Local targeted therapy of liver metastasis from colon cancer by galactosylated liposome encapsulated with doxorubicin

Abstract

Since regional drug administration enables to maintain a high drug concentration within tumors, we compared the plasma concentration and biodistribution of doxorubicin (Dox) from drug-loaded conventional liposomes by local or systemic administration. The results demonstrated that drug concentration was substantially improved in liver as well as a decrease in blood and other organs by spleen injection mimicking portal vein perfusion (regional administration). To further investigate the targeted therapeutic effect of galactosylated liposome encapsulated doxorubicin (Dox) by regional administration, liver targeting liposomes were prepared by incorporating galactosylated-DPPE to conventional liposomes. Liposome uptake and targeting were verified in vitro and in vivo by fluorescence microscopy and xenogen IVIS imaging system, respectively. The results showed that galactose targeted liposomes presented a stronger specific cell uptake by human hepatocellular carcinoma HepG2 cells compared to the non-targeted liposomes. In vivo fluorescence imaging showed that the intra-hepatic deposition of conventional and galactosylated liposomes via spleen injection was more than that via tail vein administration, and galactosylated liposomes had higher fluorescent intensity over conventional liposomes in the liver post spleen administration. The anti-tumor effect of various drug administration routes for both liposomal formulations was evaluated using a murine liver metastasis model of colon cancer. The results indicated that tumor progression in the liver and mesenteric lymph nodes was significantly suppressed by Dox-loaded galactosylated liposomes via spleen injection, while no significance was observed in non-targeted formulations. Our data indicated that local perfusion of galactosylated liposomal doxorubicin had a great promise for the treatment of liver metastasis from colon cancer.

Figure 1. Doxorubicin concentration in plasma, liver, heart and kidney.

Liposomal doxorubicin at a loading dose of 6 mg/kg was introduced into Balb/c-nu mice via either spleen injection or i.v. injection. After drug administration, the blood, liver, heart and kidney were collected from treated mice. Doxorubicin concentrations versus time in plasma (A), liver (B), heart (C) and Kidney (D) were determined by HPLC.

Figure 2. The effect of liposome concentration on cell uptake by ASGPR+/− cells.

The HCT-8 cells (ASGPR−) and HepG2 cells (ASGPR+) were incubated with either conventional liposomes (CL) or galactosylated liposomes (Gal-lipo) for 2 hrs at different lipid concentration ranging from 10 µM to 100 µM. Cellular uptake of liposomes was visualized under fluorescence microscopy due to the incorporation of 25-NBD-cholesterol into liposomes. The mean fluorescence intensity presented by cells was determined using Image-Pro Plus Imaging software (Media Cybernetics). A) Fluorescence imaging of cellular uptake of liposomes. B) Quantitative analysis of the mean fluorescence intensity. “*” indicates significant difference (p<0.001). CL: conventional liposomes; Gal: galactosylated liposomes.

Figure 3. The effect of incubation time on cell uptake by ASGPR+/− cells.

The HCT-8 cells (ASGPR−) and HepG2 cells (ASGPR+) were incubated with either conventional liposomes (CL) or galactosylated liposomes (Gal-lipo) at 37°C for different time duration. Cellular uptake of liposomes labeled by 25-NBD-cholesterol was visualized under fluorescence microscopy. The mean fluorescence intensity representing durg uptake was determined using Image-Pro Plus Imaging software. A) Fluorescence imaging of cellular uptake of liposomes. B) Quantitative analysis of the mean fluorescence intensity for the treatment of 1 hr incubation. “*” indicates significant difference (p<0.001). CL: conventional liposomes; Gal: galactosylated liposomes.

Figure 4. The effect of temperature on cell uptake by ASGPR+/− cells.

The HCT-8 cells and HepG2 cells were incubated with either conventional liposomes (CL) or galactosylated liposomes (Gal-lipo) at 4°C for 1 hr, and then warmed to 37°C with continued incubation for an additional 1 hr. Cellular uptake of liposomes labeled by 25-NBD-cholesterol was visualized under fluorescence microscopy. The mean fluorescence intensity was quantitatively determined using Image-Pro Plus Imaging software. A) Fluorescence imaging of cellular uptake of liposomes. B) Quantitative analysis of the mean fluorescence intensity. “*” indicates significant difference (p<0.001). CL: conventional liposomes; Gal: galactosylated liposomes.

Figure 5. Distribution profiles of CL and Gal-lipo in the liver of mouse.

The conventional liposomes (CL) and galactosylated liposomes (Gal-lipo) were labeled by DiR. Each liposome containing a total of 200 µg of lipid was ininjected into Balb/c-nu mice via either tail intravenous or spleen administration. The in vivo biodistribution was monitored by a live animal imaging system with Ex/Em of 745 nm/820 nm at various time point post injection. The photon radiance on the surface of the liver of an animal was expressed as photons per second per square centimeter per steradian (p/sec/cm²/sr). Images are compound pictures generated by Living Image software. A) In vivo longitudinal monitoring of both liposomes. B) The analysis of fluorescence imaging using Living Image software.

Figure 6. The anti-tumor effect of Dox-loaded galactosylated liposomes in animal model via spleen injection.

Three formulations (Dox alone, CL-Dox and Gal-Dox) were introduced into tumor-bearing mice on day 7 post cell inoculation via two administration routes, tail vein injection and spleen injection. The drug dose administrated was 6 mg/kg. A) Tumor progression in liver was assessed by the mean value of hepatic tumor weight. B) Mesenteric lymph node metastasis was assessed by the mean weight of metastatic carcinoma from mesenteric lymph node. The results represent the mean ± SE. “*” indicate significant difference (p<0.05).

Figure 7. Microscopy images of H&E stained normal liver tissue slides.

The normal liver tissues from groups treated with three drug formulations via spleen injection and PBS groups were collected and fixed using 10% formalin for 24 hrs at room, and then hematoxylin and eosin staining (H&E staining) was carried out. Magnification = 400×.