Alpha-fetoprotein-thymidine kinase-luciferase knockin mice: a novel model for dual modality longitudinal imaging of tumorigenesis in liver

LINC00520 up-regulates SOX5 to promote cell proliferation and invasion by miR-4516 in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common human cancers. Long non-coding RNA (lncRNA) has been demonstrated to play an important role in regulating tumor development. The current study aims to explore the specific role of LINC00520 during HCC progression. The present study identified that LINC00520 was upregulated in HCC tissues and indicated poor patient survival. Overexpression of LINC00520 promoted HCC cell proliferation, migration and invasion, while LINC00520 downregulation led to the opposite effects. Besides, LINC00520 knockdown was found to inhibit tumor growth in vivo. Furthermore, LINC00520 acted as a sponge of miR-4516 to regulate SRY-related high mobility group box 5 (SOX5). In addition, the inhibition of miR-4516 partly reversed the inhibitory effect of LINC00520 silencing on HCC cell proliferation, migration and invasion. In conclusion, the inhibition of LINC00520 suppressed HCC cell proliferation, migration and invasion through mediating miR-4516/SOX5 axis. Therefore, our study provides a basis for the development of treatment strategies for HCC.

AFP promotes HCC progression by suppressing the HuR-mediated Fas/FADD apoptotic pathway

Hepatocellular carcinoma (HCC) is a major leading cause of cancer-related death worldwide. Alpha fetoprotein (AFP) is reactivated in a majority of hepatocellular carcinoma (HCC) and associated with poor patient outcomes. Although increasing evidence has shown that AFP can regulate HCC cell growth, the precise functions of AFP in hepatocarcinogenesis and the associated underlying mechanism remain incompletely understood. In this study, we demostrated that depleting AFP significantly suppressed diethylnitrosamine (DEN)-induced liver tumor progression in an AFP gene-deficient mouse model. Similarly, knocking down AFP expression inhibited human HCC cell proliferation and tumor growth by inducing apoptosis. AFP expression level was inversely associated with the apoptotic rate in mouse and human HCC specimens. Investigation of potential cross-talk between AFP and apoptotic signaling revealed that AFP exerted its growth-promoting effect by suppressing the Fas/FADD-mediated extrinsic apoptotic pathway. Mechanistically, AFP bound to the RNA-binding protein HuR, increasing the accumulation of HuR in the cytoplasm and subsequent inhibition of Fas mRNA translation. In addition, we found that inhibiting AFP enhanced the cytotoxicity of therapeutics to AFP-positive HCC cells by activating HuR-mediated Fas/FADD apoptotic signaling. Conclusion: Our study defined the pro-oncogenic role of AFP in HCC progression and uncovered a novel antiapoptotic mechanism connecting AFP to HuR-mediated Fas translation. Our findings suggest that AFP is involved in the pathogenesis and chemosensitivity of HCC and that blockade of AFP may be a promising strategy to treat advanced HCC.

Oleanolic Acid Suppressed DMBA-Induced Liver Carcinogenesis through Induction of Mitochondrial-Mediated Apoptosis and Autophagy

Phytochemicals appeared as a rich source of efficient and safe agents against many diseases like cancer. Various herbal sources are rich in oleanolic acid (OA). The scope of this study was to assess the biochemical and molecular mechanisms implicated in the ameliorative potency of OA against DMBA-induced liver carcinogenesis. Forty-eight male albino mice were assigned randomly to five groups (eight mice each) as follows: control healthy group, olive oil group, OA group, DMBA group, and DMBA with OA. Apoptosis, autophagy, inflammation, proliferation, and angiogenesis were investigated in the tissue samples. Histopathological examination was carried out as well as liver enzymes activity and other hepatic antioxidant and inflammatory biomarkers. The treatment with OA effectively suppressed the DMBA-initiated liver carcinogenesis via modulation of antioxidant status, induction of apoptosis and autophagy through modulating the expression of Caspase-3, Bcl-2 and Beclin-1, inhibiting angiogenesis (VEGF), proliferation (PCNA), and improved liver function and histological picture with a reduction in AFP level. Additionally, OA applies its antitumor effects by inhibition of proinflammatory transcription factor NF-κB and inflammatory markers (TNF-α and Cox-2) associated with DMBA administration. The present study shows that OA treatment efficiently suppressed the DMBA-initiated liver carcinogenesis through induction of mitochondrial-mediated apoptosis and autophagy and modulating inflammation.

Non-invasive Bioluminescence Monitoring of Hepatocellular Carcinoma Therapy in an HCR Mouse Model

Animal models play crucial roles in the development of anticancer therapeutics. The ability to quickly assess the localized primary hepatocellular carcinoma (HCC) status in a non-invasive manner would significantly improve the effectiveness of anti-HCC therapeutic studies. However, to date, animal models with this advantage are extremely scarce. In this study, we developed a novel animal model for the fast assessment of drug efficacy against primary HCC in vivo. HCC was induced in immunocompetent hepatocarcinogenesis reporter (HCR) mice by diethylnitrosamine (DEN) injection and confirmed by histopathological staining. Using the bioluminescence imaging (BLI) technique, HCC progression was longitudinally visualized and monitored in a non-invasive way. Tests of two clinical drugs showed that both sorafenib and oxaliplatin significantly inhibited the BLI signal in mouse liver in a dose-dependent manner. The in vivo intensity of BLI signals was highly consistent with the final tumor burden status in mouse liver after drug treatment. The inhibitory effect of anti-HCC drugs was accurately evaluated through in vivo BLI intensity detection. Our study successfully established a bioluminescence mouse model for non-invasive real-time monitoring of HCC therapy, and this HCR mouse model would be a useful tool for potential anti-HCC drug screening and new therapeutic strategy development.

Transgenic Animal Models to Visualize Cancer-Related Cellular Processes by Bioluminescence Imaging

Preclinical animal models are valuable tools to improve treatments of malignant diseases, being an intermediate step of experimentation between cell culture and human clinical trials. Among different animal models frequently used in cancer research are mouse and, more recently, zebrafish models. Indeed, most of the cellular pathways are highly conserved between human, mouse and zebrafish, thus rendering these models very attractive. Recently, several transgenic reporter mice and zebrafishes have been generated in which the luciferase reporter gene are placed under the control of a promoter whose activity is strictly related to specific cancer cellular processes. Other mouse models have been generated by the cDNA luciferase knockin in the locus of a gene whose expression/activity has increased in cancer. Using BioLuminescence Imaging (BLI), we have now the opportunity to spatiotemporal visualize cell behaviors, among which proliferation, apoptosis, migration and immune responses, in any body district in living animal in a time frame process. We provide here a review of the available models to visualized cancer and cancer-associated events in living animals by BLI and as they have been successful in identifying new stages of early tumor progression, new interactions between different tissues and new therapeutic responsiveness.

Mice lacking RAP1 show early onset and higher rates of DEN-induced hepatocellular carcinomas in female mice

RAP1, a component of the telomere-protective shelterin complex, has been shown to have both telomeric and non-telomeric roles. In the liver, RAP1 is involved in the regulation of metabolic transcriptional programs. RAP1-deficient mice develop obesity and hepatic steatosis, these phenotypes being more severe in females than in males. As hepatic steatosis and obesity have been related to increased liver cancer in mice and humans, we set out to address whether RAP1 deficiency resulted in increased liver cancer upon chemical liver carcinogenesis. We found that Rap1-/- females were more susceptible to DEN-induced liver damage and hepatocellular carcinoma (HCC). DEN-treated Rap1-/- female livers showed an earlier onset of both premalignant and malignant liver lesions, which were characterized by increased abundance of γH2AX-positive cells, increased proliferation and shorter telomeres. These findings highlight an important role for RAP1 in protection from liver damage and liver cancer.

A new bioluminescent imaging technology for studying oxidative stress in the testis and its impacts on fertility

PURPOSE

Excessive oxidative stress (OS) leads to cellular dysfunctions and cell death and constitutes a major cause of male infertility. However, the etiologies of increased reactive oxygen species (ROS) in male infertility is not fully understood. One major limitation is the lack of an in vivo imaging system that can be used to effectively study the impact of excessive ROS in the testis. Recently, we discovered that the hepatocellular carcinoma reporter (HCR) mice previously generated in our laboratory also expressed luciferase in the spermatids of the testis. The goal of the current study is to use the HCR mice to detect OS in the testis and to investigate the potential use of this new system in studying OS-induced male infertility.

EXPERIMENTAL DESIGN

Bioluminescence imaging (BLI) was performed in HCR mice that were treated with peroxy caged luciferin-1 (PCL-1), an OS reporter, to establish a new mouse model for in vivo monitoring of the OS status inside the male reproductive tract. Subsequently, the effect of acetaminophen (APAP) overdose on the OS inside the testis and male fertility were determined. Lastly, APAP was co-administered with glutathione, an antioxidant reagent, to test if the HCR mice can serve as a model for the effective and rapid assessment of the potency of individual agents in modifying the OS inside the mouse testis.

RESULTS

The OS level in the testis in the HCR mice was readily detected by BLI. The use of this new model led to the discovery that APAP caused a sudden rise of OS in the testis and was a potent toxicant for the male reproductive system. Moreover, administration of glutathione was effective in preventing the APAP-induced elevation of OS and in ameliorating all of the OS-induced anomalies in the testis.

CONCLUSIONS

The HCR mice represent an excellent model for monitoring OS change in the mouse testis by real time BLI. APAP is a potent male reproductive toxicant and APAP-treated mice represent a valid model for OS-induced male infertility. This model can be used to study OS-induced damage in male reproductive tract and in assessing the effects of therapeutic agents on the relative levels of OS and male fertility.

Alpha-fetoprotein-targeted reporter gene expression imaging in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers in Eastern Asia, and its incidence is increasing globally. Numerous experimental models have been developed to better our understanding of the pathogenic mechanism of HCC and to evaluate novel therapeutic approaches. Molecular imaging is a convenient and up-to-date biomedical tool that enables the visualization, characterization and quantification of biologic processes in a living subject. Molecular imaging based on reporter gene expression, in particular, can elucidate tumor-specific events or processes by acquiring images of a reporter gene’s expression driven by tumor-specific enhancers/promoters. In this review, we discuss the advantages and disadvantages of various experimental HCC mouse models and we present in vivo images of tumor-specific reporter gene expression driven by an alpha-fetoprotein (AFP) enhancer/promoter system in a mouse model of HCC. The current mouse models of HCC development are established by xenograft, carcinogen induction and genetic engineering, representing the spectrum of tumor-inducing factors and tumor locations. The imaging analysis approach of reporter genes driven by AFP enhancer/promoter is presented for these different HCC mouse models. Such molecular imaging can provide longitudinal information about carcinogenesis and tumor progression. We expect that clinical application of AFP-targeted reporter gene expression imaging systems will be useful for the detection of AFP-expressing HCC tumors and screening of increased/decreased AFP levels due to disease or drug treatment.

PET imaging of oncolytic VSV expressing the mutant HSV-1 thymidine kinase transgene in a preclinical HCC rat model

Hepatocellular carcinoma (HCC) is the most predominant form of liver cancer and the third leading cause of cancer-related death worldwide. Due to the relative ineffectiveness of conventional HCC therapies, oncolytic viruses have emerged as novel alternative treatment agents. Our previous studies have demonstrated significant prolongation of survival in advanced HCC in rats after oncolytic vesicular stomatitis virus (VSV) treatment. In this study, we aimed to establish a reporter system to reliably and sensitively image VSV in a clinically relevant model of HCC for clinical translation. To this end, an orthotopic, unifocal HCC model in immune-competent Buffalo rats was employed to test a recombinant VSV vector encoding for an enhanced version of the herpes simplex virus 1 (HSV-1) thymidine kinase (sr39tk) reporter, which would allow the indirect detection of VSV via positron emission tomography (PET). The resulting data revealed specific tracer uptake in VSV-HSV1-sr39tk-treated tumors. Further characterization of the VSV-HSV1-sr39tk vector demonstrated its optimal detection time-point after application and its detection limit via PET. In conclusion, oncolytic VSV expressing the HSV1-sr39tk reporter gene allows for highly sensitive in vivo imaging via PET. Therefore, this imaging system may be directly translatable and beneficial in further clinical applications.

Alpha-fetoprotein-a potential biomarker of intestinal regeneration in the infant

We hypothesise that the human infant, whether born prematurely or at term, may have special capacities when mounting a healing response to severe post-natal gastrointestinal injury consequent upon stem cells of endodermal origin, located in the infant gut, persisting beyond the intrauterine period. Should such endodermal stem cells persist beyond birth, and should they survive any gastro-intestinal injury, there would be a possibility for them to be re-activated, and then to differentiate into progeny cells appropriate to replacement of the destroyed intestinal cell type(s). We therefore postulate that in infants who survive significant intestinal necrosis requiring surgical excision in the perinatal period, a component of the recovery process may include some degree of intestinal regeneration. Evidence for the regeneration of intestine would be evinced by measurement of a biomarker in the plasma of recovering infants--alpha-fetoprotein (AFP)--as this protein would be produced by early generations of these putative replacement progeny intestinal cells. We would anticipate an initial significant rise in the plasma AFP, prior to a plateau in levels, and then a subsequent fall in plasma AFP values. This would indicate the activity, then subsequent cessation, of any intestinal cell regenerative process. We have recently published a previously undescribed pattern of anomalous serial plasma concentrations of AFP in several infants who survived following significant intestinal necrosis and subsequent surgical resection. We consider this novel hypothesis, and our associated observation of another cause of rising AFP in the post-natal period, to support our contention regarding the presence and potential of intestinal stem cells, and a regenerative process within the infant gastro-intestinal system. This hypothesis has important implications for the understanding of the physiologic responses following gut cell necrosis in the human newborn as well as future approaches to research directions, clinical support and potential treatment modalities, during their recovery phase. Further studies are needed to confirm our hypothesis.

Illuminating cancer systems with genetically engineered mouse models and coupled luciferase reporters in vivo

Bioluminescent imaging (BLI) is a powerful noninvasive tool that has dramatically accelerated the in vivo interrogation of cancer systems and longitudinal analysis of mouse models of cancer over the past decade. Various luciferase enzymes have been genetically engineered into mouse models (GEMM) of cancer, which permit investigation of cellular and molecular events associated with oncogenic transcription, posttranslational processing, protein-protein interactions, transformation, and oncogene addiction in live cells and animals. Luciferase-coupled GEMMs ultimately serve as a noninvasive, repetitive, longitudinal, and physiologic means by which cancer systems and therapeutic responses can be investigated accurately within the autochthonous context of a living animal.

Comparative histomorphological review of rat and human hepatocellular proliferative lesions

In this comparative review, histomorphological features of common nonneoplastic and neoplastic hepatocyte lesions of rats and humans are examined using H&E-stained slides. The morphological similarities and differences of both neoplastic (hepatocellular carcinoma and hepatocellular adenoma) and presumptive preneoplastic lesions (large and small cell change in humans and foci of cellular alteration in rats) are presented and discussed. There are major similarities in the diagnostic features, growth patterns and behavior of both rat and human hepatocellular proliferative lesions and in the process of hepatocarcinogenesis. Further study of presumptive preneoplastic lesions in humans and rats should help to further define their role in progression to hepatocellular neoplasia in both species.

Overexpression of a novel osteopetrosis-related gene CCDC154 suppresses cell proliferation by inducing G2/M arrest

Osteopetrosis, a disorder of skeletal bone, can cause death during childhood. We previously described a new spontaneous autosomal recessive osteopetrosis mouse mutant, "new toothless" (ntl). In this study, we reported for the first time the identification, cloning and characterization of the coiled-coil domain-containing 154 (CCDC154), a novel gene whose deletion of ~5 kb sequence including exons 1-6 was completely linked to the ntl mutant. The CCDC154 was conserved between mouse and human and is wildly expressed in mouse tissues. The cellular localization of CCDC154 was in the early endosomes. Overexpression of CCDC154 inhibited cell proliferation of HEK293 cells by inducing G 2/M arrest. CCDC154 also inhibited tumor cell growth, and the soft agar assay revealed a significant decrease of the colony size of Hela cells upon transfection of CCDC154. Our results indicate that CCDC154 is a novel osteopetrosis-related gene involved in cell cycle regulation and tumor suppression growth.

Radio-deoxynucleoside Analogs used for Imaging tk Expression in a Transgenic Mouse Model of Induced Hepatocellular Carcinoma

Purpose: A group of radiolabeled thymidine analogs were developed as radio-tracers for imaging herpes viral thymidine kinase (HSV1-tk) or its variants used as reporter gene. A transgenic mouse model was created to express tk upon liver injury or naturally occurring hepatocellular carcinoma (HCC). The purpose of this study was to use this unique animal model for initial testing with radio-labeled thymidine analogs, mainly a pair of newly emerging nucleoside analogs, D-FMAU and L-FMAU.

Methods: A transgeneic mouse model was created by putting a fused reporter gene system, firefly luciferase (luc) and HSV1-tk, under the control of mouse alpha fetoprotein (Afp) promoter. Initial multimodal imaging, which was consisted of bioluminescent imaging (BLI) and planar gamma scintigraphy with [¹²⁵I]-FIAU, was used for examining the model creation in the new born and liver injury in the adult mice. Carcinogen diethylnitrosamine (DEN) was then administrated to induce HCC in these knock-in mice such that microPET imaging could be used to track the activity of Afp promoter during tumor development and progression by imaging tk expression first with [¹⁸F]-FHBG. Dynamic PET scans with D-[¹⁸F]-FMAU and L-[¹⁸F]-FMAU were then performed to evaluate this pair of relatively new tracers. Cells were derived from these liver tumors for uptake assays using H-3 labeled version of PET tracers.

Results: The mouse model with dual reporters: HSV1-tk and luc placed under the transcriptional control of an endogenous Afp promoter was used for imaging studies. The expression of the Afp gene was highly specific in proliferative hepatocytes, in regenerative liver, and in developing fetal liver, and thus provided an excellent indicator for liver injury and cancer development in adult mice. Both D-FMAU and L-FMAU showed stable liver tumor uptake where the tk gene was expressed under the Afp promoter. The performance of this pair of tracers was slightly different in terms of signal-to-background ratio as well as tracer clearance.

Conclusion: The newly created knock-in mouse model was used to demonstrate the use of the dual-reporter genes driven by well-characterized cancer-specific transcriptional units in conjunction with in vivo imaging as a paradigm in studying naturally occurring cancer in live animals. While BLI is suitable for small animal imaging with luc expression, PET with L-FMAU seemed be the choice for liver injury or liver cancer imaging with this animal model for future investigations.

Circulating tumor cells measurements in hepatocellular carcinoma

Liver cancer is the fifth most common cancer in men and the seventh in women. During the past 20 years, the incidence of HCC has tripled while the 5-year survival rate has remained below 12%. The presence of circulating tumor cells (CTC) reflects the aggressiveness nature of a tumor. Many attempts have been made to develop assays that reliably detect and enumerate the CTC during the development of the HCC. In this case, the challenges are (1) there are few markers specific to the HCC (tumor cells versus nontumor cells) and (2) they can be used to quantify the number of CTC in the bloodstream. Another technical challenge consists of finding few CTC mixed with million leukocytes and billion erythrocytes. CTC detection and identification can be used to estimate prognosis and may serve as an early marker to assess antitumor activity of treatment. CTC can also be used to predict progression-free survival and overall survival. CTC are an interesting source of biological information in order to understand dissemination, drug resistance, and treatment-induced cell death. Our aim is to review and analyze the different new methods existing to detect, enumerate, and characterize the CTC in the peripheral circulation of patients with HCC.