Comparison of gadolinium-DTPA and polylysine-gadolinium-DTPA--enhanced magnetic resonance imaging of hepatocarcinoma in the rat

Stability evaluation of Gd chelates for macromolecular MRI contrast agents

OBJECTIVE

We try to establish designs for the macromolecular agents possessing high Gd³⁺-chelating stability, because free Gd³⁺ ion released from Gd chelates is known as a risk factor to cause toxic side effects and a safety concern.

MATERIALS AND METHODS

We prepared three types of Gd-based macromolecular MRI contrast agents from a synthetic polymer (poly(glutamic acid) homopolymer or poly(ethylene glycol)-b-poly(lysine) block copolymer) and a chelating moiety (DO3A or DOTA) having two strategic designs for high chelate stability. Then, we examine the in vitro Gd³⁺-chelate stability of these macromolecular MRI contrast agents.

RESULTS

The prepared macromolecular agents exhibited the same or higher Gd³⁺-chelate stability as/than did Gd-DOTA that possesses the highest Gd³⁺-chelate stability among the approved small-MW Gd-chelate MRI contrast agent.

DISCUSSION

Our macromolecular design was considered to work well for high Gd³⁺-chelate stability.

Computed tomography and magnetic resonance imaging

Imaging in Oncology is rapidly moving from the detection and size measurement of a lesion to the quantitative assessment of metabolic processes and cellular and molecular interactions. Increasing insights into cancer as a complex disease with involvement of the tumor stroma in tumor pathobiological processes have made it clear that for successful control of cancer, treatment strategies should not only be directed at the tumor cells but also targeted at the tumor microenvironment. This requires understanding of the complex molecular and cellular interactions in cancer tissue. Recent developments in imaging technology have increased the possibility to image various pathobiological processes in cancer development and response to treatment. For computed tomography (CT) and magnetic resonance imaging (MRI) various improvements in hardware, software, and imaging probes have lifted these modalities from classical anatomical imaging techniques to techniques suitable to image and quantify various physiological processes and molecular and cellular interactions. Next to a more general overview of possible imaging targets in oncology this chapter provides an overview of the various developments in CT and MRI technology and some specific applications.

Different signal intensity at Gd-EOB-DTPA compared with Gd-DTPA-enhanced MRI in hepatocellular carcinoma transgenic mouse model in delayed phase hepatobiliary imaging

PURPOSE

To evaluate hyperintense Gd-DTPA- compared with hyper- and hypointense Gd-EOB-DTPA-enhanced magnet resonance imaging (MRI) in c-myc/TGFα transgenic mice for detecting hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty HCC-bearing transgenic mice with overexpression of the protooncogene c-myc and transforming growth factor-alpha (TGF-α) were analyzed. MRI was performed using a 3-T MRI scanner and an MRI coil. The imaging protocol included Gd-DTPA- and Gd-EOB-DTPA-enhanced T1-weighted images. The statistically evaluated parameters are signal intensity (SI), signal intensity ratio (SIR), contrast-to-noise ratio (CNR), percentage enhancement (PE), and signal-to-noise ratio (SNR).

RESULTS

On Gd-DTPA-enhanced MRI compared with Gd-EOB-DTPA-enhanced MRI, the SI of liver was 265.02 to 573.02 and of HCC 350.84 to either hyperintense with 757.1 or hypointense with 372.55 enhancement. Evaluated parameters were SNR of HCC 50.1 to 56.5/111.5 and SNR of liver parenchyma 37.8 to 85.8, SIR 1.32 to 1.31/0.64, CNR 12.2 to 26.1/-30.08 and PE 42.08% to 80.5/-98.2%, (P < 0.05).

CONCLUSION

Gd-EOB-DTPA is superior to Gd-DTPA for detecting HCC in contrast agent-enhanced MRI in the c-myc/TGFα transgenic mouse model and there was no difference between the hyperintense or hypointense appearance of HCC. Either way, HCCs can easily be distinguished from liver parenchyma in mice.

Adenovirus vector-mediated gene transfer using degradable starch microspheres for hepatocellular carcinoma in rats

BACKGROUND

When gene therapy is performed for malignant tumors, gene transfer efficiency and selectivity are extremely important. The delivery of anticancer agents and embolic agents through tumor feeding artery is known as transarterial embolization. We speculated that genes might be efficiently and selectively transferred to hepatocellular carcinomas (HCCs) by degradable starch microspheres (DSM) as the embolic agent, which could be trapped within the tumor and release a gene vector. Therefore, we studied the use of DSM for adenovirus vector-mediated gene transfer to HCC in vivo.

MATERIAL AND METHODS

HCC was induced in rats with diethylnitrosamine and phenobarbital, after which either AxCALacZ and DSM or AxCALacZ alone was injected through the hepatic artery.

RESULTS

Histological examination revealed that beta-galactosidase expression was greater (P < 0.001), and more selective (P < 0.001) in tumors after injection of AxCALacZ and DSM, than after injection of the vector alone.

CONCLUSION

Injection of DSM together with an adenovirus vector through the hepatic artery can result in efficient and cancer-selective transfer of genes to HCC.

Efficient and cancer-selective gene transfer to hepatocellular carcinoma in a rat using adenovirus vector with iodized oil esters

Gene therapy for cancer requires efficient, selective gene transfer to cancer cells. In gene therapy for hepatocellular carcinoma (HCC), gene transfer is efficient for small tumors, but not for large tumors. The delivery of anticancer agents and of iodized oil esters as embolic agents through tumor-feeding arteries is known as transarterial embolization. We speculate that genes may be efficiently and selectively transferred for HCC using iodized oil esters because these esters may remain together with a genetic vector within HCC selectively. Hence, we have studied the effect of iodized oil esters on adenovirus vector-mediated gene transfer for HCC in vivo. A rat model of HCC induced with diethylnitrosamine and phenobarbital was injected with either AxCALacZ, which expresses the beta-galactosidase of Escherichia coli, or AxCALacZ and iodized oil esters into the hepatic artery. Histological comparisons revealed that the beta-galactosidase expression in the rats with HCC injected with AxCALacZ and iodized oil esters was greater (P<.0001) in small tumors (P=.0046) and large tumors (P=.0023), and more selective (P=.0229) than in only AxCALacZ-injected rats. These results suggest that iodized oil esters are injected into hepatic artery together with adenovirus vector, and that genes may be efficiently and cancer-selectively transferred to HCC.