Prototype of the preclinical MPI scanner. Courtesy: Philips Research Hamburg

Characterizing Drug Efficacy with Desktop MRI

“Characterization of Different Drug Treatments Efficacy in Morris Hepatocellular Carcinoma (HCC) Bearing Rat with Desktop MRI”

Fifteen Morris hepatoma-bearing rats were treated using two differing regimes, and the therapeutic results for both were monitored using the Icon desktop MRI scanner.

A group of 6 animals was treated with Sorafenib, a multikinase inhibitor blocking tumor cell proliferation and angiogenesis whereas a second group of rats (n=6) was administered with Entinostat –MS-275- a benzoamide with activity against HDAC of class 1 and 2. The choice of these two compounds was supported by evidence in literature reporting a significant reduction in tumor mass after 3/4 weeks of treatment.

The efficacy of the different drugs’ administration was monitored over an approximate 4-week timeframe by running T2 -weighted anatomical MRI acquisitions. The results were then compared with those obtained in a control group (n=3) that received only the drug vehicle.

Materials and Methods
Tumor Induction

One million McA-RH7777 cells were collected and washed twice with PBS. Cells were then re-suspended in 0.2 mL of DMEM medium and injected with a 27G needle under the hepatic capsula of the left lobe of the liver of anesthetized Buffalo rats.

Drug Administration and Animal Treatment
Sorafenib was dissolved in Cremophor EL and 95% ethanol (50:50) and administered at a dose of 30mg/kg in 500 μL vehicle once daily. Treatment started 1 week after cell inoculation and continued up to 24 days.

Figure 1

Figure 1: Mean tumor volume (mm3) in orthotopic Morris hepatocellular bearing rats treated with Sorafenib –red circles-, MS-275 –green circles- and controls –black circles-. Bars indicate standard deviation.

MS-275 was suspended in methanol. This stock solution was diluted at least 20-fold with water for injection, to a final maximum concentration of 0.5% methanol before injection. Administration was performed at a dose of 3mg/kg i.p. per day. Treatment started 1 week after cell inoculation and continued up to 24 days.

Administration was performed at a dose of 3mg/kg i.p. per day. Treatment started 1 week after cell inoculation and continued up to 24 days.

MRI Experiments
For MR experiments, animals were anaesthetized with isofluorane gas (about 1%) in a mixture of 33% O2 and 66% N2O. During the experiments, anaesthesia was maintained by adjusting the gas level as a function of breathing rate.

Transverse RARE T2 -weighted images were acquired using the following parameters:

FOV=5.7X4.5cm; matrix size=156X156 (in-plane resolution of 0.365X0.288 mm2); slice thickness=2.5mm; number of slices=10; TR=1200ms; TEeff=53.3ms; RARE factor=4 and NEX=8. For coronal images the slice thickness was set to 4mm, number of slices=7 and NEX=4.

These parameters were chosen following an optimization procedure to achieve high resolution images with good contrast.

Tumor volume was measured through manual segmentation of the mass, using default ParaVision ROI selection tools.

After the end the experiment, the animals were given an overdose of gas anaesthesia and the livers were excised for macroscopic evaluation.

Figure 2

Figure 2: Coronal and transverse T2 -weighted MR images at 0 -3 days and 18-24 days intervals in: (A) untreated HCC rats; (B) MS-275 treated animals and (C) Sorafenib group. Red arrows indicate tumor masses. (Click to enlarge)

Both Sorafenib and MS-275 were effective in reducing tumor growth compared to animals treated with just the vehicle (see figures 1 and 2).

A significant reduction in the tumor growth rate was observed in treated animals after the end of the 1st week of administration. This effect steadily increased over time, reaching its maximum at the end of the study.

According  to  our  results,  Sorafenib  exhibited  the  highest activity  against  hepatoma  proliferation, with an average tumor volume of 3174±142 mm3  detected after 24 days of treatment. The average values for MS-275 and the control animals were 8908±10.5mm3 and 9485±385mm3 respectively.

In addition, Sorafenib was effective in limiting lung metastases and tumor spread to kidneys, spleen and peritoneum, which affected 80-90% of the control and MS-275 animals, as confirmed by our autoptic examination.

The Bruker Icon desktop MRI scanner proved itself as a valuable pre-clinical tool for therapeutic follow-up of HCC rats undergoing 2 different drug treatments.

Operating at 1 Tesla, Icon combined the advantages of reduced running costs and high tissue contrast, returning images with good resolution that allowed full characterization of our tumor models.

According to our results, drug treatment showed indeed a beneficial effect on cancer growth compared to controls. The highest reduction in tumor mass size was registered in rats after 24 days of treatment with Sorafenib (i.e. – 66.54% in volume) compared to controls.

For more information please contact Luca Venturi:

Luca Venturi1, Luigi Miragoli2, Claudia Cabella2, Lara Caminiti2, Fabio Tedoldi2 and Silvio Aime1
1 Dipartimento di Fisica Sperimentale, Università degli Studi di Torino, Italy
2 Centro Ricerche Bracco, Bracco Imaging Spa, Colleretto Giacosa, Italy

Find out more about the Icon

Read more articles about preclinical imaging

Leave a Reply

Your email address will not be published. Required fields are marked *