A long non-coding RNA snaR contributes to 5-fluorouracil resistance in human colon cancer cells

Several types of genetic and epigenetic regulation have been implicated in the development of drug resistance, one significant challenge for cancer therapy. Although changes in the expression of non-coding RNA are also responsible for drug resistance, the specific identities and roles of them remain to be elucidated. Long non-coding RNAs (lncRNAs) are a type of ncRNA (> 200 nt) that influence the regulation of gene expression in various ways. In this study, we aimed to identify differentially expressed lncRNAs in 5-fluorouracil-resistant colon cancer cells. Using two pairs of 5-FU-resistant cells derived from the human colon cancer cell lines SNU-C4 and SNU-C5, we analyzed the expression of 90 lncRNAs by qPCR-based profiling and found that 19 and 23 lncRNAs were differentially expressed in SNU-C4R and SNU-C5R cells, respectively. We confirmed that snaR and BACE1AS were downregulated in resistant cells. To further investigate the effects of snaR on cell growth, cell viability and cell cycle were analyzed after transfection of siRNAs targeting snaR. Down-regulation of snaR decreased cell death after 5-FU treatment, which indicates that snaR loss decreases in vitro sensitivity to 5-FU. Our results provide an important insight into the involvement of lncRNAs in 5-FU resistance in colon cancer cells.

Injectable poly(organophosphazene) hydrogel system for effective paclitaxel and doxorubicin combination therapy

Combination therapy is an important option for gastric cancer which is the second leading cause of cancer-related death worldwide. The administration schedule of cell cycle-specific drugs, such as doxorubicin (DOX) and paclitaxel (PTX), is important for therapeutic efficacy. However, to control the schedule is clinically inconvenient. Additionally, in vitro cytotoxicity tests against human gastric cancer cells (SNU-601) showed that the combination indices (CIs) of DOX and PTX were 1.43 (α=0) and 1.90 (α=1), respectively, indicating that the DOX and PTX interaction was antagonistic. Thus, based on the finding that the release rate of drugs from poly(organophosphazene) (PPZ) hydrogel is dependent on the hydrophobicity of the drugs, we used injectable PPZ hydrogel in combination therapy. In vivo anticancer activity test in human gastric cancer cell-xenografted mice showed that intratumoral injection with aqueous PPZ solution, containing DOX (15 mg/kg) and PTX (30 mg/kg), resulted in the highest tumor inhibition and safety (no mortality for approximately 3 months) in the experimental groups. Consequently, PPZ hydrogel is expected to be a promising drug delivery system for cell cycle-specific drugs, facilitating the control of their administration schedule for effective combination therapy.

Application of concave microwells to pancreatic tumor spheroids enabling anticancer drug evaluation in a clinically relevant drug resistance model

Intrinsic drug resistance of pancreatic ductal adenocarcinoma (PDAC) warrants studies using models that are more clinically relevant for identifying novel resistance mechanisms as well as for drug development. Tumor spheroids (TS) mimic in vivo tumor conditions associated with multicellular resistance and represent a promising model for efficient drug screening, however, pancreatic cancer cells often fail to form spheroids using conventional methods such as liquid overlay. This study describes the induction of TS of human pancreatic cancer cells (Panc-1, Aspc-1, Capan-2) in concave polydimethylsiloxane (PDMS) microwell plates and evaluation of their usefulness as an anticancer efficacy test model. All three cell lines showed TS formation with varying degree of necrosis inside TS. Among these, Panc-1 spheroid with spherical morphology, a rather rough surface, and unique adhesion structures were successfully produced with no notable necrosis in concave microwell plates. Panc-1 TS contained growth factors or enzymes such as TGF-β1, CTGF, and MT1-MMP, and extracellular matrix proteins such as collagen type I, fibronectin, and laminin. Panc-1 cells grown as TS showed changes in stem cell populations and in expression levels of miRNAs that may play roles in chemoresistance. Visualization of drug penetration and detection of viability indicators, such as Ki-67 and MitoSOX, were optimized for TS for quantitative analysis. Water-soluble tetrazolium (MTS) and acid phosphatase (APH) assays were also successfully optimized. Overall, we demonstrated that concave PDMS microwell plates are a novel platform for preparation of TS of weakly aggregating cells and that Panc-1 spheroids may represent a novel three-dimensional model for anti-pancreatic cancer drug screening.

Intratumoral delivery of paclitaxel using a thermosensitive hydrogel in human tumor xenografts

Poly(organophosphazene), a novel thermosensitive hydrogel, is an injectable drug delivery system (DDS) that transforms from sol to gel at body temperature. Paclitaxel (PTX) is a mitotic inhibitor used in the treatment of various solid tumors. Due to its poor solubility in water and efflux systems in the gastrointestinal tract, PTX is a good candidate for local DDS. Here, we evaluated the penetration kinetics of PTX released from the PTX-poly(organophosphazene) hydrogel mixture in multicellular layers (MCLs) of human cancer cells. We also investigated the tumor pharmacokinetics of PTX (60 mg/kg) when administered as an intratumoral injection using poly(organophosphazene) in mice with human tumor xenografts. When PTX was formulated at 0.6 % w/w into a 10 % w/w hydrogel, the in vitro and in vivo release were found to be 40 and 90 % of the dose, respectively, in a sustained manner over 4 weeks. Exposure of MCLs to PTX-hydrogel showed time-dependent drug penetration and accumulation. In mice, the hydrogel mass was well retained over 6 weeks, and the PTX concentration in the tumor tissue was maximal at 14 days, which rapidly decreased and coincided with rebound tumor growth after 14 days of suppression. These data indicate that PTX-hydrogel should be intratumorally injected every 14 days, or drug release duration should be prolonged in order to achieve a long-term antitumor effect. Overall, poly(organophosphazene) represents a novel thermosensitive DDS for intratumoral delivery of PTX, which can accommodate a large dose of the drug in addition to reducing its systemic exposure by restricting biodistribution to tumor tissue alone.

Abstract 2722: Characteristics of pancreatic cancer spheroids as a model for anticancer efficacy test

Compared to the conventional monolayers or suspension cultures, 3D culture models have drawn attention as a vivo-mimic model which can produce clinically relevant data. Among the several types of 3D culture models, multicellular spheroid (MCS) is a appropriate model for study of penetration and efficacy of anticancer agents. Purpose of this study was to establish MCS of human pancreatic cancer cell (Panc-1) and evaluate its usefulness as anticancer efficacy test. Panc-1 MCS was produced successfully by using poly-dimethylsiloxane(PDMS) microwell instead of agarose-coated 96-well system. MCS with average diameter of 375 μm was prepared in 700 μm microwells after 4 days of culture. Spherical morphology with rather rough surface and junctional structures in outer cell layers were observed with no notable necrotic area. Extracellular matrix proteins such as collagen I, fibronectin, and laminin were detected in the interstitial space of MCS. Stem cell population with CD44+/CD24+/ESA+ expression increased from 0.1% to 2.1% when cultured as MCS. miRNA expression profiling showed a difference between monolayers and MCS, i.e., 36 and 85 genes were up- and down-regulated in MCS, respectively. Imaging of drug penetration and viability indicators including MitoSOX, Edu incorporation, and Ki-67 expression were optimized for microwell format. Colorimetric assays of MTS and APH were performed after transferring MCS to 96-well plates. Overall, we demonstrated that PDMS microwell is an appropriate platform for preparation of MCS of Panc-1 cells and MCS showed different biological features from monolayers, suggesting that Panc-1 MCS prepared using PDMS microwell may be a useful 3D model for anticancer efficacy test.

Citation Format: Sang-Eun Yeon, Sang-Hoon Lee, Hyo-Jeong Kuh. Characteristics of pancreatic cancer spheroids as a model for anticancer efficacy test. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2722. doi:10.1158/1538-7445.AM2013-2722

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

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 self-microemulsifying bilayer tablets for pH-independent fast release of candesartan cilexetil

The aim of this study was to design self-microemulsifying tablets for pH-independent fast release of poorly soluble candesartan cilexetil (CDC). To improve the solubility of CDC, a self-microemulsifying drug delivery system (SMEDDS) was prepared composed of Capryol 90, Tween 80 and tetraglycol at a ratio of 5:35:60. Drug containing SMEDDS was adsorbed onto Fujicalin and Neusilin UFL2, respectively, used as solidification carriers and subsequently compressed into tablets (self-microemulsifying tablet, SMET). SMET using Fujicalin exhibited immediate CDC release in pH 1.2 medium while Neusilin UFL2-based SMET showed fast release, especially at pH 6.5. Thus, optimized SMET could be produced with one layer of Fujicalin and the other layer with Neusilin UFL2, demonstrating CDC release of 75% of the initial dose within 15 min in all pH conditions (1.2, 4.5, and 6.5). The average diameter of emulsion droplets formed from SMET was less than 200 nm. It was thus expected that Fujicalin and Neusilin UFL2-based bi-layer SMET would overcome low oral bioavailability of CDC due to its limited solubility at physiological pH conditions in the gastrointestinal tract.

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.

Abstract 5708: Interstitial protein delivery evaluated in multicellular layers model

The limited efficacy of protein drugs is related to their poor distribution in tumor tissue. We examined interstitial delivery of four model proteins of different molecular size and bioaffinity as formulated of non-formulated forms in multicellular layers (MCL) of human cancer cells. Model proteins were tumor necrosis factor-related apoptosis-including ligand (TRAIL), cetuximab, RNase A, and IgG. MCLs were cultured in Transwell inserts, exposed to drugs, then cryo-sectioned for image acquisition using fluorescence microscopy (fluorescent dye-labeled TRAIL, RNase A, IgG) or Immunohistochemistry (cetuximab). TRAIL and cetuximab showed partial penetration into MCLs, whereas RNase A and IgG showed little penetration. At 10-fold higher dose, a significant increase in penetration was observed for IgG only, while cetuximab showed an intense accumulation limited to the front layers. PEGylated TRAIL and a heparin-Pluronic nanogel formulation of RNase A showed significantly improved penetration that was attributed to increased stability and extracellular matrix binding, respectively. IgG penetration was significantly enhanced with PTX pretreatment as a penetration enhancer. MCL culture was successfully used for the evaluation of protein movement in the tumor interstitum. Four proteins showed limited interstitial penetration in MCL cultures. Bioaffinity, rather than molecular size, seems to have a positive effect on tissue penetration, although strong binding affinity may lead to sequestration in the front layers. Nanoformulations, such as PEGylation and heparin-Pluronic (HP) nanogel, or penetration enhancers are potential strategies to increase interstitial delivery of anticancer biologics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5708. doi:1538-7445.AM2012-5708

Evaluation of interstitial protein delivery in multicellular layers model

The limited efficacy of anticancer protein drugs is related to their poor distribution in tumor tissue. We examined interstitial delivery of four model proteins of different molecular size and bioaffinity in multicellular layers (MCL) of human cancer cells. Model proteins were tumor necrosis factor-related apoptosis-including ligand (TRAIL), cetuximab, RNase A, and IgG. MCLs were cultured in Transwell inserts, exposed to drugs, then cryo-sectioned for image acquisition using fluorescence microscopy (fluorescent dye-labeled TRAIL, RNase A, IgG) or immunohistochemistry (cetuximab). TRAIL and cetuximab showed partial penetration into MCLs, whereas RNase A and IgG showed insignificant penetration. At 10-fold higher dose, a significant increase in penetration was observed for IgG only, while cetuximab showed an intense accumulation limited to the front layers. PEGylated TRAIL and RNase A formulated in a heparin-Pluronic (HP) nanogel showed significantly improved penetration attributable to increased stability and extracellular matrix binding, respectively. IgG penetration was significantly enhanced with paclitaxel pretreatment as a penetration enhancer. The present study suggests that MCL culture may be useful in evaluation of protein delivery in the tumor interstitium. Four model proteins showed limited interstitial penetration in MCL cultures. Bioaffinity, rather than molecular size, seems to have a positive effect on tissue penetration, although high binding affinity may lead to sequestration in the front cell layers. Polymer conjugation and nanoformulation, such as PEGylation and HP nanogel, or use of penetration enhancers are potential strategies to increase interstitial delivery of anticancer protein drugs.

The distribution and retention of paclitaxel and doxorubicin in multicellular layer cultures

Limited distribution of anticancer drugs has been recognized as a significant hurdle to efficacy. We investigated a detailed penetration/distribution profile of paclitaxel-rhodamine (PTX-rd) and doxorubicin (DOX) in multicellular layer (MCL) cultures of human cancer cells as an in vitro model for avascular regions of solid tumors. MCLs were exposed to drugs and fluorescent images of frozen sections were acquired for determination of drug penetration into MCL under various exposure conditions. PTX-rd and DOX showed drastically different profiles of penetration. DOX showed full penetration after 1 h and accumulation over 3 h, whereas PTX-rd showed slow and limited penetration, with accumulation only within the top 20% of layers by 2 h and insignificant penetration even at 72 h. Drug retention in MCL was more dependent on drug concentration, rather than exposure time, i.e., drug distribution increased by 6.3- and 2.5-fold for PTX-rd and DOX, respectively, when exposed to higher concentrations under comparable AUC exposure (1 μM × 24 h vs. 50 μM × 0.5 h). Anti-proliferative activity of PTX and DOX in MCL, as determined by cell cycle analysis, was minimal and may be attributed, at least in part, to their limited distribution in multicellular cultures. Overall, we demonstrated that penetration and retention of PTX and DOX in MCL was not only concentration- and time-dependent, but also schedule-dependent. It is suggested that slow releasing formulations or a slow infusion regimen may not necessarily be desirable, especially for PTX, due to insufficient penetration and accumulation which may result from a low local concentration at the target site.

The reciprocal interaction: chemotherapy and tumor microenvironment

Despite significant improvements in ways to treat cancer, numerous patients still die from this disease. One of the reasons for this inability to cure cancer is the lack of ability of drugs to penetrate target cells properly. While studies on drug resistance have focused on the molecular mechanisms of single cells, there has been little attention on drug penetration or distribution in solid tumor tissues. It is reported that the factors that obstruct the penetration and distribution of drugs in solid tumors are closely related to the microenvironment of solid tumors. This review paper aims to discuss the microenvironment that hinders drug penetration in solid tumors and to investigate whether or not changes in the microenvironment can improve drug penetration. This review also introduces in vitro 3D multicellular culture systems that can reproduce the characteristics of solid tumors in vivo and that are required for such studies.

Neurotrophic activity of DA-9801, a mixture extract of Dioscorea japonica Thunb. and Dioscorea nipponica Makino, in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Dioscorea japonica Thunb. has been traditionally used to treat polyuria and diabetes in Korea.

AIM OF THE STUDY

We previously report the effects of Dioscorea japonica Thunb. extract on glucose control, NGF induction, and neuroprotection in a rodent diabetic model. Since the most potent fraction, DA-9801, was identified from a mixture of Dioscorea japonica Thunb. (DJ) and Dioscorea nipponica Makino (DN) following bioactivity-guided fractionation, here, we investigated the potential mechanism of the extract activity against diabetic peripheral neuropathy (DPN).

MATERIALS AND METHODS

A 1:3 mixture of DJ and DN was extracted with ethanol (DA-9801) and further fractionated into an ethylacetate-soluble fraction (DA-9801E). Effects of these extracts on neurite outgrowth were measured in PC-12 cells and DRG neurons. Effects on cell viability and TrkA phosphorylation were evaluated in PC-12 cells. NGF induction effect was determined in primary Schwann cells as well as IMS32 cells (immortalized Schwann cells).

RESULTS

No cytotoxicity was observed in PC-12 cells at the concentration below 500 μg/ml of either DA-9801 or DA-9801E. DA-9801 and DA-9801E at 100 μg/ml and 10 μg/ml, respectively, showed a significant effect on neurite outgrowth in PC-12 cells and DRG neurons in the presence of or absence a low concentration of NGF (2 ng/ml). The Trk-A phosphorylation effect of DA9801 was confirmed in PC-12 cells. An NGF induction effect of these extracts was not detected in either IMS-32 cells, or primary Schwann cells.

CONCLUSIONS

The NGF agonistic activity of DA-9801 and DA-9801E was demonstrated, which may contribute to their neuroprotective effect against DPN. Studies of the detailed mechanism of these extracts as well as identification of the active components are warranted for the development of an anti-DPN drug from DJ and DN.

Penetration of paclitaxel and 5-fluorouracil in multicellular layers of human colorectal cancer cells

Limited efficacy of chemotherapeutic drugs against solid tumors has been attributed to poor drug penetration into tumor tissues. Multicellular layer (MCL) cultures recapitulate barriers to drug penetration and distribution and have been used successfully in the production of clinically relevant data. In the present study, we evaluated the characteristics of paclitaxel (PTX) and 5-fluorouracil (5-FU) penetration and their effects on tissue penetration using MCLs of human colorectal cancer cells (DLD-1 and HT-29) grown in Transwell inserts. Drug concentration in conditioned media after MCL penetration was estimated using % survival of cells exposed to the conditioned media, and the penetration rate was calculated as % drug concentration relative to the expected concentration after penetration of cell-free MCLs. PTX showed limited penetration in both MCLs in contrast to the full penetration seen by 5-FU. The penetration rate measured after 24 h by cytotoxicity of the conditioned media was 40 and 38% in DLD-1 (20 μM) and HT-29 MCLs (1 μM), respectively, at which concentration the conditioned media produced 50% growth inhibition in monolayers. The penetration profile obtained using [14C]-paclitaxel also showed slow and limited penetration with concentration- and cell line-dependency. In HT-29 MCL, full penetration of PTX was obtained at 10 μM after 48 h, whereas only 80% was obtained at 1 μM. In DLD-1 MCLs, penetration of PTX was minimal, especially at 1 μM, showing penetration rates as low as 10 and 20% after 24 and 96 h, respectively. When PTX and 5-FU were allowed to penetrate in sequential combination, no effect on the penetration rate was observed. Overall, our results demonstrated limited penetration of PTX in human colorectal cancer MCLs along with concentration-, time-, and cell line-dependency. Assessment of penetration using cytotoxicity of the conditioned media used in the present study may be useful in early stage screening of anticancer agents for their potential in tissue penetration.

Abstract 3591: Efficacy and distribution of intratumoral paclitaxel given alone or in combination with doxorubicin using hydrogel in nude mice

Intralesional chemotherapy is suggested to improve local tumor control as well as systemic toxicity profile of antitumor agents against solid tumors. Thermosensitive poly-(organophosphazene) hydrogel is a novel injectable polymer that transforms from sol to gel at body temperature. In this study, we evaluated distribution and efficacy of paclitaxel (PTX) when given as intratumoral injection using the hydrogel or solution formulation in human SNU-601 tumor xenograft-bearing nude mice. Following intratumoral injection of 60 mg/kg of PTX, plasma drug concentrations were lower than 0.5 μg/ml(LOQ) for both hydrogel and solution. For PTX tumor concentration, Cmax was 1.2 folds higher and T1/2 3.7 folds longer with hydrogel compared to solution. Over 21d, AUCtumor was 1.5 folds greater in hydrogel compared to solution, indicating greater drug exposure and retention at target site. The antitumor activity of PTX (30 mg/kg) when given alone or in combination with doxorubicin (DOX, 15 mg/kg) was evaluated after intratumoral hydrogel injection in SNU-601 (Td= 21 d) and SNU-398 (Td= 5 d) xenograft models. The synergism between DOX and PTX, independent of dosage form, was observed in SNU-398, but not in SNU-601. No toxicity was observed in hydrogel group in neither single nor combination treatment. For slow-growing SNU-601 tumor, combination of PTX and DOX given in hyrogel mixture showed greater activity than that of solution. In conclusion, poly-(organophosphazene) polymer may be useful in intralesional administration of PTX to achieve greater drug exposure at target site. Also, combination of DOX and PTX, showed a potential for greater antitumor efficacy, which warrants further evaluation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3591.

Synergistic interaction between tetra-arsenic oxide and paclitaxel in human cancer cells in vitro

Similar to arsenic trioxide (As2O3), tetra-arsenic oxide (As4O6, TAO) has shown anti-proliferative and apoptosis-inducing effects against human leukemic and solid tumor cells. In order to assess the increase in efficacy, we evaluated the combinatory interaction of TAO combined with paclitaxel, 5-FU or cisplatin and studied its mechanism of action in the cell lines of human gastric, cervix and head and neck tumors. Two agents were combined at equitoxic ratios based on the IC50 of each drug. Efficacy improvement was evaluated using a combination index and isobologram at 50% inhibition level. Apoptosis induction and expression of apoptosis-related proteins was determined and the effect on microtubule polymerization was monitored. TAO combined with paclitaxel showed synergistic interaction in all three of gastric, cervix and head and neck cancer cell lines. On the other hand, TAO when combined with 5-FU or cisplatin showed an antagonistic interaction in head and neck or cervix cancer cell lines, respectively. Simultaneous treatment with TAO with paclitaxel resulted in an increased percentage of apoptotic cells and a significant increase in PARP cleavage and caspase-3 activation in the gastric and cervix cancer cells compared to TAO alone as well as the antagonistic groups (TAO with 5-FU or cisplatin). TAO suppressed the tubulin polymerization in the presence and absence of paclitaxel in a concentration-dependent manner, suggesting mitotic catastrophe as a potential mechanism of the synergism with paclitaxel. Overall, the present study suggests that TAO may have a greater potential as an anti-cancer agent against human gastric, cervix and head and neck tumors, in combination with paclitaxel. The synergistic interaction with paclitaxel may be associated with increased apoptosis via inhibition of paclitaxel-induced tubulin polymerization. Further detailed studies of combinatory mechanisms and evaluation using in vivo models are warranted.

A simple HPLC method for doxorubicin in plasma and tissues of nude mice

Doxorubicin is a cytotoxic anthracycline that has been used for the treatment of several malignancies. Several HPLC methods have been reported for the quantification of doxorubicin in biological samples. Tissue matrix effect and sample size requirements, however, have been remaining issues for simple and easy-to-adapt analytical methods in small animal experiments. The present study established a simple HPLC method for doxorubicin in plasma and tissues (tumor, heart, spleen, liver, gastrointestinal tract, brain, lung, and kidney) of nude mice. Our method required a small sample volume (100 microL plasma and 10 mg tissue), which made it possible to use each blank tissue for calibration curves. The limit of quantification was 25 ng/mL in plasma and 0.1 to 0.4 microg/mg in other tissues with recovery rates ranging from 52.4 to 95.2%. The linearity, accuracy and precision in all tissues, except gastrointestinal tract (GIT), were found to be acceptable in the range of 25-2000 ng/mL plasma and 0.1-4 ng/mg tissue. This method was used successfully to determine the drug concentration in plasma and tissues of human tumor xenograft-bearing nude mice given intratumoral doxorubicin in a polymeric drug delivery system designed for sustained release. In conclusion, the present method may be useful as a simple and easy-to-adapt, yet, sensitive analytical method of doxorubicin for plasma and tissue pharmacokinetic studies in small animals such as nude mice.

Novel application of multicellular layers culture for in situ evaluation of cytotoxicity and penetration of paclitaxel

Limited drug penetration into tumor tissue is one of the major factors causing clinical drug resistance in human solid tumors. The multicellular layers (MCL) of human cancer cells have been successfully used to study tissue pharmacokinetics of anticancer drugs. The purpose of this study was to develop a direct and simple method to evaluate vitality changes in situ within MCL using calcein-AM. Human colorectal (DLD-1, HT-29) and bladder (HT-1376, J-82) cancer cells were grown in Transwell inserts to form MCL and subjected to paclitaxel exposure. The drug distribution was evaluated using paclitaxel-rhodamine. Photonic attenuation and limited penetration of calcein-AM prevented cellular vitality evaluation on optical sections under confocal microscopy in DLD-1 MCL. However, direct measurement of the fluorescence intensity on frozen sections of MCL allowed successful vitality assessment in more than 80% depth for HT-29 and J-82 MCL and in the upper 40% depth for DLD-1 and HT-1376 MCL. The penetration of paclitaxel-rhodamine was greater in HT-29 than DLD-1 and its distribution pattern was correlated to the spatial profile of vitality deterioration in both MCL, suggesting that tissue penetration may be an important determinant of drug effect in tumors. In conclusion, a novel method for vitality evaluation in situ within MCL was developed using calcein-AM. This method may provide clinically relevant data regarding the spatial pharmacodynamics of anticancer agents within avascular regions of solid tumors.

Anti-tumor activity of heptaplatin in combination with 5-fluorouracil or paclitaxel against human head and neck cancer cells in vitro

Heptaplatin (HTP), a newly developed platinum analog, has been approved for the treatment of gastric cancers in South Korea. In this study we explored the potential of HTP for the treatment of head and neck squamous cell cancers (HNSCC). The anti-proliferative activity of HTP was evaluated in FaDu, a human HNSCC cell line. Combinations of HTP with 5-fluorouracil (5-FU) or paclitaxel (PTX) were determined using combination indexes, and were compared with combinations of cisplatin and 5-FU or PTX. In order to evaluate the transport of HTP into tumor tissue, its penetration through multicell layers (MCLs) of cancer cells was measured. Cisplatin+5-FU and HTP+5-FU showed additive to antagonistic interactions. In terms of the HTP+paclitaxel combination, HTP showed antagonism and additivity at the 50 and 80% growth inhibition levels, respectively. An additive interaction was obtained and apoptosis was increased by 2-fold at both inhibition levels when the combinatorial PTX dose was reduced to 1/10. HTP, but not cisplatin or oxaliplatin (L-OHP), maintained its anti-proliferative activity after MCL penetration at clinically relevant concentrations, which can be attributed to lower protein binding of HTP. In conclusion, the present study suggests that low-dose PTX may sensitize tumor cells to HTP. HTP also showed greater penetration through multilayers of tumor cells compared to cisplatin and L-OHP, which may be an important characteristic for solid tumor treatment. Overall, the present study supports the clinical development of HTP in combination with low-dose PTX against HNSCC.

Clinical pharmacokinetics of oxaliplatin and 5-fluorouracil administered in combination with leucovorin in Korean patients with advanced colorectal cancer

PURPOSE

Oxaliplatin and 5-fluorouracil (5-FU) act synergistically in colorectal cancer. Here, we evaluated the pharmacokinetics of oxaliplatin and 5-FU administered in combination with leucovorin in Korean advanced colorectal cancer patients.

METHODS

Nine patients with advanced colorectal cancer were included in this study. The 3-week regimen consisted of oxaliplatin (2-h infusion, 130 mg/m(2)on day 1) followed by 5-FU and leucovorin (2-h infusion, 425 and 20 mg/m(2), respectively, from day 1 to day 5). Blood samples were taken and platinum concentrations in total plasma, plasma ultrafiltrate, and RBCs were determined. Plasma concentrations of 5-FU were also determined.

RESULTS

The C (max) of oxaliplatin was observed at the end of infusion, with mean values of 4.66, 0.84, and 2.69 microg/ml for total plasma, plasma ultrafiltrate, and RBC samples, respectively. C (max) ratios of total/free were significantly higher than those reported in other ethnic groups. An accumulation of platinum was observed in RBCs, but not in total plasma and plasma ultrafiltrate samples. A significant correlation was found between the total body clearance of ultrafiltrable platinum and creatinine clearance. The C (max) of plasma 5-FU ranged from 23.9 to 533.8 ng/ml, indicating large inter-patient pharmacokinetic variations.

CONCLUSIONS

This study shows that pharmacokinetics of oxaliplatin in Korean patients is comparable with that of other ethic groups, except for the higher C (max) ratios of total/free. The C (max) of 5-FU in plasma showed large variations among patients. Antitumor efficacy in Korean advanced colorectal cancer patients given oxaliplatin and 5-FU should be further evaluated with respect to pharmacokinetic variabilities.