Drug-Eluting, Radiopaque, Tumor-Casting Hydrogels for Endovascular Locoregional Therapy of Hepatocellular Carcinoma

Abstract

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. For patients with unresectable disease, locoregional therapies, such as transarterial chemoembolization (TACE), are the standard of care. However, even with this treatment, the average survival rate is only 27% at 5 years. Recent studies have demonstrated the potential of novel approaches to improve responses through more complete embolization and targeting ischemia-induced molecular dependencies. To build on these findings, we developed an injectable chitosan-based hydrogel system (AuNP-Lys05-gel) that we hypothesized might be a more effective embolic material by (i) enabling a more complete filling of tumor feeding blood vessels in a cast-like manner, (ii) encapsulating Lys05, a potent autophagy inhibitor, and (iii) providing X-ray contrast for direct visualization of the embolization. Chitosan hydrogels of varying composition were formed and characterized. We found that Lys05 could be loaded in this type of hydrogel and that it was released gradually over 7 days. We found that AuNP was better retained by the hydrogel than iopamidol, an FDA-approved contrast agent, indicating that AuNP would provide longer-lasting CT monitoring. In a rat model of HCC, AuNP-Lys05-gel reduced tumor growth and resulted in a 67% objective response rate vs 26% for a clinically used particle embolic. Histology indicated effective vascular occlusion by the gel. These findings indicate that AuNP-Lys05-gel merits further investigation as a treatment for HCC.

Figure 1. Characterizations of thermosensitive hydrogels

(A) Photos of thermosensitive hydrogels loaded with AuNP and Lys05. (B) TEM micrograph of sub-5 nm AuNP dispersed in the hydrogel. (C) Hydrogels with different polymer/crosslinker mass ratio and their corresponding pH, gelation time and viscosity.

Figure 2. Rheological characterization of hydrogels.

Temperature-dependent storage modulus of hydrogels with different polymer to crosslinker mass ratios measured using oscillatory shear rheometry.

Figure 3. Release profiles of AuNP, iodine molecules, Lys05, and DOX from hydrogels.

Release profiles of (A) AuNP and iodinated molecules, as well as (B) Lys05 and DOX from hydrogels over 20 days.

Figure 4. Phantom imaging of AuNP-Lys05 hydrogels with CT

(A) CT phantom image and (B) X-ray attenuation changes versus concentration for hydrogels scanned by a microCT system.

Figure 5. In vitro cytocompatibility and cytotoxicity of AuNP-Lys05 hydrogels.

(A) Viability of cells incubated with hydrogel degradation byproducts and released AuNP. (B) Viability of Huh 7 cells after receiving treatment with drugs eluted from hydrogels.

Figure 6

A) Representative MR images of liver tumors treated with either sham or AuNP-Lys05-gel (‘Gel’) in the DEN rat model. CT scans of the liver of a rat B) before and C) two days post administration of AuNP-Lys05-gel (indicated by red star) into an HCC tumor. RECIST criteria responses of tumors to D) sham, E) AuNP-Lys05-gel and F) PE treatment. CR = complete response, PR = partial response, SD = stable disease and PD = progressive disease. G) Objective response rate of tumor treated with AuNP-Lys05-gel or PEs (* = p<0.05).

Figure 7

(A) Histology of tumors that were embolized either with AuNP-Lys05-gel or underwent a sham procedure. Stains are hematoxylin and eosin (H&E) and Cibacron Brilliant Red-3BA (CBR-3BA). (B) Electron microscopy of tumor tissue embolized with AuNP-Lys05-gel.