Breast cancer is associated with an increase in the activity and expression of cholinephosphotransferase in rats.

AIM: The present study aims to establish that cholinephosphotransferase (CPT), the terminal enzyme for the de novo biosynthesis of phosphatidylcholine (PC), can be used as a biomarker for breast cancer in an animal model. MAIN METHODS: Breast cancer was induced by intragastric administration of dimethylbenz(a)anthracene (DMBA) in rats. The activity and expression of CPT were compared between normal breast tissues and breast tumors. To establish possible mechanistic model, we looked into other enzymes of PC biosynthesis as well as c-fos protein expression and DNA binding. KEY FINDINGS: CPT enzyme activity and its expression were significantly higher in breast cancer tissues relative to normal breast tissues. Corresponding to the increase in the CPT activity and its expression, c-fos activity and its expression were also increased in breast tumors. SIGNIFICANCE: The present study suggests that increased CPT activity and expression is associated with DMBA-induced breast cancer development.

Identification of lutein, a dietary antioxidant carotenoid in guinea pig tissues.

Lutein, a dietary carotenoid, is a well known antioxidant. The major source of this carotenoid in humans is diet. We report here the presence of lutein, a dietary carotenoid in several guinea pig tissues (in decreasing order: liver>spleen>lung>>testis>kidney>plasma>eye but not in white adipose tissue). The presence of lutein in lung and other tissues may be significant in term of its antioxidant capacity of these organs.

Inhibition of cholinephosphotransferase activity in lung injury induced by 2-chloroethyl ethyl sulfide, a mustard analog.

Exposure to mustard gas causes inflammatory lung diseases including acute respiratory distress syndrome (ARDS). A defect in the lung surfactant system has been implicated as a cause of ARDS. A major component of lung surfactant is dipalmitoyl phosphatidylcholine (DPPC) and the major pathway for its synthesis is the cytidine diphosphocholine (CDP-choline) pathway. It is not known whether the ARDS induced by mustard gas is mediated by its direct effects on some of the enzymes in the CDP-choline pathway. In the present study we investigated whether mustard gas exposure modulates the activity of cholinephosphotransferase (CPT) the terminal enzyme by CDP-choline pathway. Adult guinea pigs were intratracheally infused with single doses of 2-chloroethyl ethyl sulfide (CEES) (0.5 mg/kg b.wt. in ethanol). Control animals were injected with vehicles only. The animals were sacrificed at different time and the lungs were removed after perfusion with physiological saline. CPT activity increased steadily up to 4 h and then decreased at 6 h and stabilized at 7 days in both mitochondria and microsomes. To determine the dose-dependent effect of CEES on CPT activity we varied the doses of CEES (0.5-6.0 mg/kg b.wt.) and sacrificed the animals at 1 h and 4 h. CPT activity showed a dose-dependent increase of up to 2.0 mg/kg b.wt. of CEES in both mitochondria and microsomes then decreased at 4.0 mg/kg b.wt. For further studies we used a fixed single dose of CEES (2.0 mg/kg b.wt.) and fixed exposure time (7 days). Lung injury was determined by measuring the leakage of iodinated-bovine serum albumin into lung tissue and expressed as the permeability index. CEES exposure (2.0 mg/kg b.wt. for 7 days) caused a significant decrease of both CPT gene expression (approximately 1.7-fold) and activity (approximately 1.5-fold) in the lung. This decrease in CPT activity was not associated with any mutation of the CPT gene. Previously we reported that CEES infusion increased the production of ceramides which are known to modulate PC synthesis. To determine whether ceramides affect microsomal CPT activity the lung microsomal fraction was incubated with different concentrations of C(2)-ceramide prior to CPT assay. CPT activity decreased significantly with increasing dose and time. The present study indicates that CEES causes lung injury and significantly decreases CPT gene expression and activity. This decrease in CPT activity was not associated with any mutation of the CPT gene is probably mediated by accumulation of ceramides. CEES induced ceramide accumulation may thus play an important role in the development of ARDS by modulating CPT enzyme.

Modulation of cholinephosphotransferase activity in breast cancer cell lines by Ro5-4864, a peripheral benzodiazepine receptor agonist.

Changes in phospholipid and fatty acid profile are hallmarks of cancer progression. Increase in peripheral benzodiazepine receptor expression has been implicated in breast cancer. The benzodiazepine, Ro5-4864, increases cell proliferation in some breast cancer cell lines. Biosynthesis of phosphatidylcholine (PC) has been identified as a marker for cells proliferating at high rates. Cholinephosphotransferase (CPT) is the terminal enzyme for the de novo biosynthesis of PC. We have addressed here whether Ro5-4864 facilitates some cancer causing mechanisms in breast cancer. We report that cell proliferation increases exponentially in aggressive breast cancer cell lines 11-9-1-4 and BT-549 when treated with nanomolar concentrations of Ro5-4864. This increase is seen within 24 h of treatment, consistent with the cell doubling time in these cells. Ro5-4864 also upregulates c-fos expression in breast cancer cell lines 11-9-1-4 and BT-549, while expression in non-tumorigenic cell line MCF-12A was either basal or slightly downregulated. We further examined the expression of the CPT gene in breast cancer (11-9-1-4, BT-549) and non-tumorigenic cell lines (MCF-12A, MCF-12F). We found that the CPT gene is overexpressed in breast cancer cell lines compared to the non-tumorigenic cell lines. Furthermore, the activity of CPT in forming PC is increased in the breast cancer cell lines cultured for 24 h. Additionally, we examined the CPT activity in the presence of nanomolar concentrations of Ro5-4864. Biosynthesis of PC was increased in breast cancer cell lines upon treatment. We therefore propose that Ro5-4864 facilitates PC formation, a process important in membrane biogenesis for proliferating cells.

Differential effect of cadmium on cholinephosphotransferase activity in normal and cancerous human mammary epithelial cell lines.

Cadmium (Cd) is an ubiquitous environmental carcinogen. Membrane phospholipids as well as fatty acid profile of membrane phospholipids are known to be altered in tumorigenicity and malignancy. Synthesis of cellular phosphatidylcholine (PC) has been used as a marker for membrane proliferation in the neoplastic mammary gland tissue. Cholinephosphotransferase (CPT), the terminal enzyme in de novo synthesis of PC, has an important role in regulating the acyl group of PC in mammalian cells. Our previous studies have shown that CPT is expressed differentially in the normal and cancerous mammary epithelial cell lines. In this study, we examined the effect of cadmium on CPT activity using normal (MCF-12A and MCF-12F) and cancerous (MCF-7, BT-549, and 11-9-1-4) human mammary epithelial cell lines. There was no consistent pattern of CPT activity in response to different doses of cadmium. The activity did not show a time-dependent variation at 5 micro M concentration, except in MCF-7 and 11-9-1-4. CPT gene expression increased with cadmium as evident from slot blots. Mutation in the nucleotide sequence was also observed as the result of cadmium but this did not result into amino acid sequence changes.