Constituents of Carpobrotus edulis inhibit P-glycoprotein of MDR1-transfected mouse lymphoma cells

A bioassay-guided separation protocol, including the testing of the extracts, fractions and pure compounds for their ability to inhibit P-glycoprotein (the efflux pump responsible for the multidrug resistance of the used cell line) of mouse lymphoma cells containing the human efflux pump gene MDR1, led to the isolation of seven compounds from the chloroform and ethyl acetate soluble fractions of the methanolic extract of Carpobrotus edulis. The compounds were identified by 1D, 2D NMR and MS investigations as triterpens (beta-amyrin, uvaol and oleanolic acid), monogalactosyldiacylglycerol, catechin, epicatechin and procyanidin B5. Uvaol was the most effective and promising compound in the reversal of multidrug resistance in MDR mouse lymphoma cell line.

Assessment of a biliary hamartoma with contrast-enhanced sonography using two different contrast agents

A 49 year old male with carcinoma of the esophagus was staged using conventional US of the abdomen. US revealed signs of cirrhosis and a hyporeflexive focal liver lesion of about 5 mm in diameter was found. Low-MI contrast-enhanced ultrasound (CEUS) with SonoVue (Bracco, Milano, Italy) showed an enhancement pattern which was typical for benign liver lesions while high-MI CEUS with Levovist (Schering, Berlin, Germany) revealed a contrast defect in the liver late phase (4:30 min p. i.) which is typical for a malignant lesion. Due to these findings the lesion was evaluated as a potentially malignant lesion and a biopsy was performed. Histology showed a benign biliary hamartoma and incomplete cirrhosis. The findings confirmed that liver-specific contrast agents have the ability to detect very small focal liver lesions not derived from hepatic tissue but may lead to a misinterpretation as a malignant lesion. Nevertheless biliary duct adenomas are benign lesions with almost the same perfusion properties as normal liver parenchyma. Therefore, while using SonoVue, such a misinterpretation of these very common but in most cases very small and not detectable lesions seems unlikely.

Quantitative assessment of iron-oxide-enhanced magnetic resonance imaging of the liver: Vessel isointensity is a potential characteristic of liver hemangiomas on late T1-weighted images

PURPOSE

To test whether a new quantitative measure, the tumor-to-vessel ratio, obtained from late post-iron-oxide-enhanced T1-weighted images allows for differentiating hemangiomas from liver metastases or all malignant liver lesions.

MATERIAL AND METHODS

Twenty-six patients (mean 57, range 33-79 years) were prospectively studied at 1.5T magnetic resonance imaging (MRI) with a T1-weighted 2D fast low-angle shot (FLASH) sequence (repetition time/echo time/flip angle; 200 ms/4.8 ms/90 degrees ) and a T2-weighted turbo spin-echo sequence (4072 ms/99 ms/180 degrees ). Imaging was carried out before and at intervals up to 18 min after IV injection of Ferucarbotran (Resovist, Schering, Germany). In 19 patients, one representative malignant lesion was analysed. Eleven hemangiomas were evaluated in 7 patients. Two readers performed a consensus reading with a signal intensity measurement in a lesion, normal liver and hepatic veins, from which ratios were computed.

RESULTS

On T1-weighted iron-oxide-enhanced MRI of 30 lesions, tumor-to-vessel signal intensity ratios were distinct in hemangiomas (median 1.04, range 0.99-1.10) as opposed to either metastases (0.64, 0.33-0.77; P < 0.05) or all malignant lesions taken together (0.64, 0.33-0.98; P < 0.05), while the tumor-to-liver ratio was not.

CONCLUSION

The tumor-to-vessel ratio may help to differentiate between hemangiomas and metastases. A ratio greater than 0.98 allowed differentiating hemangiomas from metastases with a wide safety margin.

Detection of hepatic metastases with low MI real time contrast enhanced sonography and SonoVue

AIM

SonoVue is the first ultrasound contrast agent which allows repeated continuous examination of the liver in real time. The aim of this study was to compare low mechanical index (MI) real time contrast enhanced ultrasound of the liver, using the contrast agent SonoVue, with conventional B-mode sonography for the detection of hepatic metastases.

METHOD

40 patients with known malignancy and at least one liver lesion on conventional B-mode sonography were included. Conventional B-mode sonography was performed followed by contrast enhanced ultrasound (CEUS) of the liver in the arterial (< 30 sec), portal-venous (40-120 sec) and delayed phase (> 120 sec) after injection of SonoVue. CEUS was performed using contrast specific imaging and low MI (< 0.3). Number, location and size of metastases on baseline and CEUS were compared with CT or MRI (blinded reader).

RESULTS

37 patients had 128 metastases on CT or MRI. Baseline US showed 74 metastases confirmed by reference examination (69%), while CEUS yielded 109 metastases (sensitivity 90%) (p < 0.001). On CEUS, 35 additional metastases not seen on baseline but confirmed by reference imaging were detected in 14 patients (36%). In 8 patients, CEUS showed 13 metastases not seen on reference imaging.

CONCLUSION

Detection of hepatic metastases is substantially improved by low MI real time contrast enhanced ultrasound with SonoVue compared to conventional B-mode sonography.

Detection and characterisation of liver metastases

Modern liver imaging of cancer patients requires an imaging modality that is not only highly sensitive in detecting lesions but also provides reliable characterisation of lesions and thus allows differentiation of metastases from frequently found benign lesions. Conventional ultrasound (US) has a relatively poor sensitivity and specificity for imaging liver metastases and US used to be inferior to CT and MRI mainly due to a lack of contrast agents. This has changed with the advent of microbubble contrast agents for US. The use of recent contrast agents such as SonoVue (Bracco, Italy) combined with low mechanical index contrast-specific imaging techniques such as Contrast Pulse Sequencing provides dynamic real time imaging of focal liver lesions in the arterial, portal venous and delayed phase. This improves lesion detection and characterisation. To investigate the benefit of SonoVue for detecting liver metastases we studied 40 cancer patients with liver lesions on reference imaging (CT or MRI), 37 of them had metastases. The mean number of reference confirmed metastases per patient increased from 1.85+/-1.79 on conventional ultrasound to 2.73+/-2.50 post SonoVue (p < 0.05). CEUS showed more individual metastases than baseline in 12 (34%) patients. Using CT or MRI as the reference, the mean sensitivity to individual metastases increased from 69% on baseline US to 90% post contrast (p < 0.0005). The role of SonoVue in characterisation of focal liver lesions was evaluated in 63 patients. One lesion was studied per patient. Based on standardised dynamic enhancement criteria for each lesion type, the number of correctly diagnosed lesions improved from 41 (65%) on baseline US to 58 (92%) post contrast (p < 0.001). On CEUS all 27 metastases were correctly diagnosed, while baseline US misinterpreted 2 of these. The number of correctly diagnosed benign lesions (n = 28) increased from 12 (43%) on baseline to 25 (89%) post SonoVue. In conclusion, detection and characterisation of focal liver lesions by US are markedly improved by the use of SonoVue. Contrast agents add a new dimension to sonography allowing it to rival CT and MRI, especially for lesion characterisation.

In vitro search for synergy between flavonoids and epirubicin on multidrug-resistant cancer cells

The drug accumulation of a human multidrug resistance 1 (mdr1) gene-transfected mouse lymphoma cell line and a multidrug resistance protein (MRP)-expressing human breast cancer cell line MDA-MB-231 was compared in the presence of sixteen flavonoids and five isoflavonoids. The expression of the 170-kDa P-glycoprotein (P-gp) (MDR1) and 190-kDa multidrug resistance protein (MRP) in both cell lines was confirmed by immunocytochemistry. The rhodamine 123 accumulation of the P-glycoprotein (P-gp)-expressing cells increased up to 46.4, while 2,7'-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein acetoxymethyl ester (BCECF-AM) accumulation of the MRP-expressing cells increased up to 1.6, in fluorescence activity ratio (FAR). Major P-gp-mediated efflux pump modifiers are formononetin, amorphigenin, rotenone and chrysin, while MRP-mediated efflux pump modifiers are formononetin, afrormosin, robinin, kaempferol and epigallocatechin. In antiproliferative assay, afrormosin, amorphigenin, chrysin and rotenone exhibited the strongest antiproliferative effects in L5178 (max. ID50: 19.70) and MDA-MB-231 cell lines (max. ID50: 55.47). In a checkerboard microplate method in vitro, furthermore, the most effective multidrug resistance (MDR) resistance modifiers, amorphigenin, formononetin, rotenone and chrysin, were assayed for their antiproliferative effects in combination with epirubicin. Rotenone and afrormosin showed additive effects. Chrysin and amorphigenin on the mouse lymphoma cell line and formononetin on the MDA-MB-231 cell line synergistically enhanced the effect of epirubicin.

Liver metastases in cancer: detection with contrast-enhanced ultrasonography

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.

[Ultrasound contrast agents]

Ultrasound contrast agents consist of tiny gas bubbles encapsulated by a stabilising membrane or shell. When combined with recent contrast-specific ultrasound techniques, they provide substantial enhancement of vessels and solid organs. The clinical use and the diagnostic value of ultrasound contrast agents are in principle comparable to those of contrast agents for CT and MRI. They add an additional dimension of information to sonography, which results in considerable improvement of diagnostic accuracy in many cases. This paper reviews the physicochemical properties of various microbubble contrast agents, discusses non-linear bubble behaviour and contrast-specific imaging techniques. An overview of the most important radiological clinical applications in the liver, kidney and spleen is given.