Modified Rat Hepatocellular Carcinoma Models Overexpressing Vascular Endothelial Growth Factor

Ideal Size Range for Embolic Agents in Interventional Oncology Experiments Involving Rat Models of Hepatocellular Carcinoma

PURPOSE

To optimize future translational research, this study aimed to determine the ideal range of sizes for embolic agents in interventional oncology experiments utilizing rat models of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Fifty-five male Sprague-Dawley rats were divided into 2 groups to evaluate the distribution of microparticles and tumor response rates. After implanting hepatoma cells into the rodent liver, fluorescent microparticles of sizes ranging from 5 to 35 μm were administered via the hepatic artery. In the first group, the distribution of microparticles was evaluated in hepatoma-free rats, and the tumor necrosis rates following administration of a predetermined aliquot of microparticles (0.4 mL) were measured in tumor-bearing rats. Thereafter, the 3 microparticle sizes associated with the best tumor response rates were chosen for analysis of the tumor necrosis rates following hepatic artery embolization until angiographic stasis is achieved in the second group.

RESULTS

The tendency for microparticles to distribute in nontarget organs increased as the microparticle size decreased below 15 μm. Tumor necrosis rates tended to be higher in rats treated with 15-19-μm microparticles than in those treated with 19-24-μm or 19-24-μm microparticles. The in-group deviation of the tumor necrosis rates was highest for microparticle sizes of 19-24 and 25-35 μm, which implies the proximal embolization of the hepatic artery for larger microparticle sizes. However, there was no statistical significance among the 3 groups (P = .095).

CONCLUSIONS

The 15-19-μm embolic agents were the most favorable for causing tumor necrosis without nontarget toxicity in the transarterial treatments of rat HCC models.

Drug delivery in transarterial chemoembolization of hepatocellular carcinoma: Ex vivo evaluation using transparent tissue imaging

In this study, we elucidated for the first time the role of anti-cancer drugs in transarterial chemoembolization (TACE) via direct visualization of the spatial distribution of drugs with respect to blood vessels in intact transparent hepatocellular carcinoma (HCC) tissues. To date, precise estimation of drug penetration into tumors using thin 3D tissue sections has been challenging. This study utilized the tissue optical clearing technique to resolve the lack of tissue clarity, thereby enabling deep tissue imaging for the quantitative assessment of drug delivery following TACE. We compared the drug delivery effect, time-dependent embolic effect, and immunogenic response following conventional TACE (cTACE), drug-eluting embolic TACE (DEE-TACE), and transarterial embolization (TAE) in a rat model of HCC. After each treatment, three-dimensional drug delivery was quantitatively evaluated via the transparent liver tumor imaging, and time-dependent tumor necrosis was analyzed by serial tumor harvesting and histological staining. The results showed that chemotherapeutic agents travel only short distances after cTACE (∼80µm) and DEE-TACE (∼110µm), whereas necrosis occurs extensively within 24 h of treatment (85.3-97.2% of tumor cells). In addition, the percentages of CD4 and IL-17+ CD4 T cells increased significantly following treatment; however, drug-loading did not appear to affect the immune response following TACE. In conclusion, transarterially delivered chemotherapeutic agents appeared to exert a limited role, owing to the rapid and overwhelming effect of embolization. STATEMENT OF SIGNIFICANCE: TACE has been widely used for the treatment of HCC, especially for unresectable intermediate and advanced HCCs. Drug use in TACE is expected to provide patients with synergistic therapeutic benefits with the effect of embolic agents; however, the role of chemotherapeutic agents in TACE remains controversial. This study quantitatively verified that chemotherapeutic agents travel only short distances after TACE, while necrosis occurs extensively within 24h, and drug loading does not significantly affect immune responses following TACE. Three-dimensional imaging of intact transparent HCC can contribute to a better understanding of drug delivery mechanisms associated with TACE and also reveal that drug use in TACE may need to be reconsidered and limited to situations when embolization is expected to be insufficient.

Animal Models of Hepatocellular Carcinoma for Local-Regional Intraarterial Therapies

Animal models play a crucial role in developing and testing new therapies for hepatocellular carcinoma (HCC), providing preclinical evidence prior to exploring human safety and efficacy outcomes. The interventional radiologist must weigh the advantages and disadvantages of various animal models available when testing a new local-regional therapy. This review highlights the currently available animal models for testing local-regional therapies for HCC and details the importance of considering animal genetics, tumor biology, and molecular mechanisms when ultimately choosing an animal model. Keywords: Animal Studies, Interventional-Vascular, Molecular Imaging-Clinical Translation, Molecular Imaging-Cancer, Chemoembolization, Liver © RSNA, 2022.

In Vivo Sol-Gel Reaction of Tantalum Alkoxide for Endovascular Embolization

Liquid embolic agents are considered the most promising for various embolization procedures because they enable deep penetration. For realizing effective procedures, the delivery of liquid embolic agents should be guided under X-ray imaging systems and the solidification time should be optimized for the specific indication. The biocompatibility of embolic agents is also crucial because they remain in the vessel after embolization. In this study, new biocompatible embolic agents based on tantalum ethoxide is synthesized. Tantalum alkoxide liquid embolics (TALE) possess the radiopacity for fluoroscopy and can control the penetration depth by modifying the sol-gel kinetics. Furthermore, TALE can serve as drug carriers for synergistic treatment. Using these excellent characteristics, it is demonstrated that TALE agents can be used in various situations including the transarterial chemoembolization of hepatocellular carcinoma and embolotherapy of massive bleeding from the femoral artery.

Screening and identification of angiogenesis-related genes as potential novel prognostic biomarkers of hepatocellular carcinoma through bioinformatics analysis

Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality, which makes the prognostic prediction challenging. Angiogenesis appears to be of critical importance in the progression and metastasis of HCC. Some of the angiogenesis-related genes promote this process, while other anti-angiogenesis genes suppress tumor growth and metastasis. Therefore, the comprehensive prognostic value of multiple angiogenesis-related genes in HCC needs to be further clarified. In this study, the mRNA expression profile of HCC patients and the corresponding clinical data were acquired from multiple public databases. Univariate Cox regression analysis was utilized to screen out differentially expressed angiogenesis-related genes with prognostic value. A multigene signature was established with the least absolute shrinkage and selection operator Cox regression in the Cancer Genome Atlas cohort, and validated through an independent cohort. The results suggested that a total of 16 differentially expressed genes (DEGs) were associated with overall survival (OS) and a 7-gene signature was constructed. The risk score of each patient was calculated using this signature, the median value of which was used to divide these patients into a high-risk group and a low-risk group. Compared with the low-risk group, the patients in the high-risk group had a poor prognosis. The risk score was an independent predictor for OS through multivariate Cox regression analysis. Then, unsupervised learning was used to verify the validity of this 7-gene signature. A nomogram by further integrating clinical information and the prognostic signature was utilized to predict prognostic risk and individual OS. Functional enrichment analyses demonstrated that these DEGs were enriched in the pathways of cell proliferation and mitosis, and the immune cell infiltration was significantly different between the two risk groups. In summary, a novel angiogenesis-related genes signature could be used to predict the prognosis of HCC and for targeted therapy.

Simple Host-Guest Assembly for High-Resolution Magnetic Resonance Imaging of Microvasculature

Magnetic resonance angiography (MRA) is an important imaging technique that can be used to identify and characterize various types of vascular diseases. However, currently used molecular contrast agents are unsuitable for MRA due to the short intravascular retention time, the whole-body distribution, and the relatively low contrast effect. In this study, we developed a vascular analysis contrast agent (i.e., VasCA) for MRA, which is a simple and biocompatible 1:1 host-guest assembly of PEGylated β-cyclodextrin and gadolinium chelate with renal clearable size and high relaxivity (r1 = 9.27 mM-1 s-1). Its biocompatibility was confirmed by in vivo animal studies as well as in vitro 3D cell culture. In a tumor-bearing rat model, VasCA circulated in the blood vessels much longer (4.3-fold increase) than gadoterate meglumine (Dotarem) and was mainly excreted by the renal system after intravenous injection. This feature of VasCA allows characterization of tumor microvasculature (e.g., feeding and draining vessels) as well as visualization of small vessels in the brain and body organs. Furthermore, after treatment with an angiogenesis inhibitor (i.e., sorafenib), VasCA revealed the vessel normalization process and allowed the assessment of viable and necrotic tumor regions. Our study provides a useful tool for diverse MRA applications, including tumor characterization, early-stage evaluation of drug efficacy, and treatment planning, as well as diagnosis of cardiovascular diseases.

Apatinib Combined With Transarterial Chemoembolization in Patients With Hepatocellular Carcinoma and Portal Vein Tumor Thrombus: A Multicenter Retrospective Study

PURPOSE

Studies focusing on the effects of combined transcatheter arterial chemoembolization (TACE) + the tyrosine kinase inhibitor apatinib in the treatment of patients with hepatocellular carcinoma (HCC), with the location and extent of portal vein tumor thrombus (PVTT) assessed as the main variable, are rare. This multicenter, retrospective, controlled study was performed to compare the efficacy and tolerability of TACE + apatinib and TACE alone in patients with HCC and PVTT.

METHODS

We retrospectively analyzed data from patients with nonresectable HCC and PVTT who underwent treatment with TACE + apatinib or TACE alone between January 2015 and January 2016. Outcomes in patients who underwent TACE + apatinib were compared with the outcomes of patients who underwent TACE alone, by using the Kaplan-Meier method, according to PVTT type: PVTT in the main portal vein (type A), PVTT in the first-order portal vein branch (type B), and PVTT in second- or lower-order portal vein branches (type C).

FINDINGS

One hundred eighty-eight patients were included in the analysis; 85 underwent treatment with TACE + apatinib and 103 underwent treatment with TACE. TACE + apatinib was associated with a significantly greater median survival compared with TACE alone in patients with PVTT type B (12.2 vs 7.5 months; P < 0.001) or type C (13.7 vs 7.2 months; P = 0.006). Along with treatment strategies and α-fetoprotein, the absence of main PVTT was an independent factor predictive of survival on uni- and multivariate analysis. Apatinib-related grade 3 adverse events occurred in 27 patients (31.8%).

IMPLICATIONS

TACE + apatinib can be of potential benefit to patients with advanced HCC with tumor thrombus in the first- and lower-order portal vein branches. Adverse events with apatinib need to be monitored during application, despite the manageable appearance.