Polymer Nanoformulation of Sorafenib and All-Trans Retinoic Acid for Synergistic Inhibition of Thyroid Cancer

Abstract

Part of differentiated thyroid cancer will relapse or develop into dedifferentiated thyroid cancer after standard therapy, such as surgery or radionuclide therapy. Sorafenib (SOR) is recommended for the treatment of advanced or radioiodine-refractory thyroid cancer. The monotherapy using SOR is often hampered by its modest efficacy, serve systemic toxicity, and high occurrence of drug resistance. In order to enhance the antitumor effect of SOR and reduce its side effects, SOR and all-trans retinoic acid (ATRA), a differentiation-promoting drug, were loaded into poly(ethylene glycol)-poly(lactide-co-glycolide) (PEG-PLGA) polymer micelles in this study. The drug-loaded micelles, PM/(SOR+ATRA), exhibited relatively slow drug release and effective cell uptake. Compared with other treatment groups, the PM/(SOR+ATRA) treatment group showed the most significant antitumor effect and minimal systemic toxicity toward the FTC-133 thyroid cancer-bearing BALB/c nude mouse model. Immunofluorescence analysis confirmed that PM/(SOR+ATRA) could significantly promote apoptosis and re-differentiation of tumor cells. All the results demonstrated that polymer micelles loaded with SOR and ATRA could treat thyroid cancer more effectively and safely.

Keywords: all-trans retinoic acid; drug delivery system; polymer micelles; sorafenib; thyroid cancer.

Scheme 1

Schematic illustration of the preparation and proposed mechanism of the PEG–PLGA micelles loaded with SOR and ATRA.

Figure 1

Characterization of drug-loaded PEG–PLGA micelles. (A) DLS and (B) TEM analyses of PM/SOR, PM/ATRA, and PM/(SOR+ATRA). Scale bar = 200 nm.

Figure 2

In vitro characterization of SOR, ATRA, and drug-loaded PEG–PLGA polymer micelles. (A) Release behavior of SOR and ATRA in PBS. Cell uptake of (B) SOR and (C) ATRA by FTC-133 cells after co-incubation for 2 h. In vitro cytotoxicity of (D) SOR, (E) ATRA, and (F) SOR + ATRA on FTC-133 cells. Data are presented as mean ± SD (n = 3; ***P < 0.001).

Figure 3

In vivo behaviors of different formulations in the FTC-133 thyroid carcinoma-bearing BALB/c mouse model. (A) Tumor volumes. (B) Body weight of mice treated with different formulations, and the body weight of the mice on day 0 was set to 1. (C) H&E staining and (D) tumor necrosis area of the tumor tissues obtained from the mouse models treated with different formulations. Data are presented as mean ± SD (in A, B, n = 5, in C, D, n = 3; *P < 0.05, **P < 0.01, ***P < 0.001). Scale bar = 100 μm.

Figure 4

Immunofluorescence staining and semi-quantitative analyses of tumor tissues obtained from the mouse models treated with different formulations. (A) Immunofluorescence staining and relative positive areas of (B) caspase-3, (C) Tg from the semi-quantitative analysis. Data are presented as mean ± SD (n = 3; *P < 0.05, **P < 0.01). Scale bar = 200 μm.

Figure 5

Immunofluorescence staining and semi-quantitative analyses of tumor tissues obtained from the mouse models treated with different formulations. (A) Immunofluorescence staining and relative positive areas of (B) NIS and (C) p-ERK2 from the semi-quantitative analysis. Data are presented as mean ± SD (n = 3; *P < 0.05, **P < 0.01, ***P < 0.001). Scale bar = 200 μm.

Figure 6

Histological analysis of major organs (i.e., heart, liver, spleen, lung, and kidney) obtained from the mouse models treated with different formulations. Scale bar = 100 μm.