Application of magnetic resonance imaging in transgenic and chemical mouse models of hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. The molecular mechanisms underlying hepatocarcinogenesis are still poorly understood. Genetically modified mice are powerful tools to further investigate the mechanisms of HCC development. However, this approach is limited due to the lack of non-invasive detection methods in small rodents. The aim of this study was to establish a protocol for the non-invasive analysis of hepatocarcinogenesis in transgenic mice using a clinical 1.5 Tesla Magnetic Resonance Imaging scanner.</p> <p>Results</p> <p>As a model system we used hepatocyte-specific c-myc transgenic mice developing hepatocellular carcinoma at the age of 12-15 months. The scans of the murine livers included axial T2-weighted turbo-spin echo (TSE) images, axial T1-weighted and contrast enhanced T1-weighted gradient echo (fast field echo, FFE) and sagittal true Fast Imaging with Steady state Precession (true-FISP) images. Application of contrast agent was performed via tail vein-catheter and confirmed by evaluation of the altered longitudinal relaxation T1 time before and after application. Through technical adaptation and optimization we could detect murine liver lesions with a minimum diameter of approximately 2 mm and provided histopathological evidence that these MR findings correspond to hepatocellular carcinoma. Tumor growth was repeatedly measured using sequential MRI with intervals of 5 weeks and subsequent volumetric analysis facilitating direct comparison of tumor progression between individual animals. We finally demonstrated that our protocol is also applicable in the widely- used chemical model of N-nitrosodiethylamine-induced hepatocarcinogenesis.</p> <p>Conclusion</p> <p>Our protocol allows the non-invasive, early detection of HCC and the subsequent continuous monitoring of liver tumorgenesis in transgenic mice thereby facilitating future investigations of transgenic tumor mouse models of the liver.</p

Inactivation of cyclin E1 inhibits chemically induced hepatocarcinogenesis in mice

E-type cyclins (CcnE) control the transition of quiescent cells into the cell cycle. Two E-type cyclins, CcnE1 and CcnE2 have been described. A variety of human cancers, including hepatocellular carcinoma (HCC), overexpress CcnE and this is frequently associated with reduced patient survival. The aim of the present study was to dissect the role of CcnE1 and CcnE2 for hepatocarcinogenesis induced by the carcinogen diethylnitrosamine (DEN) using CcnE1 and CcnE2 knockout mice. The central question was how the genetic loss of CcnE1 or CcnE2 would affect tumor initiation and/or progression. The study revealed several unexpected findings. CcnE2-/- mice developed liver tumors of similar number and size compared to wild type (WT) animals demonstrating for the first time that CcnE2 is dispensable for development of liver cancer. Surprisingly, CcnE1-deficient animals were mostly resistant to HCC induction and showed poor tumor growth. Therefore the present data suggests that CcnE1 – but not its homologue CcnE2 – is essential for initiation and progression of liver cancer. The molecular mechanisms underlying these findings were further investigated in a model of DEN-induced acute liver injury, which reflected immediate early events of cell transformation and cellular signaling. DEN-mediated liver injury was genotoxic and triggered a DNA damage response pathway (DDR) and activation of Jun kinases (JNK) already 24 and 48 hours after treatment in all genotypes. Interestingly, CcnE1-deficient livers revealed transient hyper-activation of JNK and more importantly a stronger and prolonged expression of the tumor suppressor p53. In good agreement, CcnE1-/- livers showed also prolonged cell cycle arrest associated with increased expression of cell cycle inhibitors p21 and p27 following DEN challenge. Thus expression of CcnE1 was shown to be essential to overcome the cell cycle arrest and DDR of hepatocytes immediately after mutagenic treatment. In another approach knockout mice with a hepatocyte-specific deletion of Cdk2 (Cdk2 delta hepa) and Cdk2 delta hepa CcnE2-/- double knockout mice were generated and subjected to DEN treatment. Importantly, these strains were also strongly protected from HCC formation similar to CcnE1-/- mice. In summary, the present study demonstrated for the first time that CcnE1 is an essential oncogene in the liver and drives hepatocarcinogenesis and tumor growth in a Cdk2-dependent manner

Inactivation of cyclin E1 inhibits chemically induced hepatocarcinogenesis in mice

E-type cyclins (CcnE) control the transition of quiescent cells into the cell cycle. Two E-type cyclins, CcnE1 and CcnE2 have been described. A variety of human cancers, including hepatocellular carcinoma (HCC), overexpress CcnE and this is frequently associated with reduced patient survival. The aim of the present study was to dissect the role of CcnE1 and CcnE2 for hepatocarcinogenesis induced by the carcinogen diethylnitrosamine (DEN) using CcnE1 and CcnE2 knockout mice. The central question was how the genetic loss of CcnE1 or CcnE2 would affect tumor initiation and/or progression. The study revealed several unexpected findings. CcnE2-/- mice developed liver tumors of similar number and size compared to wild type (WT) animals demonstrating for the first time that CcnE2 is dispensable for development of liver cancer. Surprisingly, CcnE1-deficient animals were mostly resistant to HCC induction and showed poor tumor growth. Therefore the present data suggests that CcnE1 – but not its homologue CcnE2 – is essential for initiation and progression of liver cancer. The molecular mechanisms underlying these findings were further investigated in a model of DEN-induced acute liver injury, which reflected immediate early events of cell transformation and cellular signaling. DEN-mediated liver injury was genotoxic and triggered a DNA damage response pathway (DDR) and activation of Jun kinases (JNK) already 24 and 48 hours after treatment in all genotypes. Interestingly, CcnE1-deficient livers revealed transient hyper-activation of JNK and more importantly a stronger and prolonged expression of the tumor suppressor p53. In good agreement, CcnE1-/- livers showed also prolonged cell cycle arrest associated with increased expression of cell cycle inhibitors p21 and p27 following DEN challenge. Thus expression of CcnE1 was shown to be essential to overcome the cell cycle arrest and DDR of hepatocytes immediately after mutagenic treatment. In another approach knockout mice with a hepatocyte-specific deletion of Cdk2 (Cdk2 delta hepa) and Cdk2 delta hepa CcnE2-/- double knockout mice were generated and subjected to DEN treatment. Importantly, these strains were also strongly protected from HCC formation similar to CcnE1-/- mice. In summary, the present study demonstrated for the first time that CcnE1 is an essential oncogene in the liver and drives hepatocarcinogenesis and tumor growth in a Cdk2-dependent manner

Metalloproteinases in melanoma

Tumour cell adhesion, motility, proteolytic activities and cell receptors have important roles in cancer invasion. These processes are involved from early development of melanoma within the epidermis, to tumour cell invasion of the underlying tissue until intravasation of lymphatic or blood vessels, and thereafter, dissemination into distant organs occur. The activity of several proteolytic enzymes was shown to be pivotal in promoting melanoma cell invasion. These enzymes not only remodel the extracellular matrix, but also release active factors and shed cell surface receptors thereby mediating melanoma cross-communication with their microenvironment. This leads to the generation of a favourable environment for melanoma growth. Several proteases are involved in melanoma invasion and include serine, cysteine proteases, matrix metalloproteases (MMPs) and the disintegrin and metalloproteases (ADAMs). This study summarises the current knowledge on the role of metalloproteinases, MMPs and ADAMs, in melanoma. (C) 2014 Elsevier GmbH. All rights reserved