue and cells present and when present in tumors, can result in drug resistance. However, the underlying mechanism of resistance by drug metabolizing enzymes is still not clear. Here, we have tried to cover various aspects of these enzymes in relation to anticancer drugs.

TAS-114, a First-in-Class Dual dUTPase/DPD Inhibitor, Demonstrates Potential to Improve Therapeutic Efficacy of Fluoropyrimidine-Based Chemotherapy

5-Fluorouracil (5-FU) is an antimetabolite and exerts antitumor activity via intracellularly and physiologically complicated metabolic pathways. In this study, we designed a novel small molecule inhibitor, TAS-114, which targets the intercellular metabolism of 5-FU to enhance antitumor activity and modulates catabolic pathway to improve the systemic availability of 5-FU. TAS-114 strongly and competitively inhibited deoxyuridine 5'-triphosphate nucleotidohydrolase (dUTPase), a gatekeeper protein preventing aberrant base incorporation into DNA, and enhanced the cytotoxicity of fluoropyrimidines in cancer cells; however, it had little intrinsic activity. In addition, TAS-114 had moderate and reversible inhibitory activity on dihydropyrimidine dehydrogenase (DPD), a catabolizing enzyme of 5-FU. Thus, TAS-114 increased the bioavailability of 5-FU when coadministered with capecitabine in mice, and it significantly improved the therapeutic efficacy of capecitabine by reducing the required dose of the prodrug by dual enzyme inhibition. Enhancement of antitumor efficacy caused by the addition of TAS-114 was retained in the presence of a potent DPD inhibitor containing oral fluoropyrimidine (S-1), indicating that dUTPase inhibition plays a major role in enhancing the antitumor efficacy of fluoropyrimidine-based therapy. In conclusion, TAS-114, a dual dUTPase/DPD inhibitor, demonstrated the potential to improve the therapeutic efficacy of fluoropyrimidine. Dual inhibition of dUTPase and DPD is a novel strategy for the advancement of oral fluoropyrimidine-based chemotherapy for cancer treatment. Mol Cancer Ther; 17(8); 1683-93. ©2018 AACR.

5-Chloro-2,4-dihydroxypyridine, CDHP, prevents lung metastasis of basal-like breast cancer cells by reducing nascent adhesion formation

A drug for metastasis prevention is necessary. The orally administered anticancer drug S‐1 contributes to cancer therapy. In a mouse xenograft model of metastatic breast cancer from our previous study, the administration of S‐1 inhibited lung metastasis. However, the mechanism of inhibition remains elusive. S‐1 contains 5‐chloro‐2,4‐dihydroxypyridine (CDHP), which does not have the antigrowth activity, but prevents the degradation of 5‐fluorouracil, an anticancer reagent. In this study, we found that CDHP treatment shrinks cell morphology in metastatic basal‐like breast cancer cell lines. Wound healing assays showed reduced cell migration in CDHP‐treated cells. At the molecular level, CDHP treatment reduced the number of nascent adhesions, whereas the number of mature focal adhesions was not changed. These findings indicate that CDHP impairs focal adhesion formation, which results in a reduction in cell migration. For the in vivo metastasis assay, we used a highly lung‐metastatic cell line. We xenografted them into immunodeficient mice, and administered CDHP. To determine whether CDHP prevents metastasis, we measured the weights of harvested lungs. The results showed that the lung weights of the CDHP‐treated animals were not significantly different compared to the no‐tumor controls, whereas the vehicle group showed a number of metastatic foci and an increase in lung weight. These observations indicate that CDHP administration prevents metastasis. This study reveals a novel effect of CDHP for lung metastasis prevention. Our findings may facilitate the establishment of future metastasis prevention therapies.

Clinical implications of dihydropyrimidine dehydrogenase expression in patients with pancreatic cancer who undergo curative resection with S-1 adjuvant chemotherapy

The predictive roles of dihydropyrimidine dehydrogenase (DPD) in patients who undergo curative resection and adjuvant chemotherapy with S-1, which is the oral 5-fluorouracil prodrug tegafur combined with oteracil and gimeracil, remain unclear. In the present study, the clinical data from 66 consecutive patients who underwent curative resection and received adjuvant chemotherapy with S-1 for the treatment of pancreatic cancer at Kanagawa Cancer Center (Yokohama City, Japan) from April 2005 to March 2014 were retrospectively analyzed. The association between the DPD status and the survival and clinicopathological features were investigated. Of the 66 patients, 34 patients exhibited positive DPD expression (51.5%). Although a significant increase in DPD expression in male patients was observed, no significant differences were identified for other clinicopathological parameters, including tumor factor or node factor, between the DPD-positive expression group and the DPD-negative expression group. The median follow-up period of the present study was 29.2 months. There was no significant difference in the 3-year overall survival (OS) rates following surgery, which were 12.6 and 14.5% in the DPD-positive and DPD-negative expression groups, respectively (P=0.352). However, in a subgroup analysis, a significant difference in the 3-year OS rates following surgery was noted, which were 58.9 and 14.5% in the DPD-high and DPD-low expression groups, respectively (P=0.019). The intratumoral DPD expression in curatively resected pancreatic cancer patients treated with S-1 adjuvant chemotherapy was identified to not be useful as a predictive marker, whereas the level of DPD expression is a potential predictive marker. The results of the present study require confirmation in another cohort or in a prospective multicenter study.

Conversion surgery after combination chemotherapy of docetaxel, cisplatin and S-1 (DCS) for far-advanced gastric cancer

PURPOSE

A triplet regimen of docetaxel, cisplatin, and S-1(DCS) is highly effective against metastatic gastric cancer. We performed this study to clarify the safety and efficacy of surgical resection in patients with initially unresectable gastric cancer, after down-staging or disease control was achieved by DCS chemotherapy.

METHODS

The subjects of this retrospective study were 31 consecutive patients with initially unresectable gastric cancer, who underwent surgical resection between October, 2006 and December, 2012, after down-staging or disease control was achieved by DCS chemotherapy. We evaluated the clinicopathological factors and clinical outcomes and assessed radiographic response based on the RECIST criteria, not by central review.

RESULT

Before DCS chemotherapy, 18 patients had extra-regional lymph node metastasis, 5 had liver metastasis, 8 had macroscopic peritoneal metastasis, and 8 had pancreatic head invasion. Twenty-three (74.2%) of the 31 patients underwent R0 resection. Postoperative morbidity and mortality rates were 16.1 and 0%. During chemotherapy, grade 3/4 toxicities included neutropenia (54.8%), leukopenia (32.3%), and anemia (16.1%). Median progression-free survival and median overall survival (OS) were 42.1 and 56.1 months, respectively. These results were similar for all patients, except those with locally advanced disease alone. In the multivariate analysis for OS, ypN remained an independent negative prognostic factor (p = 0.018).

CONCLUSION

Surgical resection after DCS chemotherapy for initially unresectable gastric cancer was safe and provided a reasonable R0 resection rate and good mid-term survival.

S-1 plus nab-paclitaxel is a promising regimen for pancreatic cancer in a preclinical model

OBJECTIVES

The aim of this study was to investigate the efficacy and mechanism of action of combined S-1 and nab-paclitaxel in pancreatic cancer.

METHODS

Three human pancreatic cancer cell lines were treated with S-1, nab-paclitaxel, alone or in combination. Mice bearing subcutaneous xenograft of the cell line, PANC-1, were treated with the same drugs.

RESULTS

The growth-inhibitory effect of combined S-1 and nab-paclitaxel was greater than that of the individual drugs, and the combination index value indicated that S-1 and nab-paclitaxel had a synergistic effect in vitro. The combination of S-1 and nab-paclitaxel showed greater efficacy in vivo than monotherapy, and the growth-inhibitory effect was significantly greater when compared with the controls (P = 0.009), although no significant reduction in body weight was observed. Fractional tumor volume analysis indicated that the combination had a synergistic effect. Tumor stroma staining with α-smooth muscle actin was significantly decreased by nab-paclitaxel (P < 0.001) while the number of CD31-stained microvessel lumina was significantly increased by the combination therapy when compared with the control (P = 0.046).

CONCLUSIONS

S-1 and nab-paclitaxel had a synergetic effect in preclinical studies with good tolerability, and may play a role in stromal depletion and tumor angiogenesis. J. Surg. Oncol. 2016;113:413-419. © 2016 Wiley Periodicals, Inc.

Prognostic Impact of the ABCC11/MRP8 Polymorphism in Adjuvant Oral Chemotherapy with S-1 for Non-Small Cell Lung Cancer

Background: Postoperative 1-year administration of S-1, an oral derivative of 5-fluorouracil (5-FU), was shown to be feasible in lung cancer. The 5-year survival rates of postoperative patients treated with S-1 adjuvant chemotherapy and the prognostic impact of clinicopathological factors were examined. Methods: The data of 50 patients with curatively resected pathological stage IB to IIIA non-small cell lung cancer, who were treated with S-1 postoperatively, were analyzed. The prognostic impacts of 22 clinicopathological factors including expressions of the 5-FU pathway enzymes were evaluated. A single-nucleotide polymorphism (SNP), i.e. 538G>A (rs17822931), of ABCC11/MRP8, which encodes a 5-FU excretion enzyme that is known as an earwax type determinant, was also evaluated. Results: The 5-year overall and relapse-free survival rates were 72.5 and 67.5%, respectively. A performance status ≥1, lymphatic vessel invasion, blood vessel invasion, and the A/A type of SNP538, which is responsible for the dry earwax type, were significantly associated with shorter relapse-free survivals. In 34 patients who showed a relative performance of 70% or more for chemotherapy, multivariate survival analysis indicated significant hazard ratios only for the A/A type of SNP538 (p = 0.007). Conclusions: S-1 has sufficient power as adjuvant chemotherapy. However, its effect might be small in the dry earwax type patient group in an adjuvant setting.

Facile synthesis of gold nanorods/hydrogels core/shell nanospheres for pH and near-infrared-light induced release of 5-fluorouracil and chemo-photothermal therapy

We described a facile synthesis of pH and near-infrared (NIR) light dual-sensitive core/shell hybrid nanospheres, consisting of gold nanorods (GNR) as the core and poly(N-isopropylacrylamide-co-methacrylic acid) as the shell, p(NIPAM-MAA). The resultant GNR/p(NIPAM-MAA) nanospheres showed a core/shell structure, with an average diameter of ∼110nm and a strong longitudinal surface plasmon band at NIR region. Due to the photothermal effect of GNR and pH/thermal-sensitive volume transition of p(NIPAM-MAA) hydrogels, the nanospheres with loading of 5-fluorouracil (5-FU) by electrostatic interactions were developed as a smart carrier for pH- and photothermal-induced release of 5-FU. Experimental results testified that the cumulative release of 5-FU from nanospheres was markedly increased in a mild acidic medium. Moreover, a NIR light (808nm) irradiation triggered a greater and faster release of 5-FU, which was further testified by relevant results from in vitro cytotoxicity assay, in vivo tumor growth inhibition and histological images of ex vivo tumor sections. These results revealed significant applications of GNR/p(NIPAM-MAA) nanospheres in controlled release of anticancer agents and photothermal ablation therapy of tumor tissues, accompanied by synergistic effect of chem-photothermal therapy.

Supramolecular assemblies constructed from β-cyclodextrin-modified montmorillonite nanosheets as carriers for 5-fluorouracil

5-Fluorouracil-loaded supramolecular assemblies formed from self-assembling β-cyclodextrin modified montmorillonite nanosheets exhibit better antitumor activity and lower cytotoxicity in vitro.

Impact of the expression of thymidylate synthase and dihydropyrimidine dehydrogenase genes on survival in stage II/III gastric cancer

BACKGROUND

The efficacy of 5-fluorouracil (5FU)-based therapy, which remains the cornerstone of gastrointestinal cancer treatment, depends upon the expression of enzymes involved in pyrimidine metabolism, including thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyltransferase (OPRT). We analyzed the expression of these genes in patients enrolled in the Adjuvant Chemotherapy Trial of S-1 for Gastric Cancer (ACTS-GC) and their possible roles as biomarkers for treatment outcomes.

METHODS

Formalin-fixed, paraffin-embedded specimens were available for 829 of a total of 1,059 (78.3 %) patients. TS, DPD, TP, and OPRT expression was measured by RT-PCR in manually microdissected tumor specimens and normalized to the reference gene, β-actin. The expression level of each gene was categorized as low or high using cutoffs at the 33.3rd, 50th, or 66.7th percentiles.

RESULTS

The hazard ratio (HR) for overall survival (OS) after S-1 treatment versus surgery alone was significantly lower in high (>66.7th percentile; HR = 0.370; 95 % CI 0.221-0.619) compared to low (<66.7th percentile; HR = 0.757; 95 % CI 0.563-1.018) TS expression groups (P = 0.015). Similarly, the HR for OS after S-1 therapy versus surgery alone was significantly lower in high (>33.3rd percentile; HR = 0.520, 95 % CI 0.376-0.720) compared to low (<33.3rd percentile; HR = 0.848, 95 % CI 0.563-1.276) DPD expression groups (P = 0.065). There was no interaction between TP or OPRT expression and OS.

CONCLUSIONS

This large biomarker study showed that high TS and DPD gene expression in tumors was associated with enhanced benefit from postoperative adjuvant S-1 treatment in gastric cancer. There was no interaction between TP and OPRT expression and S-1 treatment.

S-1-based vs non-S-1-based chemotherapy in advanced gastric cancer: A meta-analysis

AIM: To assess the efficacy and tolerability of S-1-based vs non-S-1-based chemotherapy in advanced gastric cancer (AGC).

METHODS: We extracted reported endpoints, including overall survival (OS), progression-free survival (PFS), time-to-treatment failure (TTF), objective response rate (ORR) and adverse effects, from randomized controlled trials identified in PubMed, the Cochrane library, Science Direct, EMBASE and American Society of Clinical Oncology meetings. Stata software was used to calculate the pooled values.

RESULTS: Seven randomized controlled trials involving 2176 patients were included in this meta-analysis. Compared to non-S-1-based regimens, the use of S-1-based regimens were associated with an increase in ORR (RR = 1.300; 95%CI: 1.028-1.645); OS (HR = 0.89; 95%CI: 0.81-0.99; P = 0.025), TTF (HR = 0.83; 95%CI: 0.75-0.92; P = 0.000), and a lower risk of febrile neutropenia (RR = 0.225; P = 0.000) and stomatitis (RR = 0.230; P = 0.032). OS, PFS and TTF were prolonged, especially in the Asian population. In subgroup analysis, statistically significant increases in ORR (RR = 1.454; P = 0.029), OS (HR = 0.895; P = 0.041) and TTF (HR = 0.832; P = 0.000) were found when S-1-based chemotherapy was compared to 5-fluorouracil (5-FU)-based chemotherapy. The incidence of leukopenia (RR = 0.584; P = 0.002) and stomatitis (RR = 0.230; P = 0.032) was higher in the 5-FU-based arm. S-1-based regimens had no advantage in ORR, OS, PFS, TTF and grade 3 or 4 adverse events over capecitabine-based regimens.

CONCLUSION: S-1-based chemotherapy may be a good choice for AGC because of longer survival times, better tolerance and more convenient use.

Oral anticancer drugs: mechanisms of low bioavailability and strategies for improvement

The use of oral anticancer drugs has increased during the last decade, because of patient preference, lower costs, proven efficacy, lack of infusion-related inconveniences, and the opportunity to develop chronic treatment regimens. Oral administration of anticancer drugs is, however, often hampered by limited bioavailability of the drug, which is associated with a wide variability. Since most anticancer drugs have a narrow therapeutic window and are dosed at or close to the maximum tolerated dose, a wide variability in the bioavailability can have a negative impact on treatment outcome. This review discusses mechanisms of low bioavailability of oral anticancer drugs and strategies for improvement. The extent of oral bioavailability depends on many factors, including release of the drug from the pharmaceutical dosage form, a drug's stability in the gastrointestinal tract, factors affecting dissolution, the rate of passage through the gut wall, and the pre-systemic metabolism in the gut wall and liver. These factors are divided into pharmaceutical limitations, physiological endogenous limitations, and patient-specific limitations. There are several strategies to reduce or overcome these limitations. First, pharmaceutical adjustment of the formulation or the physicochemical characteristics of the drug can improve the dissolution rate and absorption. Second, pharmacological interventions by combining the drug with inhibitors of transporter proteins and/or pre-systemic metabolizing enzymes can overcome the physiological endogenous limitations. Third, chemical modification of a drug by synthesis of a derivative, salt form, or prodrug could enhance the bioavailability by improving the absorption and bypassing physiological endogenous limitations. Although the bioavailability can be enhanced by various strategies, the development of novel oral products with low solubility or cell membrane permeability remains cumbersome and is often unsuccessful. The main reasons are unacceptable variation in the bioavailability and high investment costs. Furthermore, novel oral anticancer drugs are frequently associated with toxic effects including unacceptable gastrointestinal adverse effects. Therefore, compliance is often suboptimal, which may negatively influence treatment outcome.

Role of S-1 in treatment of advanced gastric cancer

Gastric cancer is the fourth most common malignancy worldwide. More than 50% of gastric cancer patients have unresectable disease at diagnosis, and there is a high rate of local or distant recurrence, even in patients with an operable tumor. Chemotherapy is regarded as a significant and basic treatment that can provide a longer symptom-free period and improve quality of life. S-1 is a novel oral derivative of 5-FU. Compared with 5-FU, S-1 is more tolerable and effective, and will be more convenient to use for patients with advanced gastric cancer. Recent phase II randomized trials of S-1 based chemotherapy have achieved encouraging results with regard to objective response rate and overall survival. This paper aims to review the efficacy of S-1 in treating advanced gastric cancer, molecular markers that can predict efficacy, and the prospect for therapy with S-1 in combination with new chemotherapeutic drugs or molecularly targeted drugs.

A phase I study of neoadjuvant chemotherapy with gemcitabine plus oral S-1 for resectable pancreatic cancer

The aim of this study was to determine the maximum-tolerated dose (MTD), the dose-limiting toxicity (DLT) and the recommended dose (RD) of neoadjuvant chemotherapy (NAC) with gemcitabine (GEM) plus oral S-1 in patients with resectable pancreatic cancer. Thirteen patients with radiologically proven resectable pancreatic cancer were included in this study. S-1 was administered orally for 14 consecutive days, and GEM was administered on days 8 and 15 for two pre-operative cycles. The dose of S-1 in this study was planned with fixed doses of GEM (1,000 mg/m2): 20, 30 and 40 mg/day for levels 0, 1 and 2, respectively. Treatment was initiated at level 1 in 3 patients, while adverse events occurred in 2 patients during the second course, leading to a dose reduction to level 0 for the 8 remaining patients. Two of the 10 patients enrolled at level 0 were excluded. Of the remaining 8 patients, GEM administration was terminated due to DLT on day 15, during the first course in 3 patients, while level 0 dosage reached MTD. Surgery was performed for the remaining 11 patients included in the study. Post-operative complications included pancreatic fistulas in 5 patients and Pseudomonas aeruginosa sepsis in 1 patient. Two of the 11 patients exhibited a partial response and 9 patients stable disease. Eight of the 11 tumor specimens showed histopathological evidence of tumor cell injury. In conclusion, NAC with GEM and S-1 was not well-tolerated in this study. However, pre-operative chemotherapy may be effective against pancreatic cancer. Therefore, it is necessary to reconsider NAC regimens for pancreatic cancer.

Therapeutic enhancement of S-1 with CPT-11 through down-regulation of thymidylate synthase in bladder cancer

Thymidylate synthase (TS), a target enzyme of 5-fluorouracil (5-FU), is significantly associated with prognosis in various cancers. Recently, it has been reported that S-1, a novel 5-FU-based agent has an effect on bladder cancer. However, in cells with high TS level, S-1 did not have significant effects. Therefore, we examined whether down-regulation of TS enhanced effects of S-1 in them. First, we measured TS level in an aggressive bladder cancer cell line, KU-19-19 by enzyme-linked immunosorbent assay (ELISA) and evaluated its sensitivity to 5-FU using a small interfering RNA (siRNA) for TS. Next, we measured TS mRNA after exposure to various agents. Finally, we evaluated enhancement of cytotoxicity of S-1 by CPT-11 (7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin) which down-regulated TS in in vivo study. The median TS and dihydropyrimidine dehydrogenase (DPD) level was 53.3 ng/mg and 80.3 ng/mg in KU-19-19 cells, respectively. The 5-FU treatment in KU-19-19 cells transfected with siRNA for TS gene (TYMS) inhibited cell growth more significantly than that for nontargeting control. Down-regulation of TS was observed after exposure to SN-38 (7-ethyl-10-hydroxycamptothecin) in a dose-dependent manner. The combination treatment of 5-FU and SN-38 significantly inhibited cell growth, as compared to the single treatment. Meanwhile, in cells transfected with siRNA for TYMS, neither an additive nor a synergistic effect was observed. Also, combined S-1 and CPT-11 dramatically inhibited tumor growth, compared to S-1 or CPT-11 alone in in vivo study. In conclusion, CPT-11 down-regulated TS level and enhanced the effect of S-1. Thus, the combination therapy with S-1 and CPT-11 might be a novel modality for bladder cancer, even with high TS level.

This study confirmed that thymidylate synthase (TS) level in an aggressive human bladder cancer cell line, KU-19-19, was relatively higher than that in other cancer and presented that irinotecan (CPT-11) could down-regulate TS. Finally, the combination therapy with S-1 and CPT-11 resulted in significant tumor growth inhibition through down-regulation of TS in KU-19-19. Thus, combined S-1 and CPT-11 might be a novel treatment in bladder cancer, even with high TS.

Multicenter Phase II Study of a New Effective S-1 and Irinotecan Combination Schedule in Patients with Unresectable Metastatic or Recurrent Colorectal Cancer

INTRODUCTION

This multicenter phase II study determined the efficacy and safety of new daily oral S-1 and weekly irinotecan (CPT-11) combination schedule in patients with previously untreated advanced or recurrent colorectal cancer.

PATIENTS AND METHODS

Patients received first-line chemotherapy comprising S-1 80 mg/m(2)/day given on days 3 to 7, 10 to 14, and 17 to 21 and 60 mg/m(2) CPT-11 administered intravenously on days 1, 8, and 15 of a 28-day cycle.

RESULTS

A total of 45 eligible patients were enrolled in this study. The overall response rate was 48.9%. Median progression-free survival and median overall survival was 8.1 months and 20.9 months, respectively. The rates of grade 3 or 4 toxicity were as follows: neutropenia, 8.9%; anemia, 4.4%; anorexia, 6.7%; and diarrhea, 6.7%.

CONCLUSIONS

This new S-1 and irinotecan combination schedule appeared to be an effective, well-tolerated, and convenient regimen in patients with advanced colorectal cancer as compared with conventional regimens such as FOLFIRI and IRIS.

The upregulation of dihydropyrimidine dehydrogenase in liver is involved in acquired resistance to 5-fluorouracil

BACKGROUND

Acquired resistance to 5-fluorouracil (5-FU) is one of the important reasons for failure in 5-FU-based chemotherapy. The upregulation of dihydropyrimidine dehydrogenase (DPD) in tumours was reported as an important factor for acquired 5-FU resistance. The aim of this study is to examine whether intra-hepatic DPD was involved in acquired 5-FU resistance.

METHODS

HT-29 human colorectal xenograft tumours were established in nude mice. After long-term exposure to 5-FU, some of the tumour became "resistant" and the others remained "sensitive" to 5-FU. DPD expression levels in the livers and tumours of "resistant", "sensitive" or untreated mice were examined, and pharmacokinetics of 5-FU in rats' plasma were investigated. Gimeracil, a DPD inhibitor, was checked whether it could reverse the reduced bioavailability of 5-FU.

RESULTS

DPD expression was upregulated obviously in tumours of "resistant" mice as reported previously. Importantly, DPD expression was also upregulated significantly in livers of "resistant" mice, compared with those of "sensitive" or untreated mice. Furthermore, the upregulation of DPD expression in livers led to accelerated metabolism of 5-FU. Gimeracil was found to reverse the reduced serum 5-FU concentration. The cultured tumour cells from 5-FU treated mice showed relative sensitivity to higher concentration of 5-FU, even the "resistant" tumour cells.

CONCLUSION

Our study suggested that the upregulation of DPD in liver may be involved in acquired resistance to 5-FU, and DPD inhibitors or increasing 5-FU dosage may have potential application in overcoming 5-FU acquired resistance.

Prognostic significance of 5-fluorouracil metabolism-relating enzymes and enhanced chemosensitivity to 5-fluorouracil by 5-chloro 2,4-dihydroxy-pyridine in urothelial carcinoma

Background

Recently, S-1, a novel 5-fluorouracil (5-FU)-based agent containing the strong dihydropyrimidine dehydrogenase (DPD) inhibitor, 5-chloro-2,4-dihydropyrimidine (CDHP) has been clinically used to treat various non-urothelial carcinomas (UC). High levels of thymidylate synthase (TS), the target enzyme of 5-FU and DPD which degrades the majority of 5-FU, are associated with poor prognosis in some cancers. However, only a few reports have dealt with this in UC. The aim of this study was to investigate the clinical significance of TS and DPD in upper tract urothelial carcinoma (UTUC) and evaluate the role of TS and DPD on the sensitivity of 5-FU in UC cell lines and the anti-tumor effect of S-1 in UC xenograft model.

Methods

Firstly, we evaluated the immunohistochemical expression of TS and DPD in 176 patients with UTUC to determine their prognostic significance. Secondly, the levels of TS and DPD in UC cell lines were measured by ELISA and real-time PCR. Furthermore, the association between their levels and the sensitivity to 5-FU was examined using the small interfering RNA (siRNA) specific for TS and DPD. Thirdly, the anti-tumor effect of S-1 was evaluated in UC xenograft model.

Results

Immunohistochemical evaluation of TS and DPD in UTUC human samples revealed that TS expression was significantly associated with stage, grade, and lymphovascular invasion and DPD expression was significantly associated with grade. Multivariate analysis revealed that high TS expression was an independent predictor of disease-specific survival in them. In in vitro study using UC cell lines, high levels of TS and DPD were associated with low response to 5-FU and these associations were confirmed with siRNA specific for TS and DPD. In in vivo study using UC xenograft model, S-1 treatment dramatically inhibited tumor growth compared to controls, tegafur, or UFT in UC tumor with a high level of DPD.

Conclusions

TS plays an important role in the prognosis of UTUC and S-1 may be a key agent for UC tumor, especially with a high level of DPD.

Pilot study of neoadjuvant chemotherapy with gemcitabine and oral S-1 for resectable pancreatic cancer

Results of surgery alone for pancreatic cancer are disappointing. We retrospectively evaluated the efficacy and tolerability of neoadjuvant chemotherapy (NAC) with gemcitabine and oral S-1 in patients with potentially resectable pancreatic cancer. A total of 34 patients with pancreatic ductal adenocarcinoma, radiologically diagnosed preoperatively as having potentially resectable tumors, underwent pancreatic resection with lymphadenectomy at Kanazawa University Hospital. NAC was administered to 13 patients (NAC group). The remaining 21 patients were surgically treated without preoperative chemotherapy (control group). Surgical results were compared between these two groups, with follow-up for at least 24 months. No statistically significant differences were found in the clinicopathological background data (tumor location, age, gender, lymph node metastases, tumor stage and tumor size) between the NAC and control groups. Following preoperative chemotherapy, no patients were judged to be unable to undergo laparotomy, i.e., neither distant metastasis nor tumor progression was observed. Radiologically, all 13 NAC group patients had stable disease, whereas, histopathologically, all tumor specimens showed evidence of tumor cells. The treatment effect was judged by Evans grading to be grade IIa in 11 patients and grade IIb in 2 patients. Toxicity was evaluated in 11 patients. Grade III side effects were regarded as hematological toxicity, i.e., leucopenia (7.7%) and thrombocytopenia (15.4%). Moreover, the incidence of perioperative complications did not differ significantly between the NAC and control groups. The one- and three-year overall survival rates of the NAC group with pancreatic head cancer were 88.9 and 55.6%, respectively, superior to 88.9 and 29.6% in the control group (p=0.055). Therefore, NAC with gemcitabine and S-1 is well tolerated and potentially effective against pancreatic head cancer. A phase I study of NAC with gemcitabine and S-1 is under way in patients with resectable pancreatic cancer.

Substrate/Product-targeted NMR monitoring of pyrimidine catabolism and its inhibition by a clinical drug

We report the application of one-dimensional triple-resonance NMR to metabolic analysis and thereon-based evaluation of drug activity. Doubly (13)C/(15)N-labeled uracil ([(15)N1,(13)C6]-uracil) was prepared. Its catabolic (degradative) conversion to [(13)C3,(15)N4]-β-alanine and inhibition thereof by gimeracil, a clinical co-drug used with the antitumor agent 5-fluorouracil, in mouse liver lysates were monitored specifically using one-dimensional triple-resonance ((1)H-{(13)C-(15)N}) NMR, but not double-resonance ((1)H-{(13)C}) NMR, in a ratiometric manner. The administration of labeled uracil to a mouse resulted in its non-selective distribution in various organs, with efficient catabolism to labeled β-alanine exclusively in the liver. The co-administration of gimeracil inhibited the catabolic conversion of uracil in the liver. In marked contrast to in vitro results, however, gimeracil had practically no effect on the level of uracil in the liver. The potentiality of triple-resonance NMR in the analysis of in vivo pharmaceutical activity of drugs targeting particular metabolic reactions is discussed.

Dihydropyrimidine dehydrogenase (DPD) expression is negatively regulated by certain microRNAs in human lung tissues

Dihydropyrimidine dehydrogenase (DPD) is important to the antitumor effect of 5-fluorouracil (5-FU). DPD gene (DPYD) expression in tumors is correlated with sensitivity to 5-FU. Because the 5-FU accumulated in cancer cells is also rapidly converted into inactivated metabolites through catabolic pathways mediated by DPD, high DPD activity in cancer cells is an important determinant of the response to 5-FU. DPD activity is highly variable and reduced activity causes a high risk of 5-FU toxicity. Genetic variation in DPYD has been proposed as the main factor responsible for the variation in DPD activity. However, only a small proportion of the activity of DPD can be explained by DPYD mutations. In this study, we found that DPYD is a target of the following microRNAs (miRNA): miR-27a, miR-27b, miR-134, and miR-582-5p. In luciferase assays with HepG2 cells, the overexpression of these miRNAs was associated with significantly decreased reporter activity in a plasmid containing the 3'-UTR of DYPD mRNA. The level of DPD protein in MIAPaca-2 cells was also significantly decreased by the overexpression of these four miRNAs. The results suggest that miR-27a, miR-27b, miR-134, and miR-582-5p post-transcriptionally regulate DPD protein expression. The levels of miRNAs in normal lung tissue and lung tumors were compared; miR-27b and miR-134 levels were significantly lower in the tumors than normal tissue (3.64 ± 4.02 versus 9.75 ± 6.58 and 0.64 ± 0.75 versus 1.48 ± 1.39). DPD protein levels were significantly higher in the tumors. Thus, the decreased expression of miR-27b would be responsible for the high levels of DPD protein. This study is the first to show that miRNAs regulate the DPD protein, and provides new insight into 5-FU-based chemotherapy.

Impact of dihydropyrimidine dehydrogenase and γ-glutamyl hydrolase on the outcomes of patients treated with gemcitabine or S-1 as adjuvant chemotherapy for advanced pancreatic cancer

Gene expression analyses may play useful roles in determining the prognosis of cancer patients and in selecting antitumor drugs. This retrospective study examined potential prognostic factors in patients with pancreatic cancer who received adjuvant chemotherapy after surgery. The study group consisted of 79 patients who had received gemcitabine or S-1 as adjuvant chemotherapy for advanced pancreatic cancer. Using laser-captured microdissection and real-time RT-PCR assay, we quantitatively evaluated the mRNA levels of 10 genes associated with patient prognosis and sensitivity to chemotherapy using paraffin-embedded specimens of the primary tumors resected before the start of adjuvant chemotherapy. In univariate analyses, a low gene expression level of γ-glutamyl hydrolase (GGH) and a high gene expression level of folylpolyglutamate synthase correlated with a favorable outcome. In a multivariate analysis, a low gene expression level of dihydropyrimidine dehydrogenase (DPD) and GGH significantly correlated with outcome (hazard ratio of the high DPD group to the low DPD group: 5.55; 95% confidence interval (CI) 1.27-24.05; P=0.022; the high GGH group to the low GGH group: 3.77; 95% CI 1.04-13.79, P=0.043). For adjuvant chemotherapy of patients with pancreatic cancer, the mRNA level of DPD and GGH may affect the prognosis of these patients.

Relationship between gene expression of 5-fluorouracil metabolic enzymes and 5-fluorouracil sensitivity in primary cancer cells isolated from malignant ascites

This study was designed to investigate the predictive role of 5-FU metabolic enzymes in malignant ascites. Forty-three malignant ascites were collected and primary cancer cells were isolated. Gene expression was detected by quantitative RT-PCR. We found that DPD mRNA was higher in patients with pancreatic cancers than those with gastric cancers, colon cancers, and liver cancers. Significant correlations were found between expression of DPD and TP, and between TS and OPRT. mRNA levels of TS and OPRT correlated significantly with the chemosensitivity of 5-FU. Assessing gene expression would be useful in predicting 5-FU sensitivity for patients with malignant ascites.

The therapeutic efficacy of S-1 against orthotopically implanted human pleural mesothelioma cells in severe combined immunodeficient mice

Purpose

Malignant pleural mesothelioma (MPM) is a highly lethal neoplasm. S-1 has been developed as a novel oral antineoplastic agent based on the modulation of 5-fluorouracil (5-FU) bioactivity. This study was conducted to investigate the preclinical therapeutic effect of S-1 on MPM.

Methods

We used three human MPM cell lines, Y-MESO-14, NCI-H290 and MSTO-211H. In vitro proliferation of human MPM cells was determined by MTT assay. Human MPM cells were orthotopically implanted into thoracic cavity of SCID mice. Tumor-bearing mice were treated with S-1 or vehicle.

Results

The combination of 5-FU and 5-chloro-2,4-dihydroxypyridine (CDHP) was more effective than 5-FU alone in inhibiting MPM cell proliferation in vitro. This combination was most effective in Y-MESO-14 cells, which co-expressed high protein level of dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP). In vivo data showed that treatment with S-1 significantly reduced thoracic tumors and pleural effusion produced by Y-MESO-14 cells. Moreover, treatment with S-1 prolonged the survival of Y-MESO-14 cell-bearing SCID mice.

Conclusions

We demonstrated that S-1 was effective for inhibiting the proliferation of MPM cells, particularly with both DPD and TP expressions, suggesting that S-1 might be therapeutically effective for control of MPM.

Spectrofluorimetric determination of 5-fluorouracil by fluorescence quenching of 9-anthracenecarboxylic acid

Photo-induced intermolecular electron transfer (PET) interaction between excited singlet (S(1)) state of 9-anthracene carboxylic acid (9-ANCA) and DNA bases of pyrimidines as uracil and 5-fluorouracil (5-FU) has been studied in water and ethanol solutions using steady-state fluorescence spectroscopy. The intensity of all emission bands of 9-ANCA was quenched in presence of uracil and 5-FU by electron transfer reaction without formation of an exciplex. It was found that uracil and 5-fluorouracil acts as effective electron donors and simultaneously quench the fluorescence of electron-accepting sensitizer 9-ANCA. The quenching by diffusion-controlled rate coincides well with the dynamic Stern-Volmer correlation. The bimolecular quenching rate constant (k(q)(ss)) and electron transfer rate constant (k(et)) observed are seen to be much higher for 5-fluorouracil than those for uracil. The thermodynamic parameters estimated by using the Rehm-Weller equation were used to propose a suitable mechanism for PET occurring between uracils and 9-ANCA. The proposed method was used to determine 5-fluorouracil from pharmaceutical samples with satisfactory results. The technique is more selective, sensitive and relatively free from coexisting substances.

An orthotopic implantation mouse model of human malignant pleural mesothelioma for in vivo photon counting analysis and evaluation of the effect of S-1 therapy

Human malignant pleural mesothelioma (HMPM) is an aggressive neoplasm that is highly resistant to conventional therapies. We established 3 HMPM cell lines (TCC-MESO-1, TCC-MESO-2 and TCC-MESO-3) from Japanese patients; the first 2 from the primary and metastatic tumors of a patient with the epithelioid type of HMPM, and the third from a patient with biphasic characteristics of the tumor (epithelioid and sarcomatous phenotypes). The 3 cell lines resembled the original HMPMs in their morphological and biological features, including the genetic alterations such as lack of p16 expression and mutation of p53. Their tumorigenicity was determined in SCID mice by orthotopic implantation (20-46%). The tumorigenicity of the HMPM cell lines, which was relatively low, was enhanced by repeated subcultures and orthotopic implantations, and 3 competent tumorigenic sublines were produced (Me1Tu, Me2Tu and Me3Tu sublines from the TCC-MESO-1, TCC-MESO-2 and TCC-MESO-3 cell lines, respectively). The resultant HMPM sublines efficiently generated tumors in the SCID mice (100%) following orthotopic implantation. SCID mice implanted with the competent sublines, into one of which the luciferase gene was introduced, displayed quantitative fluctuation of the bioluminescence for the tumor volume in vivo. Oral administration of S-1, an anticancer agent, suppressed the proliferation of the luciferase gene-expressing Me1Tu subline in the mouse models in vivo, with a treated-to-control ratio of the mean tumor volume of 0.2. The orthotopic implantation mouse model proved to be useful for quantitative evaluation of the efficacy of novel anticancer drugs and also for studying the biology of HMPMs in vivo.

EUS-guided in vivo microdialysis of the pancreas: a novel technique with potential diagnostic and therapeutic application

BACKGROUND

Microdialysis has been used in vivo to measure dynamic temporal variations in extracellular or interstitial concentrations of non-protein-bound substances that are unstable in the systemic circulation.

OBJECTIVE

To evaluate the technical feasibility and possible complications of EUS-guided in vivo microdialysis of the pancreas.

DESIGN AND INTERVENTION

Under the guidance of an echoendoscope inserted into the stomach of each dog, the pancreatic parenchyma was punctured by using a 19-gauge needle. A specially developed microdialysis probe threaded through the lumen of the 19-gauge needle was positioned in the pancreas. The probe was constantly perfused with saline solution at a flow rate of 1.0 microL/minute.

SETTING

Experiments on 8 beagle dogs.

MAIN OUTCOME MEASUREMENTS

The concentration of 5-fluorouracil (5-FU) in the microdialysate was measured at 10-minute intervals, once before and for 8 times after a single (20 mg/kg) bolus intravenous infusion of 5-FU.

RESULTS

Following the administration of 5-FU, the concentration of 5-FU in all macrodialysate samples exceeded the cut-off value by more than 100-fold. The 5-FU levels in the microdialysate increased rapidly, peaked by 10 minutes (13.9 microg/mL), and gradually declined thereafter. No local bleeding or accumulation of fluid around the pancreas was observed.

LIMITATION

Sampling was unsuccessful in 2 of the 8 dogs because the probe broke while being inserted into the pancreatic parenchyma.

CONCLUSION

EUS-guided pancreatic microdialysis is feasible and has multiple potential clinical/therapeutic applications, including monitoring pharmacokinetics focally and detecting novel biomarkers that are unstable or undetectable in the plasma.

Impacts of fluorouracil-metabolizing enzymes on the outcomes of patients treated with S-1 alone or S-1 plus cisplatin for first-line treatment of advanced gastric cancer

A phase III trial of S-1 plus cisplatin (SP) versus S-1 alone, for first-line treatment of advanced gastric cancer (SPIRITS trial), has shown that overall survival was better in patients treated with SP than with S-1 alone. In the present retrospective biomarker study, we aimed to develop a methodology to identify the patients with advanced gastric cancer who would respond better to S-1 alone than SP. We studied 120 patients who received S-1 alone or SP for first-line chemotherapy for advanced gastric cancer, and quantitatively evaluated mRNA levels of thymidylate synthase (TS), thymidine phosphorylase (TP), orotate phosphoribosyltransferase (OPRT), dihydropyrimidine dehydrogenase, vascular endothelial growth factor-A, and epidermal growth factor receptor in paraffin-embedded specimens of primary tumors. Multivariate survival analysis in patients who received S-1 monotherapy (66 patients) demonstrated that low TP expression (hazard ratio: 2.55 (95% CI: (1.33 to 4.89)), low TS (2.71 (1.36 to 5.37)), and high OPRT (0.33 (0.13 to 0.86)) were significant predictors of long overall survival. In patients with lower expression of both TP and TS (n = 23) than their cutoff values, the S-1 alone group (n = 15) had longer overall survival than the SP group (n = 8; median overall survival, 18.2 months vs. 9.4 months), whereas the frequency of overall adverse events in the S-1 alone group tended to be lower than that in SP group. Our results suggest that these biomarkers are useful for selection of patients with advanced gastric cancer in whom treatment with S-1 alone will yield survival benefit.

Clinical relevance of thymidylate synthase (TS) activity for S-1-based chemotherapy in squamous cell carcinoma of the oral cavity

S-1 is a newly developed oral fluoropyrimidine derivative that is now widely used as a chemotherapeutic agent in the treatment of oral squamous cell carcinoma (SCC). Thymidylate synthase (TS) is the rate-limiting enzyme in the de novo DNA biosynthetic pathway, and improves clinical response to chemotherapy with fluoropyrimidines. We have retrospectively evaluated the predictive value of thymidylate synthase activity in 75 patients with oral SCC with an enzyme-linked immunosorbent assay (ELISA). Mean (SD) activity (pmol/mg) in the specimens was 0.078 (0.080) (median 0.059). The median value was taken as the cut-off value based on which the patients were divided into high and low activity groups. Both the clinical and histopathological responses to chemotherapy and radiochemotherapy were higher in the group with low TS activity. The group with low TS activity also differed significantly in their clinical response to S-1-based chemotherapy (p<0.05). However, there was no significant difference in cause-specific survival. Measurement of TS activity may aid in predicting the clinical response to chemotherapy including S-1 for oral SCC.

High intratumoral dihydropyrimidine dehydrogenase mRNA levels in pancreatic cancer associated with a high rate of response to S-1

PURPOSE

Although the prognosis in patients with pancreatic cancer has been poor, we recently reported unusually high response rate and survival benefit of S-1 treatment in patients with pancreatic cancer. The aim of this study was to reveal genetic background of this unique activity of S-1 against pancreatic cancer. S-1 is a novel oral fluoropyrimidine derivative consisting of Tegafur (FT) and dihydropyrimidine dehydrogenase (DPD) inhibitor (5-chloro-2,4-dihydroxypyridine; CDHP). Accordingly, intratumoral DPD mRNA expression level was measured to reveal whether the level in pancreatic cancer was different from other GI cancer and whether it was relevant to chemosensitivity.

METHODS

Thirty-three recurrent pancreatic cancer patients treated with S-1 were studied. We obtained 15 responders and 13 non-responders according to the change of serum CA19-9. The mRNA was extracted from paraffin-embedded surgical specimens using laser captured microdissection, and relative expression levels of each DPD/beta-actin were measured using a quantitative reverse transcription polymerase chain reaction (RT-PCR) (Taqman) system. Forty-four colorectal cancer patients and 20 gastric cancer patients treated with S-1 were enrolled as control groups. Thymidylate synthase (TS) mRNA expression levels were also measured.

RESULTS

Intratumoral DPD mRNA expression level was significantly higher in pancreatic cancer than that in colorectal cancer (P = 0.0003; median level, 1.38 vs. 0.44) and gastric cancer (P = 0.0061; 1.38 vs. 0.82). No difference in TS mRNA expression levels was observed among cancer types. DPD expression among responded pancreatic cancer was significantly lower than non-responded. (P = 0.012, Mann-Whitney U test).

CONCLUSIONS

Intratumoral DPD mRNA expression level in pancreatic cancer was significantly higher than the other malignancies. This result may elucidate possible reasons for the high effectiveness of S-1 in pancreatic cancer.

Orotate phosphoribosyltransferase expression level in tumors is a potential determinant of the efficacy of 5-fluorouracil

Although the intratumoral expression levels of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) are known to affect the antitumor activity of 5-fluorouracil (5-FU), the importance of orotate phosphoribosyltransferase (OPRT) has remained unclear. This study investigated the relationship between intratumoral OPRT expression and the antitumor activity of 5-FU using human NCI60 cell lines with similar levels of TS and DPD messenger RNAs, as well as 31 tumor xenografts. The OPRT mRNA level was positively correlated with the 5-FU efficacy in these cell lines. In vitro, the 50% growth-inhibitory concentrations of 5-FU were closely correlated with the OPRT mRNA levels in cancer cell lines with similar levels of TS mRNAs when combined with a DPD inhibitor. Moreover, downregulation of OPRT with small-interfering RNA decreased the sensitivities of the cultured tumor cells to 5-FU. These results suggest that the OPRT expression level in tumors is an additional determinant of the efficacy of 5-FU.

Involvement of up-regulation of hepatic breast cancer resistance protein in decreased plasma concentration of 7-ethyl-10-hydroxycamptothecin (SN-38) by coadministration of S-1 in rats

The safety and efficacy of combination therapy with 7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin (CPT-11, irinotecan) and S-1 composed of tegafur, a prodrug of 5-fluorouracil, gimeracil, and potassium oxonate, have been confirmed in patients with colorectal cancer. Previously, we showed that p.o. coadministration of S-1 decreased the plasma concentration of both CPT-11 and its metabolites in a patient with advanced colorectal cancer. The aim of this study was to clarify the mechanism of drug interaction using both in vivo and in vitro methods. Rats were administered S-1 p.o. (10 mg/kg) once a day for 7 consecutive days. On day 7, CPT-11 (10 mg/kg) was administered by i.v. injection. Coadministration of S-1 affected the pharmacokinetic behavior of CPT-11 and its metabolites, with a decrease in the C(max) and area under the plasma concentration curve (AUC) of the active metabolite 7-ethyl-10-hydroxycampothecin (SN-38) lactone form. Furthermore, the rate of biliary excretion of the SN-38 carboxylate form increased on coadministration of S-1. In the liver, the level of breast cancer resistance protein (BCRP), but not P-glycoprotein and multidrug resistance-associated protein 2, was elevated after administration of S-1. Enzymatic conversion of CPT-11 to SN-38 by carboxylesterase (CES) was unaffected by the liver microsomes of rats treated with S-1. In addition, components of S-1 did not inhibit the hydrolysis of p-nitrophenylacetate, a substrate of CES, in the S9 fraction of HepG2 cells. Therefore, the mechanism of drug interaction between CPT-11 and S-1 appears to involve up-regulation of BCRP in the liver, resulting in an increased rate of biliary excretion of SN-38 accompanied by a decrease in the C(max) and AUC of SN-38.