In vivo MRS assessment of altered fatty acyl unsaturation in liver tumor formation of a TGFα/c-myc transgenic mouse model

Abstract

Current detection methods (computed tomography, ultrasound, and MRI) for hepatocarcinogenesis in humans rely on visual confirmation of neoplastic formations. A more effective early detection method is needed. Using in vivo magnetic resonance spectroscopy (MRS), we show that alterations in the integral ratios of the bis-allyl to vinyl hydrogen protons in unsaturated lipid fatty acyl groups correlate with the development of neoplastic formations in vivo in a TGFa/c-myc mouse hepatocellular carcinoma (HCC) model. HPLC analysis of the TGFa/c-myc mice liver tissue revealed a significant increase in the amount of oleic acid, along with alterations in linoleic and g-linolenic acids, as compared with control CD1 mice. Electrospray ionization tandem mass spectrometry analysis indicated a significant increase in the abundance of specific glycerol phosphatidylcholine (GPCho) lipids containing palmitic and oleic acids between control CD1 and TGFa/c-myc mice liver tissue extracts. Western blot analysis of the mice liver tissue indicates alterations in the desaturase enzyme stearoyl CoA desaturase (SCD)1, responsible for palmitic and oleic acid formation. Microarray analysis detected alterations in several genes involved with fatty acid metabolism, particularly SCD2, in transgenic mouse liver tissue. In correlation with the HPLC, mass spectrometry, Western blot, and microarray analyses, we are able to confirm the ability of in vivo MRS to detect precancerous lesions in the mouse liver before visual neoplastic formations were detectable by MRI. Hepatocellular carcinoma (HCC) is one of the most deadly forms of cancer in the world. The World Health Organization reports that liver cancer is the third highest cause of death from cancer, with HCC being predominantly observed in Asian and African countries (1). There are many known causes of HCC, including hepatitis B and C, cirrhosis, and aflatoxin exposure. The techniques currently used for diagnosis of liver cancer rely on imaging modalities (MRI, computed tomography, and ultrasound) that, at the highest sensitivity, are able to detect evidence of neoplasia when there is a formation of at least 1 mm. Image confirmation of a neoplasm this size usually only occurs at a later stage in cancer development when therapy treatments are not as effective. Therefore, the prognosis for a patient when they have visual evidence of neoplasia is poor. Additionally, neoplasms at the lower range of imaging detection are often unverifiable without biopsy. There is a need, therefore, to develop a method that can detect neoplastic formations at an earlier stage than those now in use.The efficacy of utilizing MRI, which mainly detects only protons from water hydrogens, for hepatic tumor detection and the measurement of tumor volumetric growth has been established previously (2, 3). We have utilized MRI in this study for visual confirmation of neoplastic tissue formations in the TGFa/c-myc mouse liver tumor model. In addition to the MRI visible liver changes, there have been several metabolic ...

In vivo NMR detection of diet-induced changes in adipose tissue composition

“…For hepatocellular carcinoma, one of the most deadly forms of cancer, in vivo NMR lipid profi ling has demonstrated early diagnoses. Alterations in the unsaturation level of hepatic lipids, and therefore in lipid metabolism, can indeed be detected well before the neoplastic nodules become visible in MRI scans ( 20 ). It has also been demonstrated that this method can be a very important tool for differentiating quiescent atherosclerotic plaques from more active plaques that lead to acute ischemic syndromes.…”

Hepatic lipid composition differs between ob/ob and ob/+ control mice as determined by using in vivo localized proton magnetic resonance spectroscopy

“…In vitro and in vivo 1 H MRS were applied to assess the lipid composition in white adipose tissue, brown adipose tissue, tumor, bone marrow, and subcutaneous fat of humans [7,10,[12][13][14][15][16][17][18] and the in vivo spectroscopic results were compared with data from biopsy samples. Similar 1 H MRS has been carried out to assess triacylglycerol and fatty acids in livers in humans and rodents both in vivo and ex vivo [19][20][21][22][23][24][25][26].…”

Magnetic resonance characterisation of developing hepatocellular carcinoma in a diet induced model of liver cancer in the rat

“…The advantage of the CDAA model is that animals develop histopathological features such as diffuse steatosis through to focal nodular lesions sequentially, closely resembling the human condition [217]. In general, diffuse fatty infiltration is expected to precede HCC development and may be indicative of malignant tumour [213] but there are few reliable biomarkers accurately predicting progression of fatty liver to HCC.…”

“…A previous study by Griffitts et al [213] showed that alterations in lipid metabolism associated with hepatocarcinogenesis could be followed by chemical shift imaging (CSI) and the formation of nodules or tumors could be predicted by determining the degree of unsaturation. The present study uses the CDAA rat model to determine whether other MRI methods could be used as biomarkers of heptaocarcinogenesis.…”

“…Non-alcoholic fatty liver disease (NAFLD) is now thought to contribute to increased rates of HCC incidence [1] and is associated with insulin resistance (or diabetes) and obesity [34]. Detecting and monitoring these pathologies is challenging and whilst histology is considered the reference standard for the assessment of liver pathology, the techniques are invasive, and prone to error [213] since lesions can be small and easily missed during biopsies [42]. Target pathologies of the liver are generally heterogeneously distributed and biopsy samples may misrepresent the extent of disease [43,44] because of under or over-sampling.…”