Combinatorial Antitumor Activity of Oxaliplatin with Epigenetic Modifying Agents, 5-Aza-CdR and FK228, in Human Gastric Cancer Cells

Epigenetic silencing is considered to be a major mechanism for loss of activity in tumor suppressors. Reversal of epigenetic silencing by using inhibitors of DNA methyltransferase (DNMT) or histone deacetylases (HDACs) such as 5-Aza-CdR and FK228 has shown to enhance cytotoxic activities of several anticancer agents. This study aims to assess the combinatorial effects of gene-silencing reversal agents (5-Aza-CdR and FK228) and oxaliplatin in gastric cancer cells, i.e., Epstein-Barr virus (EBV)-negative SNU-638 and EBV-positive SNU-719 cells. The doublet combinatorial treatment of 5-Aza-CdR and FK228 exhibited synergistic effects in both cell lines, and this was further corroborated by Zta expression induction in SNU-719 cells. Three drug combinations as 5-Aza-CdR/FK228 followed by oxaliplatin, however, resulted in antagonistic effects in both cell lines. Simultaneous treatment with FK228 and oxaliplatin induced synergistic and additive effects in SNU-638 and SNU-719 cells, respectively. Three drug combinations as 5-Aza-CdR prior to FK228/oxaliplatin, however, again resulted in antagonistic effects in both cell lines. This work demonstrated that efficacy of doublet synergistic combination using DNMT or HDACs inhibitors can be compromised by adding the third drug in pre- or post-treatment approach in gastric cancer cells. This implies that the development of clinical trial protocols for triplet combinations using gene-silencing reversal agents should be carefully evaluated in light of their potential antagonistic effects.

microRNA-200a-3p increases 5-fluorouracil resistance by regulating dual specificity phosphatase 6 expression

Acquisition of resistance to anti-cancer drugs is a significant obstacle to effective cancer treatment. Although several efforts have been made to overcome drug resistance in cancer cells, the detailed mechanisms have not been fully elucidated. Here, we investigated whether microRNAs (miRNAs) function as pivotal regulators in the acquisition of anti-cancer drug resistance to 5-fluorouracil (5-FU). A survey using a lentivirus library containing 572 precursor miRNAs revealed that five miRNAs promoted cell survival after 5-FU treatment in human hepatocellular carcinoma Hep3B cells. Among the five different clones, the clone expressing miR-200a-3p (Hep3B-miR-200a-3p) was further characterized as a 5-FU-resistant cell line. The cell viability and growth rate of Hep3B-miR-200a-3p cells were higher than those of control cells after 5-FU treatment. Ectopic expression of a miR-200a-3p mimic increased, while inhibition of miR-200a-3p downregulated, cell viability in response to 5-FU, doxorubicin, and CDDP (cisplatin). We also showed that dual-specificity phosphatase 6 (DUSP6) is a novel target of miR-200a-3p and regulates resistance to 5-FU. Ectopic expression of DUSP6 mitigated the pro-survival effects of miR-200a-3p. Taken together, these results lead us to propose that miR-200a-3p enhances anti-cancer drug resistance by decreasing DUSP6 expression.

Impact of Micellar Vehicles on in situ Intestinal Absorption Properties of Beta-Lapachone in Rats

The aim of the present study was to examine the effect of micellar systems on the absorption of beta-lapachone (b-lap) through different intestinal segments using a single-pass rat intestinal perfusion technique. B-lap was solubilized in mixed micelles composed of phosphatidylcholine and sodium deoxycholate, and in sodium lauryl sulfate (SLS)-based conventional micelles. Both mixed micelles and SLS micelles improved the in situ permeability of b-lap in all intestinal segments tested although the mixed micellar formulation was more effective in increasing the intestinal absorption of b-lap. The permeability of b-lap was greatest in the large intestinal segments. Compared with SLS micelles, the effective permeability coefficient values measured with mixed micelles were 5- to 23-fold higher depending on the intestinal segment. Our data suggest that b-lap should be delivered to the large intestine using a mixed micellar system for improved absorption.

Development of Estimation Methods of Skin Oxidation and Evaluation of Anti-Oxidative Effects of Genistein in Topical Formulations

The objective of the present study was to establish the method of measurement of hydrogen peroxide and to estimate the anti-oxidative effect of genistein in the skin. UVB induced skin oxidation and anti-oxidative effect of genistein formulations were evaluated by determining levels of hydrogen peroxide. The mechanism involved in the determination of hydrogen peroxide is based on a color reaction between ferric ion (Fe3+) and xylenol orange, often called FOX assay and subsequent monitoring of absorbance values of the reactant at 540 nm. The reaction was to some extent pH-dependent and detection sensitivity was greatest at pH 1.75. Genistein liposomal gel demonstrated better anti-oxidative effect with regard to lowering hydrogen peroxide levels elevated by UVB irradiation compared to genistein-suspended gel. A linear relationship has been observed between anti-oxidative effect of genistein and drug deposition in the skin tissue. Genistein liposomal gel resulting in the localization of the drug in the deeper skin led to improved anti-oxidative effect compared to genistein gel. The suggested method for evaluation of oxidation of the skin can be used as a tool to screen effective anti-oxidative agents and their delivery systems acting on the skin.

Clinical Pharmacokinetics of Tegafur Administered with Epirubicin and Cisplatin in Patients with Advanced Gastric Cancer / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Tegafur, an oral prodrug of 5-fluorouracil (5-FU), has been used in the treatment of gastric cancers. UFT (tegafur + uracil) has been developed to enhance the efficacy of tegafur. This study was conducted to assess the pharmacokinetics (PK) of tegafur in gastric cancer patients given the ECU-E regimen (epirubicin, cisplatin, UFT-E, an enteric-coated formula of UFT). A preliminary evaluation of antitumor efficacy and toxicity of ECU-E regimen was also performed. MATERIALS AND METHODS: Of the 32 gastric cancer patients registered for the ECU-E regimen, 8 participated in the PK study. The plasma concentration of tegafur was determined using HPLC. RESULTS: Seven out of the 8 patients were evaluable for response after 2 cycles, and showed 3 partial responses, 1 stable disease and 3 progressive diseases. No major toxicities were observed. Plasma profiles of the tegafur after the first dose showed significant differences in the amount and rate of absorption, i.e., rapid absorption group vs. slow absorption group. The level of C(max) in the rapid absorption group was 1.8 fold higher, and the AUC(0-5h) 4 fold greater, than those in the slow absorption group, nonetheless, the steady state concentrations showed no significant difference. These data indicate that the different absorption rates may not affect the overall exposure to tegafur. The patients with low Cp(ss, peak) showed poor efficacy compared to those with high Cp(ss, peak), suggesting that the concentration of tegafur may be one of the pharmacodynamic determinants in patients administered with ECU-E. CONCLUSION: This study evaluated the pharmacokinetics of tegafur in gastric patients given the ECU-E regimen, and provides preliminary data on the relationship between the plasma tegafur level and the efficacy, which warrants further evaluation.

Antitumor Activity of Oxaliplatin, 5-FU and Paclitaxel Given Alone or in Combination with ZD1839 in Human Gastric Carcinoma Cells in vitro / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Oxaliplatin (LOHP), 5-FU, and paclitaxel (PTX) are considered highly active against advanced gastric carcinomas, and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, ZD1839 is considered as a good candidate for the treatment of gastric cancers when given alone or in combination with cytotoxic agents. The present study evaluated the antitumor effects of these agents in SNU-1 human gastric cancer cells either alone or when given as a doublet (i.e., as a cytotoxic-cytostatic combination). MATERIALS AND METHODS: We selected SNU-1 cells that showed DNA mismatch repair (MMR) deficiency and EGFR overexpression. Growth inhibition was measured by MTT and by direct cell counting and cell cycle distribution by flow cytometry. The combination index (CI) was used to describe synergistic interaction. RESULTS: The four drugs showed IC50s ranging from 1.81 nM to 13.2microM. MTT assay appeared to underestimate the cytotoxicity of PTX, which was attributed to a significant resistant fraction (32%). LOHP and PTX induced G2/M arrest, 5-FU increased in S phase, and ZD1839 in-creased in G1 in a concentration dependent manner. PTX ZD1839 showed the greatest synergism and LOHP ZD1839 showed a similar result. The cell cycle effect of PTX was potentiated by the coadministration of ZD1839. A previously developed cytostatic TPi model was used to assess the contribution of cell cycle arrest to overall growth inhibition, and 64% and 80% of the overall growth inhibition was attributed to cell cycle arrest for LOHP and PTX, when exposed to 7.55microM and 10 nM for 72 hr, respectively. CONCLUSION: This study demonstrates the antitumor activity and significant cell cycle arrest effect of ZD1839 against human gastric carcinoma cells and its synergistic interaction with LOHP and PTX. These results provide a preclinical rationale for the clinical development of ZD1839 and its use in combination with LOHP or PTX against human gastric cancers that express EGFR.