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Superior Performance of Aptamer in Tumor Penetration over Antibody: Implication of Aptamer-Based Theranostics in Solid Tumors.

Xiang D, Zheng C, Zhou SF, Qiao S, Tran PH, Pu C, Li Y, Kong L, Kouzani AZ, Lin J, Liu K, Li L, Shigdar S, Duan W - Theranostics (2015)

Bottom Line: Targeted drug delivery to solid tumors followed by complete drug penetration and durable retention will significantly improve clinical outcomes of cancer therapy.To explore whether aptamers are superior to antibodies in terms of tumor penetration, we carried out the first comprehensive study to compare the performance of an EpCAM aptamer with an EpCAM antibody in theranostic applications.We found that the EpCAM aptamer can not only effectively penetrate into the tumorsphere cores but can also be retained by tumor sphere cells for at least 24 h, while limited tumor penetration by EpCAM antibody was observed after 4 h incubation.

View Article: PubMed Central - PubMed

Affiliation: 1. School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria 3216, Australia.

ABSTRACT
Insufficient penetration of therapeutic agents into tumor tissues results in inadequate drug distribution and lower intracellular concentration of drugs, leading to the increase of drug resistance and resultant failure of cancer treatment. Targeted drug delivery to solid tumors followed by complete drug penetration and durable retention will significantly improve clinical outcomes of cancer therapy. Monoclonal antibodies have been commonly used in clinic for cancer treatment, but their limitation of penetrating into tumor tissues still remains because of their large size. Aptamers, as "chemical antibodies", are 15-20 times smaller than antibodies. To explore whether aptamers are superior to antibodies in terms of tumor penetration, we carried out the first comprehensive study to compare the performance of an EpCAM aptamer with an EpCAM antibody in theranostic applications. Penetration and retention were studied in in vitro three-dimensional tumorspheres, in vivo live animal imaging and mouse colorectal cancer xenograft model. We found that the EpCAM aptamer can not only effectively penetrate into the tumorsphere cores but can also be retained by tumor sphere cells for at least 24 h, while limited tumor penetration by EpCAM antibody was observed after 4 h incubation. As observed from in vivo live animal imaging, EpCAM aptamers displayed a maximum tumor uptake at around 10 min followed by a rapid clearance after 80 min, while the signal of peak uptake and disappearance of antibody appeared at 3 h and 6 h after intravenous injection, respectively. The signal of PEGylated EpCAM aptamers in xenograft tumors was sustained for 26 h, which was 4.3-fold longer than that of the EpCAM antibody. Consistently, there were 1.67-fold and 6.6-fold higher accumulation of PEGylated aptamer in xenograft tumors than that of antibody, at 3 h and 24 h after intravenous administration, respectively. In addition, the aptamer achieved at least a 4-time better tumor penetration in xenograft tumors than that of the antibody at a 200 μm distances from the blood vessels 3 h after intravenous injection. Taken together, these data indicate that aptmers are superior to antibodies in cancer theranostics due to their better tumor penetration, more homogeneous distribution and longer retention in tumor sites. Thus, aptamers are promising agents for targeted tumor therapeutics and molecular imaging.

No MeSH data available.


Related in: MedlinePlus

Superior performance of EpCAM aptamer to the antibody in in vivo molecular imaging. (a) Representative live animal images of aptamers and antibody. NOD-SCID mice bearing HT29 tumor (150 mm3) received a single i.v. injection of 0.75 nmol of EpCAM aptamer and EpCAM antibody. Log-scale heat map (at the right) of photon flux applies to all panels. p/s/cm2/sr: photons per second per cm2 per steradian. Arrow depicts the position of the subcutaneous HT29 tumor. (b) The fluorescence-time curve of EpCAM aptamer and EpCAM antibody in tumors as indicated in (a) was determined by Living Imaging Software v2.50 (Xenogen) with the units of photons/s/cm2/sr. Data are means ± SEM, n=3.
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Figure 3: Superior performance of EpCAM aptamer to the antibody in in vivo molecular imaging. (a) Representative live animal images of aptamers and antibody. NOD-SCID mice bearing HT29 tumor (150 mm3) received a single i.v. injection of 0.75 nmol of EpCAM aptamer and EpCAM antibody. Log-scale heat map (at the right) of photon flux applies to all panels. p/s/cm2/sr: photons per second per cm2 per steradian. Arrow depicts the position of the subcutaneous HT29 tumor. (b) The fluorescence-time curve of EpCAM aptamer and EpCAM antibody in tumors as indicated in (a) was determined by Living Imaging Software v2.50 (Xenogen) with the units of photons/s/cm2/sr. Data are means ± SEM, n=3.

Mentions: Given that the EpCAM RNA aptamer penetrated the tumorsphere much better than antibody in vitro, we next compared the performance in in vivo imaging between aptamer and antibody. A DY647 fluorophore was conjugated to the 5'-end of the EpCAM aptamer to facilitate molecular imaging. As for the imaging study, NOD/SCID mice-bearing HT29 xenograft tumors with a tumor volume of ~150 mm3 received a bolus i.v. injection of 0.75 nmole of DY647-labelled aptamers or FITC-labeled EpCAM antibodies. The whole body imaging was performed using the IVIS Live Imaging System. Fluorescence signals obtained from aptamers or antibodies at the regions of interest (ROIs) of tumor sites were recorded at a 5 min interval until the signal disappeared. The signal of aptamer on HT29 tumors appeared immediately and the maximum uptake was observed at around 10 min after i.v. injection and lasted for approximately 80 min (Fig. 3a and b). In sharp contrast, the signal for antibody observed in tumor sites had a slow onset, with the maximum uptake reached at 3 h. The signal in the tumor receiving EpCAM antibody lasted for at least 6 h. Thus, the aptamer achieved highest concentration in the tumor within 10 min and the signal in the tumor diminished at least 4.5-times faster than that of the antibody. Such quick onset of the maximum signal at the site of the tumor followed by rapid disappearance confers aptamer with highly desirable characteristics for function as a promising molecular imaging probe which outperform antibodies 44, 45.


Superior Performance of Aptamer in Tumor Penetration over Antibody: Implication of Aptamer-Based Theranostics in Solid Tumors.

Xiang D, Zheng C, Zhou SF, Qiao S, Tran PH, Pu C, Li Y, Kong L, Kouzani AZ, Lin J, Liu K, Li L, Shigdar S, Duan W - Theranostics (2015)

Superior performance of EpCAM aptamer to the antibody in in vivo molecular imaging. (a) Representative live animal images of aptamers and antibody. NOD-SCID mice bearing HT29 tumor (150 mm3) received a single i.v. injection of 0.75 nmol of EpCAM aptamer and EpCAM antibody. Log-scale heat map (at the right) of photon flux applies to all panels. p/s/cm2/sr: photons per second per cm2 per steradian. Arrow depicts the position of the subcutaneous HT29 tumor. (b) The fluorescence-time curve of EpCAM aptamer and EpCAM antibody in tumors as indicated in (a) was determined by Living Imaging Software v2.50 (Xenogen) with the units of photons/s/cm2/sr. Data are means ± SEM, n=3.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4508498&req=5

Figure 3: Superior performance of EpCAM aptamer to the antibody in in vivo molecular imaging. (a) Representative live animal images of aptamers and antibody. NOD-SCID mice bearing HT29 tumor (150 mm3) received a single i.v. injection of 0.75 nmol of EpCAM aptamer and EpCAM antibody. Log-scale heat map (at the right) of photon flux applies to all panels. p/s/cm2/sr: photons per second per cm2 per steradian. Arrow depicts the position of the subcutaneous HT29 tumor. (b) The fluorescence-time curve of EpCAM aptamer and EpCAM antibody in tumors as indicated in (a) was determined by Living Imaging Software v2.50 (Xenogen) with the units of photons/s/cm2/sr. Data are means ± SEM, n=3.
Mentions: Given that the EpCAM RNA aptamer penetrated the tumorsphere much better than antibody in vitro, we next compared the performance in in vivo imaging between aptamer and antibody. A DY647 fluorophore was conjugated to the 5'-end of the EpCAM aptamer to facilitate molecular imaging. As for the imaging study, NOD/SCID mice-bearing HT29 xenograft tumors with a tumor volume of ~150 mm3 received a bolus i.v. injection of 0.75 nmole of DY647-labelled aptamers or FITC-labeled EpCAM antibodies. The whole body imaging was performed using the IVIS Live Imaging System. Fluorescence signals obtained from aptamers or antibodies at the regions of interest (ROIs) of tumor sites were recorded at a 5 min interval until the signal disappeared. The signal of aptamer on HT29 tumors appeared immediately and the maximum uptake was observed at around 10 min after i.v. injection and lasted for approximately 80 min (Fig. 3a and b). In sharp contrast, the signal for antibody observed in tumor sites had a slow onset, with the maximum uptake reached at 3 h. The signal in the tumor receiving EpCAM antibody lasted for at least 6 h. Thus, the aptamer achieved highest concentration in the tumor within 10 min and the signal in the tumor diminished at least 4.5-times faster than that of the antibody. Such quick onset of the maximum signal at the site of the tumor followed by rapid disappearance confers aptamer with highly desirable characteristics for function as a promising molecular imaging probe which outperform antibodies 44, 45.

Bottom Line: Targeted drug delivery to solid tumors followed by complete drug penetration and durable retention will significantly improve clinical outcomes of cancer therapy.To explore whether aptamers are superior to antibodies in terms of tumor penetration, we carried out the first comprehensive study to compare the performance of an EpCAM aptamer with an EpCAM antibody in theranostic applications.We found that the EpCAM aptamer can not only effectively penetrate into the tumorsphere cores but can also be retained by tumor sphere cells for at least 24 h, while limited tumor penetration by EpCAM antibody was observed after 4 h incubation.

View Article: PubMed Central - PubMed

Affiliation: 1. School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria 3216, Australia.

ABSTRACT
Insufficient penetration of therapeutic agents into tumor tissues results in inadequate drug distribution and lower intracellular concentration of drugs, leading to the increase of drug resistance and resultant failure of cancer treatment. Targeted drug delivery to solid tumors followed by complete drug penetration and durable retention will significantly improve clinical outcomes of cancer therapy. Monoclonal antibodies have been commonly used in clinic for cancer treatment, but their limitation of penetrating into tumor tissues still remains because of their large size. Aptamers, as "chemical antibodies", are 15-20 times smaller than antibodies. To explore whether aptamers are superior to antibodies in terms of tumor penetration, we carried out the first comprehensive study to compare the performance of an EpCAM aptamer with an EpCAM antibody in theranostic applications. Penetration and retention were studied in in vitro three-dimensional tumorspheres, in vivo live animal imaging and mouse colorectal cancer xenograft model. We found that the EpCAM aptamer can not only effectively penetrate into the tumorsphere cores but can also be retained by tumor sphere cells for at least 24 h, while limited tumor penetration by EpCAM antibody was observed after 4 h incubation. As observed from in vivo live animal imaging, EpCAM aptamers displayed a maximum tumor uptake at around 10 min followed by a rapid clearance after 80 min, while the signal of peak uptake and disappearance of antibody appeared at 3 h and 6 h after intravenous injection, respectively. The signal of PEGylated EpCAM aptamers in xenograft tumors was sustained for 26 h, which was 4.3-fold longer than that of the EpCAM antibody. Consistently, there were 1.67-fold and 6.6-fold higher accumulation of PEGylated aptamer in xenograft tumors than that of antibody, at 3 h and 24 h after intravenous administration, respectively. In addition, the aptamer achieved at least a 4-time better tumor penetration in xenograft tumors than that of the antibody at a 200 μm distances from the blood vessels 3 h after intravenous injection. Taken together, these data indicate that aptmers are superior to antibodies in cancer theranostics due to their better tumor penetration, more homogeneous distribution and longer retention in tumor sites. Thus, aptamers are promising agents for targeted tumor therapeutics and molecular imaging.

No MeSH data available.


Related in: MedlinePlus