Limits...
Mechanisms and implications of dual-acting methotrexate in folate-targeted nanotherapeutic delivery.

Wong PT, Choi SK - Int J Mol Sci (2015)

Bottom Line: A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell.However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle.Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan Medical School, Ann Arbor, MI 48109, USA. ptw@med.umich.edu.

ABSTRACT
The rational design of a nanoplatform in drug delivery plays a crucial role in determining its targeting specificity and efficacy in vivo. A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell. However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle. In this review, we evaluate the validity of this new strategy by using methotrexate, which displays multifunctional mechanisms of action. Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division. Thus we describe a series of fifth generation poly(amido amine) dendrimers conjugated with methotrexate, and discuss several lines of evidence supporting the efficacy of this new platform strategy based on surface plasmon resonance spectroscopy, enzyme activity assays, and cell-based studies with folate receptor (+) KB cancer cells.

Show MeSH

Related in: MedlinePlus

Two strategies for targeted drug delivery to a folate receptor (FAR)-overexpressing tumor cell with a fifth generation (G5) dendrimer NP. (A) A conventional two-molecule approach with G5(FA)n(MTX)m presenting folic acid (FA) as a targeting ligand and carrying methotrexate (MTX) as a drug payload and (B) A dual-acting, single molecule approach with G5(MTX)n presenting MTX as both a targeting ligand and drug payload.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4307333&req=5

ijms-16-01772-f001: Two strategies for targeted drug delivery to a folate receptor (FAR)-overexpressing tumor cell with a fifth generation (G5) dendrimer NP. (A) A conventional two-molecule approach with G5(FA)n(MTX)m presenting folic acid (FA) as a targeting ligand and carrying methotrexate (MTX) as a drug payload and (B) A dual-acting, single molecule approach with G5(MTX)n presenting MTX as both a targeting ligand and drug payload.

Mentions: In this article, we describe the mechanisms and implications of MTX as a dual-acting molecule that can both target a tumor biomarker and function as a therapeutic agent (Figure 1). MTX belongs to the class of antifolate therapeutic agents that have been used for treating cancers and rheumatoid arthritis [31,53]. Its therapeutic effect is attributed primarily to inhibition of human dihydrofolate reductase (DHFR), an enzyme localized in the cytoplasm. In addition, MTX binds to FAR because of its high structural similarity to FA. To test this MTX-based dual-acting strategy, we designed a series of multivalent dendrimer NPs, each composed of multiple MTX ligands conjugated to a fifth generation (G5) PAMAM dendrimer scaffold, and investigated their dual mechanisms of action pertinent to tumor targeted drug delivery. Firstly, we employed surface plasmon resonance (SPR) spectroscopy and determined their binding avidity to folate binding protein (FBP) immobilized to a sensor chip as a model surface for FAR(+) tumor cells. The SPR studies provide evidence supportive of multivalent tight binding of MTX-conjugated NPs. Secondly, we studied these NPs for their ability to inhibit DHFR by using a cell free-enzyme assay which shows dose-dependent blocking of the enzyme activity by the MTX molecules attached to the dendrimer. Thirdly, we determined the ability of these MTX-conjugated dendrimers to bind and kill FAR(+) KB tumor cells in vitro. In summary, we describe the design principle of dual-acting MTX conjugates and provide strong evidence supporting the ability of these conjugates to display the dual activities needed for an effective cancer-targeting delivery and therapeutic platform.


Mechanisms and implications of dual-acting methotrexate in folate-targeted nanotherapeutic delivery.

Wong PT, Choi SK - Int J Mol Sci (2015)

Two strategies for targeted drug delivery to a folate receptor (FAR)-overexpressing tumor cell with a fifth generation (G5) dendrimer NP. (A) A conventional two-molecule approach with G5(FA)n(MTX)m presenting folic acid (FA) as a targeting ligand and carrying methotrexate (MTX) as a drug payload and (B) A dual-acting, single molecule approach with G5(MTX)n presenting MTX as both a targeting ligand and drug payload.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4307333&req=5

ijms-16-01772-f001: Two strategies for targeted drug delivery to a folate receptor (FAR)-overexpressing tumor cell with a fifth generation (G5) dendrimer NP. (A) A conventional two-molecule approach with G5(FA)n(MTX)m presenting folic acid (FA) as a targeting ligand and carrying methotrexate (MTX) as a drug payload and (B) A dual-acting, single molecule approach with G5(MTX)n presenting MTX as both a targeting ligand and drug payload.
Mentions: In this article, we describe the mechanisms and implications of MTX as a dual-acting molecule that can both target a tumor biomarker and function as a therapeutic agent (Figure 1). MTX belongs to the class of antifolate therapeutic agents that have been used for treating cancers and rheumatoid arthritis [31,53]. Its therapeutic effect is attributed primarily to inhibition of human dihydrofolate reductase (DHFR), an enzyme localized in the cytoplasm. In addition, MTX binds to FAR because of its high structural similarity to FA. To test this MTX-based dual-acting strategy, we designed a series of multivalent dendrimer NPs, each composed of multiple MTX ligands conjugated to a fifth generation (G5) PAMAM dendrimer scaffold, and investigated their dual mechanisms of action pertinent to tumor targeted drug delivery. Firstly, we employed surface plasmon resonance (SPR) spectroscopy and determined their binding avidity to folate binding protein (FBP) immobilized to a sensor chip as a model surface for FAR(+) tumor cells. The SPR studies provide evidence supportive of multivalent tight binding of MTX-conjugated NPs. Secondly, we studied these NPs for their ability to inhibit DHFR by using a cell free-enzyme assay which shows dose-dependent blocking of the enzyme activity by the MTX molecules attached to the dendrimer. Thirdly, we determined the ability of these MTX-conjugated dendrimers to bind and kill FAR(+) KB tumor cells in vitro. In summary, we describe the design principle of dual-acting MTX conjugates and provide strong evidence supporting the ability of these conjugates to display the dual activities needed for an effective cancer-targeting delivery and therapeutic platform.

Bottom Line: A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell.However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle.Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan Medical School, Ann Arbor, MI 48109, USA. ptw@med.umich.edu.

ABSTRACT
The rational design of a nanoplatform in drug delivery plays a crucial role in determining its targeting specificity and efficacy in vivo. A conventional approach relies on the surface conjugation of a nanometer-sized particle with two functionally distinct types of molecules, one as a targeting ligand, and the other as a therapeutic agent to be delivered to the diseased cell. However, an alternative simplified approach can be used, in which a single type of molecule displaying dual function as both a targeting ligand and therapeutic agent is conjugated to the nanoparticle. In this review, we evaluate the validity of this new strategy by using methotrexate, which displays multifunctional mechanisms of action. Methotrexate binds to the folate receptor, a surface biomarker frequently overexpressed in tumor cells, and also inhibits dihydrofolate reductase, an enzyme critical for cell survival and division. Thus we describe a series of fifth generation poly(amido amine) dendrimers conjugated with methotrexate, and discuss several lines of evidence supporting the efficacy of this new platform strategy based on surface plasmon resonance spectroscopy, enzyme activity assays, and cell-based studies with folate receptor (+) KB cancer cells.

Show MeSH
Related in: MedlinePlus