AS30D model of hepatocellular carcinoma: tumorigenicity and preliminary characterization by imaging, histopathology, and immunohistochemistry

Quantitative Expression of Key Cancer Markers in the AS-30D Hepatocarcinoma Model

Hepatocellular carcinoma is one of the cancers with the highest mortality rate worldwide. HCC is often diagnosed when the disease is already in an advanced stage, making the discovery and implementation of biomarkers for the disease a critical aim in cancer research. In this study, we aim to quantify the transcript levels of key signaling molecules relevant to different pathways known to participate in tumorigenesis, with special emphasis on those related to cancer hallmarks and epithelial-mesenchymal transition, using as a model the murine transplantable hepatocarcinoma AS-30D. Using qPCR to quantify the mRNA levels of genes involved in tumorigenesis, we found elevated levels for Tgfb1 and Spp1, two master regulators of EMT. A mesenchymal signature profile for AS-30D cells is also supported by the overexpression of genes encoding for molecules known to be associated to aggressiveness and metastatic phenotypes such as Foxm1, C-met, and Inppl1. This study supports the use of the AS-30D cells as an efficient and cost-effective model to study gene expression changes in HCC, especially those associated with the EMT process.

Heat Stress and Thermal Ablation Induce Local Expression of Nerve Growth Factor Inducible (VGF) in Hepatocytes and Hepatocellular Carcinoma: Preclinical and Clinical Studies

The purposes of this study were to test the hypothesis that heat stress and hepatic thermal ablation induce nerve growth factor inducible (VGF) and to determine intrahepatic versus systemic VGF expression induced by thermal ablation in vivo and in patients. Hepatocytes and HCC cells were subjected to moderate (45°C) or physiologic (37°C) heat stress for 10 min and assessed for VGF expression at 0-72 h post-heat stress (n ≥ 3 experiments). Orthotopic N1S1 HCC-bearing rats were randomized to sham or laser thermal ablation (3 W × 90 s), and liver/serum was harvested at 0-7 days postablation for analysis of VGF expression (n ≥ 6 per group). Serum was collected from patients undergoing thermal ablation for HCC (n = 16) at baseline, 3-6, and 18-24 h postablation and analyzed for VGF expression. Data were analyzed using ordinary or repeated-measures one-way analysis of variance and post hoc pairwise comparison with Dunnett's test. Moderate heat stress induced time-dependent VGF mRNA (3- to 15-fold; p < 0.04) and protein expression and secretion (3.1- to 3.3-fold; p < 0.05). Thermal ablation induced VGF expression at the hepatic ablation margin at 1 and 3 days postablation but not remote from the ablation zone or distant intrahepatic lobe. There was no detectable serum VGF following hepatic thermal ablation in rats and no increase in serum VGF following HCC thermal ablation in patients at 3-6 and 18-24 h postablation compared to baseline (0.71- and 0.63-fold; p = 0.27 and p = 0.16, respectively). Moderate heat stress induces expression and secretion of VGF in HCC cells and hepatocytes in vitro, and thermal ablation induces local intrahepatic but not distant intrahepatic or systemic VGF expression in vivo.

Modified Rat Hepatocellular Carcinoma Models Overexpressing Vascular Endothelial Growth Factor

PURPOSE

To compare tumor vascularity in 4 types of rat hepatocellular carcinoma (HCC) models: N1S1, vascular endothelial growth factor (VEGF)-transfected N1S1 (VEGF-N1S1), McA-RH7777, and VEGF-transfected McA-RH7777 (VEGF-McA-RH777) tumors.

MATERIALS AND METHODS

The N1S1 and McA-RH7777 cell lines were transfected with expression vectors containing cDNA for rat VEGF. Eighty-eight male Sprague-Dawley rats (weight range, 400-450 g) were randomly divided into 4 groups (ie, 22 rats per model), and 4 types of tumor models were created by using the N1S1, VEGF-N1S1, McA-RH7777, and VEGF-McA-RH777 cell lines. Tumor vascularity was evaluated by perfusion computed tomography (CT), enzyme-linked immunosorbent assay of VEGF, CD34 staining, angiography, and Lipiodol transarterial embolization. Intergroup discrepancies were evaluated by Kruskal-Wallis test.

RESULTS

Arterial perfusion (P < .001), portal perfusion (P = .015), total perfusion (P < .001), tumor VEGF level (P = .002), and microvessel density (MVD; P = .007) were significantly different among groups. VEGF-McA-RH7777 tumors showed the greatest arterial perfusion (46.7 mL/min/100 mL ± 15.5), total perfusion (60.7 mL/min/100 mL ± 21.8), tumor VEGF level (3,376.7 pg/mL ± 145.8), and MVD (34.5‰ ± 7.5). Whereas most tumors in the N1S1, VEGF-N1S1, and McA-RH7777 groups showed hypovascular staining on angiography and minimal Lipiodol uptake after embolization, 5 of 6 VEGF-McA-RH7777 tumors (83.3%) presented hypervascular tumor staining and moderate to compact Lipiodol uptake.

CONCLUSIONS

McA-RH7777 tumors were more hypervascular than N1S1 tumors, and tumor vascularity was enhanced further by VEGF transfection. Therefore, the VEGF-McA-RH7777 tumor is recommended to mimic hypervascular human HCC in rats.

Heat Stress and Hepatic Laser Thermal Ablation Induce Hepatocellular Carcinoma Growth: Role of PI3K/mTOR/AKT Signaling

Purpose To determine if heat stress and hepatic laser thermal ablation induce hepatocellular carcinoma (HCC) growth and to identify growth factors induced by heat stress. Materials and Methods Non-heat-stressed HCC cells were cocultured with HCC cells or hepatocytes that were heat stressed at 37°C (physiologic), 45°C (moderate), or 50°C (severe) for 10 minutes and proliferation monitored with bioluminescence imaging for up to 6 days after heat stress (three experiments). Rats bearing orthotopic N1S1 HCC were randomly assigned to undergo immediate sham or laser thermal (3 W for 60 or 90 seconds; hereafter, 3W×60s and 3W×90s, respectively) ablation of the median (local) or left (distant) hepatic lobe, and tumor growth was monitored with magnetic resonance imaging for up to 18 days after ablation (six or more rats per group). Experiments were repeated with rats randomly assigned to receive either the adjuvant phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitor (NVP-BEZ235) or the vehicle control. Heat-stressed HCC cells and hepatocytes were analyzed by using microarray or quantitative real-time polymerase chain reaction analysis for growth factor expression (three or more experiments). Groups were compared by using one- or two-way analysis of variance, and post hoc pairwise comparison was performed with the Dunnett test. Results There were more non-heat-stressed HCC cells when cells were cocultured with cells subjected to moderate but not physiologic or severe heat stress (P < .001 for both). Local intrahepatic N1S1 tumors were larger at day 18 in the 3W×60s (mean, 3102 mm³ ± 463 [standard error]; P = .004) and 3W×90s (mean, 3538 mm³ ± 667; P < .001) groups than in the sham group (mean, 1363 mm³ ± 361) but not in distant intrahepatic tumors (P = .31). Adjuvant BEZ235 resulted in smaller N1S1 tumors in the BEZ235 and laser thermal ablation group than in the vehicle control and laser thermal ablation group (mean, 1731 mm³ ± 1457 vs 3844 mm³ ± 2400, P < .001). Moderate heat stress induced expression of growth factors in HCC cells and hepatocytes, including heparin-binding growth factor, fibroblast growth factor 21, and nerve growth factor (range, 2.9-66.9-fold; P < .05). Conclusion Moderate heat stress and laser thermal ablation induce hepatocellular carcinoma growth, which is prevented with adjuvant PI3K/mTOR/protein kinase B inhibition.

Heat stress induced, ligand-independent MET and EGFR signalling in hepatocellular carcinoma

PURPOSE

The aims of the present study were 2-fold: first, to test the hypothesis that heat stress induces MET and EGFR signalling in hepatocellular carcinoma (HCC) cells and inhibition of this signalling decreases HCC clonogenic survival; and second, to identify signalling pathways associated with heat stress induced MET signalling.

MATERIALS AND METHODS

MET⁺ and EGFR⁺ HCC cells were pre-treated with inhibitors to MET, EGFR, PI3K/mTOR or vehicle and subjected to heat stress or control ± HGF or EGF growth factors and assessed by colony formation assay, Western blotting and/or quantitative mass spectrometry. IACUC approved partial laser thermal or sham ablation was performed on orthotopic N1S1 and AS30D HCC tumours and liver/tumour assessed for phospho-MET and phospho-EGFR immunostaining.

RESULTS

Heat-stress induced rapid MET and EGFR phosphorylation that is distinct from HGF or EGF in HCC cells and thermal ablation induced MET but not EGFR phosphorylation at the HCC tumour ablation margin. Inhibition of the MET and EGFR blocked both heat stress and growth factor induced MET and EGFR phosphorylation and inhibition of MET decreased HCC clonogenic survival following heat stress. Pathway analysis of quantitative phosphoproteomic data identified downstream pathways associated with heat stress induced MET signalling including AKT, ERK, Stat3 and JNK. However, inhibition of heat stress induced MET signalling did not block AKT signalling.

CONCLUSIONS

Heat-stress induced MET and EGFR signalling is distinct from growth factor mediated signalling in HCC cells and MET inhibition enhances heat stress induced HCC cell killing via a PI3K/AKT/mTOR-independent mechanism.

Heat Stress-Induced PI3K/mTORC2-Dependent AKT Signaling Is a Central Mediator of Hepatocellular Carcinoma Survival to Thermal Ablation Induced Heat Stress

Thermal ablative therapies are important treatment options in the multidisciplinary care of patients with hepatocellular carcinoma (HCC), but lesions larger than 2–3 cm are plagued with high local recurrence rates and overall survival of these patients remains poor. Currently no adjuvant therapies exist to prevent local HCC recurrence in patients undergoing thermal ablation. The molecular mechanisms mediating HCC resistance to thermal ablation induced heat stress and local recurrence remain unclear. Here we demonstrate that the HCC cells with a poor prognostic hepatic stem cell subtype (Subtype HS) are more resistant to heat stress than HCC cells with a better prognostic hepatocyte subtype (Subtype HC). Moreover, sublethal heat stress rapidly induces phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) dependent-protein kinase B (AKT) survival signaling in HCC cells in vitro and at the tumor ablation margin in vivo. Conversely, inhibition of PI3K/mTOR complex 2 (mTORC2)-dependent AKT phosphorylation or direct inhibition of AKT function both enhance HCC cell killing and decrease HCC cell survival to sublethal heat stress in both poor and better prognostic HCC subtypes while mTOR complex 1 (mTORC1)-inhibition has no impact. Finally, we showed that AKT isoforms 1, 2 and 3 are differentially upregulated in primary human HCCs and that overexpression of AKT correlates with worse tumor biology and pathologic features (AKT3) and prognosis (AKT1). Together these findings define a novel molecular mechanism whereby heat stress induces PI3K/mTORC2-dependent AKT survival signaling in HCC cells and provide a mechanistic rationale for adjuvant AKT inhibition in combination with thermal ablation as a strategy to enhance HCC cell killing and prevent local recurrence, particularly at the ablation margin.

Characterization of CC-531 as a Rat Model of Colorectal Liver Metastases

Purpose

Surgical resection of colorectal liver metastases is not achievable in more than 70% of the cases. Although the liver directed therapies have become a part of the stand of care, lack of a preclinical model impedes the assessment of toxicity and therapeutic benefits attributed several candidate drugs or treatment regimens that can be designed. In the present study we aim develop and characterize a rat colorectal liver metastasis model.

Materials and Methods

Growth characteristics of CC-531 cells were determined in vitro followed by subcapsular liver implantation in syngeneic WAG/Rij rats. Tumor growth progression was followed over 3 weeks by ultrasound (US) and magnetic resonance imaging (MRI). Growth characteristics were also assessed by histopathology and immunohistochemistry in harvested tumor tissues.

Results

The doubling time of CC-531 cells was found be under 24hrs and all the implanted rats grew tumors. US imaging showed hypoechoic masses and MRI showed contrast enhancement representing complex tumor microenvironments. Hematoxylin and Eosin staining confirmed tumor growth and uniform CD31 staining in tumor confirmed even vessel density.

Conclusion

CC-531 can be used as a metastatic rat tumor colorectal liver metastases model with well-defined characteristics that can be readily followed by imaging whilst having a therapeutic window for interventions.

Comparison of tumor vascularity and hemodynamics in three rat hepatoma models

PURPOSE

To compare tumor vascularity and hemodynamics in three rat hepatoma models: N1-S1 cells in Sprague-Dawley rats, McA-RH7777 cells in Sprague-Dawley rats, and 13762 MAT B III cells in F344 rats.

METHODS

The three rat hepatoma models were induced in five rats per group. After confirming that the tumors grew up to 10 mm on magnetic resonance imaging, the rats underwent dynamic contrast-enhanced ultrasonography (DCE-US). Afterward, the rats were euthanized for histologic analyses. The Kruskal-Wallis test was used to compare the rat hepatoma models. Correlation coefficients were calculated between the microvessel density (MVD) and DCE-US parameters.

RESULTS

On DCE-US imaging, arterial enhancement and washout were demonstrated in all N1-S1 tumors, while persistent peripheral enhancement on arterial to portal phases was shown in all 13762 MAT B III tumors. The McA-RH7777 tumors presented diverse enhancement patterns on arterial and portal phases. There were no significant differences in DCE-US parameters among the three hepatoma groups, while MVD was correlated with peak intensity (r = 0.565, p = 0.044), mean transit time (r = -0.559, p = 0.047), and time to peak (r = - 0.617, p = 0.025) of individual rats. The necrosis ratio was significantly different between the models (p = 0.031); 13762 MAT B III showed a significantly higher necrosis ratio than N1-S1 (p < 0.050 by post hoc test).

CONCLUSION

The N1-S1 tumor may be suitable as a model to investigate hypervascular hepatic tumors of the liver in DCE-US such as hepatocellular carcinoma among the three tumors.

Evaluation of Selective Arterial Embolization Effect by Chitosan Micro-Hydrogels in Hindlimb Sarcoma Rodent Models Using Various Imaging Modalities

PURPOSE

Embolization is mainly used to reduce the size of locally advanced tumors. In this study, selective arterial catheterization with chitosan micro-hydrogels (CMH) into the femoral artery was performed and the therapeutic effect was validated using different imaging methods.

METHODS

Male SD rats (n = 18, 6 weeks old) were randomly assigned into three groups: Group 1 as control, Group 2 without any ligation of distal femoral artery, and Group 3 with temporary ligation of the distal femoral artery. RR1022 sarcoma cell lines were inoculated into thigh muscle. After 1 week, CMH was injected into the proximal femoral artery. Different imaging modalities were performed during a 3-week follow-up.

RESULTS

The tumor size was significantly (P < 0.001) decreased in both Group 2 and Group 3 (P < 0.001) after selective arterial embolization therapy. (18)F-FDG-PET/CT revealed decreased intensity of (18)F-FDG uptake in tumors. The accumulation status of (125)I-CMH near the tumor was verified by gamma camera.

CONCLUSIONS

Appropriate selective arterial embolization therapy with CMH was.

Establishment of animal models with orthotopic hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most serious health problems worldwide. Many researchers have investigated HCC at the level of genes, ribonucleic acid, proteins, cells, and animals. The resultant development of animal models and monitoring methods has improved the effectiveness of guidelines provided to researchers working with preclinical HCC models. HCC in animal models and clinical patients is monitored by various current imaging modalities such as ultrasound (US) imaging, computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), positron emission tomography (PET) and bioluminescence imaging (BLI). These techniques are currently used for both preclinical and clinical assessment, and provide valuable diagnostic information. In this article, we have mainly reviewed the established animal models and the assessment of orthotopic HCC using imaging modalities. Additionally, we have introduced a method of orthotopic HCC rat model developed in our laboratory. We have furthermore evaluated the occurrence of tumor mass using molecular imaging techniques.

Establishment of a lung metastatic breast tumor xenograft model in nude rats

Objective

Larger animal models provide relevant tumor burden in the development of advanced clinical imaging methods for non-invasive cancer detection and diagnosis, and are especially valuable for studying metastatic disease. Most available experimental models, however, are based on immune-compromised mice. To lay the foundation for studying spontaneous metastasis using non-invasive magnetic resonance imaging (MRI), this study aims to establish a highly metastatic breast cancer xenograft model in nude rats.

Materials and Methods

A highly metastatic variant of human adenocarcinoma MDA-MB-231 known as LM2 was inoculated into nude rats. Orthotopic and subcutaneous (flank) sites were compared, with half of the orthotopic injections guided by ultrasound imaging. MRI with gadolinium contrast administration was performed weekly beginning on Day 6 and ending on Day 104. Excised tumors were assessed on histology using hematoxylin and eosin and CD34. Fisher's exact test was used to compare successful tumor induction amongst different inoculation methods.

Results

Primary LM2 tumors were established orthotopically in all cases under ultrasound-guided injection, and none otherwise (p = 0.0028). Contrast-enhanced MRI revealed rapidly progressing tumors that reached critical size (15 mm diameter) in 2 to 3 weeks after inoculation. MRI and histology findings were consistent: LM2 tumors were characterized by low vascularity confined to the tumor rim and large necrotic cores with increasing interstitial fluid pressure.

Conclusions

The metastatic LM2 breast tumor model was successfully established in the mammary fat pads of nude rats, using ultrasound needle guidance as a non-invasive alternative to surgery. This platform lays the foundation for future development and application of MRI to study spontaneous metastasis and different stages throughout the metastatic cascade.

Heat stress induced cell death mechanisms in hepatocytes and hepatocellular carcinoma: in vitro and in vivo study

BACKGROUND AND OBJECTIVE

The aims of the present study were to investigate the thermal-dose dependent effect of heat stress on hepatocyte and HCC cell death mechanisms using clinically relevant experimental heat stress conditions in vitro and to investigate apoptotic cell death induced by laser thermal ablation in vivo.

STUDY DESIGN/MATERIALS AND METHODS

Institutional Animal Care and Use Committee approved all studies. Hepatocyte and HCC cell lines were heat stressed from 37 to 60°C for 2 or 10 minutes and assessed for viability, cytotoxicity and caspase-3/7 activity at 6 and/or 24 hours post-treatment (N = 3). Viability experiments were repeated with the RIPK1 inhibitor Necrostatin-1 to block necroptosis (N = 3). Rats with orthotopic HCC tumors stably expressing luciferase (N1S1luc2) were randomized to US-guided laser ablation (3W-45s for an intentional partial ablation; N = 6) or sham (N = 6) and followed by post-ablation caspase-3/7 bioluminescence imaging at 6 and 24 hours and cleaved caspase-3 immunostaining. P < 0.05 was considered statistically significant.

RESULTS

Heat-stress induced apoptosis and necrosis in hepatocytes and HCC cells in a thermal dose and cell-type dependent manner. Inhibition of RIPIK1-mediated necroptosis induced a significant, differential increase in HCC cell viability under physiologic and hyperthermic heat stress (P < 0.001). Intentional partial laser thermal ablation induced a significant increase in caspase-3/7 activity in the laser versus sham ablation groups at both 6 hours (10.1-fold, P < 0.01) and 24 hours (16.7-fold, P < 0.02). Immunohistochemistry confirmed increased cleaved caspase-3 staining at the tumor ablation margin 24 hours post-ablation.

CONCLUSIONS

Both regulated and non-regulated cell death mechanisms mediate heat stress-induced HCC cell killing and vary between hepatocytes and HCC subtypes. Apoptosis is a significant mechanism of cell death at the HCC tumor ablation margin.

Role for putative hepatocellular carcinoma stem cell subpopulations in biological response to incomplete thermal ablation: in vitro and in vivo pilot study

PURPOSE

To investigate the potential role for CD44(+) and CD90(+) hepatocellular carcinoma (HCC) cellular subpopulations in biological response to thermal ablation-induced heat stress.

METHODS

This study was approved by the institutional animal care committee. The N1S1 rat HCC cell line was subjected to sublethal heat stress (45 °C) or control (37 °C) for 10 min, costained with fluorescent-labeled antibodies against CD44, CD90, and 7-AAD after a 48-h recovery and analyzed by flow cytometry to assess the percentage of live CD44(+) and CD90(+) HCC cells (n = 4). Experiments were repeated with pretreatment of N1S1 cells with a dose titration of the dual PI3K-mTOR inhibitor BEZ235 or vehicle control (n = 3). Rats bearing orthotopic N1S1 tumors were subjected to ultrasound-guided partial laser ablation (n = 5) or sham ablation (n = 3), euthanized 24 h after ablation, and liver/tumor analyzed for immunohistochemical staining of CD44 and CD90. Differences between groups were compared with an unpaired t test.

RESULTS

Sublethal heat stress induced a significant increase in the relative proportion of live CD44(+) and CD90(+) HCC cells compared to the control group: CD44(+)CD90(-) (5.3-fold; p = 0.0001), CD44(-)CD90(+) (2.4-fold; p = 0.003), and CD44(+)CD90(+) (22.0-fold; p < 0.03). Inhibition of PI3K-mTOR prevented heat stress-induced enrichment of the population of live CD44(+) HCC cells (p < 0.01), but not CD90(+) cells (p > 0.10). Immunohistochemical analysis demonstrated preferential localization of clusters of CD44(+) cells at both the tumor margin and ablation margin.

CONCLUSION

These studies provide experimental evidence supporting a role for HCC cells expressing the putative stem cell marker CD44 in HCC response to heat stress.

Molecular bioluminescence imaging as a noninvasive tool for monitoring tumor growth and therapeutic response to MRI-guided laser ablation in a rat model of hepatocellular carcinoma

OBJECTIVES

The objective of this study was to quantitatively compare tumor imaging by magnetic resonance imaging (MRI) and molecular bioluminescence imaging (BLI) and test the feasibility of monitoring the effect of MRI-guided laser ablation on tumor viability by 2-dimensional BLI and 3-dimensional diffuse luminescence tomography (3D DLIT) in an orthotopic rat model of hepatocellular carcinoma.

MATERIALS AND METHODS

This study was approved by the animal care committee. Rats underwent injection of N1S1 cells stably transfected with an empty vector (n = 3) or a heat shock element luciferase reporter (HSE-luc; n = 4) into the liver. All rats underwent MRI to assess tumor establishment and volume and 2-dimensional BLI to assess tumor luminescence at day 7 with subsequent MRI and 2D BLI and 3D DLIT in select animals at days 14 and 21. Magnetic resonance imaging-guided laser ablation of the tumor was performed with preablation and postablation 2D BLI and/or 3D DLIT (n = 2). The tumors underwent histopathologic analysis to assess tumor viability.

RESULTS

The MRI scans demonstrated hyperintense T2-weighted lesions at 3 of 3 and 4 of 4 sites in the empty vector and HSE-luc rats, respectively. Two-dimensional BLI quantitation demonstrated 23.0-fold higher radiance in the HSE-luc group compared with the empty vector group at day 7 (P < 0.01) and a significant correlation with tumor volume by MRI (r = 0.86; P < 0.03). Tumor dimensions by 3D DLIT and MRI demonstrated good agreement. Three-dimensional DLIT quantitation demonstrated better agreement with the percentage of nonviable tumor by histopathology than did 2D BLI quantitation after the MRI-guided laser ablation.

CONCLUSIONS

Bioluminescence imaging is feasible as a noninvasive, quantitative tool for monitoring tumor growth and therapeutic response to thermal ablation in a rat model of hepatocellular carcinoma.