Analysis of Targeted Viral Protein Nanoparticles Delivered to HER2+ Tumors

Summary

This article details the procedures for optical imaging analysis of the tumor-targeted nanoparticle, HerDox. In particular, detailed use of the multimode imaging device for detecting tumor targeting and assessing tumor penetration is described here.

Abstract

The HER2+ tumor-targeted nanoparticle, HerDox, exhibits tumor-preferential accumulation and tumor-growth ablation in an animal model of HER2+ cancer. HerDox is formed by non-covalent self-assembly of a tumor targeted cell penetration protein with the chemotherapy agent, doxorubicin, via a small nucleic acid linker. A combination of electrophilic, intercalation, and oligomerization interactions facilitate self-assembly into round 10-20 nm particles. HerDox exhibits stability in blood as well as in extended storage at different temperatures. Systemic delivery of HerDox in tumor-bearing mice results in tumor-cell death with no detectable adverse effects to non-tumor tissue, including the heart and liver (which undergo marked damage by untargeted doxorubicin). HER2 elevation facilitates targeting to cells expressing the human epidermal growth factor receptor, hence tumors displaying elevated HER2 levels exhibit greater accumulation of HerDox compared to cells expressing lower levels, both in vitro and in vivo. Fluorescence intensity imaging combined with in situ confocal and spectral analysis has allowed us to verify in vivo tumor targeting and tumor cell penetration of HerDox after systemic delivery. Here we detail our methods for assessing tumor targeting via multimode imaging after systemic delivery.

Introduction

Tumor-targeting of chemotherapy has the potential to eliminate cancer cells at lower dose compared to untargeted drugs because more of the delivered therapy can accumulate at its intended destination rather than distribute to non-tumor tissue. As the latter situation would dilute out the efficacy of the drug and thus require higher doses to be effective, tumor-targeting has both therapeutic and safety advantages over standard non-targeted treatment.

Targeting chemotherapy by encapsulation in self-assembled nanoparticles allows the drug to remain chemically unmodified in contrast to drugs that are covalently linked to targeting molecules. A....

Protocol

1. Systemic Delivery In vivo

1. Mix enough HerDox with sterile saline to equate 0.2 ml of a 0.004 mg/kg dose of HerDox per injection for a 6-8 week old NU/NU mouse bearing subcutaneous bilateral flank xenograft tumors.
2. Gently draw the HerDox mixture into a 3/10 cc insulin syringe fitted with a 29G needle, avoiding bubbles.
3. Anesthesia is induced by brief isoflurane exposure in an induction chamber equipped with a gas scavenging system (Oxygen flow rates: 0.5-1 L/min, isoflurane concen.......

Discussion

Dox fluorescence can be detectable in vivo using the multimode imager when tumors are subcutaneous. However, the therapeutically effective dose of HerDox (0.004 mg/kg) is below the detection threshold after a single dose. In contrast, after 7 daily injections (1x/day for 7 days), the tumor accumulation and retention of the particle is sufficient to enable visualization of Dox fluorescence.

It is critical when working with Dox or any other fluorophore for in vivo imaging that.......

Materials

Name	Company	Catalog Number	Comments
Name of the reagent	Company	Catalogue number	Comments (optional)
Fluorescence laser scanning confocal microscope	Leica	SPE
In Vivo Optical Imager	Spectral Molecular Imaging	Multimode In Vivo Optical Imager
Doxorubicin-HCl	Sigma-Aldrich	D4035
Nude (NU/NU) mouse, female, 6-8 week	Charles River	Strain code 088
MDA-MB-435 human HER2+ tumor cells	NCI-Frederick Cancer DCTD Tumor/Cell Line Repository	0507292
3/10 cc insulin syringe U-100 with 29G x 1/2" Ultra-FineIV permanently attached needle	BD	309301
Delta T chamber	Bioptechs	04200417B