Tumor lipids

Effect of Polar Head Group Modifications on the Tumor Retention of Phospholipid Ether Analogs: Role of the Quaternary Nitrogen

We have previously described the remarkable capacity of radioiodinated alkyl phospholipids to be sequestered and retained by a variety of tumors in vivo. We have already established the influence of certain structural parameters of iodinated alkyl phospholipids on tumor avidity, such as stereochemistry at the sn-2 carbon of alkylglycerol phosphocholines, meta-or para-position of iodine in the aromatic ring of phenylalkyl phosphocholines, and the length of the alkyl chain in alkyl phospholipids. In order to determine the additional structural requirements for tumor uptake and retention, three new radioiodinated alkylphospholipid analogs, 2-4, were synthesized as potential tumor imaging agents. Polar head groups were modified to determine structure-tumor avidity relationships. The trimethylammonio group in 1 was substituted with a hydrogen atom in 2, an ammonio group in 3 and a tertiary butyl group in 4. All analogs were separately labeled with iodine-125 or iodine-124 and administered to Walker 256 tumor-bearing rats or human PC-3 tumor-bearing SCID mice, respectively. Tumor uptake was assessed by gamma-camera scintigraphy (for [I-125]-labeled compounds) and high-resolution micro-PET scanning (for [I-124]-labeled compounds). It was found that structural modifications in the polar head group of alkyl phospholipids strongly influenced the tumor uptake and tissue distribution of these compounds in tumor-bearing animals. Phosphoethanolamine analog 3 (NM401) displayed a very slight accumulation in tumor as compared with phosphocholine analog 1 (NM346). Analogs 2 (NM400) and 4 (NM402) lacking the positively charged nitrogen atom failed to display any tumor uptake and localized primarily in the liver. This study provided important insights regarding structural requirements for tumor uptake and retention. Replacement of the quaternary nitrogen in the alkyl phospholipid head group with non-polar substituents resulted in loss of tumor avidity.

Ultrasonic Sputter Desorption Mass Spectrometry Technique for Minimally Invasive Tissue Analysis

Minimally invasive techniques for in vivo tissue analysis are desired by life science and medical research. Herein, a new ionization interface coupled with ultrasonic sputter desorption (USD) was developed for in vitro and in vivo tissue analysis. Sample molecules were effectively sputtered out when the high-frequency ultrasonic probe touched the tissue. Then, the sputtered molecules were collected and ionized by a custom-made heated quartz tube and finally analyzed by mass spectrometry (MS) online. The sample pretreatment of the USD-MS technique was quite simple and required no other steps except for wetting the tissue surface with ethanol to assist molecular extraction. Experimental results demonstrated that the proposed method was suitable for the analysis of different morphologies of tissues (such as liver, brain, kidney, and lung) and performed well in the analysis of liver tumors and paracancerous tissues. Moreover, as the proposed method caused little damage to the tissues during analysis, rats and mice with orthotopic tumors still survived after the experiments. Overall, the newly developed USD-MS technique was an effective tool for minimally invasive tissue analysis and could be used as a new candidate method for in situ and real-time analysis of biological tissues in vitro and in vivo.

The intelligent knife (iKnife) and its intraoperative diagnostic advantage for the treatment of cervical disease

Clearance of surgical margins in early cervical cancer prevents the need for adjuvant chemoradiation and associated morbidity and allows fertility preservation. Clearance of disease is also crucial in the surgical management of local recurrence of cervical tumors with exenterative surgery. In this study intelligent knife technology was able to discriminate healthy from abnormal lesions on the cervix with high accuracy, highlighting the potential to improve intraoperative management of women treated surgically for cervical cancer and, as a result, patient outcomes. While pilot experiments in vivo are encouraging, accuracy remains to be validated in larger patient cohorts. Future studies could also explore whether this technology could be used for management of cervical preinvasive disease.

Clearance of surgical margins in cervical cancer prevents the need for adjuvant chemoradiation and allows fertility preservation. In this study, we determined the capacity of the rapid evaporative ionization mass spectrometry (REIMS), also known as intelligent knife (iKnife), to discriminate between healthy, preinvasive, and invasive cervical tissue. Cervical tissue samples were collected from women with healthy, human papilloma virus (HPV) ± cervical intraepithelial neoplasia (CIN), or cervical cancer. A handheld diathermy device generated surgical aerosol, which was transferred into a mass spectrometer for subsequent chemical analysis. Combination of principal component and linear discriminant analysis and least absolute shrinkage and selection operator was employed to study the spectral differences between groups. Significance of discriminatory m/z features was tested using univariate statistics and tandem MS performed to elucidate the structure of the significant peaks allowing separation of the two classes. We analyzed 87 samples (normal = 16, HPV ± CIN = 50, cancer = 21 patients). The iKnife discriminated with 100% accuracy normal (100%) vs. HPV ± CIN (100%) vs. cancer (100%) when compared to histology as the gold standard. When comparing normal vs. cancer samples, the accuracy was 100% with a sensitivity of 100% (95% CI 83.9 to 100) and specificity 100% (79.4 to 100). Univariate analysis revealed significant MS peaks in the cancer-to-normal separation belonging to various classes of complex lipids. The iKnife discriminates healthy from premalignant and invasive cervical lesions with high accuracy and can improve oncological outcomes and fertility preservation of women treated surgically for cervical cancer. Larger in vivo research cohorts are required to validate these findings.

Tensiometric Profiles and Their Modulation by Cholesterol: Implications in Cervical Cancer

Langmuir monolayers offer a convenient model for understanding the behavior of many natural systems like biological membranes. This technique was used to characterize the role of cholesterol, lipophilic, and lipophobic components of tissues in cervical cancer by evaluating their tensiometric profiles. Monolayers were formed on the surface of deionized water by spreading tissue components corresponding to 1 mg of the tissue for studying their surface pressure-area isotherms at body temperature. The cholesterol content of cancerous human cervical tissues was higher than that of the normal human cervical tissues. The addition of 3 mug cholesterol/mg tissue to the normal organic phase changed its tensiometric profile to that of the cancerous profile. Statistically significant tensiometric parameters showed that cholesterol acts as a rigidifier in the cervical tissues and has a remarkable role in shifting the normal cervical lipophilic surface activity towards that of the cancerous lipophilic monolayer. Several mixtures of the lipophilic-lipophobic components of both cancerous as well as normal cervical tissues also were characterized to reveal the relative contribution of these phases in the cervical cancer tensiometric profiles. Though the actual ratio of aqueous and organic phases in the normal tissue was 97:3 by weight, the tissue homogenate behavior was similar to that of a 50:50 mixture by weight, indicating the nonadditivity of the lipophilic-lipophobic components. The addition of cholesterol to a 97: 3 by weight aqueous: organic mixture of normal cervical tissue also revealed the rigidifying role of cholesterol. Unlike in normal tissue homogenates, the cancerous tissue homogenate tensiometric profile had more contribution from its aqueous phase components and an additive interaction between the lipophilic and lipophobic components was observed in the tissue homogenate. Thus, distinct differences in the interactions between lipophilic and lipophobic components were observed in cancerous and normal states. The Langmuir monolayer technique was sensitive to detect such changes in the form of altered tensiometric profiles. Therapeutic strategies may be designed to modulate these tensiometric profiles to our benefit.

Vitamin E as an antioxidant in vitro and in vivo

Measurements of the absolute rate constants for the reaction with peroxyl radicals of alpha, beta, gamma and delta-tocopherol and several model compounds are described. The peroxyl radicals were obtained either by the autoxidation of styrene or by the flash photolysis of di-t-butyl ketone in an oxygen-saturated environment. The kinetic data are discussed in stereoelectronic terms. Vitamin E and total lipid-soluble, chain-breaking antioxidant concentrations in some normal and cancerous tissues have been measured. In human blood plasma and erythrocyte ghost membranes vitamin E is the major, and possibly the only, chain-breaking antioxidant. Lipid extracts of Novikoff ascites hepatoma cells contain considerably more vitamin E relative to lipid than do extracts of normal rat liver. These tumour lipids contain relatively fewer highly unsaturated fatty acids and are present at lower lipid/wet tissue ratios than the normal liver lipids. A number of unresolved problems relating to the action of vitamin E in vivo are discussed.

Interfacial properties as biophysical markers of cervical cancer

Monolayers at air-liquid interfaces offer a convenient model for understanding the behavior of many natural systems like biological membranes. Langmuir monolayers were used to characterize the interfacial properties of tissue homogenates, organic phases and aqueous phases of tissue biopsy samples from 30 patients of cervical cancer and 15 normals. Our results reveal that the tensiometric parameters can differentiate between cancer and normal tissues obtained from human cervix and were statistically significant using t-test (P<0.05). The minimum surface tension of the cancer tissue monolayer was 52.9+/-4.4 mN/m, 1.4-folds greater than the normal cervical tissue homogenate value of 38.5+/-2.6 mN/m. The normal tissue homogenate isotherm had a hysteresis area of 90.3 microJ, which was approximately 6.2 times greater than that of the cervical cancer tissue monolayer. The total lipid and phospholipid contents of the cancerous cervical tissue were roughly double that of the normal cervical tissue and the surface activity was also in line with this observation. The difference in hysteresis of the cancerous and normal tissues indicates a decreased stability of the cancerous tissue film as compared to normal. The difference in surface activity denotes alterations in the molecular packing of the tissues in the cancerous state, which may have implications in terms of drug permeability and responsiveness. Further, differences in surface activity may play a role in altered cell adhesion and metastasis. This study is the first to evaluate surface properties of cancerous tissues and can lead to the development of a biophysical marker of cervical cancer based on interfacial properties.

Difference in plasma membrane structure between two sublines of Ehrlich-Lettrè ascites tumor cells

The plasma membranes of the glycogen-free and the glycogen-containing subline of Ehrlich-Lettrè ascites cells were purified and compared with respect to their enzyme activity, chemical, lipid and protein composition, and membrane fluidity. Both membrane fractions differed in a number of parameters which are discussed as differences in the expression of malignant transformation of the two sublines. 1. The 5'-nucleotidase activity was 3-5 times higher and the sialic acid content 3-times lower in the glycogen-containing than in the glycogen-free subline. 2. Differences were also observed with respect to the phospholipid composition, that is in the relative proportions of mainly phosphatidylcholine, -inositol and -serine. 3. The fatty acid spectrum of the two sublines differed in the C-18 series and in the percentage of polyunsaturated acids, which was about 6% lower in the glycogen-containing line. 4. Measurements of fluorescence polarization (P) using 1,6-diphenyl-1,3,5-hextriene as probe generally gave higher P values, indicating a decreased membrane fluidity for the plasma membranes of the glycogen-containing subline both below and above the transition temperature at 33 degrees C. 5. Polyacrylamide gel electrophoresis revealed different protein patterns mainly in the molecular weight range of around 90 000 and in the range between 31 000 and 14 000.

Isolation and characterization of plasma membranes from krebs II ascite cells using Percoll gradient

1. Plasma membranes were isolated from Krebs II ascite cells grown in the mouse. Cells were disrupted by nitrogen cavitation in an isotonic alkaline buffer containing magnesium and ATP. Isolation was performed in an alkaline-buffered self-generating gradient of Percoll with an angular rotor. At each step of the preparation, the pH appeared as the critical aspect of our procedure. 2. External membrane markers were concanavalin A and 5'-nucleotidase (EC 3.1.3.5). They reached a relative specific activity of 10, whereas this value was only of 0.7 for the endoplasmic reticulum marker, NADH dehydrogenase (EC 1.6.99.3). 3. Plasma membrane from 4 ml packed cells were isolated within 1 h after homogenization with good yield: 50% and 67% of total [3H]concanavalin A and 5'-nucleotidase, respectively, were recovered in the two plasma membrane fractions. 4. Electron microscopy examination showed the presence of vesicles of different sizes devoid of other structural contaminants. 5. Using the specific binding of concanavalin A to the external cell membrane, it was calculated that about 50% of the total cell phospholipid and 10% protein are located in the plasma membrane. Their sphingomyelin content is much higher than in the whole cell, in contrast to phosphatidylinositol, known as a more specific endoplasmic reticulum phospholipid.

Diet-induced changes in the fatty acid composition of mouse hepatocyte plasma membranes

Hepatocyte plasma membranes were isolated from the livers of mice fed either a low fat diet or high fat diets containing polyunsaturated or saturated fat. The combined rate and isopycnic ultracentrifugation technique which was used produced highly purified hepatocyte plasma membrane fractions. The efficacy of the procedure was checked by electron microscopy and the assay to marker enzymes for the different subcellular organelles. Mice were maintained on a low fat diet until 60-70 days of age, when they were fed high fat diets containing polyunsaturated fat. The hepatocyte plasma membrane lipids of mice fed the polyunsaturated fat diet for 4 wk contained increased proportions of the major dietary unsaturated fatty acid, linoleic acid, and increased proportions of arachidonic acid. The proportion of linoleic and arachidonic acids decreased with continued feeding of the polyunsaturated fat diet. The hepatocyte plasma membrane lipids of mice fed the saturated fat diet contained increased proportions of oleic acid.

The age-related occurrence of wax esters in the mouse preputial gland tumour

The mouse preputial gland tumour (ESR-586) accumulates wax esters from between 20 and 25 days after transplantation until they become the most abundant lipid class. Prior to this time wax esters are not detectable. The process occurs in both male and female host mice and appears to be determined by a response of the host to the tumour, rather than by a property of the tumour itself. The most abundant fatty alcohol present in the wax esters is hexadecanol. This contrasts with the greater proportions of the C20 to C24 chains found for the alkyl portion of the alkyldiacylglycerols, for which the precursors are fatty alcohols.