Paclitaxel-2'-Ethylcarbonate prodrug can circumvent P-glycoprotein-mediated cellular efflux to increase drug cytotoxicity.

Abstract

PURPOSE:

The aim of the study was to investigate whether 2'-ethylcarbonate-linked paclitaxel (TAX-2'-Et) circumvents P-glycoprotein (P-gp)-mediated cellular efflux and cytotoxicity enhanced by TAX-2'-Et activation within human culture cells transfected with a rabbit liver carboxylesterase (Ra-CES) cDNA.

MATERIALS AND METHODS:

TAX-2'-Et transport was characterized in a human colon carcinoma cell line (Caco-2) and paclitaxel (TAX)-resistant ovarian carcinoma cells (SKOV3/TAX60). Expression of P-gp, multidrug resistance protein (MRP) 2 and Ra-CES was detected by Western blotting. Cytotoxicity against Ra-CES-expressing cells and cellular amount of TAX produced were determined by MTT assay and using HPLC, respectively.

RESULTS:

Unlike rhodamine123 and TAX, TAX-2'-Et did not exhibit polarized transport in the Caco-2 cells in the absence or presence of verapamil. P-gp levels were expressed much higher in the SKOV3/ TAX60 cells than in the Caco-2 cells. MRP2 protein was not detectable in the SKOV3/TAX60 cells. Uptake by the SKOV3/TAX60 cells was similar in quantity to the amount internalized by P-gp-negative SKOV3 cells. In the SKOV3/TAX60 cells, cellular uptake of TAX-2'-Et was not altered regardless of the absence or presence of verapamil. The cytotoxicity to the untransfected SKOV3 cells induced by TAX-2'-Et was significantly lower than that induced by TAX. In the Ra-CES-expressing SKOV3 line, the EC50 value of TAX (10.6 nM) was approximately four-fold higher than that of TAX-2'-Et (2.5 nM). Transfection of Ra-CES into another TAX-resistant ovarian carcinoma cells (KOC-7c) conferred a high level of TAX-2'-Et cytotoxicity via prodrug activation. The intracellular levels of TAX produced from TAX-2'-Et in the Ra-CES-positive KOC-7c cells significantly increased compared with the levels seen in exposure of the untransfected KOC-7c cells to TAX.

CONCLUSIONS:

TAX-2'-Et can circumvent P-gp-associated cellular efflux of TAX. TAX-2'-Et is converted into TAX by the Ra-CES, supporting its potential use as a theoretical GDEPT strategy for cancer cells expressing high levels of P-gp. The TAX-2'-Et prodrug efficiently increased the amount of intracellular TAX, which mediates tumor cell death.

• Authors: Tadatoshi Tanino, Akihiro Nawa, Eisaku Kondo, Fumitaka Kikkawa, Tohru Daikoku, Tatsuya Tsurumi, Chenhong Luo, Yukihiro Nishiyama, Yuki Takayanagi, Katuhiko Nishimori, Seiji Ichida, Tetsuyuki Wada, Yasuyoshi Miki, Masahiro Iwaki
• Journal: Pharmaceutical research (Pharm Res) Vol. 24 Issue 3 Pg. 555-65 (Mar 2007) ISSN: 0724-8741 [Print] United States
• PMID: 17245652 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ABCC2 protein, human
• ATP Binding Cassette Transporter, Subfamily B, Member 1
• Antineoplastic Agents, Phytogenic
• Membrane Transport Proteins
• Multidrug Resistance-Associated Protein 2
• Multidrug Resistance-Associated Proteins
• Prodrugs
• Carboxylesterase
• Paclitaxel

Topics

• ATP Binding Cassette Transporter, Subfamily B, Member 1 (genetics, metabolism)
• Animals
• Antineoplastic Agents, Phytogenic (chemistry, pharmacokinetics, pharmacology)
• Biological Transport
• Blotting, Western
• Caco-2 Cells
• Carboxylesterase (genetics, metabolism)
• Cell Line, Tumor
• Cell Proliferation (drug effects)
• Cell Survival (drug effects, genetics)
• Dose-Response Relationship, Drug
• Drug Resistance, Neoplasm
• Female
• Humans
• Membrane Transport Proteins (genetics, metabolism)
• Molecular Structure
• Multidrug Resistance-Associated Protein 2
• Multidrug Resistance-Associated Proteins (genetics, metabolism)
• Paclitaxel (chemistry, pharmacokinetics, pharmacology)
• Plasmids (genetics)
• Prodrugs (chemistry, pharmacokinetics, pharmacology)
• Rabbits
• Transfection