Characterization of malignant colon tumors with 31P nuclear magnetic resonance phospholipid and phosphatic metabolite profiles

Biomembrane lipids: When physics and chemistry join to shape biological activity

Biomembranes constitute the first lines of defense of cells. While small molecules can often permeate cell walls in bacteria and plants, they are generally unable to penetrate the barrier constituted by the double layer of phospholipids, unless specific receptors or channels are present. Antimicrobial or cell-penetrating peptides are in fact highly specialized molecules able to bypass this barrier and even discriminate among different cell types. This capacity is made possible by the intrinsic properties of its phospholipids, their distribution between the internal and external leaflet, and their ability to mutually interact, modulating the membrane fluidity and the exposition of key headgroups. Although common phospholipids can be found in the membranes of most organisms, some are characteristic of specific cell types. Here, we review the properties of the most common lipids and describe how they interact with each other in biomembrane. We then discuss how their assembly in bilayers determines some key physical-chemical properties such as permeability, potential and phase status. Finally, we describe how the exposition of specific phospholipids determines the recognition of cell types by membrane-targeting molecules.

In silico and in vitro design of cordycepin encapsulation in liposomes for colon cancer treatment

Cordycepin or 3'-deoxyadenosine is an interesting anti-cancer drug candidate that is found in abundance in the fungus Cordyceps militaris. It inhibits cellular growth of many cancers including lung carcinoma, melanoma, bladder cancer, and colon cancer by inducing apoptosis, anti-proliferation, anti-metastasis and by arresting the cell cycle. Cordycepin has, however, poor stability and low solubility in water, resulting in loss of its bioactivity. Liposomes can be used to overcome these obstacles. Our aim is to improve cordycepin's anti-colon cancer activity by liposome encapsulation. Cordycepin-encapsulated liposomes were designed and fabricated based on a combination of theoretical and experimental studies. Molecular dynamics (MD) simulations and free energy calculations suggest that phosphatidylcholine (PC) lipid environment is favorable for cordycepin adsorption. Cordycepin passively permeates into PC lipid bilayers without membrane damage and strongly binds to the lipids' polar groups by flipping its deoxyribose sugar toward the bilayer center. Our fabricated liposomes containing 10 : 1 molar ratio of egg yolk PC : cholesterol showed encapsulation efficiency (%EE) of 99% using microfluidic hydrodynamic focusing (MHF) methods. In our in vitro study using the HT-29 colon cancer cell line, cordycepin was able to inhibit growth by induction of apoptosis. Cell viability was significantly decreased below 50% at 125 μg mL-1 dosage after 48 h treatment with non-encapsulated and encapsulated cordycepin. Importantly, encapsulation provided (1) a 2-fold improvement in the inhibition of cancer cell growth at 125 μg mL-1 dosage and (2) 4-fold increase in release time. These in silico and in vitro studies indicate that cordycepin-encapsulated liposomes could be a potent drug candidate for colon cancer therapy.

A role for ceramide glycosylation in resistance to oxaliplatin in colorectal cancer

There is growing evidence to support a role for the ceramide-metabolizing enzyme, glucosylceramide synthase (GCS), in resistance to a variety of chemotherapeutic agents. Whether GCS contributes to oxaliplatin resistance in colorectal cancer (CRC) has not yet been determined. We have addressed this potentially important clinical issue by examining GCS function in two panels of oxaliplatin-resistant, isogenic CRC cell lines. Compared to parental cell lines, oxaliplatin-resistant cells have increased expression of GCS protein associated with increased levels of the pro-survival ceramide metabolite, glucosylceramide (GlcCer). Inhibition of GCS expression by RNAi-mediated gene knockdown resulted in a reduction in cellular GlcCer levels, with restored sensitivity to oxaliplatin. Furthermore, oxaliplatin-resistant CRC cells displayed lower ceramide levels both basally and after treatment with oxaliplatin, compared to parental cells. GlcCer, formed by GCS-mediated ceramide glycosylation, is the precursor to a complex array of glycosphingolipids. Differences in cellular levels and species of gangliosides, a family of glycosphingolipids, were also seen between parental and oxaliplatin-resistant CRC cells. Increased Akt activation was also observed in oxaliplatin-resistant CRC cell lines, together with increased expression of the anti-apoptotic protein survivin. Finally, this study shows that GCS protein levels are greatly increased in human CRC specimens, compared to matched, normal colonic mucosa, and that high levels of UGCG gene expression are significantly associated with decreased disease-free survival in colorectal cancer patients. These findings uncover an important cellular role for GCS in oxaliplatin chemosensitivity and may provide a novel cellular target for augmenting chemotherapeutic drug effectiveness in CRC.

Overexpression of TrpC5 promotes tumor metastasis via the HIF-1α-Twist signaling pathway in colon cancer

In cancer cells, intracellular Ca²⁺ homeostasis is altered, and this is involved in tumor initiation, progression, and metastasis. However, little is known about the underlying mechanisms. Here, we report that transient receptor potential channel 5 (TrpC5), a receptor-activated non-selective Ca²⁺ channel, is correlated with tumor metastasis in colon cancer patients. Moreover, in colon cancer cells, overexpression of TrpC5 caused a robust rise in the concentration of ([Ca²⁺]_i), decreased E-cadherin, and increased mesenchymal biomarker expression, then promoted cell migration, invasion, and proliferation. Interestingly, we found that TrpC5 mediated hypoxia-inducible factor 1α (HIF-1α) expression, activating Twist to promote the epithelial-mesenchymal transition (EMT). Notably, patients with high expression of TrpC5 displayed poorer overall and metastasis-free survival. Taken together, our findings demonstrate that TrpC5 induces the EMT through the HIF-1α-Twist signaling pathway to promote tumor metastasis in colon cancer.

Sphingolipid abnormalities in cancer multidrug resistance: Chicken or egg?

The cancer multidrug resistance (MDR) phenotype encompasses a myriad of molecular, genetic and cellular alterations resulting from progressive oncogenic transformation and selection. Drug efflux transporters, in particular the MDR P-glycoprotein ABCB1, play an important role in MDR but cannot confer the complete phenotype alone indicating parallel alterations are prerequisite. Sphingolipids are essential constituents of lipid raft domains and directly participate in functionalization of transmembrane proteins, including providing an optimal lipid microenvironment for multidrug transporters, and are also perturbed in cancer. Here we postulate that increased sphingomyelin content, developing early in some cancers, recruits and functionalizes plasma membrane ABCB1 conferring a state of partial MDR, which is completed by glycosphingolipid disturbance and the appearance of intracellular vesicular ABCB1. In this review, the independent and interdependent roles of sphingolipid alterations and ABCB1 upregulation during the transformation process and resultant conferment of partial and complete MDR phenotypes are discussed.

Highly Selective Anti-Cancer Activity of Cholesterol-Interacting Agents Methyl-β-Cyclodextrin and Ostreolysin A/Pleurotolysin B Protein Complex on Urothelial Cancer Cells

Cholesterol content can vary distinctly between normal and cancer cells, with elevated levels in cancer cells. Here, we investigated cholesterol sequestration with methyl-β-cyclodextrin (MCD), and pore-formation with the ostreolysin A/pleurotolysin B (OlyA/PlyB) protein complex that binds to cholesterol/sphingomyelin-rich membrane domains. We evaluated the effects on viability of T24 invasive and RT4 noninvasive human urothelial cancer cells and normal porcine urothelial (NPU) cells. Cholesterol content strongly correlated with cancerous transformation, as highest in the T24 high-grade invasive urothelial cancer cells, and lowest in NPU cells. MCD treatment induced prominent cell death of T24 cells, whereas OlyA/PlyB treatment resulted in greatly decreased viability of the RT4 low-grade noninvasive carcinoma cells. Biochemical and transmission electron microscopy analyses revealed that MCD and OlyA/PlyB induce necrotic cell death in these cancer cells, while viability of NPU cells was not significantly affected by either treatment. We conclude that MCD is more toxic for T24 high-grade invasive urothelial cancer cells, and OlyA/PlyB for RT4 low-grade noninvasive urothelial cancer cells, and neither is toxic for NPU cells. The cholesterol and cholesterol/sphingomyelin-rich membrane domains in urothelial cancer cells thus constitute a selective therapeutic target for elimination of urothelial cancer cells.

Clinical significance of detecting lymphatic and blood vessel invasion in stage II colon cancer using markers D2-40 and CD34 in combination

This research was conducted to compare differences in colon cancer lymphatic vessel invasion (LVI) with D2-40 antibody labeling and regular HE staining, blood vessel invasion (BVI) with CD34 antibody labeling and HE staining and to assess the possibility of using D2-40-LVI/CD34-BVI in combination for predicting stage II colon cancer prognosis and guiding adjuvant chemotherapy.Anti-D2-40 and anti-CD34 antibodies were applied to tissue samples of 220 cases of stage II colon cancer to label lymphatic vessels and small blood vessels, respectively. LVI and BVI were assessed and multivariate COX regression analysis was performed for associations with colon cancer prognosis. Regular HE staining proved unable to differentiate lymphatic vessels from blood vessels, while D2-40 selectively labeled lymphatic endothelial cell cytosol and CD34 was widely expressed in large and small blood vessels of tumors as well as normal tissues. Compared to regular HE staining, D2-40-labeling for LVI and CD34-labeling for BVI significantly increased positive rate (22.3% vs 10.0% for LVI, and 19.1% vs 9.1% for BVI). Multivariate analysis indicated that TNM stage, pathology tissue type, post-surgery adjuvant chemotherapy, D2-40-LVI, and CD34-BVI were independent factors affecting whole group colon cancer prognosis, while HE staining-BVI, HE staining-LVI were not significantly related. When CD34-BVI/D2-40-LVI were used in combination for detection, the risk of death for patients with two or one positive results was 5.003 times that in the LVI(-)andBVI(-) group (95% CI 2.365 - 9.679). D2-40 antibody LVI labeling and CD34 antibody BVI labeling have higher specificity and accuracy than regular HE staining and can be used as molecular biological indicators for prognosis prediction and guidance of adjuvant chemotherapy for stage II colon cancer.

Miscibility and interactions of animal and plant sterols with choline plasmalogen in binary and multicomponent model systems

In this work miscibility and interactions of sterols with choline plasmalogen (PC-plasm) in Langmuir monolayers were studied. Moreover, the properties of cholesterol/phosphatidylcholine/plasmalogen mixtures of different PC-plasm concentration were investigated. The foregoing systems were treated as a model of cancer cell membranes, which are of higher plasmalogen level than normal cells. Finally, the influence of β-sitosterol and stigmasterol (phytosterols differing in anticancer potency) on these mixtures was verified. The properties of monolayers were analyzed based on the parameters derived from the surface pressure-area isotherms and images taken with Brewster Angle Microscope. It was found that at 30% of sterol in sterol/plasmalogen monolayer the lipids are immiscible and 3D crystallites are formed within the film. Cholesterol molecules mix favorably with PC-plasm at Xchol ≥ 0.5, while the investigated phytosterols only at their prevailing proportion in binary system. The increase of choline plasmalogen in cholesterol/phosphatidylcholine monolayer causes destabilization of the system. Moreover, the incorporation of phytosterols into cholesterol/phosphatidylcholine+PC-plasm mixtures disturbed membrane morphology and this effect was stronger for β-sitosterol as compared to stigmasterol. It was concluded that the presence of vinyl ether bond at sn-1 position in PC-plasm molecule strongly affects miscibility of choline plasmalogen with sterols. The comparison of the collected data with those reported in literature allowed one to conclude that miscibility and interactions of sterols with PC-plasm are less favorable than those with phosphatidylcholine. It was also suggested that overexpression of plasmalogens in cancer cell membranes may be a factor differentiating sensitivity of cells to anticancer effect of phytosterols.

MRS-based Metabolomics in Cancer Research

Metabolomics is a relatively new technique that is gaining importance very rapidly. MRS-based metabolomics, in particular, is becoming a useful tool in the study of body fluids, tissue biopsies and whole organisms. Advances in analytical techniques and data analysis methods have opened a new opportunity for such technology to contribute in the field of diagnostics. In the MRS approach to the diagnosis of disease, it is important that the analysis utilizes all the essential information in the spectra, is robust, and is non-subjective. Although some of the data analytic methods widely used in chemical and biological sciences are sketched, a more extensive discussion is given of a 5-stage Statistical Classification Strategy. This proposes powerful feature selection methods, based on, for example, genetic algorithms and novel projection techniques. The applications of MRS-based metabolomics in breast cancer, prostate cancer, colorectal cancer, pancreatic cancer, hepatobiliary cancers, gastric cancer, and brain cancer have been reviewed. While the majority of these applications relate to body fluids and tissue biopsies, some in vivo applications have also been included. It should be emphasized that the number of subjects studied must be sufficiently large to ensure a robust diagnostic classification. Before MRS-based metabolomics can become a widely used clinical tool, however, certain challenges need to be overcome. These include manufacturing user-friendly commercial instruments with all the essential features, and educating physicians and medical technologists in the acquisition, analysis, and interpretation of metabolomics data.

The effect of β-sitosterol on the properties of cholesterol/phosphatidylcholine/ganglioside monolayers--the impact of monolayer fluidity

In this paper the influence of one of phytosterols, namely β-sitosterol on cholesterol (Chol)/phosphatidylcholine (PC)/ganglioside (GM3) monolayers was examined to find the correlation between the properties of model system and the effect of phytocompound. The studied monolayers differed in condensation and fluidity, which were modified by the structure of phosphatidylcholine. It was found that the incorporation of β-sitosterol into cholesterol/phosphatidylcholine/ganglioside films changes their morphology, condensation and interactions between the lipids. The substitution of cholesterol more strongly decreased the condensation and stability of the film containing PC molecules having monounsaturated chains than more densely packed monolayer composed of saturated phosphatidylcholine. However, thorough analysis of data obtained so far suggests that the magnitude of β-sitosterol effect is determined by the composition of the system rather than its fluidity itself. Moreover, the results collected herein correlate well with the findings that phytosterol more strongly inhibits the growth of cancer cells, which at a given proportion of cholesterol to phospholipids in membranes, have more unsaturated fatty acids within phospholipids molecules.

Combining nuclear magnetic resonance spectroscopy and mass spectrometry in biomarker discovery

Metabolic profiling of biological specimens is emerging as a promising approach for discovering specific biomarkers in the diagnosis of a number of diseases. Amongst many analytical techniques, nuclear magnetic resonance spectroscopy and mass spectrometry are the most information-rich tools that enable high-throughput and global analysis of hundreds of metabolites in a single step. Although only one of the two techniques is utilized in a majority of metabolomics applications, there is a growing interest in combining the data from the two methods to effectively unravel the mammoth complexity of biological samples. In this article, current developments in nuclear magnetic resonance, mass spectrometry and multivariate statistical analysis methods are described. While some general applications that utilize the combination of the two analytical methods are presented briefly, the emphasis is laid on the recent applications of nuclear magnetic resonance and mass spectrometry methods in the studies of hepatopancreatobiliary and gastrointestinal malignancies.

VSL#3 probiotic upregulates intestinal mucosal alkaline sphingomyelinase and reduces inflammation

BACKGROUND

Alkaline sphingomyelinase, an enzyme found exclusively in bile and the intestinal brush border, hydrolyzes sphingomyelin into ceramide, sphingosine and sphingosine-1-phosphate, thereby inducing epithelial apoptosis. Reduced levels of alkaline sphingomyelinase have been found in premalignant and malignant intestinal epithelia and in ulcerative colitis tissue. Probiotic bacteria can be a source of sphingomyelinase.

OBJECTIVE

To determine the effect of VSL#3 probiotic therapy on mucosal levels of alkaline sphingomyelinase, both in a mouse model of colitis and in patients with ulcerative colitis.

METHODS

Interleukin-10 gene-deficient (IL10KO) and wild type control mice were treated with VSL#3 (10(9) colony-forming units per day) for three weeks, after which alkaline sphingomyelinase activity was measured in ileal and colonic tissue. As well, 15 patients with ulcerative colitis were treated with VSL#3 (900 billion bacteria two times per day for five weeks). Alkaline sphingomyelinase activity was measured through biopsies and comparison of ulcerative colitis disease activity index scores obtained before and after treatment.

RESULTS

Lowered alkaline sphingomyelinase levels were seen in the colon (P=0.02) and ileum (P=0.04) of IL10KO mice, as compared with controls. Treatment of these mice with VSL#3 resulted in upregulation of mucosal alkaline sphingomyelinase activity in both the colon (P=0.04) and the ileum (P=0.01). VSL#3 treatment of human patients who had ulcerative colitis decreased mean (+/- SEM) ulcerative colitis disease activity index scores from 5.3+/-1.8946 to 0.70+/-0.34 (P=0.02) and increased mucosal alkaline sphingomyelinase activity.

CONCLUSION

Mucosal alkaline sphingomyelinase activity is reduced in the intestine of IL10KO mice with colitis and in humans with ulcerative colitis. VSL#3 probiotic therapy upregulates mucosal alkaline sphingomyelinase activity.

Purified intestinal alkaline sphingomyelinase inhibits proliferation without inducing apoptosis in HT-29 colon carcinoma cells

PURPOSE

Sphingomyelin (SM) hydrolysis by sphingomyelinase (SMase) has become an important signalling pathway, with the product ceramide implicated in regulation of cell growth, differentiation and apoptosis. Alkaline SMase is specifically located in the intestinal tract. Marked reductions of the enzyme activity have been found in sporadic colorectal carcinomas and in both adenomas and flat mucosa of patients with familial adenomatous polyposis, indicating an anti-proliferative role in colonic cell growth.

METHODS

We examined the effects of a purified alkaline SMase from rat intestine and a bacterial neutral SMase on cell growth parameters in HT-29 colonic carcinoma cells.

RESULTS

Alkaline SMase was found to inhibit proliferation of HT-29 cells in both dose-dependent and time-dependent manners. The threshold concentration of the enzyme was approximately 2.5 microU/ml, and the maximum effect was obtained at approximately 20 microU/ml, which inhibited the cell growth by 50%. The inhibition occurred rapidly, and maximum effect was reached after 12 h of incubation. Dose-dependent inhibition of DNA synthesis was also demonstrated. The effect of alkaline SMase was preceded and accompanied by increased hydrolysis of SM and production of ceramide. Neutral SMase with equivalent hydrolytic capacity did not inhibit cell growth. Alkaline SMase did not induce apoptosis in HT-29 cells. Alkaline SMase did not inhibit growth of IEC-6 cells.

CONCLUSION

Alkaline SMase, at doses that induce SM hydrolysis, inhibits growth of colon cancer cells. The inhibition is attributed to an anti-proliferative effect rather than an apoptotic effect.

From T-antigen to plasmalogen-derived aldehydes: The identification of a marker of colorectal cancer in human rectal mucous

Recently, a simple noninvasive screening test for colorectal cancer was proposed, based on a hypothesis involving galactose-containing carbohydrate moieties such as the Thomsen–Friedenreich antigen. According to the hypothesis, such carbohydrate moieties, present in the human rectal mucous of patients with colorectal cancer, can be specifically oxidized with galactose oxidase to form substances that, upon reaction with Schiff reagent, yield purple (magenta) coloured compounds. While evaluating this proposed test, we discovered that the colour formation is not due to the proposed reaction between oxidized galactose moieties present in rectal mucous and Schiff reagent. We found instead that the mucous from colorectal cancer patients contains compounds that form purple (magenta) adducts with the Schiff reagent directly, i.e., they do not require oxidation by galactose oxidase. We have identified these compounds as long-chain aliphatic aldehydes, mainly palmitic aldehyde C15H31CH=O and stearic aldehyde C17H35CH=O. We have further found that the aldehydes originate from plasmalogens present in the phospholipid fraction of the mucous obtained from colorectal cancer patients. The aldehydes, present in plasmalogens as enol ethers, are released by the acidity of the Schiff reagent and in turn react with the Schiff reagent to form the coloured adducts. Correct identification of these markers could lead to the development of a more accurate colorectal cancer screening tool and to a deeper understanding of colorectal carcinogenesis.Key words: T-antigen, plasmalogen-derived aldehydes, colorectal cancer marker.

Phosphorous metabolites and steady-state energetics of transformed fibroblasts during three-dimensional growth

Rat1-T1 and MR1 spheroids represent separate transformed phenotypes originated from the same rat fibroblasts that differ in three-dimensional (3D) growth kinetics, histological structure, and oxygenation status. In the present study, (31)P-NMR spectroscopy of perfused spheroid suspensions was used to investigate cellular energetics relative to 3D growth, development of necrosis, and cell cycle distribution. Both spheroid types were characterized by a remarkably low amount of free (inorganic) phosphate (P(i)) and a low phosphocreatine peak. The ratio of nucleoside triphosphate (NTP) to P(i) ranged between 1.5 and 2.0. Intracellular pH, NTP-to-P(i) ratio, and NTP/cell remained constant throughout spheroid growth, being unaffected by the emergence of oxygen deficiency, cell quiescence, and necrosis. However, a 50% decrease in the ratio of the lipid precursors phosphorylcholine and phosphorylethanolamine (PC/PE) was observed with increasing spheroid size and was correlated with an increased G(1)/G(0) phase cell fraction. In addition, the ratio of the phospholipid degradation products glycerophosphorylcholine and glycerophosphorylethanolamine (GPC/GPE) increased with spheroid diameter in Rat1-T1 aggregates. We conclude that changes in phospholipid metabolism, rather than alterations in energy-rich phosphates, reflect cell quiescence in spheroid cultures, because cells in the inner oxygen-deficient zones seem to adapt their energy metabolism to the environmental conditions before necrotic cell destruction.

Anandamide and other N-acylethanolamines in human tumors

Long-chain N-acylethanolamines (NAE), including the endocannabinoid, anandamide, accumulate in mammalian tissues under a variety of pathological conditions. They have also been shown to inhibit the growth of various cancer cell lines in vitro. Here, we report the presence, in widely differing amounts (3.88-254.46 pmol/micromol lipid P), of NAE and their precursor phospholipids in various human tumors and some adjacent unaffected tissues. Anandamide ranged from 1.5 to 48% of total NAE, and incubation of tissue homogenates suggested possible NAE biosynthesis by both the established transacylation-phosphodiesterase pathway via N-acyl PE and by direct N-acylation of ethanolamine.

31P NMR spectroscopy of blood plasma: determination and quantification of phospholipid classes in patients with renal cell carcinoma

Advanced renal cell carcinoma (RCC) has a poor prognosis and is characterized by an unpredictable clinical course. The aim of this study was to assess the systemic phospholipid distribution as a possible marker of tumor stage and tumor spread beyond the kidney. To this end, the effect of renal cell carcinoma (RCC) on phospholipid concentrations in blood plasma using 31P NMR spectroscopy was studied in: (a) 29 patients with RCC prior to nephrectomy; (b) 19 healthy volunteers; (c) three patients with other renal tumors (renal metastases of bronchial carcinoma and of renal pelvic carcinoma, and a benign renal tumor). Furthermore, the phospholipid concentrations of eight patients of group (a) were determined 6 months after nephrectomy, when they were in remission. We found considerable deviations in the concentrations of the lysophosphatidylcholines (LPC1, LPC2) in both male and female patients with RCC compared to healthy volunteers (male--LPC1 0.217+/-0.062 vs 0.297+/-0.049 mmol/l, LPC2 0.036+/-0.014 vs 0.068+/-0.024 mmol/l; female--LPC1 0.195+/-0.071 vs 0.296+/-0.044 mmol/l, LPC2 0.037+/-0.027 vs 0.044+/-0.014 mmol/l). In addition, female patients with RCC showed lower concentrations of phosphatidylcholines (PC; 1.409+/-0.268 vs 1.947+/-0.259 mmol/l). The low phospholipid concentrations normalized for patients in remission. Phospholipid concentrations were found to depend on tumor stage and metastatic spread. The deviations in phospholipid concentrations (LPC1, LPC2, PC) observed may be attributable to systemic effects caused by the tumor as well as changes in enzyme activities.

Novel approaches to imaging brain tumors

Brain imaging techniques are assuming a greater range of roles in neuro-oncology. New techniques promise earlier recognition of the spread of tumors to the brain, which is useful in staging of disseminated disease, as well as better definition of small lesions associated with presentations of epilepsy. There is the promise that entirely noninvasive, specific diagnosis of brain tumors may become possible. Imaging methods are being used increasingly to direct and monitor therapy. Preoperative and intraoperative imaging are being used for guiding tumor surgery. An exciting potential goal for greater use of imaging is in the individualization of medical therapies either by analysis of in vitro responses or by visualization of drug responses on the tumor in situ. An important focus for technical development is in the robust integration of complementary information to allow optimization of the sensitivity and specificity of multimodal examinations.

Influence of preculture on the prefreeze and postthaw characteristics of hepatocytes

Recent studies performed in our laboratory have shown that a brief period of preculture prior to cryopreservation improves the postthaw viability of hepatocytes. The purpose of this investigation is to characterize specific metabolic and biochemical characteristics of the hepatocytes (both frozen and nonfrozen) to help elucidate the role of preculture on the postthaw viability. Fresh and thawed hepatocytes were cultured in a bioartificial liver (BAL) to determine albumin secretion as a function of time in culture. In addition, cell extracts were analyzed using nuclear magnetic resonance (NMR) spectroscopy to quantify changes in cell membrane composition and energetics as a function of time in culture prefreeze and postthaw. The results of these studies showed an increase in albumin concentration in the culture medium with time in culture for the period tested for both fresh and frozen and thawed hepatocytes. NMR spectroscopy of lipid extracts indicates that in vitro culture of hepatocytes results in an increase in cholesterol relative to membrane phospholipid. Moreover, the NMR results also indicate phospholipid interconversion, via specific lipases in cultured hepatocytes, and these changes are consistent with water permeability measurements performed previously. Significant changes in phosphoenergetics were also observed, with the net energy charge for the cells increasing significantly with time in culture. In addition, NMR spectra show increased levels of 6-phosphogluconate, another indicator of the cellular response to the stresses of isolation and ex vivo culture. These results suggest that energetic considerations may be a significant factor in the ability of hepatocytes to survive the stresses of freezing and thawing. Significant shifts in membrane phospholipids may also influence membrane permeability and postthaw survival.

Phospholipid identification and quantification of membrane vesicle subfractions by 31P-1H two-dimensional nuclear magnetic resonance

An approach to the direct quantification of phospholipids from two-dimensional 31P-1H nuclear magnetic resonance (NMR) spectroscopy with isotropic proton mixing has been developed as a general method for phospholipid analysis of minor membrane vesicle subfractions. Membrane vesicles were subfractionated by sedimentation to density equilibrium in a sucrose gradient, and a modified Folch method was employed to extract their phospholipids. The coefficient for the NMR detection efficiency of each phospholipid and the relative mole percentage of the phospholipids present in the membrane vesicles were calculated. We demonstrate low detection limits such that relative concentrations of phospholipids in membrane subfractions may be determined even in the submicromolar range.

Familial adenomatous polyposis is associated with a marked decrease in alkaline sphingomyelinase activity: a key factor to the unrestrained cell proliferation?

The hydrolysis of sphingomyelin generates key molecules regulating cell growth and inducing apoptosis. Data from animal cancer models support an inhibitory role for this pathway in the malignant transformation of the colonic mucosa. In the intestinal tract, a sphingomyelinase with an optimum alkaline pH has been identified. We recently found that the activity of alkaline sphingomyelinase is significantly decreased in colorectal adenocarcinomas, indicating a potential anticarcinogenic role of this enzyme. To further examine whether the reduction of sphingomyelinase is present already in the premalignant state of neoplastic transformation, we measured sphingomyelinase activities in patients with familial adenomatous polyposis (FAP) and in sporadic colorectal tubulovillous adenomas. Tissue samples were taken from adenomas and surrounding macroscopically normal mucosa from 11 FAP patients operated with ileorectal anastomosis, from three FAP patients with intact colon, from 13 patients with sporadic colorectal adenomas and from 12 controls. Activities of acid, neutral and alkaline sphingomyelinase were measured together with alkaline phosphatase. In FAP adenoma tissue, alkaline sphingomyelinase activity was reduced by 90% compared to controls (P < 0.0001), acid sphingomyelinase by 66% (P < 0.01) and neutral sphingomyelinase by 54% (P < 0.05). Similar reductions were found in the surrounding mucosa. In sporadic adenoma tissue, only alkaline sphingomyelinase was reduced significantly, by 57% (P < 0.05). Alkaline phosphatase was not changed in FAP adenomas, but decreased in the sporadic adenomas. We conclude that the markedly reduced levels of alkaline sphingomyelinase activities in FAP adenomas and in the surrounding mucosa may be a pathogenic factor that can lead to unrestrained cell proliferation and neoplastic transformation.

Dietary factors in human colorectal cancer

Colorectal cancer is a significant cause of mortality in Western societies. The progression of the disease from normal colonic epithelium to the acquisition of the malignant phenotype is accompanied by numerous genetic and epigenetic alterations. Compelling experimental and epidemiological evidence indicates that diet and nutrition are key factors in the modulation of colorectal cancer. A salient case in point is the recent observation that a dietary regimen based on a Western-style diet provokes in the rodent colon the appearance of preneoplastic lesions in the absence of any genotoxic insult. This review mainly describes dietary factors that inhibit the development and progression of colorectal cancer. Much is unknown about the precise mechanisms of action of chemically disparate nutrients and how they interfere with the development and progression of this disease. Current knowledge about this important issue is summarized. We believe that continuing scrutiny and precise assessment of the benefits (and potential risks) of nutrients in the treatment and prevention of colorectal cancer will prove significant to controlling this devastating disease.

From magnetic resonance spectroscopy to classification of tumors. A review of pattern recognition methods

This article reviews the wealth of different pattern recognition methods that have been used for magnetic resonance spectroscopy (MRS) based tumor classification. The methods have in common that the entire MR spectra is used to develop linear and non-linear classifiers. The following issues are addressed: (i) pre-processing, such as normalization and digitization, (ii) extraction of relevant spectral features by multivariate methods, such as principal component analysis, linear discriminant analysis (LDA), and optimal discriminant vector, and (iii) classification by LDA, cluster analysis and artificial neural networks. Different approaches are compared and discussed in view of practical and theoretical considerations.